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IC 
 
 8948 
 
 Bureau of Mines Information Circular/1983 
 
 Back Injuries 
 
 Proceedings: Bureau of Mines Technology Transfer 
 Symposia, Pittsburgh, PA, August 9, 1983, 
 and Reno, NV, August 15, 1983 
 
 Compiled by James M. Peay 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
'p^ / h '' ^ t-h, . ^MMMi 'Y lt»^); 
 
 Information Circular 8948 
 
 Back Injuries 
 
 Proceedings: Bureau of Mines Technology Transfer 
 Symposia, Pittsburgh, PA, August 9, 1983, 
 and Reno, NV, August 15, 1983 
 
 Compiled by James M. Peay 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 James G. Watt, Secretary 
 
 BUREAU OF MINES 
 Robert C. Horton, Director 
 

 c\'0 
 
 %^ 
 
 ^1^ 
 
 This publication has been cataloged as follows: 
 
 Bureau of 
 
 Mines T 
 
 echnology Transfer 
 
 Sympos 
 
 ia (1983 : 
 
 Pittsburgh, PA, 
 
 and Reno, N 
 
 V) 
 
 
 
 
 Back inj 
 
 uries. 
 
 
 
 
 
 
 (Bureau 
 
 oi Mines in 
 
 ormation circu 
 
 ar ; 
 
 8948) 
 
 
 
 Includes 
 
 bibliograpl 
 
 ical references 
 
 . 
 
 
 
 
 Supt. of Docs, no.: 
 
 28.27:8948. 
 
 
 
 
 
 1. Mine accidents 
 Clongrcsscs. I. Peay, 
 circular (United States. 
 
 -Congresses. 2. 
 James M. 11. Tit 
 Bureau of Mines) ; 
 
 Back- 
 e. Ill 
 8948. 
 
 -Wounds 
 . Series: 
 
 and injuries- 
 Information 
 
 TN295.U4 
 
 fTNSll] 
 
 622s [622' 
 
 .8] 
 
 83-600258 
 
 
CONTENTS 
 
 Page 
 
 Abs tract 1 
 
 Introduction 2 
 
 Materials Handling Methods and Problems in Underground Coal Mines , by 
 
 Richard L. Unger and Daniel J. Connelly 3 
 
 Activities and Objects Most Commonly Associated With Underground Coal Miners' 
 
 Back Injuries, by Robert H. Peters 23 
 
 Analysis of Coal Mining Back Injury Statistics, by Terrence J. Stobbe and 
 
 Ralph W. Plummer 32 
 
 Two Back Risks in Mining: Lifting and Pushing and Pulling, by Robert 0. Andres 41 
 Field Testing of Workers Involved in Material Handling, by BCarl H. E. Kroemer.. 47 
 Lifting Capacity Determination, by M. M. Ayoub, J. L. Selan, W. Karwowski, and 
 
 H. P. R. Rao 54 
 
 Job Design for Manual Material Handling Tasks, by M. M. Ayoub, J. L. Selan, and 
 
 H. P. R. Rao 64 
 
 Back Injuries and Maintenance Material Handling in Low-Seam Coal Mines , by 
 
 Ernest J. Conway and William W. Elliott 74 
 
 Training Procedures to Reduce Low Back Injuries , by Nancy C. Selby 81 
 
 A Manual Materials Handling (MMH) Training Program for the Mining Industry, by 
 
 Daniel J. Connelly 88 
 
 Mechanization of Materials Handling Tasks , by Richard L. Unger 102 
 
BACK INJURIES 
 
 Proceedings: Bureau of Mines Technology Transfer Symposia, Pittsburgh, PA, 
 August 9, 1983, and Reno, NV, August 15, 1983 
 
 Compiled by James M, Peay 
 
 ABSTRACT 
 
 These proceedings consist of papers presented at two Bureau of Mines 
 Technology Transfer symposia on reducing back injuries in the mining in- 
 dustry. The sjnnposia were held in August 1983 and covered a wide range 
 of topics related to a more fundamental understanding of factors that 
 lead to back, injuries and approaches for reducing the frequency and 
 severity of such injuries. 
 
 'Supervisory engineering psychologist, Pittsburgh Research Center, Bureau of Mines, 
 Pittsburgh, PA. 
 
INTRODUCTION 
 
 Back injuries constitute the largest 
 single category of lost-time accidents in 
 the mining industry. U.S. Department of 
 Labor [Health and Safety Analysis Center 
 (HSAC)] data for 1981 indicates there 
 were 37,017 accidents in the mining in- 
 dustry of which approximately 25 pet or 
 roughly 9,254 incidents involved back in- 
 juries. Back injuries of the most severe 
 nature, i.e., strains, sprains, and dis- 
 located disks accounted for 5,458 inci- 
 dents or approximately 15 pet of all min- 
 ing injuries. 
 
 In addition, this category of injury 
 accounts for more lost workdays than any 
 other single type of injury. For exam- 
 ple, 40 pet of the lost-time back inju- 
 ries incurred by underground coal miners 
 during 1981 resulted in the miner missing 
 more than 4 weeks of work. When the num- 
 ber of lost workdays per back injury in- 
 cident is compared with other types of 
 mining injuries, statistics indicate that 
 on the average, those workers experi- 
 encing back injuries are off the job ap- 
 proximately 6 days longer. Thus, back 
 injuries not only constitute the single 
 largest category of mining injuries, but 
 also lead in degree of severity as re- 
 flected in lost workdays. 
 
 Back injuries, therefore, represent not 
 only a tremendous economic cost to coal 
 companies, to miners and their families, 
 and to society, they also represent a 
 tremendous amount of human suffering. 
 Data and expert optinion are in agreement 
 that intensified efforts and new ap- 
 proaches to reducing back injuries are 
 called for. 
 
 As pointed out by Robert H. Peters' 
 paper in these proceedings, there are 
 many good reasons to believe that the 
 
 mining environmental conditions and cur- 
 rent work procedures, which involve con- 
 siderable manual materials handling 
 tasks, pose relatively unique barriers to 
 preventing back injuries. Compared with 
 most other types of industrial settings, 
 many mines, especially underground opera- 
 tions, require considerable manual lift- 
 ing of heavy materials. Also, compared 
 with most other types of industrial set- 
 tings, many underground coal mines have 
 less than desirable illumination, are 
 wetter, and have constricted work spaces. 
 Illumination and water problems can re- 
 sult in back injuries caused by slipping 
 on wet or muddy surfaces or by tripping 
 over things that cannot be easily seen. 
 The thickness of many mineral seams also 
 prevents miners from performing work 
 while standing erect, forcing miners to 
 perform heavy work while in stooped or 
 kneeling positions, thus placing signifi- 
 cantly more stress on their backs than 
 other industrial workers who can perform 
 lifting activites while standing erect. 
 
 Training miners to cope with existing 
 work conditions has been the traditional 
 approach to reducing back injuries, how- 
 ever this method has many deficiencies, 
 as reflected in the continuing high fre- 
 quency and severity rates. While im- 
 proved training should be continued, 
 newly developed selection procedures and 
 extensive job redesign based on bio- 
 mechanical and ergonomic studies appear 
 to offer the greatest potential for fu- 
 ture positive impact. Many of the papers 
 contained in these proceedings, there- 
 fore, focus on assessment and selection 
 of workers who are most capable of per- 
 forming heavy lifting tasks and on analy- 
 sis and design of mining jobs to elimi- 
 nate many hazards that eventually lead to 
 back injuries. 
 
MATERIALS HANDLING METHODS AND PROBLEMS IN UNDERGROUND COAL MINES 
 By Richard L. Ungerl and Daniel J. Connelly2 
 
 ABSTRACT 
 
 Materials handling accidents are the 
 leading cause of nonfatal injuries in 
 underground coal mines in the United 
 States. The Bureau of Mines has spon- 
 sored research into the problems asso- 
 ciated with materials handling in 
 
 underground coal mines. This paper pro- 
 vides descriptions of the methods, exam- 
 ples of activities, flow paths of materi- 
 als, problem areas, and accident analyses 
 of materials handling operations reported 
 in Bureau of Mines research studies. 
 
 INTRODUCTION 
 
 Annually, materials handling is the 
 leading accident classification in under- 
 ground coal mines in the United States. 
 In 1980, materials handling accidents 
 accounted for 34% of the 15,075 nonfatal 
 days-lost accidents in underground coal 
 mines. 
 
 In order to identify the various fac- 
 tors that characterize the materials 
 handling problem, several analyses are 
 necessary. Bureau of Mines sponsored 
 
 research projects3 have provided a better 
 understanding of materials handling acci- 
 dents in underground coal mines. The 
 information reported in this paper is a 
 result of those research efforts. The 
 descriptions of materials handling meth- 
 ods, flow patterns, commonly handled ma- 
 terials, problems of mine environment and 
 personnel, and accident analyses that are 
 presented define the hazards associated 
 with materials handling in underground 
 coal mines. 
 
 BREAKDOWN OF THE OPERATING ENVIRONMENT 
 
 Manual handling of materials in an un- 
 derground coal mine can be described as 
 the performance of actions on items in 
 various operating environments. The 
 operating environments can be described 
 by the associated mine activities, loca- 
 tion, space limitations, and usage. A 
 practical division of the operating en- 
 vironments has been defined by handling 
 
 ^Civil engineer. 
 
 ^Safety specialist. 
 Both authors are 
 Pittsburgh Research 
 Mines, Pittsburgh, PA. 
 
 ■^Diaz, R. A., and A. 
 tem for Handling Supplies in Underground 
 Coal Mines ongoing BuMines contract 
 H0188049; for inf., contact G. R. Bock- 
 osh, TPO, Pittsburgh Res. Center, Pitts- 
 burgh, PA. 
 
 Foote, A. L. , and J. S. Schaefer. 
 Mine Materials Handling Vehicle (MMHV) 
 (contract H0242015 MBAssociates) . Bu- 
 Mines OFR 59-80, 1978', 308 pp.; NTIS PB 
 80-178890. 
 
 employed by the 
 Center, Bureau of 
 
 D. Chitaley. Sys- 
 
 functions which describe the general pur- 
 pose of the activities. 4 These handling 
 functions are 
 
 1. Production end use . 5 This function 
 relates to the handling of items during 
 their end use at the working face. Some 
 work activity examples are 
 
 Erecting temporary curtains for 
 ventilation. 
 
 Rock dusting. 
 
 Roof bolting. 
 
 Erecting roof timbers. 
 
 ^First work cited in footnote 3. 
 
 ^The end use handling associated with 
 section move, mine maintenance, and 
 equipment maintenance is included in the 
 respective functions. End use handling 
 associated with the production handling 
 function is classified as a separate 
 function. 
 
2. Production supply . This function 
 relates to the handling of materials from 
 the surface yard to locations near the 
 working face. It excludes the end use 
 handling. Work activities in this func- 
 tion are directly related to production. 
 Some examples of work activities are 
 
 Transporting rock-dust bags. 
 
 Transporting roof bolts. 
 
 Transporting timbers. 
 
 3. Section move. This function re- 
 lates to the handling of materials from 
 the surface yard to the section being 
 moved. It also includes the handling 
 during the process of moving a mining 
 section. Some examples of work activi- 
 ties are 
 
 Moving haulage belts. 
 
 Replenishing transformer oil, 
 hydraulic oil. 
 
 5. Mine maintenance. 
 
 This function 
 
 relates to handling of materials from the 
 surface yard to the point of end use 
 for mine maintenance. It also includes 
 final handling during scheduled and 
 unscheduled mine maintenance. Mine main- 
 tenance activities include the mainte- 
 nance of roof, floor, ventilation, path- 
 ways, rail track, and the like. It 
 excludes equipment maintenance activi- 
 ties, but includes those activities on 
 equipment which form part of the mine 
 installation. Some examples of work 
 activities are 
 
 Erecting stoppings for 
 ventilation. 
 
 Setting props and crossbars for 
 roof support. 
 
 Tearing up and re-laying rails. 
 
 Transporting cables. 
 
 Moving air lines, compressors. 
 
 Longwall face supports. 
 
 4. Equipment maintenance . This func- 
 tion relates to the handling of materials 
 from the surface yard to the point of 
 use. It also includes final handling ac- 
 tivities during maintenance of mine 
 equipment. Some examples of work activi- 
 ties are 
 
 Extracting motors from continuous 
 miners. 
 
 Replacing of extinguisher 
 canisters. 
 
 Laying rail. 
 
 Upgrading track. 
 
 Table 1 gives examples of materials 
 associated with various handling func- 
 tions for further understanding of the 
 work activities associated with each 
 function. Each of the handling functions 
 can be categorized by the type of ma- 
 terials handled, the usage frequency, 
 and the flow path. The flow path indi- 
 cates the path followed by the materi- 
 als in reaching the end use. The flow 
 paths and the typical materials moved in 
 each of the handling functions are de- 
 scribed in appendix A. The handling 
 functions will be used later to analyze 
 the accidents associated with materials 
 handling. 
 
TABLE 1. - Examples of materials handled in various handling functions l 
 
 Materials handled Handling functions ^ 
 
 Roof and rib support items: Roof bolts, roof Production end use, production supply 
 bolt plates, expansion heads, half headers, 
 timbers, steel beams, hydraulic jacks, crib 
 materials, cement, sand. 
 
 Fire protection items: Rock dust, extin- 
 guisher cannister, foam tank. 
 
 mine maintenance. 
 
 All handling functions. 
 
 Coal handling equipment items: 
 
 Belting, jacks, conveyor parts, rollers. Production end use, production sup- 
 stands. ply> equipment maintenance, section 
 
 move. 
 Shuttle cars, face equipment Equipment maintenance, section move. 
 
 Vehicle maintenance items: Tires, cans of 
 hydraulic oil, grease, and brake fluid, 
 motors, handtools and power tools, welding 
 equipment. 
 
 Air supply items: Air lines, compressors, 
 hoses, line fittings. 
 
 Water supply items: Hoses, pipes, pumps, 
 line fittings. 
 
 Production supply, equipment 
 maintenance. 
 
 All handling functions. 
 
 Production end use, production sup- 
 ply, section move, mine maintenance. 
 
 Ventilation items: Tubing, brattice, motors, All handling functions, 
 brackets, hardware. 
 
 Power supply items: Wire and cable spools, 
 motors, transformers, cans of transformer 
 oil, J hooks, motors, meters, power units, 
 trailing units, trailing cables and con- 
 nectors, breaker and switching panels. 
 
 Do. 
 
 Personnel support items: Food and water Production end use, production sup- 
 containers, toilets, first aid kits, ply» section move. 
 
 handtools. 
 
 'Based on classifications in a study of 27 mines reported in the second work of 
 footnote 3. 
 
 ^The end use handling associated with section move, mine maintenance, and equipment 
 maintenance is included in the respective functions. End use handling associated 
 with production handling function is classified as a separate function. 
 
CURRENT PRACTICES IN MATERIALS HANDLING OPERATIONS 
 
 Many methods exist for handling materi- 
 als among underground coal mines. More- 
 over, different methods may be used for 
 different materials within the same mine. 
 Each mine, however, seems to have an es- 
 tablished set of procedures for handling 
 production, mine maintenance and equip- 
 ment maintenance materials, and for ad- 
 vancing or retreating a section. 
 
 HANDLING OF PRODUCTION AND MINE 
 MAINTENANCE SUPPLIES 
 
 In terms of tasks and worker activi- 
 ties, production supply and mine mainte- 
 nance are closely related. For this rea- 
 son the discussion of these functions has 
 been combined. 
 
 Production and mine maintenance materi- 
 als are nearly always handled by a set of 
 routine procedures. A typical cycle of 
 events in this materials handling process 
 could include the following: 
 
 Transferring materials from commercial 
 carriers to a surface storage area, and 
 loading them on supply trips in their ex- 
 isting packaged form to be transported to 
 the section. 
 
 Breaking the bindings of materials in 
 packaged form and transferring individual 
 items or small bundles of items from the 
 supply trip to the section storage area. 
 
 Transferring the materials from the 
 section storage area to an area near the 
 working face. 
 
 Transporting the individual items for 
 their end use. 
 
 received roof bolts in packages of 10 
 with a number of packages strapped to a 
 pallet. 
 
 Forklifts, cherrypickers, front-end 
 loaders, and cranes are sometimes used to 
 help unload and stack the materials in 
 the surface storage area, but all mines 
 studied used some degree of manual hand- 
 ling at the surface. Some materials are 
 loaded in their packaged form, though it 
 is more common to have individual items 
 or small bundles loaded manually into the 
 vehicle for the trip into the mine. Some 
 mines perform bulk handling of rock dust 
 and oil. In these cases, the surface 
 yard will have bulk storage facilities 
 for these items after they have been re- 
 ceived from the supplier. Rock dust may 
 be pneumatically transferred into a rock- 
 dust bin from a truck or railroad car. 
 Hydraulic oil is pumped into a bulk tank, 
 or the mine may have an "oil house" where 
 it cleans, empties, and fills containers 
 to be transported to the section. 
 
 Typically, section supervisors will 
 generate lists of their supply needs. A 
 surface crew will take the list from each 
 section and assemble a supply trip. In 
 some mines, the supply function is a 
 scheduled effort that tries to anticipate 
 production and mine maintenance needs 
 rather than responding to demand. The 
 supply trip will deliver a scheduled 
 amount of supplies in accordance to the 
 linear advance expected from the section. 
 In large mines , it is common for the sup- 
 ply trips to be loaded on the first shift 
 and hauled into the mine on the third. 
 The supply logistics are less formal for 
 the smaller mines of one or two sections. 
 
 A general discussion of production 
 and mine maintenance handling methods 
 follows. 
 
 Handling on the Surface 
 
 Materials usually arrive at the mine 
 by truck or railroad. Most often they 
 are packaged on pallets or in strapped 
 bundles. It was noted that some mines 
 
 Transport to the Section 
 
 The methods of transporting supplies to 
 the section change with the items to be 
 handled. Solid supplies, such as roof 
 bolts, posts, blocks, and crossbars, are 
 transported as individual items or pal- 
 lets by means of mine cars or rubber- 
 tired vehicles. Large volume liquid and 
 granular supplies, such as rock dust. 
 
hydraulic oil, and water, are put into 
 containers and transported on vehicles or 
 handled in bulk. form. 
 
 There are several types of solid items 
 with different weights and sizes involved 
 in the production and mine maintenance 
 supply function. Table 2 outlines a typ- 
 ical list of items and average use per 
 day per section. 
 
 battery-powered vehicles, scoops, and/or 
 tractor-trailer combinations. 
 
 2. Rail haulage with a track laid in a 
 section heading as far as the tailpiece 
 using railcars pulled by a motor. 
 
 3. Rail haulage with track not extend- 
 ed into the section and transferring di- 
 rectly to battery-powered vehicles. 
 
 TABLE 2. - Description and usage 
 of typical supply items 
 
 Supply 
 
 Weight, 
 
 Av. 
 
 
 lb 
 
 use 
 
 2- to 12-foot plates, roof 
 
 
 
 bolts , and shells .......... 
 
 4- 12 
 50 
 
 123 
 
 Rock dust sacks............. 
 
 75 
 
 2- by 6-in to 6- by 8-in, 1- 
 
 
 to 16-ft lengths of timber. 
 
 
 
 boards, and headers 
 
 8-270 
 
 61 
 
 16- by 8- by 4- or 6-in 
 
 
 
 8 topping blocks 
 
 27- 65 
 
 52 
 
 8- to 13-ft header steel.... 
 
 10- 16 
 
 25 
 
 Bit: 
 
 
 
 Continuous miner. ......... 
 
 <1 
 <1 
 
 40 
 
 18 
 
 Roof drill 
 
 16 
 
 5— gal oil container. ........ 
 
 1 5 
 
 4- to 10-in diam, 3- to 15- 
 
 
 ft round timber posts 
 
 34-320 
 
 15 
 
 1- to 6-ft crib block 
 
 20- 60 
 
 12 
 
 Mortar mix sacks. ........... 
 
 90 
 60 
 
 3 
 
 75-ft brattice roll 
 
 <1 
 
 'Based on yearly supply 
 2 7 mines reported in the 
 footnote 3. 
 
 consumption of 
 second work of 
 
 A major difference in transport to the 
 section involves the use of area storage. 
 A few mines use intermediate storage lo- 
 cations, each of which serves several 
 working sections. This method requires a 
 transfer from the supply trip to stacks, 
 usually along the rib of the supply en- 
 try, and then another transfer to a vehi- 
 cle for haulage into the section. 
 
 Most mines transport directly from sur- 
 face storage to the section without an 
 intermediate storage area. There are 
 
 four methods of transport in conmion use 
 
 4. Rail haulage with track not extend- 
 ed to the section using rubber-tired or 
 railcars until the end of the track and 
 then converting to rubber-tired haulage 
 by battery-powered tractors. 
 
 5. Another method, though not in com- 
 mon use, is to reverse the conveyor belt 
 to handle materials; this requires manual 
 handling at the loading and unloading 
 point. 
 
 Many methods exist for handling bulk 
 materials, such as rock dust and hydraul- 
 ic oil. In the case of rock dust, the 
 need to handle bagged rock dust has been 
 practically eliminated by the use of one 
 of the following bulk transportation 
 methods: 
 
 1. Rock dust is pneumatically piped 
 into a rock-dust car at the section. In 
 smaller mines, it is piped directly to 
 the face. 
 
 2. Rock dust is fed by gravity through 
 a borehole or through a casing suspended 
 from an air shaft into a rock dust car 
 and then hauled to the section. 
 
 3. Rock dust is unloaded from a bin 
 into a rock dust car at the surface. 
 
 Two methods of handling bulk oil in- 
 clude having it flow by gravity from an 
 oil tank at the surface into an inter- 
 mediate storage area, or using 55-gal 
 drums transported by supply vehicle to 
 the section. 
 
 Handling in the Section 
 
 1. Rubber-tired haulage in drift mines 
 where the distance from surface to 
 section is short (less than 1 mile) using 
 
 Once the railcar or other supply vehi- 
 cle has arrived in the section two or 
 three crosscuts from the working face. 
 
items are usually unloaded and stacked. 
 In some mines, the vehicles are parked at 
 the section and the materials are used 
 directly. 
 
 If the supply vehicle is left in the 
 section, there is less handling of mate- 
 rials; however, mines vary in their will- 
 ingness to leave cars in the section for 
 two reasons. First, leaving the car 
 takes up room and makes switching diffi- 
 cult, and second, more supply cars are 
 required. 
 
 Haulage of supplies from section stor- 
 age to end use is accomplished several 
 ways 
 
 Manual carrying. 
 
 be found in section storage locations. 
 These locations vary from a small under- 
 ground shop with an overhead hoist to 
 storage stacks in a crosscut along a sup- 
 ply route. Some frequently used items 
 such as shuttle car wheels and hydraulic 
 hoses, can often be found in section 
 storage. 
 
 When a machine component is needed, it 
 is generally transported by the quickest 
 means possible to minimize downtime. 
 Problems are frequently encountered owing 
 to the weight of the item (sometimes over 
 2,000 lb). These materials are usually 
 handled with a combination of manual 
 handling and mechanical devices such as 
 a machine-mounted winch, come-along, or 
 jack. 
 
 Battery-powered vehicles such as 
 scoops, tractors, and personal 
 carriers. 
 
 Face equipment, such as roof bolters, 
 shuttle cars, and rock dusts. 
 
 When oil is transported in bulk to the 
 section, the usual procedure is to fill 
 5-gal containers and carry them to final 
 use. 
 
 HANDLING OF EQUIPMENT 
 MAINTENANCE MATERIALS 
 
 The handling of equipment maintenance 
 materials usually follows very undefined 
 paths. Some components are kept in sur- 
 face storage, but more likely they will 
 
 HANDLING OF SECTION MOVE SUPPLIES 
 
 The advance of the section calls for 
 the addition of conveyor sections, elec- 
 trical cable, and track, plus the trans- 
 port of equipment, such as a tailpiece, 
 belt feeder, or power boxes. While these 
 materials usually follow the conventional 
 supply route, their size and weight re- 
 quire special handling. This is accom- 
 plished using a combination of manual 
 handling and powered equipment. 
 
 For longwall sections, specially de- 
 signed lift-transporting devices have 
 been developed to handle roof supports 
 which present a problem owing to their 
 weight (10,000-lb range) and distances 
 they must be moved. 
 
 MINE ENVIRONMENT AND MATERIALS HANDLING METHODS 
 
 There are many environmental factors 
 that have an effect on a mine materials 
 handling method. These include 
 
 Mine size. 
 
 Portal; drift, slope, shaft. 
 
 Mining method; continuous, conven- 
 tional, longwall. 
 
 Coal haulage; belt, rail. 
 
 Seam height. 
 
 Stage of development; advance, 
 retreat, rooms. 
 
 The size of the mine plays a role in 
 determining the equipment available for 
 materials handling. Some mines are small 
 enough to use battery-powered scoops or 
 tractors to haul materials from the sur- 
 face to the section. Large mines are 
 more likely to use forklifts and cranes 
 
for surface handling because they have 
 higher utilization of such equipment. 
 
 The type of portal effects the diffi- 
 culty of transporting the materials into 
 and out of the mine. Transportation into 
 a drift mine is usually the easiest since 
 a locomotive can often run in and out of 
 the mine. At slope mines, it is common 
 practice to lower the supply trip into 
 the mine using a hoist. The shaft mine 
 poses the most problems since a train of 
 cars cannot be transported into the mine. 
 In some cases, they can be lowered one 
 car at a time by hoist; or where cars 
 cannot be hoisted, materials must be 
 doubly handled. 
 
 The mining method has the largest ef- 
 fect on the types of materials that are 
 handled. Conventional mining involves 
 essentially the same materials handling 
 methods as continuous mining except for 
 the special requirements for handling ex- 
 plosives. However, longwall mining has 
 radically different requirements. Mate- 
 rials, such as roof bolts, rock dust, and 
 stopping blocks, are used only on a lim- 
 ited basis for development. The descrip- 
 tion for handling equipment maintenance 
 materials and section move could serve as 
 the general pattern for longwall sec- 
 tions, except that in longwall mining the 
 section move is a massive operation. 
 
 The method of coal haulage does not 
 appear to have a large impact on handling 
 methods because track is generally laid 
 
 for personnel and supply movement even in 
 mines with belt haulage. Probably the 
 largest factor influencing the movement 
 of materials is the scheduling problems 
 encountered between supply trips and coal 
 haulage on the main line track 
 
 Seam height has a large impact from 
 several aspects. A high-seam mine opera- 
 tion is better able to lay track up to a 
 section because it is not faced with the 
 costs of cutting roof or bottom to pro- 
 vide height clearance. In low mines, 
 problems are encountered when loading 
 supplies in and out of supply cars be- 
 cause of limited clearance between the 
 sides of the car and the roof. This same 
 problem makes it impossible to use avail- 
 able overhead lifting devices. Another 
 problem results because manual lifting 
 and carrying must be done while bending 
 over, which is extremely strenuous to the 
 back. 
 
 The stage of mine development has an 
 impact mainly on the materials used. 
 Material usage changes significantly 
 between advance and retreat mining. For 
 instance, in retreat mining, more timber 
 is used and new stoppings will not be 
 erected. The major problem with retreat 
 mining is associated with recovery of 
 materials. As the section retreats, 
 materials such as conveyor sections, 
 track, water pipe and electrical cable, 
 must be pulled out of the section and 
 stored. 
 
 PROBLEM AREAS IN THE PRESENT MATERIALS HANDLING SYSTEMS 
 IN UNDERGROUND COAL MINES 
 
 Interviews with mine operators and 
 equipment manufacturers have indicated a 
 general awareness of materials handling 
 problem areas such as accidents, supply 
 function, labor costs, and production de- 
 lays due to maintenance and production 
 supply system breakdowns. 6 The produc- 
 tion materials handling function supports 
 most other activities in the mine and is 
 affected by its interaction with other 
 operations. Daily supply items such as 
 roof bolts, timber bolts, and concrete 
 
 "First work cited in footnote 3. 
 
 blocks, are needed at various locations 
 at different times. The movement of mine 
 maintenance and equipment maintenance 
 materials, such as replacement motors, 
 are vital to keeping production going. 
 Section move, though not as common an oc- 
 currence, poses special hazards owing to 
 the size and weight of the items being 
 handled. 
 
 Meeting these needs requires the 
 movement and handling of materials by 
 most mine personnel. Their activities 
 are based on the quantities of items 
 
10 
 
 required, times when they are needed, 
 physical characteristics of the items, 
 transfers between transport equipment and 
 storage, availability of transport and 
 other handling equipment, communications 
 systems among the supply personnel, in- 
 formation exchange between the supply 
 personnel and other miners, and the pre- 
 dictability of supply needs at various 
 locations underground. The following 
 sections discuss problems related to the 
 above factors. 
 
 PERFORMANCE OF HAZARDOUS 
 MANUAL ACTIONS 
 
 Manual handling of items is very common 
 in underground coal mines. Typically, 
 materials are loaded and unloaded from 
 vehicles, placed in storage, carried, or 
 simply held unsupported. Such manual 
 handling occurs in support of mine opera- 
 tions such as production, mine mainte- 
 nance, equipment maintenance, and section 
 move. Manual actions directly associ- 
 ated with accidents can be grouped as 
 follows: 
 
 Stationary actions (transfer) 
 
 Lifting or lowering without support 
 (supply item is supported manually). 
 
 Pushing or pulling with support (sup- 
 ply item is on floor or surface of a 
 vehicle) . 
 
 Holding without support (supply item 
 is held manually). 
 
 Walking actions (transport) 
 
 Carrying without support (supply item 
 is held manually). 
 
 Pushing or pulling with support (sup- 
 ply item is on floor, skid, or on surface 
 of a vehicle). 
 
 End use actions 
 
 All actions connected with the final 
 application of supply items and not sep- 
 arately classified as stationary or walk- 
 ing actions. 
 
 ACCIDENT ANALYSIS OF HANDLING 
 FUNCTIONS AND ACTIONS 
 
 Accident data used were obtained in 
 a study of 27 mines representative of 
 the coal mining industry profile. 7 These 
 data were taken from mine accident rec- 
 ords for 1973. 
 
 In the 27 mines sampled, a total of 269 
 materials handling accidents took place. 
 A total of 771 days were lost because of 
 these accidents. The total hours worked 
 were 10.356 million and total coal pro- 
 duction was 15.121 million tons. Acci- 
 dent data were analyzed for the handling 
 functions and actions defined earlier. 
 Accident frequencies, days lost, and 
 severity were calculated for various 
 handling functions and actions and are 
 presented in appendix B.8 The following 
 paragraphs highlight the findings of this 
 analysis. 
 
 The reported accident data were ana- 
 lyzed for frequency and severity with 
 reference to manual actions and han- 
 dling functions. The following signifi- 
 cant observations resulted from the 
 analysis: 
 
 The production supply and mine mainte- 
 nance functions are highly hazardous sup- 
 ply environments. 
 
 They account for 
 accidents. 
 
 60% 
 
 of the 
 
 They account for 76% of the days 
 lost. 
 
 Accident severity (6.26) is the high- 
 est in the mine maintenance function. 
 
 Accident severity (3.25) is also high 
 in the production supply function. 
 
 Stationary manual actions in the pro- 
 duction supply and mine maintenance func- 
 tions are the largest contributors to the 
 total accidents. 
 
 8 
 
 Second work cited in footnote 3. 
 
 See appendix B for definitions of fre- 
 
 quency, days lost, and severity. 
 
11 
 
 Lifting and lowering without support is 
 a highly hazardous manual action in ma- 
 terials handling. It accounts for 59% of 
 all accidents and 54% of days lost. 
 
 Manual carrying without support is a 
 hazardous action with high accident se- 
 verity (4.11). 
 
 INEFFICIENT UTILIZATION 
 OF SUPPLY LABOR 
 
 In general, supply-related personnel 
 are underutilized in that their produc- 
 tive time is less than half of the work- 
 ing shift. Considerable time is spent in 
 traveling to and from work, areas, wait- 
 ing, returning empties, and the like. In 
 some mines, a large fraction of the time 
 is lost owing to early quitting, late 
 starting, and traffic conflicts. Some 
 identifiable factors related to this 
 problem include 
 
 Performance standards have not been 
 developed, therefore, staffing and sched- 
 uling or performance control is based al- 
 most entirely on experience and guess- 
 work. 
 
 Staffing of the supply function is 
 based on past history, experience, and 
 anticipation of peak loads, which results 
 in overstaf f ing. 
 
 For some items the usage quantity, 
 place, and time are predetermined. Yet a 
 large number enter the mine on an as- and 
 when-needed basis. The lag time between 
 a supply requisition by the section or 
 mine supervisor from the surface yard and 
 the actual delivery of the item encour- 
 ages the supervisor to overstock supplies 
 in advance. Very few supply scheduling 
 plans exist. 
 
 In general, predetermined routing of 
 items to the working section does not ex- 
 ist and is rarely followed when it does. 
 This creates hazards and makes supervi- 
 sion difficult. 
 
 Communications between personnel han- 
 dling material is difficult because of 
 noise and poor visibility. 
 
 Good information exchange between the 
 section and mine supervisor and the sup- 
 ply crew do not normally exist. 
 
 PERSONNEL PROBLEMS 
 
 Several personnel problems were iden- 
 tified as reducing the efficiency of 
 materials handling operations, as well as 
 increasing the possibility of an injury 
 in the performance of manual handling 
 tasks. 
 
 Job bidding in union mines gives the 
 workers an opportunity for higher wages 
 and job advancement. This generally re- 
 sults in junior, more inexperienced per- 
 sonnel staffing the supply function or 
 doing other manual labor. 
 
 Stretching physical limits and capabil- 
 ities in manual handling of materials 
 often result in injuries to personnel 
 with inadequate physical capability in an 
 effort to meet job requirements. 
 
 Very little formal safety training is 
 obtained by supply personnel because most 
 of the training is "on the job." Also, 
 there is little training given on tech- 
 niques for manual handling of materials 
 in an underground environment. 
 
 WEIGHT OF SUPPLY ITEMS 
 
 Table 2 outlines the size and weight 
 ranges and average daily section usage of 
 some common supply items. Many supply 
 items such as rails, timber, headers, 
 stopping blocks, crib blocks, bags of 
 rock dust or mortar mix, and the like, 
 are of considerable weight. The manual 
 handling of such supply items in a low 
 roof, poor footing environment increases 
 the probability of accidents and handling 
 time, even though they are usually 
 handled by more than one person per item. 
 In general, very few attempts have been 
 made at weight reduction of supply items. 
 A known exception is the recent use of 
 fiberglass beams by some mines. These 
 beams are considerably lighter than 
 timber. 
 
12 
 
 Figures B-5 and B-6 of appendix B give 
 frequencies and severities for accidents 
 occurring while handling supply items of 
 various weight groups. The accident data 
 indicate the following: 
 
 Most of the accidents occur while han- 
 dling supply items in the 1- to 100-lb 
 weight group. 
 
 Typical supply items in this weight 
 group are roof bolts, short timber, 5-gal 
 oil containers, rock dust or mortar mix 
 bags, belts, and stopping block. 
 
 The 1- to 100-lb weight group accounts 
 for the majority of days lost. 
 
 Accident severity is very high for 
 the 200- to 500-lb weight groups taken 
 together. 
 
 Typical supply items in this weight 
 group are electric motors, equipment com- 
 ponents, haulage rails, PVC and steel 
 pipes, pumps, timber, and large oil 
 drums. 
 
 HAZARDOUS ENVIRONMENTAL CONDITIONS 
 
 The underground mine environment is 
 considerably more hazardous and difficult 
 to work in as coii^)ared to most surface 
 environments. Such conditions not only 
 increase the probabilities of accidents, 
 but also reduce the rate of manual work. 
 Some examples of hazardous handling oper- 
 ations due to the environment are as 
 follows: 
 
 Bending or Sitting on folded legs is 
 common in mlp.es of low roof height. 
 Holding without support, lifting, or car- 
 rying weight under such conditions can 
 result in back injuries. This cumbersome 
 position causes worker fatigue and 
 increases the potential for dropping 
 loads. 
 
 Poor maintenance of the mine bottom re- 
 sults in slippery and uneven footing. 
 Manual handling actions performed under 
 such conditions increase the potential 
 for accidents. 
 
 SUMMARY 
 
 Materials handling accidents have been 
 identified as a significant problem area 
 in underground coal mines. Bureau of 
 Mines research has provided a better un- 
 derstanding of the numerous factors con- 
 tributing to materials handling problems. 
 
 In this paper, descriptions and exam- 
 ples of current materials handling meth- 
 ods and problems in underground coal 
 mines have been presented, as reported in 
 Bureau of Mines research studies. Mate- 
 rials handling activities have been de- 
 fined by the various mining operations 
 which describe their general purpose. 
 These materials handling functions are: 
 Production End Use, Production Supply, 
 Section Move, Equipment Maintenance, and 
 Mine Maintenance. 
 
 A survey of a representative sample of 
 underground coal mines^ has resulted in 
 a description of the methods, practices, 
 flow paths, and items typical of materi- 
 als handling activities. In addition, 
 several specific problem areas associ- 
 ated with materials handling in under- 
 ground coal mines , such as manual hand- 
 ling actions accidents, inefficient use 
 of labor, and hazardous environmental 
 conditions, have been discussed. In sum- 
 mary, this paper has provided an over- 
 view of the methods and problems of ma- 
 terials handling in underground coal 
 mines. 
 
 ^Second work cited in footnote 3. 
 
13 
 
 APPENDIX A.— FLOW PATHS AND MATERIALS FOR VARIOUS MATERIALS HANDLING FUNCTIONS 
 
 Figures A-1 through A-5 illustrate flow each figure. The flow paths also show 
 
 paths of materials in various operating locations at which manual transfer, 
 
 environments defined by the handling transport, and end use actions are per- 
 
 f unctions. Only the major items of the formed on the materials, 
 handling function have been listed in 
 
14 
 
 APPENDIX B. —ACCIDENT ANALYSIS 
 
 Accident data collected in a study of 
 27 mines has been analyzed in this ap- 
 pendix. Accident frequencies, severity, 
 and days lost have been calculated for 
 various handling functions, manual haz- 
 ardous actions, and weight groups of 
 items. Figures B-1 through B-6 illus- 
 trate the results of these analyses. In 
 the following sections, accidents are 
 further discussed in terms of various 
 handling functions. Some definitions 
 used in these discussions include: 
 
 Frequency — The number of accidents for 
 a particular handling function. 
 
 Severity — Frequency divided by the num- 
 ber of days lost for a particular hand- 
 ling function. 
 
 Days lost — Actual days lost from work. 
 
 PRODUCTION SUPPLY AND MINE 
 MAINTENANCE FUNCTIONS 
 
 of the accidents in this handling func- 
 tion. (Refer to table B-1.) 
 
 Stationary actions account for 77% of 
 the accidents in this function, while 
 walking actions relate to 23%. 
 
 Cable handling poses a handling problem 
 different from the other materials used 
 in this function. At intersections, the 
 cable has to be lifted and hung from a 
 hook anchored to a roof bolt. It also 
 has to be pulled in advance of tramming 
 equipment to prevent damage by tramming 
 over the cable. The production end use 
 function accounts for 30% (out of 269) 
 accidents, but only 5% of the total 771 
 days lost. The accident severity is con- 
 siderably lower than other functions, 
 1.17 days lost per accident, 
 
 TABLE B-1. - Number of accidents 
 classified by manual actions in 
 the production end use function 
 
 Since most of the materials used and 
 manual actions are similar for these 
 functions and since their activities are 
 closely related, the accident data for 
 these two functions have been combined. 
 
 Sixty percent (160 out of 269) of all 
 manual handling accidents take place in 
 the production supply and mine mainte- 
 nance functions. The number of days lost 
 owing to accidents in these two functions 
 together account for 76% (588 out of 771 
 days lost). The severity of accidents in 
 the mine maintenance function is the 
 highest, 6.26 days lost per accident. 
 The severity in the production supply 
 function is also high, 3.15 days lost per 
 accident. 
 
 
 Weight, 
 lb 
 
 Accidents 
 
 Item 
 
 Sta- 
 
 Walk- 
 
 
 
 tionary 
 
 ing 
 
 6- by 6-in by 5- 
 
 
 
 
 to 8-ft (closed) 
 
 
 
 
 roof jack 
 
 50- 70 
 
 3 
 
 4 
 
 6- by 8-in by 10- 
 
 
 
 
 to 14-ft crossbar 
 
 160-225 
 
 5 
 
 
 
 6-in-diam by 5- to 
 
 
 
 
 8-ft round posts. 
 
 48- 76 
 
 3 
 
 2 
 
 2- to 3-in-diam 
 
 
 
 
 trailing cable... 
 
 15- 10 
 
 4 
 
 
 
 Other items 
 
 NAp 
 
 8 
 
 1 
 
 Total 
 
 NAp 
 
 23 
 
 7 
 
 NAp Not applicable. 
 1Per foot. 
 
 SECTION MOVE FUNCTION 
 
 Most of the accidents in these func- 
 tions are related to stationary actions 
 (38% of 269). Walking actions account 
 for the next largest number of accidents 
 in these functions (18% of 269). 
 
 PRODUCTION END USE FUNCTION 
 
 Roof jacks, crossbars, round posts, and 
 trailing cables account for the majority 
 
 A major move of a production unit from 
 one section to another is infrequent, oc- 
 curring from one to three times per year. 
 Most of the handling actions and materi- 
 als are similar to other functions. A 
 number of manual handling actions are in- 
 volved during the section move operation. 
 Handling of rail, belt, and belt rollers 
 cause the majority of accidents in this 
 function (table B-2). In some mines. 
 
15 
 
 TABLE B-2. - Number of accidents classified by manual actions for some materials 
 in the section move function 
 
 Item 
 
 Common usage 
 
 Weight, 
 lb 
 
 Accidents 
 
 
 Stationary 
 
 Walking 
 
 40- to 85-lb rail, 20- to 39- 
 
 ft length. 
 Belt roller, 4-in-diam by 36- 
 
 in length to 6-in-diam by 
 
 42-in length. 
 Belt, 36- and 42-in width.... 
 Rail tie, 8 by 6 by 72 in.... 
 Belt chain, 8 by 9 by 52 in. . 
 
 Coal, supply haulage.. 
 Return (bottom) idler. 
 
 Coal haulage 
 
 Support for rail 
 
 Carrying (top) idler.. 
 
 266-1,100 
 40- 50 
 
 NA 
 90- 100 
 20- 25 
 
 9 
 
 4 
 
 4 
 1 
 
 1 
 
 6 
 1 
 
 
 1 
 
 
 
 Total 
 
 NAp 
 
 NAp 
 
 19 
 
 8 
 
 NA Not available. NAp Not applicable. 
 
 rails are manually rolled off a supply 
 car and then manually dragged into place, 
 which is a hazardous practice. In other 
 mines, the rail is attached by a chain to 
 a scoop, battery tractor, or the like, 
 and is pulled out of the supply car and 
 then pulled into place by the transport 
 vehicle. This handling practice, too, is 
 considered hazardous. 
 
 Section move accounts for 13% (out of 
 269) accidents, with 7% (out of 771) days 
 lost. 
 
 EQUIPMENT MAINTENANCE FUNCTION 
 
 This function accounts for the next 
 largest number of accidents, 16% (out of 
 269) and days lost, 12% (out of 771), as 
 compared with production supply and mine 
 maintenance functions. Stationary ac- 
 tions performed during removal and re- 
 placement of heavy equipment parts, such 
 as motors, rubber tires on haulage vehi- 
 cles, and the like, account for most of 
 the accidents in this function. 
 
 Most of the items in this function are 
 in the 50- to 200-lb range and are usu- 
 ally handled by one to four miners. 
 
 Another major source of accidents is the 
 manual handling of 5-gal cans of hydraul- 
 ic oil, tool boxes, and welding gas bot- 
 tles. Generally, tool boxes weigh up to 
 100 lb and require two miners to lift or 
 carry them. 
 
 Table B-3 gives the accident frequen- 
 cies for various materials and hazardous 
 manual actions for the equipment mainte- 
 nance function. 
 
 TABLE B-3. - Number of accidents classi- 
 fied by manual actions for some mate- 
 rials in the equipment maintenance 
 function 
 
 
 Accidents 
 
 
 Sta- 
 tionary 
 
 Walk- 
 ing 
 
 Face equipment components. 
 
 Repair supplies (oil cans, 
 wire reels, etc.) 
 
 Repair supplies (tool- 
 boxes, gas bottles 
 
 Shuttle car components.... 
 
 Other equipment components 
 
 Belt conveyor components.. 
 
 7 
 
 5 
 
 5 
 7 
 7 
 4 
 
 2 
 
 4 
 
 3 
 
 
 
 
 Total. 
 
 35 
 
 9 
 
16 
 
 Surface 
 storage 
 
 
 Belt 
 Belt entry move up 
 
 KX 
 
 Track entry 
 
 Track move up 
 
 Area 
 storage Section storage 
 
 DOO 
 
 Production working place 
 
 KEY 
 
 D 
 
 Manual 
 transfer 
 
 O 
 
 Manual 
 transport 
 
 O 
 
 End use 
 handling 
 
 Major materials ranked by usage frequency 
 •Roof bolts, plates, and shells . Bits -continuous miner 
 
 • Wedges . Bits- roof drill 
 
 • Rock dust sacks • Timber- round posts 
 
 • Timber- boards and headers . Crib block 
 
 • Header, steel . Brattice cloth 
 
 FIGURE A-l. - Production supply function flow path with materials used. 
 
17 
 
 Surface 
 storage 
 
 Belt 
 Belt entry move up 
 
 K>0 
 
 Track entry 
 
 Track move up 
 
 Area 
 
 DO-O 
 
 storage Section storage Production working place 
 
 DtCIOOO 
 
 o 
 
 Equipment 
 maintenance 
 
 J^ 
 
 KEY 
 
 D 
 
 Manual 
 transfer 
 
 o 
 
 Manual 
 transport 
 
 O 
 
 End use 
 handling 
 
 Major materials ranked by usage frequency 
 
 • Wedges 
 
 • Rock dust sack 
 
 • Timber - boards and headers 
 
 • Stopping blocks 
 
 • Timber-round posts 
 •Crib block 
 
 • Mortar mix sack 
 
 • Pipe-PVC and steel 
 
 FIGURE A-2. - Mine maintenance function flow path with materials used. 
 
18 
 
 Belt 
 Belt entry move up 
 
 Surface 
 storage 
 
 o 
 
 KH 
 
 Track entry 
 
 Track move up 
 
 Area 
 storage Section storage 
 
 Production working place 
 
 KXTD 
 
 O 
 
 Equipment 
 maintenance 
 
 KEY 
 
 D 
 
 Manual 
 transfer 
 
 o 
 
 Manual 
 transport 
 
 O 
 
 End use 
 handling 
 
 Major materials ranked by usage frequency 
 
 • Roof jack, portable 
 
 • Trailing cable 
 
 • Wire 
 
 FIGURE A-3. - Production end use function flow path with materials used. 
 
19 
 
 Surface 
 storage 
 
 Belt 
 Belt entry move up 
 
 hO< 
 
 Track entry 
 
 "-"''^-^'"'^' 
 
 Track move up 
 
 Area 
 storage Section storage Production working place 
 
 brK>^3 
 
 Equipment 
 maintenance 
 
 
 fS^Jf^^lw^^ 
 
 Xh-'X^ii&fi'.-.-i 
 
 KEY 
 
 D 
 
 Manual 
 transfer 
 
 O 
 
 Manual 
 transport 
 
 O 
 
 End use 
 handling 
 
 Major materials ranked by usage frequency 
 
 • Lubricant containers 
 
 • Equipment components 
 
 • Bottles, welding gas 
 
 • Tool boxes 
 
 FIGURE A-4. - Equipment maintenance function flow path with materials used. 
 
20 
 
 Surface 
 storage 
 
 JJW^V*-'!.-:'^;'.' 
 
 ?A;-?-..''r ^'i'via 
 
 Belt 
 Belt entry move up 
 
 Area 
 
 storage Section storage Production working place 
 
 Equipment 
 maintenance 
 
 KEY 
 
 D 
 
 Manual 
 transfer 
 
 o 
 
 Manual 
 transport 
 
 O 
 
 End use 
 handling 
 
 Major materials ranked by usage frequency 
 •Conveyor belt 'Belt support stand 
 
 • Carrying idlers • Haulage roil 
 
 • Return idler 'Timber 
 
 FIGURE A-5. - Section move function flow path with materials used. 
 
21 
 
 140 
 130 
 120 
 110 
 100 
 
 CO 
 
 z 90 
 
 UJ 
 
 o 
 
 o 80 
 
 (J 
 
 < 
 
 li. 70 
 
 133 (50%) 
 
 Total number of accidents = 269 
 
 44 { 16%) 
 
 27(10%) 
 
 30(11%) 
 
 n 
 
 35 (13%)- 
 
 
 i>-? 
 X-> 
 ^^V 
 
 
 FIGURE B-1, - Accident frequencies for different 
 handling functions. 
 
 6.^6 
 
 (169) 
 
 
 7 
 
 
 
 t 
 
 KEY 
 
 
 Totol number of accidents ■ 269 
 
 
 Total average seventy- 2.87 
 
 
 Total days lost "771 
 
 - 
 
 Figures in ( ) ore days lost 
 
 
 / 
 
 
 
 / 
 
 
 _ 
 
 / 
 
 _ 
 
 J./ 5 
 
 ^ 
 
 
 (419) 
 
 
 
 ' 
 
 
 s 
 
 
 - 
 
 
 
 2.07 
 
 (91) 
 
 7\ 
 
 1.17 / 
 
 (35) ^ . 
 
 71 ^ 
 
 1.63 
 (57 
 
 1 
 
 
 
 ^ 
 
 
 
 / 
 
 
 / 
 
 
 
 
 
 
 ^ 
 
 
 / 
 
 
 / 
 
 
 
 / 
 
 
 / 
 
 
 
 / 
 
 
 / 
 
 
 
 
 6</ 
 
 
 ^.^ 
 
 FIGURE B-2, - Accident severity for various han- 
 dl ing functions. 
 
 180 
 
 ISO 
 
 I 40 
 
 120 
 
 100 
 
 80 
 
 60 
 
 40 
 
 20 
 
 :p^ 
 
 Lifting or lowering 
 
 without support 
 
 158 (59%) 
 
 \X>th 
 
 Total nunnber of accidents = 269 
 
 Carrying 
 
 without support 
 
 56(21%) 
 
 Holding 
 
 without support 
 
 1 1 (4%) 
 
 Pushing or 
 pulling 
 with support 
 9 (3%) 
 
 Stationary 
 ( transfer) 
 178 (66%) 
 
 A 
 
 Pushing or pulling 
 
 with support 
 
 17 (6%) 
 
 End use action 
 in all modes 
 18 (7%) I 
 
 A. 
 
 Walking 
 (transport) 
 73 (27%) 
 
 All end use 
 18 (7%) 
 
 FIGURE B-3. - Accident frequencies for differ- 
 ent hazardous manual actions. 
 
 Stationary 
 
 (transfer) 
 
 (484) 2.61 
 
 Walking 
 (transport) 
 (264) 3.62 
 
 All end use 
 (43) 2.39 
 
 FIGURE B-4, - Accident severity for various man- 
 ual hazardous actions. 
 
22 
 
 
 q: 
 lij 
 > 
 
 LiJ 
 
 LU 
 O 
 
 O 
 O 
 < 
 
 5.4 
 
 (156) 
 
 F 
 
 S.2 
 
 (273) 
 
 F 
 
 (256) 
 
 .es 
 
 (17) 
 
 /I M 
 
 KEY 
 Total days lost = 771 
 Total accidents=269 
 Severity = 2.9 days lost 
 per accident 
 Figures in ( ) = total doys 
 lost 
 
 3.4 
 
 (41) 
 
 17 
 
 2.6 
 
 (21) 
 
 A 
 
 .A 
 
 .68 
 
 (7) 
 F 
 
 (0) (0) 
 
 ^.^-/^o%o^o%o%^o o- o- 
 
 MATERIAL WEIGHT GROUPS, lb 
 
 FIGURE B-5. - Accident frequencies for various 
 manual handling accidents in materials weight 
 groups. 
 
 
 1 10 
 
 
 100 
 
 
 90 
 
 
 80 
 
 Z 
 
 
 liJ 
 
 a 
 
 70 
 
 () 
 
 
 o 
 
 ttO 
 
 < 
 
 
 u. 
 o 
 
 50 
 
 tr 
 
 
 LJ 
 
 40 
 
 m 
 
 
 - 86 
 F 
 
 30 
 20 
 10 
 
 97 
 
 The weight group is only an 
 
 indication of the physical 
 
 characteristics of the materials. 
 
 It should not be confused with the 
 
 desirable load capacity of any 
 
 potential equipment. 
 
 20 
 
 12 
 
 \V\\A^,^\7\ 
 
 ^ r> C^ o>' r>' o> ^\' 
 
 v°^ ^°^ >,Q^ 
 
 ^Q ^ 
 
 ^ ^^ 
 
 MATERIAL WEIGHT GROUPS, lb 
 
 FIGURE B-6. - Accident severity for manual han- 
 dling accidents in various materials weight groups. 
 
23 
 
 ACTIVITIES AND OBJECTS MOST COMMONLY ASSOCIATED WITH UNDERGROUND 
 COAL MINERS' BACK INJURIES 
 
 By Robert H. Peters 1 
 
 ABSTRACT 
 
 Recent national statistics on factors 
 associated with underground coal miners' 
 back injuries are presented. Particular 
 attention is given to describing combin- 
 ations of events and conditions that 
 account for over 1 pet of these back, in- 
 juries. Most of the statistics present- 
 ed in this paper are derived from Mine 
 
 Safety and Health Administration's (MSHA) 
 records of injury data and short narra- 
 tive accounts of injuries. It is con- 
 cluded that since there are such a vari- 
 ety of factors that contribute to back 
 injuries, significant improvements can 
 be realized only through a broad, multi- 
 faceted approach to prevention. 
 
 INTRODUCTION 
 
 There is reason to believe that the en- 
 vironmental conditions that exist in many 
 underground coal mines pose relatively 
 unique barriers to the prevention of back 
 injuries. Compared with most other types 
 of industrial settings, many underground 
 coal mines are not as well illuminated, 
 are wetter, and have more restricted work 
 spaces. The problems of illumination and 
 water can result in back injuries caused 
 by slipping on wet or muddy surfaces or 
 tripping over things that could not be 
 seen clearly. Coal seams that prevent 
 miners from standing erect contribute to 
 the occurrence of back injuries because 
 miners who must stand, walk, lift, and 
 carry things in a stooped position place 
 significantly more stress on their backs 
 than those who can perform these activi- 
 ties while standing erect. 
 
 Back injuries are unquestionably the 
 most common type of injury suffered by 
 miners. A few statistics based on injury 
 data reported to MSHA help to portray the 
 significance of the problem. 
 
 Table 1 presents the total reported in- 
 juries and overall incidence rates and 
 severity measures associated with back 
 injuries suffered by U.S. coal miners 
 while working underground for each year 
 
 ^Research psychologist, Pittsburgh Re- 
 search Center, Bureau of Mines, Pitts- 
 burgh, PA. 
 
 from 1978 to 1981. No trends are appar- 
 ent in the figures for total injuries and 
 incidence rates. The total number of re- 
 ported back injuries over this 4-yr peri- 
 od range from 2,654 to 3,779, and do not 
 appear to be declining. The overall in- 
 cidence rates over this 4-yr period range 
 from 2.74 to 3.39, and also do not appear 
 to be declining. The overall severity 
 rates over this 4-yr period range from 
 102 to 141, and definitely portray a 
 trend of increasing severity. 
 
 It should be noted that not all back 
 injuries (especially the "minor" ones) 
 are reported to MSHA. Therefore, it is 
 very likely that, in reality, the numbers 
 and incidence rates associated with back 
 injuries are higher than those portrayed 
 in table 1. 
 
 TABLE 1. - Number, incidence rate, and 
 severity of back injuries suffered by 
 coal miners while working underground 
 
 Year 
 
 Number 
 
 Incidence 
 rate ' 
 
 Severity^ 
 
 1978 
 
 1979 
 
 1980 
 
 1981 
 
 2,654 
 3,617 
 3,779 
 3,007 
 
 2.74 
 3.14 
 3.39 
 3.00 
 
 102 
 114 
 136 
 141 
 
 'incidence rate is the number of back 
 injuries per 200,000 worker-hours. 
 
 ^Severity is the number of lost work- 
 days per 200,000 worker-hours. 
 
24 
 
 Table 2 breaks down the total number of 
 accidents that occurred inside under- 
 ground coal mines during 1981 according 
 to MSHA's categorization scheme for clas- 
 sification of accidents. MSHA's accident 
 classification scheme attempts to iden- 
 tify the circumstances that contributed 
 most directly to the resulting accident. 
 The first column of numbers in table 2 
 indicates that handling material accounts 
 for a much greater percentage of total 
 injuries than any other single class. As 
 shown in the last column of table 2, in- 
 juries to the back (as opposed to other 
 parts of the body) account for almost 
 half (42.7 pet) of the injuries associ- 
 ated with handling material. Within 
 classes containing relatively large num- 
 bers of injuries, the back is generally 
 associated with more injuries than any 
 other part of the body. Altogether, back 
 
 injuries account for 23 pet of all in- 
 juries reported to have occurred inside 
 underground coal mines during 1981. 
 
 In terms of the number of workdays 
 missed before the injured miner is able 
 to return to work, back injuries are a 
 relatively severe type of injury. 
 Twenty-six percent of the lost-time back 
 injuries that occurred inside underground 
 coal mines during 1981 resulted in the 
 miner missing more than 4 weeks of work. 
 The average number of workdays missed 
 after miners injured their backs was ap- 
 proximately 7 days longer than the aver- 
 age number for all nonfatal injuries (39 
 versus 32 days). Altogether, 31 pet of 
 all workdays lost to nonfatal work- 
 related injuries were attributed to in- 
 juries of the back. 
 
 TABLE 2. - Injuries suffered by underground coal miners during 1981, 
 broken down by accident classification and showing the percent 
 of back injuries in each class 
 
 Accident classification 
 
 Percentage that 
 are back injuries 
 
 Electrical (current producing) 
 
 Entrapment 
 
 Exploding vessels under pressure 
 
 Explosives and breaking agents 
 
 Falling or sliding rock or material.. 
 
 Fall of face or rib 
 
 Fall of roof 
 
 Fire 
 
 Handling material 
 
 Nonpowered hand tools 
 
 Nonpowered haulage ' 
 
 Powered haulage ' 
 
 Hoisting' 
 
 Explosion of gas or dust 
 
 Inundation 
 
 Machinery (includes power tools and 
 
 mining machines )' 
 
 Slip or fall of person 
 
 Stepping or kneeling on object 
 
 Striking or bumping^ 
 
 Other 
 
 Total and percentage 
 
 1.6 
 
 
 
 
 
 
 11.5 
 12.9 
 
 3.9 
 
 3.2 
 42.7 
 10.8 
 31.0 
 16.3 
 
 6.3 
 .1 
 
 
 
 7.6 
 21.4 
 10.5 
 10.5 
 28.7 
 
 23.0 
 
 'Accidents caused by the motion of the o 
 
 ^Excludes accidents that occurred while 
 
 handtools, or operating and/or riding mach 
 
 bject. 
 
 handling material, using 
 inery or haulage. 
 
25 
 
 In total, these injuries represent only 
 a tremendous economic cost to coal com- 
 panies, to miners and their families, and 
 to society; they represent a tremendous 
 amount of human suffering. It is obvious 
 that there is a great need to find better 
 ways to prevent back injuries to under- 
 ground coal miners. 
 
 The success of those who search for 
 better ways to prevent back injuries to 
 underground coal miners is, in part, de- 
 pendent upon the accuracy of their under- 
 standing of the causes of back injuries. 
 This paper attempts to add to what is 
 currently known about the causes of back 
 injuries to underground coal miners. The 
 
 general approach employed was to review 
 data from reports on an extensive number 
 of back injuries recently suffered by un- 
 derground coal miners, to identify the 
 basic types of accidents causing these 
 injuries, and to search for events and 
 conditions that are commonly associated 
 with them. The first section describes 
 how the data were obtained, the types of 
 injuries that were included, and the 
 types of analyses that were performed. 
 The second section presents the results 
 of data analyses and a few speculations 
 concerning how various types of accidents 
 might be prevented. The third section 
 summarizes the findings. 
 
 THE SOURCE OF DATA AND METHODS OF ANALYSIS 
 
 The types of injuries included in the 
 statistics presented in the remainder of 
 this paper are those in which a coal min- 
 er suffered a ruptured disk or a strain 
 or sprain of his or her back while work- 
 ing at an underground location. The data 
 are derived from reports that the opera- 
 tors of U.S. coal mines sent to MSHA con- 
 cerning injuries their employees suffered 
 while at work during 1981. Employers are 
 required by 30 CFR 50.2 to report to MSHA 
 all injuries that cause an employee to 
 miss one or more days of work. However, 
 if the injury did not require the em- 
 ployee to miss work, and meets certain 
 other conditions (as defined in 30 CFR 
 50.2), the employer is not required to 
 report it to MSHA. Therefore, it should 
 be noted that the statistics are based on 
 reports of both lost-time and no-lost- 
 time injuries, but that employers are not 
 required to report certain types of no- 
 lost-time injuries. 
 
 After the injury report is received by 
 MSHA's Health and Safety Analysis Center, 
 much of the information on it is trans- 
 formed into code numbers that correspond 
 to predetermined categories. For exam- 
 ple, there are a list of codes for de- 
 scribing the types of acitivity miners 
 were performing at the time they were in- 
 jured. These code numbers are then en- 
 tered into a computer file. Using a com- 
 puterized retrieval system, information 
 
 from this file can be selectively re- 
 trieved and various types of statistics 
 can be calculated. 
 
 The primary goal of this paper is to 
 use this information to identify the 
 types of activities, objects, and condi- 
 tions most frequently associated with the 
 2,492 reported cases of an underground 
 coal miner suffering a back sprain or 
 strain during 1981. The first step to- 
 ward this goal was to determine which 
 categories for describing the type of 
 accident were used most frequently. 
 
 Ninety-seven percent of these injuries 
 are categorized as one of three basic 
 types of accidents: overexertion in at- 
 tempting to move objects, falls to the 
 ground, and jolts to the occupants of ve- 
 hicles. In order to get a clearer pic- 
 ture of the circumstances that often lead 
 to each of these three types of acci- 
 dents, the injuries within each major 
 category were further broken down. De- 
 pending upon which is more conducive to 
 understanding the factors that may have 
 contributed to the accident, the second 
 level of breakdowns were based upon 
 either the type of activity the miner was 
 performing or the type of object that 
 caused or contributed to the injury. 
 Next, sets of descriptions of each acci- 
 dent were retrieved for each group of in- 
 juries that, on the basis of the second 
 
26 
 
 level breakdown, accounted for more than 
 1 pet of the total, i.e. , more than 24 
 Injuries. These verbal accounts, called 
 narratives, generally consist of one or 
 two sentences describing what the miner 
 was doing at or shortly before the time 
 back pain was noticed. 
 
 Included in the previously mentioned 
 injury reports that mine operators file 
 are written descriptions of how the acci- 
 dent occurred. These narratives are also 
 put into a computer file from which they 
 can be selectively sorted into groups and 
 retrieved. As mentioned earlier, sets of 
 narratives were generated for each group 
 of injuries accounting for more than 1 
 pet of the total. 
 
 Each of these groups of narratives was 
 reviewed and a tally was kept of the 
 types of activities, actions, environ- 
 mental conditions, etc., that appear to 
 have contributed to each miner's back in- 
 jury. Conclusions based on these tallys 
 are presented as each type of back injury 
 accident is discussed. However, for a 
 variety of reasons, these conclusions 
 
 should be interpreted cautiously, as 
 rough approximations to understanding 
 what actually happened. In some cases, 
 the injured miner or the individual who 
 wrote the narrative may not have used the 
 most accurate and descriptive language to 
 convey what happened. For example, one 
 narrative states that, "the miner hurt 
 his back while moving cable," which does 
 not indicate whether the miner was lift- 
 ing, pulling, or hanging a cable. For- 
 tunately, most narratives are more pre- 
 cise in the language they use. 
 
 It is recognized that in some cases, 
 especially those involving back pain ow- 
 ing to overexertion, it may be impossible 
 for miners to pinpoint the event that 
 caused their backs to hurt. The miner's 
 back may have begun to hurt gradually 
 over a period of time that he or she was 
 performing a variety of activities, all 
 of which contributed to overexertion of 
 the back muscles. Although the narra- 
 tives may be somewhat ambiguous and con- 
 tain some error, they significantly im- 
 prove one's ability to understand how 
 miners commonly injure their backs. 
 
 PRESENTATION OF THE DATA AND ITS IMPLICATIONS 
 
 This section presents a detailed dis- 
 cussion of each of the three major cate- 
 gories of accidents. Each major type of 
 accident is further broken down into sub- 
 sets that possess some type of common 
 element, such as similarities in the type 
 of activity the victim was performing, 
 the type of object with which the victim 
 was working, or the type of bodily move- 
 ment the miner was attempting at the time 
 of the injury. As indicated in table 3, 
 more back injuries were attributed to 
 overexertion than to any other category 
 for describing the type of accident. 
 Although 79 pet were classified as in- 
 juries because of overexertion, signifi- 
 cant numbers were also classified as 
 falls (11 pet) and jolts (7 pet). 
 
 TABLE 3. - Back injuries suffered by 
 underground coal miners during 1981 
 by accident type 
 
 Accident type 
 
 Number of 
 injuries 
 
 Percentage 
 
 Overexertion 
 
 Falls 
 
 1,958 
 
 263 
 
 183 
 
 88 
 
 79 
 11 
 
 Jolts 
 
 7 
 
 Other 
 
 3 
 
 Total 
 
 2,492 
 
 100 
 
 OVEREXERTION IN MOVING OBJECTS 
 
 Table 4 breaks down back injuries owing 
 to overexertion by the types of objects 
 miners were attempting to move. The most 
 common types of objects being moved at 
 
27 
 
 the time of a back injury were electric 
 cables, broken rock and coal, timbers and 
 posts, metal objects (not elsewhere 
 classified), belt conveyors, wooden ob- 
 jects (not elsewhere classified), steel 
 rails, bagged material systems, jacks, 
 mining machines, roof bolts, oil contain- 
 ers, cement blocks, buckets and cans, 
 metal covers and guards, pry bars, mo- 
 tors, wheels, and boxes. As table 4 in- 
 dicates, the movement of each of these 
 categories of objects accounts for at 
 least 1 pet of the total and, together, 
 they account for 83 pet of all back in- 
 juries due to overexertion. 
 
 TABLE 4. - Overexertion back injuries 
 suffered by underground coal miners 
 during 1981, by the type of objects 
 associated with the injury 
 
 Type of object 
 
 Number of 
 injuries 
 
 Percent- 
 age 
 
 Electric cables 
 
 Broken rock and coal 
 Timbers and posts... 
 
 Metal objects' 
 
 Belt conveyor 
 systems ............ 
 
 233 
 231 
 198 
 156 
 
 99 
 82 
 82 
 82 
 61 
 49 
 49 
 48 
 47 
 46 
 
 43 
 33 
 33 
 32 
 30 
 324 
 
 11.9 
 
 11.8 
 
 10.1 
 
 8.0 
 
 5.1 
 
 Wood objects^ 
 
 Steel rails 
 
 4.2 
 4.2 
 
 Bagged materials.... 
 Jacks ............... 
 
 4.2 
 3.1 
 
 Mining machines 
 
 Roof bolts 
 
 Oil containers 
 
 Cement blocks 
 
 Buckets and cans.... 
 Metal covers and 
 guards ............. 
 
 2.5 
 2.5 
 2.5 
 2.4 
 2.3 
 
 2.1 
 
 Pry bars ............ 
 
 1.7 
 
 Motors 
 
 1.7 
 
 Wheels 
 
 1.6 
 
 Boxes ............... 
 
 1.5 
 
 Other 
 
 16.6 
 
 Total 
 
 1,958 
 
 100.0 
 
 'Does not include metal objects such as 
 rails, roof bolts, jacks, motors, etc., 
 that are listed in other categories. 
 
 ^Does not include timbers, posts, caps, 
 and headers. 
 
 Electric Cables . Based upon MSHA's 
 categorization scheme, the movement of 
 electric cables was associated with more 
 back injuries due to overexertion than 
 
 the movement of any other type of object. 
 Forty-two percent of the narratives for 
 these accidents indicate that the miner 
 was pulling on a cable, 17 pet indicate 
 that the miner was lifting a cable, and 
 11 pet indicate that the miner was hang- 
 ing or lowering a cable. The remaining 
 narratives use less specific terms to de- 
 scribe the miner's actions (e.g., moving 
 or handling cable) or describe relatively 
 unique types of accidents. 
 
 Broken Rock and Coal. The second most 
 
 coEimon category of object associated with 
 
 overexertion injuries was broken rock and 
 
 coal. The movement of rock and coal 
 
 accounted for almost as many overexer- 
 tion injuries as cables (11.9 versus 
 11.8 pet). 
 
 Approximately half of the narratives 
 attribute the injury to shoveling and a 
 quarter of the narratives attribute the 
 injury to the manual lifting of broken 
 rock and coal. The remaining narratives 
 attribute the injury to other types of 
 movement such as the dragging, rolling, 
 or pulling of rocks. 
 
 Timbers and Posts . The third most com- 
 mon category of objects associated with 
 overexertion injuries consisted of tim- 
 bers, posts, caps, and headers. The nar- 
 ratives refer to timbers and posts much 
 more frequently than caps and headers. 
 The types of movements most often men- 
 tioned in the narratives are lifting, 37 
 pet; loading and unloading, 16 pet; and 
 throwing, 10 pet. The remaining narra- 
 tives generally use less specific terms 
 to describe the miner's actions such as 
 setting, moving, or handling timber. The 
 narratives usually describe back injuries 
 due to throwing as "twist" of the back, 
 suggesting that the injury occurs because 
 miners often twist their body instead 
 of pivoting on their foot when throwing 
 timbers. 
 
 Metal Objects (not elsewhere classi- 
 fied). A review of the narratives indi- 
 cates that there is no one specific type 
 of metal object that accounts for a sig- 
 nificant portion of the injuries in this 
 category. The types of items mentioned 
 include pipes, wire, coupling hitches, 
 
28 
 
 ramps, and roof bolt augers. The types 
 of movements most often mentioned in the 
 narratives are lifting, 52 pet; loading 
 and unloading, 10 pet; carrying, 10 pet. 
 
 Belt Conve yor Systems . A review of the 
 narratives indicates that the movement of 
 each of three elements of belt conveyor 
 systems was associated with roughly a 
 quarter of the overexertion back injuries 
 in this category. One of these elements 
 is the belt structure. Narratives men- 
 tioning belt structures usually state 
 that miners were lifting, unloading, or 
 carrying them when their backs were in- 
 jured. A second element is rollers. 
 Narratives mentioning rollers usually 
 state that miners were lifting or chang- 
 ing them when their backs were injured. 
 The third element is the belt itself. 
 Narratives mentioning belts usually state 
 that miners were pulling, lifting, or 
 loading belt material. 
 
 Wooden Objects (not elsewhere classi- 
 fied) . The types of items most often 
 mentioned in the narratives for this cat- 
 egory are crib blocks, boards, crossbars, 
 planks, and props. Other than crib 
 blocks, which account for almost half, no 
 one specific type of wooden object is as- 
 sociated with a significant portion of 
 this category of injuries. Most narra- 
 tives indicate that these injuries oc- 
 curred as the object was being lifted. 
 
 Steel Rails . About half of the narra- 
 tives for this category of injuries indi- 
 cate that the injury occurred while lift- 
 ing rails. Most of the remaining inju- 
 ries are attributed to loading, pulling, 
 or pushing on rails. These accidents 
 usually occur during the installation of 
 rails as tracks or as roof supports. 
 
 Bagged Materials . The narratives re- 
 veal that three-quarters of the bags be- 
 ing moved when the injury occurred con- 
 tained rock dust, and that the others 
 contained tools, cement mix, powder, and 
 sand. Almost all the narratives state 
 that the miner's back was injured while 
 lifting or loading bags. A few narra- 
 tives give the weight of the bag(s) that 
 had been lifted when the injury occurred. 
 Those which do, indicate that the rock 
 
 dust bags weighed 50 lb, and that the 
 bags of other materials were heavier, up 
 to 100 lb each. 
 
 Jacks . Most narratives for this cate- 
 gory state that miners were lifting a 
 jack when their backs were injured. How- 
 ever, several narratives state that the 
 miner was using a jack to remount de- 
 railed vehicles when the back injury 
 occurred. 
 
 Mining Machines . This category of back 
 injuries includes those suffered during 
 the operation, maintenance, or repair of 
 underground mining machines, but does not 
 include injuries suffered while lifting 
 motors or while riding or operating ve- 
 hicles. The narratives indicate that 
 approximately half of these injuries were 
 associated with roof bolting machines. 
 Several injuries are also attributed to 
 lifting rock dust machines. 
 
 Roof Bolts, 
 
 About half of the narra- 
 
 tives indicate that the back injury was 
 received while the miner was unloading or 
 lifting roof bolts. About one-third 
 state that the miner was injured while 
 attempting to bend a roof bolt. 
 
 Oil Containers. Most narratives for 
 this category of back injuries state that 
 the injury occurred as barrels of oil 
 were being lifted or loaded onto equip- 
 ment. Several injuries occurred while 
 oil was being poured into machinery and 
 while miners were attempting to upright a 
 barrel that was lying on its side. 
 
 Cement Blocks. 
 
 About half of the 
 
 narratives for this category of back 
 injuries indicate that the injury oc- 
 curred as cement blocks were being lifted 
 and/or carried. Roughly a quarter of 
 the narratives state that the injury oc- 
 curred while blocks were being loaded or 
 unloaded. 
 
 Buckets and Cans. Most narratives for 
 
 this category of back injuries indicate 
 that the injury occurred during the 
 movement of buckets or cans of oil, 
 grease, or water. Many narratives state 
 that the bucket or can being moved was 
 the 5-gal size. 
 
29 
 
 Metal Covers and Guards . Most narra- 
 tives for this category of back injuries 
 reveal that the injury occurred during 
 the removal or installation of the metal 
 guards, covers, and canopies on under- 
 ground powered equipment. The narratives 
 also suggest that several of the back in- 
 juries in this category occurred as bat- 
 tery lids were being lifted. 
 
 prolonged periods of time without rest. 
 Shoveling can place unusually great 
 stress on the back. Therefore, indi- 
 viduals with a history of back problems 
 should be especially careful not to over- 
 exert themselves while shoveling. The 
 data also suggest that miners should be 
 discouraged from trying to throw objects 
 as heavy and cumbersome as timbers. 
 
 Pry Bars . Almost all narratives for 
 this category of back injuries indicate 
 that the miner was using a pry bar or 
 crowbar to pry or lift on parts of 
 machines or equipment. A small number 
 attribute the injury to prying down loose 
 top. 
 
 Motors. 
 
 The narratives for this cate- 
 
 gory of back injuries generally state 
 that the injury was received while at- 
 tempting to lift an underground mining 
 machine's motor. 
 
 Wheels . Most narratives for this cate- 
 gory of back injuries reveal that the in- 
 jury occurred when tires were being load- 
 ed or unloaded, or when a tire was being 
 lifted onto a vehicle's wheel unit. 
 
 Boxes . One and one-half percent of the 
 overexertion back injuries were attrib- 
 uted to the movement of boxes. The types 
 of boxes mentioned most frequently in the 
 narratives are toolboxes, dust boxes, and 
 boxes of cutting bits for the continuous 
 miner or bolter. 
 
 IMPLICATIONS FOR PREVENTION 
 
 The data suggest that there is an espe- 
 cially great need to (1) improve upon 
 present methods and equipment for manual- 
 ly handling power cables, broken rock and 
 coal, and timbers and posts in under- 
 ground coal mines, or (2) find ways to 
 lessen the amount of human (as opposed to 
 mechanical) effort that must be devoted 
 to handling these materials. The data 
 also suggest that there is a need to 
 prevent miners from using shovels in ways 
 that are likely to place too much stress 
 on the back. Miners should be discour- 
 aged from using shovels to lift ob- 
 jects that are too big, or shoveling for 
 
 Potter2 presents tables of data con- 
 cerning the recommended maximums for the 
 amount of weight that should be lifted, 
 pushed, or pulled by individuals accord- 
 ing to their age and sex. He goes on 
 to list the common weights of many of 
 the objects that must be manually moved 
 in underground coal mines, and points 
 out that many of these objects exceed 
 the recommended limits for most types 
 of individuals. On the basis of these 
 data. Potter suggests that several types 
 of mining supplies and materials should 
 be manufactured and packaged in smaller 
 quantities. 
 
 FALLING TO THE GROUND 
 
 The second type of accident that ac- 
 counts for a significant portion of min- 
 ers' back injuries is falling to the 
 ground. In 1981, 10.6 pet of the back 
 injuries suffered by underground coal 
 miners were the result of falling to the 
 ground. Back injuries due to falls were 
 further broken down by the activity the 
 miner was performing at the time of the 
 fall. The activities mentioned most fre- 
 quently are walking, 26 pet, and handling 
 supplies, 24 pet. Several miners also 
 injured their backs while getting on or 
 off equipment, handling timber, and mov- 
 ing cable. However, in terms of the por- 
 tion of total back injuries, the number 
 associated with these last three activi- 
 ties is relatively insignificant. There- 
 fore, only falls associated with walking 
 or handling supplies will be discussed. 
 
 2potter, H. H. Back In juries--Causes 
 and Cures. Pres. at Fall Meeting, See. 
 Min. Eng. , AIME, Denver, CO, Nov. 18, 
 1981, 10 pp.; available for consultation 
 at MSHA's Division of Coal Mine Safety 
 and Health, Denver, CO. 
 
30 
 
 Walking . A review of the narratives 
 for back, injuries associated with falls 
 while walking reveals that most such ac- 
 cidents were the result of slipping on 
 mud or a wet surface. Other phases fre- 
 quently used to describe the cause of 
 falls are "stepping in a hole," and 
 "tripping over" things on the ground. 
 
 Handling Supplies . A review of nar- 
 ratives for back injuries associated with 
 falls while handling supplies reveals 
 that such accidents were most frequent- 
 ly the result of slipping on a wet or 
 muddy surface while carrying something, 
 or slipping while trying to pull on 
 something. 
 
 that they cause operators to strike their 
 heads on the canopy above them. It would 
 be possible to prevent some of these ac- 
 cidents by doing the following: keeping 
 the floor of the mine more level; cau- 
 tioning shuttlecar operators to slow down 
 for rough spots; increasing illumination 
 of the mine floor, or providing some type 
 of warning that signifies the presence 
 of rough spots; putting cushions in the 
 seat and on the canopy above the opera- 
 tor; and requiring the use of seatbelts. 
 It should be noted that these suggested 
 solutions are by no means an exhaustive 
 list, and that it may not yet be econom- 
 ically feasible to implement some of 
 them. 
 
 Possible ways to prevent such accidents 
 include keeping work areas as dry as pos- 
 sible, keeping walking surfaces as level 
 as possible and free of obstacles, im- 
 proving illumination along walkways, and 
 using boots with tread designs that pre- 
 vent slipping on wet surfaces. 
 
 JOLTS 
 
 The third major type of accident re- 
 sulting in back injuries consists of 
 jolts to the occupants of underground ve- 
 hicles. In 1981, 7.3 pet of the back in- 
 juries suffered by underground coal min- 
 ers were the result of the miner's body 
 striking against a relatively stationary 
 object. These injuries were further 
 broken down by the activity being per- 
 formed at the time of the accident. It 
 was found that 28 pet of the victims of 
 this category of accidents were operating 
 a shuttle car, and 21 pet were riding in 
 a mantrip or Jeep. 
 
 Operating Shuttle Cars . A review of 
 narratives for back injuries to the oper- 
 ators of shuttle cars reveals that such 
 injuries were almost always due to the 
 operator being jolted when the shuttle 
 car ran over a bump, hole, or rough spot 
 in the mine floor. Some narratives de- 
 scribe these jolts as being so severe 
 
 Riding in Underground Transportation 
 Vehicles . Back injuries suffered by the 
 occupants of underground transportation 
 vehicles were usually caused by one of 
 two types of mishaps. The first type of 
 mishap is that, like shuttle car opera- 
 tors, miners received back injuries from 
 being jolted when their vehicle ran over 
 uneven places in the mine floor or in the 
 tracks on which certain types of vehicles 
 run. The second type of mishap, which 
 caused as many back injuries as the 
 first, was the collision of vehicles. 
 Such collisions result in sudden jolts to 
 the vehicle's occupants, sometimes caus- 
 ing them to experience back pain. Many 
 of the measures suggested for preventing 
 back injuries to shuttle car operators 
 would also be applicable to the operation 
 of underground transportation vehicles. 
 The following measures might also reduce 
 the number of vehicle-related back inju- 
 ries: encouraging miners to keep the 
 roadways free of parked vehicles and 
 other obstructions; encouraging vehicle 
 operators to be more attentive to possi- 
 ble obstructions in the roadway; and en- 
 suring that vehicles, their brakes, and 
 the track on which they run are properly 
 maintained. Consideration might also be 
 given to the use of better shock absorb- 
 ing devices on these vehicles. 
 
31 
 
 SUMMARY AND CONCLUSIONS 
 
 A review of recent data on back, inju- 
 ries suffered by underground coal miners 
 suggests that many factors contribute to 
 their occurrence. The action most fre- 
 quently associated with these injuries is 
 overexertion in lifting things. The 
 types of things being lifted that are 
 most frequently associated with back in- 
 juries are cables, broken rock and coal, 
 and timbers and posts. Another common 
 form of overexertion causing back inju- 
 ries is pulling on things. The object 
 that causes the majority of back injuries 
 due to pulling is power cables. Another 
 activity associated with many back inju- 
 ries due to overexertion is the shoveling 
 of broken rock and coal. 
 
 Although most back injuries are due to 
 overexertion, a significant number of 
 them are due to falls and jolts. The in- 
 juries due to falls are typically the re- 
 sult of slipping on a wet or muddy sur- 
 face, or tripping over something while 
 handling materials or while simply walk- 
 ing. The injuries due to jolts are typi- 
 cally the result of running over uneven 
 
 places in the mine floor while riding in 
 shuttle cars or underground transporta- 
 tion vehicles. Another common type of 
 mishap causing back injuries to the occu- 
 pants of underground transportation ve- 
 hicles is the collision of their vehicle 
 into another vehicle. 
 
 The fact that there are so many factors 
 that contribute to underground miners' 
 back injuries suggests that there are a 
 variety of actions that could be taken to 
 reduce back injuries, but that no one 
 approach will be a panacea. The fact 
 that most back injuries are the result of 
 overexertion in the manual movement of 
 things suggests that back injuries could 
 be reduced most significantly by changing 
 the way these things are moved, or elimi- 
 nating the need to move some of them. 
 Thus, although it is very important that 
 more attention be devoted to the preven- 
 tion of falls and jolts, there is an ex- 
 tremely great need to devote more atten- 
 tion to the prevention of overexertion 
 injuries. 
 
32 
 
 ANALYSIS OF COAL MINING BACK INJURY STATISTICS 
 By Terrence J. Stobbel and Ralph W. Plummer2 
 
 ABSTRACT 
 
 Injury and illness in industry are at 
 best complex problems. One of the big- 
 gest of these problems is the overexer- 
 tion injury. This is commonly character- 
 ized as a strain or sprain injury. In 
 its most severe form, it occurs to the 
 back and necessitates disk surgery. 
 
 This study collected and analyzed ex- 
 isting data of job-related overexertion 
 
 injury data for coal miners employed by a 
 major coal company during the years 1977- 
 82. The purpose of this analysis was to 
 determine the magnitude of overexertion 
 injuries, to determine the severity of 
 the injuries, and to identify specific 
 activities that account for large numbers 
 of back injuries. 
 
 INTRODUCTION 
 
 The desire to control injury and ill- 
 ness in coal mining is motivated by hu- 
 manitarian and economic factors. The 
 need to reduce pain and suffering not on- 
 ly to the injured persons, but to their 
 families and associates as well, is obvi- 
 ous. The economic basis is perhaps less 
 clear. The injured miner often loses a 
 significant portion of his or her income 
 while off the job. The employer pays the 
 medical and indemnity costs of workmen's 
 compensation, along with an equivalent 
 amount in hidden costs, such as retrain- 
 ing, administrative functions, etc. Coal 
 mining is recognized as being one of the 
 most hazardous industries. The high de- 
 gree of hazard is reflected in the asso- 
 ciated workmen's compensation costs. In 
 West Virginia, underground coal mining 
 has a base rate for compensation which is 
 second only to high-rise structural steel 
 work. The base rate, which is almost 
 20 pet of payroll dollars, is more than 
 twice the third place job activity — 
 working in a sawmill. The base rate is 
 adjusted up or down based on individual 
 company experience and, as a result, some 
 coal companies pay compensation premiums 
 that are equal to three-fourths of pay- 
 roll dollars. 
 
 ^President, S&P Associates, Morgantown, 
 WV. 
 
 ^Vice president, S&P Associates, Mor- 
 gantown, WV. 
 
 Reduction of these costs is dependent 
 on understanding their causes. One well- 
 known cause is the overexertion injury. 
 This type of injury ranges from strain 
 and sprain to the more severe back injury 
 that requires surgery. Nationally, these 
 injuries account for 30 to 40 pet of all 
 reported injuries, and at least as high a 
 percentage of the compensation costs. 
 Back injuries are a subset of these inju- 
 ries, which account for about 20 pet of 
 all reported injuries. 
 
 The situation in coal mining is similar 
 but worse. Accident statistics for West 
 Virginia show that in 1979 back injuries 
 accounted for 23 pet of all injuries. 
 MSHA3 reported that, in 1980, back inju- 
 ries accounted for 26 pet of all coal 
 mining injuries. The associated compen- 
 sation costs are estimated to be 30 to 40 
 pet of the total compensation costs (for 
 the company in this study). Having iden- 
 tified the source of a significant por- 
 tion of the coii^)ensation costs, we must 
 look to understanding the cause of over- 
 exertion and back injuries. 
 
 In trying to understand the causes of 
 these injuries, it is instrumental to 
 
 -^Potter, H. H. Lack of Mechaniza- 
 tion in Some Coal Mine Tasks. Mine Safe- 
 ty and Health Magazine, Dec-Jan. 1982, 
 pp. 8-13. 
 
33 
 
 look first to general industry where 
 most of the back injury related research 
 has been. This research has shown that 
 the major causes of back injury are mate- 
 rials handling, slip-trip, and push-pull. 
 Within these categories, materials han- 
 dling predominates, and it is considered 
 to be such a major problem that NIOSH has 
 published a lengthy Work Practices Guide 
 for Manual Lifting4 that summarizes what 
 is currently known about the problem 
 as well as providing control recommenda- 
 tions. In essence, the guide reports 
 that people who lift too much too often 
 experience back and overexertion inju- 
 ries. The guide then proposes a method 
 for estimating relatively safe weights to 
 lift under ideal lifting conditions. 
 
 Looking now at coal mining, it is again 
 found that the situation is similar but 
 worse. Materials handling is a major ac- 
 tivity in the mines, and in most mines it 
 is increasing in frequency as the rate of 
 mining coal increases. 5 Loads handled 
 are equal to or heavier than those han- 
 dled in general industry. Typical "man- 
 handled" loads are shown in table 1. The 
 work practice guide emphasizes that 
 its recommendations apply to ideal lift- 
 ing conditions. However, lifting condi- 
 tions in coal mining are far from ideal. 
 Loads are bulky and do not have handles, 
 and furthermore, floor conditions vary 
 from dry and uneven to wet, muddy, and 
 slippery. 
 
 TABLE 1. - Weights of materials commonly 
 handled in coal mines 
 
 Materials lb 
 Roof bolts: 
 
 5/8 in by 6 ft, bundle of 10 55 
 
 5/8 in by 10 ft, bundle of 10 90 
 
 Crossbar, oak, 4 by 6 in by 16 ft... 129 
 
 Round post, oak, 6-in diam by 6 ft.. 57 
 
 Concrete block, 8 by 8 by 16 62 
 
 Cement, 1 bag 80 
 
 Rock dust, 1 bag 50 
 
 Rail, 30 lb, 30-ft length 300 
 
 ^. S. Department of Health and Human 
 Services. Work Practices Guide for Man- 
 ual Lifting. NIOSH Pub. 81-122, 1981, 
 183 pp.; NTIS PB 82-178-948. 
 
 ^Work cited in footnote 3. 
 
 With respect to the above, the Bureau 
 of Mines sponsored this study of coal 
 mining back injuries. To the extent pos- 
 sible, this description includes such 
 factors as job, task, materials handled, 
 mine height, time of year, repeated inju- 
 ries to the same miner, and exposure 
 hours. 
 
 The results of this study are aimed at 
 reducing back injuries in coal mining. 
 This will be accomplished by applying the 
 result of this study to (1) identifying 
 specific jobs with high back injury fre- 
 quency rates based on hours of exposure 
 (work); (2) conducting job safety and 
 physical stress anslyses of these jobs to 
 isolate specific tasks or work procedures 
 that increase the risk of back injury; 
 (3) isolating tools, supplies, equipment, 
 etc. , that act as causes or agents in a 
 significant number of back injury scenar- 
 ios; and (4) redesigning or modifying the 
 tasks, work procedures, tools, supplies, 
 or equipment that significantly increase 
 back injuries. 
 
 METHODOLOGY 
 
 The purpose of this research was to 
 develop a set of statistics that would 
 describe the back injury problem in coal 
 mining in sufficient detail so that 
 future research directions could be 
 identified. Two sources of data were 
 available: the MSHA's Health and Safety 
 Analysis Center (HSAC) data base and in- 
 dividual company accident-injury records. 
 Each data base had advantages to its use. 
 HSAC records covered all of the mining 
 industry, thus a larger data base was 
 available. They were, however, based on 
 a single reporting form, and their ac- 
 curacy suffered to the extent that dif- 
 ferent companies and mines use different 
 titles to describe the same job or activ- 
 ity or the same title to describe differ- 
 ent jobs and activities. Individual com- 
 pany records were limited in that a much 
 smaller data base was available, but they 
 were superior because considerable back- 
 ground information was available beyond 
 the HSAC reporting form. In addition, a 
 comprehensive review of a large coal pro- 
 ducer's back injury statistics was not 
 available in the literature. 
 
34 
 
 In view of the above, individual com- 
 pany statistics were used. Contact was 
 made with a large coal producer and after 
 some discussion it was agreed that the 
 analysis would be mutually beneficial. 
 Access was provided to all of the com- 
 pany's accident records. This included 
 the company's internal first injury re- 
 port, the HSAC form, the company's inter- 
 nal statistical report, and miscellaneous 
 data that found their way into individual 
 accident files. All of these data were 
 reviewed for the 6-yr period 1977-82, 
 during which a total of 974 back injuries 
 were reported. Correct interpretation of 
 the data required frequent contact with 
 company personnel in a number of areas 
 including the medical department, safety 
 department (corporate and field) , mine 
 supervision, industrial relations, com- 
 pensation, and industrial engineering. 
 
 The review of the accident data pro- 
 vided an excellent description of the 
 nature, source, and frequency of back, 
 injuries, but without exposure data, it 
 was difficult to interpret. Exposure 
 data were collected with the additional 
 help of the company's industrial engi- 
 neering group. As expected, collection 
 and interpretation of both exposure and 
 accident data were difficult since there 
 were numerous mine-to-mine inconsisten- 
 cies in the titles placed on jobs and 
 activities. These inconsistencies were 
 identifiable only with the help of com- 
 pany personnel. 
 
 The actual data collection process in- 
 volved reading all of the information 
 contained in each accident file and cod- 
 ing it for later analyzing using a sta- 
 tistical analysis system (SAS). The fol- 
 lowing is a partial list of the data 
 collected. 
 
 Bureau of Mines identification. 
 
 Primary cause. 
 
 Secondary cause. 
 
 Agent of injury. 
 
 Sex of injured miner. 
 
 Total mining experience. 
 
 Permanent job classification. 
 
 Date injury occurred. 
 
 Time of day injury occurred. 
 
 Date injury reported. 
 
 Job being performed when injury 
 occurred. 
 
 Total experience in job being performed 
 when injured. 
 
 Part of body injured. 
 
 The unique feature of this data set is 
 the inclusion of the primary and second- 
 ary causes of the injury, as well as the 
 agent of injury. Partial lists of these 
 variables are provided in the following 
 tabulations. 
 
 Primary cause: 
 
 Lifting-twisting Jumping from 
 
 vehicle. 
 
 Tripped 
 
 Slipped 
 
 Pulling 
 
 Fell 
 
 Shoveling 
 
 Stumbled 
 
 Carrying 
 
 Pushing 
 
 Hit canopy 
 
 Prying 
 
 Hit bump (vehicle) 
 
 Twisting 
 
 Hit rough road Pulling down 
 
 (vehicle) Hit by object 
 
 Bend over and/or Handling supplies 
 
 lifting. Striking head 
 
 Secondary cause ; 
 
 Crib block Supply car 
 
 Swinging pick Walking 
 
 Landed on seat Unbalanced load 
 
35 
 
 Secondary cause — Continued: 
 
 Lifted over head Slipped 
 
 Timber Roof bolter 
 
 Absence of guard Fell against post 
 
 Wet area Blasting 
 
 Operating motor Climbing ladder 
 
 Twisted body Slipped on a rock 
 
 Climbing railroad Fan house 
 car. 
 
 Agent category : 
 Steel rope 
 Plank 
 Stone falls 
 
 Bag of rock dust 
 Trolley wire 
 Railroad ties 
 
 Concrete blocks Chunk of coal 
 
 Hit canopy Culvert pipe 
 
 Pry bar Straighten up 
 
 Shoveling Drill unit 
 
 Hit roof bolt Post 
 
 Air jack Stepped in hole 
 
 Jarred Using a wrench 
 Primary cause ; 
 
 Lifting-twisting Carrying 
 
 Tripped Pushing 
 
 Slipped Hit canopy 
 
 Pulling Prying 
 
 Fell Hit bump (vehicle) 
 
 Shoveling Twisting 
 
 Stumbled Pulling down 
 
 Primary cause — Continued: 
 
 Hit rough road Hit by object 
 (vehicle). 
 
 Bend over and/or Handling supplies 
 lifting. 
 
 Jumping from Striking head 
 vehicle. 
 
 Secondary cause : 
 
 Crib block Supply car 
 
 Swinging pick Walking 
 
 Landed on seat Unbalanced load 
 
 Lifting over head Slipped 
 
 Timber Roof bolter 
 
 Absence of guard Fell against post 
 
 Wet area Blasting 
 
 Operator motor Climbing ladder 
 
 Twisted body Slipped on a rock 
 
 Climbing railroad Fan house 
 car. 
 
 Agent category ; 
 
 Steel rope Bag of rock dust 
 
 Plank Trolley wire 
 
 Stone falls Railroad ties 
 
 Concrete blocks Chunk of coal 
 
 Hit canopy Culvert pipe 
 
 Pry bar Straighten up 
 
 Shoveling Drill unit 
 
 Hit roof bolt Post 
 
 Air jack Stepped in hole 
 
 Jarred Using a wrench 
 
36 
 
 Use of this multiple coding scheme 
 allowed the subsequent analysis to go 
 beyond the usual analysis which reveals 
 that X people were injured lifting, 
 Y pulling, etc. ; G people were handling 
 timbers, H bags, etc. Instead it was 
 possible to identify the number injured 
 by lifting by each agent category. Fur- 
 thermore, this approach permitted the 
 identification of those situations in 
 which the person was lifting a timber 
 and slipped. Clearly, it is not known 
 whether it was the lift or the slip 
 that caused the injury, but the fact 
 that they were lifting a heavy object 
 when they slipped certainly contributed 
 to the injury. The slip would probably 
 not have occurred without the force dy- 
 namics that lifting places on the body, 
 and the injury may not have occurred 
 without the sudden body movement owing to 
 the slip. In most conventional data 
 analyses, this would be coded simply as 
 
 a lift or a slip and the joint cause 
 would be lost. 
 
 In addition to developing the descrip- 
 tive statistics, the effects of mine 
 height, the contribution of back injury 
 repeaters to the overall problem, and the 
 often repeated argument that people take 
 advantage of the back injury to get a few 
 days off during hunting season were stud- 
 ied. Mine height was provided by indus- 
 trial engineering and grouped into four 
 categories. Where meaningful, the data 
 were statistically analyzed to determine 
 which conditions were significant. 
 
 There is one element not included in 
 this discussion — cost data. At the time 
 of writing, this information was still 
 being prepared by the compensation de- 
 partment. When received and analyzed 
 this will make a valuable addition to 
 this study. 
 
 RESULTS 
 
 The comprehensive review of 6 yr of 
 back injury data results in a massive 
 amount of data. It is not practical to 
 describe all of it in a single paper. 
 Rather, this paper will present the re- 
 sults of selected analyses. The report- 
 ing order will be to report the mixed-job 
 statistics first, followed by in-depth 
 analyses of selected jobs. The preva- 
 lence of back injuries in coal mining was 
 discussed in the introduction. From a 
 control standpoint, the more interesting 
 question is who suffers these injuries. 
 When the question is discussed with min- 
 ing management, it becomes clear that a 
 mystique has developed about back inju- 
 ries within which the persons concerned 
 have developed their own theories of 
 causation, often without supporting data. 
 Common examples which were suggested fre- 
 quently included 
 
 1. They lift the wrong way. 
 
 2. They try to lift too much. 
 
 3. There is always a rash of them when 
 the miners want a few days off. 
 
 4. It is the same miners who get hurt 
 over and over again. 
 
 The data analyzed herein do not address 
 the first two issues, so all that can be 
 done is to point out that there is no 
 single best way to lift. The "lifting 
 method is dependent on the nature of the 
 load and environmental circumstances sur- 
 rounding the lift, "6 With respect to the 
 size of the lift, it is true that miners 
 often lift too much — but who is responsi- 
 ble? Who designs the jobs, specifies the 
 weights of supplies, and determines the 
 work pace? Furthermore, how is an indi- 
 vidual miner supposed to know how much he 
 or she can lift? 
 
 There were data available in this study 
 to address issues 3 and 4. The use of a 
 back injury to selectively obtain extra 
 time off is supposedly one with some fre- 
 quency. In the mystique, hunting season 
 is the prime time for convenient back in- 
 juries. To evaluate the issue, contact 
 was made with the Natural Resources De- 
 partments of the States in which injuries 
 were reported to identify the dates of 
 hunting season during the years studied. 
 The mean number of back injuries that oc- 
 curred during hunting season was com- 
 puted and compared year by year to the 
 
 ^Work cited in footnote 4. 
 
37 
 
 in table 2, show 
 mystique is wrong. 
 
 mean number of back injuries occurring on 
 any other day of the year. The week pre- 
 ceding hunting season was included with 
 the hunting data. The results, presented 
 that the conventional 
 The statistical anal- 
 ysis demonstrates that there are fewer 
 back injuries per day just before and 
 during hunting season, than during the 
 rest of the year. 
 
 TABLE 2. - Comparison of back injury 
 rate (BIR) preceding and during 
 hunting season with the BIR during 
 the rest of the year 
 
 frequency rate for mining jobs with high 
 back injury frequencies. The frequency 
 provides a relative comparison of the 
 magnitude of the problem per job, while 
 the frequency rate indicates the likeli- 
 hood of getting hurt on a given job by 
 adjusting the frequency for exposure 
 hours. As expected, those jobs requiring 
 considerable manual materials handling 
 are the jobs with the highest rates. The 
 possible exception to this is the shuttle 
 car operator. 
 
 TABLE 4. - Comparison of frequency and 
 frequency rates for coal mining jobs 
 
 BIR — hunting. . . . 
 BIR — nonhunting. 
 
 Mean 
 
 0.312 
 .418 
 
 Variance 
 
 0.223 
 .488 
 
 NOTE. — T-test calculated = 2.262. T- 
 test tabular value = 1.645 for a = 0.05. 
 
 Issue 4, back injury repeaters, also 
 proved to be more mystique than fact. 
 Table 3 presents the number of injuries 
 per miner during the 6-yr period. Re- 
 peated back injuries, at least during 
 the time period studied, were infrequent. 
 The data were examined further to see 
 if there was a pattern to the timing of 
 injuries in the repeater, and none was 
 found. The distribution of job titles 
 among the repeaters was consistent with 
 that of the overall study. 
 
 TABLE 3. - Frequency of back injuries 
 per miner during the 6-yr period 
 1977-82 
 
 Number of miners Injuries 
 
 10,000 
 
 882 1 
 
 40 2 
 
 4 3 
 
 The next section of the report ad- 
 dresses the questions of which jobs 
 have a high frequency of back injuries 
 and what causes them (doing what) . Ta- 
 ble 4 presents the injury frequency and 
 
 
 Frequency, 
 
 Frequency 
 
 Job title 
 
 number of 
 
 rate per 
 
 
 injuries 
 
 thousand h 
 
 Laborer. .......... 
 
 158 
 41 
 
 37.05 
 
 Trackman-helper. . . 
 
 29.42 
 
 Brattice worker. . . 
 
 18 
 
 18.30 
 
 Shuttle car 
 
 
 
 operator. ........ 
 
 95 
 129 
 
 15.74 
 
 Mechanic-helper. . . 
 
 13.22 
 
 Continuous miner 
 
 
 
 operator-helper. . 
 
 54 
 
 10.73 
 
 Roof bolter-helper 
 
 67 
 
 10.29 
 
 In addition to looking at jobs, this 
 study reviewed causes (activities at the 
 time of injury), and agents (things han- 
 dled or producing the injury). Table 5 
 presents an overview of the cause of 
 injury. Clearly, materials handling- 
 related injuries dominate the list. The 
 materials handling category includes 
 lifting of all forms (carrying, twisting, 
 bending, single- and two-person lift, 
 etc.). Table 6 presents an overview of 
 the agent handled at the time of injury. 
 In this case, no one category stands out. 
 Handling supplies such as bagged or 
 drummed materials and concrete blocks is 
 the most frequent, but back injuries due 
 to riding in vehicles, handling timbers, 
 planks and posts, and cable handling are 
 close behind. The data presented in 
 table 6 are consistent with the high fre- 
 quency of materials handling-related in- 
 juries found in table 5. 
 
38 
 
 TABLE 5. - High-frequency causes of back 
 injury in coal mining 
 
 Causes Frequency 
 
 Lifting^ 158 
 
 Lift-twist' 107 
 
 Slip-trip 107 
 
 Push-pull 93 
 
 Bend lift' 41 
 
 Hit by object 41 
 
 Working 24 
 
 Unload ' 19 
 
 Operating machine 18 
 
 ' Several causes were combined to form 
 materials handling. 
 
 TABLE 6. - High-frequency agents of back 
 injury in coal mining 
 
 Agents Frequency 
 
 Handling general supplies 101 
 
 Planks, timbers 91 
 
 Riding in vehicle 90 
 
 Cables 84 
 
 Railroad related 69 
 
 Tools 57 
 
 Shovel, wheelbarrow 52 
 
 The data in tables 5 and 6 can be 
 broken down further by investigating 
 the relationship between cause and agent. 
 Table 7 provides a frequency distribu- 
 tion for agents associated with materi- 
 als handling. Table 8 provides agents 
 for slip-trip, and table 9 for push-pull. 
 Each cause of injury has its own dominant 
 agents. 
 
 TABLE 7. - Frequency distribution for 
 agents of materials handling' injuries 
 
 TABLE 8. - Frequency distribution for 
 agents of slip-trip' injuries 
 
 Agent Frequency 
 
 Floor conditions 69 
 
 Tools and equipment 13 
 
 Railroad related 12 
 
 Supplies 7 
 
 Stairs 5 
 
 Planks and timbers 4 
 
 ' Primary cause of 138 back injuries. 
 
 TABLE 9. - Frequency distribution for 
 agents of push-pull' injuries 
 
 Agent 
 
 Frequency 
 
 Agent 
 
 Frequency 
 
 Cable 35 
 
 Building supplies 12 
 
 Tools and equipment 12 
 
 Wheelbarrow 10 
 
 Hose 6 
 
 Steelrope 4 
 
 'Primary cause of 93 back injuries. 
 
 The preceding discussion has analyzed 
 the overall back injury data for a ma- 
 jor coal company. The balance of this 
 section will provide examples of the 
 analysis of job-related injury data by 
 analyzing two of the jobs in detail. 
 In essence, this means breaking down 
 the cause and agent data for two jobs: 
 laborer and shuttle car operator. Of 
 the mining jobs, the laborer job had 
 both the highest frequency and frequency 
 rate. Table 10 shows the frequency dis- 
 tribution of causes of back injury for 
 laborers. The laborer's job consists of 
 setting posts and timbers, laying and 
 retrieving rails, unloading supplies, 
 shoveling, general cleaning activities, 
 etc. 
 
 Planks and timbers 70 
 
 Tools and equipment (timber 
 
 jacks, 21) 69 
 
 Supplies 48 
 
 Railroad ties-bars 42 
 
 Shovel-rocks 41 
 
 Cables 38 
 
 Bagged materials 28 
 
 Drums -cans 18 
 
 Wheelbarrow 11 
 
 Belts-belt drive 11 
 
 ' Primary cause of 428 back injuries. 
 
 TABLE 10. - Causes of laborer back 
 injuries 
 
 (Total cases, 158; frequency rate, 37.05) 
 
 Cause 
 
 Slip-trip 
 
 Riding in vehicle.. 
 Materials handling. 
 Push-pull 
 
 pet 
 
39 
 
 As would be expected, more than half of 
 the Injuries are the result of materials 
 handling or push-pull activities. Anoth- 
 er 18 pet are due to slips-trips, but 
 when these are analyzed further, a third 
 of them involve materials handling. The 
 remaining injuries are split between 
 shoveling and riding in vehicles. Shov- 
 eling is to some extent a variation of 
 materials handling, but having 12 pet of 
 laborer's back injuries associated with 
 riding in vehicles raises some serious 
 questions about mine vehicle design. A 
 more detailed breakdown of laborer in- 
 juries is provided in table 11 by materi- 
 als handling, slip-trip, and riding in 
 vehicle. 
 
 TABLE 11. - Analysis of activity at time 
 of laborer injury 
 
 the balance of the injuries. Again, al- 
 most one-third of the slip-trip injuries 
 involved materials handling. The high 
 percentage of vehicle-related injuries is 
 perhaps not surprising for a vehicle op- 
 erator, but it again suggests problems 
 within vehicle design, particularly as it 
 relates to occupant safety. When com- 
 pared with the estimated job exposure, 
 the high frequency of materials handling 
 injuries raises a question about the re- 
 lation among the shuttle car operator's 
 seat design, the constant forward flexed 
 posture and vibration exposure, and a 
 predisposition to lifting injuries. 
 
 TABLE 12. - Causes of shuttle car 
 operator back injuries 
 
 (Total cases, 95; frequency rate, 15.74) 
 
 Activity 
 
 Frequency | pcF 
 
 MATERIALS HANDLING 
 
 
 
 Timber, plank, railroad 
 ties 
 
 18 
 12 
 11 
 
 11 
 
 4 
 
 20 
 
 24 
 
 Shovel 
 
 Rair bars 
 
 16 
 
 14 
 
 Supplies, bagged materi- 
 als, concrete blocks.... 
 Cable 
 
 14 
 5 
 
 Other 
 
 26 
 
 SLIP-TRIP 
 
 Floor conditions... 
 Materials handling. 
 
 Using tools 
 
 Others 
 
 48 
 
 34 
 
 11 
 
 7 
 
 RIDING IN VEHICLE 
 
 
 
 Floor conditions ......... 
 
 6 
 6 
 5 
 2 
 
 32 
 
 Collision 
 
 32 
 
 Hit object 
 
 26 
 
 Derail 
 
 10 
 
 
 
 A similar analysis is provided for the 
 shuttle car operator (tables 12-13). 
 This job was selected because of its con- 
 trast to the laborer. In theory, this 
 job involves considerably less materials 
 handling and, in fact, industrial engi- 
 neering estimated that only 15 to 20 pet 
 of the job is materials handling (com- 
 pared with 40 to 45 pet for laborer) . In 
 spite of this, when push-pull is added to 
 strict materials handling, 53 pet of the 
 back injuries are accounted for. Riding 
 in vehicles accounts for 29 pet, with 
 slip/trip and shoveling accounting for 
 
 Cause 
 
 Slip-trip 
 
 Riding in vehicle. , 
 Materials handling. 
 
 Push-pull 
 
 Shoveling 
 
 pet 
 
 11 
 
 29 
 
 46 
 
 9 
 
 5 
 
 TABLE 13. - Analysis of shuttle car 
 operator activity at time of injury 
 
 Activity 
 
 Frequency | pet 
 
 MATERIALS HANDLING (INCLUDES PUSH-PULL 
 AND SHOVELING) 
 
 Timbers , 
 
 Cables , 
 
 Bagged materials, 
 
 Supplies , 
 
 Shoveling , 
 
 Wheelbarrow , 
 
 Timber j acks 
 
 Other 
 
 10 
 10 
 7 
 6 
 5 
 5 
 2 
 12 
 
 18 
 
 18 
 
 12 
 
 11 
 
 9 
 
 9 
 
 4 
 
 21 
 
 RIDING IN VEHICLE 
 
 Floor condition. 
 
 Collision 
 
 Other 
 
 20 
 5 
 3 
 
 71 
 18 
 11 
 
 SLIP-TRIP 
 
 Floor condition. . . . 
 Materials handling. 
 Other 
 
 50 
 30 
 20 
 
 A final issue of interest is the effect 
 of mine height. Table 14 presents a com- 
 parison of the frequency rates associated 
 with the four mine height categories used 
 in this study. The higher ranges were 
 
40 
 
 selected based upon ease of categoriza- 
 tion from the company's records. The 
 data should be interpreted with caution 
 since four or less mines are represented 
 in each of the first three categories. 
 The data in the first three categories 
 were pooled to determine whether there 
 
 TABLE 14. - Comparison of back injury 
 frequency rates by mine seam height 
 for one company 
 
 Mine seam height, in Frequency rate 
 
 <48 7.51 
 
 48 to 60 10.87 
 
 60 to 78 4.90 
 
 >78 16.61 
 
 CONCLUSIONS AND 
 
 This paper has provided an overview of 
 a rather massive data collection effort 
 designed to probe the circumstances sur- 
 rounding back injuries in coal mining. 
 A short paper could not do more than sum- 
 marize the subject and introduce one 
 method for analyzing the problem. It be- 
 gan by evaluating some of the convention- 
 al wisdom and opinions about back inju- 
 ries in coal mining, and established that 
 for this company, the wisdom was in con- 
 flict with the facts. The problems that 
 lead to back injuries are complex, and 
 hese results clearly suggest that the fi- 
 rst steps in solving the problem will 
 have to be thorough, quantitative analy- 
 ses of the situation and not, as has of- 
 ten been done, a reliance on conventional 
 wisdom and opinion. We cannot ever do 
 away with back injuries, but by system- 
 atically analyzing the problem, and con- 
 trolling what is done, how it is done, 
 and who does it, it should be possible to 
 achieve a significant reduction in the 
 back injury rate. 
 
 The overall pattern of back injuries 
 was analyzed, and it pointed to a number 
 of conditions as being the source of the 
 problem. The primary source was, as ex- 
 pected, materials handling. This is con- 
 sistent with similar analyses performed 
 in general industry. Additional indepth 
 analyses conducted on specific jobs also 
 identified materials handling as a major 
 problem, but these also highlighted 
 vehicle-related injuries, often the re- 
 sult of hitting bumps in the haulageway. 
 
 appeared to be differences between mines 
 in which miners work standing (>78 in) 
 and those which preclude standing (table 
 15). The rates suggest that standing is 
 more hazardous, but with only three data 
 points to compare, the differences were 
 nonsignificant. 
 
 TABLE 15. - Comparison of back injury 
 frequency rates in mines greater than 
 and less than 78 in for one company 
 
 Year 
 
 Mine height, in 
 
 
 <78 
 
 >78 
 
 1980 
 
 6.5 
 3.4 
 6.2 
 
 20.2 
 
 1981 
 
 13.7 
 
 1982 
 
 8.3 
 
 Average 
 
 5.4 
 
 14.2 
 
 RECOMMENDATIONS 
 
 as being a significant cause. Identifi- 
 cation of materials handling as a problem 
 is not a new insight. MSHA's Hershel 
 Potter stated it was a problem years ago. 
 What is new in this research is the po- 
 tential for a job-by-job breakdown of the 
 pattern of back injuries to determine 
 what approach may work on each job. The 
 other new feature of this effort will be 
 that of tying together the costs and in- 
 juries so that both frequent and costly 
 injuries can be examined. The next step 
 in this process will be application of 
 these data to the jobs studied to find 
 practical ways of modifying either job or 
 agent to reduce the risk of injury. 
 
 Identifying vehicle riding as a major 
 source of back injury suggests a number 
 of promising research directions. At 
 this point, the cause appears to be a 
 combination of forward flexed posture, 
 continual vibration exposure, and occa- 
 sional severe jarring which combined to 
 create the injuries. In addition, it ap- 
 pears they form a predisposition to lift- 
 ing injuries. Much of this relates di- 
 rectly to vehicle design and, as such, is 
 a problem that management can control. 
 
 The analyses reported here will be ex- 
 panded for use in working with company 
 engineers, supervisors, and miners to de- 
 crease the injury frequency rate. Future 
 reports will provide a description of one 
 or more innovations that have resulted in 
 the decrease of back injuries among coal 
 miners. 
 
41 
 
 TWO BACK RISKS IN MINING: LIFTING AND PUSHING AND PULLING 
 By Robert 0. Andres 1 
 
 INTRODUCTION 
 
 Mining has long had the onus of being 
 one of the most hazardous occupations for 
 the workers involved. The nature of the 
 work, is quite physical, and many of the 
 accidents are unpredictable owing to 
 falling roofs or materials. There were 
 about 40,000 disabling injuries in 1974 
 for the mining and quarrying industries 
 (11) ,2 and out of 41 industries reporting 
 to the National Safety Council, under- 
 ground coal mining had the highest fre- 
 quency rate and severity rate (35.44 dis- 
 abling injuries and 5,154 days lost per 
 1,000,000 employee-hours, respectively). 
 However, not all of these injuries are 
 due to falls of mine roofs; slips and 
 falls on the same level and materials 
 handling showed up as causes of injury 
 also in mining (14). Broken down on the 
 
 basis of part of the body injured, from 
 33 to 42 pet of the injuries reported 
 (from underground to open-pit mining) 
 were to the trunk. Between 33 and 44 pet 
 of the total injuries were strains and 
 sprains due to overexertion. These find- 
 ings for the mining industry echo the 
 statistics for the workplace in general, 
 where 27 pet of all injuries occurred to 
 the trunk, resulting in 38 pet of the to- 
 tal workmen's compensation in 1974 (11). 
 
 Recent research has been concentrating 
 on the risks of back injury during manual 
 materials handling, and also during dy- 
 namic pushing-pulling. Some of this re- 
 search and its methodologies will be de- 
 scribed briefly, and example applications 
 to the mining industry will be presented. 
 
 BIOMECHANICS OF THE LOW BACK 
 
 Epidemiological studies have shown that 
 the low back is a structural weak link in 
 the musculoskeletal system. Approximate- 
 ly 80 pet of back injuries occur in the 
 L4-L5 or Lj-S^ region of the spine (,1) • 
 A large body of evidence indicates that 
 many of these back injuries result from 
 excessive compressive forces on the L5~S, 
 disk (_2, 9-10). Cadaver studies have 
 shown that compressive forces in excess 
 of 1,500 lb result in L^-S , disk verte- 
 brae failures in cadavers of males 40 yr 
 old or younger (_6, 13). This load level 
 decreases with age, and females have 
 an even lower tolerance. Low-back pain 
 
 ''Assistant research scientist. Center 
 for Ergonomics, University of Michigan, 
 Ann Arbor, MI. 
 
 ^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this paper. 
 
 incidents have been shown to increase 
 with predicted compressive forces on the 
 L5-S , disk (_5) , so the biomechanics of 
 the low-back region will be examined in 
 more detail. 
 
 Figure 1 is a free body diagram of the 
 torso showing the different forces that 
 contribute to the compressive force on 
 the L5-S , disk. Only the abdominal force 
 exerted on the diaphragm counteracts the 
 forces due to the upper body mass, the 
 load in the hands, and the forces of the 
 trunk extensor muscles (erector spinas). 
 Static analysis of this situation solves 
 for the L5SO, compressive force; this 
 static model has been applied to load 
 handling by several researchers (^~^. ]_) • 
 Given the body posture, the weight of the 
 load in the hands, and the position of 
 the hands, these models can predict the 
 compressive force on the L5-S ^ disk. 
 
42 
 
 NIOSH WORK PRACTICES GUIDE 
 
 One culmination of the biomechanical 
 approach to studying low-back injuries 
 was the development of the "Work. Prac- 
 tices Guide for Manual Lifting" by NIOSH 
 ( 13 ) in 1981. This document combines 
 epidemiological, biomechanical, physio- 
 logical, and psychophysical research re- 
 sults to make recommendations about lift- 
 ing. This amalgamated approach does not 
 pretend to be the final word on lifting 
 techniques; in fact, the major recommen- 
 dation is that much more research in 
 all of these areas is necessary, but 
 there are several interesting analyses 
 that can and should be applied to jobs as 
 stressful as those found in the mining 
 industry. 
 
 Two different lifting limits have been 
 defined in the guide: The maximal per- 
 missible limit (MPL) above which load the 
 lift is so hazardous that only a few 
 people could perform it safely, and the 
 action limit (AL) above which weaker in- 
 dividuals are at risk, but most people 
 can safely perform the lift. When ex- 
 ceeded, the MPL dictates that job re- 
 design must be performed, whereas exceed- 
 ing the AL requires aggressive selection 
 and training procedures to protect those 
 at risk. Figure 2 shows the maximum 
 
 weight that can be lifted (in a sym- 
 metric, sagittal plane, two-handed lift) 
 infrequently (once every 5 min) from 
 floor-to-knuckle height as a function of 
 the horizontal location of the load. The 
 criteria that defined the MPL include (1) 
 epidemiology, musculoskeletal injury and 
 severity rates increase in populations 
 performing work above this level; (2) 
 biomechanics, conditions above the MPL 
 result in L^-S ^ compressive forces above 
 1,400 lb, which is not tolerable to most 
 workers; (3) physiology, metabolic rates 
 would exceed 5.0 kcal/min for most indi- 
 viduals above the MPL; and (4) psycho- 
 physics, only 25 pet of male and less 
 than 1 pet of female workers have the 
 muscle strength to work above the MPL. 
 These same criteria, applied for the AL, 
 show (1) only a moderate increase in in- 
 jury and severity rates, (2) a 770-lb 
 compressive force on the L5~S ^ disk, 
 which can be tolerated by most young, 
 healthy workers, (3) metabolic rates ex- 
 ceeding 3.5 kcal/min for most people 
 working above the AL, and (4) 99 pet of 
 men and over 75 pet of women could lift 
 loads described by the AL. 
 
 The following algebraic formula was de- 
 rived to calculate the AL: 
 
 Al(lb) = 90(6/H)(1-0.01|V-30|)(0.7+3/D(1-F/Fmax) 
 
 where H = horizontal location forward of midpoint between ankles at lift origin, or 
 inches, 
 
 V = vertical location at lift origin, inches, 
 
 D = vertical travel distance between lift origin and destination, inches, 
 
 F = average lift frequency, lifts per minutes, 
 
 F^^^^ = maximum frequency which can be sustained (table I), 
 
 then MPL = 3 (AL). 
 
 See reference 13 for the limits of application to a mining situation will be 
 these variables. With this brief in- presented, 
 troduction to the guide, an example 
 
EXAMPLE APPLICATION 
 
 Figure 3 schematically represents a 
 situation where a miner lifts rock, or 
 coal from the mine floor to a waiting 
 
 43 
 
 cart. Assuming this takes place fre- 
 quently throughout an 8-hr shift, Fn^^^=12 
 (table 1). If the lift is performed once 
 per minute (F=l), the results for just 
 the vertical portion of the lift are 
 
 AL(lb) = 40(6/18)(l-0.004|7.6-75|)(0.7+7.5/20)(l-l/12) 
 = 40(0. 333)(1.26)(1.075)(0. 917) = 16.54 lb 
 MPL = 50 lb 
 
 TABLE 1. - Maximum sustained lifting 
 frequency 
 
 Period, h 
 
 Average vertical location, in 
 
 
 >30, standing 
 
 <30, stooped 
 
 1 
 
 18 
 15 
 
 15 
 
 8 
 
 12 
 
 Therefore, any load material smaller 
 than 16 lb should not overly stress 
 any worker, whereas loads between 16 to 
 50 lb should only be handled by stronger 
 
 workers with care, and loads above 50 lb 
 should not be lifted. The control mea- 
 sure in this situation would be breaking 
 the rock up into pieces smaller than 16 
 lb. If this lift were performed up to 
 five times a minute, the AL would be 
 10 lb while the MPL would be 30 lb. 
 Although few actual tasks are as simple 
 to analyze as this one, this type of 
 analysis is obviously quite easy to per- 
 form as a first attempt to control job 
 stresses. 
 
 CART PUSHING AND PULLING 
 
 In some mining operations the mined 
 material is loaded on carts, sometimes on 
 rails, which are then manully manuevered. 
 This situation can lead not only to mus- 
 culoskeletal strains or sprains, but also 
 to slips or falls owing to inadequate co- 
 efficient of friction parameters at the 
 shoe-floor interface. A biodynamic model 
 has been developed i8) that predicts the 
 risk of low back injury and the risk of 
 foot slip. This model is not restricted 
 to static push-pull tasks, but only oper- 
 ates in the sagittal plane. The inputs 
 to the computer model are subject an- 
 thropometry, body joint motion data, cart 
 handle height, and the forces exerted by 
 the hands on the cart handles. 
 
 Figure 4 is an illustration of the lab- 
 oratory equipment used to gather the mod- 
 el inputs. The model then calculates the 
 reactive forces and moments at each 
 joint, the L^-S^ compressive load, and 
 the required coefficient of friction to 
 prevent foot slip. Although this model 
 is still being refined and validated in 
 the laboratory, it will be applied exten- 
 sively in the field. Example predictions 
 
 from the model are shown in figures 5 and 
 6. Figure 5 illustrates the predicted 
 Lg-S^ compressive forces for an example 
 push-pull situation, while figure 6 is an 
 example of predicted coefficient of fric- 
 tion requirements at the shoe-floor in- 
 terface during a push. 
 
 Field data taken with portable force 
 measuring handles and high-speed movies 
 will be run through the biodynamic model 
 to obtain output similar to figures 5 and 
 6. From this analysis the following rec- 
 ommendations can be made: (1) The maxi- 
 mum allowable hand forces, which relate 
 to cart loading and resistance; (2) the 
 required coefficient of friction, which 
 relates to the shoe and floor materials, 
 shoe tread design, floor surface prepara- 
 tion, and floor maintenance; (3) cart 
 handle placement to minimize back injury 
 risk (this changes for pushing versus 
 pulling); and (4) the required strength 
 of the worker performing the task. Al- 
 though this model is still being refined, 
 it represents another tool that should be 
 used to analyze the stresses of physical 
 work. 
 
44 
 
 SUMMARY AND CONCLUSIONS 
 
 There are several recently developed 
 analytical tools available for study- 
 ing working situations, such as mining, 
 that have high musculoskeletal injury 
 rates and severity rates. Only two tech- 
 niques of predicting overexertion inju- 
 ries to the low back have been discussed 
 in this paper, along with some example 
 
 applications to mining. As research pro- 
 gresses in ergonomics, more use must be 
 made of its results by the industries 
 that can benefit most from its applica- 
 tions; hence, a unique possibility for 
 cooperation among academia, management, 
 and labor exists and should be pursued. 
 
 REFERENCES 
 
 1. Armstrong, J. R. Lumbar Disk Le- 
 sions. Williams and Wilkins, Baltimore, 
 MD, 1965, pp. 230-239. 
 
 2. Chaffin, D. B. A Computerized Bio- 
 mechanical Model: Development of and Use 
 in Studying Gross Body Actions. J. Bio- 
 mechanics, V. 2, Oct. 1969, pp. 429-441. 
 
 3. . On the Validity of Biome- 
 
 chanical Models of the Low Back for 
 Weight Lifting Analysis. Pres. at the 
 Winter Ann. Meeting of ASME, Houston, TX, 
 Nov. 30-Dec. 4, 1975; available upon re- 
 quest from R. 0. Andres, Univ. MI, Ann 
 Arbor, MI. 
 
 8. Lee, K. S. Biomechanical Modelling 
 of Cart Pushing and Pulling. Ph.D. Dis- 
 sertation in Industrial and Operations 
 Engineering, Univ. MI, Ann Arbor, MI, 
 1982. 
 
 9. Martin, J. B., and D. B. Chaffin. 
 Biomechanical Computerized Simulation 
 of Human Strength in Sagittal-Plane 
 Activities. AIEE Trans., v. 4, 1972, 
 pp. 19-28. 
 
 10. Morris, J. M. , D. B. Lucas, and 
 B. Bresler. Role of the Trunk in Stabil- 
 ity of the Spine. J. Bone Joint Surg. , 
 V. 43A, 1961, pp. 327-351. 
 
 4. Chaffin, D. B., and W. H. Baker. 
 Biomechanical Model for Analysis of Sym- 
 metric Sagittal Plane Lifting. AIIE 
 Trans., v. 2, Mar. 1970, pp. 16-27. 
 
 5. Chaffin, D. B., and K. S. Park. A 
 Longitudinal Study of Low Back Pain as 
 Associated With Occupational Lifting Fac- 
 tors. AM. Ind. Hyg. Assoc. J., v. 34, 
 1973, pp. 513-525. 
 
 6. Evans, F. G. , and H. R. Lissner. 
 Biomechanical Studies on the Lumbar Spine 
 and Pelvis. J. Bone Joint Surg. , v. 41A, 
 1959, pp. 218-290. 
 
 7. Garg, A., and D. B. Chaffin. A Bi- 
 omechanical Computerized Simulation of 
 Human Strength. AIIE Trans., v. 7, 1975, 
 pp. 1-15. 
 
 11. National Safety Council Accident 
 Facts. Chicago, IL, 1975, pp. 23-37. 
 
 12. Sonada, T. Studies on the Com- 
 pression, Tension, and Torsion Strength 
 of the Human Vertebral Column. J. Kyoto 
 Prefect Med. Univ., v. 71, 1962, pp. 659- 
 702. 
 
 13. U.S. Department of Health and Hu- 
 man Services Work Practices Guide for 
 Manual Lifting. NIOSH Pub. 81-122, 1981, 
 183 pp.; NTIS: PB 82-178-948. 
 
 14. U.S. Mine Enforcement and Safety 
 Administration. Injury Experience in the 
 Nonmetallic Mineral Industries (Except 
 Stone and Coal), 1970-71. MESA IR 1014, 
 1975, 106 pp. 
 
45 
 
 'abdomen-. 
 
 e — *-, 
 
 FmuscI 
 
 ■compression-TY /pg^g^' 
 
 Center of gravity of body 
 weight (BW) above 
 lumbosacral joint 
 
 Push or pul 
 force 
 
 Handle attached 
 to 3-axis load 
 
 FIGURE 1. . Free body diagram of the torso, showing variables used to calculate the c 
 
 sive force at Lj-S ,. 
 
 ompres- 
 
 200 
 
 150- 
 
 _i 100- 
 
 X 
 
 a 
 
 UJ 
 
 5 
 
 10 20 30 40 
 
 HORIZONTAL LOCATION OF LOAD, In 
 
 FIGURE 2, - Maximum weight versus horizontal 
 location for infrequent lifts from floor-to-knuckle 
 height (13), 
 
 KEY 
 V = 3in 
 H = I8in 
 D = 20in 
 F = I lift per minute 
 
 FIGURE 3, - Schematic representation of miner 
 lifting material onto a cart. 
 
46 
 
 Amplifier 
 
 FIGURE 4, - Laboratory setup used to collect data 
 for the biodynamic push-pull model. 
 
 en 
 
 Q 
 
 < 
 o 
 
 _l 
 
 LLl 
 
 > 
 
 CO 
 
 (n 
 
 UJ 
 
 a: 
 a. 
 
 O 
 
 o 
 
 ,000 
 
 500 
 
 KEY 
 A= Push V, 32 In 
 • = Pull V, 32 in 
 
 20 40 60 80 
 
 HAND FORCES, lb 
 
 100 
 
 120 
 
 FIGURE 5. - Predicted L5-S, compressive 
 forces (8). 
 
 20 40 60 80 100 120 140 160 180 200 
 TIME DURING STEP CYCLE, ms 
 
 FIGURE 6. - Predicted required coefficient of fric- 
 tion for one foot at the shoe-floor interface during a 
 pushing task. 
 
47 
 
 FIELD TESTING OF WORKERS INVOLVED IN MATERIAL HANDLING 
 By Karl H. E. Kroemer' 
 
 INTRODUCTION 
 
 Many industrial jobs require the worker 
 to manipulate objects, position loads, 
 and perform other physical activities 
 that are usually understood as "lifting." 
 The physical efforts involved in lifting 
 often overload the physical capability of 
 the people performing them, leading to 
 very large numbers of job-related inju- 
 ries and to very high costs in terms of 
 lost time, compensation payments, and re- 
 training of new personnel. Thus, indus- 
 try is trying to either select people ac- 
 cording to their strength, to train them 
 so that they are able to perform stress- 
 ful jobs, or to limit the loads to be 
 moved by workers so that they will not be 
 overstressed. For screening, reliable 
 and valid tests are needed that assess 
 the capability of an individual to manip- 
 ulate loads. Relatedly, job requirements 
 must be known regarding the type and mag- 
 nitude of loads to be manipulated. Both 
 tasks are interrelated because job re- 
 quirements should match the operator's 
 capability to perform the jobs, and vice 
 verse. 
 
 Sponsored and coordinated by NIOSH, 
 several researchers cooperated to deter- 
 mine the conditions that would either 
 constitute safe or hazardous lifting re- 
 quirements. A summary of the research 
 and recommendations derived from it were 
 published in the 1981 NIOSH "Work Prac- 
 tices Guide for Manual Lifting" (10).^ 
 
 The guide utilizes weight to be lifted 
 as the primary descriptor of the job re- 
 quirements, but modifies this criterion 
 by including the start and end points of 
 the path of the lift, and by the frequen- 
 cy of lifting. These job requirements 
 then, ideally, are matched to capabili- 
 ties of the operators, or vice versa. 
 Operator capabilities can be established 
 using physiological, psychophysical, and 
 biomechanical response variables. Among 
 biomechanical test procedures, until re- 
 cently only static tests were at hand. 
 While well established and tested, these 
 procedures obviously do not represent the 
 dynamic requirements of industrial lift- 
 ing, where work is usually performed with 
 body and object in motion. 
 
 Psychophysical testing of a subject's 
 dynamic capability for lifting was pre- 
 viously developed in the laboratories 
 of Liberty Mutual Insurance Co. and at 
 Texas Tech University. NIOSH sponsored 
 research for the development of an 
 industrial dynamic testing technique 
 at Virginia Polytechnic Institute and 
 State University. This work resulted in 
 a new testing procedure and technique, 
 called LIFTEST. This dynamic technique 
 promises to be more reliable than static 
 strength testing and appears to be more 
 indicative of a person's actual lifting 
 capability. 
 
 FITTING THE WORKER TO THE JOB VERSUS FITTING THE JOB TO THE WORKER 
 
 Manual material handlings produces the 
 single largest percentage of compensable 
 work injury in U.S. industry, constitut- 
 ing today one-fourth to one-third of all 
 
 ^Director, Ergonomics Research Insti- 
 tute, Inc., Blacksburg, VA. 
 
 ^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this paper. 
 
 injuries. The cost to U.S. business is 
 estimated" between $4 and $20 billion an- 
 nually (_9, 10). Suffering of the injured 
 and of their families cannot be expressed 
 in dollar figures. 
 
 -^This is often called lifting, although 
 in its strict sense lifting refers exclu- 
 sively to elevating an object from a low- 
 er level to a higher one. 
 
48 
 
 The following three major avenues exist 
 to reduce the frequency and severity of 
 these injuries: 
 
 1. Screening of workers for their 
 physical abilities to perform material 
 handling. 
 
 2. Training of workers to perform 
 material handling in a manner that avoids 
 accidents. 
 
 3. Designing work task and work equip- 
 ment so that workers will not be strained 
 excessively by materials handling. 
 
 This presentation concentrates on 
 screening of workers for their physical 
 capabilities to handle material at work 
 without overexertion. 
 
 After standard medical examinations 
 were found ineffective for screening, 
 more recently static muscular strength 
 tests have been advocated (10). These 
 assess isometric muscular strength of the 
 human in discrete "frozen" body posi- 
 tions, primarily by measuring leg force, 
 back force, and arm force (2). In com- 
 paring these scores via a biomechanical 
 model of the human body with job require- 
 ments, or injury data in general, it was 
 
 found that isometrically "stronger" work- 
 ers have fewer and/or less severe inju- 
 ries than isometrically "weaker" workers 
 (iO). 
 
 The effectiveness of a screening tech- 
 nique depends, to a large degree, on its 
 ability to mimic the actual work require- 
 ments that may overexert human capabili- 
 ties. Static strength testing suffers in 
 particular from the fact that it is done 
 with the worker being immobile while ac- 
 tual material handling usually involves 
 motion. 
 
 Because of the apparent deficiency in 
 the validity of static testing, NIOSH 
 sponsored research (under contract 210- 
 79-0041) to develop a dynamic technique 
 to test individual capability for lift- 
 ing. This work resulted in a testing 
 procedure, called LIFTEST, that was found 
 to be highly reliable, as well as quick 
 and simple to administer, in laboratory 
 experiments (6^). While LIFTEST is ap- 
 parently much more similar to actual 
 material handling than static strength 
 testing, its validity and effectiveness 
 in screening workers for their capability 
 to perform material handling tasks with- 
 out injuries has yet to be assessed in a 
 systematic manner. 
 
 INDIVIDUAL CAPABILITIES SHOULD EXCEED JOB DEMANDS 
 
 The premise of physical screening tech- 
 niques is that human bodily capabilities 
 will be measured and compared with re- 
 lated job requirements; the more tested 
 capabilities exceed job demands, the 
 "safer" the person-job match. In mate- 
 rial handling, many of the critical in- 
 juries are related to the musculoskeletal 
 system, particularly to the L5-S , region 
 of the spinal column. As the guide for 
 manual lifting indicates, there is an 
 
 epidemiological relationship between in- 
 dividual "strength" (as measured physio- 
 logically, biomechanically , or psycho- 
 physically) and job demands, with strong- 
 er persons being less susceptible to 
 injuries than their weaker cohorts. Even 
 other injuries related to materials han- 
 dling such as lesions, abrasions, etc., 
 show correspondence with the strength 
 criterion (10). 
 
 ASSESSMENT OF INDIVIDUAL LIFT CAPABILITY 
 
 Current static biomechanical models of 
 the human performing material handling 
 include anthropometry, isometric muscle 
 force (or torque) capabilities, the abil- 
 ity to withstand compression forces in 
 the lower part of the lumbar spine, body 
 
 posture descriptors, and work require- 
 ments (J_). Unfortunately, the key in- 
 gredient, isometric muscle strength capa- 
 bility, is somewhat unrealistic because 
 lifting and other material handling ac- 
 tivities are performed with body and 
 
49 
 
 load in motion and not in a static "fro- 
 zen" condition. This discrepancy between 
 static measurements and dynamic job re- 
 quirements may explain why correlations 
 between static strength and job perform- 
 ance capabilities are usually unsatisfac- 
 tory for predictive-preventive purposes, 
 being in the neighborhood of only 0.5 
 
 a). 
 
 Researchers at the University of Michi- 
 gan and at Texas Tech University devel- 
 oped static muscle strength tests and re- 
 lated their outcomes with incidences of 
 
 physical overexertion in industries re- 
 quiring material handling O, 8^). Both 
 groups found that isometrically weaker 
 persons suffered from a larger number of 
 overexertion injuries than stronger sub- 
 jects. However, some of the static 
 strength tests showed practically no 
 relationships to the probabilities of 
 overexertion injuries. For example, of 
 nine isometric strength tests applied by 
 Keyserling (_5 ) , only four showed signifi- 
 cant relations to the occurrences of mus- 
 culoskeletal problems. 
 
 LIFTEST 
 
 Recognizing the problems of "unrealis- 
 tic" static testing, NIOSH sponsored work 
 to develop a dynamic testing procedure 
 suitable for field application. This 
 work was performed over a period of 2-yr, 
 and resulted in the new technique called 
 LIFTEST (6^). 
 
 LIFTEST equipment consists essentially 
 of a carriage that a person moves up and 
 down within vertical guardrails. Varia- 
 ble weights are attached to the rear part 
 of the carriage in such a manner that the 
 subject is unable to see them. The per- 
 son grasps the handles protruding from 
 the carriage near floor height and lifts 
 them, with carriage and weights attached, 
 to her or his individual overhead reach 
 height. Using a suitable sequence, the 
 maximum weight that the individual can 
 lift to overhead reach is determined 
 within 2 or 3 min. In test-retest relia- 
 bility experiments performed in the lab- 
 oratory, 39 subjects could lift, on the 
 average, 59.3 lb to overhead reach, with 
 a standard deviation of 22.7 lb. This 
 range indicates that the strength capa- 
 bilities of the subjects employed were 
 rather different. However, the subjects, 
 whether weak or strong, showed a con- 
 sistent low intra-individual variabil- 
 ity of their individual scores in repeat- 
 ed tests. The average coefficient of 
 variation was only 3.5 pet, compared 
 with 13 pet in isometric strength tests 
 (6). In rather similar "Factor X" tests 
 with almost 600 subjects, male and fe- 
 male, the U.S. Air Force also found that 
 
 such dynamic lift tests are much more 
 reliable (i.e. , less variable in repeat- 
 ed tests) than isometric muscle strength 
 measurements. 4 Relatedly, isokinetic 
 (i.e., constant speed) strength testing 
 also showed relatively low correlations 
 with isometric muscle strength testing 
 (4^). This strongly supports the notion 
 that the dynamic LIFTEST can be used re- 
 liably to assess lift capability. What 
 was not measured (and not intended to be 
 measured) in the NIOSH-sponsored labor- 
 atory research was the validity of the 
 test, that is, its relationship to actual 
 lifting performance in industry. While 
 having obvious "face-validity," the prac- 
 tical effectiveness of the LIFTEST pro- 
 cedure needs to be established in field 
 tests. Interestingly enough, the U.S. 
 Air Force used simulated "actual" lift 
 tasks to validate their dynamic "Factor 
 X" testing. The correlation between lift 
 test results, and actual lift performance 
 was about 0.9.5 a correlation of 0.75 
 between isokinetic and actual lifting 
 capability has been reported (4^) . These 
 results strongly support the expectation 
 that the LIFTEST procedure will be an ef- 
 ficient predictor of lifting capability 
 on the job. 
 
 According to the premise discussed 
 above, the ratio "strength available to 
 strength required" would indicate the 
 
 '^McDaniel, J. W. Personal Communica- 
 tion, Jan. 24, 1983. 
 ^See footnote 4. 
 
50 
 
 probability of an overexertion injury; 
 a high ratio would make this probabil- 
 ity small, a ratio close to unity would 
 indicate a high probability. Used as 
 a screening technique, one would avoid 
 placing persons with a low ratio in jobs 
 requiring such strength exertion, or 
 
 reduce job requirements by administra- 
 tive or engineering intervention. Per- 
 sons with a high ratio could be employed 
 in jobs requiring manual material han- 
 dling with little danger of overexertion 
 injuries. 
 
 ASSESSMENT OF JOB LIFTING REQUIREMENTS 
 
 The NIOSH guide provides a standardized 
 procedure to assess the job requirements 
 involved in material lifting tasks. The 
 guide ( 10 , p. 124) establishes three 
 major categories of hazards in material 
 handling. They are divided by the so- 
 called "action limit" and the "maximum 
 permissible limit." Below the action 
 limit, no hazard to the individual is ex- 
 pected that would require engineering 
 or administrative interaction. A "gray" 
 zone exists between the action lim- 
 it and the maximum permissible limit 
 where suitable intervention methods 
 are needed. These might mean worker 
 screening-selection methods, and/or might 
 involve engineering measures to reduce 
 the worker's lift effort. Requirements 
 above the maximum permissible limit are 
 unacceptable. 
 
 The guide sets the maximum permissible 
 limit numerically to be three times larg- 
 er than the action limit. It appears 
 reasonable to divide this zone between 
 action and maximum permissible limits in- 
 to two zones by doubling the action limit 
 values. Hence, work requirements that 
 fall below the doubled action limit would 
 be less hazardous than those conditions 
 falling between twice the action limit 
 
 and maximum permissible limit values. 
 Using such subdivision, one can cate- 
 gorize job demands in the following 
 four areas: below action limit, between 
 single- and double-action limit, between 
 double-action limit and maximum permissi- 
 ble limit, and above maximum permissible 
 limit. 
 
 According to the guide ( 10 , p. 126) , 
 the following job variables primarily 
 determine the job requirements: the ini- 
 tial starting point of the load, the 
 end point of the lifting path, and the 
 frequency of lifts per time unit per- 
 formed. The individual contributions of 
 these variables are expressed by an alge- 
 braic formula in the guide ( 10 , p. 126). 
 Start and end point are described by the 
 height above the floor upon which the 
 worker stands, and by the vertical dis- 
 tance away from the body of the worker. 
 The frequency of lift is compared with a 
 maximum frequency deemed suitable. The 
 numerical values for these parameters are 
 inserted into the formula given in the 
 guide. Furthermore, the guide describes 
 a measurement technique to determine the 
 actual lift requirements at any given 
 workplace. 
 
 COMPARING WORKER CAPABILITIES TO JOB REQUIREMENTS 
 
 Whereas the NIOSH guide provides a 
 standard approach to establish job re- 
 quirements, the LIFTEST procedure pro- 
 vides an equally convenient method to de- 
 termine related physical capabilities of 
 the worker. The LIFTEST regimen provides 
 for a minimum load of 25 lb, and a maxi- 
 mum load of 100 lb to be employed for the 
 establishment of overhead capability 
 scores. With test weight increments of 5 
 lbs used, 18 different lift scores can be 
 obtained, ranging from below 25 lb, at 25 
 
 lb increasing in steps of 5 lb to 100 lb, 
 to exceeding 100 lb. (The 5-lb increment 
 values can be combined to larger units, 
 such as 10 lb, in order 
 number of lift capability 
 convenient. ) 
 
 to reduce the 
 assessments as 
 
 In summary, the guide provides a stan- 
 dardized procedure to assess lift re- 
 quirements imposed by the job. LIFTEST 
 provides a reliable procedure to assess 
 dynamic individual lift capabilities. 
 
51 
 
 LIFTEST PROCEDURE FIELD STUDIES 
 
 The general aim of a field study being 
 organized by the author is to assess the 
 effectiveness of the LIFTEST procedure as 
 a screening technique for reducing sever- 
 ity and frequency of overexertion inju- 
 ries resulting from manual material move- 
 ment, particularly lifting. 
 
 The specific aims of this study are 
 
 2. Monitor overexertion and other re- 
 lated injury events of these workers over 
 a 3-yr period. 
 
 3. Determine 
 needed. 
 
 job lift strains, 
 
 4. Compare injury statistics with per- 
 formance in LIFTESTs. 
 
 1. Measure individual lifting capabil- 
 ities, via the LIFTEST procedure, approx- 
 imately 15,000 workers doing material 
 handling. 
 
 5. Assess the effectiveness of the 
 LIFTEST procedure as a screening tech- 
 nique based on the results of aims 1 
 through 4. 
 
 METHODS 
 
 Several large industries in Virginia, 
 North Carolina, and Tennessee have con- 
 sented to participate in this study. 
 Others are invited to participate. 
 
 The currently participating industries 
 employ about 50,000 hourly paid persons. 
 Of these workers, approximately 30 pet 
 have jobs that include material handling. 
 If these 15,000 workers have a related 
 accident-injury rate during the 3-yr re- 
 search period of approximately 10 pet 
 (5, 10), approximately 1,500 cases would 
 be present. Even if a dropout rate of 
 one-third (which would be very high in- 
 deed) existed in the subject population, 
 approximately 1,000 cases present in the 
 study would constitute a solid statisti- 
 cal basis. 
 
 In order to establish the effectivenss 
 of the LIFTEST procedure, the following 
 steps will be taken: 
 
 1 . Measure individual lifting capabil- 
 ities of approximately 15,000 workers 
 involved in material handling . The co- 
 operating industries will identify, in- 
 ternally, in accordance with existing 
 management-labor practices and agree- 
 ments, jobs with material handling re- 
 quirements and the persons either incum- 
 bent in the jobs, being transferred to 
 them, or to be hired for them. These 
 persons will be measured, usually in con- 
 junction with a routine physical examina- 
 tion, in their LIFTEST performance by the 
 companies' medical staff. In order to 
 
 ensure uniformness and consistency in the 
 application of the LIFTEST procedure, the 
 initial equipment setup and training of 
 the staff applying the tests will be pro- 
 vided by the author and his team. 
 
 Test results will become part of the 
 medical record kept by the industries in 
 accordance with their existing safeguard- 
 ing practices. 
 
 2. Monitor over exe rtion and other re- 
 lated injuries of workers over a 3-yr 
 period. Participating industries will 
 monitor injuries related to material han- 
 dling according to the industry-estab- 
 lished practices. This assures that ano- 
 nymity and privacy of the worker rec- 
 ords remain intact, such as they would be 
 without this investigation. 
 
 3. Determine job lift requirements. 
 The author and his team will, in coopera- 
 tion with industry personnel, and in ac- 
 cordance with local management-labor 
 practices, determine the actual lifting 
 requirements of jobs that have a poten- 
 tial for, or a record of, lifting-related 
 overexertions. This will be done accord- 
 ing to reference 10. 
 
 The assessment of job requirements will 
 be independent from the person actually 
 occupying the job. Hence, personal rec- 
 ords of the worker will not be provided 
 to the investigators but will remain in 
 custody of the industry. 
 
52 
 
 4. Compare Injury statistics with 
 LIFTEST performance . The participating 
 companies will compare accident severity 
 and frequency, according to ANSI and OSHA 
 standards, with performance on LIFTEST. 
 Where the accident circumstances are not 
 obvious, the industry will cooperate with 
 the investigators in the determination of 
 job requirements prevailing at the injury 
 time (step 3). With the four categories 
 of NIOSH-def ined job requirements and 18 
 LIFTEST procedure-performance steps, in- 
 cidents can be recorded on a 4 by 18 
 matrix. (If required, the NIOSH job re- 
 quirement categories can be further sub- 
 divided and/or the number of LIFTEST 
 performance score categories be reduced, 
 as described above.). Only anonymous 
 information regarding incidence and test 
 performance will be received by the 
 investigators. 
 
 Establish 
 
 effectiveness of the 
 
 LIFTEST procedure as a screening tech- 
 nique . Based on the data collected in 
 steps 1 through 4, correlations between 
 LIFTEST performance and injuries will be 
 established. In a first step, LIFTEST 
 performance will be compared with injury 
 severity and frequency, following common 
 practice in industrial and injury statis- 
 tics. In this case, the actual job re- 
 quirements are not considered in detail. 
 As a second step, detailed comparison of 
 job requirements with LIFTEST performance 
 will be done, based on the results of the 
 specific job requirement assessments. 
 This will identify correlations between 
 general and specific job requirements 
 (such as lift frequency, initial position 
 of the load, final position of the load, 
 etc.) and LIFTEST performance. 
 
 STATISTICS 
 
 The statistical procedures are simple 
 and straightforward, using the industry- 
 common ANSI Z16 technique. This facili- 
 tates the cooperation with industry. 
 
 and 
 
 Oj = observed number of inci- 
 dents in category i, 
 
 i=l, 2, 3, ...m. 
 
 As in previous experiments (_5) , the 
 following chi-square formula to test the 
 significance of differences between inci- 
 dent rates and test performance will also 
 be used. 
 
 The values of Ej are computed with the 
 following equation: 
 
 E, =|t^«r. 
 
 (2) 
 
 2 = ? (Ej - Qj)^ 
 
 Xm-1 
 
 i=l E, 
 
 (1) 
 
 where Xm-1 = test statistic with (m-1) 
 degree of freedom, 
 
 m = number of LIFTEST score 
 categories being 
 compared. 
 
 where H| = hours of exposure in 
 category i, 
 
 H^ = total hours of exposure 
 across all categories, 
 
 or 0^ = total number of observed 
 incidents across all 
 categories. 
 
 Ej = expected number of inci- 
 dents in category i, 
 based on exposure, 
 
CONCLUSION 
 
 53 
 
 While the basic solution is to design 
 jobs to fit the worker, training and, in 
 particular, selection of individuals for 
 safe material handling are also indispen- 
 sable. Regarding screening, the testing 
 should be "realistic," that is, represent 
 
 actual job demands. Dynamic tests appear 
 to be more suitable than static muscle 
 strength testing. Procedures to develop 
 and apply such dynamic testing are at 
 hand. 
 
 REFERENCES 
 
 1. Ayoub, M. M. , A. Mital, S. S. 
 Asfour, and N. J. Bethea. Review, Evalu- 
 ation, and Comparison of Models for Pre- 
 dicting Lifting Capacity. Human Factors, 
 v. 22, No. 3, 1980, pp. 257-269. 
 
 2. Chaffin, D. B. Functional Assess- 
 ment for Heavy Physical Labor. Occupa- 
 tional Health and Safety, v. 50, No. 1, 
 1981, pp. 24, 27, 32, 64. 
 
 3. Chaffin, D. B. , G. D. Herrin, W. M. 
 Keyserling, and J. A. Foulke. Pre- 
 Employment Strength Testing in Selecting 
 Workers for Materials Handling Jobs. 
 DHEW Rept. 77-163, 188 pp.; NTIS PB- 
 298-677. 
 
 4. Kamon, E., D. Kiser, and J. L. 
 Pytel. Dynamic and Static Lifting Capac- 
 ity and Muscular Strength of Steelmill 
 Workers. Am. Ind. Hyg. Assoc. J. , v. 43, 
 No. 11, 1982, pp. 853-857. 
 
 5. Keyserling, W. M. , G. D. Herrin, 
 D. B. Chaffin, T. J. Armstrong, and 
 M. L. Foss. Establishing an Industrial 
 Strength Testing Program. Am. Ind. Hyg. 
 Assoc. J., V. 41, No. 10, 1980, pp. 730- 
 736. 
 
 6. Kroemer, K. H. E. Development of 
 "LIFTEST," A Dynamic Technique to Assess 
 
 the Individual Capability to Lift Materi- 
 al. Final Report, NIOSH contract 210- 
 79-0041. Ergonomics Laboratory, VA Poly- 
 technic Inst, and State Univ. , Febru- 
 ary 26, 1982, available upon request from 
 K. H. E. Kroemer, Ergonomics Research In- 
 stitute, Blacksburg, VA. 
 
 7. Mital, A., and M. M. Ayoub. Model- 
 ing of Isometric Strength and Lifting 
 Capacity. Human Factors, v. 22, No. 3, 
 
 1980, pp. 285-290. 
 
 8. Mital, A., M. M. Ayoub, S. S. 
 Asfour, and J. J. Bethea. Relationship 
 Between Lifting Capacity and Injury 
 in Occupations Requiring Lifting. Paper 
 in Proceedings, Annual Meeting of the 
 Human Factors Society (Detroit, MI, 
 Oct. 16-19, 1978). Santa Monica, CA, 
 pp. 469-473. 
 
 9. Nordby, E. J. Epidemiology and 
 Diagnosis in Low Back Injury. Occupa- 
 tional Health and Safety, v. 50, No. 1, 
 
 1981, pp. 38-42. 
 
 10. U.S. Department of Health and Hu- 
 man Services. Work Practices Guide for 
 Manual Lifting. NIOSH Pub. 81-122, 183 
 pp.; NTIS PB 82-178-948. 
 
54 
 
 LIFTING CAPACITY DETERMINATION 
 By M. M. Ayoub.l J. L. Selan,2 w. Karwowski,3 and H. P. R. Rao4 
 
 ABSTRACT 
 
 Given the large number of tasks in the 
 mining industry that require manual mate- 
 rials handling (MMH) and the enormous 
 costs associated with musculoskeletal in- 
 juries resulting from MMH, job design and 
 employee placement procedures for MMH 
 tasks in the mining industry would be 
 beneficial. A major step in establishing 
 these procedures is the determination of 
 the lifting capacity of the individual or 
 population performing a given lifting 
 task. The three primary approaches used 
 to determine lifting capacity are the bi- 
 omechanical approach, the physiological 
 
 approach, and the psychophysical ap- 
 proach. This paper proposes the use of 
 the psychophysical approach to determine 
 lifting capacity owing to the fact that 
 it attempts to combine the biomechanical 
 and physiological stresses present in all 
 lifting tasks under a measure of per- 
 ceived stress. A mathematical, fuzzy- 
 sets-based model of lifting capacity is 
 presented that demonstrates that the com- 
 bining of acceptability measure for psy- 
 chophysical stress. Advantages of the 
 fuzzy-sets-based model and examples of 
 its use are given. 
 
 INTRODUCTION 
 
 Manual materials handling (MMH) activi- 
 ties, and in particular manual lifting, 
 are recognized as a major hazard to the 
 safety and health of industrial workers 
 (17)5 and a majorcost to industry (10). 
 Recent evidence ( 19 ) supports the notion 
 that numerous tasks in the mining indus- 
 try involve manual lifting, and as such 
 could be helped by improved job design 
 and employee placement procedures in or- 
 der that job demands can be controlled to 
 stay within individual capacities. A 
 major step in the establishment of such 
 procedures is the determination of the 
 
 lifting capacity of the individual or 
 population performing these jobs. It has 
 been noted by Karwowski ( 11 ) that no OSHA 
 regulations exist regarding the maximum 
 acceptable weight of lift; this being 
 due in part to the fact that existing 
 recoimnendations are based on different 
 methodological approaches assessing dif- 
 ferent categories of stresses in MMH ac- 
 tivities. The three primary approaches 
 to determine lifting capacity are (1) the 
 biomechanical approach, (2) the physio- 
 logical approach, and (3) the psychophys- 
 ical approach. 
 
 BIOMECHANICAL APPROACH 
 
 In general, biomechanics determines 
 what a person can physically do. Bio- 
 mechanical models attempt to establish 
 the physical stresses imposed on the 
 musculoskeletal system during a lifting 
 action; these stresses serve as the 
 
 ^Horn professor of industrial and bio- 
 medical engineering, Texas Tech Univer- 
 sity, Department of Industrial Engineer- 
 ing, Lubbock, TX. 
 
 ^Research associate, Texas Tech Univer- 
 sity, Department of Industrial Engineer- 
 ing, Lubbock, TX. 
 
 criteria upon which capacity of lift 
 is based. These physical stresses in- 
 clude reaction forces and torques on var- 
 ious joints of the body (4^) and compres- 
 sive and shear forces on the lower back 
 
 ■^Assistant professor, Iowa State Uni- 
 versity, Ames, lA. 
 
 "^Research associate, Texas Tech Univer- 
 sity, Department of Industrial Engineer- 
 ing, Lubbock, TX. 
 
 ^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this paper. 
 
55 
 
 _5-^). The low back, in particular the 
 L4-L5 and L5-S, disks of the lower back, 
 is especially considered as a basis for 
 load lifting limits owing to the exces- 
 sively high forces produced on the low 
 back when lifting O, _18, 22^) and the 
 large number of back injuries arising 
 from manual lifting. 
 
 The ultimate goal of the biomechanical 
 approach is to set limits on these physi- 
 cal stresses imposed during lifting and 
 then determine the load-lifting capacity 
 based on these limits. Towards this 
 goal, both static and dynamic models of 
 lifting capacity have been developed 
 based on the biomechanical approach. 
 Static biomechanical models, such as 
 those developed by Chaff in ( 4_) , assume 
 that the lifting action is performed 
 slowly and smoothly such that forces due 
 to the acceleration can be neglected. 
 Dynamic models, such as those developed 
 by Fischer (7), El-Bassoussi (6), Ayoub 
 O), and Muth ( 16 , pp. 96-109), provide 
 data for analyses in the form of time- 
 displacement relationships of the body 
 segments (kinematic analysis) and the 
 forces and torques involved in the motion 
 (kinetic analysis). 
 
 Figure 1, based on the dynamic biome- 
 chanical model developed by El-Bassoussi 
 (6) and Ayoub (3), presents lifting ca- 
 pacity guidelines developed using the 
 biomechanical approach. The figure shows 
 three different lifting regions based on 
 compression on the spine. Weights of 
 
 lift producing con^ressive forces of less 
 than 1,100 lb are considered acceptable 
 (i.e., minimal risk of injury to worker). 
 Lifting tasks producing compressive 
 forces of 1,540 lb or more are considered 
 hazardous and should be redesigned. The 
 region between these two values falls un- 
 der the area of administrative control. 
 As is also indicated in the figure, if 
 the center of gravity (CG) of a load from 
 the spine is 20 in, an acceptable weight 
 of load would be 25 lb, and a weight of 
 load of 69 lb or more would produce ex- 
 cessive compressive forces on the spine. 
 The constant compression lines were de- 
 veloped using the concept of a biomechan- 
 ical equivalent (22) in the form of 
 
 BE = H 
 
 (w). 
 
 where BE = biomechanical equivalent, 
 pound-inch, 
 
 H = horizontal distance of the 
 CG of the load from the 
 spine, inches. 
 
 and 
 
 W = weight of the load, pounds. 
 
 The model allows the calculation of the 
 compressive and shearing forces on the 
 Lc-S^ disk during the time course of a 
 lifting movement in the sagittal plane 
 from floor to a 2.5-ft height. The out- 
 put of the model include the reactive 
 forces and torques at several joints in- 
 volved in the motion. 
 
 PHYSIOLOGICAL APPROACH 
 
 The physiological approach may use sev- 
 eral criteria, such as oxygen consump- 
 tion, heart rate, pulmonary ventilation 
 volume, or percent of physical work ca- 
 pacity, as indices of heaviness of work 
 performed. Generally, the criterion used 
 is the energy expenditure while lifting 
 loads. 
 
 Oxygen consumption is generally mea- 
 sured to estimate the energy expenditure 
 required by a lifting task. The measure- 
 ment of the physiological demands can al- 
 so be related to an individual's maximum 
 aerobic capacity in order to determine 
 
 what percent of that capacity a given 
 lifting task requires. 
 
 As with the biomechanical approach, the 
 goal of the physiological approach is to 
 develop limits using metabolic energy ex- 
 penditure criteria and then determine 
 lifting capacity based on the chosen cri- 
 teria limits. Several prediction models 
 of metabolic energy expenditure for lift- 
 ing tasks have been developed (4^, 8^-^). 
 Based on the physiological approach, 
 it has been concluded that, for a young 
 male, the 8-h average metabolic rate 
 should not exceed 5 kcal/min or 33 pet of 
 
56 
 
 the individual's maximum aerobic capac- 
 ity, and heart rate should not exceed 110 
 to 115 beats per minute (20). Figure 2, 
 based on the model reported by Garg ( 11 ) , 
 shows the effect of frequency of lift 
 
 (lifts per minute) and lifting technique 
 on the weight of load that can be lifted 
 to maintain an energy expenditure of 5 
 kcal/min. 
 
 PSYCHOPHYSICAL APPROACH 
 
 The third method employed to determine 
 lifting capacity is the psychophysical 
 approach. Psychophysics deals with the 
 relationship between human sensations and 
 their physical stimuli; this relationship 
 best being described by a power function 
 (21). The use of psychophysics in lift- 
 ing tasks requires the subject to adjust 
 the weight of load according to his or 
 her own perception of effort such that 
 the lifting task does not result in over- 
 exertion or excessive fatigue. The final 
 weight decided upon by the subject repre- 
 sents the maximum acceptable weight of 
 lift for the given job conditions (fre- 
 quency of lift, height of lift, container 
 size, etc.). 
 
 Several lifting capacity prediction 
 models using the psychophysical approach 
 have been developed (13-15). The major 
 limitation with these models has been 
 that they are applicable to only one or 
 two lifting ranges and only one frequency 
 of lift. Ayoub (2) developed lifting 
 
 capacity prediction models that were more 
 flexible than the previously developed 
 models in that six ranges of lift and 
 different work paces were accommodated by 
 the model. Table 1 presents the lifting 
 capacity norms for male and female indus- 
 trial workers developed by Ayoub (2). 
 Figure 3 presents capacity norms adjusted 
 for load size and frequency of lift de- 
 veloped by the senior author. The capac- 
 ity norms are given by the formula 
 
 LC = rv X a X b, 
 
 where LC = capacity of lift, pounds, 
 
 rv = reference value at one lift 
 per minute, 
 
 a = percent multiplier for 
 frequency, 
 
 and b = percent multiplier for load 
 size 
 
 TABLE 1. - Distribution of maximum weights of lift acceptable to male 
 and female industrial workers' (corrected for one lift per minute 
 and load size of 18 in), pounds 
 
 Range of lift 
 
 Sex 
 
 Mean 
 
 SD 
 
 
 Percent 
 
 of population 
 
 
 
 95 
 
 75 
 
 50 
 
 25 
 
 5 
 
 Floor to knuckle 
 
 Male... 
 Female. 
 
 61.17 
 37.12 
 
 16.87 
 6.76 
 
 33.43 
 26.00 
 
 49.62 
 32.50 
 
 61.17 
 37.12 
 
 72.71 
 41.73 
 
 88.90 
 
 
 48.20 
 
 Floor to shoulder 
 
 Male... 
 
 51.12 
 
 12.11 
 
 31.29 
 
 42.91 
 
 51.21 
 
 59.50 
 
 71.13 
 
 
 Female. 
 
 31.08 
 
 6.54 
 
 20.32 
 
 26.60 
 
 31.08 
 
 35.56 
 
 41.83 
 
 Floor to reach 
 
 Male. . . 
 Female. 
 
 49.12 
 28.14 
 
 11.20 
 5.41 
 
 30.69 
 19.24 
 
 41.45 
 24.41 
 
 49.12 
 28.14 
 
 56.79 
 31.84 
 
 67.54 
 
 
 37.04 
 
 Knuckle to shoulder 
 
 Male... 
 
 57.75 
 
 14.67 
 
 33.33 
 
 47.42 
 
 57.47 
 
 67.52 
 
 81.60 
 
 
 Female. 
 
 31.97 
 
 6.55 
 
 21.19 
 
 27.48 
 
 31.97 
 
 36.45 
 
 42.74 
 
 Knuckle to reach 
 
 Male. . . 
 Female. 
 
 53.54 
 26.22 
 
 10.70 
 4.86 
 
 35.93 
 18.22 
 
 46.21 
 22.89 
 
 53.54 
 26.22 
 
 60.87 
 29.55 
 
 71.14 
 
 
 34.21 
 
 Shoulder to reach. ......... 
 
 Male. . . 
 Female. 
 
 43.62 
 25.78 
 
 10.45 
 4.17 
 
 26.43 
 18.92 
 
 36.46 
 22.92 
 
 42.62 
 25.78 
 
 50.77 
 28.63 
 
 60.81 
 
 
 32.64 
 
 SD Standard deviation. 'As 
 
 suminp a 
 
 normal 
 
 distrit- 
 
 Kitlon. 
 
 
 
 
 
57 
 
 COMPARISON OF THE THREE APPROACHES 
 
 It is the assertion of this paper that 
 the psychophysical approach is the appro- 
 priate single approach to use to deter- 
 mine lifting capacity. The problem with 
 the use of the biomechanical approach or 
 the physiological approach alone is that 
 both biomechanical and physiological 
 stresses are usually present in almost 
 all lifting tasks. Using the aforemen- 
 tioned physiologically based guidelines 
 proposed by Snook (20) , it is intuitively 
 obvious that an individual could stay 
 within the recommended physiological lim- 
 its by lifting a very heavy load at a low 
 frequency of lift. However, such a pro- 
 cedure would violate lifting capacity 
 recommendations based on biomechanical 
 criteria. Conversely, lifting capacity 
 models based solely on biomechanical cri- 
 teria are wholly inadequate in dealing 
 with the effects of repetitive lifting on 
 the cumulative physical stresses imposed 
 on the body. 
 
 The discrepancies encountered by the 
 use of biomechanical or physiological 
 criteria alone in the determination of 
 lifting capacity become evident when com- 
 paring the lifting guidelines presented 
 in figure 1 (using the biomechanical ap- 
 proach) and the lifting guidelines pre- 
 sented in figure 2 (using the physiologi- 
 cal approach). Although attempting to 
 make comparisons between these two ap- 
 proaches is difficult, the aforementioned 
 problems associated with using only a 
 biomechanical or physiological criterion 
 can be made more evident. For example, 
 a weight of load of 88.2 lb is acceptable 
 at low frequencies of lift using the 
 
 physiological approach, whereas this same 
 weight of load significantly exceeds the 
 acceptable lifting region recommended 
 when using the biomechanical approach. 
 In fact, in situations where the horizon- 
 tal distance of the center of gravity of 
 the load from the spine exceeds approxi- 
 mately 12 in, a weight of load of 88.2 lb 
 is considered hazardous based on the bio- 
 mechanical criteria. 
 
 In general MMH recommendations based on 
 biomechanical models suggest lifting 
 light loads at higher frequencies of 
 lift, whereas physiological models sug- 
 gest the lifting of heavier loads at a 
 reduced frequency of lift. Also, it is 
 often assumed by researcher in the area 
 of MMH that only biomechanical criteria 
 need to be considered if the frequency of 
 lift is low, and only physiological cri- 
 teria need to be considered for higher 
 frequencies of lift. This could be a 
 dangerous oversimplification. 
 
 Lifting is a task of a complex nature 
 such that it cannot be fully explained 
 using only physiological or biomechani- 
 cal criteria. Both physiological and 
 biomechanical stresses, among others, 
 are present in every lifting task and, 
 as such, the need exists for a means of 
 determining lifting capacity that can 
 accommodate both of these everpresent 
 stresses. The virtue of the psycho- 
 physical approach is that it attempts to 
 combine the stresses, including the bio- 
 mechanical and physiological stresses 
 present in the lifting task under a mea- 
 sure of perceived stress. 
 
 COMBINED STRESS VERSUS PSYCHOPHYSICAL STRESS 
 
 The psychophysical approach is based on 
 the assumption that the biomechanical and 
 physiological stresses are integrated or 
 combined under the measure of perceived 
 stress. No theoretical method has exist- 
 ed in the past for combining the biome- 
 chanical and physiological stresses to 
 determine their relationship with the 
 psycholphysical stress. However, a re- 
 cent model of lifting capacity developed 
 
 and reported by Karwowski (11-12) has 
 provided a means by which the relation- 
 ship between the combined effects of bio- 
 mechanical and physiological stresses and 
 the perceived stress determined psycho- 
 physically can be explained. 
 
 Karwowski ( 11 ) hypothesized that a 
 combination of the acceptability of bio- 
 mechanical and physiological stresses 
 
58 
 
 imposed during manual lifting leads to an 
 overall measure of the lifting task ac- 
 ceptability, expressed by the acceptabil- 
 ity of the psychophysical stress. Toward 
 the testing of this hypothesis, Karwowski 
 utilized a fuzzy sets theory [for a thor- 
 ough explanation of the concept and fun- 
 damentals of fuzzy sets theory refer to 
 Zadeh (23)]. 
 
 Karwowski (11) developed a fuzzy set 
 model from which an acceptability measure 
 for biomechanical stress and an accepta- 
 bility measure for physiological stress 
 could be integrated into a measure of 
 combined stress. Following this, mathe- 
 matical procedures stemming from fuzzy 
 sets theory were used to determine the 
 relationship between the maximum accepta- 
 ble weight of lift from the psychophysi- 
 cal and combined standpoints. Based on 
 these mathematical procedures, Karwowski 
 (11) concluded that the maximum accepta- 
 ble weight of lift based on a psychophys- 
 ical criterion appears to be the result 
 of the integration of the biomechanical 
 and physiological stresses imposed by the 
 lifting task. 
 
 Figure 4 shows the relationship between 
 the acceptability measures of the com- 
 bined stress versus the acceptability 
 measures of the psychophysical stress. 
 The combined stress is determined by tak- 
 ing the algebraic product of the accepta- 
 bility measures of the biomechanical and 
 physiological stress. The acceptability 
 measure is determined using membership 
 functions developed by Karwowski (11) for 
 the biomechanical, physiological, and 
 psychophysical stress. The degree of 
 membership can be any value ranging from 
 to 1 , with representing nonmembership 
 in a set, and 1 indicating total member- 
 ship in the set. The stresses given a 
 value of 1 (i.e., are totally acceptable 
 in terms of stress imposed) .were selected 
 based on past research in the areas of 
 acceptable biomechanical, physiological, 
 and psychophysical stresses. For exam- 
 ple, the membership function for the ac- 
 ceptability of the psychophysical stress 
 was based on the lifting capacity norms 
 presented in figure 1. 
 
 One of the advantages presented by the 
 fuzzy-sets-based model is that it allows 
 for the determination of lifting capaci- 
 ty, and consequently allows for the de- 
 sign of a lifting task, without the ne- 
 cessity of performing any psychophysical 
 experiments. By determining the accepta- 
 bility measure of the biomechanical and 
 physiological stresses imposed on the in- 
 dividual while lifting a specified weight 
 of load and then combining these two 
 stresses into a single category, the lev- 
 el of psychophysical stress that is like- 
 ly to occur for this particular lifting 
 task can be assessed. In addition, pre- 
 dictive models already exist whereby the 
 physiological and biomechanical stresses 
 can be determined without extensive ex- 
 perimentation. Oxygen consumption can be 
 predicted using equations such as those 
 developed by Garg (9) or Asfour (J^) . Bi- 
 omechanical stresses can be predicted us- 
 ing a dynamic biomechanical model such as 
 the one developed by El-Bassoussi (6^). 
 
 Using an example from Karwowski (11), 
 consider a task in which an individual 
 lifts 75 lb from floor to knuckle height 
 at a frequency of three lifts per minutes 
 using a squat lifting technique (i.e., 
 back straight, bent at knees). Given 
 these task conditions, oxygen consumption 
 would be approximately 0.886 L/min and ] 
 the biomechanical stress imposed would be 
 1,690 lb, with the acceptability measures 
 for the physiological and biomechanical 
 stress based on the fuzzy sets model be- 
 ing 0.7929 and 0.5233, respectively. The 
 membership functions for the biomechani- 
 cal and physiological stress from which 
 the acceptability measures were deter- 
 mined are given in figures 5 and 6, re- 
 spectively. The combined stress is then 
 determined to be 0.4150 (by taking the 
 algebraic product of the acceptability 
 measures of the biomechanical and physio- 
 logical stress). The hypothetical capac- 
 ity norm can then be determined by multi- 
 plying the 75 lb by the acceptability 
 measure for the combined stress. Based 
 on this product , it can be concluded that 
 a weight of load of 31.13 lb would repre- 
 sent a totally acceptable weight for the 
 given task. 
 
59 
 
 To further illustrate the relationship 
 between the acceptability measures for 
 the combined stress and the psychophysi- 
 cal stress, the psychophysical stress 
 calculated by the fuzzy sets model was 
 0.4552. As can be seen in figure 7, the 
 capacity norm based on the psychophysical 
 methodology is 34.14 lb. The difference 
 
 between this norm and the hypothetical 
 capacity norm derived from the combined 
 stress is 3.01 lb (9.13 pet). This rep- 
 resents more evidence that the psycho- 
 physical stress is a combination of the 
 physiological and biomechanical stresses 
 imposed on the individual while lifting. 
 
 SUMMARY 
 
 Figure 8 presents a model of lifting 
 performance that summarizes the proposals 
 made in this paper. First, the ultimate 
 goal and purpose of lifting capacity de- 
 termination is to stay within individual 
 capacity when designing total job demand. 
 By accomplishing this , the percentage of 
 the population able to perform the task 
 increases and the injuries associated 
 
 with people exceeding or approaching 
 their physical capabilities diminishes. 
 Second, in order to match individual ca- 
 pacity with total job demand, the lifting 
 capacity of workers must be determined. 
 This paper hopefully has proposed that 
 the psychophysically determined lifting 
 capacity should be used as the basis for 
 job design and placement of workers. 
 
 REFERENCES 
 
 1. Asfour, S. S. Energy Cost Predict- 
 ing Models for Manual Lifting and Lower- 
 ing Tasks. Ph.D. Dissertation, Texas 
 Tech University, Lubbock, TX, 1980. 
 
 2. Ayoub, M. M. , N. J. Bethea, S. 
 Deivanayagam, S. S. Asfour, and M. 
 Sherif. Determination and Modeling of 
 Lifting Capacity. Final Rept. HEW 
 (NIOSH) grant No. 5R010H-00545-02, Sep- 
 tember 1978; available upon request from 
 M. M. Ayoub, Texas Tech Univ., Lubbock, 
 TX. 
 
 3. Ayoub, M. M. , and M. M. El- 
 Bassoussi. Dynamic Biomechanical Model 
 for Sagittal Lifting Activities. Paper 
 in Proceedings of the 6th Congress of In- 
 ternational Ergonomics Association, 1976, 
 pp. 355-359. 
 
 Medical Publishers, Inc., Chicago, IL, 
 1975, Chapter 19. 
 
 6. El-Bassoussi, M. M. A Biomechani- 
 cal Dynamic Model for Lifting in the 
 Sagittal Plane. Ph.D. Dissertation, Tex- 
 as Tech University, Lubbock, TX, 1974; 
 available upon request from M. M. Ayoub, 
 Texas Tech Univ., Lubbock, TX. 
 
 7. Fisher, B. 0. Analysis of Spinal 
 Stresses during Lifting. Unpublished 
 M.S. Thesis, The University of Michigan, 
 Ann Arbor, MI, 1967; available upon re- 
 quest from M. M. Ayoub, Texas Tech Univ., 
 Lubbock, TX. 
 
 8. Frederik, 
 Manual Lifting, 
 dling, V. 14, No, 
 
 W. S. Human Energy in 
 Modern Materials Han- 
 3, 1959, pp. 74-76. 
 
 4. Chaffin, D. B. The Development of 
 a Prediction Model for Metabolic Energy 
 Expended During Arm Activities. Unpub- 
 lished Ph.D. Dissertation, University of 
 Michigan, 1967; available upon request 
 from M. M. Ayoub, Texas Tech Univ., Lub- 
 bock, TX. 
 
 5. Chaffin, D. B. Manual Materials 
 Handling and Low Back Pain. Occupational 
 Medicine, Principles and Practical Ap- 
 plications. Ed. by C. Zenz Year Book 
 
 9. Garg, A. A Metabolic Prediction 
 Model for Manual Materials Handling Jobs. 
 Unpublished Ph.D. Dissertation, The Uni- 
 versity of Michigan, Ann Arbor, MI, 1976; 
 available upon request from M. M. Ayoub, 
 Texas Tech Univ., Lubbock, TX. 
 
 10. Goldberg, H. M. Diagnosis and 
 Management of Low Back Pain. J. of Occu- 
 pational Health and Safety, v. 49, No. 6, 
 June 1980. 
 
60 
 
 11. Karwowski, W. A Fuzzy Sets Based 
 Model on the Interaction Between Stresses 
 Involved in Manual Lifting Tasks. Unpub- 
 lished Ph.D. Dissertation, Texas Tech 
 University, Lubbock, TX, 1982; available 
 upon request from M. M. Ayoub, Texas Tech 
 Univ. , Lubbock, TX. 
 
 12. Karwowski, W. , and M. M. Ayoub. 
 Fuzzy Approach in Psychophysical Modeling 
 of Human Operator-Manual Lifting System. 
 Unpublished article, January 1983; avail- 
 able upon request from M. M. Ayoub, Texas 
 Tech Univ., Lubbock, TX. 
 
 13. Knipfer, R. E. Predictive Models 
 for the Maximum Acceptable Weight of 
 Lift. Ph.D. Dissertation, Texas Tech 
 University, Lubbock, TX, 1974. 
 
 14. McConville, J. T. , and H. T. E. A. 
 Hertzberg. A Study of One Hand Lifting: 
 Final Report. Wright-Patterson AFB, OH, 
 Aerospace Med. Res. Lab., Tech. Rept. 
 AMRL-TR-66-17, May 1966. 
 
 15. McDaniel, J. W. Prediction of Ac- 
 ceptable Lift Capability. Ph.D. Disser- 
 tation, Texas Tech University, Lubbock, 
 TX, 1972. 
 
 16. Muth, M. B., M. M. Ayoub, and 
 W. A. Gruver. A Nonlinear Programming 
 Model for the Design and Evaluation of 
 Lifting Tasks. Chapter in Safety in 
 
 Manuals Materials Handling, ed. by Colin 
 G. Drury, NIOSH, Pub. 78-185, 1978, 219 
 pp.; NTIS PB-297-660. 
 
 17. National Safety Council. Accident 
 Facts. Chicago, IL. , 1981. 
 
 18. Park, K. S., and D. B. Chaffin. A 
 Biomechanical Evaluation of Two Methods 
 of Manual Load Lifting. Trans. AIIE, 
 V. 6, 1974, pp. 105-113. 
 
 19. Selan, J., M. M. Ayoub, and 
 H. P. R. Rao. Manual Materials Handling 
 in the Mining Industry. Unpublished re- 
 port; available upon request from M. M. 
 Ayoub, Texas Tech Univ. , Lubbock, TX. 
 
 20. Snook, S. H. , and C. H. Irvine. 
 Maximum Acceptable Weight of Lift. Am. 
 Ind. Hyg. Assoc. J., v. 28, No. 4, 1967, 
 pp. 322-329. 
 
 21. Stevens, S. S. Psychophysics: 
 Introduction to Its Perceptual, Neural, 
 and Social Prospects. Wiley, 1975. 
 
 22. Tichauer, E. R. A Pilot Study of 
 the Biomechanics of Lifting in Simulated 
 Industrial Work Situations. J, Safety 
 Res., V. 3, No. 3, 1971, pp. 98-115. 
 
 23. Zadeh, L. A. Fuzzy Sets. In- 
 formation and Control, v. 8, June 1965, 
 pp. 338-353. 
 
61 
 
 HORIZONTAL DISTANCE OF CENTER OF GRAVITY 
 OF LOAD FROM SPINE, in 
 
 FIGURE 1. . Maximum weight versus horizon- 
 tal distance from spine based on 1,100 lb and 
 1,540 lb of compression on spine, respectively. 
 
 C 
 
 0> 
 
 a. 
 
 
 8 
 
 >- 
 
 
 < ) 
 
 
 2 
 
 ^ 
 
 LU 
 
 
 Z) 
 
 6 
 
 cjr 
 
 
 LU 
 
 
 QC 
 
 5 
 
 Ll_ 
 
 
 
 4 
 
 
 3 
 
 
 2 
 
 Straight back, 
 _ bent knee 
 (floor to 2. 5 ft) 
 I 
 
 30 60 90 
 
 WEIGHT OF THE LOAD, lb 
 
 FIGURE 2. = Effect of lifting technique and fre- 
 quency of lift on weight of load that can be lifted 
 to maintain metabolic energy expenditure of 5 
 kcal/min. 
 
62 
 
 BOX SIZE, in 
 18 19 20 21 22 23 24 25 26 27 28 29 
 
 0.1 0.2 03 0.4 0.5 0.6 0.7 0.8 0.9 I 2 4 
 
 FREQUENCY, lift per minute 
 
 FIGURE 3. - Lifting capacity norms for males (floor-to-knuckle height). 
 
 8 10 12 
 
 a 
 
 UJ 
 
 0.9 
 
 z 
 
 
 m 
 
 .8 
 
 S 
 
 
 o 
 
 
 o 
 
 .7 
 
 U-y) 
 
 
 Oy) 
 
 6 
 
 >^ 
 
 
 I-? 
 
 
 ^^ 
 
 .5 
 
 m 
 
 
 ^ 
 
 .4 
 
 Q. 
 
 
 U 
 
 
 O 
 
 .3 
 
 O 
 
 
 < 
 
 
 
 .2 
 
 
 
 
 I I I I I I I I I I I I I I I 
 R= 1.0 
 
 / - 
 
 „c 
 
 • •••• * 
 
 ^* • • 
 
 ■ I ■ I . I . I . I . I 
 
 1.0 
 
 2 0.4 0.6 0.8 I.O 
 
 ACCEPTABILITY OF PSYCHOPHYSICAL 
 STRESS 
 
 FIGURE 4, - Acceptability of the combined bio- 
 mechanical and physiological stress versus the 
 acceptability of the psychophysical stress. 
 
 if) 
 
 < 
 
 UJ 
 
 >• .5 - 
 
 CD 
 < 
 
 I- 
 Q. 
 UJ 
 O 
 O 
 < 
 
 
 1 
 
 Lifts per minute 
 1-12 3-3 
 2-9 4-0.1 
 
 1 1 
 
 1 
 
 440 880 1,320 1,760 2,200 
 
 COMPRESSIVE FORCE, lb 
 
 FIGURE 5. - Membership function for biome- 
 chanical stress. 
 
63 
 
 1.0 
 
 UJ 
 
 ir 
 
 ZD 
 
 cn 
 < 
 
 UJ 
 
 t .5 - 
 
 CD 
 
 < 
 I- 
 Q. 
 UJ 
 O 
 O 
 < 
 
 \ 
 
 0.7929 \ 
 
 >^ Frequency 
 ^v =9,12 
 
 - 
 
 Frequency ^s^ 
 = 0.1,3 \^ 
 
 1 
 
 0.886 L/min 
 1 1 
 
 0.5 I 1.5 2 
 
 OXYGEN CONSUMPTION, L/min 
 
 FIGURE 6. - Membership function for physio- 
 logical stress. 
 
 20 30 40 50 60 70 80 90 
 WEIGHT OF LOAD, lb 
 
 FIGURE 7, - Membership function of psycho- 
 physical stress. 
 
 Operator 
 capacity 
 
 Operator 
 characteristics 
 
 Task 
 characteristics 
 
 Environmental 
 characteristics 
 
 Biomechanical 
 demands 
 
 Physiological 
 demands 
 
 Psychological 
 demands 
 
 Comparison 
 
 Percent 
 accommodated 
 
 Total 
 demand 
 
 Psychophysical 
 demand 
 
 FIGURE 8. - A model of lifting performance. 
 
64 
 
 JOB DESIGN FOR MANUAL MATERIAL HANDLING TASKS 
 By M. M. Ayoub,1 J. L. Selan,2 and H. P. R. Rao3 
 
 ABSTRACT 
 
 A procedure for job design of and em- 
 ployee placement into manual material 
 handling (MMH) tasks based on job demand 
 and employee capacity is discussed. The 
 first step involves an extensive analysis 
 of selected jobs in terms of injury data 
 (nature of injury, number of lost work- 
 days, etc.) and lifting requirements of 
 the job (weight, frequency, range of 
 lift, etc.). The measure of job stress 
 to be used is a job severity index (JSI). 
 The JSI is the ratio of the job demand to 
 the capacity of the person or population 
 
 working under the job conditions, ex- 
 pressed as the time frequency weighted 
 average of the maximum weight required by 
 each task divided by the smallest lifting 
 capacity given the lifting task condi- 
 tions. The JSI provides a means to mea- 
 sure job severity and to define the rela- 
 tionship between this measure and an ac- 
 ceptable measure of injury potential. 
 Procedures for job design and employee 
 placement based on the JSI are discussed 
 and examples are given. 
 
 INTRODUCTION 
 
 A large number of work injuries in 
 the industrial arena arise either direct- 
 ly or indirectly from the handling and/ 
 or mishandling of materials. National 
 Safety Council (8^)'* statistics indicate 
 that 27 pet of all industrial injuries 
 were associated with MMH; this percentage 
 equaled 590,000 injuries with a total 
 cost of approximately $10.4 billion. 
 More important, the number of MMH-related 
 injuries continues to increase (670,000 
 injuries in 1980 based on National Safety 
 Council estimates) despite improved medi- 
 cal care, increased automation in indus- 
 try, and more extensive use of preemploy- 
 ment examinations. 
 
 More imposing than the increase in 
 the number of work injuries is the in- 
 crease in the cost of these injuries. 
 The economic costs associated with MMH- 
 related injuries include medical costs, 
 lost worktime, insurance-related costs, 
 loss of material and property damage, 
 lost wages, training cost of a new 
 worker, and administration costs. The 
 
 'Horn professor of industrial and bio- 
 medical engineering. 
 
 ^Research associate. 
 
 ■^Research associate. 
 
 Texas Tech University, Department of 
 Industrial E^ngineering, Lubbock, TX. 
 
 relationship between these costs and back 
 injuries over a 33-yr span (1957-90, pro- 
 jected) is exponential as shown in figure 
 1 [based on National Safety Council esti- 
 mates; from Aghazadeh (J_) ] . The alarming 
 rate of increase in the cost of back in- 
 juries has also been reported by Snook 
 (11). During the 1938-65 period, the 
 number of compensable back injuries in- 
 creased by 11.4 pet while the average 
 cost per back injury increased by approx- 
 imately 400 pet. 
 
 The mining industry contains several 
 jobs in which MMH activities, in particu- 
 lar manual lifting, constitute a major 
 component of the job (10) . A listing of 
 some of these jobs is given below. 
 
 Jackleg drilling 
 
 Stoper drilling 
 
 Tmbering 
 
 Steel set construction 
 
 Concrete construction 
 
 '^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this paper. 
 
65 
 
 Gunite and shotcreting 
 
 Rock dusting 
 
 Loading powder bags 
 
 Ventilation and pipe installation 
 
 Track installation and maintenance 
 
 Given this prevalence of MMH activities 
 in the mining industry, it would not be 
 surprising to find a large number of in- 
 juries including back injuries among min- 
 ers. It has been reported (_8) that in 
 Pennsylvania 4.8 pet of all con^)ensable 
 back injuries were from miners. A study 
 presently being conducted for the Bureau 
 of Mines (5) also indicates indirectly 
 the presence of worker injuries in the 
 mining industry. As part of the ongoing 
 study (5), isometric strength tests are 
 being conducted on miners, provided at 
 the time of the test, the miner is not 
 suffering from a back injury of any kind. 
 Over 10 pet of all miners in the study 
 have reported back injuries (although 
 it has not been determined in the study 
 whether the injuries were directly work 
 related). It has been noted in another 
 recent study conducted for the Bureau of 
 Mines (2), that the heavy lifting demands 
 and awkward postures imposed in low- 
 coal mining (seam height <48 in) may re- 
 sult in an increased probability of back 
 injuries. 
 
 Nordby {9) reported that, out of 8 mil- 
 lion low-back problems that occurred in 
 1974, 200,000 required surgical treat- 
 ment. Because of the severity, fre- 
 quency, and cost of MMH-related injuries, 
 procedures for job design of and employee 
 placement into MMH tasks need to be 
 seriously considered, properly developed, 
 and applied. Such procedures should be 
 based on job demands and worker capacity, 
 and need to be validated in the work 
 environment. The means to determine 
 worker capacity has been discussed else- 
 where (6), therefore, only a brief sum- 
 mary will be presented here. 
 
 The variables affecting lifting capac- 
 ity fall into three general categories: 
 
 worker, task, and environmental. Worker 
 variables include such factors as body 
 weight, sex, age, training, etc. Task 
 variables include frequency of lift, 
 range of lift, load size, and others. 
 Some significant environmental variables 
 include heat stress, floor stability, 
 traction, etc. There are three different 
 bases for determining lifting capacity. 
 These are the biomechanical basis, the 
 physiological basis, and the psychophysi- 
 cal basis. For the biomechanical basis, 
 estimates are made of the stresses im- 
 posed on the musculoskeletal system while 
 lifting. Limits for these stresses are 
 established from which the capacity or 
 loads to be lifted can then be estimated. 
 Similarly, the physiological basis sets 
 upper limits based on metabolic or car- 
 diovascular criteria (e.g., percent of 
 physical work capacity) and then deter- 
 mines lifting capacity as some percentage 
 of the physiological indice(s). 
 
 As noted by Ayoub (^) , the problem with 
 using either the biomechanical or physio- 
 logical approach is that both stresses 
 are present in any lifting activity. The 
 third basis, psychophysical, attempts to 
 combine the biomechanical and physiologi- 
 cal stresses under a measure of perceived 
 stress on the part of the individual. 
 The measure of lifting capacity used in 
 conjunction with psychophysical methods 
 is the "maximum acceptable" or "maximum 
 safe weight of lift," defined as the max- 
 imum weight an individual feels he or she 
 could lift repeatedly without undue 
 stress or overtiring. 
 
 The purpose of this paper is to propose 
 the use of the JSI developed by Ayoub (_3) 
 as a means to define the relationship be- 
 tween an acceptable measure of injury po- 
 tential and a measure of job severity. 
 Also, this paper proposes the use of the 
 procedures outlined by Ayoub (3^) , based 
 on the work done with the JSI, for job 
 design of and employee placement into MMH 
 tasks based on job parameters and employ- 
 ee capacity. The JSI will be defined in 
 the following section, and in the final 
 section the job design-employee placement 
 procedures based on the JSI will be 
 discussed. 
 
66 
 
 THE JOB SEVERITY INDEX 
 
 DEVELOPMENT 
 
 The JSI conceptually is the ratio of a 
 measure of job demand to a measure of the 
 capacity of the person or population per- 
 forming the job under the job conditions. 
 A large JSI represents a relatively 
 stressful job. 
 
 The job demands are determined using a 
 detailed job description procedure. The 
 initial step in the job description pro- 
 cedure is to determine the average length 
 of the work week, the average length of 
 the workday or shift, the number of 
 shifts per day, and a general written 
 description of the job. This information 
 is primarily used to determine the aver- 
 age job exposure time of the employees. 
 
 The next step is to describe each job 
 in terms of actual weight of lift, fre- 
 quency of lift, load size, and range of 
 lift. Because many jobs display a lack 
 of constant parameters (e.g., several 
 frequencies of lift are required), each 
 job is divided into a number of component 
 tasks such that each task can be de- 
 scribed with constant or near constant 
 parameters. Thus, each job is described 
 as a series of lifting tasks described in 
 terms of frequency of lift, range of 
 lift, etc. 
 
 Range of lift is defined in terms of 
 lift initiation level and lift termina- 
 tion level. The load size or dimension 
 is defined in terms of inches along a 
 line perpendicular to the frontal plane 
 of the body of the person doing the lift- 
 ing. Lifting frequency is defined as the 
 average number of lifts per minute re- 
 quired by the particular task. 
 
 The JSI is designed specifically for 
 those jobs requiring lifting as a sub- 
 stantial portion of the job. As such, 
 MMH activities, such as carrying, push- 
 ing, or pulling, are excluded from 
 analysis. However, the job description 
 
 procedure can be applied to lowering 
 tasks (which were found by Ayoub (3) to 
 occur in significant amounts in most jobs 
 requiring lifting). 
 
 The measure of lifting capacity used by 
 the JSI is the maximum acceptable weight 
 of lift determined based on psychophysi- 
 cal data. As noted, maximum acceptable 
 weight of lift is defined as the maximum 
 weight an individual feels he or she can 
 lift repeatedly without undue stress or 
 overtiring. Ayoub (3) developed a set of 
 mathematical models to predict the maxi- 
 mum acceptable weight of lift based on 
 various conditions of lifting frequency, 
 load size, and range 
 with a few strength 
 measurements. These 
 are presented in table 
 developed for each 
 ranges of lift: 
 
 of lift, coupled 
 and anthropometric 
 regression models 
 1. One model was 
 of the following 
 
 Floor to knuckle (F-K) 
 Floor to shoulder (F-S) 
 Floor to full reach (F-R) 
 Knuckle to shoulder (K-S) 
 Knuckle to full reach (K-R) 
 Shoulder to full reach (S-R) 
 
 These models have R2 values 
 
 of between 
 
 0.85 and 0.877. It should be noted that 
 these equations predict the sum of the 
 maximum acceptable weight of lift plus 
 body weight. The sex code is for 
 males and 1 for females. The weight 
 code is if body weight is below the 
 median and 1 if body weight is above the 
 median for the male or female population. 
 The median body weights for females and 
 males are 138 and 170 lb, respectively. 
 All strength variables are in pounds, age 
 is in years, endurance in minutes, 
 and anthropometric variables are in 
 centimeters. 
 
67 
 
 TABLE 1. - Prediction models for maximum acceptable weight of lift plus body weight 
 for both males and females 
 
 Lifting 
 
 Constant 
 
 Sex 
 
 Weight 
 
 Arm 
 
 Age 
 
 Shoulder 
 
 Back 
 
 Abdomin- 
 
 Dynamic 
 
 range 
 
 term 
 
 code 
 
 code 
 
 strength 
 
 
 height 
 
 strength 
 
 al depth 
 
 endurance 
 
 F-K 
 
 -72.165 
 
 -28.334 
 
 24.243 
 
 0.143 
 
 -0.553 
 
 1.225 
 
 0.056 
 
 4.914 
 
 1.757 
 
 F-S 
 
 -145.412 
 
 -16.165 
 
 11.928 
 
 .185 
 
 -.597 
 
 1.438 
 
 .077 
 
 6.472 
 
 2.608 
 
 F-R 
 
 -41.267 
 
 -19.453 
 
 16.176 
 
 .210 
 
 -.892 
 
 .759 
 
 .068 
 
 6.220 
 
 1.426 
 
 K-S 
 
 -55.160 
 
 -18.542 
 
 11.700 
 
 .265 
 
 -.606 
 
 .768 
 
 .105 
 
 6.290 
 
 1.415 
 
 K-R 
 
 -79.193 
 
 -18.917 
 
 17.273 
 
 .297 
 
 -.499 
 
 .092 
 
 .018 
 
 5.154 
 
 2.120 
 
 S-R 
 
 -37.439 
 
 -19.584 
 
 20.352 
 
 .096 
 
 -.592 
 
 .886 
 
 .099 
 
 4.731 
 
 1.090 
 
 F-K 
 F-S 
 
 Flo 
 Flo 
 
 or to knuckle, 
 or to shoulder. 
 
 F-R Floor to full reach. 
 K-S Knuckle to shoulder. 
 
 K-R Knuckle to full reach. 
 S-R Shoulder to full reach. 
 
 As noted, the JSI is a function of the 
 ratio of job demands to worker capacity. 
 Specifically, the JSI is the time and 
 frequency weighted average of the maximum 
 weight required by each task divided by 
 the smallest capacity of those associated 
 with lifting ranges required by each 
 task. The JSI is stated algebraically as 
 follows: 
 
 Dayst = total days per week for job. 
 
 Hours I = exposure hours per day for . 
 group i, 
 
 Hours^ = number of hours per day that 
 a job is performed, 
 
 F: = lifting frequency for task j, 
 
 n 
 JSI = E 
 
 Hours j 
 Hours-|- 
 = 1 
 
 Days j 
 Days -I- 
 
 £ix"^ 
 
 j = 1 
 
 CAPj 
 
 where n = number of sub-task groups , 
 
 F, = 
 
 WTj 
 
 total lifting frequency for 
 group i, 
 
 maximum weight of lift re- 
 quired by task j , 
 
 mj = number of task in group i. 
 
 Days I = exposure days per week for 
 group i, 
 
 and CAPj 
 
 the smallest applicable maxi- 
 mum acceptable weight of 
 lift adjusted for frequency 
 of lift and load size. 
 
 FIELD VALIDATION 
 
 Field validation of the JSI was con- 
 ducted by Ayoub in 1978 and 1982 {2-^). 
 The purpose of both studies was to at- 
 tempt to define the relationship between 
 MMH injury and the JSI. In general, the 
 methodology employed in both studies was 
 to evaluate the stress levels of indus- 
 trial subjects working in different lift- 
 ing jobs and relate the JSI to the injury 
 rates experienced by the same group of 
 subjects. 
 
 The first step in the field study phase 
 was the selection of jobs for analysis. 
 Selection was based on the extent that 
 the job involved MMH and specifically 
 
 lifting (e.g., a MMH job involving push- 
 ing would be excluded). Taking the 1978 
 and 1982 studies O-M together, a total 
 of 101 jobs involving 385 male and 68 fe- 
 male industrial workers from 2 private 
 companies and governmental agencies were 
 used in the field validation. 
 
 The selected jobs were analyzed in 
 terms of lifting requirements of the job 
 (procedure and parameters used were dis- 
 cussed earlier) and in terms of injury 
 data. Information collected describing 
 injuries included injury type, injury 
 cause (lifting or nonlif ting) , number of 
 days lost, medical expenses, wages paid 
 
68 
 
 during lost workdays, worker's compensa- 
 tion paid, and extraordinary expenses. 
 Injury type elassif ieations are given 
 below. 
 
 Type 1. Musculoskeletal injuries to 
 the back. 
 
 Type 2. Musculoskeletal injuries to 
 other body parts. 
 
 Type 3. Surface tissue injuries due to 
 impact. 
 
 Type 4. Other surface tissue injuries. 
 
 Type 5. Miscellaneous injuries. 
 
 Individual JSI 
 each industrial 
 JSI values were 
 JSI values great 
 or less than 0.7 
 equal to or les 
 1.5 and equal t 
 greater than 2.2 
 exposure times 
 group were then 
 
 's were calculated for 
 subject. The resulting 
 grouped into four ranges: 
 er than 0.00 and equal to 
 5, greater than 0.75 and 
 s than 1.5, greater than 
 o or less than 2.25, and 
 5. The injury data and 
 for the subjects in each 
 compiled and summed. 
 
 Figure 2 shows the relationship between 
 JSI and the number of back injuries sus- 
 tained per 100 full-time-equivalent (FTE) 
 employees (equal to 200,000 exposure 
 hours) for the 1978 and 1982 studies O- 
 h) combined. Figure 3 shows the rela- 
 tionship between JSI and the number of 
 disabling (one or more lost days) back 
 injuries sustained per 100 FTE employees 
 for the combined studies. Figure 4 shows 
 
 the relationship between JSI and the 
 severity (number of days lost per disab- 
 ling back injury) of disabling back inju- 
 ries. Figure 5 shows the relationship 
 between JSI and total direct injury ex- 
 pense (defined as the sum of medical ex- 
 penses, wages paid during lost workdays, 
 and worker's compensation) using data 
 from the 1982 study (M« For most of the 
 parameters, substantial increases oc- 
 curred at JSI levels equal to or greater 
 than 1.5, and for a number of parameters 
 (most notably severity of disabling back 
 injuries) there occurred another substan- 
 tial increase at JSI levels of 2.25 or 
 above. 
 
 Also determined was a stress measure 
 for each of the 101 jobs selected for 
 analysis. Following determination of the 
 stress measure, each job was placed into 
 one of the three following categories: 
 Jobs that overstressed less than or equal 
 to 5 pet of the sample population, jobs 
 that overstressed more than 5 pet but 
 less than 75 pet of the sample popula- 
 tion, and jobs that overstressed more 
 than 75 pet of the sample population. 
 That proportion of the sample population 
 for each job with JSI values greater than 
 1.5 was defined as the percentage over- 
 stressed for the job. 
 
 Table 2 shows the injury and cost sta- 
 tistics calculated for each job stress 
 category for the 1978 and 1982 studies 
 (3-4), respectively. As percentage over- 
 stressed increased, both injury rates and 
 costs increased. 
 
 TABLE 2. - Number of back injuries, number of disabling back injuries, days lost per 
 disabling back injury, and total expenses observed in various job stress categories 
 
 (Per 100 full-time-equivalent employees (200,000 exposure hours) caused by lifting) 
 
 Population 
 
 overstressed, ' 
 
 pet 
 
 Back 
 
 Disab- 
 ling 
 
 Days 
 lost 
 
 Total 
 expense 
 
 Population 
 
 overstressed, ' 
 
 pet 
 
 Back 
 
 Disab- 
 ling 
 
 Days 
 lost 
 
 Total 
 expense 
 
 1978 DATA, 63 JOBS 
 
 1982 DATA, 38 JOBS 
 
 <5 
 
 5.33 
 
 5.59 
 
 12.04 
 
 5.44 
 1.93 
 8.76 
 
 2.3 
 
 9.5 
 
 14.1 
 
 NA 
 NA 
 NA 
 
 <5 
 
 4.18 
 16.79 
 23.84 
 
 
 12.60 
 17.03 
 
 
 15.6 
 13.4 
 
 NA 
 
 <5, <75 
 
 >75 
 
 75, <75 
 
 >75 
 
 $35,092 
 $36,337 
 
 NA Not available. 
 
 'Defined as that proportion of the sample population for each job with JSI values 
 greater than 1.5. 
 
69 
 
 SIGNIFICANCE OF JOB SEVERITY INDEX 
 
 The JSI can be used as a tool for job 
 design and employee placement using the 
 relationship between JSI injury frequency 
 and/or job severity. For job design, the 
 following procedure can be followed: 
 
 Step 1. Describe the job as a series 
 of tasks, each having a weight distribu- 
 tion, average frequency, and ranges of 
 lift. 
 
 Step 2. Select an acceptable injury 
 frequency based on company policy. 
 
 Step 2. Determine the JSI for the per- 
 son if placed at a given job using the 
 JSI equation. 
 
 Step 3. Use this JSI to determine the 
 expected injury frequency rate if placed 
 on that job. Table 3 can again be 
 referenced. 
 
 Step 4. Make the screening and place- 
 ment decision based upon the acceptabil- 
 ity of the injury frequency rate deter- 
 mined in step 3. 
 
 Step 3. Select the population for 
 which the job is to be designed (for ex- 
 ample, 95 pet of the population, females, 
 etc.). 
 
 Step 4. Using step 2, determine the 
 corresponding JSI from the available 
 data. (Such data have been collected by 
 Ayoub {3), see table 3.) 
 
 Step 5. For each task (a) select the 
 smallest of the predicted lifting capaci- 
 ties using the appropriate equation from 
 table 1 (e.g. , if a task requires three 
 lifting ranges, select the smallest ca- 
 pacity of the three) and (b) calculate 
 the maximum design weight of lift for a 
 task using the JSI equation. 
 
 Step 6. If for a given task, the re- 
 quired weight of lift is above the maxi- 
 mum designed weight of lift, the job 
 should be redesigned in terms of required 
 range of lift, frequency of lift, etc. 
 
 To use the JSI for employee placement, 
 the following procedure should be 
 followed: 
 
 Step 1. Collect the information and 
 make the measurements necessary to pre- 
 dict the individual's lifting capacity 
 for each of the six lifting ranges us- 
 ing the predictive models given in ta- 
 ble 1. As noted, this information in- 
 cludes sex, weight, age, arm strength, 
 shoulder height, back strength, abdominal 
 depth, and dynamic endurance. 
 
 TABLE 3. - Expected frequency of total 
 injuries ' as a function of JSI (_3) , 
 warehousing industry 
 
 Frequency 
 expected^ 
 
 28. ...r 
 
 JSI 
 
 . 
 
 .0489 
 .1244 
 .1998 
 .2752 
 .3506 
 .4261 
 .5015 
 .5769 
 .6523 
 .7277 
 
 Frequency 
 expected^ 
 
 50 
 
 60 
 
 70 
 
 80 
 
 90 
 
 JSI 
 0.8032 
 
 30.... 
 
 
 1.1803 
 
 32. ... 
 
 
 1.5574 
 
 34.... 
 
 
 1.9345 
 
 36.... 
 
 
 2.3116 
 
 38.... 
 
 
 100 
 
 120 
 
 150 
 
 200 
 
 232 
 
 2.6888 
 
 40. ... 
 
 
 3.4430 
 
 42.. .. 
 
 
 4.5754 
 
 44.... 
 
 
 6.4599 
 
 46.... 
 
 
 7.6449 
 
 48 
 
 
 
 'Sum 
 
 tions. 
 
 2per 
 
 of 1 
 100 
 
 the 5 inju 
 full-time 
 
 ry type classifica- 
 -equivalent employees 
 
 (200,000 exposure hours). 
 
 The JSI has been successfully utilized 
 in a number of industrial settings. As 
 an example of the practical application 
 of the JSI, Liles (_7) performed an analy- 
 sis of selected jobs involving MMH for 
 Western Electric Corp. The analysis re- 
 sults for each job were presented in a 
 three-part summary and are presented in 
 tables 4 through 6. Table 4 presents the 
 job information necessary for the JSI 
 calculations. Table 5 gives the JSI's of 
 a large representative population of peo- 
 ple working in MMH activities. This por- 
 tion of the analysis results was conduct- 
 ed under the assumption that the large 
 
70 
 
 TABLE 4. - Job description information for job 99 (7) 
 
 Task 1: 
 
 Maximum weight lb.. 50 
 
 Lifting frequency 1.0000 
 
 Maximum box size... ft.. 5 
 Load center of gravity: 
 
 Initial 9 
 
 Terminal 15 
 
 Load height, in: 
 
 Initial 12-22 
 
 Terminal 25-35 
 
 Task: 
 
 Hours 8 
 
 Days 5 
 
 Task 2: 
 
 Maximum weight lb.. 30 
 
 Lifting frequency 1. 0000 
 
 Maximum box size... ft.. 2 
 Load center of gravity: 
 
 Initial 8 
 
 Terminal 8 
 
 Load height, in: 
 
 Initial 25-35 
 
 Terminal 30-40 
 
 Task: 
 
 Hours 8 
 
 Days 5 
 
 TABLE 5. - Statistics for representative 
 population assumed to be working in 
 job 99 (7) 
 
 
 Population 
 percentile 
 
 JSI 
 
 
 Male 
 
 Female 
 
 Task 1 
 
 95 
 50 
 
 5 
 
 95 
 
 50 
 
 5 
 
 3.70 
 
 1.27 
 
 .84 
 
 2.22 
 .76 
 .50 
 
 50.00 
 
 Task 2 
 
 2.61 
 1.29 
 
 30.00 
 
 
 1.56 
 .78 
 
 TABLE 6. - Actual JSI values for persons 
 working in job 99 (7) 
 
 Subject 
 
 Female. 
 Male. . . 
 
 JSI 
 
 2.1021 
 .8787 
 
 size of the assumed population would pro- 
 vide a better indicator of the JSI than 
 the small group of people actually work- 
 ing on the jobs. Finally, table 6 pre- 
 sents the JSI values for the people actu- 
 ally working at the particular job. 
 
 In comparing the data presented in 
 tables 5 and 6, it should be noted that 
 the JSI values for the representative 
 population of MMH workers (table 5) are 
 significantly larger than for the actual 
 population working in job 99. This would 
 imply that an employee placement proce- 
 dure of at least a subliminal level is 
 being carried out. Unfortunately for 
 
 industry, this nonf ormalized method of 
 employee placement is generally of a hit- 
 or-miss nature, and the misses in indus- 
 try often surface as injured workers. 
 The use of a formalized, empirically 
 based employee placement procedure (rath- 
 er than, for example, the supervisor de- 
 ciding a worker looks strong enough to 
 perform the job) such as the JSI could 
 potentially reduce the number of injuries 
 caused by the wrong worker being placed 
 on the wrong job. 
 
 Acceptable and unacceptable weights of 
 lift as determined through use of the JSI 
 can be compared with lifting guidelines 
 predicted using other procedures. Figure 
 6 compares the limits for a floor- 
 to-knuckle lift at various lifting fre- 
 quencies obtained using the JSI and using 
 the protocol recommended in the NIOSH 
 guide ( 12 ) for manual lifting. The maxi- 
 mum permissible limit (MPL) and action 
 limit (AL) lines generated using the 
 NIOSH equations correspond roughly with 
 the 2.25 and 1.125 JSI lines, respective- 
 ly, in that lifting tasks above 2.25 or 
 the MPL fall in the unacceptable range 
 (i.e., require engineering controls), 
 tasks below 1.125 or the AL represent a 
 nominal safety risk, and tasks falling 
 between the criterion limits (1.125-2.25, 
 AL-MPL) require administrative control. 
 It is apparent that the AL and, to a 
 lesser extent, the MPL are more conserva- 
 tive than the corresponding JSI lines; 
 this being particularly true for higher 
 frequencies of lift. 
 
SUMMARY 
 
 71 
 
 It can be said that the ratio of job 
 demand to the capacity of the worker does 
 affect the frequency and severity of in- 
 juries incurred during MMH activities. 
 Use of the JSI provides a means to con- 
 trol these injuries through redesign of 
 demand tasks and/or (as a last resort) 
 
 better placement of workers. Because of 
 the presence of MMH activities in the 
 mining industry, the JSI has the poten- 
 tial to reduce the frequency and severity 
 of MMH-related injuries in this indus- 
 trial area. 
 
 REFERENCES 
 
 1. Aghazadeh, F. Simulated Dynamic 
 Lifting Strength Models for Manual Lift- 
 ing. Unpublished Ph.D. Dissertation, 
 Texas Tech. University, Lubbock, TX, 
 1982; available upon request from M. M. 
 Ayoub, Texas Tech Univ., Lubbock, TX. 
 
 2. Ayoub, M. M. , N. J. Bethea, 
 M. Bobo, C. L. Burford, K. Caddel, K. 
 Intaranont, S. Morrissey, and J. Selan. 
 Biomechanics in Low Coal Mines contract 
 H0387022; for inf., contact S. J. Mor- 
 risey, Pittsburgh Res. Center, Pitts- 
 burgh, PA. 
 
 3. Ayoub, M. M. , N. J. Bethea, S. 
 Deivanayagam, S. S. Asfour, G. M. Bakken, 
 D. Liles, A. Mital, and M. Sherif. De- 
 termination and Modeling of Lifting Ca- 
 pacity. Final Rept. NIOSH, grant 5R010H- 
 00545-02, September 1978; available upon 
 request from M. M. Ayoub, Texas Tech. 
 Univ. , Lubbock, TX. 
 
 4. Ayoub, M. M. , D. Liles, S. S. As- 
 four, G. M. Bakken, A. Mital, and J. 
 Selan. Effects of Task Variables on 
 Lifting Capacity. Final Rept. NIOSH 
 grant 5R010H00798-04, August 1982; same 
 as ref. 3. 
 
 5. Ayoub, M. M. , J. L. Selan, C. L. 
 Burford, H. P. R. Rao, K. Intaranont, M. 
 Bobo, K. Caddel, and J. L. Smith. Bio- 
 mechanical and Work Physiology Study in 
 Underground Mining Excluding Low Coal. 
 Ongoing BuMines contract J0308058; for 
 
 inf., contact J. M. Peay, Pittsburgh Res. 
 Center, Pittsburgh, PA. 
 
 6. Ayoub, M. M. , J. L. Selan, W. Kar- 
 wowski, and H. P. R. Rao. Lifting Capac- 
 ity Determination. See preceding paper 
 in this proceedings. 
 
 7. Liles, D. Analysis of Selected 
 Materials Handling Activities for Western 
 Electric. Report to company, 1981; 
 available from M. M. Ayoub, Texas Tech. 
 Univ., Lubbock, TX. 
 
 8. National Safety Council. Accident 
 Facts. Chicago, IL, 1978. 
 
 9. Nordby, E. J. Epidemiology and 
 Diagnosis in Low Back Injury. J. Occupa- 
 tional Health and Safety, v. 50, No. 1, 
 1981. 
 
 10. Selan, J. L. , M. M. Ayoub, and 
 H. P. R. Rao. Manual Materials Handling 
 in the Mining Industry. Unpublished re- 
 port; available upon request from M. M. 
 Ayoub, Texas Tech. Univ., Lubbock, TX. 
 
 11. Snook, S. H., and V. M. Ciriello. 
 Low Back Pain Industry. Am. Soc. Safety 
 Eng. J., V. 17, No. 4, 1972, pp. 17-23. 
 
 12. U.S. Department of Health and Hu- 
 man Services. Work Practices Guide for 
 Manual Lifting. NIOSH, Pub. 81-122, 
 1981, 183 pp.; NTIS PB 82-178-948. 
 
72 
 
 I960 1970 1980 1990 
 
 YEAR 
 
 FIGURE 1. - Cost of trunk injuries over time (1). 
 
 (T 
 
 O 
 
 X 
 
 LU 
 
 cr 
 
 CO 
 O 
 
 a. 
 
 X 
 
 UJ 
 
 o 
 o 
 
 o" 
 
 o 
 
 CvJ 
 
 cr 
 
 UJ 
 
 a. 
 
 20 
 
 10 
 
 ra 
 
 i 
 
 .*-■' 
 
 A- 
 
 i 
 
 a"^ 
 
 .>^^ 
 
 i 
 
 .'V^ 
 
 
 .^^ 
 
 T? 
 
 JSI RANGE 
 
 FIGURE 2. - The incidence of back injuries 
 caused by lifting versus JSI. 
 
73 
 
 ir 
 I 20 
 
 •^ LlI 
 
 o tr 
 < 3 
 m t/> 
 o 
 o a 
 
 _1 1^ 
 
 <8 
 
 '-' C\i 
 QL 
 
 uj q: 
 
 QQ UJ 
 => CO 
 
 a: 
 
 3 
 
 I 5 
 
 10 
 
 5 - 
 
 1 1 
 
 n 
 / 
 
 
 
 - 
 
 .^ 
 
 .^ 
 
 ^^ 
 
 'p 
 
 
 0.- 
 
 \- 
 
 JSI RANGE 
 
 FIGURb 3. - The incidence of disabling back 
 injuries caused by lifting versus JSI, 
 
 JSI RANGE 
 
 FIGURE 4. - The severity of disabling back 
 injuries caused by lifting versus JSL 
 
 JSI RANGE 
 
 FIGURE 5. - The total expense of back injur- 
 ies caused by lifting versus JSI. 
 
 125 I 1 1 1 1 1 1 1 I r 
 
 Maximum 
 permissible 
 " limit 
 
 I 
 
 2345 6789 
 
 LIFTS PER MINUTE 
 
 FIGURE 6. - Comparison of lifting guides based 
 on JSI versus NIOSH (12) lifting guidelines. 
 
74 
 
 BACK INJURIES AND MAINTENANCE MATERIAL HANDLING IN LOW-SEAM COAL MINES 
 By Ernest J. Conway' and William W. Elliott2 
 
 INTRODUCTION 
 
 Accidents associated with the handling 
 of materials and supplies have tradition- 
 ally accounted for a large percentage of 
 all industrial lost-time injuries. The 
 National Safety Council reports that this 
 accident category is responsible for at 
 least 25 pet of all industrial accidents. 
 In the mining industry, an even higher 
 percentage of materials handling injuries 
 are noted. As table 1 suggests, these 
 statistics are relatively consistent 
 across various types of mining opera- 
 tions. Somewhat higher percentages, how- 
 ever, are noted for underground coal 
 mines and for metal processing plants. 
 
 TABLE 1. - Materials handling injuries 
 by industry by work location, January- 
 March 1982' 
 
 Coal mines: 
 
 Underground 
 
 Surface 
 
 Preparation plant.. 
 Metal mines: 
 
 Underground 
 
 Surface 
 
 Mills 
 
 Total or percent. 
 
 'Mine Injuries an 
 ly , January-March, 
 ment of Labor, Mine 
 Administration. 
 
 Handling 
 
 Lost time 
 
 injuries 
 
 injuries 
 
 Total 
 
 pet 
 
 1,115 
 
 3,211 
 
 34.7 
 
 175 
 
 628 
 
 28.0 
 
 68 
 
 233 
 
 29.0 
 
 93 
 
 337 
 
 27.5 
 
 51 
 
 150 
 
 34.0 
 
 71 
 
 193 
 
 36.7 
 
 1,573 
 
 4,752 
 
 33.1 
 
 d Worktime Quarter- 
 
 1982, U.S. Depart- 
 
 Safety and Health 
 
 ^Vice president. Canyon Research Corp., 
 Westlake Village, CA. 
 
 ^Fire systems engineer, Santa Barbara 
 Research Center, Subsidiary of Hughes 
 Aircraft Co., Santa Barbara, CA. 
 
 Table 2 summarizes manual materials 
 handling injuries in 26 mines at several 
 points in the mine supply cycle. It is 
 noted that the largest single source of 
 injury involves the movement of supplies 
 and components from the surface to the 
 point of use in the mine. This function, 
 however, may involve handling of the same 
 material two, three, or more times prior 
 to reaching the point of use. The second 
 largest category, which accounts for 
 approximately 26 pet of all injuries, 
 occurs during the actual use of the mate- 
 rials in mine maintenance or equipment 
 repair activities. These are the acci- 
 dents to be discussed in this paper. For 
 purposes of the following discussion, 
 materials handling shall be defined as 
 the lifting, pushing, pulling, or shovel- 
 ing of materials or components used dur- 
 ing equipment maintenance or during mine 
 maintenance activities. 
 
 TABLE 2. - Analysis of in-mine material 
 handling injuries for 26 mines 
 
 Injuries , 
 Handling mode pet 
 
 On-section manual handling of 
 equipment and or supplies 
 during production shift 11.2 
 
 Supply movement from surface 
 to point of use 49.5 
 
 Section move: Movement be- 
 tween working sections 13.0 
 
 Equipment maintenance: During 
 maintenance shift 16.3 
 
 Mine maintenance and handling 
 
 on maintenance shift 10.0 
 
 Total 100.0 
 
75 
 
 ACCIDENT REPORT ANALYSIS 
 
 In an effort to define the magnitude of 
 the materials handling injury problem in 
 underground coal mines, an analysis was 
 performed of over 75,000 accident reports 
 collected and reported in the Mine Safety 
 and Health Administration Health and 
 Safety Analysis Center (HSAC) data base 
 for a 3-yr period. 3 This review resulted 
 in the identification of 15,416 cases 
 that reportedly involved materials han- 
 dling activities. These materials han- 
 dling accident reports were then sorted 
 into the following four categories: 
 
 1. Part of body injured 
 
 2. Type of accident. 
 
 3. Source of injury 
 
 4. Nature of injury 
 
 Table 3 summarizes the 15,416 injury 
 reports by part of body affected. It is 
 observed that over 39 pet of these re- 
 ported injuries involved the middle and 
 lower back. This category represents a 
 larger percentage of materials of han- 
 dling injuries than the next six elements 
 combined. 
 
 Table 3 also summarizes the same 15,416 
 cases by type of accident. It is noted 
 that the largest single accident category 
 is overexertion while lifting. This fre- 
 quently involves the lifting of a com- 
 ponent (e.g., a shuttle car drive motor) 
 or mine supplies (e.g., rock dust bags, 
 etc. ) from the ground prior to use. 
 Likewise, it is noted that overexertion 
 pulling accounts for another 20.6 pet of 
 the total injuries. Combined, overexer- 
 tion type accidents account for more than 
 half of all the injuries. 
 
 ■^Ongoing BuMines contract HO1 13018; for 
 info. , contact R. L. Unger, Pittsburgh 
 Res. Center, Pittsburgh, PA. 
 
 TABLE 3. - Ranking of underground mine 
 maintenance material handling injuries 
 
 Rank 
 
 Element 
 
 PART OF BODY 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 11 
 
 12 
 
 13 
 
 14 
 
 15 
 
 16 
 
 17 
 
 18 
 
 NAp 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 11 
 
 NAp 
 
 NAp Not 
 NEC Not 
 
 Back 
 
 Finger 
 
 Hand 
 
 Foot 
 
 Hips 
 
 Knee 
 
 Shoulders 
 
 Eyes 
 
 Multiple parts. 
 
 Wrist , 
 
 Neck , 
 
 Chest , 
 
 Leg, NEC , 
 
 Arm, NEC , 
 
 Abdomen , 
 
 Head, NEC , 
 
 Toes , 
 
 Ankle , 
 
 Other , 
 
 ACCIDENT TYPE 
 
 Overexert, lift.... 
 
 Falling object 
 
 Overexert, NEC 
 
 Caught , NEC 
 
 Overexert, pull.... 
 
 Struck by, NEC 
 
 Stationary object.. 
 Caught , moving and 
 stationary. 
 
 Flying object 
 
 Rolling object 
 
 Overexert, wield... 
 Other 
 
 applicable, 
 elsewhere classified. 
 
 pet 
 
 39.7 
 18.3 
 4.9 
 4.8 
 4.0 
 3.6 
 3.1 
 2.8 
 1.8 
 1.5 
 1.5 
 1,4 
 1.4 
 1.3 
 1.3 
 1.0 
 1.0 
 1.0 
 <1.0 
 
 31.0 
 14.3 
 13.1 
 8.8 
 7.5 
 6.7 
 6.5 
 3.3 
 
 2.6 
 
 1.2 
 
 1.2 
 
 <1.0 
 
 When the materials handling accidents 
 are sorted on the basis of the source of 
 injury, an interesting distribution is 
 observed (table 4). As table 4 suggests, 
 a broad spectrum of components and mate- 
 rials are involved in the maintenance- 
 related handling injuries. As will be 
 discussed later, many of these elements 
 
76 
 
 would probably not have resulted in in- 
 juries if they were handled on the sur- 
 face instead of in the mine. This type 
 of distribution suggests that what is 
 handled may not be as important as where 
 and how it is handled. 
 
 TABLE 4. - Underground maintenance 
 handling injuries summarized by 
 source of injury 
 
 Rank 
 
 9.. 
 
 10. 
 11. 
 12. 
 13. 
 14. 
 15. 
 16. 
 17. 
 18. 
 19. 
 20. 
 21. 
 
 Element 
 
 Metal, NEC 
 
 Timber posts, cap 
 
 Broken rock, ore... 
 
 Electrical conduit 
 
 Steel rail 
 
 Belt conveyor 
 
 Metal components........ 
 
 Cement products 
 
 Wood items, NEC 
 
 Jacks 
 
 Rock bolts 
 
 Bags 
 
 Barrels , drum 
 
 Chains , ropes 
 
 Underground mine machine 
 
 Miscellaneous, NEC 
 
 Containers , NEC 
 
 Cribbing 
 
 Container, NEC 
 
 Blocking 
 
 Pumps, fans, NEC 
 
 pet 
 
 13.8 
 12.8 
 8.9 
 7.2 
 4.6 
 3.6 
 3.5 
 2.9 
 2.5 
 2.5 
 2.4 
 2.3 
 2.1 
 1.9 
 1.9 
 1.8 
 1.6 
 1.6 
 1.6 
 1.4 
 1.3 
 
 NEC Not elsewhere classified. 
 
 Perhaps the most revealing summary is 
 presented in table 5. This table summa- 
 rizes the underground materials handling 
 injuries on the basis of the number of 
 days lost. Not only do back injuries ac- 
 count for the largest percentage of the 
 injuries, but they account for an even 
 larger percentage of days lost from work. 
 This suggests that back injuries are 
 somewhat more serious than other types of 
 injuries. 
 
 In an effort to identify the specific 
 task being performed by the miner at 
 the time of the maintenance handling in- 
 jury, a second series of analyses were 
 performed for the narrative description 
 of 5,376 HSAC cases. These cases in- 
 volved only in-mine equipment or mine 
 maintenance tasks. These accidents were 
 sorted into the following categories: 
 
 1. Lifting or lowering 
 
 2. Carrying 
 
 3. Maneuvering 
 
 4. Other activity 
 
 TABLE 5. - Summary of 1978-80 underground 
 coal mine material handling accidents, 
 HSAC data 
 
 Part of 
 
 Injuries 
 
 Injuries involving 
 
 body 
 
 Total 
 
 pet 
 
 days lost 
 
 injured 
 
 Total 
 
 pet 
 
 Head 
 
 Neck 
 
 Shoulders 
 
 Arms 
 
 Wrists. . . 
 Hands .... 
 Fingers. . 
 Trunk. . . . 
 
 Back 
 
 Hips 
 
 Legs 
 
 Feet and 
 
 toes. . . . 
 Other. ... 
 
 889 
 230 
 474 
 451 
 226 
 752 
 
 2,813 
 589 
 
 6,119 
 617 
 
 1,079 
 
 880 
 291 
 
 5.8 
 1.5 
 3.1 
 2.9 
 1.5 
 4.9 
 
 18.3 
 3.8 
 
 39.7 
 4.0 
 7.0 
 
 5.7 
 1.8 
 
 487 
 201 
 400 
 335 
 165 
 512 
 
 1,673 
 494 
 
 5,606 
 400 
 920 
 
 736 
 253 
 
 4.0 
 1.6 
 3.3 
 2.7 
 1.4 
 4.2 
 
 13.7 
 4.1 
 
 46.0 
 3.3 
 7.6 
 
 6.0 
 2.1 
 
 Total.. 
 
 15,410 
 
 100.0 
 
 12,182 
 
 100.0 
 
 Table 6 identifies the miner's activity 
 and the items being handled at the time 
 of the accident for equipment maintenance 
 tasks. It is pointed out that lifting 
 and lowering of components accounted for 
 the majority of all the days lost. It is 
 also noted that oil drums and grease 
 cans , machine parts and tools are the 
 most frequently involved items. 
 
 Table 6 also summarizes the miner's ac- 
 tivity at the time of the accident by the 
 material handled during mine maintenance 
 activities. It is observed that lifting- 
 lowering of track rails and timbers are 
 involved with the largest number of days 
 lost from work. This can be anticipated 
 since rails and timbers have relatively 
 high unit weights and are awkward to han- 
 dle. Unfortunately, track laying and 
 timber handling is traditionally accom- 
 plished manually using only a few simple 
 handtools. 
 
77 
 
 TABLE 6. - 1978-80 underground coal mine material accidents, summarized 
 by activity and item being handled 
 
 Activity 
 
 Item 
 
 DURING EQUIPMENT MAINTENANCE ACCIDENTS 
 
 Lifting-lowering. 
 
 Do 
 
 Other activity... 
 Lifting-lowering, 
 
 Do 
 
 Do 
 
 Do 
 
 Maneuvering. . . . . , 
 
 Carrying 
 
 Dropping 
 
 Carrying 
 
 Other activity.., 
 
 Do , 
 
 Maneuvering , 
 
 Other activity.., 
 
 Carrying , 
 
 Other activity... 
 
 Oil drum, grease can, hydraulic oil. 
 
 Machine part, tool 
 
 do , 
 
 Pump, motor, gearbox, wheel unit..., 
 
 Cover plate, X-P cover , 
 
 Tire 
 
 Toolbox 
 
 Machine part, tool 
 
 Oil drum, grease can, hydraulic oil. 
 
 Machine part , tool 
 
 Pump, motor, gearbox, wheel unit..., 
 Tire 
 
 Oil drum, grease can, hydraulic oil. 
 Pump, motor, gearbox, wheel unit.... 
 
 Cover plate, X-P cover 
 
 Machine part , tool 
 
 Pump, motor, gearbox, wheel unit.... 
 
 DURING MINE MAINTENANCE ACCIDENTS 
 
 Lifting-lowering. 
 
 Do 
 
 Do 
 
 Other activity... 
 
 Maneuvering 
 
 Lifting-lowering. 
 Other activity... 
 
 Do 
 
 Lifting-lowering. 
 
 Dropping 
 
 Carrying 
 
 Do 
 
 Other activity... 
 Dropping 
 
 Do 
 
 Lifting-lowering. 
 
 Track, rail 
 
 Timber, cribbing, ties. 
 
 Crossbar, header 
 
 Timber, cribbing, ties. 
 
 Track rail 
 
 Other 
 
 Track rail 
 
 Crossbar, header 
 
 Stopping block , 
 
 Track rail , 
 
 Other , 
 
 Timber, cribbing, ties. 
 
 Stopping block , 
 
 Timber, cribbing, ties. 
 
 Stopping block , 
 
 Rock dust, cement bag. , 
 
 Days 
 lost 
 
 3,629 
 
 2,249 
 
 2,182 
 
 1,749 
 
 1,639 
 
 1,127 
 
 1,070 
 
 692 
 
 559 
 
 537 
 
 490 
 
 434 
 
 349 
 
 334 
 
 314 
 
 301 
 
 289 
 
 1,828 
 1,355 
 783 
 643 
 487 
 425 
 388 
 372 
 327 
 319 
 236 
 224 
 211 
 150 
 149 
 148 
 
 The above analysis has pointed out that 
 
 2. About 40 pet of these injuries in- 
 volve the middle or lower back. 
 
 3. Over 30 pet of the injuries result- 
 ed from overexertion while lifting or 
 lowering objects. 
 
 1. A majority of the in-mine injuries 
 involve materials handling activities and 
 account for about 34 pet of all lost-time 
 injuries. 
 
 CONTRIBUTING FACTOR IDENTIFICATION 
 
 in procedures can minimize the associated 
 risk to mine personnel. This is particu- 
 larly important for lower seam height 
 mines which tend to have more severe 
 
 Through examination of these accident 
 data, it is possible to identify factors 
 contributing to these injuries. By look- 
 ing at some of the biomechanical limita- 
 tions of the human body, it is possible 
 to identify areas where mechanization of 
 materials handling tasks and/or changes 
 
 material handling related back injuries. 4 
 ^Work cited in footnote 3. 
 
78 
 
 Why are there relatively higher numbers 
 and more severe back injuries in lower 
 seam mines? There are several factors 
 involved. The most important one, how- 
 ever, is the fact that the spine is de- 
 signed to carry a maximum load when the 
 miner is standing in an erect, upright 
 position. In fact, the cervical, thora- 
 cic, and lumbar curves in the spine are 
 designed to center the load being lift- 
 ed (including the body weight of the 
 individual) between the ball and the 
 heel of the foot. In the fully erect po- 
 sition, the human spine typically can 
 safely handle up to 100 pet of the per- 
 sons 's body weight for short periods of 
 t ime . 5 
 
 When the spine is in other than the 
 full erect position, however, the load 
 that it can safely handle decreases 
 sharply. This is the result of — 
 
 1. The load not being evenly distrib- 
 uted across the vertebra and the inter- 
 vertebral disk. 
 
 2. The muscles being strained simply 
 supporting the weight of the upper torso, 
 arms, and head. 
 
 3. The ligaments and tendons being 
 strained supporting the upper body weight 
 and guiding the body's motion. 
 
 More specifically, when the miner is 
 bending forward (as in a 48- to 60-in 
 seam height), the muscles of the back and 
 stomach, which are normally used to main- 
 tain balance, must now support the weight 
 of the head, upper torso, and arms from a 
 biomechanically disadvantaged position. 
 This amounts to a substantial amount of 
 weight if you consider that 
 
 2. The average arm up to the shoulder 
 weighs 12 to 15 lbs. 
 
 3. The upper torso minus the head, 
 neck, and arms weighs 70 to 90 lb. 
 
 The back and stomach muscles of the 
 typical 190-lb miner are supporting some- 
 what over 100 lb of "dead" upper body 
 weight when he or she leans forward ap- 
 proximately 45°. This moment of force 
 must be borne by the lower spine and typ- 
 ically acts on the lumbrosacral joint. 
 This simply means that the body itself 
 (spine, muscles, and ligaments) is in- 
 capable of handling as much nonbody 
 weight as when the person is standing in 
 a full upright position. In an improper 
 work position, a load weighing only 30 lb 
 combined with the weight of the upper 
 body components may produce a torque on 
 the lower spine exceeding 300 in* lb. The 
 latter is the lifting equivalent of quite 
 a severe lifting task. Hence, depending 
 upon the miner's build and physical con- 
 dition, from 50 to 90 pet of the back's 
 muscle strength may be used just to sup- 
 port the upper body weight. This sug- 
 gests that a person can only safely lift 
 considerably less than 50 pet of the 
 weight that could be lifted in a normal 
 erect position. This percentage is re- 
 duced even further if 
 
 1. The miner is sitting on his or her 
 knees or buttocks, thus eliminating the 
 shock-abosorbing effects of the knees and 
 ankles. 
 
 2. The lifting task requires movement 
 of the object from one side of the body 
 to the other with the feet or knees 
 (e.g., in a kneeling position) in a fixed 
 position. 
 
 1. The average head (without the neck) 
 weighs 20 to 30 lb. 
 
 3. The lifting task requires the 
 transporting of the center of mass away 
 from the body. 
 
 -'U.S. Department of Health and Human 
 Services. Work Practices Guide for Man- 
 ual Lifting. NIOSH Pub. 81-122, 1981, 
 183 pp.; PB 82-178-948. 
 
 4. The size of the object moves the 
 center of mass of the person-object away 
 from the body's own natural center of 
 gravity. 
 
79 
 
 Research has shown that a majority of 
 the low-back injuries actually occur upon 
 release of a heavy load rather than at 
 the moment it is picked up. The reason 
 for this is that when a load is lifted 
 the stress induced to the human body is 
 distributed over time (e.g., 0.75 to 1.50 
 sec). When the same load is released, 
 separation may take place in as little as 
 40 sec or one-twentieth of the time re- 
 quired to place the load on the spine. 
 This results from 
 
 1. Extreme stress induced by muscle 
 action required to reestablish the body's 
 center of balance. 
 
 2. Sharply increased musculoskeletal 
 loading on the vertebra while attempting 
 to regain balance. 
 
 To make matters worse, the closer the 
 miner's body is to the floor (i.e., 
 stooped forward 90°), the greater the 
 musculoskeletal stress. 
 
 As table 7 illustrates, many of the 
 materials handling tasks performed during 
 mine or equipment maintenance involve the 
 lifting or handling of items that exceed 
 safe lifting weights for persons not in a 
 full upright position. 
 
 TABLE 7. - Weight of frequently handled components 
 
 I Unit weight, lb | Frequency | 
 
 Description 
 
 Tools 
 
 EQUIPMENT MAINTENANCE 
 
 Major component replacement. 
 
 Component replacement 
 
 Minor component replacement. 
 Lubrication and servicing. . , 
 
 Move workers' tool , 
 
 Repair by welding 
 
 Change tire 
 
 Repair electrical cable 
 
 Access permissible enclosure. 
 
 200-2,000 
 
 50- 
 
 5- 
 
 5- 
 
 50- 
 
 50- 
 
 200 
 
 50 
 
 50 
 
 200 
 
 200 
 
 50- 200 
 
 1- 5 
 
 50- 200 
 
 Monthly 
 Weekly. 
 Daily.. 
 . . .do. . 
 Monthly 
 Daily.. 
 
 Weekly. 
 Daily. . 
 . . .do. . 
 
 Jacks , come-alongs . 
 Handtools. 
 
 Do. 
 Pails, 5-gal cans. 
 Toolbox. 
 Cutting and welding 
 
 equipment. 
 Jack. 
 Handtools. 
 
 Do. 
 
 MINE MAINTENANCE 
 
 Set props and crossbars. • 
 
 200- 
 
 500 
 
 to 20 
 per day. 
 
 Saw , axe . 
 
 
 
 Bui. Id s topping walls ••••••••••••••• 
 
 50- 
 
 100 
 
 2 per day. 
 Monthly. . . 
 
 Axe. 
 
 Build ventilation doors 
 
 5- 
 
 50 
 
 Handtools 
 
 Build cribs •••• • 
 
 50- 
 100-1 
 
 100 
 ,000 
 
 Daily 
 
 Monthly. . . 
 
 Axe. 
 
 Install track ••••••••••••• 
 
 Handtools, sledge- 
 
 
 hammer, pry bars. 
 
 Build overcasts •••••••••••••••••••• 
 
 200- 
 
 500 
 
 Semiannual 
 
 Handtools, axe. 
 
 
 sledgehammer, pry 
 
 
 
 
 
 bars. 
 
 Tn t? t" fl 1 1 wp tPT* ninp^ DiiTnns .••>>•>>> 
 
 50- 
 
 100 
 
 Weekly. . . . 
 Semiannual 
 
 Handtools. 
 
 Install electrical power boxes 
 
 200- 
 
 500 
 
 Come-alongs , hand- 
 
 
 
 
 
 tools, scoop. 
 
 RopIc Hitcit hflpic pntries- .....>•••••• 
 
 50- 
 5- 
 
 100 
 50 
 
 Daily 
 
 . . .do 
 
 None. 
 
 Clean up rib trash, rock falls. 
 
 Shovel, scoop. 
 
 etc. 
 
 
 
 
 
 Build plank roadways through wet 
 
 50- 
 
 100 
 
 Semiannual 
 
 Scoop. 
 
 areas. 
 
 
 
 
 
80 
 
 SUMMARY 
 
 What are the implications of these 
 findings for materials handling in lower 
 seam mines? First, with this understand- 
 ing of the material handling tasks that 
 must be performed and the limitations of 
 the human spine, innovative approaches to 
 the materials handling problem can be 
 sought. As reported in another paper in 
 this proceedings , the Bureau of Mines is 
 currently developing a number of innova- 
 tive handling devices. 
 
 Secondly, improved materials handling 
 procedures and practices need to be de- 
 veloped. The straight-back lifting tech- 
 nique is simply not effective in mines 
 where the miner cannot stand upright. 
 Research is needed to find an alterna- 
 tive approach. Likewise, procedures that 
 
 better utilize the tools and equipment 
 found in the mine environment to do the 
 materials handling need to be identified, 
 thereby eliminating stress on the miner's 
 back. 
 
 Third, equipment used in mines needs to 
 be designed so that it can be properly 
 and safely maintained in the restrictive 
 mine environment. The size and weight of 
 supplies and materials used in mine main- 
 tenance needs to be reduced to ensure 
 that they can be "safely" handled by the 
 miner. 
 
 Finally, every miner must understand 
 the limitations of the human back and he 
 or she must take the precautions neces- 
 sary to prevent injury. 
 
81 
 
 TRAINING PROCEDURES TO REDUCE LOW BACK INJURIES 
 By Nancy C. Selby ' 
 
 ABSTRACT 
 
 Many back, injuries can be avoided, as 
 can chronic back pain. However, individ- 
 uals need to have enough information to 
 be able to understand how to protect 
 themselves. Safety information must be 
 presented in a manner that is relative to 
 individuals' environment and educational 
 level. Since most back injuries do not 
 occur on the job, first aid and home 
 
 activities must be included in training 
 programs. Lifting instructions are only 
 a small part of total effective injury 
 prevention; proper sitting, standing, 
 pushing, pulling, and turning procedures 
 must also be included. The blue collar 
 worker can and will take responsibility 
 for his or her own back care with proper 
 training. 
 
 INTRODUCTION 
 
 Second only to the common cold, back 
 injuries and back pain are the most fre- 
 quent problem in the work force in the 
 United States. Over 75 pet of the popu- 
 lation suffers from back pain at some 
 point in time. Back pain interferes with 
 worklife and social habits. In 1980, it 
 accounted for 93 million lost-time days, 
 as well as $5 billion in medical costs 
 and $12 billion in legal and insurance 
 fees (11).2 These figures have risen in 
 
 the past 2 yrs. Back injuries may ac- 
 count for only 25 pet of all injuries, 
 but cost over 65 pet of the dollars 
 spent. Back pain and back injuries have 
 become one of the most expensive health 
 problems in the mining industry just like 
 every other industry in the United 
 States. Unfortunately, knowing that 
 "everybody has it" does not alleviate the 
 discomfort or the frustration that accom- 
 panies back pain. 
 
 DISCUSSION 
 
 Back injuries are frustrating because 
 they are so difficult to identify, diag- 
 nose, and treat. Differentiation between 
 a "real" injury and a "supposed" injury 
 is challenging to the medical community 
 as well as to industry. It is not the 
 kind of injury that can be casted and be 
 healed in a certain length of time (_8 ) . 
 Back injuries become a problem of balance 
 sheets and productivity versus worker's 
 compensation premiums and lost-time days. 
 
 In the underground coal mining indus- 
 try, an average of 2,500 back injuries 
 per year occurred between 1977 and 1981. 
 If the average cost of a back injury is 
 $5,000, a yearly expenditure could be 
 
 ^Director, Spine Education Center, Dal- 
 las, TX. 
 
 ^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this paper. 
 
 over $12 million. Of course, not all 
 back injuries cost $5,000, but some cost 
 much more (12). This figure does not in- 
 clude those individuals who undergo sur- 
 gery or have long-term problems. 
 
 Since back injuries are a fact of life, 
 a safety director or personnel manager 
 with safety-related duties becomes an in- 
 tegral part of the team that tries to 
 oversee the problems. Unfortunately, 
 that individual is usually consumed with 
 paperwork and has neither the time nor 
 budget to initiate an effective program. 
 So he or she turns the entire dilemma 
 over to the supervisors. Supervisors may 
 be very knowledgeable about mines and 
 mining, techniques and equipment, but 
 they rarely have experience in safety and 
 injury prevention. Yet, they are the 
 people who are made ultimately responsi- 
 ble for every back injury on the job. 
 There is no way they can stop the back 
 
82 
 
 pain problem unless they have adequate 
 training and management's support ( 15 ) . 
 
 It is not unusual for a typical safety 
 program to allocate 0.04 pet of an entire 
 budget to safety, which translates to 
 $50,000 if the company has a yearly oper- 
 ating budget of $130 million (_3 ) . It is 
 definitely time to modify the present 
 system. Back injuries alone represent a 
 costly liability. Training techniques 
 must also be modified to stimulate the 
 individuals who are doing the work. We 
 must remember that all of us are much 
 more highly educated and exposed through 
 the television media than we once were. 
 The American worker expects and should 
 receive training that is relevant to his 
 or her situation. 
 
 The concept of educating individuals to 
 be responsible for their own health care 
 has surfaced in recent years. Extensive 
 studies have determined that education 
 has been the key factor in helping hemo- 
 philiacs and diabetics control their 
 diseases successfully (13). People with 
 back pain have not had much information 
 available to them, so they have been un- 
 able to control their problems. Back ed- 
 ucation and "back school" began in Sweden 
 in 1970. In a triple blind study, there 
 was substantial evidence indicating that 
 education returned patients to work soon- 
 er than regular physical therapy modali- 
 ties (_1_) . Also, recurring absence from 
 work was reduced. 
 
 The group incurring back injuries are 
 those individuals who are doing the ac- 
 tual labor, not the supervisors. There- 
 fore, it is important that the workers be 
 trained using appropriate techniques and 
 materials. Supervisor participation and 
 management support is essential for ef- 
 fective results. If given applicable in- 
 formation, miners will be able to take 
 responsibility for their own back care. 
 
 The program content found to be most 
 effective is a comprehensive one that 
 consists of information that incorporates 
 several topics as they relate to the 
 person working in a mine and their poten- 
 tial back problems. 
 
 People cannot be expected to take care 
 of their back unless they have some un- 
 derstanding of anatomy {8). We have a 
 spine for two reasons; one is for sup- 
 port. The other function of the spine is 
 to protect the spinal cord. 
 
 We have a number of anatomical parts 
 that affect the way we feel, but the most 
 common long-term injury involves the 
 disks. Disks rest between the 24 verte- 
 brae in our backs. Disks are the shock 
 absorbers of our bodies, just like we 
 have shock absorbers in our cars. An ef- 
 fective training program will use analo- 
 gies that are easily understood. For ex- 
 ample, disks look a lot like a jelly 
 doughnut; crusty on the outside with jel- 
 ly on the inside. And everyone under- 
 stands what happens if a jelly doughnut 
 is crushed; it leaks, just like a disk 
 does when it is crushed. Unfortunately, 
 when a disk herniates, that jelly may in- 
 terfere with the nerves and cause pain 
 and neurological deficits that will lead 
 to surgery. A ruptured or herniated 
 disk is the most common reason for back 
 surgery. 
 
 If we are interested in avoiding disk 
 herniation, it is necessary to understand 
 disk pressure. Different body positions 
 put more or less pressure on the low back 
 area; extensive studies from Sweden have 
 demonstrated this. For example, a person 
 who stands with knees locked, bent for- 
 ward, will put 200 lb of pressure on the 
 low back area (fig. 1). An individual 
 who sits incorrectly will do the same 
 thing. However, if we can reeducate that 
 person to sit with arms and back support- 
 ed and knees higher than hips, we can cut 
 that disk pressure in half. When lift- 
 ing, a person who holds material a fore- 
 arm's length away from his or her body 
 will put 10 times more pressure on the 
 low back than if that same object is held 
 close. Fortunately we can put ourselves 
 in positions that are comfortable as well 
 as beneficial. Lying on your back with 
 your feet on a stool puts only 25 lb of 
 pressure on the low back (fig. 2). For 
 this reason, it is called the resting 
 position (7). 
 
83 
 
 Pressure on the back is directly re- 
 lated to body mechanics (6). Body me- 
 chanics is not just lifting. It is sit- 
 ting, standing, bending, stooping, reach- 
 ing, and turning, as well as lifting. In 
 employee training, a giant inadequacy has 
 been the neglect to educate the worker 
 about job-related situations other than 
 lifting. 
 
 For example, there are two tribes in 
 the world that have no incidence of back 
 pain: One is in Mexico, and one is in 
 Africa. Apparently, they do not have 
 back pain because they do not spend much 
 time sitting. Everyone in this country 
 spends a great deal of time sitting, 
 whether at their job or at home watching 
 television, and that is contributing to 
 the back pain problem (11). 
 
 We know that absorption of informa- 
 tion is directly related to understand- 
 ing the subject matter presented ( 10 , 
 14). Obviously then, a back injury pre- 
 vention program for miners should uti- 
 lize visuals of miners in their job 
 situation. 
 
 Sitting with knees higher than hips 
 takes pressure off the back in situations 
 that require sitting. Getting close to 
 the worksite and working straight ahead 
 takes pressure off the low back area. 
 Getting down to the level of the work is 
 as important as staying close when reach- 
 ing. However, miners have a difficult 
 problem because they are forced to stay 
 in that position for long periods of time 
 (12) . Protecting their backs may con- 
 tribute to knee problems. 
 
 Standing with knees locked may not 
 cause a back injury, but it can give 
 you a very tired back by the end of the 
 day. It is recommended that a person 
 who stands all day put one foot slightly 
 in front of the other with knees slight- 
 ly bent. This gives the individual a 
 wider base of support so that the back 
 is not as likely to be stressed. If a 
 piece of equipment is available, putting 
 one foot up will take even more pres- 
 sure off the back. Bars have railings 
 for back comfort while standing and 
 drinking. 
 
 Ergonomics plays an important role in 
 back injury prevention (6^) . Look for 
 simple modifications to install to make 
 employees more comfortable. 
 
 Other body mechanics techniques that 
 should be discussed are pushing, pull- 
 ing, lifting, and pivoting. Pushing is 
 usually more desirable than pulling. An 
 accident that occurs with frequency is 
 pulling with feet parallel — an individual 
 using only his or her back — and a mechan- 
 ical device close by. 
 
 Lifting, like other jobs, can be done 
 in several ways. The person handling ma- 
 terial should be as close as possible to 
 the object. This is the most important 
 concept. Lifting can be accomplished by 
 putting one knee down or squatting. It 
 is important that the legs be used for 
 leverage, not the back (fig. 3). Not 
 everyone can lift the same way. People 
 and material come in different sizes and 
 should be handled accordingly. These 
 different options should be demonstrated, 
 discussed, and practiced at the time of 
 training. Learning to pivot rather than 
 twist is particularly helpful. 
 
 Employees need to know how to modify 
 their body mechanics and why. It is 
 important that employees understand the 
 benefits of using good body mechanics 
 and the disadvantages if they do not. 
 With this knowledge, they can think 
 about a job, their back, and the best 
 way to avoid pressure when performing 
 that job (8). Utilizing mechanical de- 
 vices whenever possible will also dimin- 
 ish injuries. 
 
 Injuries occur at home, too, and be- 
 cause of our system, they may become a 
 Monday morning worker's compensation ac- 
 cident. Therefore, it is important for 
 the miners to be able to transfer these 
 new techniques to a home situation. Even 
 shaving and brushing teeth can cause back 
 pain. An alternative is to bend the 
 knees into the sink or put a foot up in 
 the cabinet. Doing yard work incorrect- 
 ly can cause back pain; driving long 
 distances in the car can, too. Most 
 Americans drive with the seat too far 
 away with knees dropped below hip level. 
 
84 
 
 Moving the seat forward a notch may alle- 
 viate the problem. An inexpensive back 
 support can be created by rolling up a 
 towel. There are also two-person jobs at 
 home, and it is important that safe tech- 
 niques be practiced off the job. 
 
 Considering that the majority of the 
 population has back pain some time in 
 their life, it is sensible to give every- 
 one a workable first aid treatment for 
 back pain. Most people suffer from back 
 pain that involves muscle spasm. The 
 most effective treatment found is ice 
 massage, stretching, and the use of as- 
 pirin. Muscles that are tight and tense 
 are in spasm. Ice massage will numb the 
 area and allow the knees to be brought up 
 toward the chest to stretch those muscles 
 out to their normal limits (4, 9). Mus- 
 cles only have the capability to contract 
 by themselves. If you have ever experi- 
 enced a cramp in the foot in the middle 
 of the night, you know you have to walk 
 on it or rub it. Muscles in the back are 
 like that. They have to be stretched to 
 their normal limits. The use of ice will 
 allow that to occur. Aspirin is a superb 
 anti-inflammatory and will help control 
 pain. 
 
 Men and women who have ulcers or bleed- 
 ing problems should not take aspirin, but 
 most people can take aspirin several 
 times a day as long as they drink plenty 
 of fluids. Directions should be included 
 with the general information given to the 
 employees at training. 
 
 It has been determined that for every 
 day a person is immobile, it takes 4 days 
 to rehabilitate that individual to normal 
 function. Therefore, mobility is impor- 
 tant. Light duty will prevent the em- 
 ployee from behavioral changes. Fur- 
 thermore, a person who is at bedrest for 
 several weeks becomes weak and is very 
 likely to have an injury the first day on 
 the job since theri muscle tone is poor. 
 Maintenance of muscle strength is very 
 critical when the worker must return to a 
 job situation (8). Although the majority 
 of the injured miners reported in the 
 underground coal mining statistics re- 
 turned to the job in 3 weeks or less, it 
 is important to consider the rapidity of 
 
 the deterioration of strength if a miner 
 has been in bed for several days. Physi- 
 cal fitness affects the occurrence of 
 back injuries, so the injured employees 
 should be given instructions in strength- 
 ening and stretching exercises and should 
 be encouraged to do these before return- 
 ing to work (2). 
 
 It follows, therefore, that the person 
 who is in poor physical condition may 
 have weight and posture problems and 
 could be a candidate for an injury. 
 Stress may also affect the back, causing 
 muscles to tighten which may lead to mus- 
 cle spasm. A physical fitness program 
 may diminish many of these problems. 
 
 In November 1982, two psychologists 
 from North Texas State University con- 
 ducted a study involving eight industries 
 and approximately 1,500 employees. One 
 hour of back injury prevention education 
 was provided to the employees of these 
 industries. The programs were given in 
 small groups at the jobsites and were 
 customized for the specific industry and 
 their needs. Companies participating in 
 the evaluation were representative of 
 both light and heavy industry. Both 
 safety directors and participants were 
 asked to respond. The employee response 
 was a random sampling. The results were 
 as follows: Safety directors report a 
 40-pct reduction in lost-time days the 
 year following the presentation with a 
 decrease in medical insurance expenses in 
 three of the companies. There was an in- 
 crease in numbers of reported injuries, 
 but those participating in the program 
 reported fewer injuries. The partici- 
 pants reported an 86-pct decrease in 
 lost-time days and a 63-pct reduction in 
 injuries. Lawlis and Hennig (_5) reasoned 
 that the reported increase in back inju- 
 ries was primarily due to the changes of 
 management's perception of back injuries 
 and the employees' willingness to report 
 early injury and accept early treatment. 
 The large reduction in lost time would 
 support that premise. 
 
 Although each program was customized, 
 all employees received the same format of 
 information. Followup material included 
 posters that were placed in common areas 
 
85 
 
 and reminder cards placed in paychecks 6 
 months following the program. A short 
 
 refresher course was offered 1 yr follow- 
 ing the initial presentation. 
 
 CONCLUSIONS 
 
 Back injuries are a major health prob- 
 lem in the United States, but can be pre- 
 vented and controlled through education 
 and training if the material is designed 
 for the person on the job. It must 
 be informative, interesting, fast-moving, 
 and relative. Body mechanics concepts 
 must be emphasized in different ways so 
 the individual can adopt the positions 
 that work best for his or her situation 
 both at work and at home (14) . Use of 
 the first aid treatment should be encour- 
 aged at the first sign of back strain. 
 Light-duty programs should be initiated 
 
 to keep the individual mobile and in 
 touch with his peers and management. 
 Practical demonstration is important, but 
 actual participation in sitting, stand- 
 ing, lifting, and pivoting procedures is 
 essential. The trainer must be well- 
 prepared before the employee can be ex- 
 pected to retain the information present- 
 ed. Followup is a mandatory part of any 
 safety program. If employees are given 
 appropriate information, they can and 
 will take responsibility for their own 
 back health care (13). 
 
 REFERENCES 
 
 1. Bergquist-Ullman, M. , and U. Lars- 
 son. Acute Low Back Pain in Industry. 
 Acta Orthopaedic Scandinavia, Suppl. 170, 
 1977, pp. 1-117. 
 
 2. Cady, L. D. Strength and Fit- 
 ness and Subsequent Back Injuries in 
 Firefighters. J. of Occupational Med., 
 V. 21, 1979, pp. 269-273. 
 
 3. Carroll, B. J. An effective Safe- 
 ty Program Without Top Managment Sup- 
 port. Professional Safety, July 1982, 
 pp. 20-24. 
 
 4. Grant, R. E. Massage With Ice in 
 the Treatment of Painful Conditions of 
 the Musculoskeletal System. Phys. Med. 
 Rehab., v. 45, 1964, pp. 223-238. 
 
 5. Lawlis, G. F. , and E. G. Hennig, 
 Jr. An Evaluation of Individualized Edu- 
 cational Services for the Prevention of 
 Industrial Back Injuries Unpublished Pro- 
 gram Evaluation for Spine Education Cen- 
 ter, Dallas, TX, November 1982; available 
 upon request from N. C. Selby, Spine Ed. 
 Center, Dallas, TX. 
 
 6. Manuele, F. A. Work Practices 
 Guide for Manual Lifting. National Safe- 
 ty News, October 1982. 
 
 7. Nachemson, A. L. Low Back Pain — 
 Its Etiology and Treatment. Clinical 
 Medicine, 1971, pp. 18-23. 
 
 8. Selby, D. K. Conservative Care of 
 Nonspecific Low Back Pain. Orthopedic 
 Clinics of North America, v. 13, No. 3, 
 July 1982, pp. 427-437. 
 
 9. Showman, J. , and L. T. Wedlick. 
 The Use of Cold Instead of Heat for the 
 Relief of Muscle Spasm. Med. J. of Aus- 
 tralia, V. 2, 1964, pp. 612-614. 
 
 10. This, L. Results-Oriented Train- 
 ing Design. Training and Dev. J. , June 
 1980, pp. 14-22. 
 
 11. Time (Chicago). That Aching Back. 
 July 14, 1980, pp. 30-34. 
 
 12. U.S. Mine Safety and Health Admin- 
 istration. Injury Experience in Coal 
 Mining, 1978-1981. MSHA IR's 1112, 1122, 
 1133, 1138. 
 
 13. White, A. H. Conservative Care — 
 California. The Challenge of the Lumbar 
 Spine, Conference Proceedings, Dallas, 
 TX, Dec. 10-12, 1981. 
 
 14. Zemke, R. , and S. Zemke. 30 
 Things We Know for Sure About Adult 
 Learning. Training/HRD, June 1981, pp. 
 45-52. 
 
 15. Zenger, J. The Painful Turnabout 
 in Training. Training and Dev. J., De- 
 cember 1980, pp. 36-49. 
 
86 
 
 200 / 
 
 FIGURE 1. - This position will put 200 lb of pressure on the 
 back. 
 
87 
 
 FIGURE 2. - Position showing only 25 lb of pressure on the low bock. 
 
 \ 
 
 I- ■ "^ 
 
 FIGURE 3. - Legs should be used for leverage, not the back 
 
88 
 
 A MANUAL MATERIALS HANDLING (MMH) TRAINING PROGRAM FOR THE MINING INDUSTRY 
 
 By Daniel J. Connelly 1 
 
 ABSTRACT 
 
 Back injuries have been a continuous 
 and increasing problem in the mining 
 industry. Accident statistics reveal 
 that most back, injuries occur during man- 
 ual materials handling activities. Vari- 
 ous methods have been attempted to con- 
 trol these accidents. Training in safe 
 
 materials handling is one approach that 
 has been used over the years. This paper 
 provides a number of general recommenda- 
 tions and specific examples to assist 
 training personnel in the mining industry 
 to develop a manual materials handling 
 training course to reduce back injuries. 
 
 INTRODUCTION 
 
 Back injuries have been a continuous 
 and increasing problem in the mining 
 industry (table 1). In coal mining, 
 for example, approximately 20 pet of all 
 injuries are back injuries. Consequent- 
 ly, a significant percentage of the total 
 nonfatal lost workdays are due to back 
 injuries (table 2). Likewise, the costs 
 of back injuries to the mining industry 
 are significant. 
 
 A review of accident statistics show 
 the majority of back injuries reported by 
 the mining industry are the result of ma- 
 terials handling accidents (table 3). 
 The accident classification, handling 
 materials, is defined as an accident re- 
 
 ^ Safety specialist, Pittsburgh Research 
 Center, Bureau of Mines, Pittsburgh, PA. 
 
 lated to handling packaged or loose ma- 
 terial while lifting, pulling, pushing, 
 or shoveling (10). 2 
 
 Miners involved in materials handling 
 activities, whether underground or on 
 the surface, are exposed to a number of 
 potential accident situations. Many fac- 
 tors contribute to the hazards of ma- 
 terials handling. The major components 
 are the worker, the task, the materials 
 handled, and the work environment. If 
 materials are not handled properly, the 
 result can be a lost-time injury, most 
 likely occurring to the back. 
 
 ^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this paper. 
 
 TABLE 1. - Total injuries, back injuries, and percentage 
 of back injuries at coal, metal, and nonmetal mines 
 in the United States, 1978-80 (10-12) 
 
 Coal mines: 
 
 Total Injuries 
 
 Back Injuries 
 
 Back injuries pet, 
 
 Metal mines: 
 
 Total injuries 
 
 Back Injuries 
 
 Back injuries pet, 
 
 Nonmetal mines: 
 
 Total injuries , 
 
 Back injuries 
 
 Back injuries pet. 
 
 1978 
 
 20,203 
 
 3,762 
 
 18.6 
 
 8,713 
 
 1,247 
 
 14.3 
 
 3,844 
 
 664 
 
 17.3 
 
 1979 
 
 23,677 
 
 4,948 
 
 2.9 
 
 9,619 
 
 1,428 
 
 14.8 
 
 3,497 
 
 608 
 
 17.4 
 
 1980 
 
 22,723 
 
 5,111 
 
 22.5 
 
 8,028 
 
 1,246 
 
 15.5 
 
 3,066 
 
 607 
 
 19.8 
 
 1981 
 
 18,821 
 
 4,119 
 
 21.9 
 
 7,570 
 
 1,153 
 
 15.2 
 
 2,697 
 
 461 
 
 17.1 
 
TABLE 2. - Total nonfatal lost workdays, nonfatal lost workdays 
 due to back injuries and percentage at coal, metal and 
 nonmetal mines in the United States 1978-80 (1-3) 
 
 89 
 
 1978 
 
 1979 
 
 1980 
 
 1981 
 
 Coal mines: 
 
 Total NFDL , 
 
 NFDL-back injuries , 
 
 Back injuries pet, 
 
 Metal mines: 
 
 Total NFDL 
 
 NFDL-back injuries 
 
 Back injuries pet, 
 
 Nonmetal mines: 
 
 Total NFDL 
 
 NFDL-back injuries 
 
 Back injuries pet 
 
 NFDL Nonfatal days lost. 
 
 494,464 
 
 113,817 
 
 23.0 
 
 148,034 
 
 21,481 
 
 14.5 
 
 78,146 
 
 11,667 
 
 14.9 
 
 662,704 
 
 155,583 
 
 23.5 
 
 187,092 
 
 27,428 
 
 14.7 
 
 75,053 
 
 15,557 
 
 20.7 
 
 662,911 
 
 193,806 
 
 29.2 
 
 179,081 
 
 40,932 
 
 22.9 
 
 58,363 
 
 11,699 
 
 20.0 
 
 616,342 
 
 176,065 
 
 28.6 
 
 149,510 
 
 25,049 
 
 16.8 
 
 58, ,218 
 
 10,521 
 
 18.1 
 
 TABLE 3. - Total back injuries, materials handling' back 
 injuries, and percentage at coal, metal, and nonmetal 
 mines in the United States 1978-80 (10-12) 
 
 Coal mines: 
 
 Back injuries 
 
 Materials handling back 
 
 injuries 
 
 Back injuries pet. 
 
 Metal mines: 
 
 Back injuries 
 
 Materials handling back 
 
 injuries 
 
 Back injuries ..pet. 
 
 Nonmetal mines: 
 
 Back injuries 
 
 Materials handling back 
 
 injuries 
 
 Back injuries pet. 
 
 1978 
 
 3,762 
 
 2,139 
 56.9 
 
 1,247 
 
 636 
 51.0 
 
 664 
 
 380 
 57.2 
 
 1979 
 
 4,948 
 
 2,932 
 59.3 
 
 1,428 
 
 749 
 52.5 
 
 608 
 
 386 
 63.5 
 
 1980 
 
 5,111 
 
 3,008 
 58.9 
 
 1,246 
 
 654 
 52.5 
 
 607 
 
 375 
 61.8 
 
 1981 
 
 4,119 
 
 2,427 
 58.9 
 
 1,153 
 
 597 
 51.8 
 
 461 
 
 271 
 58.8 
 
 'Handling materials accidents are defined as accidents related 
 to handling packaged or loose material while lifting, pulling, 
 pushing, or shoveling. 
 
 In addition to back injuries, there are 
 other types of injuries associated with 
 materials handling accidents. These 
 other injuries, such as bruises and cuts 
 
 of the fingers and hands , account for a 
 minor percentage of the total costs of 
 injuries arising from materials handling. 
 
90 
 
 WHAT CAN BE DONE? 
 
 In many mining companies, frustrations 
 over the seemingly insoluble back injury 
 and materials handling problems create 
 attitudes that further aggravate the 
 problems. Several positive steps can be 
 taken to control the hazards. Tradition- 
 ally, the prevention of back injuries has 
 been attempted by 
 
 1. Careful selection and placement of 
 workers. 
 
 2. Training in safe lifting. 
 
 3. Designing the job to fit the worker 
 
 (Z). 
 
 Training for manual materials handling 
 in the mining industry is the main topic 
 of this paper. Training in safe handling 
 methods alone will not solve the back in- 
 jury problem. The problems of back inju- 
 ries and materials handling are multidi- 
 mensional in nature. Training is only 
 one approach that should be used in com- 
 bination with other control methods, such 
 as job redesign, and worker selection and 
 placement (1). 
 
 TRAINING TO CHANGE BEHAVIOR 
 
 The ultimate objective of any training 
 program is to change behavior of people. 
 That is, to cause them to do their jobs 
 effectively and correctly (i.e., safely). 
 However, there are many factors that in- 
 fluence human behavior on the job. Be- 
 havioral change can be insensitive to 
 
 training if other factors (i.e., environ- 
 mental, managerial, physiological, so- 
 cial, etc.) predominate in determining 
 the way people are behaving (6). There- 
 fore, training can be identified as one 
 of many variables to consider and control 
 to achieve behavioral change. 
 
 TRAINING TO REDUCE BACK INJURIES 
 
 Training for the purpose of reduc- 
 ing back injuries has been conducted 
 throughout industry for many years. Even 
 though, few in-depth studies have been 
 made to determine the effectiveness of 
 lifting and materials handling training 
 (8^, p. 176). 
 
 The importance of training in manual 
 materials handling (MMH) , however, has 
 
 been generally accepted, and is likely to 
 continue. What is needed is a clear def- 
 inition of what the training should be 
 and how it should be taught. The only 
 general criteria would appear to be that 
 training should involve the worker ac- 
 tively in the learning process and iden- 
 tify specific techniques and hazards of 
 MMH tasks (8, p. 199). 
 
 A MODEL MANUAL MATERIALS HANDLING TRAINING COURSE 
 
 The National Institute for Occupa- 
 tional Safety and Health (NIOSH) pub- 
 lication, "Work Practices Guide for 
 Manual Lifting," provides recommenda- 
 tions regarding the training of work- 
 ers who perform MMH tasks (_9, pp. 99- 
 101). These recommendations form the 
 basis for a model MMH training course. 
 The aims of safety training in MMH should 
 be to — 
 
 1. Make the miners aware of the dan- 
 gers in MMH. 
 
 2. Show miners how to avoid unneces- 
 sary stress. 
 
 3. Teach miners individually to be 
 aware of what they can handle safely. 
 
 The following items should be covered 
 in the training course: 
 
 materials han- 
 
 1 . The risks in manual 
 
 dling. Based upon the materials commonly 
 handled and the accident history of the 
 mine. 
 
91 
 
 2. The basic principles of manual m at- 
 erials handling . The basic physics of 
 MMH, the body as a system of levers, and 
 the work needed to shift loads. 
 
 3. The effects of MMH. 
 
 The basic 
 
 anatomy of the back, muscles, and joints, 
 and the effect of lifting on the body. 
 
 4. Individual awareness of the body's 
 strengths and weaknesses . Teach miners 
 how to judge the weights they can handle 
 safely, and where their body strengths 
 and weaknesses lie. 
 
 5. How to avoid accidents . Teach min- 
 ers how to recognize and avoid the physi- 
 cal factors that might contribute to an 
 accident, for example. 
 
 g. Is the floor clean, dry, and 
 nonsllp? 
 
 h. Is the area clear where the 
 load will be set down? 
 
 6. Handling skill : Emphasize the ac- 
 tual materials handled at the mine. Pro- 
 vide instruction on the following general 
 points: 
 
 a. How to prepare for materials 
 handling tasks. 
 
 b. How to recognize what loads can 
 be handled safely. 
 
 c. How to keep the load close to 
 the body when lifting. 
 
 a. Is the load free to move and 
 not stuck? 
 
 d. How to lift without twisting or 
 bending sideways 
 
 b. Is it a weight that can be 
 safely handled by one person? 
 
 c. Are lifting aids available? 
 
 e. How to use the legs to get 
 close to the load and to make use of 
 the body weight and the kinetic energy 
 of the body and load. 
 
 d. Does the load have handles to 
 grasp or can they be provided? 
 
 f. How to develop timing for 
 smooth and easy lifting. 
 
 e. Is protective clothing needed? 
 
 f . Is the work area clear of 
 obstruction? 
 
 7. Handling aids: Demonstrate the 
 handling aids available for materials 
 handling tasks, and encourage their use. 
 
 DETERMINING MATERIALS HANDLING TRAINING NEEDS 
 
 The basic steps of training in general 
 apply equally well to the training of 
 miners for materials handling tasks. In 
 order to develop an effective training 
 program, identify and define the materi- 
 als handling problems and then establish 
 procedures to control those problems. 
 
 Information necessary to evaluate ma- 
 terials handling Includes accident rec- 
 ords, mine conditions, and discussions 
 with mine personnel. An accident analy- 
 sis will Identify problem areas, in terms 
 of the who, what, where, how, and why 
 (individuals, tasks, materials handled, 
 causes, and so forth). This information 
 
 will provide a good idea of what areas 
 or topics need to be emphasized during 
 training (_3 ) . 
 
 In addition to the basic Information 
 about accidents, obtain specific details 
 concerning mine policies, procedures, 
 equipment and supplies, and responsibili- 
 ties of the miners. Obtaining this in- 
 formation will require talking to the 
 mine personnel most familiar with the 
 day-to-day operation of the mine, the 
 section supervisors. Questions should 
 cover the problems and hazards of materi- 
 als handling activities at the mine or 
 sections of the mine. 
 
92 
 
 HAZARDS OF MATERIALS HANDLING IN THE MINING INDUSTRY 
 
 Accident analyses of materials handling 
 accidents have identified several poten- 
 tially hazardous tasks (_5 ) . Most of 
 these accidents involve the act of manu- 
 ally handling materials, specifically, 
 lifting and lowering, pushing and pull- 
 ing, carrying, and shoveling. Although 
 these accidents provide an indication of 
 the general hazards of materials han- 
 dling, training should concern specific 
 tasks and materials associated with the 
 problem areas. 
 
 Understandably, the underground mine 
 environment is more hazardous and more 
 difficult to work in than most surface 
 environments. Underground conditions 
 
 increase the potential for accidents. 
 For example, poor maintenance of the mine 
 floor results in slippery and uneven 
 footing which contributes to accidents. 
 Bending or sitting on folded legs is com- 
 mon in mines of low roof height. Lifting 
 or carrying materials under such condi- 
 tions can result in back injuries (4). 
 In addition, the weight of materials han- 
 dled sometimes exceeds the physical capa- 
 bility of the miner and this can result 
 in injury. It is for these reasons that 
 training in materials handling should 
 include discussions of the work environ- 
 ment and the physical limitations of the 
 workers. 
 
 TRAINING METHODS 
 
 Lecturing requires that the instructor 
 talks and the miners listen. While this 
 method can be effective for a short per- 
 iod of time, it should not be the only 
 method used. A short lecture on the ba- 
 sic structure of the back, for example, 
 should be combined with slides or films 
 and class discussion. A discussion al- 
 lows for class participation. Asking a 
 few questions helps to focus on the top- 
 ics you want to cover. The following ex- 
 amples are questions that can be used for 
 discussion: 
 
 1. What are the most common injuries 
 and accidents in the mining industry and 
 at your mine? 
 
 2. What are the most common materials 
 handling accidents? 
 
 3. Where in your mine are materials 
 handling accidents occurring? And to 
 whom? 
 
 4 . How can 
 prevented? 
 
 these 
 
 accidents 
 
 be 
 
 Demonstration is the best teaching 
 method to use to show how something is 
 done. The classes should be small enough 
 that safe materials handling methods 
 can be demonstrated, preferably at the 
 worksite. The materials or objects known 
 to be associated with materials handling 
 accidents and back injuries (such as 
 trailing cables, oil drums, roof bolts, 
 timbers, rock dust bags, etc.), should be 
 used in actual demonstrations. 
 
 Mine supervisors should be actively in- 
 volved in developing and conducting the 
 training course. It does little good to 
 train miners in safe handling methods if 
 the methods are not used during materials 
 handling tasks on the job. Therefore, 
 observing day-to-day job performance and 
 correcting unsafe acts are essential 
 responsibilities of the mine supervisors. 
 
 COURSE OBJECTIVES 
 
 The purpose of the course should be to 
 
 instruct miners in the safe methods of 
 
 materials handling. After completion of 
 
 the course, the miners should be able to 
 identify the following: 
 
 The basic anatomy of the back. 
 
 General safety rules. 
 Safe lifting method. 
 Safe carrying method. 
 Safe shoveling method. 
 
93 
 
 The miners should be given a test to 
 demonstrate they have learned the mate- 
 rial. The test method should provide 
 
 evidence, either by doing or by listing 
 the safe methods, that the miners have 
 learned what you want them to do. 
 
 COURSE MATERIALS 
 
 The following illustrations provide ex- 
 amples of course materials for training 
 in materials handling. 
 
 the training course. Figure 3 shows the 
 personal protective equipment that should 
 be worn (2). 
 
 A brief lecture on the basic anatomy 
 of the back can be used to teach the 
 effects of materials handling on the 
 body. Figure 1 shows the structure of 
 the back (2). The NIOSH publication, 
 "Work Practices Guide for Manual Lift- 
 ing," provides reference material that 
 can be helpful (9). 
 
 Discussions of personal experiences 
 with back pain can assist in "selling" 
 the need for the training. Examples of 
 materials handling accidents at your mine 
 "bring home" the point that the potential 
 for injury is real. Analysis of your 
 mine's accident history can reveal the 
 problem areas that need to be emphasized. 
 Figure '2 illustrates typical examples of 
 materials handling accidents. 
 
 Strains, bruises, cuts, or other inju- 
 ries may result from handling materials. 
 Personal protection equipment and reasons 
 for wearing them should be covered during 
 
 Lifting and lowering materials are the 
 most common materials handling tasks per- 
 formed in the mines. Figure 4 provides 
 examples of safe lifting methods. The 
 lifting tasks selected for your training 
 course should include the materials most 
 often handled at your mine. 
 
 Accident statistics show that handling 
 electrical cable is a leading cause of 
 back injuries and materials handling ac- 
 cidents in mining. Many of these acci- 
 dents result from the miner pulling on 
 the cable rather than lifting. Figure 5 
 provides instruction on the safe handling 
 of cable. 
 
 Shoveling coal and rock account for a 
 large number of back injuries in mining. 
 Therefore, instruction provided on the 
 safe method for shoveling materials is 
 needed as shown in figure 6 (2^) . The 
 main point to stress is to avoid twisting 
 the back while shoveling. 
 
 GENERAL MATERIALS HANDLING SAFETY RULES 
 
 There are a number of general safety 
 rules that apply to materials handling. 
 One of the most important is to plan 
 ahead. Determine where the material will 
 be placed before moving it. If carrying 
 materials a long distance, plan rest 
 stops to prevent fatigue. If the materi- 
 al required to be moved is too heavy. 
 
 then get help or use a mechanical device, 
 such as a hoist, wheelbarrow, front-end 
 loader, or forklift. The miner should 
 also be instructed to become aware of the 
 surrounding environment, obstacles in the 
 pathways, and wet or muddy floor 
 surfaces. 
 
 SUMMARY 
 
 Back injuries have been identified as a 
 significant problem area in the mining 
 industry. Accident statistics have shown 
 that most back injuries occur during ma- 
 terials handling activities. Training in 
 safe materials handling methods is one 
 approach for control of back injuries. A 
 number of general recommendations and 
 
 specific examples have been presented to 
 assist training personnel in the mining 
 industry to develop a manual materials 
 handling training course to reduce back 
 injuries. It is hoped that some prac- 
 tical suggestions have been made and 
 will be used where needed in the mining 
 industry. 
 
94 
 
 REFERENCES 
 
 1. Ayoub, M. M. Control of Man- 
 ual Lifting Hazards: I. Training in 
 Safe Handling. J. of Occupational Med. , 
 V. 24, No. 8, August 1982, pp. 573-577. 
 
 7. Snook, S. H. , R. A. Campanelli, 
 and J. W. Hart. Three Preventive Ap- 
 proaches to Low Back Injury. Profession- 
 al Safety, July 1978, pp. 34-38. 
 
 2. Bituminous Coal Operations Associa- 
 tion and National Coal Association. Ma- 
 terials Handling (SLIDE/TAPE Training 
 Program). Produced by National Photo- 
 graphic Laboratories, Inc., Houston, TX, 
 1981. 
 
 3. Christopherson, K. I., C. H. Cover, 
 and M. J. Klishis. How To Tailor Train- 
 ing Material To Fit Your Mine. BuMines 
 contract J0188069; for inf., contact W. 
 J. Wiehagen, Pittsburgh Res. Center, 
 Pittsburgh, PA. 
 
 8. U.S. Department of Health, Educa- 
 tion and Welfare NIOSH Report on Interna- 
 tional Sjnnposium: Safety in Manual Mate- 
 rials Handling (State Univ. NY at Buffa- 
 lo, July 18-20, 1976). Pub. as Safety in 
 Materials Handling, ed. by C. G. Drury, 
 NIOSH Pub. 78-185, 219 pp.; NTIS PB- 
 297-660. 
 
 9. U.S. Department of Health and Hu- 
 man Services. Work Practices Guide for 
 Manual Lifting. NIOSH Pub. 81-122, 1981, 
 183 pp.; NTIS PB 82-178-948. 
 
 4. Diaz, R. A., and A. D. Chitaley. 
 System For Handling Supplies in Under- 
 ground Coal Mines. BuMines contract 
 H0188049; for inf., contact G. R. Bock- 
 osh, Pittsburgh, Res. Center. 
 
 5. Foote, A. L. , and J. S. Schaefer. 
 Mine Materials Handling Vehicle (MMHV) 
 contract H0242015, MB Associates). Bu- 
 Mines OFR 59-80, 1978, 308 pp.; NTIS 
 PB 80-178890. 
 
 6. Nertney, R. J., and J. R. Buys. 
 Training as Related to Behavioral Change. 
 ERDA-76-45-6, SSDC-6, June 1976, 9 pp.; 
 available from System Safety Development 
 Center, Idaho Falls, ID. 
 
 10. U.S. Mine Safety and Health Admin- 
 istration. Injury Experience in Coal 
 Mining, 1978-1981, MSHA IR's 1112, 1122, 
 1133, 1138. 
 
 11. . Injury Experience in Me- 
 tallic Mineral Mining, 1978-1981. MSHA 
 IR's 1116, 1126, 1137, 1142 
 
 12. 
 
 Injury Experience in Non- 
 
 metallic Mineral Mining (except stone and 
 coal), 1978-1981. MSHA IR's 1114, 1124, 
 1135, 1140. 
 
95 
 
 Your back is a "complex System" 
 
 It includes : 
 
 THE SPINE 
 
 33 bones (vertebrae). The upper 
 24 are separated by disks that act 
 as cushions. 
 
 NERVES 
 
 31 pairs branching out from the 
 spinal cord, sending information 
 to the brain and orders to the 
 muscles. 
 
 MUSCLES 
 
 400 of them producing motion in 
 all directions, they are attached to 
 the bone by about 1,000 tendons. 
 
 THE SPINAL CORD 
 A half-inch thick "cable" of nerves, 
 about 18-inches long, controls all 
 activities below neck level. 
 
 FIGURE 1. - Basic anatomy of the back. 
 
96 
 
 ^-^^^ 
 
 FIGURE 2. - Examples of materials handling accidents. 
 
97 
 
 METATARSAL SHOES 
 
 Injuries to the feet are common and painful. 
 They most frequently occur when materials that 
 are being carried slip or when they fall be- 
 cause they are stacked improperly. Metatarsal 
 shoes are recommended because they protect 
 your entire foot — the toes, the arch, and 
 the top. 
 
 HARD HATS 
 
 It is easy to bump your head against overhead 
 obstacles or stacked supplies while working in 
 congested, dark surroundings. Hard hats are 
 essential for your protection and should be 
 
 worn at all times whether you're working 
 
 outside or inside the mine. 
 
 SAFETY GLASSES 
 
 Your eyes should be protected from cool dust, 
 rock dust and other particles that can cause 
 severe irritations. Safety glasses make sure 
 such damaging abrasives do not enter your 
 eyes. 
 
 LEATHER GLOVES 
 
 When handling materials and supplies, it is im- 
 portant to maintain a firm grip. Leather gloves 
 help you to do this, as well as protecting your 
 hands from cuts, burns, and blisters that could 
 become infected. 
 
 RUBBER BOOTS 
 
 Since you will be working around high voltage 
 trolley wires and wet, muddy areas it may be 
 necessary to wear rubber boots to avoid any 
 electrical shock. Rubber boots also help you 
 maintain a firm foothold. 
 
 LEG BANDS 
 
 Securing your pants legs is an essential part 
 of your safety. Leg bands is one way of doing 
 this. You should wear them at all times to a- 
 void tripping and getting caught on moving 
 pieces of equipment. 
 
 FIGURE 3. - Personal protective equipment. 
 
98 
 
 As you approach the load determine 
 its weight, size and shape. Consider 
 your physical ability. 
 
 Bend the knees and get a firm grasp 
 on the object. 
 
 Do not twist or turn until the object 
 is in carrying position. 
 
 Stand close to the object with feet 
 8 to 12 inches apart for good bal- 
 ance. 
 
 D 
 
 Using both leg and back muscles lift 
 the load straight up. Keep the ob- 
 ject close to the body. 
 
 Rotate body by turning your feet and 
 make sure path of travel is clear. 
 
 To set the object down, use leg and 
 back muscles and lower the object 
 by bending the knees. 
 
 FIGURE 4. = Safe lifting. 
 
 the fic 
 
99 
 
 B 
 
 First, stand close to the belt and 
 establish firm footing. 
 
 Then get the items to the side of 
 the belt by pulling gradually, without 
 sudden jerky movements. 
 
 Lift the items off the belt, keeping 
 your back as straight as possible and 
 holding the load close to your body. 
 
 Remember not to twist your back 
 when unloading materials, as this 
 miner is doing. Instead, reposition 
 your feet, and turn your body. 
 
 First, be sure to wipe off any dirt or 
 grease before reaching for the ob- 
 ject you are going to lift. 
 
 B . Then, stand close to the object and 
 get a firm foothold. 
 
 Straddle the load sonnewhat and squat 
 
 down, bending at the knees not 
 
 at the back. 
 
 Incorrect d. 
 
 Hold the object securely so your grasp 
 does not slip. 
 
 E . Finally.. ..slowly straighten to an up- 
 right stance, keeping your back in a 
 vertical position. 
 
 E. Then bend your knees to lower the load. 
 
 FIGURE 4. - Safe lifting. -Continued, B, From a belt; C, an irregular shaped object. 
 
100 
 
 
 FIGURE 5. - Handling cable. 
 
101 
 
 Always shovel in the direction the belt is 
 moving . This way, you avoid catching 
 the shovel in the belt and keep from 
 getting hit with the handle. 
 
 Avoid twisting your back. Turn your feet 
 and your entire body so your back is not 
 strained. 
 
 FIGURE 6. - Example of safe shoveling. 
 
102 
 
 MECHANIZATION OF MATERIALS HANDLING TASKS 
 By Richard L. Unger"! 
 
 ABSTRACT 
 
 The Bureau of Mines is sponsoring re- materials handling activities are dis- 
 cussed. A daily supply handling system 
 is presented, as well as several concepts 
 to reduce manual handling requirements 
 during equipment and mine maintenance. 
 
 search aimed at reducing the manual ef- 
 fort required to transport or transfer 
 materials used in underground coal mines. 
 Specifically, production supply, mine 
 maintenance, and equipment maintenance 
 
 INTRODUCTION 
 
 In the mid-1970' s, the Bureau of Mines 
 sponsored studies to determine the types 
 and causes of materials handling injuries 
 in underground coal mines. One result of 
 this work was the determination that ap- 
 proximately one-half of all materials 
 handling accidents occur in the produc- 
 tion supply function (fig. 1). Produc- 
 tion supply refers to the handling of 
 daily supply items from the surface to 
 locations near the working face in sup- 
 port of production activities. Examples 
 of this type of handling include trans- 
 porting rock dust bags, roof bolts, and 
 timbers. It was also found that the com- 
 bination of equipment and mine mainte- 
 nance functions accounted for approxi- 
 mately one-quarter of the materials han- 
 dling accidents. Some examples of these 
 functions include extracting motors from 
 
 continuous miners, 
 hanging cable. 
 
 changing tires, and 
 
 The Bureau initiated two research proj- 
 ects to reduce the need for manual han- 
 dling of items through a systems approach 
 involving mechanization of supply han- 
 dling. The first project, begun in 1978, 
 was to develop a system for handling 
 daily supplies in underground coal mines, 
 directed primarily toward the production 
 supply function. The second project was 
 to develop a vehicle for mine and equip- 
 ment maintenance activities. These two 
 Bureau research projects were aimed at 75 
 pet of the materials handling accidents 
 in underground coal mines. This paper 
 describes the methods and results to date 
 of these two projects. 
 
 A SYSTEMS APPROACH TO HANDLING DAILY SUPPLIES 
 
 The surest way to reduce materials han- 
 dling injuries is to reduce or eliminate 
 the need for manual handling. This is 
 the purpose of the Bureau's daily supply 
 handling system. Studies conducted at a 
 Pennsylvania coal mine over a 2-yr span 
 indicate that production times could be 
 increased by at least 3 pet and supply 
 handling injuries reduced by as much as 
 7 3 pet if a supply system based on pal- 
 letization and mechanical handling were 
 to be implemented. Such a system has 
 been developed and is outlined below. 
 
 ^Civil engineer, Pittsburgh Research 
 Center, Bureau of Mines, Pittsburgh, PA. 
 
 PALLETIZATION 
 
 Daily supplies would be palletized on 
 the surface and moved as unit loads 
 throughout the mine. As much as possi- 
 ble, pallets of supplies as delivered by 
 vendors would be moved to the section. 
 The supplies moved to the section would 
 be based on the estimated needs for that 
 day. This should eliminate delay or lost 
 production time owing to lack of materi- 
 als or waste due to oversupply. Large 
 items, such as timbers or rail, would be 
 left on dedicated supply cars or trailers 
 off the haulageway. These items are then 
 off-loaded as needed. Empty pallets. 
 
railcars, and trailers are returned to 
 the surface on the return supply trip. 
 
 PERMISSIBLE FORKLIFT 
 
 Once the supply trip brings the pallets 
 to the section, a method is required for 
 off-loading and delivering them to the 
 face as they are needed. After consider- 
 ing many alternatives, the Bureau chose 
 the idea of a permissible, battery- 
 powered forklift, with a winch and forks, 
 for handling pallets and long narrow 
 items such as timbers. An additional 
 benefit would be using the forklift as a 
 hoist to assist in equipment maintenance 
 by reversing the forks. Figure 2 gives 
 the forklift's specifications while fig- 
 ures 3 through 7 present its layout. 2 
 The forklift offers compactness, maneuv- 
 erability and ease of materials handling 
 underground. Forklifts are commonly used 
 to handle supplies in the surface yard, 
 however, the underground applications 
 have usually been limited to high-seam 
 mines that allow permissible diesel ve- 
 hicles. This appears to be due to the 
 unavailability of suitable forklift ve- 
 hicles for use in the lower seams. Elec- 
 tric cable forklifts are available for 
 underground use; but the cable restricts 
 reach and maneuverability, thereby limit- 
 ing its suitability for the section han- 
 dling operations needed for this system^ 
 (fig. 8). 
 
 103 
 
 The forklift's task would be to unload 
 the supply trip and move the pallets to 
 the section storage area. As supplies 
 are needed at the face, the forklift 
 would deliver them pallet by pallet up to 
 their point of use. The forklift's small 
 size would enable it to manuever around 
 most equipment in the entry, such as a 
 roof bolter. 
 
 Rails, timber, and pipe are carried by 
 a special sling attachment on the side of 
 the forklift directly to the usage point 
 (fig. 7). The forklift's operation gen- 
 erally requires two people: the operator 
 and a helper who spots loads and directs 
 pallet movement. 
 
 When not being used to handle supplies , 
 the forklift has uses in equipment and 
 mine maintenance activities. By revers- 
 ing the forks, a hydraulically powered 
 hoist is created that can remove or posi- 
 tion heavy motors or lift timber to sup- 
 port the roof. It should be pointed out, 
 however, that the main function of the 
 forklift is supply handling. This dif- 
 fers from other vehicles sometimes used 
 to handle supplies, such as a scoop. 
 Often, when a scoop is needed to handle 
 supplies, it is being used for its pri- 
 mary task of coal cleanup. The supplies 
 must then be moved by other means, usual- 
 ly by hand. 
 
 TEST RESULTS 
 
 The daily supply handling system was 
 tested at the Safety Research Coal Mine 
 located at the Pittsburgh (PA) Research 
 Center. Overall, the system worked well, 
 with the need for manual handling of 
 items reduced to the initial loading 
 of the pallets and final use. However, 
 there were problems , such as 
 
 Pallet design. Some wooden pallets 
 could not withstand the rugged under- 
 ground conditions, and broke apart after 
 a short time in use. 
 
 ^Diaz, R. A., and A. D. Chitaley. Sys- 
 tem for Handling Supplies in Underground 
 Coal Mines. BuMines contract H0188049; 
 for inf., contact G. R. Bockosh, Pitts- 
 burgh Res. Center, Pittsburgh, PA. 
 
 A few lightweight-design steel pallets 
 were tested and proved to be much stur- 
 dier. More testing is needed in this 
 area. 
 
 The permissible forklift, though work- 
 ing well for a prototype, has a few defi- 
 ciencies that need to be corrected. 
 These include the need for increased 
 traction in soft ground, greater overall 
 battery life and speed, and more precise 
 handling. The Bureau is considering a 
 second prototype to correct these prob- 
 lems. An alternative solution would be 
 for the mining industry or equipment man- 
 ufacturer to apply their expertise in 
 this area. 
 
 -^Work cited in footnote 2. 
 
104 
 
 The palletization-f orklif t method of 
 handling daily supplies in underground 
 coal mines shows great promise for re- 
 ducing manual materials handling. The 
 
 results should be a reduction in materi- 
 als handling injuries, more efficient 
 distribution of supplies, as well as sav- 
 ings in daily supply handling labor. 
 
 MECHANICAL DEVICES FOR MINE MAINTENANCE AND EQUIPMENT MAINTNENACE 
 
 As stated earlier, production sup- 
 ply, mine maintenance, and equipment 
 maintenance accounted for approximately 
 75 pet of materials handling accidents 
 reported in Bureau's studies. The Bu- 
 reau's work into a system for handling 
 daily production supplies resulted in 
 a palletization-f orklif t scheme. This 
 section discusses the Bureau's project to 
 reduce mine maintenance and equipment 
 maintenance accidents. 
 
 The initial intent of this project was 
 to design and develop a universal mainte- 
 nance and materials handling vehicle. 
 This approach has been tried before by 
 the Bureau with poor results. 4 In a 
 sense, the permissible forklift for the 
 daily supply handling system is another 
 attempt at an underground materials han- 
 dling vehicle. However, there are two 
 main differences between the forklift and 
 the vehicle proposed for this project. 
 
 1. The forklift has one major task; 
 transporting pallets. A maintenance ma- 
 terials handling vehicle, on the other 
 hand, should be adaptable to individual 
 tasks and be able to transport and posi- 
 tion a variety of single items into all 
 areas of the mine. This requires a ver- 
 satile vehicle with several lifting and 
 carrying attachments. 
 
 2. The forklift is intended to carry 
 large volumes of items on a daily basis. 
 A maintenance materials handling vehicle 
 would be used only in specific situa- 
 tions, and therefore with less frequency. 
 This would make the vehicle harder to 
 justify in terms of cost. 
 
 ^Foote, A^ L. , and j! si Schaefer. 
 Mine Minerals Handling Vehicle (MMHV) 
 (contract H0242015, MB Associates). Bu- 
 Mines OFR 59-80, 1978, 308 pp.; NTIS PB 
 80-178890. 
 
 Based on the above reasons, it was de- 
 cided that a series of simple, relatively 
 inexpensive materials handling devices 
 would be more readily accepted by mining 
 industry. Each device would be tested in 
 work situations at cooperating mines. 
 The results of the tests, as well as 
 plans and guidelines on fabrication, 
 would be made available to the industry. 
 The hope is that individual mining com- 
 panies can be made aware of how mechani- 
 zation of mine and equipment maintenance 
 tasks can be both inexpensive and helpful 
 in reducing their materials handling 
 problems. 
 
 Eight materials handling device-tool 
 concepts were generated, based on acci- 
 dent statistics, interviews with mine op- 
 erators and underground mine visits. 
 This lift was then reduced, due to budget 
 constraints, to what was felt to be the 
 five most useful devices. These devices 
 are briefly described below. 5 
 
 Lifting Boom (fig. 9) . One of the ma- 
 jor needs identified was for a simple 
 boom device that could be used to lift 
 and transport components weighing up 
 to 1 ton and to lower them safely to 
 the ground. The boom would mount on the 
 front of a small scoop when the bucket 
 was removed, and would have a hydraulic 
 winch with 100 ft of cable. 
 
 A device was built on this concept and 
 is now in one of the demonstration mines 
 for testing. All comments from the mine 
 thus far have been favorable. 
 
 ^Conway, E. J., and W. W. Elliot. Mine 
 Maintenance Material Handling Vehicle: 
 Investigative Study and Concept Develop- 
 ment, BuMines contract H0 113018; for 
 inf., contact E. A. Ayres, Pittsburgh 
 Res. Center, Pittsburgh, PA. 
 
105 
 
 Mine Jack-Wheel Changer (fig. 10) . 
 Another concept is for a floor type jack 
 that could be used to lift a component, 
 transport it over short distances, and 
 maneuver it into position for installa- 
 tion. Typical tasks would be aligning 
 and lifting a drive motor under the fen- 
 der of a shuttle car, or changing wheels 
 weighing up to 1,000 lb on shuttle cars, 
 cutters, etc. 
 
 Mud Truck (fig. 12) . This device is 
 designed for use in low-seam mines. It 
 is equipped with high flotation tires to 
 permit one person to pull it through soft 
 bottoms. The steerable front tires and 
 articulation joint provide even load dis- 
 tribution with maximum maneuverability. 
 It can be used for transporting toolbox- 
 es, parts, and supplies to wherever they 
 are needed. 
 
 The lift capability is derived from a 
 hydraulic jack mechanism. The jack head 
 tilts and rotates to allow more flexibil- 
 ity in placing the load. The ballon 
 tires make movement easier over the mine 
 floor, and the long handle provides lev- 
 erage by which to maneuver the load up, 
 down, or sideways as required. 
 
 Cable Puller (fig. 11) . This device is 
 a capstan powered by either a hydraulic 
 or electrical source, and pulls a rope 
 attached to a mining vehicle trailing ca- 
 ble. The pull rate can be controlled by 
 the tension held by the laborer. The 
 capstan can pull trailing cable and water 
 hose out of an entry when preparing to 
 move across the section or pull any cable 
 on a conventional mining section. 
 
 Pivot Crane (fig. 13) . This portable 
 winch crane is an adaptation of devices 
 commonly used on vehicles above ground. 
 The crane mounts in a socket strategical- 
 ly located on any machine and can be 
 stored at the section shop when not in 
 use. Its uses include major component 
 replacement in the 100- to 2,000-lb cate- 
 gory or any lifting task adjacent to a 
 machine. 
 
 All of these devices can be fabricated 
 at the mine or in a small shop. Most can 
 be modified to fit the needs of a partic- 
 ular mine. For instance, a chain winch 
 can be substituted for the hydraulic 
 winch in the lifting boom, at a substan- 
 tial cost saving. 
 
 DISCUSSION 
 
 It is hoped that the mining industry 
 will incorporate the ideas the Bureau is 
 presently pursuing in relation to reduc- 
 ing materials handling accidents. Though 
 every mine is unique, with its own par- 
 ticular materials handling problems, the 
 ideas presented in this paper are adapta- 
 ble to any mine in one form or another. 
 
 It is up to the mine operator to make 
 sure that avoidable materials handling 
 accidents are eliminated by providing the 
 most efficient methods of supply distri- 
 bution as well as reasonable amounts 
 of mechanization of materials handling 
 tasks. 
 
106 
 
 140 
 130 
 120 
 110 
 100 
 
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 UJ 
 
 o 
 
 o 80 
 
 o 
 
 < 
 
 li. 70 
 
 133 (50%) 
 
 'a 
 
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 44 ( 16%) 
 
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 171 
 
 30(11%) 
 
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 ^^v 
 
 FIGURE 1. - AccicJent frequenciesfordifferent 
 handling functions. 
 
 Permissibility 
 
 MSHA and Pennsylvania approved for work-face 
 
 Type 
 
 Battery powered skid steer 
 
 Drive 
 
 4 wheels driven by two hydraulic motors 
 
 Payload 
 
 3- by 3-ft pallets typical at maximum 1,500 lb 
 
 
 Timber 16 ft by 7 by Sin, quantity 3 to 5 
 
 Speed 
 
 1.3 mph moximum 
 
 Ronge 
 
 2 h continuous duty 
 
 Dimensions 
 
 Height 56- in over canopy 
 
 
 Width 61 in 
 
 
 Length 12 ft, 4 in 
 
 
 Ground clearance 7, 9, or II in 
 
 
 Forks 31 -in long by 38 travel 
 
 
 Empty weight 7,470 lb 
 
 Auxiliary 
 
 Power winch 3,000-lb copacify 
 
 equipment 
 
 l/4-in-diam wire rope, 
 
 
 120ft 
 
 
 Timber carrying hooks 
 
 
 Reversible forks 
 
 
 Sheove and hook attachment for crane use of forks 
 
 FIGURE 2. - The underground supply handling 
 forklift specifications. 
 
 56-in, 
 3- post canopy 
 
 Hydraulic pump 
 l5-hp,dc motor 
 
 Starter 
 
 Hydraulic tank 
 
 Telescopic mast 
 
 126-v, 200- Ah 
 battery 
 
 31-in forks by 38-in travel, 
 lO-in lift without raising mast 
 
 am control joystick 
 Forklift controls 
 Light switch box 
 
 -Power winch, dog clutch, 
 and control lever 
 
 7-in or 9-in 
 ground clearance 
 
 -6:50 by 10 
 pneumatic tires 
 
 FIGURE 3. - Perspective schematic-underground supply handling forklift. 
 
107 
 
 Joystick tram control-) p Panic stop bar 
 
 e extinguisher 
 
 l5-hp,dc motor 
 
 Battery 
 
 3l-in by 38-in travel, 
 side shift carriage forklift 
 
 Hydraulic tank 
 
 6:50 by 10 tires- 
 FIGURE 4. - Top view schematic — underground supply handling forl<lift. 
 
 Telescopic mast 
 with 3° forward 
 
 15-hp, 
 dc motor _ 2-stage 
 
 hydraulic pump 
 
 126-v, 200-Ah 
 battery- 
 
 Hydraulic 
 orbital motor 
 
 FIGURE 5. - Front and right side view schematics— underground supply handling forklift. 
 
108 
 
 Arms fold back for storage 
 
 // ^ 
 
 ^3E^ 
 
 i}! 
 
 Side of machine 
 
 J 
 
 Sling coble 
 
 rl6-ft-|onq timbers 
 
 ' /^//, 
 
 IglMM! 
 
 7-in minimum , ; - i i -^ — ■■ — i-i-. 
 
 FIGURE 6. - Sling arrangement for carrying 
 long, narrow loads. 
 
 FIGURE 7. - Hoist configuration of forks. 
 18-ft entry 
 
 Skid steer 
 turning center 
 
 Crib set 
 
 "^c^=? 
 
 ^r 
 
 FIGURE 8. - Maneuvering capabilities of skid steer. 
 
109 
 
 4^ 
 
 FIGURE 9. - Lifting boom during tests at a low-seam coal mine. 
 
no 
 
 Slide mechanism 
 
 ^^ 
 
 -Balloon tire 
 
 Tiltable saddle 
 
 Telescoping 
 handle, 
 
 _fi, Y_ 
 
 To laborer , 
 
 Control 
 
 Trailing cable 
 
 Motor 
 
 PLAN VIEW 
 
 -ri n r. 
 
 ^Foot pad 
 
 SIDE VIEW 
 
 FIGURE 10. • Mine jack-wheel changer. 
 
 Capstan 
 
 Anchor chain. 
 
 Drive chain 
 
 Skid mounted' 
 
 SIDE VIEW 
 
 FIGURE 11. . Cable puller. 
 
 Roof 
 
 , Load deck 
 
 Steer and tow bar^ 
 
 SIDE VIEW 
 
 FIGURE 12. - Mud truck. 
 
 Machine frame. 
 
 Component-. 
 
 
 "Swivel crane 
 
 )r 
 
 Socket 
 
 Floor 
 FIGURE 13. - Pivot crane. 
 
 TiU.S. GOVERNMENT PRINTING OFFICE: 1983-605-015/50 
 
 INT.-BU.OF mines, PGH., pa. 27100 
 
 963 
 
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