key: cord-0813382-eu3i6r76 authors: Weldon, Anthony; Duncan, Michael J.; Turner, Anthony; Sampaio, Jaime; Noon, Mark; Wong, Del P.; Lai, Vivian W. title: Contemporary practices of strength and conditioning coaches in professional soccer date: 2020-10-24 journal: Biol Sport DOI: 10.5114/biolsport.2021.99328 sha: ee86127ad6a6a46c55d8c5eecfe6d746d90d708f doc_id: 813382 cord_uid: eu3i6r76 This study describes the contemporary practices of strength and conditioning coaches in professional soccer. Fifty-two strength and conditioning coaches from professional leagues across 18 countries completed an online survey, consisting of 45 questions, with eight sections: (a) background information, (b) muscular strength and power development, (c) speed development, (d) plyometrics, (e) flexibility development, (f) physical testing, (g) technology use, and (h) programing. A frequency analysis was used to assess and report responses to fixed response questions, and thematic-analysis used for open-ended questions to create clear, identifiable and distinct themes. All strength and conditioning coaches were educated to degree level or higher, 65% held strength and conditioning certifications and 54% held soccer coaching certifications. Concentric (100%) and eccentric (98%) modes of resistance were the most commonly prescribed, whereas the squat (including variations) (52%) was deemed the most important exercise for soccer players. Hang clean (33%) and multiple hops/lunges (89%) were the most programed Olympic weightlifting and plyometric exercises. Global Positioning Systems (94%) were the most utilized technology-based equipment. Time, scheduling and fixtures were the biggest issues faced, which made it difficult to periodize training programs and apply appropriate training loads. Furthermore, strength and conditioning coaches would like to further integrate technology to comprehensively monitor and test players, while also believing that technology will continue to be developed and integrated in the future. Strength and conditioning coaches from professional soccer can use the information from this study to review current practices and also provide ideas for diversifying or modifying future practices. Strength and conditioning coaches (SCCs) in professional soccer should use their understanding of sports science and coaching to achieve the primary objectives of reducing injuries and improving physical and sports performance [1, 2] . Some SCCs specifically focus on physical training, monitoring and testing, whereas others have soccer coaching certifications and experience, allowing the development of technical, tactical, and mental skills [1, 3] . Nevertheless, SCCs should use strength and conditioning guidelines and research informed methods to develop physical capacities associated with superior soccer performance [1, 2, 3] . For example, small-sided games, repeated sprint ability (RSA) and repeated change-of-direction drills can improve aerobic and anaerobic capacities, while approved by the Research Ethics Committee of the Technological and Higher Education Institute of Hong Kong. To target and invite the relevant population for this study, an online search was conducted through available biographies (e.g., LinkedIn, professional club webpages) of SCCs working in professional soccer. Strength and conditioning coaches were sought from 28 countries with the most registered recreational and professional players according to the FIFA Big Count Statistical Summary Report [22] . Contact information and responses were received from SCCs in 14 of these countries. Furthermore, invited SCCs were requested to share the survey with their SCC network in professional soccer. This led to additional responses from professional soccer leagues in: Australia, Singapore, Slovakia and Thailand. Therefore, in total SCCs from 18 countries were included in this study. Due to unequal sample sizes from SCCs respective countries/continents of occupation, it was not feasible to draw direct comparisons within this study. All SCCs provided informed consent to initiate the anonymous online survey, and only fully completed surveys were used for analyses. The survey started with an explanation of the purpose, aims, required time-commitment, and confidentiality of information. Coaches were informed a copy of results may be sent to them upon request. All responses from Google Forms were downloaded into an Excel 2016 spreadsheet (Microsoft Corporation, Redmond, WA). Fixed response questions were assessed using a frequency analysis. Openended questions were assessed using a thematic analysis approach [23] using the following six-stage process: (a) familiarization with the data, (b) generating initial codes, (c) searching for themes, (d) reviewing themes, (e) defining and naming themes, and (f) producing the report. This thematic-analysis method has been used in prior studies surveying SCCs [11, 20] . Thereafter, overarching clear and identifiably distinct themes, representing the main ideas or patterns emerging from the raw data were generated for each openended question. Some responses provided sufficient information that more than one overarching theme could be identified. All themes were reviewed and agreed to by all authors. Fifty-two SCCs with a mean age of 35.6 ± 7.9 years and strength and conditioning experience of 11.5 ± 7.2 years, participated in this study. All SCCs worked in professional leagues across 18 countries, including: United Kingdom (38%), Belgium and Austria (each 10%), United States of America (6%), Portugal, Singapore, Italy, Slovakia and Spain (each 4%), and Argentina, Australia, Chile, France, Iran, Mexico, Netherlands, Sweden, and Thailand (each 2%). The most physical demands of soccer and congested fixture schedules [8, 9] . Therefore, monitoring individual player's internal and external loads in physical training, soccer-specific training, and competitive matches, is commonly employed [9, 10] . This provides insight to each player's current condition, enabling SCCs to make informed decisions regarding periodized plans and strength and conditioning programs [9, 10] . Although literature advises the practical and scientific practices of SCCs in professional soccer, there is limited evidence addressing whether this translates well to field settings or if alternative methods are preferred [11] . Therefore, with the roles, responsibilities and practices of SCCs continuing to evolve, it is important contemporary practices are understood. This includes: data analytics [10, 12] , supporting and monitoring player's psychological wellbeing [13] , and injury reduction strategies [14] . Several studies have investigated the practices of SCCs in different professional sports, including: American football [15] , ice hockey [16] , baseball [17] , basketball [18] , rugby union [19] , and swimming [20] , but not soccer, which is surprising given its global popularity. Therefore, this study aimed to investigate the contemporary practices of SCCs working in professional soccer. This will help identify potential gaps between methods used, proposed guidelines, and real practice, facilitating the development of research and education resources tailored to the current climate. Furthermore, to provide a source of information for existing and progressing SCCs in soccer. This cross-sectional, explorative study was designed to provide descriptive information about the contemporary practices of SCCs in professional soccer from different countries and leagues. Strength and conditioning coaches were required to describe their practices and opinions, to provide an understanding of their knowledge and practical application of sports science and coaching in professional soccer. The survey was adapted from previous research [11, 15, 19, 21] and developed using Google Forms. The survey consisted of eight sections: (a) background information, (b) muscular strength and power development, (c) speed development, (d) plyometrics, (e) flexibility, (f) physical testing, (g) technology use, and (h) programing. The survey included 35 fixed responses and 10 open-ended questions, and coaches could provide specific answers using "other" option for most questions (see Appendix 1) . Some questions allowed more than one response, meaning some questions had more responses than others. Pilot testing was conducted by all members of the research team, then by three accredited SCCs, for a total three rounds of pilot testing before the survey was finalized. Pilot testing led to modifications to the wording and structure of the survey to avoid ambiguity of terms with varying definitions, and ensuring validity for use with this population. The study was conducted in accordance with the ethical standards of the Helsinki Declaration and [15] [16] [17] [18] [19] [20] , likely due to a broader inclusion criteria, instead of focusing on specific leagues or countries. Strength and conditioning certifications were held by 65% of coaches, and 10% had more than one certification, including: Unit- The most used set ranges were: 3-4 (87%), 5-6 (25%), 1-2 (14%), and 7-8 (8%). The most reported repetition ranges used per set were: 7-9 (62%), 4-6 (54%), 10-12 (48%), 15+ (12%), and 13-15 (10%). Other responses included: "depending on the athlete/ player". In-Season: The reported number of strength training sessions conducted each week were: two (62%), three (40%), one (35%), four (15%), and five (4%). Whereas, 31-45 min (58%), 16-30 min (42%), 46-60 min (30%), 61-75 min (10%), and 0-15 min (4%) were the reported session durations. The most used set ranges were: 3-4 (90%), 1-2 (37%), 5-6 (15%), and 7-8 (14%). The most reported repetition ranges used per set were: 4-6 (94%), 7-9 (44%), 1-3 (21%), and 10-12 (19%) . Other responses included: "depending on the player's level". Periodization, Set Loads and Recovery: Periodization strategies were used by 98% of coaches to structure programs. Other responses included: "depends on the definition of periodization". The most common methods to determine set loads were: athlete dependent (52%), predicted repetition maximum (44%), velocity (40%), repetition maximum (29%), subjective guess (21%), ratings of perceived exertion (21%), trial and error (19%), other (12%), and train to failure (6%). Other responses included: "bodyweight", "power output", "flywheel eccentric training", "my choice", "previous session loading" and "reps in reserve". The recovery time prescribed by SCCs between physical training, sports training and competition is presented in Table 1 . Resistance Training: All SCCs used resistance training with the most common modes being: concentric (100%), eccentric (98%), isometric (69%), variable (e.g. bands and chains) (65%), isoinertial (e.g. flywheel) (39%), and machine (37%). Other responses included: "pneumatic resistance". Olympic weightlifting and associated derivative exercises were prescribed by 67% of coaches, with the most common exercises being: hang clean (33%), power clean (31%), jump shrugs (25%), hang snatch (23%), clean high pull (21%), clean (21%), power jerk (19%), power snatch (19%), snatch (19%), jerk (15%), snatch high pull (8%), and other (8%). Other responses included: "clean press", "relate movements to sport", "landmine jerks", and "other free-weight variations". The top five weightlifting exercises programed by SCCs were ranked in order of importance, responses are presented in Table 2 . All SCCs used flexibility exercises, which were predominantly prescribed: before practice (79%), after practice, (58%), independently/athlete led (54%), after workout (40%), before workout (31%), The frequency that SCCs prescribed different types of flexibility exercise is presented in Table 3 . All SCCs physically tested players, which were predominantly conducted: during the pre-season (58%), all year round (46%), inseason (42%), at training camps (10%), and off-season (4%). Other responses included: "anthropometry each week/month", "depends on various factors", "in some cases after injury", and "winterbreak". The most reported physical tests used were to assess: cardiovascular endurance (92%), body composition (87%), muscular strength (81%), speed (81%), anthropometry (63%), muscular power (62%), acceleration (56%), flexibility (48%), agility (40%), anaerobic capacity (31%), and muscular endurance (8%). Athletewellbeing was monitored by 90% of coaches, via mobile device questionnaires (69%), verbal questionnaires (31%), and written questionnaires (15%). All SCCs used technology-based equipment, with global positioning systems (GPS) (94%), speed gates (73%), heart rate monitors (71%), electronic jump mats (50%), force plates (50%), mobile phone applications (40%), bar velocity trackers (35%), video analysis software (33%), body composition analyzers (31%), wearable technology (15%), and metabolic analysis devices (10%) being the most reported. Other responses included: "local positioning monitoring", "isometric and isokinetic dynamometry", and "isometric muscle test- Five open-ended questions were asked, allowing more detailed responses from SCCs, which were used to create higher order themes. The percentage of responses to each theme and exemplar responses are provided in Tables 4a-4e . This is the first study to investigate the practices of SCCs in professional soccer across different countries and leagues. A key finding was the high level of professional and academic certifications possessed by SCCs compared to surveys in other professional sports. Strength and conditioning certifications were held more commonly than SCCs in swimming (58%) [20] and rugby union (56%) [19] . Furthermore, over half of SCCs also had soccer coaching certifications, which has not been addressed in prior surveys. Obtaining a recognized strength and conditioning certification is considered important for personal development, quality assurance and employability [3, 24, 25] . Whereas soccer certifications provide underpinning theoretical and practical expertise, allowing SCCs to utilize their strength and conditioning knowledge to program soccer specific exercises and activities [1, 3] . Most notably, a quarter of SCCs held a PhD which is considerably higher than reported in prior surveys across different sports [11, 19] . The level of academic qualifications held by this generation of SCCs is possibly supported by higher education programs building stronger links with professional strength and conditioning organizations and sports teams [26] . Whereas, to obtain a job as a SCC it is often a prerequisite for candidates to possess higher degrees in a related field [24, 25] , particularly in professional sport. In support of transitioning from academia to the workplace, it was observed a high percentage of SCCs completed an internship. This is unsurprising given internships allow progressing SCCs to apply theoretical and practical knowledge/skills, improve self-efficacy, develop soft skills, and increase employment opportunities [3, 27, 28] . Periodization strategies were extensively used by SCCs in professional soccer, and to a larger extent than reported in other professional sports 69-91% [15] [16] [17] [18] [19] . Research has demonstrated in professional soccer, the use of block periodization over four seasons, improved performance (i.e., points tally), which was attributed to an increased focus on sport-specific speed development during the re- Lack of Facilities / Equipment / Staffing "Player:Coach ratio is often a challenge with relatively large playing squads (>20) and low numbers of staff (1-2)" and "Lack of money and people". 15% 6 Individualization of Training "Differentiation between game-players and reserves" and "Volume of athletes programmed for -thus inability to individualize". 10% *Some coaches detailed more than one response. Which was further sub-divided amongst the themes created. "Brilliant Basics -we continually strive to get the basics" and "Probably not. I'd be interested to see any program that is labelled unique. The basics done well and consistently is the best formula in my mind". 2 Miscellaneous "Consequence, respect the demands of the job on the pitch / in the gym" and "We support both academic and sports development until the under 23's age group, therefore, promote holistic development of players". 3 Sport Specific / Individualized Training "Soccer specific movements and gestures" and "We try to individualize as much as we can, even within collective training sessions". 13% 4 Periodization "Acceleration, change of direction and agility training is progressed through a continuum" and "We us periodization four our strength and power program, so we do 2 sessions (upper and lower) and currently progressing through a block periodization so will work through 6 weeks of hypertrophy, 6 weeks of max strength and 6 weeks of power. "Certain positions will work more than others on movements associated to their player profile, e.g., an explosive winger will do more ballistic type stuff, and central midfielder do more lunging type stuff throughout all planes" and "We use GPS to track player load according to the individualized match activity (or position average) and individualized top speed velocity. This allows us to individualize every pitch session (sport related or strength and conditioning) according to the specific needs of each position". Screening / Well Being / Testing "We try to develop players weaknesses based off pre-screening" and "I use the maximum speed reached during last stage of 30-15 Intermittent Fitness Test (VIFT) to individualize training" and "Based on testing and how the athlete is feeling". "Individual workloads are prescribed based off match performance (e.g., distance covered, high velocity running)" and "Training is individualized off weekly loads". Facilities / Staffing "We currently perform strength sessions in a circuit because of limited racks available so players are put into specific training groups and rotated weekly to do the session in the optimum order" and "Larger gym and improved coach:athlete numbers". Individualization "Yes I would individualize even more deeply, every strength and conditioning session will be individualized for every athlete" and "More attention to detail with each individual". Miscellaneous "A lot of players and clubs would benefit if they invest more in a long term athletic performance enhance" and "Less time foam rolling, more time building fluid movements through mobility, movement competency types sessions". No n/a 10% 7 Yes (No Elaboration) n/a 6% *Some coaches detailed more than one response. Which was further sub-divided amongst the themes created. tric-overload training conducted 1-2 times per week with professional soccer players, improves lean mass, half squat power and 40-m sprint time, while reducing fat mass [31] . Yet, more traditionally SCCs believed the most important exercise for professional soccer players was the squat and associated derivatives (see Table 2 ), which is similar to previous surveys in other professional sports [15] [16] [17] [18] [19] [20] . Supportively, developing maximal squat strength during a competitive season in professional soccer players, has shown improved sprint performance over 5, 10 and 20 m [32] . Olympic weightlifting was also widely implemented by SCCs, but less than in other professional sports (88-95%) [15, 16, 18, 19] , with the most prescribed lifts being derivatives (i.e., hang clean, jumps shrugs). Derivative lifts can be just as effective for improving athletic movements (e.g., triple extension) when performed with maximum intent, while also being less time demanding and complex to learn [33] . This is potentially a reason for coaches using derivatives more commonly given a reported "lack of time with players", "limited facilities and staffing", and "focusing on the basics" (see Tables 4a, 4b and 4d . Different speed development exercises were implemented by SCCs in professional soccer (i.e., strength training, plyometrics, maximum alization phase [29] . However, SCCs also reported challenges with designing and implementing periodized plans, due to "balancing strength and conditioning practices with tactical and technical work due to limited training days" and "frequency of match days" (see Table 4a . This was apparent in-season where a maintenance approach was adopted by reducing workloads for strength development programs, compared to the off-season. Research suggests a single weekly maintenance session over 12-weeks in professional soccer players maintains strength and power gained during prior developmental periods [30] . Whereas, set loads prescribed by SCCs during strength sessions were mostly athlete dependent. This concurs with open-ended responses, such as: "we try to individualize as much as we can" and "this allows us to individualize every pitch session (sport related or strength and conditioning)" (see Tables 4b and 4c ). However, individualized training was a big issue faced by SCCs and something they wanted to further integrate into their programs given unlimited time and resources (see Table 4d ). Concentric and eccentric training were the most common modes of resistance exercises prescribed, whereas other contemporary methods were also used (e.g., isoinertial/flywheel). Research suggests, in-season whole body (i.e., upper body, lower body and core) eccen- 1 Technology "Less decision making with more artificial intelligence and machine learning" and "Cognitive / virtual reality" and "The combination of wearable technology and video analysis". 2 Individualization "Training sessions will be more and more individualized. The time to bring all players together to work collectively will reduce in the future" and "More specialized training on position and associated movements". 3 Miscellaneous "Athletes will be stronger, faster and will have to play more often with congestive fixtures" and "I think more online sessions will occur as a result of COVID-19 and the ability to adapt to this". "Individualized strength and conditioning outside of the club" and "I believe players will build their own performance team and employ individual SCCs". Prehabilitation / Injury Reduction "Greater understanding of performance profiling and its links to performance and injury risk" and "Increased focus on injury prevention". Back to Basics "I feel the field will move away from all the data we currently have. Top teams sometimes have more measures than they can make use of, I think teams will go back to basic measures or a limited number of relevant measures" and "Going back to using less tech and back to person to person coaching". 8 Specialized Staff "Integration of football psychologists" and "Segmentation of all roles, i.e., strength and power coach, speed coach, fitness coach". *Some coaches detailed more than one response. Which was further sub-divided amongst the themes created. Biology of Sport, Vol. 38 No3, 2021 385 Contemporary practices of strength and conditioning coaches in professional soccer speed training and sport-specific movements). Possibly demonstrating soccer players are being trained across the force-velocity continuum, with the inclusion of sport-specific movements to transfer speed improvements to sports performance. Research in netball has demonstrated that coupling sport specific movements to either strength or power training programs improved throwing velocity by 12.4% and 8.8% respectively [34] . Therefore, suggesting SCCs should utilize sport-specific movements to promote sport-specific high velocity adaptations [34] . Plyometric exercises were mostly prescribed all year round, and used more frequently than in other professional sports (15-57%) [15] [16] [17] [18] [19] . The reasons for using plyometrics aligned with research recommendations in professional soccer, to improve lower body power, speed, jump height and reduce injuries [35] . Similar to rugby union plyometrics were mostly prescribed as complex training [19] . However, research in professional soccer has suggested combining strength and plyometric training compared to strength training alone, shows no additional improvements to performance in strength, power and speed tests [36] . Nonetheless, complex training is a time efficient method for integrating strength and plyometric work within the same program [37] . Comparable to American football [15] multiple hops/lunges and bounding, were the most prescribed plyometric exercises in this study. This is logical given these exercises effectively develop the stretch-shortening cycle, enabling soccer players to perform explosive muscular contractions and improve rapid force development [35] . Physically testing players was predominantly conducted during the pre-season, whereas a large proportion of SCCs tested players all year round. It has been shown that significant changes occur in different physical fitness and performance capacities (e.g., lower body power, flexibility, agility, aerobic and anaerobic fitness) across a season in professional soccer [38] . Therefore, monitoring changes in player's physical fitness throughout a season, allows SCCs to provide benchmarks for players returning from injury, observe decrements in performance, and ascertain if physical training programs have been effective [38] . Cardiovascular endurance was the most utilized physical test, which is practical given players peak heart rates reach 85-98% of maximal values and average oxygen uptake is approximately 70% of maximum values in professional soccer matches [4] . Technology-based equipment and in particular GPS was widely used by SCCs in professional soccer. Open-ended questions revealed GPS was used to "track player load according to the individualized match activity (or position average) and individualized top speed velocity". Research recommends tracking total training load, external responses to training load, positional match-play demands, and exposures to high-speed running to optimize training programs and reduce injuries [10] . Also, SCCs in this study commonly monitored athlete-wellbeing, predominantly through mobile device questionnaires. Self-reporting techniques such as informal questionnaires, are valid for players to declare their fatigue and wellbeing levels [39] . Furthermore, this information can be used to have informed discussion with players, and make decisions whether to modify set loads, training intensity, training volume and/or provide player support [39] . 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