FSI Football Science Update

1. The Potential Role of Hamstring Extensibility on Sagittal Pelvic Tilt, Sagittal Spinal Curves and Recurrent Low Back Pain in Team Sports Players: A Gender Perspective Analysis.

Cejudo A, Centenera-Centenera JM, Santonja-Medina F.

Faculty of Sport Sciences, University of Murcia, Spain

Int J Environ Res Public Health. 2021 Aug 16;18(16):8654. doi: 10.3390/ijerph18168654

This study in 94 soccer and basketball players (61 man and 33 woman) with (n = 36) and without (n = 58) recurrent lower back pain LBP found that low Hamstrings Extensibility was associated with maximum trunk forward flexion and lumbar curve in both genders, and with lower back pain in male players. Also low Hamstrings Extensibility predicted lower back pain in male players, and 100% of male players with recurrent lower back pain had low Hamstrings Extensibility. 


2. Hamstring Strain Injury (HSI) Prevention in Professional and Semi-Professional Football Teams: A Systematic Review and Meta-Analysis.

Biz C, Nicoletti P, Baldin G, Bragazzi NL, Crimì A, Ruggieri P.

Department of Surgery, Oncology and Gastroenterology (DiSCOG), University of Padua, Italy

Int J Environ Res Public Health. 2021 Aug 4;18(16):8272. doi: 10.3390/ijerph18168272

This literature search of PubMed/MEDLINE, ISI/Web of Science and Scopus databases with meta-analysis of six studies provided strong evidence that exercise interventions – Nordic hamstring exercise, the FIFA 11+ programme and exercises for core stability or balance training – are effective in reducing hamstring injuries, with effect size of 0.443. 


3. Effects of Match Location, Quality of Opposition and Match Outcome on Match Running Performance in a Portuguese Professional Football Team.

Teixeira JE, Leal M, Ferraz R, Ribeiro J, Cachada JM, Barbosa TM, Monteiro AM, Forte P.

Research Centre in Sports Sciences, Vila Real, Portugal. 

Entropy (Basel). 2021 Jul 29;23(8):973. doi: 10.3390/e23080973

This study in 23 male professional football players from 18 Portuguese Football League matches during the 2019-2020 season found that Central Midfielders and Wide Midfielders covered significantly greater total distance and average speed. Wide Midfielders and Fullbacks covered higher distances at high-speed running and sprinting, and Wide Midfielders showed the highest number of accelerations and decelerations. The match running performance was influenced by match location, quality of opposition and match outcome.


4. Quantifying Accelerations and Decelerations in Elite Women Soccer Players during Regular In-Season Training as an Index of Training Load.

Douchet T, Humbertclaude A, Cometti C, Paizis C, Babault N.

Center for Performance Expertise, University of Bourgogne-Franche-Comté, Dijon, France. 

Sports (Basel). 2021 Jul 31;9(8):109. doi: 10.3390/sports9080109

In this study, changes in the training load were monitored during two different selected weeks (considered a “low week” and a “heavy week”) during the in-season in 12 elite soccer women playing in the French first division.  During the heavy week, the training load was significantly greater than the low week when considering number of ACC >2 m·s-2, number of DEC < -2 m·s-2, and ACC and DEC showed significant correlations with most outcomes: HR%, total distance, distance per min, sprint number, Hooper index, DOMS E, Fatigue E, RPE, and session RPE. It is concluded that, for elite women soccer players, quantifying ACC and DEC alongside other indicators seemed to be essential for a more complete training load monitoring.


5. External and Internal Load Measures During Preseason Training in Men Collegiate Soccer Athletes.

Fields JB, Merigan JM, Gallo S, White JB, Jones MT.

Department of Exercise Science and Athletic Training, Springfield College, Springfield, Massachusetts

J Strength Cond Res. 2021 Sep 1;35(9):2572-2578. doi: 10.1519/JSC.0000000000004092

Morning Cortisol positively predicted afternoon external load and post-training RPE; Testosterone:Cortisol ratio negatively predicted afternoon external load and post-training RPE; and morning Heart Rate Variability negatively predicted post-training RPE. Despite reduced hormonal stress and external load across weeks, negative perceptions of fatigue increased, suggesting fatigue patterns may have a delayed response. Load may have a more belated, chronic effect on perceptions of fatigue, whereas hormonal changes may be more immediate and sensitive to change. 


6. Incidence of injury in adult elite women’s football: a systematic review and meta-analysis.

Mayhew L, Johnson MI, Francis P, Lutter C, Alali A, Jones G.

Musculoskeletal Health Research Group, School of Clinical and Applied Science, Leeds Beckett University, UK. 

BMJ Open Sport Exerc Med. 2021 Jul 13;7(3):e001094. doi: 10.1136/bmjsem-2021-001094

This systematic review and meta-analysis included 12 studies sampling 129 teams. In domestic club football, injury incidence rate in adult elite women’s football was estimated to be 5.7/1000 hours (total), 19.5/1000 hours (match) and 3.1/1000 hours (training). In tournament, football match incidence was estimated to be 55.7/1000 hours. The knee (22.8%) was the most common site of injury in domestic club football, while the ankle (23.7%) was the most common site of injury in tournament football. Ligament sprains were the most common type of injury (27.8%), followed by muscle strains (19.1%). 


7. Physical preparation and return to performance of an elite female football player following ACL reconstruction: a journey to the FIFA Women’s World Cup.

Taberner M, van Dyk N, Allen T, Jain N, Richter C, Drust B, Betancur E, Cohen DD.

School of Sport and Exercise Sciences, Liverpool John Moores University, UK.

BMJ Open Sport Exerc Med. 2020 Dec 1;6(1):e000843. doi: 10.1136/bmjsem-2020-000843

This case report describes the return to sport and return to performance of an elite female football player following ACLR and her journey to the FIFA Women’s World Cup, including the gym-based physical preparation and the on-pitch/sports-specific reconditioning. 


8. Why are female soccer players experiencing a concussion more often than their male counterparts? A scoping review.

Blyth RJ, Alcock M, Tumilty DS.

School of Physiotherapy, University of Otago, Dunedin, New Zealand. 

Phys Ther Sport. 2021 Aug 8;52:54-68. doi: 10.1016/j.ptsp.2021.08.001

This systematic review searched several hypotheses to explain the increased concussion rates that are found in female soccer players. These include, reduced neck strength/anthropometrics, increased head acceleration, increased ball-to-head concussions, differences in hormones and brain structure/function, and reduced visual awareness. Despite this hypothesis generation there is scarce high-level evidence which is required to guide injury prevention and/or rule changes to protect female soccer players.


9. The dominant leg is more likely to get injured in soccer players: systematic review and meta-analysis.

DeLang MD, Salamh PA, Farooq A, Tabben M, Whiteley R, van Dyk N, Chamari K.

Texas Health Sports Medicine, Dallas/Fort Worth, USA. 

Biol Sport. 2021 Sep;38(3):397-435. doi: 10.5114/biolsport.2021.100265

This systematic review on 74 studies, with 36 of them eligible for meta-analysis, found that for prospective lower extremity injury studies, soccer players demonstrated a 1.6 times greater risk of injury to the dominant limb, and this was true across playing levels (amateurs, youths, professionals) and gender of the players.


10. Contemporary practices of strength and conditioning coaches in professional soccer.

Weldon A, Duncan MJ, Turner A, Sampaio J, Noon M, Wong DP, Lai VW.

Human Performance Laboratory, The Technological and Higher Education Institute of Hong Kong (THEi), Hong Kong. 

Biol Sport. 2021 Sep;38(3):377-390. doi: 10.5114/biolsport.2021.99328

This study describes an online survey on 52 strength and conditioning coaches from professional leagues across 18 countries. 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 made it difficult to periodize training programs and apply appropriate training loads. 


11. Differences in worst-case scenarios calculated by fixed length and rolling average methods in professional soccer match-play.

Oliva-Lozano JM, Martín-Fuentes I, Fortes V, Muyor JM.

Health Research Centre. University of Almería. Almería, Spain

Biol Sport. 2021 Sep;38(3):325-331. doi: 10.5114/biolsport.2021.99706

This study describes the worst-case scenarios (WCS) in professional soccer players calculated by fixed length and rolling average methods. A significant effect of the type of method used was found, with fixed length methods of different durations (1, 3, 5, 10 minutes) significantly underestimating the WCS of Total Distance, High-speed running distance and Sprint distance across the most common playing positions. Therefore, the application of rolling averages is recommended for an appropriate WCS analysis in professional soccer match-play.


12. Acute Effects of Foam Rolling on Blood Flow Measured by Ultrasonography in Soccer Players.

Alonso-Calvete A, Padrón-Cabo A, Lorenzo-Martínez M, Rey E.

Faculty of Education and Sport Sciences, University of Vigo, Pontevedra, Spain

J Strength Cond Res. 2021 Sep 1. doi: 10.1519/JSC.0000000000004125

This study analyzes acute effects of Foam Rolling FR – 2 sets, each with 45 seconds of FR and 15 seconds of rest between sets with a high-density foam roller in quadriceps, hamstrings, and iliotibial band – on blood flow parameters measured by Doppler ultrasonography in 12 soccer players. Results showed a significant increase in both maximal velocity and maximal volume of blood flow after intervention in comparison with pretest, but after 30 minutes, there were no significant differences, suggesting an acute effect that may contribute to the understanding of local physiological mechanism of FR.


13. Should we individualize training based on force-velocity profiling to improve physical performance in athletes?

Lindberg K et al.

Department of Sport Science and Physical Education, Faculty of Health and Sport Sciences, University of Agder, Kristiansand, Norway.

Scand J Med Sci Sports. 2021 Sep 2. doi: 10.1111/sms.14044

The present study aimed to examine the effectiveness of an individualized training program based on a Squat Jump force-velocity (FV) profiling on jumping, sprinting, strength, and power in athletes. Forty national level team sport athletes from ice-hockey, handball, and soccer completed a 10-week training intervention. A theoretical optimal squat jump (SJ)-FV-profile was calculated from SJ with 5 different loads (0, 20, 40, 60, 80 kg). Based on their initial FV-profile, athletes were randomized to train towards, away, or irrespective (balanced training) of their initial theoretical optimal FV-profile. There were no significant group differences for any of the performance measures: 10 and 30 m sprints, SJ and countermovement jump, 1RM squat, and a leg-press power test. The results from this study do not support the efficacy of individualized training based on SJ-FV-profiling.


14. Multiscale fractal dimension applied to tactical analysis in football: A novel approach to evaluate the shapes of team organization on the pitch.

Bueno MJO, Silva M, Cunha SA), Torres RDS), Moura FA.

Sport Sciences Department, State University of Londrina, Brazil. 

PLoS One. 2021 Sep 1;16(9):e0256771. doi: 10.1371/journal.pone.0256771

This study evaluates different shape descriptors applied to images of polygons that represent the organization of football teams on the pitch. The multiscale fractal curve-MFC descriptor presented the highest values of effectiveness. As a practical demonstration, MFC was applied for tactical analysis of an official match through a K-means clustering technique, and different shapes of organization could be identified throughout the match, making it possible to apply this descriptor in the analysis of professional football matches.


15. Perceived load, fatigue and recovery responses during congested and non-congested micro-cycles in international football tournaments.

Noor D, McCall A, Jones M, Duncan C, Ehrmann F, Meyer T, Duffield R.

Institute of Sports and Preventive Medicine, Saarland University, Germany.

J Sci Med Sport. 2021 Jul 9:S1440-2440(21)00177-8. doi: 10.1016/j.jsams.2021.07.001

Internal load (session-rating of perceived exertion [s-RPE]) and perceived ratings of fatigue, muscle soreness, psychological status, sleep quality, and sleep duration were recorded daily from 37 national team footballers during the competition phase of 3 international tournaments. Significantly higher s-RPE match loads within the single- and multi-match conditions resulted in significantly worsened subjective ratings of perceived fatigue, muscle soreness and sleep duration in the 24-48 h post-match. However, internal load profiles were not different between the Acute-Congestion or Non-congestion conditions.