FSI Football Science Update

1. Strength training in professional soccer: effects on short-sprint and jump performance.

Nuñez J, Suarez-Arrones L, de Hoyo M, Loturco I

University of Pablo de Olavide of Sevilla, Spain & Football Science Institute

Int J Sports Med. 2021 Sep 24. doi: 10.1055/a-1653-7350

The aim of this meta-analysis was to determine the effects of different strength training protocols on short-sprint and vertical jump performance of elite professional soccer players. Overall, the different strength-oriented training schemes produced similar improvements, that cannot be attributed to strength training in isolation, and with lower effect when applied during in-season than in pre-season periods.


2. Screening Hamstring Injury Risk Factors Multiple Times in a Season Does Not Improve the Identification of Future Injury Risk

Opar DA, Ruddy JD, Williams MD, Maniar N, Hickey JT, Bourne MN, Pizzari T, Timmins RG

Australian Catholic University, Fitzroy, Victoria, Australia

Med Sci Sports Exerc. 2021 Sep 20. doi: 10.1249/MSS.0000000000002782

In this study, across two competitive seasons, 311 Australian Football players had their eccentric knee flexor strength during the Nordic hamstring exercise and BFlh architecture assessed at the start and end of the preseason and in the middle of the competitive season. 74 HSI injuries were recorded. Shorter BFlh fascicles (<10.42 cm) increased HSI risk (RR = 1.9), as between-limb eccentric strength imbalance (>9%) (RR = 1.8), and prior HSI (RR = 2.9). The ability of a logistic regression model combining these 3 factors to identify which players would sustain an HSI, however, did not improve with more frequent measures across a season.


3. Comparison of Immediate Effects of Foam Rolling and Dynamic Stretching to Only Dynamic Stretching on Flexibility, Balance, and Agility in Male Soccer Players

Seçer E, Özer Kaya D

J Sport Rehabil. 2021 Sep 20:1-7. doi: 10.1123/jsr.2021-0017

In this study, 30 male soccer players (mean age 18.8 y) performed 2 sessions (Dynamic Stretching DS and DS + Foam Rolling FR) on separate occasions in a randomized order, with an interval of 72 hours. Significant improvement in flexibility (sit-and-reach test) and agility (T test) were observed in both conditions, and DS + FR was not superior to DS at improving flexibility and agility as compared only with DS.


4. Monitoring post-match fatigue during a competitive season in elite youth soccer players

Evans DA, Jackson DT, Kelly AL, Williams CA, McAuley ABT, Knapman H, Morgan PT

University of Exeter, Exeter, Devon, United Kingdom

J Athl Train. 2021 Sep 20. doi: 10.4085/1062-6050-0245.21

This study examined 16 soccer players (18 ± 1 years) participating in 36 English Football League Youth Alliance League fixtures. Match accelerations and decelerations (AD) were predictive of wellness questionary sub-units energy and stress and of total wellness 2 days post-match (MD+2). Stress, sleep, and total wellness 5 days pre-match (MD-5) were predictive of AD output during the subsequent match.


5. Integrating video tracking and GPS to quantify accelerations and decelerations in elite soccer

Pons E, García-Calvo T, Cos F, Resta R, Blanco H, López Del Campo R, Díaz-García J, Pulido-González JJ

Sports Performance Area, FC Barcelona, Barcelona, Spain

Sci Rep. 2021 Sep 17;11(1):18531. doi: 10.1038/s41598-021-97903-2

This study analyzed the degree of agreement comparing number and distance covered in different acceleration and deceleration sections registered by a video tracking system (MEDIACOACH) and a GPS device (WIMU PRO) during the official competition of a Spanish professional club over the course of a season. Data presented more bursts of accelerations and decelerations in WIMU PRO than in MEDIACOACH, whereas the distances covered recorded by both systems were similar. The differences in means across the two devices were trivial or small for most variables, and agreement and consistency between systems showed good and excellent values. Both systems demonstrated an acceptable degree of agreement and could be useful in analyzing players’ acceleration demands in professional soccer. However, caution is required when interpreting the results and a comparison with a gold standard is required in order to validate both systems.


6. A longitudinal cohort study of adolescent elite footballers and controls investigating the development of cam morphology

Fernquest S et al

Botnar Research Centre, Old Road, Oxford, UK

Sci Rep. 2021 Sep 17;11(1):18567. doi: 10.1038/s41598-021-97957-2

This study analyzed 121 male academy footballers and 107 male and female controls during 3 years with MRI and questionnaires to characterize the change in hip and growth plate anatomy and quantify activity levels. Footballers experienced significantly greater increases in femoral head asphericity than controls, and a positive correlation existed between activity levels and change in femoral head morphology. The greatest morphological change occurred in individuals aged 11-12 years at baseline, with no significant change in individuals aged 14 years and older at baseline. Cam morphology development was secondary to soft tissue hypertrophy and lateral growth plate extension. In conclusion, excessive loading of the hip joint through exercise prior to 14 years of age may result in growth plate adaptations causing cam morphology. Potential interventions may include training type and load modification in young adolescent football players.


7. Effects of 30 days of ketogenic diet on body composition, muscle strength, muscle area, metabolism, and performance in semi-professional soccer players

Paoli A, et al

University of Padua, Padua, Italy

J Int Soc Sports Nutr. 2021 Sep 16;18(1):62. doi: 10.1186/s12970-021-00459-9

This study randomly assigned semi-professional soccer players to an iso-protein (1.8 g/Kg body weight/day) either ketogenic diet (KD) or western diet (WD) for 30 days. There was a significantly higher decrease in body fat, visceral adipose tissue, waist circumference, and extra-cellular water in KD compared to the WD group. Lean soft tissue, quadriceps muscle area, maximal strength, and resting energy expenditure REE showed no changes in both groups. Respiratory exchange ratio RER decreased significantly in KD. Yo-yo intermittent test improved significantly in both groups without significant differences. CMJ significantly improved only in KD. Thus, KD athletes lost fat mass without any detrimental effects on strength, power, and muscle mass.


8. The Effect of High-Intensity Accelerations and Decelerations on Match Outcome of an Elite English League Two Football Team

Rhodes D, Valassakis S, Bortnik L, Eaves R, Harper D, Alexander J

Football Performance Hub, University of Central Lancashire, Preston, UK

Int J Environ Res Public Health. 2021 Sep 21;18(18):9913. doi: 10.3390/ijerph18189913

This study in 26 elite outfield footballers from an elite English Football League 2 (EFL) team utilized GPS to quantify high-intensity accelerations and decelerations during 45 games in a competitive season. Significant effects of results were observed with the highest outputs observed in games won.


9. How Positional Constraints Affect Footedness in Football: A Notational Analysis of Five Leagues in Europe

Marcori AJ, Giovanini B, Monteiro PHM, Nascimento VB, Brito de Souza D, Okazaki VHA

School of Physical Education and Sports, University of São Paulo, Brazil

J Mot Behav. 2021 Sep 27:1-9. doi: 10.1080/00222895.2021.1980367

This study analyzed 1826 games from the 2017/18 season, divided between Spanish LaLiga (380 matches); Italian Serie A (380 matches); English Premier League (380 matches); German Bundesliga (306 matches); and French Ligue 1 (380 matches). Results revealed asymmetrical proportions of foot selection, favoring the preferred foot for right- and left-footed athletes. The frequency of preferred foot selection increased as a function of distance from the target (i.e., the farther the athlete, the higher the percentage of preferred foot selection). Shots taken from the left side were more often performed with the right foot and vice-versa, both for left- and right-footed athletes, and the success rate did not vary between limbs in any position.