FSI Selected Publications of the Week

1. Effects of Caffeine Supplementation on Physical Performance of Soccer Players: Systematic Review and Meta-Analysis.
Ferreira RES, Pacheco RL, de Oliveira Cruz Latorraca C, Riera R, Eid RG, Martimbianco ALC. 

Centro Universitário São Camilo, São Paulo, SP, Brazil.

This systematic review with meta-analysis of 16 Randomized clinical trials (RCTs) assessing the effects of caffeine on the performance of soccer players found no differences reported between caffeine and placebo when assessing soccer-related performance parameters such as aerobic endurance, time to fatigue, vertical jump, repeated sprint tests, reaction time agility test, and rating of perceived exertion. However, a few minor adverse events from caffeine were reported.

Sports Health. 2021 Mar 5:1941738121998712. doi: 10.1177/1941738121998712


2. Relationships Between Aerobic Performance, Hemoglobin Levels, and Training Load During Small-Sided Games: A Study in Professional Soccer Players.
Younesi S, Rabbani A, Clemente FM, Silva R, Sarmento H, Figueiredo AJ.

University of Coimbra, Research Unit for Sport and Physical Activity, Faculty of Sport Sciences and Physical Education, Coimbra, Portugal.

This study in 16 professional soccer players finds relationships between the maximum speed reached (VIFT) during the 30-15 Intermittent Fitness Test, the players’ hemoglobin levels, and the training load measures during standardized 3 vs. 3 Small Side Games SSGs. Large-to-very-large relationships were found between VIFT and external loads: TD and MW. And moderate-to-large negative relationships were found between hemoglobin levels and internal loads: Edwards’ TRIMP, %HRmax, and red zone. The use of SSGs protocols as a monitoring complement of the 30-15IFT is suggested.

Front Physiol. 2021 Feb 16;12:649870. doi: 10.3389/fphys.2021.649870. eCollection 2021


3. The effects of 14-week betaine supplementation on endocrine markers, body composition and anthropometrics in professional youth soccer players: a double blind, randomized, placebo-controlled trial.
Nobari H, Kargarfard M, Minasian V, Cholewa JM, Pérez-Gómez J.

Department of Exercise Physiology, Faculty of Sport Sciences, University of Isfahan, Isfahan, Iran.

Betaine (Trimethylglycine – TMG) supplementation (2 g/day) increased testosterone levels and T/C ratio in 15 youth professional soccer players (age 15 years) during a competitive season, with no negative effects on growth (height and weight) and so may attenuate reductions in testosterone due to intense training during puberty.

J Int Soc Sports Nutr. 2021 Mar 4;18(1):20. doi: 10.1186/s12970-021-00417-5


4. External and internal loads during the competitive season in professional female soccer players according to their playing position: differences between training and competition.
Moraleda BR, Nedergaard NJ, Morencos E, Casamichana D, Ramirez-Campillo R, Vanrenterghem J.

Department of Physical Education, Sport and Human Movement, Universidad Autónoma de Madrid, Madrid, Spain.

External Load EL (total distance covered; high-speed running distance; number of accelerations and decelerations) and Internal Load IL (RPE) were assessed in 18 elite female soccer players from a Spanish 1st Division team during one season. The EL and the IL from official matches were higher compared to training sessions. In matches, the EL was greater in Attackers and Central Midfielders versus Central Backs, while during training sessions, the EL was similar between playing positions.

Res Sports Med. 2021 Mar 4:1-13. doi: 10.1080/15438627.2021.1895781


5. Prevalence of Inflammatory Heart Disease Among Professional Athletes With Prior COVID-19 Infection Who Received Systematic Return-to-Play Cardiac Screening.
Martinez MW et al.

Morristown Medical Center, Atlantic Health System, Morristown, New Jersey.

The major North American professional sports leagues including MLS implemented between May and October 2020 a conservative return-to-play (RTP) cardiac testing program for all athletes (n=789) testing positive for COVID-19. Troponin testing, electrocardiography, and resting echocardiography were performed. Abnormal screening results were identified in 30 athletes (3.8%); and 5 athletes (0.6%) ultimately had cardiac magnetic resonance imaging findings suggesting inflammatory heart disease (myocarditis, 3; pericarditis, 2) that resulted in temporary restriction from play, with no adverse cardiac events when professional sport participation was resumed.

JAMA Cardiol. 2021 Mar 4. doi: 10.1001/jamacardio.2021.0565


6. Factors Influencing Creatine Kinase Response in Youth National Team Soccer Players.
Schuth G, Szigeti G, Dobreff G, Revisnyei P, Pasic A, Toka L, Gabbett T, Pavlik G.

Department of Sports Medicine and Sport Science, Hungarian Football Federation, Budapest, Hungary.

Training and match load, and CK values were measured on 41 U16-U17 youth national team soccer players over an 18-month period. The prediction Load-CK models fitted similarly during games and training sessions, but the accuracy was better during training sessions. Position-specific differences were found in the load parameters, which best explained the CK changes, indicating that relationship between external/internal load parameters and CK changes are position-specific and might depend on the type of session (training or match).

Sports Health. 2021 Mar 4:1941738121999387. doi: 10.1177/1941738121999387


7. Effect of Early Residual Laxity After Anterior Cruciate Ligament Reconstruction on Long-term Laxity, Graft Failure, Return to Sports, and Subjective Outcome at 25 Years.
Lindanger L, Strand T, Mølster AO, Solheim E, Inderhaug E.

Department of Orthopedics, Haraldsplass Deaconess Hospital, Bergen, Norway.

Study of 151 soccer, handball, and basketball players with KT-1000 arthrometer at 6-month after anterior cruciate ligament reconstruction (ACLR) using bone-patellar tendon-bone graft, and follow-up for 25 years average, showed that the n = 20 with a slightly loose graft (3 to 5 mm increase from the uninvolved side), despite a rate of return to preinjury level of sports similar to those with tight grafts (<3mm), showed a median duration of the sports career shorter (2 vs 6 years), more need of surgical revision (30 % vs 6%), permanent increased anterior laxity, and an inferior Lysholm score.

Am J Sports Med. 2021 Mar 3:363546521990801. doi: 10.1177/0363546521990801


8. Curve Sprint in Elite Female Soccer Players: Relationship with Linear Sprint and Jump Performance.
Kobal R, Freitas TT, Fílter A, Requena B, Barroso R, Rossetti M, Jorge RM, Carvalho L, Pereira LA, Loturco I.

Sport Club Corinthians Paulista, São Paulo 03828-000, Brazil, Football Science Institute (FSI), 18016 Granada, Spain.

This study in 17 professional female soccer players found nearly perfect associations (r > 0.9) between linear and curve sprint (CS) velocities, and both were significantly correlated with the jumping ability, suggesting that both may benefit from the implementation of plyometric exercises. For change of direction (COD), players faster in linear and curve sprints exhibited greater COD deficits, and no significant associations were found between these deficits and either body mass, sprint momentum, or jumping ability, suggesting a different mechanics and training methodology for the COD.

Int J Environ Res Public Health. 2021 Feb 26;18(5):2306. doi: 10.3390/ijerph18052306


9. Effects of an eccentric overload and small-side games training in match accelerations and decelerations performance in female under-23 soccer players.
Nevado F, Torreblanca V, Paredes V, Del Campo J, Balsalobre C.

Applied Biomechanics and Sports Technology Research Group, Autonomous University of Madrid, Madrid, Spain.

This study in 23 female soccer players from a Spanish professional club divided into three training groups: small-sided game group (SGG), eccentric overload group (EOG) and a control group (CG), found that the SSG training obtained mainly improvements in variables related with efforts repetitions and the capacity of minimize the accelerations ACC and decelerations DCC deficit at the end of the games, while the EOG training was related to increments in the intensity of ACC and DCC.

J Sports Med Phys Fitness. 2021 Mar;61(3):365-371. doi: 10.23736/S0022-4707.20.11232-5