As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

1 Prediction of talent selection in elite male youth soccer across 7 seasons: A machine-learning approach

Reference: J Sports Sci. 2024 Dec 17:1-14.
 doi: 10.1080/02640414.2024.2442850. Online ahead of print.
Authors: Stefan Altmann, Ludwig Ruf, Stefan Thiem, Tobias Beckmann, Oliver Wohak, Christian Romeike, Sascha Härtel
Summary: This study aimed to investigate the relative importance of parameters from several domains associated to both selecting or de-selecting players with regards to the next age group within a professional German youth soccer academy across a 7-year period. Following a mixed-longitudinal approach, physical, physiological, psychological, skill-, health-, age-, and position-related parameters were collected from 409 male players (980 datapoints) from the U12 to U19 age groups. Supervised machine learning classifiers were used to predict the selection status regarding the next age group. The XGBoost models (ROC-AUC: 0.69, F1-Score: 0.84) revealed that physical and physiological (linear sprint, change-of-direction sprint, countermovement jump, aerobic speed reserve) as well as skill-related parameters (soccer-specific skill) were most important for being selected or de-selected regarding the next age group across the entire sample and all age groups. The majority of psychological parameters (motive structure, motive attention, motive competition, cognitive flexibility) were of medium importance. No clear pattern was observed for the health-, age-, and position-related parameters. Our study provides insights into key parameters for talent selection thereby contributing to an overall talent management strategy in highly trained youth soccer players. In particular, coaches and key stakeholders might focus on physical, physiological, and skill-related parameters.

2 Identification of Game Periods and Playing Position Activity Profiles in Elite-Level Beach Soccer Players Through Principal Component Analysis

Reference: Sensors (Basel). 2024 Dec 2;24(23):7708. doi: 10.3390/s24237708.
Authors: Pau Vaccaro Benet, Alexis Ugalde-Ramírez, Carlos D Gómez-Carmona, José Pino-Ortega, Boryi A Becerra-Patiño
Download link: https://pmc.ncbi.nlm.nih.gov/articles/PMC11645014/pdf/sensors-24-07708.pdf
Summary: Beach soccer has gained increasing interest for study in the sports sciences. In this sense, the analysis of activity profiles is important for training design and load individualization. Therefore, the aims of this study were to identify the most important variables to assess the activity profile and to compare them according to the playing position and game periods in international beach soccer matches. A total of 19 matches of the Spanish national beach soccer team were analyzed during their participation in different international competitions during the 2021-2022 season. A Principal Component Analysis (PCA) was applied to objectively select the external load variables that best explain the data. Kaiser-Meyer-Olkin values of 0.705 and Bartlett’s Sphericity (p < 0.01) were obtained. Kruskal-Wallis and Friedman tests was performed for playing positions and game period comparisons, respectively. The PCA showed seven components that grouped a total of 20 variables, explaining 66% of the total variance. Only PC1 and PC2 explained more than 15% (23% and 17%, respectively). Differences were found between playing positions (H > 22.73; p < 0.01) and between game periods (X2 > 16.46; p < 0.01). A significant decrease was found throughout the game, with the highest demands in period 1 and the lowest in period 3. The highest workloads were performed by wingers and the lowest by goalkeepers. The differences between positions and game periods were found in the following: Total Distance (m/min), HIBD (m/min), High Acc (m/s), High Dec (m/s), Acc 1-2 m/s2 (m), Acc 2-3 m/s2 (m), Imp 4-5G (n), Imp 5-6G (n), Sprint (n), and Dec 10-6 m/s2 (m) (p < 0.01). In conclusion, physical and tactical demands faced by elite-level beach soccer players will be influenced by playing positions and game periods. Coaches needs to develop position-specific training programs and optimize substitution strategies for enhancing overall team performance.

3 Neuromuscular Fatigue in Hamstring and Quadriceps Muscles Following Simulated Soccer Match-Play and Typical Training Sessions

Reference: Med Sci Sports Exerc. 2024 Dec 18. doi: 10.1249/MSS.0000000000003633. Online ahead of print.
Authors: Anasthase Massamba, Nabil Kouzkouz, Bernard Geny 1, Fabrice Favret, Thomas J Hureau
Summary: This study investigated the mechanisms of neuromuscular fatigue and recovery in quadriceps and hamstring muscles following soccer match-play and typical training sessions dedicated to the physical development of players. Fifteen male professional academy soccer players completed at different visits a 90-minute simulated soccer match-play (MATCH) and four training sessions modulating the metabolic nature (HIIT vs. SPRINT) and the mechanical load (number of changes of direction [COD]). Neuromuscular fatigue was evaluated via changes in pre to postexercise maximal voluntary contraction (MVC), potentiated twitch force (PTw, peripheral fatigue) and voluntary activation (VA, central fatigue) evoked by electrical stimulation in quadriceps and hamstring muscles. External load was assessed via GPS units. Following MATCH, ΔMVC was similar between quadriceps (-18.3 ± 11.6%) and hamstring (-23.2 ± 10.6%) muscles. However, hamstring muscles displayed greater ΔPTw (-27.2 ± 25.0% vs. -17.2 ± 10.9%), but lower ΔVA (-8.2 ± 14.0% vs. -18.1 ± 12.7%) than quadriceps muscles. Quadriceps and hamstring muscles fatigue recovered 24 h post-match. Increasing the mechanical load (number of COD) increased the magnitude of neuromuscular fatigue in quadriceps but not in hamstring muscles. Modulating the metabolic nature of the session (SPRINT vs. HIIT) did not influence neuromuscular fatigue in either muscle group. No correlation was found between ΔMVC and a fatigue index derived from GPS metrics for any muscle groups (r2 < 0.06, P > 0.38). The magnitude and etiology of neuromuscular fatigue were modulated by the muscle group investigated and the mechanical load of the exercise task. Moreover, the ‚fatigue index‘ derived from GPS metrics is not a valid surrogate of neuromuscular fatigue on the field.

4 Return to Soccer After Anterior Cruciate Ligament Reconstruction: An Outcome or a Decision?

Reference: Orthop J Sports Med. 2024 Dec 18;12(12):23259671241295834. doi: 10.1177/23259671241295834. eCollection 2024 Dec.
Authors: Isabelle Hållén, Joanna Kvist, Magnus Forssblad, Alexander Sandon
Download link: https://pmc.ncbi.nlm.nih.gov/articles/PMC11653463/pdf/10.1177_23259671241295834.pdf
Summary: The return-to-sports rate is often used as an outcome measure after anterior cruciate ligament (ACL) reconstruction (ACLR). Although most soccer players want to return to sports after their ACL injury, up to 40% do not believe they will return to soccer after their ACL injury. The aim was to investigate whether self-reported presurgical beliefs regarding return to soccer correspond to registered official match participation after ACLR. Included were soccer players with a primary unilateral ACL injury who were ≥15 years at the time of ACLR and who had completed a presurgical question about their future sports participation beliefs. ACLR surgical data were extracted from the Swedish National Knee Ligament Registry, and game participation data were extracted from the Swedish Football Association’s administrative data system. A total of 959 soccer players (617 [64%] male and 342 [36%] female) were included. The follow-up time after ACLR ranged from 18 months to 5.5 years. Of 720 soccer players (75%) who believed that they would return to play (RTP), 462 (64%) players actually did. Of the players who believed that they would not RTP, 181 (76%) did not. Presurgical beliefs predicted RTP (odds ratio [OR], 5.59; P < .001). Younger age at the time of ACLR favored RTP, where 61% of the players aged 15-20 years had RTP (OR, 3.85; P < .001). At the top competitive level, 84% of the players RTP compared to 14% at the recreational level. Players active at higher levels were more likely to believe that they would RTP, and they also actually did so (OR, 33.06; P < .001). Overall, 67% of players followed their presurgical intention to return to soccer. The findings indicated that presurgical beliefs, age, and level of play helped to predict the actual RTP of soccer players after ACLR.

5 Evaluation of the impact of a 3-week specific-sport rehabilitation program on neuromotor control during single-leg countermovement-jump tests in professional soccer players with lower-limb injuries

Reference: Front Sports Act Living. 2024 Dec 5:6:1448401. doi: 10.3389/fspor.2024.1448401. eCollection 2024.
Authors: Geoffrey Memain, Christopher Carling, Jean Bouvet, Pascal Maille, Bertrand Tamalet, Paul Fourcade, Eric Yiou
Summary: This study investigated the evolution of neuromotor control during a typical short sport-specific rehabilitation program (SSR) in professional soccer players who had incurred a major lower-limb injury (n = 15, chondral and muscle injuries, ACL-reconstruction). All injured participants (n = 15) were in the on-field rehabilitation phase of their specific sport rehabilitation process, prior to return to play. An experimental group (EG, chondral and muscle injuries, ACL-reconstruction) followed a 3-week SSR-program composed of muscular and core strengthening (weightlifting, functional stability, explosivity and mobility exercises), running and cycling, neuromotor reprogramming, cognitive development and specific soccer on-field rehabilitation (acceleration, braking, cutting, dual-contact, high-speed-running, sprint, jump, drills with ball). Neuromotor control via analysis of movement kinematics, muscle activation and kinetic parameters was evaluated using a single-leg Countermovement-Jump, pre- and post- rehabilitation program. A control group (n = 22) of healthy soccer players of similar standards performed the same single-leg Countermovement-Jump to provide reference values regarding the level to be attained by the injured players for return to play. In the experimental group, almost all kinetic analyses values progressed during the program and significantly for concentric Rate-of-Force-Development (p < 0.05), height jump (p < 0.001) and Reactive-Strength-Index Modified (p < 0.001) but remained lower than control group values for RSI-Mod (p < 0.05) and RFDconcentricLate (p < 0.001). Activation changed (p < 0.05) for all muscles except for rectus femoris and medial gastrocnemius in the pushing phase and rectus femoris during landing in the EG. Activation of all muscles decreased for EG, except for semitendinous which increased. Regarding kinematic analyses during the landing phase, there were a significant decrease in peak trunk flexion (p < 0.001) and lateroflexion (p < 0.001) and an increase in peak knee flexion (p < 0.001) for both legs. Trunk flexion (p < 0.001) and lateroflexion (p < 0.001) values were again higher for EG while knee flexion remained significantly lower than the CG (p < 0.001). The SSR generally improved neuromotor control suggesting that the present specific sport rehabilitation program, albeit of only three weeks duration, was effective in aiding elite footballers recover their neuromotor qualities although this was potentially insufficient to return to the values observed in healthy players.

6 Systematic video analysis of shoulder dislocations in professional male football (soccer): Injury mechanisms, situational and kinematic patterns

Reference: J Exp Orthop. 2024 Dec 19;11(4):e70121. doi: 10.1002/jeo2.70121. eCollection 2024 Oct.
Authors: Kristian Nikolaus Schneider, Tim Schachtrup, Georg Gosheger, Mirkka Lynn Hiort, Blanca Julie Degener, Theodoros Zafeiris, Christoph Theil
Download link: https://pmc.ncbi.nlm.nih.gov/articles/PMC11656221/pdf/JEO2-11-e70121.pdf
Summary: Shoulder dislocations in professional football are severe injuries with an increasing incidence and considerable layoff times. Unlike other football injuries, the mechanisms leading to shoulder dislocations are not well understood, which limits the development of targeted preventive measures. Thus, the aims of this study were: (1) to analyse injury mechanisms of shoulder dislocations in professional football, (2) to evaluate situational and (3) to assess kinematic patterns by performing a systematic video analysis. The study included all shoulder dislocations occurring in official matches within Germany’s top two professional male football (soccer) leagues (1. and 2. Bundesliga) from the 2012/2013 to the 2022/2023 seasons. A systematic video analysis was performed using the official Bundesliga video database. Two independent reviewers assessed injury-related, situational and kinematic parameters. A total of 37 shoulder dislocations in 36 players (mean age 25 years) were analysed. Two primary injury mechanisms were identified: Type 1 mechanisms, caused by direct contact to the upper extremity (n = 14), and Type 2 mechanisms, caused by catching a fall (n = 22). Only one case did not fit these categories. Median layoff times were 94 days for Type 1 and 56 days for Type 2, but this difference was not statistically significant. Statistically significant differences between the two types were found in player action (p < 0.001) and type of contact (p = 0.005), while factors like player’s speed, movement direction, football-specific actions, ball possession and pitch location showed no statistically significant differences. On-field treatment methods varied, but there were no statistically significant differences in repositioning attempts or reduction techniques (n.s.). Trunk position, shoulder joint version, shoulder elevation, and rotation, as well as elbow and wrist joint positions at the moment of dislocation, were similar between the two types (n.s.). Shoulder dislocations in professional football typically occur through direct contact or catching a fall, indicating a potential role for specific preventive measures.

7 Beyond the Pitch: Unveiling the Concave Hull as Soccer’s Ecological Niche in Practice Design

Reference: Res Q Exerc Sport. 2024 Dec 20:1-12. doi: 10.1080/02701367.2024.2434155. Online ahead of print.
Authors: Albert Deuker, Joris Wittkugel, Yannis Dublin, Bjoern Braunstein, Robert Rein, Keith Davids, Tobias Vogt
Summary: An ecological niche is a field in a landscape of affordances, rich in information inviting its inhabitants to develop functionality and effectiveness of their behavior. This idea means that, in sports like soccer, the playing area encapsulates an ecological niche, replete with affordances inviting collective and individual technical-tactical actions, contextualized with associated psychological and physical demands. To examine the co-adaptive relationships framing players‘ actions in their ecological niche, the present study employed a crossover design with repeated measures to compare the players‘ transactions within 11 vs. 11 training games across four different field dimensions (from official size to a small-sided game). Player transactions with the performance environment were analyzed across 40 game sequences, using 10Hz GPS positional data. Metrics such as convex hull dimensions, field occupancy, and proximity to opponents were derived. Repeated-measures ANOVA revealed significant differences between tendencies for forming synergies constrained by field dimensions scaling. When field size was reduced, the convex hull dimension significantly decreased. Additionally, relative field occupancy and distance to nearest opponent exhibited significant changes, especially when contrasted with performance transactions emerging on the official size field. These observations underline the essential functional relationship between the playing field dimension and emergent player actions. Such findings underscore the need for soccer coaches and training designers to integrate the specificity of field dimension scaling in training designs to represent competitive performance contexts. Data analytics deriving spatial constraint values from competitive matches may help researchers and practitioners improve task representativeness in practice and performance preparation, supporting the optimality of training niches in soccer.

8 External load transition practices from pre-season to in-season. A case study in elite female professional soccer players

Reference: PLoS One. 2024 Dec 20;19(12):e0314076. doi: 10.1371/journal.pone.0314076. eCollection 2024.
Authors: Rafael Oliveira, Ryland Morgans, Renato Fernandes, João Paulo Brito, Mário C Espada, Fernando J Santos
Download link: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0314076
Summary: The study aim was to compare the external load during varying microcycles (M1-M4 during pre-season and M5 during the in-season) in elite female Portuguese soccer players and to describe external load variations between differing Ms. Fourteen first-team players participated in the study (age 23.29 ± 3.19 years, weight 59.14 ± 6.87 kg, height 1.66 ± 0.08 m). Load measures included total distance, high-speed running (HSR) distance (≥15 km/h), number of accelerations and decelerations [acceleration 1 (ACC1), >1-2 m/s; acceleration 2 (ACC2), >2-3 m/s; acceleration 3 (ACC3), >3-4 m/s; acceleration 4 (ACC4), >4 m/s] and decelerations [deceleration 1 (DEC1), <1-2 m/s; deceleration 2 (DEC2), <2-3 m/s; deceleration 3 (DEC3), <3-4 m/s; deceleration 4 (DEC4), <4 m/s]. M1 showed higher values of total distance, ACC1, ACC2, ACC3, DEC2, DEC3 and DEC4 than M2 (p = <0.001-0.04), although HSR was higher in M2 (p < 0.001). M2 showed lower values of HSR, ACC1, DEC1, DEC2, DEC3 than M3 (p = 0.001-0.04). M3 reported higher values of total distance, ACC1, ACC2, DEC1, DEC2 than M4 (p = <0.001-0.03), while M4 only found higher values of ACC4 and DEC4 than M5 (both, p = 0.01). The highest values occurred in M3 for the majority of external load metrics (except ACC3, ACC4, and DEC4 which were higher in M4). However, during the transition from M4 to M5, only ACC4 and DEC4 decreased with all other measures maintained, thus supporting the notion to maintain similar loading patterns during official competition.

9 The impact of transient air pollution exposure on worker performance in Chinese soccer players

Reference: Sci Rep. 2024 Dec 28;14(1):31093. doi: 10.1038/s41598-024-82322-w.
Authors: Ning Zhang, Xiahai Wei, Xuhui Huang, Pan He, Yunxiao Liu, Hongyou Liu, Tao Lin, Xin Shi, Zhu Liu, Richard B Freeman
Download link: https://www.nature.com/articles/s41598-024-82322-w.pdf
Summary: Using a unique dataset on the performance of soccer players in China (retrieved from 632 matches involving 24 teams during the 2014 to 2016 seasons), we investigate the effect of air pollution on different performance indicators that rely on different mixtures of the physical and cognitive inputs of players. To ensure a causal interpretation, we implement an instrumental variable (IV) approach using thermal inversion as the instrument for air pollution. We found that players‘ performance indicators, especially those more related to cognitive factors, are more strongly influenced by air pollution. One standard deviation (SD) increase in the Air Quality Index (AQI) leads to 2.5% decrease in the number of players‘ passes and 5.1% increase in the number of fouls. However, for performance indicators that are more related to players‘ physical condition, e.g., running distances, no such significant impact is identified. Overall, these findings suggest that the negative impact of short-term air pollution exposure on outdoor worker performance is mainly cognitive, which we believe could lead to important policy implications, not only for competitive sports but also across a much broader spectrum of business sectors.

10 Effects of a Short-Term Soccer Training Intervention on Skill Course Performance in Youth Players: A Randomized Study

Reference: Sports (Basel). 2024 Dec 13;12(12):345. doi: 10.3390/sports12120345.
Authors: Arne Sørensen, Terje Dalen, Pål Lagestad
Download link: https://www.mdpi.com/2075-4663/12/12/345
Summary: The aim of this study was to evaluate the effect of 11 additional soccer training sessions among youth soccer players according to their performance in a skill course. A total of 90 participants, aged 9 to 12, were randomly assigned to either an intervention group (IG) (n = 54) or a control group (CG) (n = 36) and have validated data. The trainings focused upon enhancing ball mastery and decision-making and included a combination of one vs. one situations and small-sided games (SSGs). Pre- and post-tests measured passing and dribbling skills through a skill course. The best time with additional time penalties for each dribbling and passing error was used for further analysis. An independent t-test revealed no significant differences in improvement between the two groups. However, paired t-tests revealed significant improvements for both the IG and the CG from pre- to post-test (7.9 and 3.9 s, respectively). Furthermore, no significant differences in the development of track time, cone touches, or passing errors between the groups were detected. These findings suggest that soccer players aged 9 to 12 improve their performance in a skill course through increased familiarity with the course and natural development of technical skills based on participation in soccer training and recreational soccer play. We argue that the lack of significant differences between the groups‘ performances can be attributed to the short duration and few sessions of the intervention, and a somehow low similarity between the skill course and the activities in the sessions.

11 Youth Soccer Heading Exposure and Its Effects on Clinical Outcome Measures

Reference: Sports (Basel). 2024 Dec 10;12(12):342. doi: 10.3390/sports12120342.
Authors: Victoria E Wahlquist, Thomas A Buckley, Jaclyn B Caccese, Joseph J Glutting, Todd D Royer, Thomas W Kaminski
Download link: https://www.mdpi.com/2075-4663/12/12/342
Summary: Purposeful heading, in which players may use their heads to advance the ball in play, is a unique part of soccer. Clinical outcome measures used to aid in the diagnosis of a concussion have long been a cornerstone of the contemporary measurements associated with the short- and long-term effects of monitoring repetitive head impacts (RHI) and soccer heading exposure. The effects of RHI in the youth population are still unknown, therefore, the purpose of this study was to examine if heading exposure is predictive of changes in self-reported symptoms, neurocognitive functioning, gait, and balance in female youth soccer players over the course of one soccer season. Small improvements in neurocognitive functioning and gait and slight deficits in balance were observed from pre- to post-season. All changes were not clinically relevant and likely due to a practice effect. The low heading exposure in our cohort of youth soccer players was likely not enough to elicit any changes in clinical measures. In general, our clinical outcomes did not change after a season of soccer play and change scores were not predicted by heading exposure.

12 Temperature-Related Variations in Physical Performance During Elite Soccer Matches

Reference: Sports (Basel). 2024 Dec 7;12(12):341. doi: 10.3390/sports12120341.
Authors: Vladimir Pavlinovic, Ryland Morgans, Toni Modric
Download link: https://www.mdpi.com/2075-4663/12/12/341
Summary: The aim of this study was to examine the differences in match running performance (MRP) according to the ambient temperature during UEFA Champions League (UCL) matches. Data were collected using an optical tracking system from all teams (n = 32) in all UCL matches (n = 125) during the 2022/23 season, and classified according to the ambient temperature at which matches were played: <5 °C, 6-10 °C, 11-20 °C, and >21 °C. The results revealed the following: (i) less total distance was covered in matches played at ≥21 °C compared to the matches played at 6-10 °C (d = 0.58), (ii) less high-speed running and high-intensity running were covered in matches played at ≥21 °C compared to the matches played at 11-20 °C (d = 0.54 and 0.43, respectively), 6-10 °C (d = 0.89 and 0.8, respectively), and ≤5 °C (d = 0.62 and 0.57, respectively), and (iii) less sprinting was covered in matches played at ≥21 °C compared to the matches played at 6-10 °C (d = 0.22). These findings indicated the significant differences in MRP when UCL matches were played at different ambient temperatures, with notable reductions in overall and high-intensity efforts in warmer conditions.

13 Comparison of Vertical Jump Force-Time Metrics Between ACL-Injured and Healthy Semi-Professional Male and Female Soccer Players

Reference: Sports (Basel). 2024 Dec 6;12(12):339. doi: 10.3390/sports12120339.
Authors: Dimitrije Cabarkapa, Damjana V Cabarkapa, Andrew C Fry, Yu Song, Thordis Gisladottir, Milos Petrovic
Download link: https://www.mdpi.com/2075-4663/12/12/339
Summary: Given the increasing use of innovative force plate systems in applied sports settings and the impact that anterior cruciate ligament (ACL) injuries have on team success, the purpose of the present study was to compare the lower-body neuromuscular performance characteristics of athletes who underwent ACL reconstruction (ACLR) and their non-injured counterparts (i.e., healthy controls). Forty-five male (thirteen injured) and twenty-six female (ten injured) semi-professional soccer players volunteered to participate in the present study. Each athlete performed three countermovement vertical jumps (CMJs) while standing on a uniaxial force plate system sampling at 1000 Hz. The injured athletes completed a nine-month recovery protocol and were screened 11-13 months post-ACLR. The dependent variables included the force-time metrics within both the eccentric and concentric phases of the CMJ. Independent t-tests or Mann-Whitney U-test were used to examine statistically significant (p < 0.05) differences in each variable (i.e., ACL-injured vs. healthy controls). The results revealed no significant between-group differences in any CMJ force-time metrics of interest (e.g., concentric peak force, eccentric mean power, countermovement depth) between ACL-injured and non-injured athletes, including inter-limb asymmetry measures (i.e., peak takeoff and landing force). Besides implying the effectiveness of the implemented rehabilitation protocol, these findings suggest that the CMJ may not present a sufficient neuromuscular performance stimulus needed to expose lower-limb asymmetries and strength and power deficiencies 11-13 months post-ACLR.

14 Heading in Female Soccer: A Scoping Systematic Review

Reference: Sports (Basel). 2024 Nov 29;12(12):327. doi: 10.3390/sports12120327.
Authors: Yinhao Shen, Shinting Chen, Qingguang Liu, Antonio Cicchella
Download link: https://www.mdpi.com/2075-4663/12/12/327
Summary: Heading is a key skill in soccer, and it is few investigated in females. Research on heading focused mostly on males and on young players. Data on females‘ soccer players are sparse and it is difficult to draw firm conclusions. Thus, little is known is known about heading in females. The most investigated aspects of heading are the relationship between heading and play state, training level and anthropometrics. The relationship between the frequency and intensity of headings and long-time outcomes in terms of vigilance, and neuro-cognitive status is also a topic of interest. Aim of this scoping review is to survey the available knowledge about heading in female football to identify possible weaknesses and issues for future research direction in the field. A structured literature search was performed in the main databases. Results show research on heading in female soccer is sparse and to draw firm conclusion on the investigated aspects (effect of play position, occurrence, cognitive impairment, influence of muscle strength, and player’s level) is difficult. It emerged mild intensity heading is not dangerous, helmet does not help, play state and player position influences the heading and that high rotational velocities are achieved. The survey identified new directions for research, that should focus on how to ameliorate heading training and skills and develop a more effective and safe heading technique.

15 Characterization of the External Load of Soccer Goalkeepers Depending on the Category and Sports Context

Reference: Sports (Basel). 2024 Nov 26;12(12):318. doi: 10.3390/sports12120318.
Authors: Víctor Hernández-Beltrán, Boryi A Becerra-Patiño, Abian Perdomo-Alonso, Jesús Barguerias-Martínez, Sergio Gómez-Carrero, Mário C Espada, José M Gamonales
Download link: https://www.mdpi.com/2075-4663/12/12/318
Summary: Studies focused on the soccer goalkeeper position in training and official matches are scarce. The present study aimed to analyze the external load during training sessions and official matches in semi-professional goalkeepers. Data from goalkeepers (n = 6) from the youth ranks of a professional team belonging to the first Spanish soccer league have been used. The sample is made up of a total of 758 data collected during all the training and competitions carried out by the analyzed teams that made up the squad during the 2021/2022 and 2022/2023 seasons. A descriptive and inferential analysis was carried out based on the category (Youth B or Youth C) and the sports context (training or competition). The results showed significant differences depending on the category (average time to feet left, average time to feet right, total jumps, total dives, total left dives, total right dives, high metabolic load distance (HMLD), and high metabolic power efforts (HMPE)), and the sport context (average time to feet right, total jumps, total dives, total left dives, total right dives, total distance, distance 18-21 km/h, distance 21-24 km/h, Dec 2-3, efforts, and HMLD). The EL of the GKs shows differences regarding the category and the context. Therefore, it is necessary to analyze and determine the threshold of each player considering different variables related to the external and internal load to individualize the training tasks and prevent injuries due to overload.

16 Intra and Inter-Test Reliability of Isometric Hip Adduction Strength Test with Force Plates in Professional Soccer Players

Reference: J Funct Morphol Kinesiol. 2024 Dec 12;9(4):270. doi: 10.3390/jfmk9040270.
Authors: Jorge Pérez-Contreras, Juan Francisco Loro-Ferrer, Pablo Merino-Muñoz, Felipe Hermosilla-Palma, Brayan Miranda-Lorca, Alejandro Bustamante-Garrido, Felipe Inostroza-Ríos, Ciro José Brito, Esteban Aedo-Muñoz
Download link: https://www.mdpi.com/2411-5142/9/4/270
Summary: Assessing the reliability of measurement instruments and equipment is essential to ensure the accurate tracking of athletes over extended periods, minimizing the measurement errors caused by chance or other factors. However, a less common but equally important analysis is the verification of inter-measurement agreement, which complements the reliability results.  The aim was to evaluate the intra- and inter-test reliability of an isometric hip adduction strength and asymmetries test in professional soccer players. Twenty-three professional male soccer players were evaluated on two occasions, 1 week apart. The force signal was collected using force plates (Pasco PS-2141), and the data processing was performed using Matlab software (R2023a, MathWorks, Natick, MA, USA). The peak force, interval RFD, peak RFD, peak force asymmetry and RFD were analyzed. Intraclass correlation coefficients (ICCs) and coefficients of variation (CV) were calculated to corroborate the intra- and inter-test reliability. In addition, the degree of agreement of the asymmetries was corroborated through the kappa index. The peak force demonstrated an acceptable absolute reliability (CV < 10%) for the intra-test and test-retest condition, an excellent relative intra-test reliability and a good to moderate reliability for the test-retest reliability. However, the peak force asymmetry showed a moderate test-retest reliability and agreement. For the intra-test condition, the RFD variables demonstrate a moderate to excellent relative reliability; however, all demonstrate unacceptable absolute reliability (CV > 10%) in at least one of the evaluation sessions. A moderate to poor test-retest reliability and unacceptable absolute reliability were observed for all the RFD variables. The peak force is the variable with the highest intra- and inter-test reliability, so its use is recommended to longitudinally assess the maximum strength of the adductors in professional soccer players, but not the asymmetry orientation of the peak force. The RFD variables should be interpreted with caution due to their inconsistent reliability, and it is necessary to improve the methods used to achieve adequate reliability.

17 Football (soccer) match-derived hamstring muscles residual fatigue can be monitored using early rate of torque development

Reference: Eur J Appl Physiol. 2024 Dec 27. doi: 10.1007/s00421-024-05694-x. Online ahead of print.
Authors: Pedro L Cosio, Lia Moreno-Simonet, Daniel Fernández, Mario Lloret, Xavier Padulles, Josep M Padulles, Andreu Farran-Codina, Gil Rodas, Joan A Cadefau
Download link: https://link.springer.com/content/pdf/10.1007/s00421-024-05694-x.pdf
Summary: The aim of this study was to determine whether a soccer match affects the rapid force-generating capacity of the hamstring muscles, given their key role in both horizontal ground reaction force production during sprint biomechanics, and in the deceleration of the shank during the late swing phase, where rapid force production is essential owing to time constraints. Therefore, the research objective was to determine soccer match-induced hamstrings residual fatigue and recovery through rate of torque development (RTD) and associated biochemical parameters. The recovery kinetics of hamstrings RTD metrics by the 90°hip:20°knee test, together with serum biomarkers (creatine kinase, mitochondrial creatine kinase, transaminases, malondialdehyde, irisin), were assessed in 19 male, regional first-division soccer players (age = 20.9 ± 2.0 years, mass = 72.6 ± 11.9 kg, height = 175.9 ± 6.9 cm [mean ± SD]), before a soccer match (MD) and post-24 h (MD+1), post-48 h (MD+2) and post-72 h (MD+3), through a repeated measures design. Early RTD to 50 ms (p < 0.001, g = -1.24) and 100 ms (p < 0.001, g = -1.06) remained unrecovered on MD+3 in both hamstring muscles. However, maximal voluntary isometric contraction (MVIC) torque of the dominant and non-dominant hamstrings was unrecovered on MD+2 (p = 0.004, g = -0.91; and p = 0.002, g = -0.98, respectively) and recovered on MD+3 (p = 0.057 and p = 0.070, respectively). Further, neuromuscular deficits were coupled with myocyte structural (p = 0.002, g = 1.11) and mitochondrial damage (p = 0.004, g = 0.92) biomarkers. Based in the findings, early RTD0-50 and RTD0-100 monitoring, through the 90°hip:20°knee IPC test, is a cost-effective method for assessing soccer match-induced hamstring muscles residual fatigue and recovery. Overall, soccer match-induced hamstring residual fatigue is not recovered within a 3-day recovery period. Practitioners can use rapid force production metrics through isometric assessments, providing a simple, non-exhaustive tool, for assessing residual fatigue status during congested competitive periods, to comprehensively balance muscle recovery with optimizing training.

18 Cognition in elite soccer players: a general model

Reference: Front Psychol. 2024 Dec 11:15:1477262. doi: 10.3389/fpsyg.2024.1477262. eCollection 2024.
Authors: Thomas Habekost, Jacob Ovesen, Jes Buster Madsen
Download link: https://pmc.ncbi.nlm.nih.gov/articles/PMC11668572/pdf/fpsyg-15-1477262.pdf
Summary: This paper presents a general model of the cognitive processes involved in each play situation of soccer at the elite level. Theoretically the model draws on general frameworks from cognitive psychology and neuroscience, in particular the affordance competition hypothesis and the reward prediction error theory. The model includes three functional stages: situational assessment, action selection and execution, and outcome assessment. The three stages form a perception-action cycle that corresponds to a single play situation. The cognitive processes operating at each functional stage are described and related to soccer research by a review of 52 empirical studies. The review covers the main cognitive processes that have been studied in soccer research: visual orientation and attention, pattern recognition, anticipation, working memory, action selection and decision making, executive control processes, as well as behavioral and cognitive learning. The model accommodates the wide variety of findings in the empirical literature and provides a general organizing frame for cognitive soccer research at the elite level. The influence of emotional and stress-related factors on cognition are also discussed. Four general limitations of the existing soccer research are identified, and suggestions for future studies include development of more naturalistic and interventional study designs. By specifying the different cognitive processes in soccer and their dynamic interactions the model has many applied perspectives for soccer training at the professional level. Overall, the paper presents the first integrated process model of cognition in elite soccer players with implications for both research and practice.

19 Impact of lateral ankle sprains on physical function, range of motion, isometric strength and balance in professional soccer players

Reference: BMJ Open Sport Exerc Med. 2024 Dec 22;10(4):e002293. doi: 10.1136/bmjsem-2024-002293. eCollection 2024.
Authors: Bartosz Wilczyński, Paulina Cabaj, Maciej Biały, Katarzyna Zorena
Download link: https://pmc.ncbi.nlm.nih.gov/articles/PMC11667455/pdf/bmjsem-10-4.pdf
Summary: Lateral ankle sprains (LASs) are prevalent in soccer and can affect long-term performance, injury recurrence and risk for chronic ankle instability. This case-control study examined functional impairments associated with LAS in professional soccer players aged 17-21. 40 players were divided into 2 groups: 21 with a history of LAS and 19 healthy matched controls. Functional assessments included the Foot and Ankle Ability Measure (FAAM), Y Balance Test (YBT), Weight Bearing Lunge Test, Heel Rise Test, Side Hop Test, and ankle and hip isometric strength measurements. Soccer players with a history of LAS exhibited significant deficits in dynamic balance, particularly in the anterior and composite YBT scores, with moderate effect sizes (p<0.05). FAAM scores also revealed functional limitations in daily activities and sports performance for the LAS group. No significant differences were observed in strength or mobility measures, including the Heel Rise, Side Hop and isometric tests. There were also no differences between injured and non-injured legs in the LAS group in the performance tests. These findings highlight the persistent deficits in dynamic balance following LAS, emphasising the need for targeted rehabilitation to mitigate the risk of reinjury and enhance performance in soccer players.

20 Injury prevention in youth football (soccer): a comprehensive description of the development process of the ‚FUNBALL‘ programme

Reference: BMJ Open Sport Exerc Med. 2024 Dec 18;10(4):e002260. doi: 10.1136/bmjsem-2024-002260. eCollection 2024.
Authors: Rilind Obërtinca, Tim Meyer, Karen Aus der Fünten
Download link: https://pmc.ncbi.nlm.nih.gov/articles/PMC11667392/pdf/bmjsem-10-4.pdf
Summary: Many football injury prevention programmes (IPPs) have been developed to target various injuries and populations. There was no specific IPP for youth players in place before. However, several existing IPPs designed for adults were also assessed in the youth population. All the existing ones face the challenge of long-term adherence even though efficacy has been demonstrated for many weeks to seasons. The main barriers to a successful long-term implementation of IPPs are time constraints and the lack of attractiveness for the players as they do not contain football-specific and motivating exercises. Increasing its attractiveness was the main aspect of designing the programme. To achieve this, a new approach was used. The ‚FUNBALL‘ programme includes competitive, pair-based exercises and frequent ball use. It offers more flexibility as there is a choice between two different exercises for each category. It was developed through close collaboration between the research community, closely involved in real-life football, and the end-users. Tailoring IPPs to the preferences of end-users could mean a significant advancement on long-term adherence compared with previous programmes. However, further research is needed to assess this assumption.

21 The Influence of Caffeine on Tolerance to Sport-Specific High-Intensity Exercise in Young Elite Soccer Players

Reference: J Hum Nutr Diet. 2025 Feb;38(1):e70002. doi: 10.1111/jhn.70002.
Authors: Eduard Bezuglov, Timur Vakhidov, Georgiy Malyakin, Elizaveta Kapralova, Anton Emanov, Egana Koroleva, Marina Manina, Svetlana Erdes, Oleg Talibov
Summary: Modern elite football places extremely high demands on the athlete’s body, so it is of practical interest to study the effect of various dietary supplements on load tolerance and postexercise recovery. Furthermore, there is a lack of research on the effects of caffeine on key measures of load tolerance in football such as delayed-onset muscle soreness (DOMS), rate of perceived exertion (RPE) and heart rate (HR) at different time points after the exercise. 54 young players aged 15-17 years from a leading Russian football academy took part in a randomised trial using the balanced placebo design. They were divided into 4 groups: 1 – told caffeine/given caffeine, 2 – told caffeine/given placebo, 3 – told placebo/given placebo and 4 – told placebo/given caffeine. All participants consumed two capsules 60 min before testing, each containing 200 mg of caffeine or placebo. Sprinting, counter-movement jump, change of direction run, dribbling, T-test and the repeated sprint ability test were used to create conditions for high-intensity sports-specific load. A visual analogue scale was used to assess the severity of muscle soreness. RPE was assessed using the Borg Rating of Perceived Exertion scale. HR immediately postexercise (HRpe), HR after 2 min of passive rest (HRrest) and recovery HR (HRrec = HRpe – HRrest) were obtained. The data demonstrated that a single caffeine intake of 400 mg had no statistically significant effect on RPE (p = 0.948), HRpe (p = 0.698) or HRrec (p = 0.920) across the groups. Additionally, the severity of DOMS 24 h postexercise did not differ significantly between the groups (p = 0.077). Acute caffeine ingestion does not affect the subjective and objective indicators of training load in young football players aged 15-17 years with low levels of anxiety and low levels of daily caffeine intake.

22 The Effect of Intraset Rest Periods on External and Internal Load During Small-Sided Games in Soccer

Reference: Sports (Basel). 2024 Dec 2;12(12):331. doi: 10.3390/sports12120331.
Authors: Ioannis Ispirlidis, Dimitrios Pantazis, Athanasios Poulios, Alexandra Avloniti, Theodoros Stampoulis, Yiannis Michailidis, Konstantinos Troupkos, Evangelos Evangelou, Dimitrios Draganidis, Dimitrios Balampanos, Nikolaos-Orestis Retzepis, Maria Protopapa, Nikolaos Mantzouranis, Nikolaos Zaras, Maria Michalopoulou, Ioannis G Fatouros, Athanasios Chatzinikolaou
Download link: https://www.mdpi.com/2075-4663/12/12/331
Summary: The purpose of this study was to compare the internal and external load in continuous and intermittent small-sided games (SSG) formats. Eight semi-professional soccer players participated in the study, and they completed three protocols: (a) I-intermittent SSG protocol (Int-I, 4 sets of 4 min with a 3 min recovery); (b) Continuous SSG protocol (Con, 2 sets of 8 min with a 3 min recovery); (c) II-SSG protocol (Int-II, 4 sets of 4 min, where each set includes 1 min of exercise with varying recovery periods (10, 20, 30 s), with a 3 min recovery period between sets). A one-way analysis of variance (ANOVA) was used to analyze the dependent variables, with significance determined at p < 0.05. The three protocols differed in total distance covered and in distance covered at speeds >19 km/h, with the Int-II protocol resulting in the greatest distance covered (p < 0.05). Additionally, players in the Con protocol exercised at a higher percentage of their maximum heart rate (%HRmax) (p < 0.05), while the highest RPE value was observed in the Int-I interval protocol (p < 0.05). The external load experienced by players in intermittent SSG protocols is higher, while internal load (%HRmax) remains relatively low. This effect is especially notable in the new intermittent exercise model proposed in this study, which incorporates progressively increasing recovery times within each exercise set. Coaches can use this model to increase players‘ external load without causing a heightened perception of fatigue.