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Latest research in football - week 22 - 2022

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 Motion characteristics of under 15, under 17 and under 19 Italian youth women football (soccer) matches

Reference: J Sports Med Phys Fitness.  2022 Jun 10.  doi: 10.23736/S0022-4707.22.13923-X.

Authors: Enrico Mordillo, Matteo Zago

Summary: Despite the constant development of women's football, few studies to date addressed the physical requirements of youth female soccer players in regional (specific) contexts. This research characterized the activity profiles of élite Italian U15, U17 and U19 female games.  Sixty players (U15, n=18; U17, n=20; U19, n=22) from a high-level club in North-East Italy were involved. Players were equipped with a 10-Hz GPS device. Forty-six games were monitored (9 vs. 9 for U15, 11 vs. 11 for U17-U19) and the following dependent variables were extracted: total distance, equivalent distance, normalized distance (m/min) in six speed and metabolic power ranges. Total high-speed (>14.1 km/h) and total high-power (>18 W) distances were computed based on thresholds parametrized to the young female athlete. A multivariate General Linear Model was fit to analyze the effect of age category, match periods and their interaction. Some game parameters increased with age, especially from U15 to U17. Among them: total distance (5.5 km, 7.8 km, and 8.8 km for U15, U17, U19), distance at very-high (18-22 km/h) and maximum (>22 km/h) speed, distance at high power (18-31.5 W). Normalized distance was ~90 m/min and comparable among age groups. A reduction of very-high (31.5-49.5 W) and maximum power (>49.5 W) distance was observed in U15 matches, and of high-power distance in U17 and U19. These findings quantify the physical demands of Italian youth female match-play. These data support evidence-based training planning, set a reference for players approaching higher playing standards, and could back up informed redesign of playing formats.



#2 Efficacy of Electromyographic Biofeedback in Muscle Recovery after Meniscectomy in Soccer Players

Reference: Sensors (Basel). 2022 May 26;22(11):4024. doi: 10.3390/s22114024.

Authors: Verónica Morales-Sánchez, Coral Falcó, Antonio Hernández-Mendo, Rafael E Reigal

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Summary: Electromyographic biofeedback (EMG-BF) is a therapeutic technique that has been used successfully in the rehabilitation of injuries. Although it has been applied to athletes, its use in this field is not very widespread. The objective of this study is to analyze its effectiveness in the recovery of electromyographic activity of the quadriceps after meniscectomy, evaluated through isometric contraction of the vastus lateralis. The sample comprised ten professional footballers in the Spanish League (2nd Division A) who had previously suffered a meniscus injury in their knee and had undergone a meniscectomy. The intervention consisted of EMG-BF treatment lasting between 6 and 10 sessions. The electromyographic signal was recorded using a Thought Technology ProComp Infiniti 8-channel biofeedback unit with a sampling rate of 2048 samples/second. For each session, a within-subject ABA design of 6 or 10 trials per session was used, with three pre- and three post-measures, which determined the gain for each session. The results indicated (1) improvements in all cases, (2) EMG-BF was effective, (3) the working model was statistically significant with an explained variance of between 67% and 75%, and (4) the generalizability analysis showed that the results are reliable and generalizable. The results indicate that EMG-BF is effective in neuromuscular rehabilitation after this type of intervention.



#3 Investigating the Knuckleball Effect in Soccer Using a Smart Ball and Training Machine

Reference: Sensors (Basel). 2022 May 24;22(11):3984.  doi: 10.3390/s22113984.

Authors: David Eager, Karlos Ishac, Shilei Zhou, Imam Hossain

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Summary: The term knuckleball in sporting jargon is used to describe a ball that has been launched with minimal spin, resulting in a trajectory that is erratic and unpredictable. This phenomenon was first observed in baseball (where the term originated) and has since been observed in other sports. While knuckleball has long fascinated the scientific community, the bulk of research has primarily focused on knuckleball as it occurs in baseball. Following the changes in the design of the soccer ball after the 2006 World Cup, knuckleball and ball aerodynamics were exploited by soccer players. This research examined the properties of a knuckleball in the sport of soccer. We designed and evaluated a system that could reproduce the knuckleball effect on soccer balls based on previous theories and characteristics outlined in our literature review. Our system is comprised of the Adidas miCoach Smart Ball, a companion smart phone app for data collection, a ball-launching machine with programmable functions, and a video-based tracking system and Tracker motion analysis software. The results from the testing showed that our system was successfully able to produce knuckleball behaviour on the football in a highly consistent manner. This verified the dynamic models of knuckleball that we outline. While a small portion of the data showed some lateral deviations (zig-zag trajectory), this erratic and unpredictable trajectory was much smaller in magnitude when compared to examples seen in professional games. The sensor data from the miCoach app and trajectory data from the Tracker motion analysis software, showed that the knuckleballs were consistently reproduced in-line with theoretical dynamics.



#4 Consequences of the SARS-CoV-2 Infection on Anaerobic Performances in Young Elite Soccer Players

Reference: Int J Environ Res Public Health. 2022 May 25;19(11):6418. doi: 10.3390/ijerph19116418.

Authors: Marc Dauty, Jérôme Grondin, Pauline Daley, Bastien Louguet, Pierre Menu, Alban Fouasson-Chailloux

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Summary: The COVID-19 pandemic required local confinement measures reducing sport practice with possible consequences on the athletes' performances. Furthermore, anaerobic detraining was underestimated and poorly known in adolescents. This article aimed to assess the effects of SARS-CoV-2 infection and 1-month COVID-19 confinement on jump testing in young elite soccer players despite a 1-month multimodal training program followed by a 1-month soccer retraining period. Thirty-one elite soccer players aged 14 were included; 16 were infected by the SARS-CoV-2 and compared with 15 non-infected elite soccer players before and after 1 month of COVID-19 confinement, and after 1 month of a soccer retraining period. Squat jumps (SJ), countermovement jumps with (CMJs) and without arm swinging (CMJ) and multiple consecutive jumps (stiffness) were used to explore the anaerobic performances. Analysis of variance for repeated measures was used to compare the positive and negative SARS-CoV-2 groups, taking into account the confinement period (low training) and the retraining soccer period. The jump tests were not altered in the positive SARS-CoV-2 group compared to the negative SARS-CoV-2 group after confinement (SJ: 31.6 ± 5.6 vs. 32.7 ± 3.7; CMJ: 34.1 ± 6.9 vs. 34.2 ± 2.6; CMJs: 38.6 ± 6.8 vs. 40.3 ± 3.9; stiffness: 28.5 ± 4.3 vs. 29.1 ± 3.7) and at 1 month of this period (SJ: 33.8 ± 5.5 vs. 36.2 ± 4.6; CMJ: 34.7 ± 5.5 vs. 36.4 ± 3.5; CMJs: 40.4 ± 6.7 vs. 42.7 ± 5.5; stiffness: 32.6 ± 4.7 vs. 34.0 ± 4.3). The SARS-CoV-2 infection had no consequence on anaerobic performances assessed by jump tests in adolescent soccer players. The adolescents' growth could explain the absence of alteration of jump performances during the COVID-19 confinement. These results can be useful to manage the recovery of the anaerobic fitness after SARS-CoV-2 infection occurring in adolescent athletes.



#5 Visual tracking assessment in a soccer-specific virtual environment: A web-based study

Reference: PLoS One. 2022 Jun 9;17(6):e0269643. doi: 10.1371/journal.pone.0269643. eCollection 2022.

Authors: Alexandre Vu, Anthony Sorel, Charles Faure, Antoine Aurousseau, Benoit Bideau, Richard Kulpa

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Summary: The ability to track teammates and opponents is an essential quality to achieve a high level of performance in soccer. The visual tracking ability is usually assessed in the laboratory with non-sport specific scenarios, leading in two major concerns. First, the methods used probably only partially reflects the actual ability to track players on the field. Second, it is unclear whether the situational features manipulated to stimulate visual tracking ability match those that make it difficult to track real players. In this study, participants had to track multiple players on a virtual soccer field. The virtual players moved according to either real or pseudo-random trajectories. The experiment was conducted online using a web application. Regarding the first concern, the visual tracking performance of players in soccer, other team sports, and non-team sports was compared to see if differences between groups varied with the use of soccer-specific or pseudo-random movements. Contrary to our assumption, the ANOVA did not reveal a greater tracking performance difference between soccer players and the two other groups when facing stimuli featuring movements from actual soccer games compared to stimuli featuring pseudo-random ones. Directing virtual players with real-world trajectories did not appear to be sufficient to allow soccer players to use soccer-specific knowledge in their visual tracking activity. Regarding the second concern, an original exploratory analysis based on Hierarchical Clustering on Principal Components was conducted to compare the situational features associated with hard-to-track virtual players in soccer-specific or pseudo-random movements. It revealed differences in the situational feature sets associated with hard-to-track players based on movement type. Essentially with soccer-specific movements, how the virtual players were distributed in space appeared to have a significant influence on visual tracking performance. These results highlight the need to consider real-world scenarios to understand what makes tracking multiple players difficult.



#6 Multiple Players Tracking in Virtual Reality: Influence of Soccer Specific Trajectories and Relationship With Gaze Activity

Reference: Front Psychol. 2022 May 20;13:901438. doi: 10.3389/fpsyg.2022.901438. eCollection 2022.

Authors: Alexandre Vu, Anthony Sorel, Annabelle Limballe, Benoit Bideau, Richard Kulpa

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Summary: The perceptual-cognitive ability to track multiple moving objects and its contribution to team sports performance has traditionally been studied in the laboratory under non-sports specific conditions. It is thus questionable whether the measured visual tracking performance and the underlying gaze activity reflected the actual ability of team sports players to track teammates and opponents on a real field. Using a Virtual Reality-based visual tracking task, the ability of participants to track multiple moving virtual players as they would do on a soccer field was observed to pursue two objectives. (i) See the influence of different scenario types (soccer-specific trajectories versus pseudo-random trajectories) on the visual tracking performance of soccer (n = 15) compared to non-soccer players (n = 16). (ii) Observe the influence of spatial features of the simulated situations on gaze activity between soccer players and non-soccer players. (i) The linear mixed model regression revealed a significant main effect of the group but no interaction effect between group and the type of trajectories, suggesting that the visual tracking ability of soccer players did not benefit from their specific knowledge when they faced scenarios with real game trajectories. (ii) Virtual players' spatial dispersion and crowding affected the participants' gaze activity and their visual tracking performance. Furthermore, the gaze activity of soccer players differed in some aspects from the gaze activity of non-soccer players. Assumptions are formulated as to the implication of these results in the difference in visual tracking performance between soccer players and non-soccer players. Overall, using soccer-specific trajectories might not be enough to replicate the representativeness of the field conditions in the study of visual tracking performance. Multitasking constraints should be considered along with motor-cognitive dual-tasks in future research to develop the representativeness of visual exploration conditions.



#7 The incidence and severity of COVID-19 in adult professional soccer players in Russia

Reference: PLoS One. 2022 Jun 6;17(6):e0265019. doi: 10.1371/journal.pone.0265019. eCollection 2022.

Authors: Eduard Bezuglov, Vladimir Khaitin, Artemii Lazarev, Evgeniy Achkasov, Larisa Romanova, Mikhail Butovskiy, Vladimir Khokhlov, Maxim Tsyplenko, Alexander Linskiy, Petr Chetverikov, Magomedtagir Sugaipov, Arseniy Petrov, Oleg Talibov, Zbigniew Waśkiewicz

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Summary: There are little data on the incidence, and clinical course of COVID-19 among professional soccer players, and the studies examining putative complications of COVID-19 infections are probabilistic. On February 28, the WHO raised the COVID-19 threat assessment to its highest level. The COVID-19 outbreak became a significant challenge for world health. Around 30 million people got infected with COVID-19 since the beginning of this year. More than 900.000 decease. Thus, examining the incidence of COVID-19 and various aspects of its clinical course in a group of adult professional soccer players would be of great practical interest. The incidence, clinical practice, and severity of COVID-19 infection, as well as the duration of treatment and return to play was studied based on a survey of team physicians and medical records assessment in the group of adult professional soccer players representing the clubs of the Russian Premier-League (RPL) during the period of championship resumption from 01.04.2020 until 20.09.2020. COVID-19 infection was detected in 103 soccer players during COVID-19 screening. This number comprises 14.5% of all soccer players on the rosters of RPL soccer teams and is subjected to regular COVID-19 testing. The asymptomatic course was observed in 43.7% of cases (n = 45). These players were isolated, and their clinical condition was monitored closely. In 56.3% of patients (n = 58), fatigue, headache, fever, and anosmia were the most common symptoms. COVID-19 infection was commonly diagnosed among adult professional soccer players in Russia. However, most cases had a mild course and did not impair return to regular exercise. Only two players were hospitalized with lung lesions and returned to regular sports.



#8 Players at home: Physical activity and quality of life in 12-17 years-old football (soccer) players during the Covid-19 lockdown

Reference: Int J Sports Sci Coach. 2022 Jun;17(3):626-636. doi: 10.1177/17479541211041703.

Authors: Matteo Zago, Nicola Lovecchio, Manuela Galli

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Summary: Aggressive preventive actions were required to face the Covid-19 outbreak. However, from March 2020 on, many healthy youth football players have seen their sporting activities disrupted by the restrictions on outdoor exercise.This study describes physical activity and quality of life during April 2020 lockdown of young people participating in organized football. 1163 young football players aged 12-17 years (185 girls) completed a web-based questionnaire including the Youth Physical Activity and the Youth Quality of Life-Short Form Questionnaires; information on lifestyle and football-specific activity were also collected. Differences according to sex, urban/rural context and élite/non-élite club level were tested using a 2 ×× 2 ×× 2 MANOVA (age considered as a covariate). We found that: (i) on average, exposure to football accounted for 3.2 hours/week, was higher in élite clubs and changed in nature, being mainly performed individually; 19% of participants practiced football <1 hour/week; (ii) only 56% of the participants reported 7 or more hours/week of moderate-to-vigorous physical activity, which decreased with age and changed according to the geographical context; (iii) perceived quality of life was lower in youth playing for non-elite clubs and in older girls; (iv) coaches, rather that official initiatives, were the primary source of football exercises practiced at home. A status of limited physical activity emerged; this might lead to deconditioning and susceptibility to injuries when football could restart. Governing bodies, football Associations and clubs could exploit these results to take informed decisions and support evidence-based interventions during and after the Covid-19 pandemic.



#9 Automated soccer head impact exposure tracking using video and deep learning

Reference: Sci Rep. 2022 Jun 3;12(1):9282. doi: 10.1038/s41598-022-13220-2.

Authors: Ahmad Rezaei, Lyndia C Wu

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Summary: Head impacts are highly prevalent in sports and there is a pressing need to investigate the potential link between head impact exposure and brain injury risk. Wearable impact sensors and manual video analysis have been utilized to collect impact exposure data. However, wearable sensors suffer from high deployment cost and limited accuracy, while manual video analysis is a long and resource-intensive task. Here we develop and apply DeepImpact, a computer vision algorithm to automatically detect soccer headers using soccer game videos. Our data-driven pipeline uses two deep learning networks including an object detection algorithm and temporal shift module to extract visual and temporal features of video segments and classify the segments as header or nonheader events. The networks were trained and validated using a large-scale professional-level soccer video dataset, with labeled ground truth header events. The algorithm achieved 95.3% sensitivity and 96.0% precision in cross-validation, and 92.9% sensitivity and 21.1% precision in an independent test that included videos of five professional soccer games. Video segments identified as headers in the test data set correspond to 3.5 min of total film time, which can be reviewed through additional manual video verification to eliminate false positives. DeepImpact streamlines the process of manual video analysis and can help to collect large-scale soccer head impact exposure datasets for brain injury research. The fully video-based solution is a low-cost alternative for head impact exposure monitoring and may also be expanded to other sports in future work.



#10 Fatigue and Recovery Time Course After Female Soccer Matches: A Systematic Review And Meta-analysis

Reference: Sports Med Open. 2022 Jun 3;8(1):72. doi: 10.1186/s40798-022-00466-3.

Authors: Karine Naves Oliveira Goulart, Cândido Celso Coimbra, Helton Oliveira Campos, Lucas Rios Drummond, Pedro Henrique Madureira Ogando, Georgia Brown, Bruno Pena Couto, Rob Duffield, Samuel Penna Wanner

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Summary: This study aimed to analyze the extent of fatigue responses after female soccer matches and the ensuing recovery time course of performance, physiological, and perceptual responses. Three databases (PubMed, Web of Science, and SPORTDiscus) were searched in October 2020 and updated in November 2021. Studies were included when participants were female soccer players, regardless of their ability level. Further, the intervention was an official soccer match with performance, physiological, or perceptual parameters collected pre- and post-match (immediately, 12 h, 24 h, 48 h, or 72 h-post). A total of 26 studies (n = 465 players) were included for meta-analysis. Most performance parameters showed some immediate post-match reduction (effect size [ES] = - 0.72 to - 1.80), apart from countermovement jump (CMJ; ES = - 0.04). Reduced CMJ performance occurred at 12 h (ES = - 0.38) and 24 h (ES = - 0.42) and sprint at 48 h post-match (ES = - 0.75). Inflammatory and immunological parameters responded acutely with moderate-to-large increases (ES = 0.58-2.75) immediately post-match. Creatine kinase and lactate dehydrogenase alterations persisted at 72 h post-match (ES = 3.79 and 7.46, respectively). Small-to-moderate effects were observed for increased cortisol (ES = 0.75) and reduced testosterone/cortisol ratio (ES = -0.47) immediately post-match, while negligible to small effects existed for testosterone (ES = 0.14) and estradiol (ES = 0.34). Large effects were observed for perceptual variables, with increased fatigue (ES = 1.79) and reduced vigor (ES = - 0.97) at 12 h post-match, while muscle soreness was increased immediately post (ES = 1.63) and at 24 h post-match (ES = 1.00). Acute fatigue exists following female soccer matches, and the performance, physiological, and perceptual parameters showed distinctive recovery timelines. Importantly, physical performance was recovered at 72 h post-match, whereas muscle damage markers were still increased at this time point. These timelines should be considered when planning training and match schedules. However, some caution should be advised given the small number of studies available on this population.



#11 Influence of the Covid 19 pandemic on changes in aerobic fitness and injury incidence in elite male soccer players

Reference: J Sports Med Phys Fitness. 2022 Jun 10. doi: 10.23736/S0022-4707.22.13929-0. Online ahead of print.

Authors: Viswanath B Unnithan, Barry Drust, Colin Brow, Andisheh Bakhshi, Liam Mason, Matthew Weston

Summary: The SARS-COV2 agent initiated a global pandemic. The initial response to the pandemic was severe disruption to the public and private sector including sports. The resultant was that soccer clubs had to prescribe that the players trained in isolation for a prolonged period of time in an attempt to maintain fitness. The aim of the present study was to evaluate the impact of a 10-week period of training in isolation on aerobic fitness, body composition and injury incidence on the return to pre-season team-training in a group of elite, male soccer players. Twenty-two professional soccer players (age: 25.2 ± 4.4 years) who played for an English Championship first team participated in this study. A weekly training programme was sent to each player at the start of each week. Prior to the start of the isolated training period, all players underwent a maximal aerobic speed test (MAS) and body mass index data (BMI) were obtained. These measurements were repeated on the return to team training. There was a significant (p<0.05) increase in MAS pre-post isolated training (Pre: 4.71 ± 0.15 vs Post: 4.92 ± 0.17 m/s), no change in BMI (Pre: 24.3 ± 1.3 vs Post: 24.1 ± 1.1 kg/m2) and a low non-contact, soft tissue muscle incidence on the return to team training. The evidence from this study suggests that a more prolonged preseason schedule can enhance aerobic conditioning and mitigate the injury risk on the return to competitive match-play in elite soccer players.



#12 Football fans' emotional attachment to their clubs as a predictor of weight loss in a prevention programme for men with obesity

Reference: Clin Obes. 2022 Jun 10;e12540. doi: 10.1111/cob.12540.

Authors: Benjamin Pietsch, Reiner Hanewinkel, Matthis Morgenstern

Summary: Data about which factors in lifestyle interventions facilitate weight loss (WL) success in men is still scarce. The Football Fans in Training (FFIT) programme in Germany attracts men with overweight and facilitates meaningful weight reduction. The goal of this study was to evaluate the possible impact of the fans' emotional attachment to their favourite football clubs on achieving at least 5% WL among the male-only participants. All 791 FFIT intervention participants of 2017 and 2018 were included in the study. We performed two separate logistic regression analyses: (a) baseline values of several participant characteristics as predictors of a 5% WL and (b) change scores of participants' health behaviour characteristics from the course start to end as predictors of the 5% WL. In addition, both models included the Emotional Attachment to a Sports Team (EAST). Analyses were based on the intention-to-treat principle. Higher EAST at baseline was associated with WL success, as was higher WL self-efficacy, lower score in vegetable intake and higher score in food high on carbohydrates. In the second analysis, EAST, an increase in fruit intake, vegetable intake, whole-grain intake and steps per day, as well as a reduction of fatty food intake, were associated with 5% WL success. The predictors are mostly explorative and limited to correlations. The results indicate that EAST was an independent predictor of WL success in the participating football fans. This understanding might be used for tailoring future interventions in sports or similar settings.



#13 Association between Selected Screening Tests and Knee Alignment in Single-Leg Tasks among Young Football Players

Reference: Int J Environ Res Public Health. 2022 May 31;19(11):6719. doi: 10.3390/ijerph19116719.

Authors: Bartosz Wilczyński, Łukasz Radzimiński, Agnieszka Sobierajska-Rek, Katarzyna Zorena

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Summary: This study aimed to examine the relationship between knee valgus in the frontal plane projection angle (FPPA) during single-leg squat (SLS), single-leg landing (SLL), and other selected clinical tests in young athletes. Forty-three young healthy elite football players (age: 13.2 (1.7) years) that were regularly training in a local sports club participated in the study. The FPPA was assessed using 2D video analysis. The screening tests included the passive single-leg raise (PSLR), hip external and internal rotation (hip ER and IR), sit and reach test, weight-bearing lunge test (WBLT), modified star excursion balance test (mSEBT), countermovement jump (CMJ), single-leg hop for distance (SLHD), and age peak height velocity (APHV). There was a significant positive relationship between the knee valgus angles in the SLS test and the sit and reach test (r = 0.34) and a negative relationship with the hip ER ROM (r = -0.34) (p &lt; 0.05). The knee valgus angles in the SLL were negatively associated with the hip IR (r = -0.32) and ER ROM (r = -0.34) and positive associated with the WBLT (r = 0.35) and sit and reach test (r = 0.33) (p &lt; 0.05). Linear regression analysis showed that the results of the hip ER ROM and sit and reach tests were independent predictors of the FPPA in the SLS test (r2 = 0.11, p = 0.03 and r2 = 0.12, p = 0.02, respectively). The conducted study showed that individuals with more hip range of motion, more spine flexion extensibility, and less ankle dorsiflexion ROM may be more likely to experience high degrees of knee valgus in FPPA.



#14 Evaluation of an Experience of Academic Happiness through Football at University

Reference: Int J Environ Res Public Health. 2022 May 28;19(11):6608. doi: 10.3390/ijerph19116608.

Authors: David Almorza-Gomar, Rafael Ravina-Ripoll, Cristina Raluca Gh Popescu, Araceli Galiano-Coronil

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Summary: The main objective of the university sport in Spain is the comprehensive training of the students. It sets out in the various state regulations in this respect. There is training in values within the comprehensive training that sporting activity should provide through Fair Play. This article aims to describe and evaluate an experience of training in values for the university students carried out by the Sports Department of the University of Cadiz, located in Cádiz, Andalusia, Spain. The methodology consisted of making selected changes to the game rules in football competitions. The experience has lasted ten years. The result of the experience has been very positive, obtaining, among other substantial achievements, a reduction of more than 75% in the percentage of cards (yellow and red) shown during matches and a reduction in referee cautions, a decrease in violent behavior, self-exclusion of players with violent behavior by the teams themselves, and an increase in fair play sporting behavior. Due to this experience, the Sports Department of the University of Cadiz has received numerous national and international awards. However, the leading award has been to take part positively, through sport, in the education and happiness of its students.



#15 Observation on the Effect of MRI Image Scanning on Knee Pain in Football Injury

Reference: Scanning. 2022 May 25;2022:7348978. doi: 10.1155/2022/7348978. eCollection 2022.

Author: Weidong Yu

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Summary: The aim was to study the effect of football injury on knee pain based on MRI image scanning, in this paper, a total of 31 knee injuries of 29 male professional football players from December 2012 to April 2015 were used as the experimental group. The players were 23.6 ± 3.5 years old and received professional football training time 15.3 ± 3.6 years; 31 outpatients of the same age group with acute knee joint acute injury were randomly selected as the control group; both groups were imaged with a 1.5 TMR scanner and knee joint standard array coil imaging, and 2 senior radiation surgeons evaluate knee cartilage, meniscus, ligaments, tendons, bone marrow, infrapatellar fat pad, and joint effusions. Pearson's chi-squared test and nonparametric test for two independent samples were used for statistical testing of the evaluation results. The experimental results showed that there were significant differences in the incidence of articular cartilage, lateral collateral ligament, tendon or ligament injury, multiligament or tendon injury, and bone marrow edema between the two groups (P < 0.05). There was no significant difference in the incidence of medial collateral ligament injury, infrapatellar fat pad edema, and joint effusion. MRI shows that knee injuries in male professional football players often involve ligaments or tendons, mostly multiligament or tendon injuries. The lesions of articular cartilage and meniscus are more common and serious, and bone marrow edema is also more common in football injuries. MRI has high diagnostic accuracy for various clinical knee injuries, and it belongs to a noninvasive examination method. It can not only reflect the pathological changes and changes of the knee joints of patients but also provide information for the formulation of clinical programs and the judgment of prognosis, for timely, accurate, and comprehensive imaging reference.



#16 Machine Learning for Understanding and Predicting Injuries in Football

Reference: Sports Med Open. 2022 Jun 7;8(1):73. doi: 10.1186/s40798-022-00465-4.

Authors: Aritra Majumdar, Rashid Bakirov, Dan Hodges, Suzanne Scott, Tim Rees

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Summary: Attempts to better understand the relationship between training and competition load and injury in football are essential for helping to understand adaptation to training programmes, assessing fatigue and recovery, and minimising the risk of injury and illness. To this end, technological advancements have enabled the collection of multiple points of data for use in analysis and injury prediction. The full breadth of available data has, however, only recently begun to be explored using suitable statistical methods. Advances in automatic and interactive data analysis with the help of machine learning are now being used to better establish the intricacies of the player load and injury relationship. In this article, we examine this recent research, describing the analyses and algorithms used, reporting the key findings, and comparing model fit. To date, the vast array of variables used in analysis as proxy indicators of player load, alongside differences in approach to key aspects of data treatment-such as response to data imbalance, model fitting, and a lack of multi-season data-limit a systematic evaluation of findings and the drawing of a unified conclusion. If, however, the limitations of current studies can be addressed, machine learning has much to offer the field and could in future provide solutions to the training load and injury paradox through enhanced and systematic analysis of athlete data.



#17 Social and Cultural Constraints on Football Player Development in Stockholm: Influencing Skill, Learning, and Wellbeing

Reference: Front Sports Act Living. 2022 May 20;4:832111. doi: 10.3389/fspor.2022.832111. eCollection 2022.

Authors: James Vaughan, Clifford J Mallett, Paul Potrac, Carl Woods, Mark O'Sullivan, Keith Davids

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Summary: In this paper, we consider how youth sport and (talent) development environments have adapted to, and are constrained by, social and cultural forces. Empirical evidence from an 18-month ethnographic case study highlights how social and cultural constraints influence the skill development and psychological wellbeing of young football players. We utilized novel ways of knowing (i.e., epistemologies) coupled to ecological frameworks (e.g., the theory of ecological dynamics and the skilled intentionality framework). A transdisciplinary inquiry was used to demonstrate that the values which athletes embody in sports are constrained by the character of the social institutions (sport club, governing body) and the social order (culture) in which they live. The constraining character of an athlete (talent) development environment is captured using ethnographic methods that illuminate a sociocultural value-directedness toward individual competition. The discussion highlights how an emphasis on individual competition overshadows opportunities (e.g., shared, and nested affordances) for collective collaboration in football. Conceptually, we argue that these findings characterize how a dominating sociocultural constraint may negatively influence the skill development, in game performance, and psychological wellbeing (via performance anxiety) of young football players in Stockholm. Viewing cultures and performance environments as embedded complex adaptive systems, with human development as ecological, it becomes clear that microenvironments and embedded relations underpinning athlete development in high performance sports organizations are deeply susceptible to broad cultural trends toward neoliberalism and competitive individualism. Weaving transdisciplinary lines of inquiry, it is clarified how a value directedness toward individual competition may overshadow collective collaboration, not only amplifying socio-cognitive related issues (anxiety, depression, emotional disturbances) but simultaneously limiting perceptual learning, skill development, team coordination and performance at all levels in a sport organization.



#18 Genetic associations with technical capabilities in English academy football players: a preliminary study

Reference: J Sports Med Phys Fitness. 2022 Jun 6. doi: 10.23736/S0022-4707.22.13945-9. Online ahead of print.

Authors: Alexander B McAULEY, David C Hughes, Loukia G Tsaprouni, Ian Varley, Bruce Suraci, Joseph Baker, Adam J Herbert, Adam L Kelly

Summary: Technical capabilities have significant discriminative and prognostic power in youth football. Although, many factors influence technical performance, no research has explored the genetic contribution. As such, the purpose of this study was to examine the association of several single nucleotide polymorphisms (SNPs) with technical assessments in youth football players. Fifty-three male under-13 to under-18 outfield football players from two Category 3 English academies were genotyped for eight SNPs. Objective and subjective technical performance scores in dribbling, passing, and shooting were collated. Simple linear regression was used to analyse individual SNP associations each variable, whereas both unweighted and weighted total genotype scores (TGSs; TWGSs) were computed to measure the combined influence of all SNPs. In isolation, the ADBR2 (rs1042714) C allele, BDNF (rs6265) C/C genotype, DBH (rs1611115) C/C genotype, and DRD1 (rs4532) C allele were associated with superior (8-10%) objective dribbling and/or shooting performance. The TGSs and/or TWGSs were significantly correlated with each technical assessment (except subjective passing), explaining up to 36% and 40% of the variance in the objective and subjective assessments, respectively. The results of this study suggest inter-individual genetic variation may influence the technical capabilities of youth football players and proposes several candidate SNPs that warrant further investigation.



#19 A Study on the Optimization and Improvement of the Construction of the Campus Football Development Model by a Factor Analysis Method under the Background of "Healthy China"

Reference: J Environ Public Health. 2022 May 26;2022:3260571. doi: 10.1155/2022/3260571. eCollection 2022.

Authors: Zhen Wang, Bin Tan, Binquan Yi

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Summary: In order to enrich campus sport life and promote the development of campus ball game, this paper uses the analysis method to analyze the development mode of campus football and evaluates the relevant factors combined with the development status, characteristics, and future trend of campus football. Factor analysis is a comprehensive analysis method, which can realize multifactor comprehensive analysis and qualitative and quantitative analysis of campus football. At the same time, analyze the relationship between various factors and find a scheme conducive to the development of campus football. The results show that both comprehensive method factors and single method factors are positive, indicating that the two models have a significant positive impact on the development model of students' football. However, the influence degree of the comprehensive method (0.314) is the largest, followed by the single method factor (0.128), and the sig. values of the two variable factors are <0.05, so the comprehensive method is the main mode of campus football development. Therefore, the factor analysis method proposed in this paper is conducive to the selection of campus football development model and provides support for the development of campus football.



#20 COVID-19 Diffusion Before Awareness: The Role of Football Match Attendance in Italy

Reference: J Sports Econom. 2022 Jun;23(5):503-523. doi: 10.1177/15270025211067786.

Authors: Vincenzo Alfano

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Summary: Anecdotal evidence suggests that football matches may have played a role in the spread of COVID-19 all over Europe. Nevertheless, from a scientific point of view, the impact of football matches on the spread of COVID-19 remains unclear. In this paper we study, via a quantitative analysis, the case of Italy, a country badly affected by COVID, and one where attending football matches is very popular. We consider the impact of matches played in January and February 2020 on the dynamic of the pandemic in March and April the same year. Our results, which consider all levels of Italian professional football, and the highest level of amateur football, show that matches played in January and February had an impact on the evolution of the pandemic in March and April. These results suggest that great care must be taken before considering re-opening stadia.



#21 Prognostic factors of muscle injury in elite football players: A media-based, retrospective 5-year analysis

Reference: Phys Ther Sport. 2022 May 27;55:305-308. doi: 10.1016/j.ptsp.2022.05.009. Online ahead of print.

Authors: Jan Wilke, Sarah Tenberg, David Groneberg

Summary: Motor function has been demonstrated to be weakly predictive for the occurrence of muscle injury in team sports. This study examined the value of non-motor prognostic factors in elite football (soccer). 1148 players of 38 German and English first-division football clubs. Binary logistic regression examining the association of prognostic factors (age, height, weight, BMI, playing position, market value, history of injury, number of played matches and minutes) and time-loss muscle injuries sustained during five consecutive seasons (2014/2015 to 2018/2019). A total of 1722 muscle injuries were observed in 619 players. History of general musculoskeletal injury (OR 5.3, 95% CI 3.8-7.5), playing position (OR 2.4-2.5), market value (OR 2.3, 95% CI 1.7-3.1), and history of muscle injury (OR 1.6, 95% CI 1.1-2.2) were associated with muscle injury. Sub-analyses revealed location-specific patterns. Playing position was not predictive for adductor injury and, except for one weak association (defender vs. goalkeeper: OR 1.05, 95%CI 0.42-2.62), the same applied to the calf. Contrary to other locations, thigh re-injury was not predicted by previous muscle injury. Non-motor factors display significant associations with injury risk in elite football players. Conditioning coaches may use this information to improve primary and secondary prevention, while scouting departments may benefit during recruitment.



#22 Differential Ratings of Perceived Exertion: Relationships With External Intensity and Load in Elite Men's Football

Reference: Int J Sports Physiol Perform. 2022 Jun 3;1-10. doi: 10.1123/ijspp.2021-0550. Online ahead of print.

Authors: Kobe C Houtmeyers, Pieter Robberechts, Arne Jaspers, Shaun J McLaren, Michel S Brink, Jos Vanrenterghem, Jesse J Davis, Werner F Helsen

Summary: The aim was to examine the utility of differential ratings of perceived exertion (dRPE) for monitoring internal intensity and load in association football. Data were collected from 2 elite senior male football teams during 1 season (N = 55). External intensity and load data (duration × intensity) were collected during each training and match session using electronic performance and tracking systems. After each session, players rated their perceived breathlessness and leg-muscle exertion. Descriptive statistics were calculated to quantify how often players rated the 2 types of rating of perceived exertion differently (dRPEDIFF). In addition, the association between dRPEDIFF and external intensity and load was examined. First, the associations between single external variables and dRPEDIFF were analyzed using a mixed-effects logistic regression model. Second, the link between dRPEDIFF and session types with distinctive external profiles was examined using the Pearson chi-square test of independence. On average, players rated their session perceived breathlessness and leg-muscle exertion differently in 22% of the sessions (range: 0%-64%). Confidence limits for the effect of single external variables on dRPEDIFF spanned across largely positive and negative values for all variables, indicating no conclusive findings. The analysis based on session type indicated that players differentiated more often in matches and intense training sessions, but there was no pattern in the direction of differentiation. The findings of this study provide no evidence supporting the utility of dRPE for monitoring internal intensity and load in football.



#23 Effects of Low vs Moderate Dose of Recreational Football on Cardiovascular Risk Factors

Reference: Eur J Sport Sci. 2022 Jun 6;1-19. doi: 10.1080/17461391.2022.2086488. Online ahead of print.

Authors: Roberto Modena, Franco M Impellizzeri, Alessandro Fornasiero, Federico Schena

Summary: This study aimed to compare the effectiveness of recreational football performed once (LOW) vs. twice (MOD) a week on cardiovascular risk factors in healthy, sedentary men. Body composition, resting blood pressure, blood lipid profile and maximal oxygen consumption (VO2max) were measured at baseline, after a 12-week control and training period, using an interrupted time series study (study 1, n=18: n=8, LOW and n=10, MOD) nested in a randomised parallel trial (study 2, n=34: n=18 LOW and n=16 MOD). After the intervention in the study 1, LDL-Cholesterol (-12.3 mg•dL-1 [-22.7 to -2.0]) and VO2max (4.5 ml•kg-¹•min-¹ [1.2 to 7.8 ]) changed in LOW whereas differences were found in weight (-2.1 kg [-3.7 to -0.4]), BMI (-0.7 kg•m-2 [-1.2 to -0.1]), total cholesterol (-22.2 mg•dL-1 [-36.0 to -8.4]), no-HDL-cholesterol (-17.5 mg•dL-1 [-30.5 to -4.5]), LDL-cholesterol (-14.9 mg•dL-1 [-23.6 to -6.2]) and VO2max (5.7 ml•kg-¹•min-¹ [2.8 to 8.6]) in MOD. Study 2 showed no evidence of differences between groups. Our results therefore, suggest positive health effects of recreational football even when performed at low frequency as it can happen in real context.






Seasonal Training Load Monitoring Among Elite Footballers: Perceived Exertion and Creatine Kinase Variations Between Microcycles

Seasonal Training Load Monitoring Among Elite Footballers: Perceived Exertion and Creatine Kinase Variations Between Microcycles.





Effect of training day, match, and length of the microcycle on workload periodization in professional football: A full-season study

The aims of this study were to: (a) describe and compare the volume and intensity from the workload of professional footballers between training and MD, and (b) analyse the effect the microcycle length on workload.





Individual player transfer values summer 2022

Summer break also means transfers.


I have had a look at the most expensive 30 players in Europe and their estimated transfer value.


Kylian Mbappé (€206) is back at the top of the list after resigning with PSG. The French world champion outranks recent Champions League winner Vinícius Júnior (€185M), as well as the new Manchester City striker Erling Haaland (€153M).



Whilst not being included in the top 30. Benfica’s striker Darwin Núñez (€70M) has the highest valuation for non-big-5 league players. The youngest player in the top 100 is 17-year-old Pablo Gavi (€58M) and the oldest one is Kevin de Bruyne (30 years of age with €57) 


I have also summarized the numbers with regards to the clubs involved. 



The two Spanish top sites are leading the table. FC Barcelona values 458 mio € (with only players in the top 30 included) followed by Real Madrid 440. Four English teams making up positions 3-6, ManCity, Liverpool FC, Manchester FC and Chelsea.


English Premier League clubs dominate the ranking with 41 representatives in the top 100. 






Small-Sided Soccer Games with Larger Relative Areas Result in Higher Responses: A Systematic and Meta-Analytical Review

This study aimed to systematically review the influence of the relative area on athletes’ physical and physiological responses (outcomes) during small-sided games of soccer which were not matched to the relative area. It also presents a meta-analysis comparing standard small-sided games protocols with different relative areas.





Center backs work hardest when playing in a back three: The influence of tactical formation on physical and technical match performance

The purpose of this study was to investigate whether tactical formation affects the physical and technical match performance of professional soccer players in the first German Bundesliga.





Latest research in football - week 21 - 2022

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 The muscle contractile properties in female soccer players: inter-limb comparison using tensiomyography

Reference: J Musculoskelet Neuronal Interact. 2022 Mar 1;22(2):179-192.

Authors: Armin H Paravlic, Zoran Milanović, Ensar Abazović, Goran Vučković, Darjan Spudić, Ziva Majcen Rošker, Maja Pajek, Janez Vodičar

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Summary: The present study aimed to: i) determine the contractile properties of the major lower limb muscles in female soccer players using tensiomyography; ii) investigate inter-limb differences; and iii) compare inter-limb differences between different selections and playing positions. A total of 52 female soccer players (A team; U19 and U17) were recruited. The vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), biceps femoris (BF), gastrocnemius medialis (GM), lateralis (GL) and tibialis anterior (TA) of both lower limbs were evaluated. When the entire sample was assessed regardless of selection or playing position, there were significant inter-limb differences in all measured muscles except BF. Compared to the non-dominant limb, the dominant limb had higher delay time in VL (p=0.008), while showing lower values in VM (p=0.023), GL (p=0.043) and GM (p=0.006). Contraction time was lower in the RF of the dominant limb (p=0.005) and VM (p=0.047), while showing higher values in VL (p=0.036) and TA (p<0.001) as compared to the non-dominant limb. Given the differences found between the limbs in the whole sample studied, it is necessary to examine both limbs to gather a more in-depth understanding of underlying mechanisms related to neuromuscular functions in female soccer players.



#2 Age-Related Differences in the Anthropometric and Physical Fitness Characteristics of Young Soccer Players: A Cross-Sectional Study

Reference: Children (Basel). 2022 May 1;9(5):650. doi: 10.3390/children9050650.

Authors: Koulla Parpa, Marcos Michaelides

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Summary: Considering that most professional academies seek to optimize the early detection and physical development of their younger players, the purpose of this study was to examine the anthropometric and physical fitness characteristics in a large cross-sectional sample of youth soccer players in Eastern Europe, starting from a very young age during their in-season period. Three hundred and thirteen soccer players (n = 313), grouped into eight age categories, participated in the study. On the basis of chronological age, the group categories were: 7 (n = 26), 8 (n = 41), 9 (n = 46), 10 (n = 48), 11 (n = 42), 12 (n = 47), 13 (n = 43), and 14 years old (n = 20). The players underwent an anthropometric evaluation, flexibility, handgrip strength, vertical jump performance, speed, and agility assessments. A one-way multivariate analysis of variance (MANOVA) indicated significant differences in the anthropometric and physical fitness variables based on chronological age (F = 13.40, p &lt; 0.05, Wilk's Λ = 0.08, partial η2 = 0.30). Concurrently, there were significant growth and physical fitness differences even in players born in the same chronological year. It is believed that the results have important practical implications, especially for those involved in youth soccer. Based on our results, coaches should contemplate speed and agility development in training sessions starting from a much younger age, as sprinting while changing directions has been considered an essential prerequisite in soccer.



#3 Alterations in Cortical Activation among Soccer Athletes with Chronic Ankle Instability during Drop-Jump Landing: A Preliminary Study

Reference: Brain Sci. 2022 May 19;12(5):664. doi: 10.3390/brainsci12050664.

Authors: Xiaoya Zhang, Wanrongyu Su, Bin Ruan, Yu Zang

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Summary: Chronic ankle instability (CAI) is a common peripheral joint injury and there is still no consensus on the mechanisms. It is necessary to investigate electrocortical parameters to provide clinical insight into the functional alterations of brain activity after an ankle sprain, which would greatly affect the implementation of rehabilitation plans. The purpose of this study was to assess cortical activation characteristics during drop-jump landing among soccer athletes with CAI. A total of 24 participants performed the drop-jump landing task on a force platform while wearing a 64-channel EEG system. The differences of power spectral density (PSD) in theta and alpha (alpha-1 and alpha-2) bands were analyzed between two groups (CAI vs. CON) and between two limbs (injured vs. healthy). CAI participants demonstrated significantly higher theta power at the frontal electrode than that in healthy control individuals (F(1,22) = 7.726, p = 0.011, η2p = 0.260). No difference in parietal alpha-1 and alpha-2 power was found between groups (alpha-1: F(1,22) = 0.297, p = 0.591, η2p = 0.013; alpha-2: F(1,22) = 0.118, p = 0.734, η2p = 0.005). No limb differences were presented for any frequency band in selected cortical areas (alpha-1: F(1,22) = 0.149, p = 0.703, η2p = 0.007; alpha-2: F(1,22) = 0.166, p = 0.688, η2p = 0.007; theta: F(1,22) = 2.256, p = 0.147, η2p = 0.093). Theta power at the frontal cortex was higher in soccer athletes with CAI during drop-jump landing. Differences in cortical activation provided evidence for an altered neural mechanism of postural control among soccer athletes with CAI.



#4 Acute arm and leg muscle glycogen and metabolite responses to small-sided football games in healthy young men

Reference: Eur J Appl Physiol. 2022 Jun 1. doi: 10.1007/s00421-022-04970-y. Online ahead of print.

Authors: Jeppe Panduro, Jeppe F Vigh-Larsen, Georgios Ermidis, Susana Póvoas, Jakob Friis Schmidt, Karen Søgaard, Peter Krustrup, Magni Mohr, Morten Bredsgaard Randers

Summary: Studies have indicated upper body involvement during football, provoking long-term muscular adaptations. This study aimed at examining the acute metabolic response in upper and lower body skeletal muscle to football training organized as small-sided games (SSG). Ten healthy male recreational football players [age 24 ± 1 (± SD) yrs; height 183 ± 4 cm; body mass 83.1 ± 9.7 kg; body fat 15.5 ± 5.4%] completed 1-h 5v5 SSG (4 × 12 min interspersed with 4-min recovery periods). Muscle biopsies were obtained from m. vastus lateralis (VL) and m. deltoideus (DE) pre- and post-SSG for muscle glycogen and metabolite analyses. Blood lactate samples were obtained at rest, middle and end of the SSG. Muscle glycogen in VL decreased (P < 0.01) by 21% and tended (P = 0.08) to decrease in DE by 13%. Muscle lactate increased in VL (117%; P < 0.001) and DE (81%; P < 0.001) during the game, while blood lactate rose threefold. Muscle ATP and PCr were unaltered, but intermuscular differences were detected for ATP at both time points (P < 0.001) and for PCr at pre-SSG (P < 0.05) with VL demonstrating higher values than DE, while muscle creatine rose in VL (P < 0.001) by 41% and by 22% in DE (P = 0.02). Baseline citrate synthase maximal activity was higher (P < 0.05) in VL compared to DE, whereas baseline muscle lactate concentration was higher (P < 0.05) in DE than VL. The upper body may be extensively involved during football play, but besides a rise in muscle lactate in the deltoideus muscle similar to the leg muscles, the present study did not demonstrate acute metabolic changes of an order that may explain the previously reported training effect of football play in the upper extremities.



#5 The Navigation Ability Test (NAT 2.0): From Football Player Performance to Balance Rehabilitation in Chronic Unilateral Vestibular Loss

Reference: Audiol Res. 2022 May 10;12(3):249-259. doi: 10.3390/audiolres12030026.

Authors: Paolo Gamba, Riccardo Guidetti, Cristiano Balzanelli, Maurizio Bavazzano, Andrea Laborai

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Summary: In humans, spatial orientation consists of the ability to move around the environment through memorized and pre-programmed movements, according to the afferent sensory information of the body and environmental analysis of the Central Nervous System (CNS). The purpose of this study is to analyze the abilities of professional athletes, such as footballers, to use mental navigation systems, cognitive maps, and memorized motor patterns in order to obtain better physical performance and to obtain useful information for training both non-sports subjects and vestibular patients for rehabilitation purposes. All the motor performances of sportsmen, healthy non-sporting subjects, or vestibular patients are based on the acquisition of visual-spatial and training information. In this study, we analyzed the visual-spatial performance of 60 trained sportsmen (professional footballers), 60 healthy non-sports subjects, and 48 patients affected by chronic unilateral vestibular loss by means of the Navigation Ability Test 2.0. A score based on the number of targets correctly reached in the various tests quantifies the degree of performance of the subjects. NAT 2.0 scores progressively improve from vestibular subjects to healthy non-sporting subjects to footballers. NAT 2.0 scores improve in all three subject groups as the number of tasks performed in all patient groups increases, regardless of gender and age. The analysis of performance data through NAT 2.0 in athletes (footballers) opens new perspectives for rehabilitation purposes, regardless of age, sex, and training conditions, both in healthy non-sporting subjects to improve their sporting potential and in patients affected by chronic vestibular dysfunction, in order to optimize their motor skills and prevent falls.



#6 Off-ball behavior in association football: A data-driven model to measure changes in individual defensive pressure

Reference: J Sports Sci. 2022 May 31;1-14. doi: 10.1080/02640414.2022.2081405. Online ahead of print.

Authors: Mat Herold, A Hecksteden, D Radke, F Goes, S Nopp, T Meyer, M Kempe

Summary: This study describes an approach to evaluate the off-ball behaviour of attacking players in association football. The aim was to implement a defensive pressure model to examine an offensive player's ability to create separation from a defender using 1411 high-intensity off-ball actions including 988 Deep Runs (DRs) DRs and 423 Change of Directions (CODs). Twenty-two official matches (14 competitive matches and 8 friendlies) of the German National Team were included in the research. To validate the effectiveness of the pressure model, each pass (n = 25,418) was evaluated for defensive pressure on the receiver at the moment of the pass and for the pass completion rate (R = -.34, p < .001). Next, after assessing the inter-rater reliability (Fleiss Kappa of 80 for DRs and 78 for CODs), three expert raters annotated all DRs and CODs that met the pre-set criteria. A time-series analysis of each DR and COD was calculated to the nearest 0.1 second, finding a slight increase in pressure from the start to the end of the off-ball actions as defenders re-established proximity to the attacker after separation was created. A linear mixed model using run type (DR or COD) as a fixed effect with the local maximum as a fixed effect on a continuous scale resulted in p < 0.001, d = 4.81, CI = 0.63 to 0.67 for the greatest decrease in pressure, p < 0.001, d = 0.143, CI = 9.18 to 10.61 for length of the longest decrease in pressure, and p < 0.001, d = 1.13, CI = 0.90 to 1.11 for the fastest rate of decrease in pressure. As these values pertain to the local maximum, situations with greater starting pressure on the attacker often led to greater subsequent decreases. Furthermore, there was a significant (p < .0001) difference between offensive and defensive positions and the number of off-ball actions. Results suggest the model can be applied to quantify and visualise the pressure exerted on non-ball-possessing players. This approach can be combined with other methods of match analysis, providing practitioners with new opportunities to measure tactical performance in football.



#7 COVID-19 Infection among Elite Football Players: A Nationwide Prospective Cohort Study

Reference: Vaccines (Basel). 2022 Apr 19;10(5):634. doi: 10.3390/vaccines10050634.

Authors: Dimitrios Papagiannis, Theodoros Laios, Konstantinos Tryposkiadis, Konstantinos Kouriotis, Xenophon Roussis, Georgios Basdekis, Panagiotis Boudouris, Christos Cholevas, Stergios Karakitsios, Pindaros Kakavas, Theoharis Kiriakidis, Panagiotis Kouloumentas, Georgios Kouvidis, Grigoris Manoudis, Pantelis Nikolaou, Christos Theos, Andreas-Nikolaos Piskopakis, Ioannis Rallis, Stavros Ristanis, Alexandros Toliopoulos, Grigoris Zisis, Yiannis Theodorakis, Konstantinos I Gourgoulianis, Georgios Rachiotis

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Summary: Little is known about the risk of COVID-19 infection among footballers. We aimed to investigate the incidence and characteristics of COVID-19 infection among footballers. In total, 480 football players of Super League Greece and 420 staff members participated in a prospective cohort study, which took place from May 2020 to May 2021. Nasopharyngeal swabs were collected from footballers and staff members weekly. All samples (n = 43,975) collected were tested using the reverse transcriptase polymerase chain reaction (RT-PCR) test for the detection of "SARS-CoV-2". In total, 190 positive cases (130 among professional football players and 60 among staff) were recorded. Out of the 190 cases that turned positive, 64 (34%) cases were considered as symptomatic, and 126 (66%) cases were asymptomatic. The incidence rate of a positive test result for footballers was 0.57% (confidence interval (CI) 0.48-0.68%) and for staff members it was 0.27% (CI 0.20%, 0.34%), respectively. Footballers recorded a twofold increased risk of COVID-19 infection in comparison to staff members (relative risk = 2.16; 95% CI = 1.59-2.93; p-value &lt; 0.001). No significant transmission events were observed during the follow-up period. We found a low incidence of COVID-19 infection among professional footballers over a long follow-up period. Furthermore, the implementation of a weekly diagnostic testing (RT-PCR) was critical to break the transmission chain of COVID-19, especially among asymptomatic football players and staff members.



#8 Physical Demands during the Game and Compensatory Training Session (MD + 1) in Elite Football Players Using Global Positioning System Device

Reference: Sensors (Basel). 2022 May 19;22(10):3872. doi: 10.3390/s22103872.

Authors: Gabriel Calderón-Pellegrino, Leonor Gallardo, Jorge Garcia-Unanue, Jose Luis Felipe, Antonio Hernandez-Martin, Víctor Paredes-Hernández, Javier Sánchez-Sánchez

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Summary: The aims of this study were to analyze the differences of physical demands of non-starter players regarding the playing time during the competition and to evaluate the physical demands of the compensatory training (MD + 1C) for substitute players in elite football. The match statistics and MD + 1C of substitute players from a professional Spanish LaLiga football club were analyzed using a 10-Hz global positioning system (GPS) Apex GPS system device, which has been validated as a reliable and valid method to analyze performance in team sports, during all games of the 2016/2017, 2017/2018 and 2018/2019 seasons. The starting players showed both lower total distances covered and high-intensity actions compared to the substitutes. Regarding the minutes played by the substitutes, greater physical performance was found for the players with fewer minutes (5-15 min). Furthermore, no differences were found between first and second divisions regarding physical performance of substitutes (p &gt; 0.05). This study highlights the importance of individualizing the workload of training sessions for substitutes and starters. Furthermore, the complementary session should be individualized according to the minutes played by the substitutes. These players are potentially under-loaded compared to starters, especially in terms of high-intensity actions, therefore additional session-specific training for each substitute would be useful to reach the optimal training load according to the minutes played during the game.



#9 The Influence of Maximum Squatting Strength on Jump and Sprint Performance: A Cross-Sectional Analysis of 492 Youth Soccer Players

Reference: Int J Environ Res Public Health. 2022 May 11;19(10):5835. doi: 10.3390/ijerph19105835.

Authors: Michael Keiner, Torsten Brauner, Björn Kadlubowski, Andre Sander, Klaus Wirth

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Summary: This study aims to analyze the influence of relative strength performance, determined by parallel back squats (REL SQ), on 30 m sprinting (LS) and on jumping performance (squat [SJ], countermovement [CMJ]) in a large sample (n = 492) of elite youth soccer players. The soccer players were divided into subgroups based on their strength performance: strength level 1 (0.0-0.5 REL SQ), strength level 2 (&gt;0.5-1.0 REL SQ), strength level 3 (&gt;1.0 to 1.5 REL SQ), strength level 4 (&gt;1.5 to 2.0 REL SQ), and strength level 5 (&gt;2.0 REL SQ). The results of this study show that REL SQ explains 45-53% (r = |0.67-0.73|) of the variance of SJ, CMJ, and LS for the total sample. Strength levels 2-4 showed similar coefficients of correlation in jumping performance (r = |0.42-0.55|) and strength levels 2 and 3 in sprint performance (r = |0.41|). The respective extreme strength levels showed lower coefficients of correlation with the sprinting and jumping performance variables (r = |0.11-0.29|). No coefficients could be calculated for strength level 5 because no athlete achieved an appropriate strength level (&gt;2.0 REL SQ). The data from this study show a clear influence of REL SQ on sprint and jump performance, even in a large sample.



#10 Validation of Instrumented Football Shoes to Measure On-Field Ground Reaction Forces

Reference: Sensors (Basel). 2022 May 11;22(10):3673. doi: 10.3390/s22103673.

Authors: Alexandre Karamanoukian, Jean-Philippe Boucher, Romain Labbé, Nicolas Vignais

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Summary: Ground reaction forces (GRF) have been widely studied in football to prevent injury. However, ambulatory tools are missing, posing methodological limitations. The purpose of this study was to assess the validity of an innovative football shoe measuring normal GRF (nGRF) directly on the field through instrumented studs. A laboratory-based experiment was first conducted to compare nGRF obtained with the instrumented shoe (IS) to vertical GRF (vGRF) obtained with force platform (FP) data, the gold standard to measure vGRF. To this aim, three subjects performed 50 steps and 18 counter-movement jumps (CMJs). Secondly, eleven subjects completed running sprints at different velocities on a football field, as well as CMJs, while wearing the IS. Good to excellent agreement was found between the vGRF parameters measured with the FP and the nGRF measured by the IS (ICC &gt; 0.75 for 9 out of 11 parameters). Moreover, on-field nGRF patterns demonstrated a progressive and significant increase in relation with the running velocity (p &lt; 0.001). This study demonstrated that the IS is a highly valid tool to assess vGRF patterns on a football field. This innovative way to measure vGRF in situ could give new insights to quantify training load and detect neuromuscular fatigue.



#11 Nutritional Intake and Training Load of Professional Female Football Players during a Mid-Season Microcycle

Reference: Nutrients. 2022 May 21;14(10):2149. doi: 10.3390/nu14102149.

Authors: César Leão, António Pedro Mendes, Catarina Custódio, Mafalda Ng, Nuno Ribeiro, Nuno Loureiro, João Pedro Araújo, José Afonso, Sílvia Rocha-Rodrigues, Francisco Tavares

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Summary: Football (soccer) is a high-intensity intermittent sport with large energy demands. In a repeated-measures design, we analysed the nutritional intake and training load of fourteen female football players (22.50 ± 4.38 y; 57.23 ± 8.61 kg; 164 ± 6.00 cm; 18.33 ± 2.48% of fat mass and 23.71 ± 2.51 kg of muscle mass) competing in the highest female Football Portuguese League across a typical mid-season microcycle. The microcycle had one match day (MD), one recovery session (two days after the MD, MD+2), three training sessions (MD-3, MD-2, MD-1) and two rest days (MD+1). Energy intake and CHO ( intake were lower on the days before the competition (MD+2, MD-3, MD-2 and MD-1 vs. MD; p &lt; 0.05; ES: 0.60-1.30). Total distance, distance covered at high-speed running (HSRD) and the high metabolic distance load (HMLD) were lower on MD+2, MD-3 and MD-1 compared with MD (p &lt; 0.05; ES: &lt;0.2-5.70). The internal training load was lower in all training sessions before the competition (MD+2, MD-3, MD-2 and MD-1 vs. MD; p ≤ 0.01; ES: 1.28-5.47). Despite the small sample size and a single assessment in time, the results suggest that caloric and CHO intake were below the recommendations and were not structured based on the physical requirements for training sessions or match days.



#12 Cardiopulmonary Exercise Testing and Cardiac Biomarker Measurements in Young Football Players: A Pilot Study

Reference: J Clin Med. 2022 May 14;11(10):2772. doi: 10.3390/jcm11102772.

Authors: Alexandru-Dan Costache, Mihai Roca, Cezar Honceriu, Irina-Iuliana Costache, Maria-Magdalena Leon-Constantin, Ovidiu Mitu, Radu-Ștefan Miftode, Alexandra Maștaleru, Dan Iliescu-Halițchi, Codruța-Olimpiada Halițchi-Iliescu, Adriana Ion, Ștefania-Teodora Duca, Delia-Melania Popa, Beatrice Abălasei, Veronica Mocanu, Florin Mitu

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Summary: Constant and intense physical activity causes physiological adaptive changes in the human body, but it can also become a trigger for adverse events, such as sudden cardiac arrest or sudden cardiac death. Our main objective was to assess the use of combined cardiopulmonary exercise testing (CPET) and cardiac biomarker determinants in young professional athletes. We conducted a study which involved the full examination of 19 football players, all male, aged between 18 and 20 years old. They underwent standard clinical and paraclinical evaluation, a 12-lead electrocardiogram (ECG), and transthoracic echocardiography (TTE). Afterwards, a tailored CPET was performed and peripheral venous blood samples were taken before and 3 h after the test in order to determine five biomarker levels at rest and post-effort. The measured biomarkers were cardiac troponin I (cTnI), myoglobin (Myo), the MB isoenzyme of creatine-kinase (CK-MB), the N-terminal prohormone of brain natriuretic peptide (NT-proBNP) and D-dimers. While cTnI and NT-proBNP levels were undetectable both at rest and post-effort in all subjects, the variations in Myo, CK-MB and D-dimers showed significant correlations with CPET parameters. This highlights the potential use of combined CPET and biomarker determinants to evaluate professional athletes, and encourages further research on larger study groups.



#13 Neuromuscular Fatigue in Cerebral Palsy Football Players after a Competitive Match According to Sport Classification and Playing Position

Reference: Int J Environ Res Public Health. 2022 May 17;19(10):6070. doi: 10.3390/ijerph19106070.

Authors: Matías Henríquez, Luis Felipe Castelli de Campos, Fernando Muñoz-Hinrichsen, María Isabel Cornejo, Javier Yanci, Raul Reina

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Summary: This study aimed to determine the rated perceived exertion (RPE) and match load (RPE-ML) to compare pre-post-match vertical jump (VJ) capacity according to cerebral palsy (CP) players' sport classes (i.e., FT1-FT3) and playing positions and to explore whether the neuromuscular performance variation is associated with the internal load of para-footballers with CP. Fifty-six male para-footballers performed two VJ tests before and immediately after a competitive CP football match, followed by measurements of the players' RPE and RPE-ML. There were no significant differences (p &gt; 0.05) in the pairwise comparisons for RPE and RPE-ML according to sport classes and playing position. A significant reduction in the VJ performance was found for each player sport class and playing position in squat jump (SJ) (p &lt; 0.01; 0.24 &lt; dg &lt; 0.58) and countermovement jump (CMJ) (p &lt; 0.05; 0.22 &lt; dg &lt; 0.45). Regarding the pairwise comparisons, players with the minimal impairment criteria (FT3) obtained higher deficit scores during SJ than those belonging to the FT1 and FT2 (p = 0.003; 1.00 &lt; dg &lt; 1.56). Defenders experienced the lowest performance compared to midfielders and attackers in SJ performance (p = 0.027; 0.94 &lt; dg &lt; 1.28). Significant correlations were obtained between ΔSJ or ΔCMJ and RPE or RPE-ML (r = -0.58 to -0.75; p &lt; 0.001). These findings provide novel information supporting the notion that fatigue induced after a competitive match causes notable impairments in VJ performance differentiated according to sport class and playing position in para-footballers with CP.



#14 Sex Differences in Pre-Season Anthropometric, Balance and Range-of-Motion Characteristics in Elite Youth Soccer Players

Reference: Healthcare (Basel). 2022 Apr 28;10(5):819. doi: 10.3390/healthcare10050819.

Authors: Luis Llurda-Almuzara, Albert Pérez-Bellmunt, Noé Labata-Lezaun, Carlos López-de-Celis, Jason Moran, Nicholas C Clark

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Summary: In soccer, injury epidemiology differs between males and females. It is clinically useful to know whether there are between-sex differences in selected characteristics relevant to primary injury risk and injury prevention practices. The purpose of this study was to explore between-sex differences in anthropometric, balance, and range-of-motion characteristics in Spanish elite male and female youth soccer players. This was a pre-season cross-sectional study. Sixty-nine males (age 16.8 ± 0.9 yr; height 175.9 ± 6.8 cm; mass 67.9 ± 6.3 kg) and thirty-seven females (age 17.2 ± 1.7 yr; height 164.0 ± 6.3 cm; mass 59.0 ± 5.8 kg) participated. Anthropometrics (standing/sitting height, bodymass, right/left leg length) and right/left anterior reach test (ART), hip internal/external active range of motion, active knee extension (AKE), and weightbearing lunge test (WBLT) were measured. Between-sex differences were assessed with Bonferroni-corrected Mann-Whitney U tests and Cliff's delta (d). Between-sex significant differences (p &lt; 0.003, d ≥ 0.50) were observed for anthropometric data and for hip internal rotation. No between-sex significant differences were observed for ART/AKE/WBLT measures. Between-sex significant differences with large effect sizes were identified for anthropometric data and right/left hip internal rotation. The present study adds new data to the literature for young Spanish male and female soccer players. The present findings will help inform clinical reasoning processes and future injury prevention research for elite male and female youth soccer players.



#15 Associations between Training Load and Well-Being in Elite Beach Soccer Players: A Case Report

Reference: Int J Environ Res Public Health. 2022 May 20;19(10):6209. doi: 10.3390/ijerph19106209.

Authors: Júlio A Costa, Pedro Figueiredo, Alberto Prata, Tiago Reis, Joana F Reis, Luís Nascimento, João Brito

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Summary: The current case study aimed to quantify within-subjects correlations between training load and well-being in elite male beach soccer players. Data were obtained over three consecutive days during the preparation camp for the FIFA Beach Soccer World Cup Russia 2021. The session rating of perceived exertion (s-RPE) and external training load metrics using global positioning system (GPS) were recorded. Eleven players reported perceived well-being (sleep quality, fatigue, muscle soreness and stress) using a Likert scale (Hooper Index) before breakfast. Within-subjects correlation coefficients between workload and well-being were calculated. Workload metrics and perceived well-being indices were significantly lower on day three than on days one and two. The Hooper Index presented a very large positive correlation with s-RPE (r = 0.86 [0.67, 0.94], 95% confidence interval, CI), exposure time (r = 0.88 [0.71, 0.95]), total distance (r = 0.83 [0.60, 0.93]), high-speed distance (r = 0.77 [0.50, 0.91]), and number of sprints (r = 0.75 [0.47, 0.90]). Sleep quality presented a moderate to large positive correlation with s-RPE (r = 0.51 [0.11, 0.77]), exposure time (r = 0.50 [0.10, 0.76]), high-speed distance (r = 0.53 [0.15, 0.78]), number of sprints (r = 0.62 [0.28, 0.83]) and total distance (r = 0.41 [0.18, 0.78]). Fatigue presented a large to very large positive correlation with s-RPE (r = 0.85 [0.66, 0.94]), exposure time (r = 0.90 [0.78, 0.96]), total distance (r = 0.86 [0.68, 0.94]), high-speed distance (r = 0.65 [0.31, 0.84]) and number of sprints (r = 0.56 [0.18, 0.79]). Muscle soreness presented a large to very large positive correlation with s-RPE (r = 0.79 [0.56, 0.91]), exposure time (r = 0.83 [0.62, 0.93]), total distance (r = 0.81 [0.59, 0.92]), high-speed distance (r = 0.75 [0.47, 0.89]) and number of sprints (r = 0.59 [0.22, 0.81]). Overall, workload presented a meaningful correlation with perceived well-being indices in elite male beach soccer players during a training camp. These findings suggest that workload metrics and perceived well-being indices can be implemented into the daily routine of an elite beach soccer team, which may assist coaches, sports scientists, and practitioners in better preparing players for beach soccer competitions.



#16 A low-volume Nordic hamstring curl programme improves change of direction ability, despite no architectural, strength or speed adaptations in elite youth soccer players

Reference: Res Sports Med. 2022 Jun 1;1-12. doi: 10.1080/15438627.2022.2079984. Online ahead of print.

Authors: James Siddle, Kristian Weaver, Matt Greig, Damian Harper, Christopher Michael Brogden

Summary: Nordic hamstring curls (NHC) are a commonly used injury intervention method in amateur team sports. Seventeen elite male academy soccer players performed an 8-week low volume NHC programme. Pre-post intervention measures of isokinetic eccentric knee flexor (KF) strength, linear speed, COD performance, hamstring muscle thickness, pennation angle and fascicle length were recorded. No significant main effects were observed for measures of isokinetic KF strength (P ≥ 0.19), linear sprint speed (P ≥ 0.47) or hamstring muscle architecture (P ≥ 0.30). However, significance was noted for improved COD performance (P < 0.01; mean difference, -0.06, p = 0.001, 95% CI = 0.03 to 0.09; d = 0.80), exceeding the minimal detectable difference (MDD = 0.05 s). A low-volume NHC intervention may contribute to significant improvements in COD ability, independent of no significant changes in eccentric KF strength, linear sprint speed or muscle architectural properties in elite youth soccer players.



#17 Semantic Concept Mining Based on Hierarchical Event Detection for Soccer Video Indexing

Reference: J Multimed. 2009 Oct;4(5):298-312. doi: 10.4304/jmm.4.5.298-312.

Authors: Maheshkumar H Kolekar, Kannappan Palaniappan, Somnath Sengupta, Gunasekaran Seetharaman

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Summary: In this paper, we present a novel automated indexing and semantic labeling for broadcast soccer video sequences. The proposed method automatically extracts silent events from the video and classifies each event sequence into a concept by sequential association mining. The paper makes three new contributions in multimodal sports video indexing and summarization. First, we propose a novel hierarchical framework for soccer (football) video event sequence detection and classification. Unlike most existing video classification approaches, which focus on shot detection followed by shot-clustering for classification, the proposed scheme perform a top-down video scene classification which avoids shot clustering. This improves the classification accuracy and also maintains the temporal order of shots. Second, we compute the association for the events of each excitement clip using a priori mining algorithm. We pro- pose a novel sequential association distance to classify the association of the excitement clip into semantic concepts. For soccer video, we have considered goal scored by team-A, goal scored by team-B, goal saved by team-A, goal saved by team-B as semantic concepts. Third, the extracted excitement clips with semantic concept label helps us to summarize many hours of video to collection of soccer highlights such as goals, saves, corner kicks, etc. We show promising results, with correctly indexed soccer scenes, enabling structural and temporal analysis, such as video retrieval, highlight extraction, and video skimming.



#18 Modelling the potential spread of virus during soccer matches

Reference: BMJ Open Sport Exerc Med. 2022 May 12;8(2):e001268. doi: 10.1136/bmjsem-2021-001268. eCollection 2022.

Authors: Nikolas Sten Knudsen, Manuel Mounir Demetry Thomasen, Thomas Bull Andersen

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Summary: In the present study, we model the potential spread of virus during soccer matches. Tracking data from 14 elite soccer matches was used. One player in each match was designated as a virus carrier (called 'infected player') for the purpose of the study. The exposure score (measured in seconds) was calculated as time spent closer than 1.5 m from the infected player or time spent in an exponentially declining zone, where the infected player was positioned earlier. The results revealed that, on average, each player was exposed for 87.8 s per match. Potential spread of virus during soccer matches was modelled and it revealed that the exposure to a virus during soccer matches is limited.



#19 Sponsorship by food and beverage companies in soccer: an analysis of the 2019 Copa América

Reference: Rev Saude Publica. 2022 May 27;56:41. doi: 10.11606/s1518-8787.2022056003491. eCollection 2022.

Authors: Larissa Cardoso de Miranda Araujo, Juliana de Paula Matos, Paula Martins Horta

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Summary: The aim was to identify the sponsorship by food and beverage companies of the teams participating in the 2019 Copa América Soccer Cup and associate this sponsorship with characteristics of the teams and their respective countries. The sponsors of the 10 teams participating in the 46th edition of the Copa América were identified. These entities were classified into (i) food companies, (ii) alcoholic beverage companies, and (iii) other segments. The food companies were classified according to their products, according to the NOVA classification. In addition, data on the number of titles previously won by the teams in the Copa America and the World Cup were obtained, as well as data on the countries' Human Development Index, annual per capita sales of ultra-processed foods, and annual per capita consumption of alcoholic beverages. A total of 89 sponsorships were identified for the 10 teams studied, some of these supporting two or more teams. Eighteen percent of the sponsors were food companies, with 12.4% being ultra-processed foods. The alcoholic beverage category represented 7.9% of the sponsors. Ultra-processed beverage and alcoholic beverage companies sponsored seven of the 10 teams studied. We noted higher participation of ultra-processed foods company sponsors in teams from countries with higher Human Development Index, sales of ultra-processed foods, and number of Copa América and World Cup titles. The sponsorship by alcoholic beverage companies was higher for teams from countries with lower Human Development Index, alcohol consumption, and number of Copa América and World Cup titles. A significant presence of ultra-processed food and alcoholic beverage companies as sponsors of South American soccer teams was noted, along with the fact that sport performance characteristics of the teams and socioeconomic and market issues of the countries are associated with the occurrence of sponsorship.







Exploring interactions between maturity status and playing time with fluctuations in physical fitness and hormonal markers in youth soccer players

The purpose of this study was to determine the differences in functional capacities and hormonal indices according to biological maturity and seasonal playing time status in young soccer players.





Variations in Internal and External Training Load Measures and Neuromuscular Performance of Professional Soccer Players

The aim was to  described the internal and external training loads (TLs) experienced by soccer players over a 4-week preseason and to examine their effects on vertical jump (VJ) performance, and investigated the relationships between different TL variables.





Game time by players born in 2001 or younger for 2021 and 2022

As clubs are always trying to recruit young players, below are the game times of different age groups for the entire year 2021 and 2022 so far.

Starting for the half-year 2022. Fabio Carvalho playing for Fulham FC lead the table followed by Lukeba (Olympique Lyonnais) and Bellingham (Borussia Dortmund).



The previous year (2021) Bellingham was again found in the top five, leading the table followed by Fabricio Díaz (Liverpool) and Fernandes (Santos FC) for the players born in 2003.



Players born in 2002 provided the following numbers: Zabarnyi (Dynamo Kyiv) 4736, Gravenberch (AFC Ajax) 4365 and Gonzalez (FC Barcelona) 4047 hours of game time.



Matheus Martinelli (Fluminense FC), Alberto (SC Internacional), and Alvarez (Penarol Montevideo) with 4854, 4506 and 4415 respectively need to be mentioned for the players born in 2001.



A quasi-longitudinal analysis provide some insights on how many minutes of game time is experienced with another year of age (or football).



Starting with an average game exposure of 2566 minutes for the top 20 players born in 2003 (for the 2001 year) players born in 2002 logged in 36,4% more game time. However, players born in 2001 had another 5,57% more playing minutes compared to their younger peers.


Over all age groups, RB Leipzig accumulated the most game times for their players born 2003 or younger for four players, followed by AFC Ajax, Bayer Leverkusen and FC Barcelona (all 3 players). The following teams had two players listed in their respected age category: AS Monaco, FC Kobenhavn, Santos FC, SE Palmeiras and Sparta Praha. 



If these number are due to the quality of recruitment and therefore the quality of players, club philosophy, training development, head coach ….etc. a mix of all is debatable. 











Ultrasound Shear Modulus and Thickness of Lateral Abdominal Muscles in Hip/Groin Problems in Youth Soccer

The objectives were to a) assess the relationship between LAM ultrasound measurements (elasticity and thickness) and self-reported subscales of the Copenhagen Hip and Groin Outcome Score (HAGOS) and b) compare LAM elasticity and thickness between asymptomatic and symptomatic sides.





The effects of individual and collective variability on youth players’ movement behaviours during football small-sided games

This study aimed to identify the effects of playing with additional individual (IND), collective (COL) or individual-collective (MIX) variability on youth football players’ performance during small-sided games.





Latest research in football - week 20 - 2022

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 Psychophysiological Stress Markers During Preseason Among Elite Female Soccer Players

Reference: J Strength Cond Res. 2022 Jun 1;36(6):1648-1654. doi: 10.1519/JSC.0000000000003702. Epub 2020 Jul 16.

Authors: Renata Botelho, Cesar C C Abad, Regina C Spadari, Ciro Winckler, Márcia C Garcia, Ricardo L F Guerra

Summary: This study aimed to investigate changes and correlations between mood states and various physiological stress markers after a 7-week preseason period among elite female soccer players. Twenty-four elite female soccer players participated in this study (26.4 ± 3.7 years). Their internal training load, mood states, day and evening salivary testosterone and cortisol concentrations, blood creatine kinase concentration (CK), and heart rate variability (HRV) were assessed during the first week of preseason (PRE), and again 7 weeks after a systematic training period (END). After the preseason, there were significant increases in subject negative mood scales (p ≤ 0.03; Effect Size [ES] > 0.60), total mood scores (p = 0.01; QI = 100/0/0; ES = 1.32), day and evening testosterone and cortisol concentrations (p ≤ 0.03; ES > 0.54), and CK concentrations (p = 0.01; QI = 100/0/0; ES = 1.54). Correlations were found between cortisol and tension (r = 0.53 and 0.60; p ≤ 0.02), cortisol and confusion (r = 0.75; p = 0.01), and cortisol and the LF/HF index of HRV (r = -0.52; p = 0.04). Mood states (except vigor), salivary testosterone, and cortisol concentrations, as well as CK, showed significant changes after a 7-week systematic training system. The cortisol was the factor most highly related to various mood states (including tension and confusion), and with the HRV indices. Coaches and researchers can use these data to design, monitor, and control soccer training programs, in particular throughout the preseason period.



#2 Comparison of the H:Q Ratio Between the Dominant and Nondominant Legs of Soccer Players: A Meta-Analysis

Reference: Sports Health. 2022 May 26;19417381221095096. doi: 10.1177/19417381221095096.

Authors: Fabian D Lutz, Christopher J Cleary, Hannah M Moffatt, Violet E Sullivan, Dain P LaRoche, Summer B Cook

Summary: Soccer players often have a dominant (D) leg, which could influence the relative strength between the quadriceps and hamstrings. The hamstring-to-quadriceps (H:Q) ratio can be assessed on a dynamometer at various velocities to provide information on injury risk. The objective was to assess the concentric hamstrings and concentric quadriceps strength ratio (conventional H:Q ratio) assessed in D and nondominant (ND) legs at various speeds in male soccer players. A systematic literature search was completed from inception to 2020 in PubMed, Academic Search Ultimate, CINAHL, and SPORTDiscus. Keywords associated with the H:Q ratio were connected with terms for soccer players. Titles and abstracts were screened by 2 reviewers based on inclusion and exclusion criteria related to sex, playing level, language, and measurement. A total of 81 studies were reviewed and 17 studies (21%) were used. A meta-analysis with random effects modeling generated standardized mean differences with 95% CIs between legs and speeds was applied. A total of 38 cohorts were identified, with 14, 13, and 11 cohorts assessed at low, intermediate, and high velocities, respectively. The Quality Assessment Tool for Observational Cohort and Cross-sectional Studies from the National Institutes of Health was used. The mean H:Q ratio at low velocities was 59.8 ± 9.5% in D leg and 58.6 ± 9.9% in ND leg, 64.2 ± 10.7% (D) and 63.6 ± 11.3% (ND) at the intermediate velocity, and 71.9 ± 12.7% (D) and 72.8 ± 12.7% (ND) at the high velocity. Low, intermediate, and high velocities had small effects of 0.13, 0.10, and -0.06, respectively. Conventional H:Q ratios vary across velocities but did not differ between D and ND limbs in male soccer players. This study may provide the foundation to establish norms and clinically meaningful differences.



#3 Training soccer goalkeeping skills: Is video modeling enough?

Reference: J Appl Behav Anal. 2022 May 26. doi: 10.1002/jaba.937. Online ahead of print.

Authors: Alexandra Capalbo, Raymond G Miltenberger, Jennifer L Cook

Summary: Scant literature exists assessing the effectiveness of video modeling (VM) alone in the sports literature. Further evaluations of VM to improve sports skills is warranted because VM is an accessible and efficient procedure that has successfully improved skills in other fields of practice (e.g., staff training, medical procedures). Additionally, behavior analysts have not evaluated interventions for improving goalkeeping skills for individual soccer players. Therefore, we replicated the 1 behavior-analytic sports study on VM (Quinn et al., 2020), using a multiple baseline design across behaviors to evaluate the effects of VM and VM + video feedback (VF) to train 3 goalkeeper skills to two 9-year-old soccer players. The results showed that, although VM had some effect on performance compared to baseline, VM + VF resulted in the robust outcomes necessary for proficient performance of the goalkeeper skills. We discuss the results and limitations.



#4 The effects of jump training on measures of physical performance, lower extremities injury incidence and burden in highly trained male soccer players

Reference: Res Sports Med. 2022 May 26;1-15. doi: 10.1080/15438627.2022.2079989. Online ahead of print.

Authors: Javier Sánchez-Sánchez, Luis Torres Martín, Rodrigo Ramirez-Campillo, Daniel Castillo, Javier Raya-González

Summary: This study aimed to analyse the effects of a 16-week jump training program on the physical performance and lower extremities injury profile in semi-professional male soccer players. Participants were randomly assigned to the control group (CG; n = 13; age = 21.7 ± 3.6 years) or the experimental group (EG; n = 10; age = 22.3 ± 3.5 years). Countermovement jump (CMJ) height (cm), 30 m linear sprint time (s) with split times at 10 m and 20 m distances, and change of direction speed (CODS; 10 + 10 m with 90° turn) time (s) with turns using the dominant or non-dominant leg, were assessed before and after the intervention. Lower extremity injuries sustained throughout the intervention period were collected. Significant within-group improvements were found in EG in CMJ (p = 0.01; effect size [ES] = 1.03; large). Additionally, between-group difference after intervention was found in CMJ (F = 4.42; p = 0.013) in favour of EG. Injury burden was 194.86 (CG) vs 71.37 (EG) days of absence/1,000 h (RR = 2.73; 95% CI 2.10-3.54; p < 0.001). No other significant within-group or between-group differences were found. In conclusion, compared to regular soccer training, jump training was effective to improve jumping ability and burden in soccer players.



#5 Intra- and Inter-Seasonal Fitness and Training Load Variations of Elite U20 Soccer Players

Reference: Res Q Exerc Sport. 2022 May 25;1-8. doi: 10.1080/02701367.2022.2074951. Online ahead of print.

Authors: Massimo Saccà, Danilo Bondi, Fabrizio Balducci, Cristian Petri, Giuseppe Mazza

Summary: Inherent physical and anthropometric traits of elite soccer players, influenced by nature and nurture, account for the emergence of performances across time.  The present study aimed to evaluate inter- and intraseasonal differences and the influence of playing position on training and fitness metrics in talented young soccer players. A total of 74 male players from U20 teams of a single elite club were tested both at beginning, during, and at the end of three consecutive competitive seasons. Players under went anthropometric measurement and were tested for aerobic, jumping, and sprinting performances; the GPS-derived measures of metabolic power (MP) and equivalent distance index (ED) of every athlete were analyzed. Difference between teams emerged in Mognoni's test, while it did not in countermovement jump and anthropometrics. ED was different across seasons. The model selection criteria revealed that the Bosco-Vittori test achieved the best fit. BMI and countermovement jump (CMJ) increased, and fat mass decreased, during season; different intraseasonal trends for CMJ. MP was slightly greater in midfielder. Network approaches in modeling performance metrics in sports team could unveil original interconnections between performance factors. In addition, the authors support multiparametric longitudinal assessments and a huge database of sports data for facilitating talent identification.



#6 Examining the influence of the Get aHEAD Safely in Soccer™ program on head impact kinematics and neck strength in female youth soccer players

Reference: Res Sports Med. 2022 May 24;1-11. doi: 10.1080/15438627.2022.2079982. Online ahead of print.

Authors: Victoria E Wahlquist, Joseph J Glutting, Thomas W Kaminski

Summary: The objective was to examine the efficacy of the Get aHEAD Safely in Soccer™ intervention on head impact kinematics and neck strength in female youth soccer players. The control group (CG) consisted of 13 players (age: 11.0 ± 0.4 yrs), while the experimental group (EG) consisted of 14 players (age: 10.6 ± 0.5 yrs). Head impact kinematics included peak linear acceleration (PLA), peak rotational acceleration (PRA), and peak rotational velocity (PRV). Pre- and post-season measures included strength measures of neck/torso flexion (NF/TF) and extension (NE/TE). Data were analysed using a multilevel linear model and ANOVA techniques. No differences in PLA, PRA, or PRV were observed between groups. The EG showed significant improvement in NF strength while the CG showed significant improvement in NE strength. Both groups significantly improved in TF pre- to post-season. The foundational strength components of the Get aHEAD Safely in Soccer program appear to show a benefit in youth soccer players beginning to learn the skill of purposeful heading.



#7 Descriptive trunk kinematics in healthy collegiate women's soccer players indicate trunk center of mass is laterally positioned prior to decelerating and cutting

Reference: J ISAKOS. 2022 Apr 4;S2059-7754(22)00019-0. doi: 10.1016/j.jisako.2022.03.002.

Authors: Celeste Dix, Amelia Arundale, Holly Silvers-Granelli, Adam Marmon, Ryan Zarzycki, Elisa Arch, Lynn Snyder-Mackler

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Summary: Trunk kinematics can contribute to lower extremity biomechanical risk factors for anterior cruciate ligament (ACL) injury. However, normative trunk kinematics during unilateral athletic tasks in a large population of "healthy" (no history of ACL injury and no known future ACL injury) women's soccer players have not been well-described. This study's purposes were to describe trunk kinematics in a population of 37 healthy collegiate women's soccer players completing a step-down, a deceleration, and a 90° cut, and to provide a reference for normative values. A cross-sectional cohort of 37 female soccer players were analysed for this study. Trunk forward flexion and lateral flexion were measured relative to the pelvis, and trunk centre of mass position was measured relative to the proximal tibia. Trunk kinematics were characterized by individual values at key events during the tasks and time-series curves normalized to 100% of the time. Participants demonstrated increasing trunk forward flexion with increasing knee flexion angle, small amounts of increasing ipsilateral trunk flexion with increasing peak knee abduction moment, and trunk centre of mass position that moved medially during the deceleration and cut tasks. Additionally, participants demonstrated peak trunk lateral flexion angles milliseconds before peak knee flexion angle. This study provides a reference for identifying aberrant trunk mechanics that may increase the risk for non-contact ACL injury.



#7 Real world complexities of periodization in a youth soccer academy: An explanatory sequential mixed methods approach

Reference: J Sports Sci. 2022 May 22;1-9. doi: 10.1080/02640414.2022.2080035. Online ahead of print.

Authors: Jake Pass, Lee Nelson, Greg Doncaster

Summary: The purpose of the study was to (1) assess the training load experienced during pre-season and in-season meso-cycles within youth academy soccer players and (2) investigate the extent to which the intended periodized approach was implemented, considering those factors that affected its realization. An explanatory sequential mixed-method design comprising two phases was adopted. Phase 1 encompassed the quantitative analysis of training load data, using 10 Hz GPS, and consisted of 17 youth academy soccer players (age 17 ± 1 yrs; stature 179 ± 9 cm; body mass 72 ± 9 kg), from a professional English soccer academy. Phase 2 involved the collection of qualitative data in relation to the data collected in phase 1 of the study. Three semi-structured interviews were conducted with the lead strength and conditioning coach at the same academy, to gain his reflections on the data, its alignments with desired outcomes, and factors that impacted on the enactment of the periodized training programme. The results provide original information on the training load experienced within a youth soccer academy and novel insights into the complex realities of enacting periodized training programmes in practice.



#8 Bilateral vs. Unilateral Countermovement Jumps: Comparing the Magnitude and Direction of Asymmetry in Elite Academy Soccer Players

Reference: J Strength Cond Res. 2022 Jun 1;36(6):1660-1666. doi: 10.1519/JSC.0000000000003679. Epub 2020 Jun 5.

Authors: Chris Bishop, Will Abbott, Calum Brashill, Anthony Turner, Jason Lake, Paul Read

Summary: The aims of this study were to compare the magnitude and direction of asymmetry in comparable bilateral and unilateral countermovement jumps (CMJs). Forty-five elite academy soccer players from under-23 (n = 15), under-18 (n = 16), and under-16 (n = 14) age groups performed bilateral and unilateral CMJs as part of their routine preseason fitness testing. For the magnitude of asymmetry, no significant differences were evident for any metric between tests. However, the eccentric impulse asymmetry was significantly greater than mean force and concentric impulse in both bilateral and unilateral tests (p < 0.01). For the direction of asymmetry, Kappa coefficients showed poor levels of agreement between test measures for all metrics (mean force = -0.15, concentric impulse = -0.07, and eccentric impulse = -0.13). The mean jump data were also presented relative to the body mass for each group. For the bilateral CMJ, significant differences were evident between groups but showed little consistency in the same group performing better or worse across metrics. For the unilateral CMJ, eccentric impulse was the only metric to show meaningful differences between groups, with the under-18 group performing significantly worse than under-23 and under-16 players. This study highlights that despite the magnitude of asymmetry being similar for each metric between comparable bilateral and unilateral CMJs, consistency in the direction of asymmetry was poor. In essence, if the right limb produced the larger force or impulse during a bilateral CMJ, it was rare for the same limb to perform superior during the unilateral task. Thus, practitioners should be aware that bilateral and unilateral CMJs present different limb dominance characteristics and should not use 1 test to represent the other when measuring between-limb asymmetries.



#9 Effects of Repeated Sprint Training With Progressive Elastic Resistance on Sprint Performance and Anterior-Posterior Force Production in Elite Young Soccer Players

Reference: J Strength Cond Res. 2022 Jun 1;36(6):1675-1681. doi: 10.1519/JSC.0000000000004242. Epub 2022 Mar 11.

Authors: Johan Le Scouarnec, Pierre Samozino, Benoit Andrieu, Teddy Thubin, Jean-Benoit Morin, François B Favier

Summary: This study aimed to determine whether repeated sprint training with progressive high elastic resistance could improve sprint performance and anterior-posterior (AP) force production capacities of elite young soccer players. Seven elite U19 soccer players underwent 10 sessions of elastic-resisted repeated sprints on 8 weeks, whereas 8 U17 players from the same academy (control group) followed the same protocol without elastic bands. Sprint performance and mechanical parameters were recorded on a 30-m sprint before and after training. The control group did not show change for any of the measured variables. In contrast, the elastic-resisted training resulted in a significant improvement of the sprint time (-2.1 ± 1.3%; p = 0.026; Hedges' g = -0.49) and maximal velocity (Vmax; +3.9 ± 2%; p = 0.029; Hedges' g = 0.61) reached during the 30-m sprint. These enhancements were concurrent with an increase in the maximal power output related to AP force (Pmax; +4.9 ± 5.1%%; p = 0.026; Hedges' g = 0.42). Although the theoretical maximal AP force (F0) remained unchanged in both groups, there was a medium but nonsignificant increase in theoretical maximal velocity (V0; +3.7 ± 2.5%; p = 0.13; Hedges' g = 0.5) only in the elastic group. Therefore, the present results show that sprint capacity of elite young soccer players can be further improved by adding incremental resistance against runner displacement to raise the ability to produce AP force, rather at high velocity in the final phase of the acceleration.



#10 Regional Bioelectrical Phase Angle Is More Informative than Whole-Body Phase Angle for Monitoring Neuromuscular Performance: A Pilot Study in Elite Young Soccer Players

Reference: Sports (Basel). 2022 Apr 22;10(5):66. doi: 10.3390/sports10050066.

Authors: Tindaro Bongiovanni, Alessio Rossi, Athos Trecroci, Giulia Martera, F Marcello Iaia, Giampietro Alberti, Giulio Pasta, Mathieu Lacome

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Summary: The objective of this study was to investigate the association between regional and total phase angle (PhA) with lower-body neuromuscular performance in young elite soccer players. Sixteen elite male soccer players (14.3 ± 1.0 years) participated in this study. Lower (LPhA)- and upper (UPhA)-hemisome PhA together with whole-body PhA (WBPhA) were measured by a bioelectrical-impedance analysis (BIA), while appendicular arm and leg lean soft tissue (ALST and LLST, respectively) were estimated. Urine osmolarity (UOsm) and urine-specific gravity (USG) were also considered. Sprints over 10 m and 20 m and countermovement jump (CMJ) tests were employed to evaluate neuromuscular performance. LPhA (p = 0.003) and UOsm (p = 0.012) explained 62% of the variance in the 10 m sprint. UOsm (p = 0.001) and both LPhA (p &lt; 0.001) and WBPhA (p = 0.024) explained 81% of the total variance in the 20 m sprint. The CMJ height was affected by LPhA (p &lt; 0.001) and UOsm (p = 0.024), which overall explained 68% of its variance (p &lt; 0.05), while 93% of the CMJ power variance was explained by LPhA (p &lt; 0.001), ALST (p &lt; 0.001), and WBPhA (p = 0.011). Regional PhA is a relevant and non-invasive tool to monitor lower-body neuromuscular performance in elite youth soccer. Specifically, LPhA may be favored over WBPhA as more informative.



#11 An Examination of Relative Age and Athlete Dropout in Female Developmental Soccer

Reference: Sports (Basel). 2022 May 20;10(5):79. doi: 10.3390/sports10050079.

Authors: Kristy L Smith, Patricia L Weir

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Summary: Sport dropout rates among children and youth are a concern for researchers and policy makers. The impact of relative age effects (RAEs) on dropout trends has not been adequately examined in female samples. The purpose of this study was to longitudinally examine dropout in a female soccer cohort in Ontario, Canada. Registration entries for a one-year cohort were examined across a seven-year period (n = 9908; age 10-16 years). A chi-square analysis established the presence of RAEs in the initial year of registration. Survival analyses assessed the impact of relative age, competition level, and community size on athlete dropout. A median survival rate of four years was observed for players born in the first quartile, while all remaining quartiles had a median survival of three years. Community size did not predict dropout in this analysis; however, competition level was a significant predictor, with competitive players being more likely to remain engaged vs. recreational players (55.9% vs. 20.7%). The observed trends are likely to have a significant impact from both a healthy development and systems perspective (e.g., economic/market loss). Intervention is needed to mitigate current dropout trends in female athletes. Practical applications are discussed.



#12 Multiagent off-screen behavior prediction in football

Reference: Sci Rep. 2022 May 23;12(1):8638. doi: 10.1038/s41598-022-12547-0.

Authors: Shayegan Omidshafiei, Daniel Hennes, Marta Garnelo, Zhe Wang, Adria Recasens, Eugene Tarassov, Yi Yang, Romuald Elie, Jerome T Connor, Paul Muller, Natalie Mackraz, Kris Cao, Pol Moreno, Pablo Sprechmann, Demis Hassabis, Ian Graham, William Spearman, Nicolas Heess, Karl Tuyls

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Summary: In multiagent worlds, several decision-making individuals interact while adhering to the dynamics constraints imposed by the environment. These interactions, combined with the potential stochasticity of the agents' dynamic behaviors, make such systems complex and interesting to study from a decision-making perspective. Significant research has been conducted on learning models for forward-direction estimation of agent behaviors, for example, pedestrian predictions used for collision-avoidance in self-driving cars. In many settings, only sporadic observations of agents may be available in a given trajectory sequence. In football, subsets of players may come in and out of view of broadcast video footage, while unobserved players continue to interact off-screen. In this paper, we study the problem of multiagent time-series imputation in the context of human football play, where available past and future observations of subsets of agents are used to estimate missing observations for other agents. Our approach, called the Graph Imputer, uses past and future information in combination with graph networks and variational autoencoders to enable learning of a distribution of imputed trajectories. We demonstrate our approach on multiagent settings involving players that are partially-observable, using the Graph Imputer to predict the behaviors of off-screen players. To quantitatively evaluate the approach, we conduct experiments on football matches with ground truth trajectory data, using a camera module to simulate the off-screen player state estimation setting. We subsequently use our approach for downstream football analytics under partial observability using the well-established framework of pitch control, which traditionally relies on fully observed data. We illustrate that our method outperforms several state-of-the-art approaches, including those hand-crafted for football, across all considered metrics.



#13 Return to Play Prediction Accuracy of the MLG-R Classification System for Hamstring Injuries in Football Players: A Machine Learning Approach

Reference: Sports Med. 2022 May 24. doi: 10.1007/s40279-022-01672-5. Online ahead of print.

Authors: Xavier Valle, Sandra Mechó, Eduard Alentorn-Geli, Tero A H Järvinen, Lasse Lempainen, Ricard Pruna, Joan C Monllau, Gil Rodas, Jaime Isern-Kebschull, Mourad Ghrairi, Xavier Yanguas, Ramon Balius, Adrian Martinez-De la Torre

Summary: Muscle injuries are one of the main daily problems in sports medicine, football in particular. However, we do not have a reliable means to predict the outcome, i.e. return to play from severe injury. The aim of the present study was to evaluate the capability of the MLG-R classification system to grade hamstring muscle injuries by severity, offer a prognosis for the return to play, and identify injuries with a higher risk of re-injury. Furthermore, we aimed to assess the consistency of our proposed system by investigating its intra-observer and inter-observer reliability. All male professional football players from FC Barcelona, senior A and B and the two U-19 teams, with injuries that occurred between February 2010 and February 2020 were reviewed. Only players with a clinical presentation of a hamstring muscle injury, with complete clinic information and magnetic resonance images, were included. Three different statistical and machine learning approaches (linear regression, random forest, and eXtreme Gradient Boosting) were used to assess the importance of each factor of the MLG-R classification system in determining the return to play, as well as to offer a prediction of the expected return to play. We used the Cohen's kappa and the intra-class correlation coefficient to assess the intra-observer and inter-observer reliability. Between 2010 and 2020, 76 hamstring injuries corresponding to 42 different players were identified, of which 50 (65.8%) were grade 3r, 54 (71.1%) affected the biceps femoris long head, and 33 of the 76 (43.4%) were located at the proximal myotendinous junction. The mean return to play for grades 2, 3, and 3r injuries were 14.3, 12.4, and 37 days, respectively. Injuries affecting the proximal myotendinous junction had a mean return to play of 31.7 days while those affecting the distal part of the myotendinous junction had a mean return to play of 23.9 days. The analysis of the grade 3r biceps femoris long head injuries located at the free tendon showed a median return to play time of 56 days while the injuries located at the central tendon had a shorter return to play of 24 days (p = 0.038). The statistical analysis showed an excellent predictive power of the MLG-R classification system with a mean absolute error of 9.8 days and an R-squared of 0.48. The most important factors to determine the return to play were if the injury was at the free tendon of the biceps femoris long head or if it was a grade 3r injury. For all the items of the MLG-R classification, the intra-observer and inter-observer reliability was excellent (k > 0.93) except for fibres blurring (κ = 0.68). The main determinant for a long return to play after a hamstring injury is the injury affecting the connective tissue structures of the hamstring. We developed a reliable hamstring muscle injury classification system based on magnetic resonance imaging that showed excellent results in terms of reliability, prognosis capability and objectivity. It is easy to use in clinical daily practice, and can be further adapted to future knowledge. The adoption of this system by the medical community would allow a uniform diagnosis leading to better injury management.



#14 Impact of Match Type and Match Halves on Referees' Physical Performance and Decision-Making Distance in Chinese Football Super League

Reference: Front Psychol. 2022 May 9;13:864957. doi: 10.3389/fpsyg.2022.864957. eCollection 2022.

Authors: Jinying Jiang, Huanmin Ge, Lida Du, Miguel-Angel Gomez, Bingnan Gong, Yixiong Cui

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Summary: The purpose of this study was to explore how Chinese Football Super League (CSL) referees' physical performance and decision-making distance varied according to match type and match halves. Data from 107 matches played by top-4 ranked and bottom-4 ranked teams during 2018-2019 CSL seasons were collected. Level of matches was classified into three groups: (a) upper-ranked (top-4) teams against top-4 teams, (b) top-4 teams against lower-ranked teams (bottom-4), and (c) bottom-4 teams against bottom-4 teams. Two-way ANOVA and Scheirer-Ray-Hare test were used to examine the statistical differences of referees' physical and spatial related distance variables among different match levels and halves. The Euclidean distance to the ball at the following three variables were statistically different among three match types: clearance (p = 0.03, E2RER2 = 0.03), running with the ball (p = 0.01, E2RER2 = 0.04), and shot off target (p = 0.04, E2RER2 = 0.03). In addition, referees' distance to the ball at three events were statistically different between both match halves: pass (p < 0.001, r = 0.69), reception (p < 0.001, r = 0.76), and running with the ball (p < 0.001, r = 0.77). The total running distance was statistically different between both match halves (p = 0.001, d = 0.05). The findings indicated that although CSL referees showed little difference in physical performance when officiating matches of three competitive levels and two halves, distinct rhythms of competitions determined that they needed to adjust running strategies to maintain proper distance to the ball. This study implied that the CSL referees' match performance was affected by the teams' style of play and match status.



#15 Examining the Mental Health Status of Referees in the Turkish Professional Football League

Reference: Sci Med Footb. 2022 May 27. doi: 10.1080/24733938.2022.2084150. Online ahead of print.

Authors: Yavuz Lima, Sergen Devran, Nazlı Deniz Öz, Tom Webb, Bülent Bayraktar

Summary: The purpose of the study was to evaluate the mental health (MH) status of referees who officiate in the Turkish professional football leagues. An online survey was sent to all referees in the Turkish professional football leagues (n=630) incorporating standardized scales assessing depression, anxiety, and stress. A total of 433 referees participated in the study, yielding a response rate of 68.7%. Younger referees (18-27 years) reported higher depression (p=0.01), anxiety (p<0.01), and stress (p<0.01) scores than older (>38 years) refereees. Depression, anxiety, and stress scores of single referees were higher compared to married referees (all p<0.01). Lower-level referees reported higher depression (p<0.01), anxiety (p=0.01), and stress (p<0.01) scores than their higher-level counterparts. Higher depression, anxiety, and stress scores were also associated with less income, performance concerns, severe injury history, and inadequate social support. MH problems in referees were associated with a wide range of variables including younger age, being single, refereeing at lower-levels, performance concerns, and inadequate social support. In light of these results, MH assessments should be undertaken with referees to detect which officials are at greater risk of MH problems. Doing so will help to enable appropriate and timely MH interventions.



#16 Players with high physical fitness are at greater risk of injury in youth football

Reference: Scand J Med Sci Sports. 2022 May 27. doi: 10.1111/sms.14199. Online ahead of print.

Authors: Mari Leppänen, Aliisa Uotila, Kari Tokola, Hannele Forsman-Lampinen, Urho M Kujala, Jari Parkkari, Pekka Kannus, Kati Pasanen, Tommi Vasankari

Summary: The aim of this study was to investigate physical fitness, football-specific skills and their association with injury risk in youth football. Altogether 447 male and female players aged 9 to 14 years (median 12 years) participated in performance tests and prospective follow-up. The physical fitness tests included five-jump test for distance, 30-m sprint, football-specific figure of eight agility, countermovement jump, and Yo-Yo intermittent endurance test level 1. The football-specific skill tests included dribbling and passing tests. Injuries and exposure were registered during the 20-week follow-up. Our candidate risk factors were low/high level of physical fitness measured with a composite score of physical fitness tests and low/high level of football-specific skills measured with a composite score of dribbling and passing tests. Secondarily, we investigated performance in individual tests and their association with injury risk. During the follow-up, players reported 565 injuries (264 acute and 301 overuse injuries). High level of physical fitness was associated with increased rate of all injuries (age-, sex- and mean team exposure - adjusted IRR 1.28, 95% CI 1.04-1.58). The level of football-specific skills had no influence on the overall injury rate. Burden of overuse injuries, but not acute injuries was significantly higher in most fit players compared with the players in the reference group (IRR 2.09, 95 % CI 1.04-4.24). In conclusion, most fit players were at greater risk of sustaining injuries in youth competitive football.






Effects of Three Preseason Training Programs on Speed, COD, and Endurance in Recreationally Trained Soccer Players

Coaches must choose wisely between the most efficient methods to improve the physical fitness of players during the preseason. The study compared the effects of plyometric training (PT), sprint interval training (SIT), and small-sided games (SSGs) on the performance of recreationally trained soccer players.





Do elite soccer players cover less distance when their team spent more time in possession of the ball?

The purpose of this study was to examine the association between the time spent in possession by teams and the match-running performance in elite soccer matches.





Latest research in football - week 19 - 2022

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 How training loads in the preparation and competitive period affect the biochemical indicators of training stress in youth soccer players?

Reference: PeerJ. 2022 May 5;10:e13367.  doi: 10.7717/peerj.13367. eCollection 2022.

Authors: Marcin Andrzejewski, Marek Konefał, Tomasz Podgórski, Beata Pluta, Paweł Chmura, Jan Chmura, Jakub Marynowicz, Kamil Melka, Marius Brazaitis, Jakub Kryściak

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Summary: Physical fitness optimization and injury risk-reducing require extensive monitoring of training loads and athletes' fatigue status. This study aimed to investigate the effect of a 6-month training program on the training-related stress indicators (creatine kinase - CK; cortisol - COR; serotonin - SER; brain-derived neurotrophic factor - BDNF) in youth soccer players. Eighteen players (17.8 ± 0.9 years old, body height 181.6 ± 6.9 cm, training experience 9.7 ± 1.7 years) were blood-tested four times: at the start of the preparation period (T0), immediately following the preparation period (T1), mid-competitive period (T2), and at the end of the competitive period (T3). CK activity as well as concentrations of serum COR, SER and BDNF were determined. Training loads were recorded using a session rating of perceived exertion (sRPE). Statistical analyzes revealed significant effects for all biochemical parameters in relation to their time measurements (T0, T1, T2, T3). The statistical analyzes of sRPE and differences of biochemical parameters in their subsequent measurements (T0-T1, T1-T2, T2-T3) also demonstrated significant effects observed for all variables: sRPE (HKW = 13.189 (df = 2); p = 0.00), COR (HKW = 9.261 (df = 2); p = 0.01), CK (HKW = 12.492 (df = 2); p = 0.00), SER (HKW = 7.781 (df = 2); p = 0.02) and BDNF (HKW = 15.160 (df = 2); p < 0.001). In conclusion, it should be stated that the most demanding training loads applied in the preparation period (highest sRPE values) resulted in a significant increase in all analyzed biochemical training stress indicators. The reduction in the training loads during a competitive period and the addition of recovery training sessions resulted in a systematic decrease in the values of the measured biochemical indicators. The results of the study showed that both subjective and objective markers, including training loads, are useful in monitoring training stress in youth soccer players.



#2 Participation of Soccer Training Improves Lower Limb Coordination and Decreases Motor Lateralization

Reference: Biomed Res Int. 2022 Apr 30;2022:7525262. doi: 10.1155/2022/7525262. eCollection 2022.

Authors: Selcuk Akpinar

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Summary: Athletes, who display less lateralization, are considered to be more successful in their sports. Therefore, it is important to test the lateralization profiles of the athletes to determine future prospects. Soccer is one of the sports where lateralization plays an important role because performing the passes and kicks with either foot may increase the success rate. Improved lower limb coordination is also very essential to perform the soccer skills more efficiently. Thus, the purpose of this study was to investigate the motor lateralization profiles of youth soccer players and to compare the same lateralization to non-athletes. A total of 28 healthy youth (14 soccer players) aged between 14 and 16 years voluntarily participated in this study. All participants were right-footed and were asked to hit the targets with their either foot maintaining accuracy in a custom-made virtual reality interface. Final position error (FPE) and foot path deviation from linearity (FPDL) were calculated to test motor lateralization for each foot and group. Two-way Mixed Model ANOVA was conducted for each dependent variable. Results indicated significant differences for FPDL between groups, while there were no significant differences between groups and within feet for FPE. Nonathletes had significantly higher FPDL with their nondominant foot compared to their dominant foot, which was not observed among soccer players. Overall, nonathletes' movements were more curvature path compared to soccer players, thus, can be considered as less coordinated. As soccer players did not show a difference between their feet on FPDL and performed better than nonathletes, soccer participation can improve lower limb coordination as well as alter motor performance and lateralization.



#3 Physical characteristics of elite youth male football players aged 13-15 are based upon biological maturity

Reference: PeerJ. 2022 May 5;10:e13282.  doi: 10.7717/peerj.13282. eCollection 2022.

Authors: Shidong Yang, Haichun Chen

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Summary: Older and more mature football players have been reported to gain advantages in the selection process during adolescence. The aim of this study was to investigate the influence of skeletal age (SA) on the physical characteristics of elite male football players aged 13-15 years through a cross-sectional study. We enrolled 167 elite players aged 13-15 from three academic football schools in China, and measured height, body mass, thigh circumference, skinfold (triceps and calf), 10 m/30-m sprint, T-tests (left and right), 5 × 25-m repeated-sprint ability (5 × 25 RSA), standing long jump, and YoYo intermittent recovery test level 1 (YYIR1). Subjects were divided into early-, average-, and late-maturity levels according to their SA and chronological age (CA) based on the following criteria: SA-CA > +1 year, SA-CA = ±1 year, and SA-CA < -1 year, respectively. The differences in parameters among the groups were analyzed using one-way analysis of variance and Bonferroni's post-hoc test, with statistical significance set at p < 0.05. Relative to the late-maturing players, the early- and average-maturing players aged 13-15 years were taller, heavier, had a larger thigh circumference, and scored higher on the standing long jump, 30 m sprint, and 5 × 25-RSA (p < 0.05). The physical (except for body-fat percentage) and athletic characteristics of players aged 13-15 were not only significantly influenced by biological maturity, but also increased significantly with CA. The influence of biological maturity on height, 30-m sprints, and 5 × 25-m RSA diminished with age and exerted no significant effect on body-fat percentage and on YYIR1. Late-maturing players exhibited the greatest increase in physical (except for body-fat percentage) and athletic performance (except for the 10-m sprint) compared to players of early and/or average maturity. Although early-maturing players aged 13-15 possessed better anthropometric and physical performance than late- and average-maturing players, the growth and development of physical function of late- and average-maturing players was significantly greater, particularly with respect to height, sprint speed, and muscular power.



#4 Is there a relationship between in-season injury risk and Y balance or vertical jump in elite youth soccer players?

Reference: FASEB J. 2022 May;36 Suppl 1. doi: 10.1096/fasebj.2022.36.S1.L7500.

Authors: Kristin Haraldsdottir, Michael Baer, Stacey Brickson, Andrew Watson

Summary: Injuries are relatively common among elite youth soccer players, and time lost participating in sport due to injury can have detrimental psychological effects on players. The purpose of this study was to determine whether the Y Balance Test (YBT), or vertical jump can identify those players at risk of suffering injury. 41 female elite soccer players (age 12-17) performed YBT and vertical jump testing prior to the competitive season. Time-loss injuries during the following season were recorded. Injured and uninjured athletes were compared with respect to YBT composite scores (absolute and relative to leg length), asymmetry, and vertical jump. Logistic regressions were performed to examine the relationships between YBT, vertical jump, and injury risk. Twelve athletes (29%) suffered a time-loss injury during the season. Athletes who suffered an in-season injury did not differ from uninjured athletes with respect to age (14.9 +/- 1.6 v 15.3 +/- 1.4 years, respectively), years of experience (9.7 +/- 1.7 v 10.2 +/- 2.4 years, p=0.26), YBT composite scores (111 +/- 16 v 109 +/- 17 cm, p=0.99), YBT composite scores relative to leg length (1.29 +/- 0.2 v 1.27 +/- 0.26, p=0.85), the difference in centimeters between composite scores of each leg (7.9+/-8.4 v 4.6+/-3.8, p=0.09) or vertical jump (15.3±1.6 v 15.3±2.6 in, p=0.96). In-season injuries were not significantly associated with YBT composite scores (OR= 0.99 [95% CI = .95-1.04] ,p= 0.80), relative YBT composite scores (1.0 [.97-1.03], p=0.98) or vertical jump scores (0.98 [.72-1.33], p=.91). Although not reaching statistical significance, higher asymmetry in composite scores showed some evidence of an increased risk of subsequent injury (1.2 [0.97-1.42], p=0.10). The composite YBT score and vertical jump did not predict in-season injury incidence in this sample of elite female adolescent soccer players. Higher YBT asymmetry may be associated with an increased risk of in-season injury, although this study may have been limited by sample size to identify a statistically significant difference. Although the YBT is widely used as an injury risk screening tool, our findings suggest that it may not be a strong predictor of subsequent time-loss injuries in elite female adolescent soccer players.



#5 Traumatic rupture of the midportion of the interosseous membrane: a rare cause of acute lower leg pain in two soccer players kicked in the anterior shin

Reference: Skeletal Radiol. 2022 May 18. doi: 10.1007/s00256-022-04071-z. Online ahead of print.

Authors: Mark S Collins, Taylor J North, Jacob L Sellon

Summary: The interosseous membrane (IOM) of the leg is a component of the tibiofibular syndesmosis that serves an important role in stabilization, as well as transferring forces to the fibula during weight-bearing. We present two separate cases of acute traumatic rupture of the midportion of the interosseous membrane in high school soccer players with blunt trauma to the anterior shin with MRI and ultrasound confirmation.



#6 Serum neurofilament light in professional soccer players: goal on safety

Reference: Neurol Sci. 2022 May 18. doi: 10.1007/s10072-022-06109-5. Online ahead of print.

Authors: Claudio Cornali, Paolo Amaddeo, Alberto Benussi, Federica Perrone, Marta Manes, Roberta Zanardini, Luisa Benussi, Francesco Belotti, Gianandrea Bellini, Andrea Bruzzone, Marco Bruzzone, Daniela Morelli, Silvana Archetti, Nicola Latronico, Alessandro Padovani, Marco Maria Fontanella, Roberta Ghidoni, Barbara Borroni

Summary: Sports-related concussion (SRC) is a subset of mild traumatic brain injuries occurring in contact sports. Most people recover spontaneously, but in retired professional players, the risk for neurodegenerative diseases is increased. A biomarker, such as neurofilament light chains (NfL), would help to address this issue and demonstrate sports' safety. Assessing NfL in professional soccer players may be the best way to investigate if repetitive head-impact exposure in the typical lower and asymptomatic range is harmful. The aim was to evaluate whether the NfL in serum is a sensitive biomarker to detect mild brain injury in professional soccer players. Thirty-six soccer players belonging to a professional Italian team underwent serum NfL assessment using ultrasensitive single-molecule array technology. Sixteen healthy nonathletic controls were also enrolled. Differences between groups and changes over time, considering pre-season vs. season, were considered. Serum NfL concentrations were comparable in the soccer professional players (median [interquartile range], 6.44 pg/mL [4.60-8.27] and controls (6.50 pg/mL [5.26-7.04]), with a median difference of - 0.06 pg/mL (95% CI -1.36 to 1.18), p = 0.957. No significant differences according to players' role (goalkeeper, defender, midfielder or forward) or according to timing of sampling (pre-season vs. season) were found. These results suggest that professional soccer, even when played at the highest level of competition, may be considered safe. Future studies assessing serum NfL levels after soccer-related concussions should be carried out, to evaluate their usefulness as a return-to-play marker avoiding second impact syndrome.



#7 Patellar fracture among elite-level European soccer players: 4-year case-control cohort analysis of return to play, re-injury, and player performance

Reference: Phys Sportsmed. 2022 May 20;1-10. doi: 10.1080/00913847.2022.2077087. Online ahead of print.

Authors: Sumit Patel, Ophelie Lavoie-Gagne, Nabil Mehta, Ghassan Farah, Avinaash Korrapati, Brian Forsythe

Summary: There is a paucity of literature investigating the relationship between patellar fracture and player performance of professional soccer players following return to play (RTP). Our goal is to determine the rate of RTP, time to RTP, and effect on player performance following patellar fracture. Twenty-one elite-level European professional soccer players who sustained a patellar fracture between 1999 and 2018 were identified via a publicly accessible database. Athletes with patellar fracture were matched to controls by age, height, years played in the league, season of injury, and position. Change in performance metrics between one season prior to injury and the following four seasons after injury were compared. Players with patellar fracture were absent for a mean 207.95 ± 135.55 days and 16.81 ± 31.79 games. Fifteen (71%) players returned to play after injury with 67% returning within 1 season after injury. Injured players did not demonstrate significant change in performance metrics at any of the follow-up timepoints compared to control. Subgroup analysis showed that attackers recorded approximately 1200 fewer minutes played per season than pre-injury levels 2 seasons following injury, significantly fewer (p < 0.05) than the control cohort recording similar minutes per season throughout the study period. Midfielders and defenders demonstrated similar fluctuations in performance to the control cohort for both field time and performance metrics (p > 0.05). Seventy-one percent of players RTP after patellar fracture with an associated absence of 7 months and 17 missed games. Overall, injured players did not demonstrate a significant decline in performance as demonstrated by games played, total minutes played per season, minutes per game, assists, and goals 1 season after injury. Attackers played fewer minutes during the season of and 2 seasons after the initial injury.



#8 Fecal microbiota monitoring in elite soccer players along the 2019-2020 competitive season

Reference: Int J Sports Med. 2022 May 20. doi: 10.1055/a-1858-1810. 

Authors: Elisa Viciani, Monica Barone, Tindaro Bongiovanni, Sara Quercia, Roberta Di Gesu, Giulio Pasta, Paolo Manetti, F Marcello Iaia, Athos Trecroci, Simone Rampelli, Marco Candela, Elena Biagi, Andrea Castagnetti

Summary: Physical exercise affects the human gut microbiota that, in turn, influences athletes' performance. The current understanding of how the microbiota of professional athletes changes along with different phases of training is sparse. We aim to characterize the fecal microbiota in elite soccer players along with different phases of a competitive season using 16S rRNA gene sequencing. Fecal samples were collected after the summer off-season period, the pre-season retreat, the first half of the competitive season, and the 8 weeks COVID-19 lockdown that interrupted the season 2019-2020. According to our results, the gut microbiota of professional athletes changes along with the phases of the season, characterized by different training, diet, nutritional surveillance, and environment sharing. Pre-season retreat, during which nutritional surveillance and exercise intensity were at their peak, caused a decrease in bacterial groups related to unhealthy lifestyle and an increase in health-promoting symbionts. The competitive season and forced interruption affected other features of the athletes' microbiota, i.e. bacterial groups that respond to dietary fibers load and stress levels. Our longitudinal study, focusing on one of the most followed sports worldwide, provides baseline data for future comparisons and microbiome-targeting interventions aimed at developing personalized training and nutrition plans for performances maximization.



#9 Comparison of the Agonist/Antagonist Tensional Balance of the Knee between Two Isokinetic Positions: A Pilot Study on a Sample of High-Level Competitive Soccer Players

Reference: Int J Environ Res Public Health. 2022 Apr 28;19(9):5397. doi: 10.3390/ijerph19095397.

Authors: Jorge García-Pastor, Ildefonso Alvear-Ordenes, Diego Arias-Giráldez, María Mercedes Reguera-García, Beatriz Alonso-Cortés

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Summary: Isokinetic knee dynamometry evolves towards more precise techniques, such as the calculation of the functional ratio. This study evaluated the influence of an intermediate hip position called the unified reclined position (URP) compared to the classic sitting position, (CSP) on hamstring eccentric PT values (Hexc30) and conventional (Hcon60/Qcon60) and functional (Hexc30/Qcon60) ratios. Twenty Spanish high-level competitive soccer players (20.4 ± 4.44 years) were evaluated in CSP and in URP. The hip angle in URP (44°) was determined with a passive extensibility test (quadriceps and hamstrings), looking for an agonist/antagonist tension balance. The following were performed: three repetitions (60°/s) and five repetitions (240°/s) in concentric quadriceps and hamstrings mode; and three repetitions (30°/s) in concentric and eccentric for the hamstrings. At 30°/s, the CSP presents higher values of maximal eccentric hamstring strength than URP, (Dom + N-Dom leg (Nm): CSP = 148.3 ± 19.5 vs. URP 143.5 ± 23.2); p = 0.086 (n.s.). The conventional relationship did not show data justifying the preference for URP over CSP (p = 0.86 (n.s.)). However, although the functional index did not show significant values (p = 0.97 (n.s.), it did show a greater number of subjects with imbalances measured in URP (five in URP vs. two in CSP). An assessment angle of the hip closer to sports reality seems to favor the use of the URP as a complementary method to the CSP. These data stimulate new studies using URP together with the classic protocol.



#10 Correlation between the Positive Effect of Vitamin D Supplementation and Physical Performance in Young Male Soccer Players

Reference: Int J Environ Res Public Health. 2022 Apr 23;19(9):5138. doi: 10.3390/ijerph19095138.

Authors: Michał Brzeziański, Monika Migdalska-Sęk , Aleksandra Czechowska, Łukasz Radzimiński, Zbigniew Jastrzębski, Ewa Brzeziańska-Lasota, Ewa Sewerynek

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Summary: The aim of this study was to determine whether supplementation with vitamin D during eight weeks of high-intensity training influences muscle power and aerobic performance in young soccer players. A total of 25 athletes were divided into two groups: the supplemented group (GS; n = 12; vitamin D 20,000 IU, twice a week) and the non-supplemented group (GN; n = 13). A set of measurements, including sprint tests, explosive power test, maximal oxygen uptake (VO2max), and serum 25(OH)D concentration, were obtained before (T1) and after (T2) the intervention. A significant group x time interaction was found in the 25(OH)D serum levels (p = 0.002; ES = 0.36, large). A significant improvement in VO2max was found in the TG (p = 0.0004) and the GS (p = 0.031). Moreover, a positive correlation between 25(OH)D and VO2max (R = 0.4192, p = 0.0024) was calculated. The explosive power tests revealed insignificant time interactions in the average 10-jump height and average 10-jump power (p = 0.07, ES = 0.13; p = 0.10, ES = 0.11, respectively). A statistically insignificant trend was observed only in the group-by-time interaction for the sprint of 10 m (p = 0.05; ES = 0.15, large). The present study provides evidence that vitamin D supplementation has a positive but trivial impact on the explosive power and locomotor skills of young soccer players, but could significantly affect their aerobic performance.



#11 Effect of the COVID-19 Confinement Period on Selected Neuromuscular Performance Indicators in Young Male Soccer Players: Can the Maturation Process Counter the Negative Effect of Detraining?

Reference: Int J Environ Res Public Health. 2022 Apr 19;19(9):4935. doi: 10.3390/ijerph19094935.

Authors: Nikolaos D Asimakidis, Stylianos S Vasileiou, Athanasios A Dalamitros, Pantelis T Nikolaidis, Vasiliki Manou

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Summary: The COVID-19 outbreak has led to an unprecedented long-term cessation in athletes' training routines. This study examined the effect of a 32-week detraining period, caused by the COVID-19 pandemic lockdown, on selected neuromuscular performance indicators in 29 young male soccer players, assessed close to their adolescent growth spurt (age = 13.0 ± 0.8 years). Change of direction ability of both lower limbs (COD), linear sprint times (10 and 20 m), and vertical jump height (CMJ) was evaluated twice, once before the first national lockdown, and one week after the return to training activities. Paired-sample t-tests detected significant improvements in all three testing variables (COD: 2.82 ± 0.23 vs. 2.66 ± 0.22 s, p ≤ 0.005, 0.001, effect size [ES] = 0.91 to 1.05 for the right and left limb, respectively; 10 m: 2.12 ± 0.16 vs. 1.96 ± 0.15 s, p ≤ 0.001, effect size [ES] = 1.67, 20 m: 3.56 ± 0.3 vs. 3.42 ± 0.27 s, p ≤ 0.001, effect size [ES] = 1.02 and CMJ: 23.3 ± 7.5 vs. 24.5 ± 7.6 cm, p = 0.033, ES = 0.42). These results indicate that maturation-related adaptations can lead to enhanced change of direction, linear sprint, and vertical jump performance, even in the absence of exposure to any level of exercise. Soccer coaches and practitioners working with youth athletes should consider the stage of maturation when planning and implementing training programs aiming to enhance neuromuscular performance.



#12 Analysis of a double Poisson model for predicting football results in Euro 2020

Reference: PLoS One. 2022 May 19;17(5):e0268511. doi: 10.1371/journal.pone.0268511. eCollection 2022.

Authors: Matthew J Penn, Christl A Donnelly

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Summary: First developed in 1982, the double Poisson model, where goals scored by each team are assumed to be Poisson distributed with a mean depending on attacking and defensive strengths, remains a popular choice for predicting football scores, despite the multitude of newer methods that have been developed. This paper examines the pre-tournament predictions made using this model for the Euro 2020 football tournament. These predictions won the Royal Statistical Society's prediction competition, demonstrating that even this simple model can produce high-quality results. Moreover, the paper also presents a range of novel analytic results which exactly quantify the conditions for the existence and uniqueness of the solution to the equations for the model parameters. After deriving these results, it provides a novel examination of a potential problem with the model-the over-weighting of the results of weaker teams-and illustrates the effectiveness of ignoring results against the weakest opposition. It also compares the predictions with the actual results of Euro 2020, showing that they were extremely accurate in predicting the number of goals scored. Finally, it considers the choice of start date for the dataset, and illustrates that the choice made by the authors (which was to start the dataset just after the previous major international tournament) was close to optimal, at least in this case. The findings of this study give a better understanding of the mathematical behaviour of the double Poisson model and provide evidence for its effectiveness as a match prediction tool.



#13 Comparison of the risk of cardiovascular diseases, stroke, and diabetes among the selected group of football referees and the group of general population men from Northern Poland - a pilot study

Reference: Eur Rev Med Pharmacol Sci. 2022 May;26(9):3151-3160. doi: 10.26355/eurrev_202205_28732.

Authors: J Wesołowska, A Jurczak, S Wieder-Huszla, K Jarosz, A Jurewicz, M Marchlewicz

Summary: We aimed at comparing the total body fat and visceral adipose tissue content in football referees and in the control group of general population men. An assessment of compliance with health promoting behavior in both groups was carried out. This study, conducted in Northern Poland, involved 112 men. The study group comprised 56 men, football referees. The control group consisted of randomly chosen general population men, not engaged in any sport activities. Assessment of compliance with health promoting behavior among football referees and general population men was based on ultrasound imaging using the BodyMetrix System device (IntelaMetrix, Poland). The study employed a survey questionnaire comprised of the original section and two standardized questionnaires: the Health Behavior Inventory (HBI) and the NEO-Five Factor Inventory (NEO-FFI): the Health Behavior Inventory (HBI) and the NEO-Five Factor Inventory (NEO-FFI). The visceral adipose tissue content in the study group (football referees) was found to be low, and the excess of body fat was 0-0.25 kg. In the control group, the trunk fat volume was found to be higher by more than 8% as compared with the study group. Also, the level of visceral adipose tissue was high, and the excess of body fat was 0-4 kg. Thanks to properly planned and systematically continued physical activity, despite non-compliance with certain pro-health principles (increased sweet supply and consumption of alcoholic beverages), football referees are characterized by the correct body fat volume and low level of visceral adipose tissue. The parameters were found to be markedly higher in the control group of randomly selected men from the general population. The risk of diabetes, stroke, and cardiovascular diseases among football referees was found to be very low.



#14 A Systematic Review of Head Impacts and Acceleration Associated with Soccer

Reference: Int J Environ Res Public Health. 2022 May 1;19(9):5488. doi: 10.3390/ijerph19095488.

Authors: Ioannis Basinas, Damien M McElvenny, Neil Pearce, Valentina Gallo, John W Cherrie

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Summary: Epidemiological studies of the neurological health of former professional soccer players are being undertaken to identify whether heading the ball is a risk factor for disease or premature death. A quantitative estimate of exposure to repeated sub-concussive head impacts would provide an opportunity to investigate possible exposure-response relationships. However, it is unclear how to formulate an appropriate exposure metric within the context of epidemiological studies. We have carried out a systematic review of the scientific literature to identify the factors that determine the magnitude of head impact acceleration during experiments and from observations during playing or training for soccer, up to the end of November 2021. Data were extracted from 33 experimental and 27 observational studies from male and female amateur players including both adults and children. There was a high correlation between peak linear and angular accelerations in the observational studies (p &lt; 0.001) although the correlation was lower for the experimental data. We chose to rely on an analysis of maximum or peak linear acceleration for this review. Differences in measurement methodology were identified as important determinants of measured acceleration, and we concluded that only data from accelerometers fixed to the head provided reliable information about the magnitude of head acceleration from soccer-related impacts. Exposures differed between men and women and between children and adults, with women on average experiencing higher acceleration but less frequent impacts. Playing position appears to have some influence on the number of heading impacts but less so on the magnitude of the head acceleration. Head-to-head collisions result in high levels of exposure and thus probably risk causing a concussion. We concluded, in the absence of evidence to the contrary, that estimates of the cumulative number of heading impacts over a playing career should be used as the main exposure metric in epidemiological studies of professional players.



#15 Nature Scenes Counter Mental Fatigue-Induced Performance Decrements in Soccer Decision-Making

Reference: Front Psychol. 2022 Apr 29;13:877844. doi: 10.3389/fpsyg.2022.877844. eCollection 2022.

Authors: He Sun, Kim Geok Soh, Xiaowei Xu

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Summary: It has been well investigated that nature exposure intervention can restore directed attention and improve subsequent cognitive performance. The impairment of decision-making skills in mentally fatigued soccer players was attributed to the inability of attention allocation. However, nature exposure as the potential intervention to counter mental fatigue and improve the subsequent decision-making skill in soccer players has never been investigated. This study aimed to evaluate the effects of nature exposure intervention on decision-making skills among mentally fatigued university soccer players. Moreover, different durations of nature exposure were also evaluated. A random control between-subject design was adopted. Players were randomly assigned into six groups with three different durations of the experimental group compared with the corresponding control group (4.17 min: Exp 1 vs. Con 1; 8.33 min: Exp 2 vs. Con 2; and 12.50 min: Exp 3 vs. Con 3). All players were first mentally fatigued by performing a 45-min Stroop task; then, they viewed virtual photos of natural or urban scenes; and finally, they performed a soccer decision-making task. The subjective ratings of mental fatigue were significantly higher following the Stroop task. Only Exp 3 (12.50 min viewing natural scenes) significantly improved decision-making reaction time compared with Con 3 (p = 0.09). Moreover, the accuracy slightly increased in Exp 3 after the intervention. In line with attention restoration theory, nature exposure significantly improved decision-making skills in mentally fatigue university players. However, the duration must be 12.50 min for each stimulus to stay longer to attract involuntary attention.



#16 Peak instantaneous PlayerLoad metrics highlight movement strategy deficits in professional male soccer players

Reference: Res Sports Med. 2022 May 20;1-11. doi: 10.1080/15438627.2022.2079985. Online ahead of print.

Authors: Andy Mitchell, Matt Greig

Summary: The aim was to investigate the influence of task, limb dominance and previous injury on single leg hop task performance and loading response, 25 professional male soccer players completed anterior, medial and lateral hop tests with an accelerometer at mid-calf. Performance outcome was defined as hop distance with loading response defined as the magnitude of, and time to peak instantaneous planar PlayerLoad. The performance was sensitive to task and previous injury (P < 0.001) but not limb dominance, with no evidence of bilateral asymmetry (P = 0.668). Despite impaired performance, previously injured players did not exhibit lower peak instantaneous PlayerLoad after impact in any plane (P ≥ 0.110). There was however a significantly (P = 0.001) longer time to peak medio-lateral loading after impact in previously injured players' affected limb. This observation was exacerbated when the injury was to the non-dominant limb (P = 0.041). Lower-limb accelerometry enhances understanding of movement strategy beyond task outcome, with practical implications in player screening and objective rehabilitation.



#17 Growth, body composition and bone mineral density among pubertal male athletes: intra-individual 12-month changes and comparisons between soccer players and swimmers

Reference: BMC Pediatr. 2022 May 13;22(1):275. doi: 10.1186/s12887-022-03321-2.

Authors: Daniela C Costa, João Valente-Dos-Santos, Paulo Sousa-E-Silva, Diogo V Martinho, João P Duarte, Oscar M Tavares, Joaquim M Castanheira, Tomás G Oliveira, Sandra Abreu, Neiva Leite, Ricardo R Agostinete, Rômulo A Fernandes, Daniel Courteix, Manuel J Coelho-E-Silva

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Summary: Puberty is a period of intense changes in human body and, additionally, participation in sports is viewed as prominent form of physical activity among male adolescent athletes. The current study was aimed to examine the intra-individual changes in body composition and bone tissue during years of maximal growth and the effect of 12-month participation in sports contrasting in mechanical impact. The sample included 40 male adolescent athletes (soccer: n = 20; swimming: n = 20) aged 12.57 ± 0.37 years who were followed for 12 months. Stature and body mass were measured, bone mineral content (BMC), areal bone mineral density (aBMD), lean soft and fat tissues assessed using DXA. Food intake was estimated using a questionnaires and training sessions individually monitored. Repeated measures ANOVA tested the differences between sports and 12-month intra-individual variation (time moments: TM1, TM2). The analyses on aBMD for total body and total body less head were repeated controlling for variation in stature at baseline. Soccer players completed 63 ± 31 sessions (95 ± 47 h). Respective values for swimmers were 248 ± 28 sessions and 390 ± 56 h. In general, the analysis of aBMD as dependent variable evidenced significant effect of sport-associated variation (F = 5.254, p < 0.01; η2 = 0.35) and 12-month increments, particularly at lower limbs (F = 97.238, p < 0.01; η2 = 0.85). Respective mean values for aBMD were SCCTM1 = 0.885, SWMTM1 = 0.847, SCCTM2 = 0.939, SWMTM2 = 0.880. Regarding the lean soft tissue, the magnitude of effects was very large for intra-individual variation (F = 223.043, p < 0.01; η2 = 0.92) and moderate between sports (F = 7.850, p < 0.01; η2 = 0.41): SCCTM1 = 30.6 kg, SWMTM1 = 34.9 kg, SCCTM2 = 35.8 kg, SWMTM2 = 40.5 kg). Finally, d-cohen values reporting percentage of intra-individual changes in aBMD between soccer players ad swimmers were large for the trochanter (d = 1.2; annual increments: SCC = 8.1%, SWM = 3.6%). Puberty appeared as a period of significant intra-individual changes in lean soft tissue and bone mineral density. With increasing accumulated training experience, mean difference between sports contrasting in mechanical impact tended to me more pronounced in particular at the lower limbs.



#18 Muscle Glycogen in Elite Soccer - A Perspective on the Implication for Performance, Fatigue, and Recovery

Reference: Front Sports Act Living. 2022 Apr 25;4:876534.  doi: 10.3389/fspor.2022.876534. eCollection 2022.

Authors: Magni Mohr, Jeppe F Vigh-Larsen, Peter Krustrup

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Summary: Based on extrapolation of current trends in modern soccer, physiological loading has increased markedly, and the game will continue to become even more demanding in the future, which will exacerbate fatigue at the end of a game and between games. Soccer is a glycogen consuming activity due to its high-intensity intermittent nature, and muscle glycogen is a key factor associated with fatigue late in a game, as well as in determining recovery after a game or an intense training session. Low glycogen in individual muscle fibers and subcellular compartments in the muscle cell is likely to negatively affect several essential steps in the excitation-contraction coupling such as action potential propagation, calcium handling and cross-bridge cycling through reductions in muscle ATP which are suggested sites of muscle function impairment inducing muscle fatigue. Recovery of physical performance and muscle glycogen after a soccer game is a slow process, which challenges the reality in modern elite soccer with increased game and training frequency and physiological loading. We suggest a markedly higher prioritization of fitness training modalities, nutritional approaches and general recovery strategies that optimizes muscle glycogen storage prior to games and training sessions. Also, the soccer community including the governing bodies of the sport must acknowledge and plan according to the high and increasing demands of the modern game, as well as the consequences this has on fatigue and recovery. These aspects are paramount to consider in the planning of training and games, as well as in the process of structuring soccer tournaments and developing competitive regulations in the future to optimize performance and player health.



#19 The influence of maturation, fitness, and hormonal indices on minutes played in elite youth soccer players: a cross-sectional study

Reference: BMC Sports Sci Med Rehabil. 2022 May 17;14(1):89. doi: 10.1186/s13102-022-00480-8.

Authors: Ebrahim Eskandarifard, Hadi Nobari, Filipe Manuel Clemente, Rui Silva, Cain C T Clark, Hugo Sarmento, António José Figueiredo

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Summary: The main purpose of this study was to investigate the relationships between minutes played (MP) with maturity status, fitness, and hormonal levels, and to quantify their influence on minutes played. Twenty-four elite youth soccer players under-16 years participated in this study, over a full-season period. Anthropometric measures, maturity status, hormonal and physical fitness levels were collected. Participants were monitored during the season. After the end-season, players were assessed in 6 different tests over a four-day period. The maximum oxygen consumption (V̇O2max) was strongly correlated with MP (r = 0.75), maturity offset (r = 0.52), and countermovement jump (r = 0.53). Multiple linear regression explained 76% of MP (F (8, 15) = 6.05, p = 0.001), with an R2 of 0.76. Moreover, Growth hormone (GH) and V̇O2max. were the most influential factors in MP (F (2, 21) = 17.92, p ≤ 0.001), with an R2 of 0.63. High levels of GH and V̇O2max have a preponderant role in MP by elite youth soccer players, it appears to be more pragmatic to consider other contextual dimensions, as they can impact selection for competition and minutes of participation in a match.






Effects of mental fatigue on soccer-specific Performance in young players

The aim was to investigate the effects of mental fatigue on soccer-specific physical and technical performance in young players.





The Relationship between Different Large-Sided Games and Official Matches on Professional Football Players’ Locomotor Intensity

The aim of this study was: (1) to investigate the locomotor demands imposed by large-sided games (LSGs) vs  official matches; and (2) to compare the effect of different pitch sizes’ LSG conditions in the locomotor demands.





Latest research in football - week 18 - 2022

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 Analysis of team success based on match technical and running performance in a professional soccer league

Reference: BMC Sports Sci Med Rehabil. 2022 May 5;14(1):82. doi: 10.1186/s13102-022-00473-7.

Authors: Marcin Andrzejewski, José M Oliva-Lozano, Paweł Chmura, Jan Chmura, Sławomir Czarniecki, Edward Kowalczuk, Andrzej Rokita, José M Muyor, Marek Konefał

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Summary: The aims of this study were to (1) determine the match technical and running performance required by different teams based on their final ranking position in a professional soccer league; and (2) analyze the correlation between teams' success at the end of the season and variables related to match technical and running performance. These performance data were collected during a total of 612 matches in the German Bundesliga. The final ranking position and the total of points obtained by each team at the end of the season were registered for the analysis of the correlation between team success and performance. The main findings were that there was a significant interaction (p < 0.05) between the ranking position, and both match technical and running performance. However, goals scored, saved shots on goal by the goalkeeper, assists, allowed shots on goal, goals conceded, ball possession ratio and successful passes from open play were the variables with the strongest correlation (r > 0.7; p ≤ 0.01) with the total of points obtained at the end of the season. Strength and conditioning coaches may consider these results to develop adequate training strategies, which may not only optimize performance but also reduce the injury risk.



#2 Change of Direction Speed in Youth Male Soccer Players: The Predictive Value of Anthropometrics and Biological Maturity

Reference: Pediatr Exerc Sci. 2022 May 5;1-7. doi: 10.1123/pes.2021-0178. Online ahead of print.

Authors: Yassine Negra, Senda Sammoud, Alan M Nevill, Helmi Chaabene

Summary: This study aimed to develop the optimal allometric body size/shape and a biological maturity model that predicted the change of direction (CoD) mean speed performance in youth male soccer players. One-hundred and fifteen youth soccer players (age: 12.4 [1.3] y) participated in this study. The 505 test was used to assess CoD mean speed performance. Anthropometric measurements comprised body height (cm), sitting height (cm), body mass (kg), fat mass (kg), lower limb length (cm), thigh length (cm), leg length (cm), foot length (cm), thigh girth (cm), and calf girth (cm). The maturity status was determined based on the maturity offset method. To identify size/shape and maturity characteristics associated with CoD speed performance, we computed a multiplicative allometric log-linear regression model, which was refined using backward elimination. The multiplicative allometric model exploring the association between 505 CoD mean speed performance and the different anthropometric characteristics in youth soccer players estimated that fat mass (P < .001), sitting height (P = .02), and maturity offset (P = .004) are the key predictors. More specifically, youths who are more mature and have a lower fat mass and a shorter trunk length, are likely to achieve a better CoD mean speed performance. These findings highlight the relevance of considering anthropometric and maturity characteristics in youth soccer players to support talent identification.



#3 Effects of Vest and Sled Resisted Sprint Training on Sprint Performance in Young Soccer Players: A Systematic Review and Meta-analysis

Reference: J Strength Cond Res. 2022 Apr 29. doi: 10.1519/JSC.0000000000004255. Online ahead of print.

Authors: Luis Miguel Fernández-Galván, Arturo Casado, Amador García-Ramos, Guy Gregory Haff

Summary: The aim of the meta-analysis was to determine the effect of resisted sprint training (RST) on sprint performance in young (<20 years) soccer players and to analyze whether the training equipment (sled or vest) and magnitude of the resistive load (above or below 20% of body mass [BM]) influences the long-term adaptations in sprint performance. Resisted sprint training reduced the acceleration phase time [standardized mean difference (SMD) = -0.41], with greater reduction in sprint time occurring in response to applying resistance with a vest (SMD = -0.70) when compared with a sled (SMD = -0.27). Similar reductions were determined for resistive loads <20% (SMD = -0.55) and ≥20% of BM (SMD = -0.31). Full sprint time showed a small reduction after RST (SMD = -0.36), regardless of the training equipment (sled: SMD = -0.44; vest: SMD = -0.26) and resistive load (<20% of BM: SMD = -0.40 ≥ 20% of BM: SMD = -0.21). There was a small and nonsignificant reduction in the maximum-velocity phase after RST (SMD = -0.25), which was comparable when the training was performed with vest (SMD = -0.34) or sled (SMD = -0.22). No significant differences in the changes of the acceleration phase time (SMD = 0.05) or full sprint time (SMD = 0.08) were observed between the experimental (sled or vest RST) and control groups (only soccer or unresisted sprint training). In conclusion, RST is effective to improve sprint performance in young soccer players, but the improvements are not superior to unresisted sprint training.



#4 Evaluation of Visual Skills in Soccer Referees and Assistant Referees

Reference: Med J Islam Repub Iran. 2021 Dec 19;35:169. doi: 10.47176/mjiri.35.169. eCollection 2021.

Authors: Amir Houshang Behesht Nejad, Tohid Seif Barghi, Bahar Hassanmirzaei, Leila Ghanbari, Homa Naderifar

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Summary: As a soccer referee or an assistant referee, having perfect visual skills is mandatory, which will help make quick and accurate decisions in the field of the play and during matches; however, this skill is not well studied among referrers. This study aimed to assess the visual skills of referees and assistant referees. Men's professional referees and assistant referees working for the Iran football federation were investigated in 2019. The visual skill investigation consists of the evaluation of static visual acuity, color vision, stereoacuity, intraocular pressure, confrontation test, and eye anatomical assessment with slit lamp. The statistical analysis was performed using the SPSS software Version 18. In this study, 159 men's professional referees and assistant referees with a mean age of 35.52±5.39 were selected. The results of this study showed that 1.88% of the referees and assistant referees had color blindness dyschromatopsia) and 3.14% of them needed more follow-up examinations. The mean spherical equivalent of examined eyes was -0.42D in the right eye and -0.16 D in the left eye.  Our results showed that referees and assistant referees both had some kind of visual skill deficiencies. As visual skills are among the fundamental skills for success in referees in dynamic sports such as soccer, all of them must undergo visual skill assessments during the precompetition period to avoid any errors in judgment due to visual disturbances.



#5 Analysis of professional soccer players in competitive match play based on submaximum intensity periods

Reference: PeerJ. 2022 Apr 26;10:e13309. doi: 10.7717/peerj.13309. eCollection 2022.

Authors: Eduardo Caro, Miguel Ángel Campos-Vázquez, Manuel Lapuente-Sagarra, Toni Caparrós

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Summary: The main objective of this study is to analyse sub-maximum intensity periods (SubMIP's) manifested by professional soccer players during official matches (number of events and time spent in each event), according to the player position, match halve and match, and also to group the players according to their SubMip values during the competition. We collected a total of 247 individual records of 14 players using Global Positioning System (GPS) during 15 official league matches (Azerbaijan Premier League 2019-2020). We calculated both the number of SubMIPs events and the time each player spent in the SubMIPs zone (threshold of 85% MIP). We analysed the possible independence of the variables with the Kruskal-Wallis test and the possible specific relationships between the groups using a post-hoc analysis with Dunn's test. In order to explore the possible distribution of physical demands in homogeneous groups, a cluster analysis was performed. The statistical analysis showed significant differences between the individual variables in the number of events and in the time spent by the player above the threshold in distance covered at speed >19.8 km/h (HSR), distance covered at speed >25.2 km/h (Sprint), acceleration density (AccDens), mean metabolic power (MetPow), metres per minute (Mmin) and high metabolic load distance >25.5 W/kg (HMLD). Differences were also found according to the playing position in MetPow, Mmin and between halves in AccDens, MetPow, Mmin. In the clustering based on the time spent by the player in SubMIPs, three main groups were described: (1) the centroid was located in lower values in each of the variables; (2) there were an accentuation of the AccDens variable; (3) all the variables, except AccDens, were accentuated. The main differences with regard to SubMIPs were related to the player's individual physical performance and not to position. However, the player's position could act as an attractor and show significant differences during matches.



#6 Soccer, safety and science: why evidence is key

Reference: Policy Brief (Inst Secur Stud). 2021 Mar;2021:159. Epub 2021 Mar 26.

Authors: Christina Laurenzi, Mark Tomlinson, Zwelibanzi Skiti, Mary Jane Rotheram-Borus

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Summary: Sports-based violence prevention programmes have broad appeal, including among police, policy makers and politicians. This policy brief presents a case study of the Eyethu Soccer League, a behavioural intervention that was carefully planned, implemented and evaluated - and yet did not achieve its aims. Findings caution against 'easy wins' and suggest that short-term skills-building programmes may struggle to solve structural challenges.



#7 In National Collegiate Athletic Association Men's and Women's Soccer Athletes There Is a Low Rate of Lumbar Spine Injury, Women Suffer More Recurrent Injuries than Men, and Most Injuries Occur in the Preseason

Reference: Arthrosc Sports Med Rehabil. 2022 Jan 29;4(2):e705-e711. doi: 10.1016/j.asmr.2021.12.015. eCollection 2022 Apr.

Authors: Nicolas P Kuttner, Aaron C Llanes, Sailesh V Tummala, Joseph C Brinkman, Kade S McQuivey, Jeffrey D Hassebrock, Justin L Makovicka, Anikar Chhabra

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Summary: The purpose was to use the National Collegiate Athletic Association Injury Surveillance Program (NCAA-ISP) from the 2009-2010 through the 2014-2015 seasons to report lumbar spine injury rates, characteristics, and time lost from sport in soccer players. Characteristics of lumbar spine injuries by season, competition/practice, and time lost from sport were determined using the NCAA-ISP database. Rates of injury were calculated as the number of injuries divided by the number of athlete exposures (AEs). AEs are any athlete participation in a competition or practice. Incidence rate ratios (IRRs) were calculated to compare rates between event types and time of season. Injury proportion ratios (IPRs) were used to evaluate differences in injury rates between men and women. The NCAA-ISP estimated 4,464 LSIs over 5 years. The rate of LSI in men was 2.1/10,000 AEs and 3.0/10,000 AEs in women. Women were 1.43 times more likely to suffer an LSI compared to men. Women were 2.15 times as likely to suffer an LSI in competition compared to in practice while men were 1.10 times as likely. Women were 2.15 times as likely to be injured in the preseason compared to the regular season, while men were 3.76 times as likely. Non-contact injuries were the most common cause of lumbar spine injuries (LSIs) in men (35%); however, contact injuries were more common in women (33%). Most athletes both male (57%) and female (59%) returned to play within 24 hours. This study provides information on the characteristics of LSIs in NCAA soccer. The overall injury rate to the lumbar spine is relatively low. Injury rates are highest in the preseason and in competition. Women suffer from more recurrent LSI's than men, and men acquired more injuries through non-contact mechanisms. More than one-half of athletes returned to sport within 24 hours.



#8 Chronic Effects of Heavy Load Activity Performed Before Resistance Training Sessions on the Physical Performance of Youth Soccer Players

Reference: Int J Exerc Sci. 2022 Feb 1;14(6):1421-1434. eCollection 2021.

Authors: Guilherme Borsetti Businari, Julio Benvenutti Bueno de Camargo, Paulo Henrique Barbosa, Felipe Alves Brigatto, Marcelo Saldanha Aoki, Tiago Volpi Braz, Charles Ricardo Lopes

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Summary: The adoption of resistance training (RT) programs has been shown to positively influence sports performance-related parameters. However, the chronic effects of maximal strength protocols on the performance of soccer players are not completely investigated. The aim of this study was to evaluate the effects of performing two repetition maximum (2RM) before a resistance training session on the physical performance of youth soccer players. Seventeen players (under-20 category) were allocated in one of the following groups: 2RM + resistance training group (2RM + RT, n = 8) and resistance training group (RTG, n = 9). Both groups performed the same RT protocol during experimental weeks. However, the 2RM + RT performed 1 set of 2RM for 4 exercises, previously to RT protocol. Pre and post intervention period, one repetition maximum of the back squat exercise (1RMSQUAT), sprint time (15m-sprint test), countermovement jump (CMJ), repeated sprint ability (RSABEST and RSAMEAN), and yo-yo intermittent recovery test level-2 (YYIRT2) were assessed. Total load lifted (TLL) during the experimental weeks was also collected. Significant increases in 1RMSQUAT (2RM + RT: +45.1%, d = 4.40; RTG: +32.3%, d = 1.84), 15m sprint (2RM + RT: -9.0%, d = 7.9; RTG: -8.8%%, d = 3.2), CMJ (2RM + RT: +2.3%, d = 0.17; RTG: +0.8%, d = 0.07), RSABEST (2RM + RT: -2.4%, d = 0.6; RTG: -2.3%, d = 1.04), RSAMEAN (2RM + RT: -2.9%, d = 1.33; RTG: -3.4%, d = 1.78), YYIRT2 (2RM + RT: +12.0%, d = 0.82; RTG: +12.1%, d = 0.63) (all p < 0,05) were observed for both groups on pre to post-intervention periods, with no significant difference between groups. Therefore, the 2RM + RT protocol did not promote additional increase on performance of young soccer players.



#9 High-Risk Environmental Conditions Attenuates Performance Efficiency Index in NCAA DI Female Soccer Players

Reference: Int J Exerc Sci. 2022 Mar 1;15(6):442-454. eCollection 2022.

Authors: Maxine Furtado Mesa, Jeffrey R Stout, David H Fukuda, Michael J Redd, Adam J Wells

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Summary: The purpose of this study was to evaluate the effects of environmental conditions on running performance and performance efficiency index (Effindex). Performance data recorded using Polar Team Pro sensors from eight collegiate female soccer players in nine matches were analyzed during the 2019 competitive season. Effindex and running performance, including total distance covered (TDREL) and distance covered in five speed thresholds relative to minutes played, were examined for indications of fatigue with respect to environmental conditions, including ambient temperature and relative humidity. Matches were separated into three groups based on environmental conditions: Low-Risk (n = 2 matches), Moderate-Risk (n = 3 matches), or High-Risk (n = 4 matches). Speed thresholds were grouped as follows: walking (WALKREL), jogging (JOGREL), low-speed running (LSRREL), high-speed running (HSRREL), and sprinting (SPRINTREL). A significant effect was observed for TDREL in all environmental conditions (η2 = 0.614). TDREL was significantly lower in the High-Risk (p = 0.002; 95.32 ± 12.04 m/min) and Moderate-Risk conditions (p = 0.004; 94.85 ± 9.94 m/min) when compared to Low-Risk (105.61 ± 9.95 m/min). WALKREL (p = 0.005), JOGREL (p = 0.005) LSRREL (p = 0.001), HSRREL (p = 0.035), SPRINTREL (p = 0.017), and Effindex (p = 0.0004) were significantly greater in Low-Risk conditions when compared to Moderate-Risk conditions. WALKREL (p = 0.005), HSRREL (p = 0.029), SPRINTREL (p = 0.005), and Effindex (p = 0.0004) were significantly greater in Low-Risk conditions when compared to High-Risk conditions. High-Risk environmental conditions may result in adverse performance in female collegiate soccer players.



#10 The Development of Executive Functions in High-Level Female Soccer Players

Reference: Percept Mot Skills. 2022 May 6;315125221096989. doi: 10.1177/00315125221096989.

Authors: Adam Beavan, Jan Spielmann, Paul Ehmann, Jan Mayer

Summary: Executive functions (EFs) are higher-level cognitive functions that help keep an individual's goal-oriented thoughts and actions aligned. While many studies have shown the importance of EFs in sport, a limitation in this literature is that female participants have been underrepresented. In this mixed-longitudinal study, we examined the development of EFs in a cohort of high performing female athletes. We collected data over five seasons in a large sample of 175 female soccer players (aged 12-29 years old) from the U14 - senior age groups of a professional German soccer club. Players undertook a large battery of cognitive tasks aimed at measuring higher-level cognitive functioning: a sustained attention task, a stop-signal task, a Go-No-go test, an N-Back Test, and both a 180°- and 360°-multiple-object tracking task. We used linear and non-linear mixed effect regressions to examine the relationship between age and EFs. Second order polynomial curves explained many of these relationships between age and EFs compared to their linear relationships. Negatively accelerated curves reveal that these players' cognitive abilities mainly developed before players reached early adulthood, with a performance plateau evident at around 21 years of age. Age explained low to moderate proportions of the variance in EFs (<1-50%), while cognitive development across playing positions was not a strong contributor to this variance (M = 2.1, SD = 2.1%). We concluded that age has a negatively accelerated relationship with EFs in female soccer players that does not differ between playing positions. These data support the idea that athletes require only a reasonable level of EF ability to perform at the highest level of their sport. Our research raises new questions regarding the validity of current EF measurement methods for inferring information about in-game use of these cognitive abilities.



#11 Preseason multiple biomechanics testing and dimension reduction for injury risk surveillance in elite female soccer athletes: short-communication

Reference: Sci Med Footb. 2022 May 6. doi: 10.1080/24733938.2022.2075558. Online ahead of print.

Authors: Carlos De la Fuente, Rony Silvestre, Roberto Yañez, Matias Roby, Macarena Soldán, Wilson Ferrada, Felipe P Carpes

Summary: Injury risk is regularly assessed during the preseason in susceptible populations like female soccer players. However, multiple outcomes (high-dimensional dataset) derived from multiple testing may make pattern recognition difficult. Thus, dimension reduction and clustering may be useful for improving injury surveillance when results of multiple assessments tools are available. Thus, we determined the influence of dimension reduction for pattern recognition followed by clustering on multiple biomechanical injury markers in elite female soccer players during preseason. We introduce the use of dimension reduction through linear principal component analysis (PCA), non-linear kernel principal component analysis (k-PCA), t-distributed stochastic neighbor embedding (t-sne), and uniform manifold approximation and projection (umap) for injury markers via grid search. Muscle strength, muscle function, jump technique and power, balance, muscle stiffness, exercise tolerance, and running performance were assessed in an elite female soccer team (n=21) prior to the competitive season. As a result, umap facilitated the injury pattern recognition compared to PCA, k-PCA, and t-sne. One of three patterns was related to a team subgroup with acceptable muscle conditions. In contrast, the other two patterns showed higher injury risk profiles. For our dataset, umap improved injury surveillance through multiple testing characteristics. Dimension reduction and clustering techniques present as useful strategies to analyze subgroups of female soccer players who have different risk profiles for injury.



#12 Staying in or Dropping Out of Elite Women's Football-Factors of Importance

Reference: Front Sports Act Living. 2022 Apr 14;4:856538. doi: 10.3389/fspor.2022.856538. eCollection 2022.

Authors: Ingrid Amalie Hoftun Bjerksæter, Pål Arild Lagestad

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Summary: The average age of elite women footballers in Norway is 22.7 years, significantly lower than that of elite male footballers in Norway (26.5). This study examines the factors leading to elite female footballers ending their careers at a relatively young age, and those factors influencing other female elite players to continue. Semi-structured interviews were conducted with five female elite players who had ended their career at the age of 19-24, and four who were still active (age 26-31). Based on the age of the informants who had ended their career and the informants who were still active, this study defines "young age" as <25years of age. The female elite players experiences were analyzed and discussed in relation to earlier research. The results of the study show that the same factors affecting the early end of a career, also had an impact on continuing the career in the Norwegian top league, beyond the average age. A low level of internal and external motivation, poor financial circumstances, high stress load, long injury breaks, lack of playing time and other priorities, are all factors leading elite players to end their football careers at a young age. These factors are increasingly being addressed in relation to still active elite players, and this has an impact on the length of their playing career. Like earlier research, this study indicates that the emergence of Norwegian women's football in recent years has helped to improve conditions for being female elite players in the professional leagues in Norway.



#13 Youth International Experience Is a Limited Predictor of Senior Success in Football: The Relationship Between U17, U19, and U21 Experience and Senior Elite Participation Across Nations and Playing Positions

Reference: Front Sports Act Living. 2022 Apr 13;4:875530. doi: 10.3389/fspor.2022.875530. eCollection 2022.

Authors: Henrik Herrebrøden, Christian Thue Bjørndal

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Summary: Athlete participation in youth international competitions is often regarded as crucial to the attainment of future success. However, the link between participation and performance in sports at youth levels and senior levels is unclear at best. To understand this relationship better we conducted two studies of male football players. In Study 1, we examined adult performance at the upper levels of football using a factor analysis and identified the characteristics that define what we termed a "Super Elite" level, which is the highest level of participation. This outcome measure was used in Study 2 to explore further the link between youth international experience and athletes' Super Elite experience. Overall, our results indicated that youth international experience is a limited predictor of participation at the Super Elite level of football. Participation at the U21 level was the strongest, most consistent predictor of Super Elite level participation. U17 participation was found to be either an insignificant or a negative predictor of subsequent participation in international football. The effect of U19 participation on later participation was partly significant, but weaker than the effect of U21 participation, and depended on the national context and the playing positions of the athletes. When looking at the effect of different youth career types, careers involving U21 international experience were the strongest predictors of later careers as Super Elite athletes. National governing bodies that want to ensure success in talent identification and development should therefore consider focusing fewer resources on youth international competitions in age categories before adulthood. A total of 1,482 players who had national football team experience at either the U17, U19, U21, or senior levels were included in our studies.



#14 Evaluation of Match Results of Five Successful Football Clubs With Ensemble Learning Algorithms

Reference: Res Q Exerc Sport. 2022 May 2;1-10. doi: 10.1080/02701367.2022.2053647. Online ahead of print.

Authors: Enes Filiz

Summary: Football, one of the most popular and loved sports branches, always keeps its excitement, ambition, passion, joy and sadness together. European football, the football capital, is an attraction for fans and footballers. In this study, the official match results (league, country cup, European cup) of five successful football clubs (Bayern Munchen, Barcelona, Juventus, Manchester City, Paris Saint Germain) in the five major leagues of European football (La Liga, Premier League, Serie A, Bundesliga, Ligue 1) were evaluated. For this analysis, ensemble learning algorithms (AdaBoost, Bagging) and machine learning algorithms (Naive Bayes, artificial neural networks, K-nearest neighbor, C4.5/Random forest/Reptree decision tree) were used. In addition, the attributes that play an active role in the classification of the match results of five successful football clubs were determined with the Symmetrical Uncertainty feature selection algorithm. As effective attributes, "Conceded goal," "Half time result," "Scoring first" and "Shooting accuracy" attributes revealed to be common for five successful football clubs. In general, it was observed that ensemble learning algorithms gave successful results and AdaBoost/ANN algorithm was determined as the most successful. On the basis of football clubs, the most successful classification result was achieved for Barcelona with a rate of 99.3%. Obtained outputs from Ensemble learning and feature selection help sport researchers and football club planners understand and revise the match results of current football match strategies. The study has mainly twofold: to find best performer ensemble and machine learning algorithm(s) for classifying match results and to extract important features on match results.



#15 Effects of training on plasmatic cortisol and testosterone in football female referees

Reference: Physiol Rep. 2022 May;10(9):e15291. doi: 10.14814/phy2.15291.

Authors: Antonella Muscella, Giulia My, Selmi Okba, Daniele Zangla, Antonino Bianco, Santo Marsigliante

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Summary: There is very little about the impact that sports training has on female football referees. Therefore, we determined the effects of a 40-week physical preparation, including a full football season, on plasma testosterone and cortisol concentrations and physical performance in female football referees. Plasma cortisol and testosterone concentrations were assayed together with fitness tests at the beginning of the training period (T0, in September), after 8 weeks from T0 (T1), at the mid of the season (T2, 24 weeks after T0), and at the end of the season (T3, in June, 40 weeks after T0). Plasma cortisol increased during the first period and up to T2 (from 15.4 ± 4.7 to 28.5 ± 3.9 µg/dl; p < 0.001), and then decreased at the end of the season (T3: 16.0 ± 2.4 µg/dl). Plasma testosterone concentration in T0 was 14.2±0.37 µg/dl and increased in T1 (57.1 ± 3.7 µg/dl) and T2 (47 ± 3.7 µg/dl) and then decreased in T3 (33.5 ± 2.8 µg/dl). Resting testosterone levels in women were very low (14,2 ± 0.37 µg/dl) (Figure 3c). Testosterone increased in T1 (57.1 ± 3.7 µg/dl) and T2 (47 ± 3.7 µg/dl) whilst, at the end of the season, its concentration decreased (33.5 ± 2.8 µg/dl) (Figure 3c). Significant improvements were observed in all physical performances during the observed period (ANOVA, p < 0.05). Finally, testosterone and cortisol concentrations significantly (p < 0.0001 for both) correlated with maximal oxygen consumption. In T1, testosterone concentration was also significantly correlated with running speed test (p < 0.001). In conclusion, training induces endocrine changes in order to maintain body homeostasis in women referees. It is important that coaches and sports scientists regularly observe changes in endocrine function induced by training and matches in female referees, because they can help maximize referees' performance and limit cases of overtraining.



#16 Epidemiology of Campus Football Injuries in Ningxia, China: Occurrence, Causes, and Management

Reference: Front Public Health. 2022 Apr 26;10:893541. doi: 10.3389/fpubh.2022.893541. eCollection 2022.

Authors: Hengyuan Liu, Sen Huang, Te Bu, Wei Jiang, Tao Fu, Liliang Zhao

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Summary: By 2022, the Chinese government intends to have more than 30 million primary-, middle- and high-school children and adolescents regularly participate in campus football. In contrast, epidemiology of campus football injuries is completely missing. The goal of this descriptive epidemiological study was to determine the current state of campus football injuries and then to recommend appropriate prevention and management strategies. This retrospective epidemiological study conducted a survey of students, physical education and football teachers in primary, middle and high schools in the Ningxia Autonomous Region to determine the campus football injuries that occurred throughout the preceding 12-month period. The survey comprised questions on demographic characteristics, the occurrence, causes, and management of campus football injuries. A total of 1,285 students and 200 teachers returned eligible surveys. 25.7% of students had encountered injury accidents while participating in campus football activities. 31.3% of high school students, 23.8% of middle school students, and 19.2% of primary school students have sustained injuries. Football competition, accounting for 45.4% of all injuries, is the leading cause of injury. Football class teaching, which accounted for 3.0% of all injuries, had the lowest injury rate of any campus football activity. Students and teachers reported that a lack of safety awareness and injury prevention education were the primary causes of injuries. Only 18.7% and 11.4% of students are familiar with first aid basics and cardiopulmonary resuscitation, respectively. 10.6% and 7.5% of students lack any first aid basics and skills, respectively. 43.9% of students lack insurance coverage for athletic injuries. 62.5% and 38.5% of teachers reported that schools lack first aid training and an emergency plan for injuries, respectively. Students in Ningxia's campus football programs have a high injury risk. Injury prevention and management strategies lag significantly behind the mainstream nationwide promotion of campus football in China.



#17 Influence of the COVID-19 Lockdown and Restart on the Injury Incidence and Injury Burden in Men's Professional Football Leagues in 2020: The UEFA Elite Club Injury Study

Reference: Sports Med Open. 2022 May 13;8(1):67. doi: 10.1186/s40798-022-00457-4.

Authors: Markus Waldén, Jan Ekstrand, Martin Hägglund, Alan McCall, Michael Davison, Anna Hallén, Håkan Bengtsson

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Summary: Studies on football and the coronavirus disease 2019 (COVID-19) have mainly focused on the lockdown consequences for player fitness, the resumption of football training, and how to safely restart the league play, but injury data are scarce. The aim was to describe the injury incidence and injury burden in men's professional football teams during the pandemic year of 2020. Nineteen teams in 12 countries prospectively registered data on player-exposure and time-loss injuries throughout 2020. All major football leagues were paused as a direct response to the pandemic in March 2020 and were thereafter completely cancelled or restarted after a lockdown interval of at least two months. Historical data from 43 teams in the same cohort during the five preceding years (2015-2019) were used as reference. Between-season and within-season comparisons were made for injury incidence (number of injuries per 1000 h) and injury burden (number of absence days per 1000 h) with 95% confidence intervals and interquartile ranges. There was no increased match injury incidence or injury burden following the restart in 2020 compared with other time periods of 2020 and the corresponding periods 2015-2019. There was an increased training injury incidence and injury burden immediately during the lockdown in 2020, and they remained elevated also following the restart, being higher in 2020 compared with 2015-2019, respectively. The injury characteristics during the first months of the new 2020/21 season (August/September-December) were similar between the five teams that cancelled their 2019/20 season in March 2020 and the 14 teams that restarted their season in May/June 2020. There was no increased match injury incidence or injury burden following the COVID-19 lockdown and restart of the football season in 2020, but training injury incidence and injury burden were elevated and higher than in 2015-2019.



#18 Isolated Obturator Internus Muscle Strain Injury in a Professional Football Player: A Case Report

Reference: Cureus. 2022 Apr 8;14(4):e23949. doi: 10.7759/cureus.23949. eCollection 2022 Apr.

Author: Alexandros Toliopoulos

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Summary: The present case report concerns an isolated obturator internus muscle strain. The patient, who was a 30-year-old professional, elite-level football player, suffered the injury during the warm-up before a football match. Isolated injuries of the obturator internus are very uncommon and they are extremely rarely reported in the literature. The diagnosis was made clinically, documented by magnetic resonance imaging. The rehabilitation program was conducted conservatively with physical therapy and kinesiotherapy. The patient's return to full athletic activity took place 2 weeks after the incident.



#19 Epidemiological Comparison of ACL Injuries on Different Playing Surfaces in High School Football and Soccer

Reference: Orthop J Sports Med. 2022 May 5;10(5):23259671221092321. doi: 10.1177/23259671221092321. eCollection 2022 May.

Authors: Micah S Ngatuvai, Jingzhen Yang, Sandhya Kistamgari, Christy L Collins, Gary A Smith

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Summary: Anterior cruciate ligament (ACL) injuries are among the most common serious injuries to athletes in the United States. Among high school sports, the highest rates of ACL injury occur in soccer and football. To compare ACL injuries on artificial turf and natural grass using a nationally representative sample of high school athletes participating in football and boys' and girls' soccer. ACL injuries among high school athletes participating in football and soccer were obtained from the High School Reporting Information Online surveillance system during the 2007-08 through 2018-19 school years. National estimates and injury proportion ratios (IPRs) with 95% CIs were calculated for ACL injuries that occurred on artificial turf versus natural grass. A total of 1039 ACL injuries were reported, which represented an estimated 389,320 (95% CI, 358,010-420,630) injuries nationally. There were 74,620 estimated football-related ACL injuries on artificial turf and 122,654 on natural grass. Likewise, 71,877 of the estimated soccer-related ACL injuries occurred on artificial turf and 104,028 on natural grass. A contact-injury mechanism accounted for 50.2% of football-related ACL injuries on artificial turf and 60.8% on natural grass. For soccer-related ACL injuries, a noncontact mechanism predominated on artificial turf (61.5%) and natural grass (66.4%). Among all injuries, ACL injuries were more likely to occur on artificial turf than natural grass in both football (IPR, 1.23 [95% CI, 1.03-1.47]) and girls' soccer (IPR, 1.53 [95% CI, 1.08-2.16]); however, no significant association was found in boys' soccer (IPR, 1.65 [95% CI, 0.99-2.75]). Among lower extremity injuries, ACL injuries were more likely to occur on artificial turf than natural grass in both boys' soccer (IPR, 1.72 [95% CI, 1.03-2.85]) and girls' soccer (IPR, 1.61 [95% CI, 1.14-2.26]); however, the association was not significant in football (IPR, 1.17 [95% CI, 0.98-1.39]). ACL injuries were more likely to occur (ie, had larger IPRs) on artificial turf than natural grass; however, this relationship was not statistically significant for all sports.






The dose–response relationship between training-load measures and aerobic fitness in elite academy soccer players

The aim of the current study was to examine the dose–response relationships between training load (TL) measures and the consequent changes in aerobic fitness.





The influence of the offside rule on players’ positional dynamics in soccer small-sided games

The aim of this study was to to compare the positional dynamics of 3v3 SSGs with and without the offside rule.





Latest research in football - week 17 - 2022

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 Impact of the Menstrual Cycle Phases on the Movement Patterns of Sub-Elite Women Soccer Players during Competitive Matches

Reference: Int J Environ Res Public Health. 2022 Apr 7;19(8):4465. doi: 10.3390/ijerph19084465.

Authors: Pierre-Hugues Igonin, Isabelle Rogowski, Nathalie Boisseau, Cyril Martin

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Summary: The purpose of this study was to evaluate the influence of the menstrual cycle phases on the movement patterns of sub-elite women soccer players during competitive matches over three consecutive seasons. Individual movement data were analyzed and compared in eight players from the second French League at the early follicular (EF), late follicular (LF) and mid-luteal (ML) phases of their menstrual cycle, determined by the calendar method. The movement patterns, expressed as meters per minute, were recorded during competitive matches using devices placed on the player's ankle. Our results showed significantly lower distances covered at moderate and high velocity in the EF phase than in the LF and ML phases (Cohen's d effect size = 1.03 and 0.79, respectively). The total distance covered during matches and the number of sprints also were reduced during EF compared with LF (d = 0.78 and 0.7, respectively). Overall, the total distance and distance covered at low velocity were significantly lower during the second half-time of the matches (d = 1.51), but no menstrual cycle phase × game period interaction was noted. In conclusion, our study suggests that EF may impact the movement pattern of sub-elite women soccer players during competitive matches, without any modulation of this effect by the playing time. Despite the low sample size, these results can be useful for coaches and support staff to modulate training loads and player rotation during soccer games.



#2 In-Season Microcycle Quantification of Professional Women Soccer Players-External, Internal and Wellness Measures

Reference: Healthcare (Basel). 2022 Apr 7;10(4):695. doi: 10.3390/healthcare10040695.

Authors: Renato Fernandes, Halil İbrahim Ceylan, Filipe Manuel Clemente, João Paulo Brito, Alexandre Duarte Martins, Hadi Nobari, Victor Machado Reis, Rafael Oliveira

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Summary: Although data currently exists pertaining to the intensity in the women's football match, the knowledge about training is still scarce. Therefore, the aim of this study was to quantify external (locomotor activity) and internal (psychophysiological) intensities, as well as the wellness profile of the typical microcycle from professional female soccer players during the 2019/20 in-season. Ten players (24.6 ± 2.3 years) from an elite Portuguese women soccer team participated in this study. All variables were collected in 87 training session and 15 matches for analysis from the 2019-2020 in-season. Global positioning variables such total distance, high-speed running, acceleration, deceleration and player load were recorded as intensity while Rated Perceived Exertion (RPE) and session-RPE were recorded as internal measures. The Hooper Index (HI) was collected as a wellness parameter. The results showed that internal and external intensity measures were greater in matches compared to trainings during the week (match day minus [MD-], MD-5, MD-4, MD-2), p &lt; 0.05 with very large effect size (ES). In the same line, higher internal and external intensity values were found in the beginning of the week while the lowest values were found in MD-2 (p &lt; 0.05, with very large ES). Regarding wellness, there was no significant differences in the HI parameters between the training days and match days (p &gt; 0.05). This study confirmed the highest intensity values during MD and the lowest on the training session before the MD (MD-2). Moreover, higher training intensities were found in the beginning of the training week sessions which were then reduced when the MD came close. Wellness parameters showed no variation when compared to intensity measures. This study confirmed the hypothesis regarding internal and external intensity but not regarding wellness.



#3 External Match Load in Amateur Soccer: The Influence of Match Location and Championship Phase

Reference: Healthcare (Basel). 2022 Mar 22;10(4):594. doi: 10.3390/healthcare10040594.

Authors: Mauro Miguel, Rafael Oliveira, João Paulo Brito, Nuno Loureiro, Javier García-Rubio, Sergio Jose Ibáñez

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Summary: Assessment of the physical dimension implicit in the soccer match is crucial for the improvement and individualization of training load management. This study aims to: (a) describe the external match load at the amateur level, (b) analyze the differences between playing positions, (c) verify whether the home/away matches and if (d) the phase (first or second) of the championship influence the external load. Twenty amateur soccer players (21.5 ± 1.9 years) were monitored using the global positioning system. The external load was assessed in 23 matches, where 13 were part of the first phase of the competition (seven home and six away matches) and the other 10 matches belonged to the second (and final) phase of the championship (five home and five away matches). A total of 173 individual match observations were analyzed. The results showed significant differences between playing positions for all the external load measures (p &lt; 0.001). There were higher values observed in the total distance covered for central defenders (p = 0.037; ES = 0.70) and in high-intensity decelerations for forwards (p = 0.022; ES = 1.77) in home matches than in away matches. There were higher values observed in the total distance (p = 0.026; ES = 0.76), relative distance (p = 0.016; ES = 0.85), and moderate-intensity accelerations (p = 0.008; ES = 0.93) for central defenders, in very high-speed running distance for forwards (p = 0.011; ES = 1.97), and in high-intensity accelerations (p = 0.036; ES = 0.89) and moderate-intensity decelerations (p = 0.006; ES = 1.11) for wide midfielders in the first phase than in the second phase of the championship. Match location and championship phase do not appear to be major contributing factors to influence the external load while the playing position should be used as the major reference for planning the external training load.



#4 Understanding the Relationship between Sport Courage and Female Soccer Performance Variables

Reference: Int J Environ Res Public Health. 2022 Apr 12;19(8):4654. doi: 10.3390/ijerph19084654.

Authors: Erkut Konter, Adam Gledhill, Yee Cheng Kueh, Garry Kuan

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Summary: The purpose of this study was to examine the relationships between female soccer players' courage and key performance variables (level of participation, injury past, being selected or non-selected by a national team, being starter or substitute). The Sport Courage Scale-31, by Konter and Ng (2012) and key performance variables were collected from 210 female soccer players aged 12 to 27 (M = 17.97 ± 3.34 years old). Spearman correlations and Mann-Whitney U tests were used to analyse the collected data. The correlations between mastery (r = 0.196), determination (p = 0.239), assertiveness (r = 0.325), sacrifice behaviour (r = 0.182), total sport courage (r = 0.265) and age of female soccer players were found to be significant (p &lt; 0.05). Female soccer players who have sustained an injury in the past scored significantly higher on the venturesome scale (p = 0.006) than those who have not sustained an injury in the past. In comparison, female soccer players who have not sustained an injury in the past or who have not been substituted had significantly more mastery than female soccer players who have sustained an injury in the past or who have been substituted (p = 0.017, p = 0.002, respectively). This study indicates that sport courage is related to key performance variables among female soccer players. Mastery and age seem to be related to courageous behaviour, whereas increasing venturesomeness might cause injuries in female soccer. Some relevant implications for practitioners can be drawn from the present findings.



#5 Analysis of Intensities Using Inertial Motion Devices in Female Soccer: Do You Train like You Compete?

Reference: Sensors (Basel). 2022 Apr 8;22(8):2870. doi: 10.3390/s22082870.

Authors: Juan M García-Ceberino, Ana Bravo, Ernesto de la Cruz-Sánchez, Sebastián Feu

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Summary: Intensity research in female soccer is limited. This study aimed to investigate whether female professional soccer players train with external and internal intensities similar to those recorded in real competition. The specific players' position, the game situation and training task type were analyzed in a total of 18 female players (26.25 ± 3.89 years). The empirical, descriptive and associative study was structured into two parts. Part 1: characterizing the training sessions (n = 13) and official matches (n = 3) using the Integral Analysis System of Training Tasks. The association between sports planning variables was evaluated using adjusted standardized residuals from contingency tables, Chi-Square and Fisher tests, as well as the Phi and Cramer's V coefficients. The main findings show that the coach and/or physical trainer predominantly planned training sessions using small-sided games, which integrate physical fitness and tactical-technical behaviors of the game and imply a medium-high subjective external intensity (20.63 ± 5.79 points). The subjective external intensity of the matches was very high (30.00 ± 0.00 points). Part 2: quantifying the external and internal intensity through the inertial motion devices and heart rate monitors. Differences in the intensities according to the type of session (training session and match), specific position of the players, game situation and type of the training task were assessed through different statistical tests. By specific position (Kruskal-Wallis H and one-factor ANOVA tests), defenders performed fewer accelerations/min and decelerations/min, while they recorded higher heart rates in training sessions and official matches. In contrast, the wingbacks performed higher accelerations/min and decelerations/min in training sessions and official matches. The wingers had the lowest heart rate in official matches. Regarding the game situation (Kruskal-Wallis H test) measured during training sessions, the unopposed tasks recorded higher accelerations/min and decelerations/min, while the small-sided games and full games recorded higher values in the rest of the intensities (both subjective and objective). With regard to the type of training task (Kruskal-Wallis H test), the simple application exercises recorded higher accelerations/min and decelerations/min. Distance in meters/min was greater in the complex application exercises. High-intensity activity/min and player load/min were higher in the simple specific game. In addition, modified sport and real game recorded higher subjective external intensity*min, sprints/min and heart rate. Furthermore, training sessions differed statistically (Mann-Whitney U test) from official matches in terms of subjective intensity and the objective external and internal intensity variables weighted by minutes. For all these reasons, female players do not train (training sessions) as they compete (official matches). The use of inertial motion devices has made it possible to quantify intensities during training sessions and real competition in soccer.



#6 Mind the gap! A survey comparing current strength training methods used in men's versus women's first team and academy soccer

Reference: Sci Med Footb. 2022 Apr 27. doi: 10.1080/24733938.2022.2070267. Online ahead of print.

Authors: Stephen J McQuilliam, David R Clark, Robert M Erskine, Thomas E Brownlee

Summary: Much less is known about strength and conditioning (S&C) practice in women's versus men's soccer. The aim of this study was to compare S&C practice between coaches working in men's or women's soccer, at first team or academy level, worldwide. A total of 170 participants, who were involved with S&C support at their soccer club (in Europe, USA and South America, within men's or women's first team or academy settings) completed a comprehensive online survey, designed to evaluate (i) their academic qualifications and S&C coaching experience; and their preferred methods for (ii) physical testing; (iii) strength and power development; (iv) plyometric training; (v) speed development; and (vi) periodization. Women's academies had fewer weekly in-season S&C sessions than men's academies (1.6±0.6 vs. 2.3±0.9, p=0.005). Relatively, fewer women's academy S&C coaches (6%) used Olympic weightlifting movements than men's academy S&C coaches (32%, p=0.030). Relatively, more women's academy coaches (47%) used the Nordic hamstring exercise (NHE) compared to men's academy coaches (15%, p=0.006), but relatively more women's vs. men's first team coaches (61% vs. 38%, p=0.028) and women's vs. men's academy (61% vs. 38% coaches, p=0.049) utilised rating of perceived exertion-based load prescriptions. Notable differences in S&C practice exist between coaches of men's and women's soccer squads, particularly at academy level. For example, fewer weekly S&C sessions in women academy players may have implications for physical development, while the greater use of subjective load prescriptions in both academy and first team women's squads may lead to sub-optimal performance gains.



#7 Maximal vs. explosive knee extensor strength in professional soccer players: inter-limb asymmetries and relationship with knee function

Reference: Eur J Sport Sci. 2022 Apr 27;1-19. doi: 10.1080/17461391.2022.2071636. Online ahead of print.

Authors: Victor R A Cossich, Ubiratã F Gavilão, Rodrigo A Goes, Jamila A Perini, Conrado T Laett, Nicola A Maffiuletti

Summary: The main aims of this study were to compare the magnitude of inter-limb asymmetry (ILA) and the relation with self-reported knee function between maximal and explosive knee extensor strength outcomes in professional soccer players. Forty-six male soccer players completed different maximal isokinetic and isometric contractions of the knee extensors for the assessment of maximal strength (peak torque and maximal voluntary contraction (MVC) torque) and explosive strength (early, intermediate, late, and peak rate of torque development (RTD)). Self-reported knee function was assessed with the International Knee Documentation Committee (IKDC) and Lysholm knee scoring scales. Peak torque and MVC torque showed comparable ILAs (8-9%), both being significantly lower than all RTD ILAs (16% on average; p < 0.001). ILAs for early RTD (21%) and peak RTD (19%) were significantly higher than all the other variables (p < 0.05). Only early and intermediate RTD were significantly correlated - though weakly - with both IKDC (rho = 0.32 for both) and Lysholm (rho = 0.36 and 0.30, respectively) scores. We conclude that explosive knee extensor strength - early RTD in particular - exhibited larger ILAs and better relations with self-reported knee function than peak torque and MVC torque in professional soccer players. These results confirm the validity and functional relevance of early RTD and the need for its inclusion in routine performance testing for soccer players.



#8 Effect of ball inclusion on jump performance in soccer players: a biomechanical approach

Reference: Sci Med Footb. 2022 May;6(2):241-247. doi: 10.1080/24733938.2021.1915495. Epub 2021 Apr 22.

Authors: Alberto Fílter, Jesús Olivares Jabalera, Alejandro Molina-Molina, Luis Suárez-Arrones, José Robles-Rodríguez, Thomas Dos'Santos, Irineu Loturco, Bernardo Requena, Alfredo Santalla

Summary: In soccer, vertical jump means jumping toward a ball. Since no vertical jump test includes the ball as a reference element, the effect that the ball would have in a vertical jump test is unknown. The aim of this study was to examine the biomechanical differences between run-up vertical jump measurements without (Run-up Vertical Jump) and with ball inclusion (Heading Test). Twelve semi- and professional soccer players were recruited. Athletes performed both jump tests in a biomechanical laboratory, where kinetic and spatiotemporal variables were collected and compared using a Student's dependent t-test for paired samples. Overall, players performed a different jumping strategy during the heading test compared to the run-up vertical jump, exhibiting: 1) higher horizontal velocity during initial contact (+45.3%, P ≤ .001), 2) shorter contact time, greater rate of force development, and total impulse during push-off (+27.5%, +53%, and +10.6%, respectively, P ≤ .008), 3) higher CoM horizontal and resultant velocity during take-off (+76.1% and 20.5%, respectively, P ≤ .001), 4) better vertical jump performance (+4.3%, P ≤ .0001), and 5) larger body angle rotation during landing (+63.3%, P = .006), compared to run-up vertical jump (effect size: 0.78 to 3.7). In general, soccer players display greater vertical jump heights in heading test, which highlights the importance of including an overhead ball during soccer-specific jump tests. Coaches and practitioners are encouraged to assess, and perhaps develop, the jumping ability of soccer players using a suspended ball as a specific target.



#9 Missing data: current practice in football research and recommendations for improvement

Reference: Sci Med Footb. 2022 May;6(2):262-267. doi: 10.1080/24733938.2021.1922739. Epub 2021 May 26.

Authors: David N Borg, Robert Nguyen, Nicholas J Tierney

Summary: A survey of 136 articles published in 2019 (sampled at random) was conducted to determine whether a statement about missing data was included. The proportion of studies reporting on missing data was low, at 11.0% (95% confidence interval = 6.3% to 17.5%). We recommend that researchers describe the number and percentage of missing values, including when there are no missing values. Exploratory analysis should be conducted to explore missing values, and visualisations describing missingness overall should be provided in the paper, or at least in supplementary materials. Missing values should almost always be imputed, and imputation methods should be explored to ensure they are appropriately representative. Researchers should consider these recommendations and pay greater attention to missing data and its influence on research results.



#10 Neuromuscular control and hop performance in youth and adult male and female football players

Reference: Phys Ther Sport. 2022 Apr 13;55:189-195. doi: 10.1016/j.ptsp.2022.04.004. Online ahead of print.

Authors: Sofi Sonesson, Martin Hägglund, Joanna Kvist, Kalle Torvaldsson, Hanna Lindblom, Anne Fältström

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Summary: The aim was to compare neuromuscular control and hop performance between youth and adult male and female football players. 119 youth players (13-16 years; 68 males) and 88 adult players (17-26 years; 44 males) participated in the investigation. Neuromuscular control assessed with drop vertical jump (DVJ) and tuck jump assessment (TJA). Hop performance assessed with single-leg hop for distance and side hop were assessed. Adult females had smaller normalized knee separation distances (NKSD) during DVJ at initial contact (77.9 ± 18.5 vs. 86.1 ± 11.0, p = 0.010) and at maximum knee flexion (59.7 ± 23.4 vs.74.1 ± 18.1, p = 0.001) compared to youth females. TJA revealed more technique errors in youths compared to adults (males 10 (8-11) vs. 8 (7-10); females 11 (9-12) vs. 9 (8-11), p < 0.05). Youths demonstrated inferior hop performance (males single-leg hop 142 ± 18 vs. 163 ± 17, side hop 41 ± 12 vs. 52 ± 12, p < 0.001; females side hop 32 ± 10 vs. 38 ± 14, p < 0.05). Youth players demonstrated reduced neuromuscular control during TJA and inferior hop performance compared to adult players. Adult female players demonstrated greater knee valgus during DVJ compared to youth female players.



#11 Hamstrings injuries in football

Reference: J Orthop. 2022 Apr 11;31:72-77. doi: 10.1016/j.jor.2022.04.003. eCollection May-Jun 2022.

Authors: André Gismonti Garcia, Renato Andrade, José Afonso, José Luíz Runco, Antonio Maestro, João Espregueira-Mendes

Summary: Hamstrings injuries are a major concern in football (soccer), affecting both recreational players and professional athletes. Although being a recognized issue within the football community, its incidence has been increasing over the last years and still poses a challenge to all practitioners involved. The goal of this narrative review is to outline hamstrings injuries epidemiology and mechanisms of injury, identify and discuss its risk factors, provide an approach to a proper early diagnosis, evaluate the efficacy of current treatment options and return to sports, and present the best strategies for hamstrings injury prevention. These guidelines will help the sports medicine staff team on how to better manage their players with or at risk of hamstrings injuries. Despite several breakthroughs in research of hamstrings injuries, there is still heterogeneity across studies and lack of consensus in regards to classification, diagnosis, treatment and prevention. Hamstrings injuries compromise the athlete's performance with time loss due to injury, shortens their highest-level career longevity with higher risk of reinjury rates, and is a defying problem for clubs to balance financial losses due to having their players off the pitch. Further research is warranted to keep moving forward with evidence on treating and preventing hamstrings injuries to mitigate its high incidence and keep the players safe.



#12 Analysis of the Football Transfer Market Network

Reference: J Stat Phys. 2022;187(3):27. doi: 10.1007/s10955-022-02919-1. Epub 2022 Apr 19.

Authors: Tobias Wand

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Summary: Using publicly available data from the football database, it is possible to construct a trade network between football clubs. This work regards the network of the flow of transfer fees between European top league clubs from eight countries between 1992 and 2020 to analyse the network of each year's transfer market. With the transfer fees as weights, the market can be represented as a weighted network in addition to the classic binary network approach. This opens up the possibility to study various topological quantities of the network, such as the degree and disparity distributions, the small-world property and different clustering measures. This article shows that these quantities stayed rather constant during the almost three decades of transfer market activity, even despite massive changes in the overall market volume.



#13 Tests of rubber granules used as artificial turf for football fields in terms of toxicity to human health and the environment

Reference: Sci Rep. 2022 Apr 23;12(1):6683. doi: 10.1038/s41598-022-10691-1.

Authors: Beata Grynkiewicz-Bylina, Bożena Rakwic, Barbara Słomka-Słupik

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Summary: Rubber waste, in the form of granules of styrene butadiene rubber and ethylene-propylene-diene-monomer with a particle size of 0.5 to 4 mm, is broadly used for the construction of synthetic surfaces of sport fields. This method of recycling may be significantly limited due to the restrictions on polycyclic aromatic hydrocarbons (PAHs) content in rubber granules in the European Union since 2022. This also applies to the recommendations of the European Chemicals Agency in relation to the identification of other hazardous chemicals in this waste, including metal elements. The scope of the research included the identification of organotin compounds, PAHs content and 18 elements leached from recycled rubber granules in terms of substances harmful to human health and to natural environment. The research covered 84 samples of rubber granules collected from the surface of football pitches or supplied by recyclers in Poland. The test results showed an over-standard content of PAHs in rubber granules. This result confirms the need to develop alternative directions of rubber granules application: construction and hydro construction, reinforcing soil and roadsides, asphalt pavements, making retaining walls, anti-shock and anti-vibration slabs, soundproofing and damping screens, paving stones and landscaping elements.



#14 Activity Level and Nature of Practice and Play in Children's Football

Reference: Int J Environ Res Public Health. 2022 Apr 11;19(8):4598. doi: 10.3390/ijerph19084598.

Authors: Tone Nybakken, Coral Falco

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Summary: This study analyzes the activity level and nature of organized football training (deliberate practice, DPR), compared with when children play football on their own (deliberate play, DPL), in a sample of selected (YT) and non-selected (BT) talents. A total of 29 observations were analyzed over 2650 min, focusing on the kind of activity, variability, and intensity of the training. In DPL, there are more finishing on goal, involvement, and challenges in 1:1 situation, and more ball touches and ball transport in games, compared with DPR. Additionally, DPL has more activity time (68% vs. 56%) and fewer breaks overall (32% vs. 44%). In DPL, children spend more time playing against each other (92% vs. 36%), and most of the time there are games or finishing on goal. In DPR, children spend more time playing together with someone (2% vs. 44%) and in passing and receiving the ball. DPR training contains more standardized exercises and protected situations. DPR-YT training differs from DPR-BT training with less activity time, ball touches, attempts on goal, and 1:1 situations. In conclusion, the results support DPL providing more football-specific activity. More DPR training at the expense of DPL might reduce practice time for skill development.



#15 Perceptions of Professional Football Players on Injury Risk Factors and Prevention Strategies

Reference: Sci Med Footb. 2022 May;6(2):148-152. doi: 10.1080/24733938.2021.1937689. Epub 2021 Jun 9.

Authors: Rogério Ferreira Liporaci, Sergio Yoshimura, Bruno Manfredini Baroni

Summary: Considering individual beliefs and preferences is a pillar of the evidence-based practice and determines compliance and outcomes of an intervention. However, little is known about the professional football (soccer) players' perceptions on injury issues. The aim of this study was to describe the professional football players' perceptions towards injury risk factors and prevention strategies. One-hundred male professional football players answered an online questionnaire. The top-five risk factors included poor muscle strength/power; poor rest/sleep; short interval between matches; high number of matches in season; and excessive training. More than ¾ of football players in our study considered the following strategies as being effective in reducing injury risk: workload monitoring; warm-up; lumbo-pelvic stability training; proprioceptive training; functional training; monitoring diet; flexibility training; and conventional strength training. Perceptions of professional male football players regarding injury risk factors and prevention strategies are only partially in line with current scientific evidence. These perceptions have been usually overlooked, and should be considered by medical/coaching staffs in order to get greater compliance to injury prevention programs.



#16 Injury incidence and prevalence in Finnish top-level football - one-season prospective cohort study

Reference: Sci Med Footb. 2022 May;6(2):141-147. doi: 10.1080/24733938.2021.1917775. Epub 2021 May 22.

Authors: Einari Kurittu, Tommi Vasankari, Tuomas Brinck, Jari Parkkari, Olli J Heinonen, Pekka Kannus, Timo Hänninen, Klaus Köhler, Mari Leppänen

Summary: The aim was to investigate the injury characteristics in Finnish male football players. One-season prospective epidemiological study. Data were collected via injury reports from the medical staff and directly from the players using the Olso Sports Trauma Research Center Health Questionnaire. The first team squads of Finnish football league (n = 12 teams, 236 players) participated in this study. Injury incidence was assessed. A total of 541 injuries occurred during the exposure of 62 878 hours. Injury incidence per 1000 exposure hours was 8.6 (30.6 in matches and 3.4 in training). A player sustained on average 2.3 (median 2, range 0-13) injuries during the study. Thigh and ankle were the most commonly injured body parts for acute injuries and hip/groin were the most commonly injured body part for overuse injuries. The median absence time for all injuries was 12 (range 0-107) days, 12 (range 0-107) for acute, and 8 (range 0-61) for overuse injuries. Thigh injuries caused the greatest consequences in terms of absence from full participation (median 5 days, range 0-88). Lower limb muscle injuries were the most prevalent injuries in the study. Collecting data directly from the players enabled to report more injuries compared to what was reported only by the medical staff.



#17 Physical and Mental Fatigue Reduce Psychomotor Vigilance in Professional Football Players

Reference: Int J Sports Physiol Perform. 2022 Apr 27;1-8. doi: 10.1123/ijspp.2021-0387. Online ahead of print.

Authors: Luca Angius, Michele Merlini, James Hopker, Mattia Bianchi, Francesco Fois, Francesco Piras, Paolo Cugia, James Russell, Samuele Maria Marcora

Summary: Professional football players experience both physical and mental fatigue (MF). The main aims of this randomized crossover study were to investigate the effect of MF on repeated-sprint ability (RSA) and the effects of both physical fatigue and MF on psychomotor vigilance. Seventeen male professional football players performed 10 maximal 20-m shuttle sprints interspaced by incomplete recovery (RSA test). Running speed, heart rate, brain oxygenation, and rating of perceived exertion were monitored during each sprint. The RSA test was preceded by either a 30-minute Stroop task to induce MF or by watching a documentary for 30 minutes (control [CON]) in a randomized counterbalanced order. Participants performed a psychomotor vigilance test at baseline, after the cognitive task (MF or CON), and after the RSA test. Heart rate and rating of perceived exertion significantly increased, while running speed and brain oxygenation significantly decreased over the repeated sprints (P < .001) with no significant differences between conditions. Response speed during the psychomotor vigilance test significantly declined after the Stroop task but not after CON (P = .001). Response speed during the psychomotor vigilance test declined after the RSA test in both conditions (P < .001) and remained lower in the MF condition compared to CON (P = .012). MF does not reduce RSA. However, the results of this study suggest that physical fatigue and MF have negative and cumulative effects on psychomotor vigilance. Therefore, strategies to reduce both physical fatigue and MF should be implemented in professional football players.



#18 Recovery During a Congested Schedule and Injury in Professional Football

Reference: Int J Sports Physiol Perform. 2022 Apr 28;1-8. doi: 10.1123/ijspp.2021-0504. Online ahead of print.

Authors: Benoit Delaval, Abd-Elbasset Abaïdia, Barthélémy Delecroix, Franck Le Gall, Alan McCall, Said Ahmaidi, Gregory Dupont

Summary: The aim was to analyze the relationships between the recovery kinetics experienced by professional football players and noncontact injury. A cohort of 46 professional football players (age 24.2 [4.7] y) from the same team (French Ligue 1) was monitored each day between matches when the team played twice a week. The recovery monitoring procedure was implemented after 38 matches and included some questionnaires: duration of sleep, Hooper scale (quality of sleep, level of stress, fatigue, and muscle soreness), perceived recovery status scale, creatine kinase concentrations, a countermovement jump, and an isometric force test. Noncontact injuries were collected during these periods. Noncontact injuries were associated with perceived fatigue and muscle soreness 2 days (relative risk [RR] = 1.89 and 1.48, respectively) and 3 days following the matches (RR = 2.08 and 2.08, respectively). An increase of sleep quantity during the 2 nights following a match was significantly associated with a lower RR (RR = 0.65), as well as a lower decrement score on the isometric force test on each of the 3 days after the matches (RR = 0.97, RR = 0.99, and RR = 0.97, respectively). No other association was reported for the variables sleep quality, stress, perceived recovery, creatine kinase concentrations, countermovement jump, and noncontact injuries. During a congested schedule, implementing a recovery monitoring protocol including questionnaires about fatigue, muscle soreness, quantity of sleep, and a physical test of isometric force could help practitioners prevent injuries.



#19 Multi-hosting UEFA European Football Championship: Fair enough between participating teams?

Reference: Sci Med Footb. 2022 Apr 29. doi: 10.1080/24733938.2022.2072944. Online ahead of print.

Authors: Franck Brocherie, Quentin De Larochelambert, Grégoire P Millet

Summary: The aim was to describe the effects of travel distance and bio-meteorological conditions on the 2020 multi-hosting UEFA European Championship's match outcomes and progress in competition. Teams' basecamps, distance from match venues, match outcomes (defeat, draw and win), bio-meteorological data (ambient air temperature, relative humidity and wet bulb globe temperature) and corresponding FIFA world ranking were extracted from the official UEFA and FIFA websites, respectively; and analyzed through Chi-squared test (impact of basecamp location on match outcomes), Kruskal-Wallis test (distribution of travel distances carried out according to match outcomes and competition phases), ordinal regressions (with match outcomes and competition phases as variables of interest and FIFA ranking and venue distance as explanatory variables) and principal component analysis with the bio-meteorological conditions and match outcomes for each match. Teams with basecamp near match venue improved their match outcomes. However, neither Kruskal-Wallis test (p > 0.05) nor ordinal regressions (odds ratio (OR) > 0.96, p > 0.403) identified any significant effect of travel distance on match outcomes. Besides, FIFA ranking improved the likelihood of a favorable match outcome (OR = 0.87, p = 0.001) and progression in competition (OR = 0.97, p = 0.003). Further, despite some matches were played in more stressful bio-meteorological conditions, this was not associated with match outcomes (r = -0.07 to 0.19, p > 0.188). These findings cannot conclusively clarify on the effects of travel and bio-meteorological conditions on match outcomes and progress in the multi-hosting UEFA European championship, but suggest to carefully consider these variables for future multi-hosting competition to avoid any discrepancies between teams.



#20 Association between SARS-COV-2 infection and muscle strain injury occurrence in elite male football players: a prospective study of 29 weeks including three teams from the Belgian professional football league

Reference: Br J Sports Med. 2022 Apr 29;bjsports-2021-104595. doi: 10.1136/bjsports-2021-104595.

Authors: Evi Wezenbeek, Sander Denolf, Tine Marieke Willems, Dries Pieters, Jan G Bourgois, Renaat M Philippaerts, Bram De Winne, Matthias Wieme, Robbe Van Hecke, Laurence Markey, Joke Schuermans, Erik Witvrouw, Steven Verstockt

Summary: The aim of this study was to investigate the association between SARS-CoV-2 infection and muscle strain injury in elite athletes. A prospective cohort study in three Belgian professional male football teams was performed during the first half of the 2020-2021 season (June 2020-January 2021). Injury data were collected using established surveillance methods. Assessment of SARS-CoV-2 infection was performed by a PCR test before each official game. Of the 84 included participants, 22 were infected with SARS-CoV-2 and 14 players developed a muscle strain during the follow-up period. Cox's proportional hazards regression analyses demonstrated a significant association between SARS-CoV-2 infection and the development of muscle strain (HR 5.1; 95% CI 1.1 to 23.1; p=0.037), indicating an increased risk of developing muscle strains following SARS-CoV-2 infection. All athletes who sustained a muscle strain after infection were injured within the first month (15.71±11.74 days) after sports resumption and completed a longer time in quarantine (14.57±6.50 days) compared with the infected players who did not develop a muscle strain (11.18±5.25 days). This study reported a five times higher risk of developing a muscle strain after a SARS-CoV-2 infection in elite male football players. Although this association should be examined further, it is possible that short-term detraining effects due to quarantine, and potentially pathological effects of the SARS-CoV-2 infection are associated with a higher risk of muscle strain injury.



#21 Modeling Players' Scanning Activity in Football

Reference: J Sport Exerc Psychol. 2022 Apr 25;1-9. doi: 10.1123/jsep.2020-0299. Online ahead of print.

Authors: Marius Pokolm, Robert Rein, Daniel Müller, Stephan Nopp, Marie Kirchhain, Karl Marius Aksum, Geir Jordet, Daniel Memmert

Summary: The purpose of this study was to develop and test models of scanning activity in football. Gibson's ecological approach of visual perception and exploratory activity provided the theoretical framework for the models. The video-based data analysis consisted of 17 selected matches and 239 players of the Union of European Football Associations (UEFA) U17 and U19 European Championship 2018 and the UEFA U17 and U21 European Championship 2019. The results showed a positive relation between scanning frequency and successful passes, as well as changes in body orientation. Scanning frequency was also related to a player's appearances in national teams and to opponent pressure. Opponent pressure had a large effect on pass result and the player's body orientation. Previous research on the relation between scanning frequency and performance was extended by several contextual predictors. Future research should focus on gaining a deeper understanding of the relation between scanning frequency and further contextual variables related to scanning.



#22 Exploring Factors Related to Goal Scoring Opportunities in Professional Football

Reference: Sci Med Footb. 2022 May;6(2):181-188. doi: 10.1080/24733938.2021.1931421. Epub 2021 Jun 8.

Authors: Emiel Schulze, Ross Julian, Tim Meyer

Summary: Outscoring opponents is the primary goal in football. To optimise goal scoring opportunities (GSOs), it is important to understand the preceding physical and tactical performance. This observational study explored whether running behaviour prior to GSOs related to the subsequent outcome (goal or no goal) or contextual factors. Tracking data was collected from one professional team during its 2016/2017 season. Physical output was differentiated for attacking styles and analysed for attackers (taking shots) and defenders (trying to prevent shots). Counter attacks were found most effective, as outcomes improved with fewer defenders behind the ball (r=-0.27; p=0.03). Offensively, running behaviour in the minute prior to GSOs explained most variance and increased activities correlated with success (r=0.26; p=0.04). Moreover, decreased high-intensity distances covered during matches significantly correlated with favourable outcomes (r=-0.21; p=0.02). Finally, increased attacking effectiveness was found to relate to greater defensive covered distances (r=0.51; p<0.01). Running behaviour prior to GSOs was found to relate to the subsequent outcome. Specifically, space ahead of attackers, forcing defenders to cover more ground, was found to relate to GSO effectiveness. The running behaviour of attackers was found unrelated to previous activity, highlighting the significance of physical capacity and well-timed substitutions.






Occurrences of near-to-maximal speed-running bouts in elite soccer: Insights for training prescription and injury mitigation

The aim of this study was to quantify the occurrence of near-to-maximal speed-running bouts in elite footballers.





Visual search strategy and anticipation in tactical behavior of young soccer players

Visual search strategy and anticipation in tactical behavior of young soccer players.





Latest research in football - week 16 -2022

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 Effect of two incremental intensity field tests on wellness indices, recovery state, and physical enjoyment in soccer players

Reference: Eur Rev Med Pharmacol Sci. 2022 Apr;26(7):2279-2287. doi: 10.26355/eurrev_202204_28457.

Authors: O Selmi, D E Levitt, A Muscella, N Ouerghi, I Issaoui, W Abassi, L Hill, T Rosemann, A Bouassida, B Knechtle

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Summary: Competitive athletes must undergo fitness testing to monitor athlete progress and to create appropriate, progressive training programs. However, fitness testing adds to training stress; therefore, impacts of testing on wellness and recovery must be considered in test selection. This study investigated the effects of two incremental field tests [VAMEVAL test (T-VAM) and 20-m maximum shuttle test (20-m MST)] on wellness, total quality of recovery (TQR) and physical enjoyment (PE) in competitive soccer players. Twenty-two soccer players (20.9±1.5 years) completed two T-VAM and two 20-m MST in a randomized order on separate days with a 1-week interval between tests. TQR and wellness indices (sleep, fatigue, stress and muscle soreness) measures were collected before and 24 hours after each test. Heart rate (HR) was continuously monitored during each test. Rating of perceived exertion (RPE) and PE were assessed after each test. T-VAM resulted in higher PE, TQR and wellness scores than 20-m MST (p<0.05). T-VAM and 20-m MST resulted in similar HR and maximal aerobic speed. For T-VAM, TQR was correlated (p<0.01) with RPE and wellness indices. For 20-m MST, TQR was correlated (p<0.01) with wellness indices. HRmax and RPE were not correlated with wellness indices, TQR or PE. Overall, T-VAM and 20-m MST produced similar aerobic fitness testing results, but athletes responded more favorably to T-VAM. Coaches can use T-VAM for evaluating aerobic fitness while maximizing well-being and physical enjoyment among soccer players.



#2 Seasonal Variation of Physical Performance, Bilateral Deficit, and Interlimb Asymmetry in Elite Academy Soccer Players: Which Metrics Are Sensitive to Change?

Reference: J Strength Cond Res. 2022 Apr 1. doi: 10.1519/JSC.0000000000004248. Online ahead of print.

Authors: Chris Bishop, Will Abbott, Calum Brashill, Irineu Loturco, Marco Beato, Anthony Turner

Summary: This study aimed to report seasonal variations for (a) physical performance, (b) interlimb asymmetry, and (c) bilateral deficit (BLD) data over the course of a competitive soccer season and determine which metrics are sensitive to change. This study used a repeated-measures observational design for 19 under-20, elite, academy, soccer players (age: 17.58 ± 0.61 years; height: 1.81 ± 0.09 m; body mass: 74.36 ± 7.58 kg), who conducted bilateral and single-leg countermovement jumps (CMJ and SLCMJ), linear speed (5, 10, 20, and 30-m) and 505 change of direction (COD) speed tests, at pre, mid, and end of season time points. For jump tests, jump height, reactive strength index modified, time to takeoff, and countermovement depth metrics were monitored, with interlimb asymmetry and the BLD also calculated for each. Significant improvements (p < 0.05) in performance were evident in all fitness tests: CMJ (effect size [ES]: 0.61 to 1.03), SLCMJ (ES: 0.60 to 2.25), linear speed (ES: -0.54 to -1.96), and COD speed (ES: -0.68 to -1.14). Significant reductions in asymmetry (ES: -0.68 to -1.07) and significant increases in the BLD (ES: 1.15 to 1.57) were also evident throughout the season. Additionally, kappa coefficients were used to determine consistency in limb dominance throughout the season, but only poor to fair levels of agreement (kappa: -0.17 to 0.37) were evident, highlighting the fluctuating nature of limb dominance throughout the season. Despite all tests exhibiting meaningful change, the SLCMJ and linear speed showed the most frequent and largest differences in performance, highlighting their usefulness in the ongoing monitoring process of physical capacities in elite male academy players across a competitive soccer season.



#3 Relative age effect in Italian soccer. A cultural issue in talent management?

Reference: J Sports Med Phys Fitness. 2022 Apr 19. doi: 10.23736/S0022-4707.22.13663-7. Online ahead of print.

Authors: Bruno Ruscello, Gabriele Morganti, Gennaro Apollaro, Antonio Saponara, Mario Esposito, Lorenzo Marcelli, Cristoforo Filetti, Marco Porta, Alberto Grossi, Laura Pantanella

Summary: Relative Age Effect (RAE) is a well-known phenomenon among those involved in youth sports, especially when the sport being investigated is widespread and involves early selection for participation in national and international competitions. The purpose of this study was to verify whether the Italian youth soccer ecosystem has adapted to this issue over the years, comparing players born in 1995 and in 2005 and been playing in Under 16 teams in the appropriate years. The sample included 13 professional Italian soccer teams. The number of players analysed was 260 (1995) and 344 boys (2005), respectively, making a total of 604 players enrolled in this study. Relative age effects were detected by chi-square (χ²) goodness of fit tests both in players born in 1995 (p<0.000;V=0.40) and in 2005 (p<0.0001;V=0.39). χ² test of independence showed no significant difference between the two groups of players (p=0.986;V=0.02), confirming a substantial parity of the phenomenon over the two investigated birth years. Ten years of research and dissemination of RAE did not change the selection policies adopted by coaches and/or scouts, who favor relatively older players during the selection processes. Therefore, RAE appears as the result of the Talent Identification and Development Structures, characterized by early selection and early specialization, and which consider performance as the pre-requisite for gaining access to the next developmental stages. Sport organizations should be aware of this issue and counteract accordingly, since it is important to mitigate the presence of RAE, as it causes inequality of opportunity.



#4 An Assist for Cognitive Diagnostics in Soccer: Two Valid Tasks Measuring Inhibition and Cognitive Flexibility in a Soccer-Specific Setting With a Soccer-Specific Motor Response

Reference: Front Psychol. 2022 Mar 31;13:867849. doi: 10.3389/fpsyg.2022.867849. eCollection 2022.

Authors: Lisa Musculus, Franziska Lautenbach, Simon Knöbel, Martin Leo Reinhard, Peter Weigel, Nils Gatzmaga, Andy Borchert, Maximilian Pelka

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Summary: In professional soccer, players, coaches, and researchers alike recognize the importance of cognitive skills. Research addressing the relevance of cognitive skills has been based on the cognitive component skills approach (i.e., general cognitive processes) or the expert performance approach (i.e., sport-specific cognitive processes). Our project aimed to combine the strengths of both approaches to develop and validate cognitive tasks measuring inhibition and cognitive flexibility in a soccer-specific setting with a soccer-specific motor response. In the main study 77 elite youth soccer players completed a computerized version of the standard flanker and number-letter tasks as well as flanker and number-letter tasks requiring a soccer-specific motor response (i.e., pass) in a soccer-specific setting (i.e., the SoccerBot360). Results show good reliability for both tasks. For the SoccerBot360 number-letter task, switch effects for response times and accuracy and acceptable convergent validity were shown. A flanker effect for response time but not accuracy was apparent. Due to no acceptable convergent validity, the flanker task was revised (i.e., adaptation of stimuli) and 63 adult soccer players participated in a follow-up validation study in the SoccerBot100. The revised flanker task showed the flanker effect for response time, but not for accuracy. However, acceptable convergent validity for response time was present. Thus, the soccer-specific number-letter and to some extent the soccer-specific flanker task show potential to be used as a valid cognitive diagnostic tool by soccer clubs.



#5 Pelvic incidence and osteitis pubis in professional soccer players

Reference: Acta Ortop Bras. 2022 Jan 28;30(1):e244380. doi: 10.1590/1413-785220223001e244380. eCollection 2022.

Authors: Fernando Mansano Rodrigues, Atul Kumar Taneja, Erica Narahashi, Flavio Duarte Silva, Artur Rocha Corrêa Fernandes, Guilherme G Falotico, André Fukunishi Yamada

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Summary: Osteitis pubis is a common inflammatory disease of the pubic symphysis, defined as a chronic pain syndrome caused by repetitive microtrauma. Since adaptative changes are necessary in the pelvis to adjust the equilibrium of the myotendinous structures, the aim of this study was to evaluate the correlation between pelvic incidence and osteitis pubis among professional soccer players. An observational, cross-sectional study was performed with professional soccer players from five teams during pre-season. Athletes with previous congenital pelvic abnormalities or a history of surgery were excluded. Radiographs of the pelvis were analyzed by two radiologists and assessed for findings consistent with osteitis pubis, and the following parameters were measured: pelvic incidence (PI), sacral inclination (SI), and pelvic version (PV). A total of 107 subjects were included in the study, with a mean age of 25.6 ± 3.1 years. Findings compatible with osteitis pubis were present in 74.8% of the subjects (80/107). There was no statistical correlation between osteitis pubis and PI (52.3°±12.7° vs. 48.4°±10.8°; p=0.156), SI (43.1°±9.8° vs. 39.9°±10.1°; p=0.146), or PV (9.2°± 6.3° vs 8.6°± 7.5°; p=0.649). Agreement between readers was excellent (p<0.0001). There was no significant correlation between pelvic parameters and radiographic diagnosis of osteitis pubis. 



#6 Visual strategies of young soccer players during a passing test - A pilot study

Reference: J Eye Mov Res. 2022 Feb 21;15(1):10.16910/jemr.15.1.3. doi: 10.16910/jemr.15.1.3. eCollection 2022.

Authors: Pieter Vansteenkiste, Matthieu Lenoir, Izabela Krejtz, Krzysztof Krejtz

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Summary: In sports, studies on visual behavior have mostly focused on expert-novice differences during decision making tasks and during aiming tasks. How visual behavior changes during the early stages of skill acquisition however, has hardly been documented. The current study investigated gaze behavior of young soccer players during the execution of a soccer passing task. Gaze behavior of eleven 8- to 10-year-old soccer players was recorded while they performed the Loughborough Soccer Passing Test. Based on their score, participants were then divided into a high performance group (N=5), and a low performance group (N=6). Results showed that the low performance group tended to look more at the ball while they were handling it. These findings suggest that gaze strategies develop alongside technical skills. More insights in the interplay between technical skills and gaze strategies during skill acquisition could lead to improved training methods for young soccer players.



#7 Is There a Sex Difference in Technical Skills among Youth Soccer Players in Norway?

Reference: Sports (Basel). 2022 Mar 29;10(4):50. doi: 10.3390/sports10040050.

Authors: Arne Sørensen, Emma C Haugen, Roland van den Tillaar

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Summary: Female soccer has recently experienced an impressive increase in the number of players, and an impressive improvement in the quality of elite matches. Still, studies show sex differences in match statistics on passing accuracy and the ability to control the ball in international matches, which is explained by a lower skill of level in female soccer players as compared to male players. Therefore, the aim of this study was to evaluate if female youth soccer players had bridged the gap in technical skills to reach the level that boys have traditionally attained. Sixteen male and 17 female youth soccer players of the same age and experience level took part in technical skill tests of reception of the ball on the ground and long passes. The results show a significant difference between the sexes in reception performance in favour of the male players (p &lt; 0.05, ES = 1.09), but no significant difference in the long pass test (p = 0.11, ES = 0.43). This leads to the conclusion that the lower score on ball reception is probably the result of experience in small-sided self-organised soccer games during childhood among the male players, which influences reception skills but not the ability to make accurate long passes.



#8 An Examination of the Experiences of Practitioners Delivering Sport Psychology Services within English Premier League Soccer Academies

Reference: Sports (Basel). 2022 Apr 13;10(4):60. doi: 10.3390/sports10040060.

Authors: Francesca Dean, Emma Kavanagh, Amanda Wilding, Tim Rees

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Summary: Sport psychology has become increasingly recognized and accepted within professional sports, including soccer. To date, there is a lack of research that examines the provision of sport psychology within elite soccer, particularly from the experience of applied practitioners working within the field. The current study adopted a qualitative, inductive approach, to examine the experiences of practitioners responsible for sport psychology delivery within elite soccer academies in England. Seven participants (four females; three males), working within academies in the English Premier League, took part in semi-structured interviews about their experience of delivering sport psychology services within elite soccer academies. Results demonstrated that the provision of sport psychology is continually evolving, yet there are a number of factors that appear to inhibit the full integration of the discipline into academy soccer. Six key themes were identified: The breadth of sport psychology provision; what is sport psychology; the stigma surrounding sport psychology services; psychological literacy; the elite youth soccer environment; and the delivery of sport psychology under the Elite Player Performance Plan. Participants identified a lack of psychological literacy among coaches and academy staff, as well as a low level of guidance regarding the provision of psychology within the England Football Association's guiding document-the Elite Player Performance Plan-leading to considerable variation in the nature of the sport psychology provision. Future research would do well to also sample from a range of staff working within English soccer academies, in order to assess their perception of the level of provision and understanding of psychology.



#9 Relationships between Fitness Status and Blood Biomarkers in Professional Soccer Players

Reference: J Healthc Eng. 2022 Apr 11;2022:5135817. doi: 10.1155/2022/5135817. eCollection 2022.

Authors: Ana Filipa Silva, Francisco Tomás González-Fernández, Halil Ibrahim Ceylan, Rui Silva, Saeid Younesi, Yung-Sheng Chen, Georgian Badicu, Paweł Wolański, Eugenia Murawska-Ciałowicz, Filipe Manuel Clemente

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Summary: Physical conditions are recognized to be optimal after the pre-season (PS) phase in professional sports. Given that blood measures may also reveal variations, which in turn, may present associations with fitness changes. The aim of this study is to test the changes of blood markers and physical fitness outcomes at the beginning and following the PS phase. Additionally, we aimed also to analyze the associations of training adaptations between blood markers and the physical fitness measures.  25 professional male soccer players (28.1 ± 4.6 years old, 2.0 ± 7.8 kg, and 176.7 ± 4.9 cm) were assessed for hematological and biochemical parameters, and physical fitness measures in the baseline and after the phase of PS. Increases in platelets were observed after the PS phase (p = 0.001, η2 = 0.39). Regarding the biochemical parameters, significant increases between PS were found for creatinine (Cre) (p = 0.001, η2 = 0.66), alkaline phosphatase (ALP) (p = 0.001, η2 = 0.79), C-Reactive Protein (CRP) (p = 0.001, η2 = 0.74), cortisol (C) (p = 0.001, η2 = 0.63), and testosterone (T) (p = 0.001, η2 = 0.76), whereas significant decreases were found for albumin (Alb) (p = 0.004, η2 = 0.29), and calcium corrected (Ca Corr.) (p = 0.002, η2 = 0.32). Moderate correlations were found between albumin and the 5-meter linear sprint split (r = -0.44 (95%CI: -0.71; -0.05)) and CRP (r = -0.48 (95%CI: -0.74; -0.10)). Moderate correlations were found between VAMEVAL and hemoglobin (r = 0.44 (95%CI: 0.05; 0.71)). The overall physical fitness measures improved after the PS phase. Also, significant variations (decreases/increases) were observed for the case of biomchemical and hematological outcomes. Coaches should carefully consider the adaptative changes observed in blood parameters as the changes in whole organism and metabolism after specific critical phases as the PS in professional players. Thus, optimal management of stimulus/recovery can be warranted to minimize illness and injury rate and to follow the direction and dynamics of adaptative changes.



#10 Physiological and Sprint Kinetics Associated With the Yo-Yo Intermittent Recovery Test Level 1 Performances in Soccer Players

Reference: Int J Sports Physiol Perform. 2022 Apr 22;1-9. doi: 10.1123/ijspp.2021-0483. Online ahead of print.

Authors: Mark Kramer, Martinique Sparks, Ben Coetzee

Summary: The Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) is often utilized to indirectly assess the cardiorespiratory fitness of team-sport athletes due to its proposed association with match-play high-speed running performance and predicted maximal oxygen uptake. No previous research has investigated the relationships between YYIR1 performances, actual oxygen uptake recorded during the YYIR1, and true all-out sprint kinetics (eg, maximal sprint speed, maximal force capacity, and maximal power output), which therefore served as the primary objective of this study. The aim was to assess the true physiological kinetics (V˙O2 and heart-rate responses) during the YYIR1 and to evaluate the correlations between the physiological kinetics, sprint kinetics, and YYIR1 performance parameters. A total of 23 amateur male soccer players were recruited for the study (age 22.52 [2.86] y; height 1.75 [0.06] m; body mass 65.61 [8.43] kg). Each participant completed a YYIR1 and 2 all-out sprint tests. Significant differences were observed between actual and predicted maximal oxygen-uptake values (Mdiff = 17.57 mL·kg-1·min-1, P < .001, r = .63). Shuttle distances showed statistically significant correlations with maximal sprint speed (r = .42, P = .044) and theoretic maximal speed (r = .44, P = .035). However, no other correlations with sprint kinetic parameters (eg, maximal force or power output) were observed. Practitioners should carefully consider the outcomes and utilities of the parameters derived from the YYIR1. The estimations of maximal oxygen uptake from shuttle performances as a proxy for cardiorespiratory fitness are not adequate. However, shuttle distances appear to be positively associated with all-out sprinting capacities.



#11 Management of FAIS in professional soccer athletes and return to sports

Reference: Orthopade. 2022 Apr 28. doi: 10.1007/s00132-022-04257-2. 

Authors: Stefan Budde, Marco Ezechieli

Summary: The prevalence of femoroacetabular impingement syndrome in professional soccer athletes is high. Professional training and treatment conditions ensure an effective conservative therapy focusing on dynamic stability, motion control, muscle balance and core stability. In the case of persistent limitations, indication for surgery has to be considered carefully. The probability is high that return to a professional level of soccer is feasible. However, the period of rehabilitation is long, leading to a potential conflict area between economic and medical interests. Good communication and intensive patient education are essential.



#12 Quantifying technical actions in professional soccer using foot-mounted inertial measurement units

Reference: Sci Med Footb. 2022 May;6(2):203-214. doi: 10.1080/24733938.2021.1910333. Epub 2021 Apr 22.

Authors: Joshua Marris, Steve Barrett, Grant Abt, Chris Towlson

Summary: This study aimed to (i) establish the concurrent validity and intra-unit reliability of a foot-mounted inertial measurement unit for monitoring soccer technical actions, (ii) quantify the within-microcycle inter-positional differences in the technical actions of professional soccer training, and (iii) determine the influence of drill category on the technical actions of professional soccer training. Twenty-one professional soccer players' technical performance data (ball touches, releases, ball touches per minute, releases per minute), collected during training sessions throughout twenty-four weekly microcycles, were analysed using general linear modelling. The inertial measurement unit exhibited good concurrent validity (PA = 95.1% - 100.0%) and intra-unit reliability (PA = 95.9% - 96.9%, CV = 1.4% - 2.9%) when compared with retrospective video analyses. The most ball touches and releases were observed on MD - 1, with MD - 5 eliciting the highest frequency of ball touches and releases per minute. Central midfielders performed the most ball touches, releases, ball touches per minute and releases per minute. Small-sided games evoked more ball touches and releases per minute than previously reported in match-play. The fewest ball touches and releases per minute were observed during tactical drills. The results of this study provide a novel understanding of the within-microcycle, inter-positional and drill category differences in the technical actions performed by professional players during training.



#13 Endoscopic curettage and allografting of simple bone cysts of the calcaneus in young soccer players: Report of three cases

Reference: Foot (Edinb). 2021 Sep 25;51:101868. doi: 10.1016/j.foot.2021.101868. Online ahead of print.

Authors: Ioannis Terzidis, Theodorakys Marín Fermín, Efthymios Papasoulis, Trifon Totlis, Emmanouil Papakostas, Aristotelis Sideridis

Summary: Open curettage with bone graft has been the traditionally suggested surgical treatment for the symptomatic simple (or unicameral as they used to be called) calcaneal bone cyst. Less invasive endoscopically assisted treatment with curettage and bone grafting with allograft have recently provided less postoperative morbidity. The aim of the present study is to present our experience with this method in young soccer athletes. Between April 2014 and May 2016 three consecutive young soccer players with symptomatic calcaneal bone cysts underwent endoscopic curettage, and percutaneous injection of demineralized bone matrix allograft. The mean age was 17.3 (16, 17 and 19 years old), and the mean follow-up was 32.1 (range 24-47) months. Both radiographic and functional follow-up, using the AOFAS score, showed good to excellent results. All lesions were radiographically healed. Preoperative AOFAS score (max. 100 pts) was 78.6 ± 4.7, improving to 98.0 ± 4.1. The patients returned to their initial level of sports activities within 18.3 (range 17-19) weeks after surgery. Evidence suggests an earlier return to sports using bone substitutes. However, the present study showed that endoscopic curettage and percutaneous injection of bone allograft is also an excellent treatment option for young athletes with a symptomatic calcaneal bone cyst.



#14 Inter-methodological quantification of the target change for performance test outcomes relevant to elite female soccer players

Reference: Sci Med Footb. 2022 May;6(2):248-261. doi: 10.1080/24733938.2021.1942538. Epub 2021 Jun 27.

Authors: Naomi Datson, Lorenzo Lolli, Barry Drust, Greg Atkinson, Matthew Weston, Warren Gregson

Summary: Valid and informed interpretations of changes in physical performance test data are important within athletic development programmes. At present, there is a lack of consensus regarding a suitable method for deeming whether a change in physical performance is practically relevant or not. We compared true population variance in mean test scores between those derived from evidence synthesis of observational studies to those derived from practioner opinion (n = 30), and to those derived from a measurement error (minimal detectable change) quantification (n = 140). All these methods can help to obtain 'target' change score values for performance variables. We found that the conventional 'blanket' target change of 0.2 (between-subjects SD) systematically underestimated practically relevant and more informed changes derived for 5-m sprinting, 30-m sprinting, CMJ, and Yo-Yo Intermittent Recovery Level 1 (IR1) tests in elite female soccer players. For the first time in the field of sport and exercise sciences, we have illustrated the use of a principled approach for comparing different methods for the definition of changes in physical performance test variables that are practically relevant. Our between-method comparison approach provides preliminary guidance for arriving at target change values that may be useful for research purposes and tracking of individual female soccer player's physical performance.



#15 An audit of hormonal contraceptive use in Women's Super League soccer players; implications on symptomology

Reference: Sci Med Footb. 2022 May;6(2):153-158. doi: 10.1080/24733938.2021.1921248. Epub 2021 May 16.

Authors: Lloyd J Parker, Kirsty J Elliott-Sale, Marcus P Hannon, James P Morton, Graeme L Close

Summary: The aim was to audit hormonal contraceptive use and associated symptomology in elite women's soccer in England. Seventy-five elite women's soccer players from the Women's Super League (WSL) completed a questionnaire to assess: hormonal contraceptive (HC) use or non-use, reasons for initiation and discontinuation and the symptoms experienced by HC and non-HC users. Twenty-eight per cent reported current HC use, with 43% having used HCs previously. Combined HCs accounted for 62% of total usage, with progestin-only HCs making up the remainder. Eighty-six per cent pre-empted negative symptoms before commencing HCs, with 38% experiencing adverse symptoms. Negative symptoms were most common in progestin-only HC users (63%). Eighty-six per cent reported benefits associated with HC usage include pain management and the ability to predict or control their cycles. Six non-HC users reported amenorrhea, with one medically diagnosed. Negative MC-related symptoms were reported by 74%, with 4% unable to train due to these symptoms. Unfavorable symptoms typically occurred during the first days of menstruation (59%). Most WSL players do not currently use HCs (72%). Most HC users reported benefits of HC usage, whilst most non-HC users reported negative symptoms especially around menstruation. Practitioners should track players' MCs to help minimise discomfort and maximise performance.



#16 Collective behaviour in high and low-level youth soccer teams

Reference: Sci Med Footb. 2022 May;6(2):164-171. doi: 10.1080/24733938.2021.1917774. Epub 2021 Jul 22.

Authors: Jade O'Brien-Smith, Job Fransen, William B Sheehan, Matthieu Lenoir, Kyle Bennett, Mitchell R Smith

Summary: An expert/non-expert paradigm often helps understand the underpinnings of sports expertise; however, this method is scarcely extended to the complexities of collective behaviour in youth soccer. Therefore, the objectives of the current study are to investigate differences in the collective behaviour of youth soccer teams by expertise level. Soccer players aged 15 to 20 years from high (n = 35) and low (n = 40) playing levels competed in two age-matched 5v5 small-sided games. For each game, teams' skill involvement (shot, pass, dribble, touch), passing networks (closeness, density, betweenness), and spatiotemporal characteristics (stretch index, effective area, length (L) & width (W), LpW ratio, synchrony) were measured using video footage and GPS coordinates. High level teams had more attempted (p = .009), and completed skills (p = .003), particularly for the number of passes (p = .001) and shots (p = .012-.045). However, there were no significant between-group differences for either the passing networks or spatiotemporal characteristics. The findings from the current research suggest that the high-level teams can quickly and effectively move the ball within existing team structures and may better optimise their afforded space to execute desired skills when compared to the low-level teams.



#17 Quantifying change of direction load using positional data from small-sided games in soccer

Reference: Sci Med Footb. 2022 May;6(2):234-240. doi: 10.1080/24733938.2021.1912382. Epub 2021 Apr 15.

Authors: Brenda M T Merks, Wouter G P Frencken, A R Den Otter, Michel S Brink

Summary: Quantifying change of direction (COD) load through positional data from small-sided games (SSG) and assess its criterion and construct validity. Elite male youth soccer players (n = 25, 16.8 ± 1.3 years) played three SSG (5v5, 5×4 min) with different field dimensions (small [40×30 m], medium [55×38 m], large [70×45 m]). Positional data of the players was obtained with a Local Position Measurement system. COD load (AU) was quantified based on the combination of velocity and change in heading direction. Additionally, total distance covered, running distance, acceleration count, deceleration count, and Rating of Perceived Exertion were measured. Criterion validity was assessed by correlating COD load and the load indicators. Construct validity was determined by testing the differences between the SSG field dimensions. Strong correlations were determined between COD load and total distance covered (r = 0.74, p < .01) and running distance (r = 0.84, p < .01). Middle and large field size resulted in highest COD load (p < .05). These results suggest that the COD load measure shows sufficient criterion and construct validity.



#18 Fundamental movement skills and perceived competence, but not fitness, are the key factors associated with technical skill performance in boys who play grassroots soccer

Reference: Sci Med Footb. 2022 May;6(2):215-220. doi: 10.1080/24733938.2021.1910332. Epub 2021 Apr 7.

Authors: Michael Duncan, Emma L J Eyre, Mark Noon, Rhys Morris, Doug Thake, Neil Clarke

Summary: This study examined the association between fitness, fundamental movement skills (FMS) and perceived competence on technical skills in boys engaged in grassroots soccer. Methods: Sixty boys (8-12 years of age, Mean ± SD = 10 ± 1 years) undertook assessment of FMS, perceived competence, physical fitness (15m sprint speed, standing long jump distance and seated 1kg medicine ball throw as a composite z-score) and technical skills (dribbling, passing and shooting as a composite z-score). Multiple backwards linear regression was used to determine to amount of variance in technical skill explained by FMS, perceived competence and fitness. Results indicated a significant model (F 3,58= 42.04, P = .0001, Adj R2 = .680) which explained 68% of the variance in technical skills. Perceived competence (β=.316, P =.001), Total FMS (β=.140, P =.002), and chronological age (β=.863), P =.001) significantly contributed to the model. This study demonstrates that better technical skills (passing, dribbling, shooting) in youth soccer are explained, alongside age, by being competent in FMS and having a more positive perception of competence. Coaches should therefore seek to encourage development of these factors during childhood for the benefit of technical skill performance.



#19 The influence of relative playing area and player numerical imbalance on physical and perceptual demands in soccer small-sided game formats

Reference: Sci Med Footb. 2022 May;6(2):221-227. doi: 10.1080/24733938.2021.1939408. Epub 2021 Jun 11.

Authors: Andrew N Guard, Kenneth McMillan, Niall G MacFarlane

Summary: This study aimed to examine physiological, mechanical and perceptual loading in small-sided games using different relative playing areas with balanced and unbalanced player numbers. Data were collected in twelve elite youth male soccer players and included heart rate and standard time-motion outputs using commercial GPS. The data demonstrated higher cardiovascular, physical and perceptual demands with increasing pitch size (e.g. average HR was 88.7 vs. 86.7% HRmax with 8 vs. 2 high-intensity acceleration in medium vs. small pitch formats. The largest pitch format resulted in a greater accumulation of high-intensity distance (47 ± 30 m), higher peak velocity (25.2 ± 1.6 km.h-1) and a higher distance and frequency of accelerations (35 ± 9 m and 8 ± 3) compared with the smallest pitch (all p < 0.01). In unbalanced games, there was significantly greater average heart rate in the overloaded team (84.4 ± 4.9 vs. 80.4 ± 4.8% HRmax in 4 v. 6). These data suggest that different game formats including numerical imbalance could be prescribed for squad management to target conditioning stimuli for specific players (e.g. to target a higher training load for players that do not get consistent match exposure).



#20 Variations in the relative age effect with age and sex, and over time-Elite-level data from international soccer world cups

Reference: PLoS One. 2022 Apr 28;17(4):e0264813. doi: 10.1371/journal.pone.0264813. eCollection 2022.

Authors: Arve Vorland Pedersen, Tore Kristian Aune, Terje Dalen, Håvard Lorås

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Summary: The relative age effect (RAE) is a statistical bias observed across sport contexts and consists of a systematic skewness in birth date distribution within an annual-age cohort. In soccer, January 1st is the common cut-off date when categorizing players in competitions according to their chronological age, which potentially disadvantages those within the cohort who were born later in the year. Thus, relatively older soccer players in their cohort can be favored in talent identification, selection, and development. The aim of the current study was to investigate the variations in RAE in male and female international youth world-cup tournaments (U17 and U20) in the period from 1997-2019 and in international senior world-cup-tournaments from 2006-2019. A total of 20,401 soccer players participating in 47 different tournaments were analyzed. The birthdate distributions were categorized into four quartiles (January-March, Q1; April-June, Q2; July-September, Q3; October-December, Q4) and compared to a uniform distribution using Chi-square analysis with Cramer's V (Vc) as a measure of effect size. Based on the existing data concerning RAE in elite junior and senior soccer, it was hypothesized that: (I) the RAE is present in youth soccer world cup tournaments but is stronger in male players than in female players; (II) the younger the soccer players, the stronger the RAE; and (III) the RAE in world cup soccer tournaments has strengthened over time. All these hypotheses were supported by the data; novel findings included that the effect has now entered women's soccer, and in men's soccer it persists into senior world cup tournaments. Thus, a strong RAE bias occurs in selection among elite soccer players competing in international world cup tournaments.



#21 Heading Exposure in Elite Football (Soccer): A Study in Adolescent, Young Adult, and Adult Male and Female Players

Reference: Med Sci Sports Exerc. 2022 Apr 25. doi: 10.1249/MSS.0000000000002945. Online ahead of print.

Authors: Shari Langdon, Edwin Goedhart, Jaap Oosterlaan, Marsh Königs

Summary: This study aims to quantify heading exposure in real-life elite football at the level of individual male and female adolescents, young adults and adults. Heading exposure was determined by video analysis in combination with a structured electronic registration tool and observation training, to comprehensively register heading characteristics. Characteristics of heading events were registered in 116 official matches (96 male, 20 female) of Dutch national teams. Mean exposure for male players based on full match participation was 4.2 headers, with maximum heading exposure at 10.6 headers. Mean heading exposure was higher in adult than adolescent players (p = .049), while maximum heading exposure was higher for adult than for young adult players (p = .045). Maximum heading exposure was higher in male than in female players (p = .015). Defenders had the greatest mean and maximum heading exposure (ps < .001). Longer flight courses of the ball had greater contribution to expected and maximum heading exposure than shorter courses (ps < .01). Frontal headers had greater contribution to exposure than other points of contact on player's head (ps < .001), while linear headers had greater contribution than rotational headers (p = .016). Defensive headers had greater contribution to exposure than other heading types (ps < .014). Unintentional head contacts in elite football players were in most cases (80%) not related to heading situations. This study provides real-life quantifications of expected and maximum heading exposure in elite football, with strong relevance for policy makers and researchers. The results highlight the roles of player and heading characteristics in heading exposure, informing current discussions on the role of heading in football.



#22 Relationships Between Internal and External Load Measures and Fitness Level Changes in Professional Soccer Players

Reference: Res Q Exerc Sport. 2022 Apr 29;1-13. doi: 10.1080/02701367.2022.2053646. Online ahead of print.

Authors: Marco Martin, Ermanno Rampinini, Andrea Bosio, Andrea Azzalin, Alan McCall, Patrick Ward

Summary: Understanding the dose-response relationship between internal and external training load with changes in aerobic fitness and intermittent running capacity, during different periods of the season, may help in optimizing training process. The aim of the present study was to investigate the dose-response relationships between load measures and changes in aerobic fitness and intermittent running capacity among a large cohort of professional soccer players.  Training load, aerobic fitness and intermittent running capacity of 52 male adult professional players from 3 elite teams were monitored across an entire season and analyzed employing linear mixed models, with a significance level set at p≤0.05.  Relationships between load measures (training and match duration, sRPE-TL, total distance, high and very high-speed running distances) and changes in physical qualities were stronger during the preparation period (PREP) for both aerobic fitness (d= 0.48 to 0.76, p<0.031) and intermittent running capacity (d= 0.46 to 1.89, p<0.046). The magnitude of the relationships reduced during the first competitive period (d= 0.43 to 0.56) and the relationships became trivial in the second competitive period (d= 0.06 to 0.41, p= 0.063 to 0.846).  The moderate to large relationships found between all measures of load and changes in physical capacities suggest that training prescription during the PREP was effective in improving players' fitness. During the competitive phase small changes in aerobic and intermittent running capacities were found, highlighting that coaching staff pursue different aims during the competitive period, such as technical and tactical training and recovery. .



#23 Accuracy of Tracking Devices' Ability to Assess Exercise Energy Expenditure in Professional Female Soccer Players: Implications for Quantifying Energy Availability

Reference: Int J Environ Res Public Health. 2022 Apr 14;19(8):4770. doi: 10.3390/ijerph19084770. 

Authors: Marcus S Dasa, Oddgeir Friborg, Morten Kristoffersen, Gunn Pettersen, Jorunn Sundgot-Borgen, Jan H Rosenvinge

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Summary: The purpose of the study was to assess the accuracy of commonly used GPS/accelerometer-based tracking devices in the estimation of exercise energy expenditure (EEE) during high-intensity intermittent exercise. A total of 13 female soccer players competing at the highest level in Norway (age 20.5 ± 4.3 years; height 168.4 ± 5.1 cm; weight 64.1 ± 5.3 kg; fat free mass 49.7 ± 4.2 kg) completed a single visit test protocol on an artificial grass surface. The test course consisted of walking, jogging, high-speed running, and sprinting, mimicking the physical requirements in soccer. Three commonly used tracking devices were compared against indirect calorimetry as the criterion measure to determine their accuracy in estimating the total energy expenditure. The anaerobic energy consumption (i.e., excess post-exercise oxygen consumption, EPOC) and resting time were examined as adjustment factors possibly improving accuracy. All three devices significantly underestimated the total energy consumption, as compared to the criterion measure (p = 0.022, p = 0.002, p = 0.017; absolute ICC = 0.39, 0.24 and 0.30, respectively), and showed a systematic pattern with increasing underestimation for higher energy consumption. Excluding EPOC from EEE reduced the bias substantially (all p's becoming non-significant; absolute ICC = 0.49, 0.54 and 0.49, respectively); however, bias was still present for all tracking devices. All GPS trackers were biased by showing a general tendency to underestimate the exercise energy consumption during high intensity intermittent exercising, which in addition showed a systematic pattern by over- or underestimation during lower or higher exercising intensity. Adjusting for EPOC reduced the bias and provided a more acceptable accuracy. For a more correct EEE estimation further calibration of these devices by the manufacturers is strongly advised by possibly addressing biases caused by EPOC.



#24 Individualized Analysis of Lateral Asymmetry Using Hip-Knee Angular Measures in Soccer Players: A New Methodological Perspective of Assessment for Lower Limb Asymmetry

Reference: Int J Environ Res Public Health. 2022 Apr 13;19(8):4672. doi: 10.3390/ijerph19084672.

Authors: Oscar García-García, Ángela Molina-Cárdenas, Tania Álvarez-Yates, Mario Iglesias-Caamaño, Virginia Serrano-Gómez

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Summary: This study aimed to: (1) determine the magnitude and direction of lateral asymmetry in well-trained soccer players using hip and knee ROM tests; (2) inquire if asymmetry relies on the ROM test performed and/or gender; and (3) establish asymmetry thresholds for each ROM test to individualize lower-limbs asymmetry. One hundred amateur soccer players were assessed using hip-knee ROM tests: Straight Leg Raise, modified Thomas Test, hip internal rotation and external rotation, hip abduction (ABD) and adduction (ADD), Nachlas Test and Rigde Test. There are significant differences between tests when determining the magnitude of lateral asymmetry (F = 3.451; p = 0.001; ηp2 = 0.031) without significant differences between gender (F = 0.204; p = 0.651; ηp2 = 0.001). Asymmetry threshold results differ significantly between using a fixed or a specific threshold (F = 65.966; p = 0.001; ηp2 = 0.985). All tests indicate that the direction of asymmetry is towards the dominant limb. In conclusion, the ROM test used determines the magnitude and direction of the lateral asymmetry of the amateur soccer players. The ABD and ADD are the ROM tests that showed higher percentages of asymmetry, without differences between female and male soccer players. Using a specific asymmetry threshold formula can classify more players as asymmetrical than with a fixed threshold.






Analysis of the Effect of Injuries on Match Performance Variables in Professional Footballers: A Retrospective, Longitudinal Design

This study aimed to analyze the changes in match performance parameters in professional soccer players after sustaining an injury, which was defined according to injury severity.





Recovery following the extra-time period of soccer: Practitioner perspectives and applied practices

Recovery following the extra-time period of soccer: Practitioner perspectives and applied practices.





Latest research in football - week 15 - 2022

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 Hypertrophic adaptations to a 6-week in-season barbell vs. flywheel squat added to regular soccer training

Reference: J Sports Med Phys Fitness. 2022 Apr 12. doi: 10.23736/S0022-4707.22.13793-X. Online ahead of print.

Authors: Cristoforo Filetti, Bruno Ruscello, Italo Leo, Marco Porta, Aldo Chiari, Carlos Miranda, Vincenzo Rago

Summary: The aim of this study was to compare the hypertrophic adaptations to barbell or flywheel squat exercise added to regular in-season soccer training. Quadriceps' (rectus femoris [RF], vastus medialis [VM] and vastus lateralis [VL]) cross-sectional area (CSA) in its portions (proximal [PROX], middle [MID], and distal [DIST]) was measured on both legs before and after a 6-week barbell (80 to 90 % one-maximum repetition; n=7) or flywheel (0.0611 to 0.0811 Kg·m2; n=7) in an U19 professional soccer team using a 3T magnetic resonance imagery. Both groups underwent 5 sets × 6 reps per session of squat separated by 3-min rest, while controlling the time under tension (within 0.5 and 0.8 s). The barbell squat group experienced moderate CSA increments in the VMMID and the VLDIST of the right leg (d=0.98-0.99). Additionally, the flywheel group experience large CSA increments in the RFMID, VLPROX and VLMID of the right leg (d=1.00-1.84). On average, flywheel squat training largely produced greater force during exercise compared to the barbell squat training (29.2 vs. 12.2 N·kg-1; d=5.95), whereas the barbell squat training produced moderately greater power output (10.5 vs. 9.7; d=0.52). Barbell squat training seems to be more effective for VM hypertrophy whereas flywheel squat triggers greater RF and VL hypertrophy as complementary to regular field-based soccer practice and competition within a short range of time (6 weeks) during the in-season. These findings can be considered also from either strength or reconditioning perspective based on the increase in the quadriceps muscles' CSA as mechanism underlying strength/power adaptations.



#2 Associations between match participation, maturation, physical fitness, and hormonal levels in elite male soccer player U15: a prospective study with observational cohort

Reference: BMC Pediatr. 2022 Apr 11;22(1):196. doi: 10.1186/s12887-022-03257-7.

Authors: Ebrahim Eskandarifard, Hadi Nobari, Filipe Manuel Clemente, Rui Silva, Ana Filipa Silva, Antonio José Figueiredo

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Summary: The aims of this study were to analyze the relationships between minutes of play (MP) and maturity status, fitness, and hormonal levels and to explain how those measures influence the time of play. Twenty-six youth soccer players U15 participated in this study over a full-season period. Anthropometric measures, maturity status, growth hormone (GH), insulin-like growth factor and physical levels such as maximal oxygen uptake (VO2max), fatigue index, countermovement jump (CMJ) performance were collected. At the end-season, players were assessed in 6 different tests over four days. VO2max largely correlated with GH (r = 0.57) and CMJ (r = 0.51). Also, GH largely correlated with CMJ (r = 0.55). MP had moderate correlations with VO2max (r = 0.44) and CMJ (r = 0.42). Multiple linear regression with maturation, physical fitness and hormonal levels explained R2 of 0.62 of the MP (F (8, 17) = 3.47, p = 0.015). Although each independent variable alone was not able to determine the playing time, when using the interactions, the model significantly explained the MP. The combination of maturity status, physical fitness, and hormonal levels seem to play a determinant role in explaining the match participation in youth soccer players.



#3 COVID-19 Confinement Effects on Game Actions during Competition Restart in Professional Soccer Players

Reference: Int J Environ Res Public Health. 2022 Apr 2;19(7):4252. doi: 10.3390/ijerph19074252.

Authors: Abraham García-Aliaga, Moisés Marquina, Ignacio Refoyo Román, Diego Muriarte Solana, Juan A Piñero Madrona, Roberto López Del Campo, Fabio Nevado Garrosa, Daniel Mon-López

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Summary: The main objective of the present study was to compare high-intensity actions in a week of three matches before and after the COVID-19 lockdown. The observational methodology was used. This study analysed 551 professional soccer players from 22 different Spanish teams (LaLiga Smartbank 2019-2020) by a multi-camera tracking system and associated software (Mediacoach®, Spain). Variables of distances per minute and totals, travelled at High Intensity (HIR), Very High Intensity (VHIR), Sprint (HSR), player's maximum speed, average speed, and the number of efforts in VHIR and HSR were analysed in the first and second half of the games, the full match, as well as in relation to the playing position. Players who participated in the same number of matches pre- and post-COVID-19 showed an increase in the total minutes played, p &lt; 0.05, and small decreases in game actions, p &lt; 0.05, with an effect size between 0.21 and 0.45, while players who participated in different number of matches pre- and post-COVID-19 showed a performance decrease, p &lt; 0.05, with a size effect between 0.13 and 0.51; this was evident, particularly, for midfielders, p &lt; 0.05, with a size effect between 0.39 and 0.75. The results seem to show that the playing intensity after COVID-19 confinement did not lead to large performance losses, except for midfielders who were the most involved players and showed a higher decrease in performance. The main findings of this study could provide insight to football coaches for rotations in starting line-ups and game substitutions, so as not to affect the intensity levels of the competitions.



#4 A Simple Field Tapping Test for Evaluating Frequency Qualities of the Lower Limb Neuromuscular System in Soccer Players: A Validity and Reliability Study

Reference: Int J Environ Res Public Health. 2022 Mar 23;19(7):3792. doi: 10.3390/ijerph19073792.

Authors: Safouen Chaabouni, Rihab Methnani, Badria Al Hadabi, Majid Al Busafi, Mahfoodha Al Kitani, Khalifa Al Jadidi, Pierre Samozino, Wassim Moalla, Nabil Gmada

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Summary: Over the years, the foot tapping test protocol has been proposed by scientists to identify the capabilities of the lower limb neuromuscular system in the medical context; however, to our knowledge, no studies have established its usefulness and relationship to athletic performance. The aim of the present study was to test the reliability, criterion validity and sensitivity of a new foot tapping (TAP) test, and to examine its relationship with proxies of athletic performance in soccer players. Forty voluntary soccer players of two different levels participated in this study (20 players from the national level: age: 22.6 ± 2.5 years and 20 players from regional level: 25.1 ± 3.6 years). They performed the TAP test on two separate occasions to test its relative and absolute reliability. To examine the criterion validity of the TAP test, all participants performed four types of jumps, sprint tests, agility tests, the Wingate test and the finger tapping test considered a gold standard tapping test. The sensitivity was assessed with national and regional player levels. The TAP test presented a high relative and absolute reliability with intra-class correlation coefficient ICC &gt; 0.90, standard errors of measurement SEM &lt; 5% and mean difference ±95% limits of agreement equal to 0.2 ± 0.8 tap·s-1. National level players showed a higher TAP score (p &lt; 0.001; dz = 1.96, large) compared to regional players (9.68 ± 1.41 tap·s-1 vs. 7.28 ± 1.01 tap·s-1, respectively) and the value of area under curve measured by the receiver operating characteristic curve technique was 0.95 (95% CI: 0.827-0.990). The TAP test showed a significant association with the finger tapping test (r = 0.84, p &lt; 0.001), whereas no correlation was seen between the TAP test and all the other physical tests measured. The TAP test could be considered a valid and reliable test to assess lower limb neuromuscular ability in soccer players.



#5 Sports Performance Tests for Amputee Football Players: A Scoping Review

Reference: Int J Environ Res Public Health. 2022 Apr 6;19(7):4386. doi: 10.3390/ijerph19074386.

Authors: Agnieszka Magdalena Nowak, Jolanta Marszalek, Bartosz Molik

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Summary: This scoping review aims to identify sports performance tests for amputee football players and to critically analyze the methodological quality, validation data, reliability, and standardization of sport-specific tests to indicate the best-fitting tests. Electronic database searches were conducted between January 2019 and October 2021. Twelve articles met the inclusion criteria. Qualitative assessment of each study was conducted by STROBE checklist. Twenty-nine sports performance tests were identified. No sports performance test fully met all three criteria associated with the qualitative assessment of tests. The critical appraisal of the articles demonstrates a gap in study design, settings, and main results description. Some inconsistencies were found in the methodological descriptions of tests assessing the same motor skill. A STROBE score of 13 points was considered a satisfactory score for the article (it was obtained by 8 of the 12 studies). The weakest point of the analyzed studies was the description of how the test group size was accessed and later obtained. No test was found that was simultaneously presented as valid, reliable, and standardized. The authors can recommend the use of the two-sports performance tests that are the closest to ideal: the L test and the YYIRT1.



#6 The Relationship between Different Large-Sided Games and Official Matches on Professional Football Players' Locomotor Intensity

Reference: Int J Environ Res Public Health. 2022 Apr 1;19(7):4214. doi: 10.3390/ijerph19074214.

Authors: Romualdo Caldeira, Élvio Rúbio Gouveia, Andreas Ihle, Adilson Marques, Filipe Manuel Clemente, Helder Lopes, Ricardo Henriques , Hugo Sarmento

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Summary: Large-sided games (LSG) are commonly used in the training contexts for providing either technical/tactical or locomotor/physiological stimuli. Despite natural similarities with the official match, the locomotor profile seems to be different, which must be considered by the coaches to identify compensatory strategies for achieving the ideal dose of training. The aim of this study was two-fold: (1) to investigate the locomotor demands imposed by LSGs and the official matches; and (2) to compare the effect of different pitch sizes' LSG conditions in the locomotor demands. This study followed an observational design. Sixteen professional football players from the same team (26.3 ± 3.0 years old) were included. The study was conducted over four weeks. The same GK + 10 × 10 + GK play format with different pitch sizes (i.e., area per player ranging between 195 m2 to 291 m2) was analyzed. Three official matches were also collected in which the 10 most demanding minutes were considered for further comparisons. Only the same players who participated in matches were considered in comparison with the LSG. The data were obtained using a 10-Hz global positioning system technology. Total distance (TD) and mechanical work (MW) scores increased 20% and 23%, respectively, between the smallest and biggest pitch sizes (p &lt; 0.001). There was a significant difference in locomotor intensity metrics between opponents from different positions on the table (p = 0.001). The biggest LSG (i.e., 291 m2 per player) was the only one that required similar levels of locomotor intensity as required in the official full match. The present study demonstrates that LSG pitch size variation requires different locomotor intensities. Bigger pitch sizes cause an increase in TD and MW. In addition, considering the position on the table, the level of opponents induces different TD covered. Finally, the largest LSG simulates the official match more accurately.



#7 Reliability of a Qualitative Instrument to Assess High-Risk Mechanisms during a 90° Change of Direction in Female Football Players

Reference: Int J Environ Res Public Health. 2022 Mar 31;19(7):4143. doi: 10.3390/ijerph19074143.

Authors: Alba Aparicio-Sarmiento, Raquel Hernández-García, Antonio Cejudo, José Manuel Palao, Pilar Sainz de Baranda

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Summary: Sidestep cuts between 60° and 180° and one-leg landings have been identified as the main mechanisms of ACL injuries in several sports. This study sought to determine intra- and inter-rater reliability of a qualitative tool to assess high-risk movements in a 90° change of direction when the test is applied in a real framework of sport practice. Female footballers from two teams (n = 38) participated in this study and were asked to perform 90° cutting trials to each side, which were simultaneously filmed from a frontal and a sagittal view. A total of 61 cases were selected for 2D qualitative observational analysis by three raters. Poor reliability was found among each pair of raters as well as moderate reliability when the Cutting Movement Assessment Score (CMAS) was given by the same rater at different moments, but with too high a minimum detectable change. On the other hand, raters presented a significant, as well as moderate-to-good intra-rater reliability for most items of the CMAS tool. There was, however, non-significant reliability between observers in rating most check-points of the tool. For these reasons, more objective guidelines and clearer definitions for each criterion within the CMAS, as well as a longer, standardised training period for novel observers, would be highly recommended to improve the reliability of this tool in an applied context with female footballers.



#8 Intra and Inter-Observer Reliability and Repeatability of Metatarsus Adductus Angle in Recreational Football Players: A Concordance Study

Reference: J Clin Med. 2022 Apr 6;11(7):2043. doi: 10.3390/jcm11072043.

Authors: Eduardo Pérez Boal, Carlos Martin-Villa, Ricardo Becerro de Bengoa Vallejo, Marta Elena Losa Iglesias, Bibiana Trevissón Redondo, Israel Casado Hernández, César Calvo Lobo, David Rodríguez Sanz

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Summary: Metatarsus adductus (MA) is a congenital foot deformity often unrecognized at birth. There is adduction of the metatarsals, supination of the subtalar joint, and plantarflexion of the first ray. The aims of this study were to assess the intra and inter-reader reliability of the radiographic MA measurement angles used in the literature. All consecutive recreational football players who practice activity more than 5 h/week over 21 years of age with MA by roentgenographic evaluation on weight-bearing dorsoplantar images were included in a cross-sectional study. Controls were matched to cases according to age and gender. We assess all radiographic measurements to evaluate metatarsus adductus with the different measurements frequently used in the literature: Sgarlato, modified Sgarlato, Rearfoot, Root, Engel, modified Engel, Kite, Kilmartin, modified Kilmartin, Simons, and Laaveg & Ponseti. The variables measured in 80 weight-bearing dorsoplantar foot radiographs show excellent reliability ranging p &gt; 0.900 in Sgarlato and modified Sgarlato with low SEM, CV, and MCD. Rearfoot, Root, Engel, modified Engel, Kite, Kilmartin, Simons, Laaveg & Ponseti, and modified Kilmartin's angles showed intra or inter reliability with ICC lower than &lt;0.900, systematic differences between intersession or inter observers, or high MCD value. It is more suitable to measure the MA angle with the Sgarlato and modified Sgarlato techniques to show higher reliability and repeatability for intra and inter-observer.



#9 The Effect of Acute Caffeine Ingestion on Tactical Performance of Professional Soccer Players

Reference: Nutrients. 2022 Mar 31;14(7):1466. doi: 10.3390/nu14071466.

Authors: Rodrigo Freire de Almeida, Israel Teoldo da Costa, Guilherme Machado, Natalia Madalena Rinaldi, Rodrigo Aquino, Jason Tallis, Neil David Clarke, Lucas Guimaraes-Ferreira

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Summary: In soccer, physical, tactical, and decision-making processes are highly important facets of successful performance. Caffeine has well established effects for promoting both physical and cognitive performance, but the translation of such benefits specifically for soccer match play is not well established. This study examined the effects of acute caffeine ingestion on tactical performance during small-sided games (SSG) in professional soccer players. Nineteen soccer players (22 ± 4 years) underwent a randomized, counterbalanced, crossover, double-blind placebo-controlled trial. The protocol consisted of 5 bouts of 5-min SSG with 3 players plus a goalkeeper in each team (3 + GK × 3 + GK) with each SSG separated by 1 min rest intervals. Tactical performance was assessed using the system of tactical assessment in soccer (FUT-SAT). Prior to each experimental trial, participants ingested caffeine (5 mg·kg-1) or a placebo 60 min before the protocol. Overall, caffeine ingestion resulted in an increased ball possession time when compared to the placebo. When the offensive and defensive core principles were analyzed, the results were equivocal. Caffeine resulted in positive effects on some tactical decisions during the protocol, but it was deleterious or promoted no observed effect on other of the core tactical principles. Caffeine ingestion resulted in less offensive (during SSG3) and defensive (SSG 2, SSG3, and SSG4) errors. Caffeine ingestion also resulted in higher total offensive success during SSG 1 and SSG2, but it was detrimental during SSG3. Additionally, total defensive success was lower for the caffeine conditions during SSG 2 and SSG5 when compared to the placebo. In conclusion, caffeine influenced aspects of tactical decisions in soccer, resulting in fewer offensive and defensive errors, although it may be deleterious considering other tactical parameters. Future studies may clarify the effects of caffeine ingestion on specific decision-making parameters in soccer.



#10 Perceived Social Support, Reinjury Anxiety, and Psychological Readiness to Return to Sport in Soccer Players

Reference: J Sport Rehabil. 2022 Apr 11;1-7. doi: 10.1123/jsr.2021-0181. Online ahead of print.

Authors: Dale Forsdyke, Daniel Madigan, Adam Gledhill, Andy Smith

Summary: The burden of sports injury in soccer is high, and return to sport outcomes following injury are often poor. This is compounded by a current lack of understanding surrounding the factors that may optimize psychological readiness to return to sport. Consequently, in the present study, we aim to further our understanding of these issues by examining the role of perceived social support in predicting psychological readiness to return to sport. In doing so, we extend previous research by examining whether reinjury anxiety is a mediating factor in this relationship. A sample of 150 previously injured soccer players (mean age = 25.32 y) completed measures of perceived social support, reinjury anxiety during rehabilitation, and psychological readiness to return to sport. Mediation analyses showed that reinjury anxiety partly accounted for the positive relationship between perceived social support and psychological readiness to return to sport. These findings suggest that injured soccer players with higher perceptions of social support will experience less reinjury anxiety during rehabilitation and, as a consequence, will be more psychologically ready upon return to sport.



#11 Discovering Oculometric Patterns to Detect Cognitive Performance Changes in Healthy Youth Football Athletes

Reference: J Healthc Inform Res. 2019 Feb 8;3(4):371-392. doi: 10.1007/s41666-019-00045-4. eCollection 2019 Dec.

Authors: Gaurav N Pradhan, Jamie M Bogle, Michael J Cevette, Jan Stepanek

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Summary: In this paper, we focus on the application of oculometric patterns extracted from raw eye movements during a mental workload task to assess changes in cognitive performance in healthy youth athletes over the course of a typical sport season. Oculometric features pertaining to fixations and saccades were measured on 116 athletes in pre- and post-season testing. Participants were between 7 and 14 years of age at pre-season testing. Due to varied developmental rates, there were large interindividual performance differences during a mental workload task consisting of reading numbers. Based on different reading speeds, we classified three profiles (slow, moderate, and fast) and established their corresponding baselines for oculometric data. Within each profile, we describe changes in oculomotor function based on changes in cognitive performance during the season. To visualize these changes in multidimensional oculometric data, we also present a multidimensional visualization tool named DiViTo (diagnostic visualization tool). These experimental, computational informatics and visualization methodologies may serve to utilize oculometric information to detect changes in cognitive performance due to mild or severe cognitive impairment such as concussion/mild traumatic brain injury, as well as possibly other disorders such as attention deficit hyperactivity disorders, learning/reading disabilities, impairment of alertness, and neurocognitive function.



#12 Professional football training strategies during home confinement in the COVID-19 pandemic

Reference: J Sports Med Phys Fitness. 2022 Apr 12. doi: 10.23736/S0022-4707.22.13143-9. Online ahead of print.

Authors: Paolo Albino, Antonio Ponzo, Stefano D'Ottavio, Gioacchino Pollara, Angelo Ventura, F Rodia

Summary: SARS-COVID-19 emergency forced athletes to train at home on their own and mostly unsupervised, making it difficult to provide training solutions. The aims of the study were 1) to collect data and experiences from a Serie A male football team, a top-level female football team and a male young elite football team; 2) to compare data from lockdown and pre-lockdown period; 3) to report changes in training strategies adopted to overcome logistical constraints and 4) to evaluate their congruence to cardio, strength and stretching recommendation mentioned above; 5) to report compliance through player daily feedback. Three different professional football teams were enrolled. From March 16, 2020 to April 13, 2020, data for each team were recorded weekly and compared to a standard training period (October 15-November 15, 2019) from the same groups. The Rate of Perceived Exertion (RPE), Visual Analogue Scale (VAS) and Total Quality of Recovery (TQR) values were used to compare the two periods using The Student t-test and Pearson test. Each group chose a different training approach. Between the pre-lockdown and the lockdown period, there was no significant difference in the VAS, TQR and RPE indexes. Other else players' compliance differed between the groups during the lockdown period. Most athletes maintained a high level of training during the COVID-19 forced isolation, thanks to the help of team athletic trainers who provide functional tools and indications customized for each differ. Athletes' feedback and compliance differed according to their gender and age. Monitoring with live video sessions and social group sharing among younger players improved compliance and aggregation.



#13 The relationship between team-level and league-level injury rate, type and location in a professional football league

Reference: J Sci Med Sport. 2022 Mar 30;S1440-2440(22)00080-9. doi: 10.1016/j.jsams.2022.03.017.

Authors: Donna Lu, Alan McCall, Mark Jones, Rob Duffield

Summary: The aim was to describe the relationship between team- and league-level variability of injury rate, type, and location over 6 seasons in professional Australian football (A-League). Injury incidence, type and location were collected from all A-League teams (n = 10) for 6 consecutive seasons (2012/13 to 2017/18) via a standardised injury surveillance system. Intra-class correlation and coefficient of variation were calculated to assess the between-season variability of injury measures for each team. To determine the relationship between team-level injury variability on league-level injury rates, Marginal Coefficient of Determination to Coefficient of Determination were then calculated from generalised linear mixed models. This allowed determination between season trends, where league-level injury incidence, type- and location rates as the response variables, season as the predictor variable and teams as random intercepts. The majority of teams showed poor to moderate correlations for between-season injury rates (intra-class correlation: r = 0.319-0.831), but also showed low-moderate variability between-seasons for injury rate (coefficient of variation 34 ± 22%). League injury rates were stable, though were reduced in 2015/16 compared to 2012/13 (β = 0.738; p = 0.011). Joint/Ligament injuries had coinciding significant reduction in 2015/16 (p = 0.001). The model variance showed the reduction of Joint/Ligament injuries was league-wide rather than team-specific (Marginal Coefficient of Determintion = 0.23; Coefficient of Determination = 0.23). In the A-League, low between-season injury rate variability from teams contributed to a stable league-level injury trend over seasons. A reduction in league injury rate in 2015/16 was mirrored by league-wide Joint/Ligament injury rates, without specific effect by team.



#14 Knee and hip agonist-antagonist relationship in male under-19 soccer players

Reference: PLoS One. 2022 Apr 15;17(4):e0266881. doi: 10.1371/journal.pone.0266881. eCollection 2022.

Authors: Filipe Rosa, Hugo Sarmento, João Pedro Duarte, Joel Barrera, Francisco Loureiro, Vasco Vaz, Nestor Saavedra, António José Figueiredo

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Summary: The purpose of this study was to evaluate the strength of the knee flexors and extensors and hip abductor and adductor muscles in young soccer players. Twenty-three male under-19 soccer players participated in this study (age: 17.7 ± 0.2 years; height: 173.0 ± 1.1 cm; body mass: 66.1 ± 1.3 kg). Body composition was measured using a bioelectrical impedance (InBody770), and the dynamometry was performed by an isokinetic dynamometer (Biodex System 3) for knee flexion and extension, and by an isometric dynamometer (Smart Groin Trainer), for hip adduction and abduction. Comparisons were made between dominant members (D) vs. non-dominant members (ND) and adductors vs. abductors (ADD:ABD) using the Wilcoxon test. There were statistically significant differences in the peak torques between the dominant and non-dominant members in the flexion function (Z = -4.198, p < 0.01) and in the extension function (Z = -4.197, p < 0.01) of the knee in concentric muscular action, and the flexion (Z = -4.198, p < 0.01) and in the extension (Z = -4.198, p < 0.01) of the knee in eccentric muscular action. No statistically significant differences were obtained in the conventional ratio (Z = -0.456, p = 0.648) nor the functional ratio (Z = -0.335, p = 0.738) between D and ND members. There were no statistically significant differences between adductors and abductors at the moment of strength for absolute values (N). The reference absolute and normalized to the weight values and the ADD:ABD can be used as a guideline for classifying players in screening and comparison in return tests to sports practice after an injury.



#15 Facilitating national football teams return to training and competition during the COVID-19 pandemic

Reference: BMJ Open Sport Exerc Med. 2022 Apr 10;8(2):e001295. doi: 10.1136/bmjsem-2021-001295. eCollection 2022.

Authors: Andrew Guard, Anne Brenneman, Matt Bradley, George T Chiampas

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Summary: Provide a robust framework to provide a safe environment for return to training and competition of the US national soccer teams following domestic and international travel. US Soccer COVID-19 working group created a return to play manual for its national teams, prescribing discrete phases to return to training and competition. This was underpinned by strict health and safety and travel protocols for specific venues and persons. This was complemented by an aggressive testing cadence and isolation policies for delegations (players, internal and external support staff). Between September 2020 and April 2021, there were nine events for males and females at the youth, senior and Paralympic level, with international opponents hosted domestically. In total, 6590 point of care (POC) (n=1810) and PCR (n=4780) tests combined were run. Overall positivity rate for players and staff in male events of 0.10% (n=2) and 0.00% (n=0) for females were recorded. Staff positivity rate was 0.14% overall, and external vendors 0.10%. Total POC and PCR positives in male events (n=2) occurred either the day of arrival or the following day. The implementation of strictly adhered to protocols and testing cadences yielded low positivity rates within team delegations. By comparison, initial league-wide COVID-19 testing in mid-2020 in other sports reported league-wide positivity rates of 2.9% (National Football League), 2.7% (Major League Soccer) and 5.3% (National Basketball Association). The English Premier League reported an increase in positivity rate in early 2021 from 1.22% to 1.74%.With the implementation of regimented protocols and stringent testing, it is possible to hold elite-level international sporting competitions involving long-haul travel while ensuring continued safety during a global pandemic.



#16 A Longitudinal Study on the Evolution of the Four Main Football Leagues Using Artificial Intelligence: Analysis of the Differences in English Premier League Teams

Reference: Res Q Exerc Sport. 2022 Apr 19;1-9. doi: 10.1080/02701367.2021.2019661. Online ahead of print.

Authors: Abraham García-Aliaga, Moisés Marquina Nieto, Javier Coterón, Asier Rodríguez-González, Javier Gil Ares, Ignacio Refoyo Román

Summary: The aim of this study was to analyze the evolution of the four most important leagues and to identify if there are differences between the English Premier League and the rest of the European leagues.  Each team was characterized according to a set of 52 variables including offensive, defensive, and buildup 10 variables that were computed from OPTA's on-ball event records of the matches for main national leagues between the 2014 and 2018 seasons. To test the evolution of leagues, the t-SNE dimensionality reduction technique was used. To better understand the differences between leagues and teams, the most discriminating variables were obtained as a set of rules discovered by RIPPER, a machine learning algorithm.  The evolution of playing styles has meant that teams in the major European leagues seem to 15 be approaching homogeneity of technical-tactical behavior. Despite this, a distinction can be seen between the English teams concerning the rest of the teams in the other leagues, determined by fewer free kicks, fewer long passes but more vertical, more errors in ball control but greater success in dribbling.  These results provide important knowledge and practical applications because of the study of the different variables and performance indicators among the best football championships.



#17 There's No Sport Without Spectators - Viewing Football Games Without Spectators During the COVID-19 Pandemic

Reference: Front Psychol. 2022 Mar 31;13:860747. doi: 10.3389/fpsyg.2022.860747. eCollection 2022.

Authors: Ilan Tamir

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Summary: The presence of sports fans in the stands is considered a natural and essential element of sporting events. Beyond the atmosphere fans create and the color they add to the game, their presence reflects the idea that the game is more than a competition between two teams -it is a grand battle between communities and identities, which is also the reason that fans are willing to sacrifice so much on behalf of their team. As is other areas of life, the COVID-19 pandemic created an unusual situation, in which sporting events were held without spectators in the stadium stands. In many places around the world, professional sporting activities were permitted but spectators were not allowed into the stadiums due to social distancing restrictions. The current study examines this unique situation and through it, gains an understanding of fans' beliefs concerning the significance of spectators and their presence in the stadium. Through in-depth interviews with football fans who regularly attend games (in the pre-pandemic period), the current study explores football fans' experiences as they viewed "ghost games" (where teams played to empty stadiums). Findings show that this unique situation, caused by the global pandemic, heightened fans' deep-rooted connection to sports and to their favorite team, and also exacerbated the social, emotional, and professional implications of viewing football games with no spectators.



#18 Effect of 2002 FIFA World Cup: Point of Attachment That Promotes Mass Football Participation

Reference: Front Psychol. 2022 Mar 30;13:857323. doi: 10.3389/fpsyg.2022.857323. eCollection 2022.

Authors: Taeahn Kang, Jeongbeom Hahm, Hirotaka Matsuoka

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Summary: The 2002 FIFA World Cup Korea/Japan significantly promoted football in the host countries. However, it remains unclear how the event has changed mass football (soccer in North America) participation. This study applies points of attachment (POA)-a well-developed concept in the field of sport management-to the 2002 FIFA World Cup and aims to examine which specific POA promoted football participation frequency immediately after the event and the present frequency of football participation in the host countries. An online questionnaire survey was conducted in South Korea (n = 405) and Japan (n = 398). The samples included adults aged > 19 as of the hosting date of the 2002 World Cup. Hierarchical regression analyses were performed to test all the datasets by employing four POAs (players, coaches, national teams, and football) as independent variables. Multiple control variables (e.g., nationality and age) and two dependent variables (football participation frequency immediately after the event and the present frequency of football participation) were included in the model. Correspondingly, those who had a higher attachment to each point during the event showed a higher frequency of football participation immediately after the event. In contrast, only two POAs (players and coaches) led to a higher frequency of present football participation. These findings provide the first empirical evidence highlighting the influence of the 2002 FIFA World Cup on mass football participation depending on the POA.



#19 Effects of Chronological Age, Relative Age, and Maturation Status on Accumulated Training Load and Perceived Exertion in Young Sub-Elite Football Players

Reference: Front Physiol. 2022 Mar 31;13:832202. doi: 10.3389/fphys.2022.832202. eCollection 2022.

Authors: José Eduardo Teixeira, Ana Ruivo Alves, Ricardo Ferraz, Pedro Forte, Miguel Leal, Joana Ribeiro, António J Silva, Tiago M Barbosa, António M Monteiro

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Summary: The aims of this study were 1) to analyze the influence of chronological age, relative age, and biological maturation on accumulated training load and perceived exertion in young sub-elite football players and 2) to understand the interaction effects amongst age grouping, maturation status, and birth quartiles on accumulated training load and perceived exertion in this target population. A 6-week period (18 training sessions and 324 observation cases) concerning 60 young male sub-elite football players grouped into relative age (Q1 to Q4), age group (U15, U17, and U19), and maturation status (Pre-peak height velocity (PHV), Mid-PHV, and Post-PHV) was established. External training load data were collected using 18 Hz global positioning system technology (GPS), heart-rate measures by a 1 Hz short-range telemetry system, and perceived exertion with total quality recovery (TQR) and rating of perceived exertion (RPE). U17 players and U15 players were 2.35 (95% CI: 1.25-4.51) and 1.60 (95% CI: 0.19-4.33) times more likely to pertain to Q1 and Q3, respectively. A negative magnitude for odds ratio was found in all four quartile comparisons within maturation status (95% CI: 6.72-0.64), except for Mid-PHV on Q2 (95% CI: 0.19-4.33). Between- and within-subject analysis reported significant differences in all variables on age group comparison measures (F = 0.439 to 26.636, p = 0.000 to 0.019, η2 = 0.003-0.037), except for dynamic stress load (DSL). Between-subject analysis on maturity status comparison demonstrated significant differences for all training load measures (F = 6.593 to 14.424, p = 0.000 to 0.037, η2 = 0.020-0.092). Interaction effects were found for age group x maturity band x relative age (Λ Pillai's = 0.391, Λ Wilk's = 0.609, F = 11.385, p = 0.000, η2 = 0.391) and maturity band x relative age (Λ Pillai's = 0.252, Λ Wilk's = 0.769, F = 0.955, p = 0.004, η2 = 0.112). Current research has confirmed the effects of chronological age, relative age, and biological maturation on accumulated training load. Perceived exertion does not seem to show any differences concerning age group or maturity status. Evidence should be helpful for professionals to optimize the training process and young football players' performance.



#20 Prevalence and burden of health problems in top-level football referees

Reference: Sci Med Footb. 2022 Apr 18;1-8. doi: 10.1080/24733938.2022.2055782. Online ahead of print.

Authors: Christian Moen, Thor Einar Andersen, Ben Clarsen, Gitte Madsen-Kaarød, Torstein Dalen-Lorentsen

Summary: Top-level football referees take decisions during strenuous physical activity, and often under great mental pressure. Despite their central role in a football match, little is known about referees' health problems, particularly in female referees. The aim was to investigate the prevalence and burden of health problems in female and male top-level referees. Fifty-five Norwegian male and female top-level referees reported health problems (injuries and illnesses) in pre-season and during the 2020 competitive season, using the Oslo Sports Trauma Research Center Questionnaire on Health Problems (OSTRC-H2). We recorded data for 49 weeks with a compliance of 98%. On average, 34% (95% CI 31-36%) of referees reported at least one health problem each week, and 20% (95% CI 19-22%) reported substantial health problems. Female referees reported more health problems than male referees, and on-field referees reported more health problems than assistant referees. Gradual-onset injuries were most prevalent and caused the greatest absence from training and matches, whereas illnesses represented only a small portion to the overall burden of health problems. The injury incidence was three injuries per athlete-year (95% CI 2.5-3.5) and 11 injuries per 1000 match hours (95% CI 7-18). The illness incidence was 1.4 illnesses per athlete-year (95% CI 1.1-1.8). Injuries to the lower legs and feet represented the highest burden of health problems. Top-level referees, especially females, reported a high prevalence of health problems. Gradual-onset injuries to the lower leg and foot represented the highest injury burden.



#21 Incidence and Clinical Relevance of COVID-19 in a Population of Young Competitive and Elite Football Players: A Retrospective Observational Study

Reference: Sports Med Open. 2022 Apr 15;8(1):54. doi: 10.1186/s40798-022-00442-x.

Authors: Lidia Colangelo, Alessandra Volpe, Elisabetta Toso, Massimo Magnano, Mario Matta, Chiara Vignati, Andrea Marchini, Luca Semperboni, Luca Stefanini, Fiorenzo Gaita

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Summary: The COVID-19 pandemic dramatically changed lifestyle worldwide, including sport. A comprehensive evaluation of the prevalence of cardiac involvement in COVID-19 is essential to finalize a safe protocol for resuming elite sport. The aim of this study is to evaluate incidence of cardiac involvement and COVID-19 impact on athletic performance. This retrospective observational study analysed the data collected from consecutive competitive athletes who performed medical-sports examinations at the J Medical Center from March 2020 to March 2021. All athletes periodically performed a molecular test using a nasopharyngeal swab to detect COVID-19 infection. Positive athletes performed laboratory (cardiac troponin T-cTnT) and instrumental (echocardiography, stress test, Holter ECG) investigations following recovery to identify any cardiac involvement. Cardiac magnetic resonance imaging (MRI) was performed in case of abnormal findings at first-level evaluation. Among 238 athletes (median age 20 years), 77 contracted COVID-19, mainly males (79%) with a median age of 16 years. Fifty-one athletes (66%) presented mild symptoms, and none required hospitalization. Evaluation for resuming sport was performed after a median of 30 days from the first positive test. Abnormal findings were obtained in 13 cases (5 athletes [6%] with elevated cTnT values; 13 athletes [17%] with arrhythmias on Holter ECG and/or during stress test; 2 athletes [3%] anomalies at echocardiography). Cardiac MRI discovered abnormalities in 9 cases, but none of these was clearly related to COVID-19 and none fulfilled acute myocarditis criteria. No negative impact on athletic performance was observed, and none of the athletes developed persistent COVID-related symptoms. Our registry confirms the predominantly self-limiting illness in young athlete population. The incidence of clear COVID-19-related structural myocardial injury was very low, but transient exertional ventricular arrhythmias or pericardial effusion was observed without significant impact on athletic performance. Implemented screening for return to activity is likely reasonable only in moderate-to-severe symptomatic athletes.






Accumulative weekly load in a professional football team: with special reference to match playing time and game position

The aim of this study was to compare weekly accumulative load during the in-season competitive period by professional soccer players according to the amount of time played in official matches (90-min, >60-min, <60-min, and 0-min) regarding the players’ position.





How does curve sprint evolve across age categories in soccer players?

The aim was to determine the age-related effects on curve sprint (CS) performance to both sides, asymmetry, and association with linear sprint (LS).





Latest research in football - week 14 - 2022

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 Assessing the usefulness of submaximal exercise heart rates for monitoring cardiorespiratory fitness changes in elite youth soccer players

Reference: Sci Med Footb. 2022 Mar 29.  doi: 010.1080/24733938.2022.2060520. Online ahead of print.

Authors: Stefan Altmann, Ludwig Ruf, Rainer Neumann, Sascha Härtel, Alexander Woll, Martin Buchheit

Summary: This study aimed to assess the value of monitoring fitness in elite youth soccer players (U15 to U19 age groups) by analyzing the concomitant changes in heart rate at submaximal intensity (HR12km/h) and the velocity at a lactate concentration of 4 mmol/l (v4mmol/l). Players were tested by means of an incremental treadmill test on two occasions during the summer pre-season in two consecutive seasons. Based on data from a total of 170 test comparisons from the U15 (n = 48 test comparisons), U16 (n = 40 test comparisons), U17 (n = 46 test comparisons), and U19 (n = 36 test comparisons) age groups, the agreement between substantial changes in HR12km/h and v4mmol/l was analyzed using the threshold combination of HR12km/h = 4.5% and v4mmol/l = 6.0%. Results revealed 2% full mismatches, 36% partial agreements, and 62% full agreements for the whole sample in terms of fitness change interpretation between both variables. The respective values for the U15 to U19 age groups ranged between 0-5% full mismatches, 28-44% partial agreements, and 56-68% full agreements with no meaningful differences between age groups. In conclusion, our findings confirm the practical value of using HR12km/h to monitor fitness changes in elite youth soccer players when lactate sampling during incremental tests is not possible.



#2 Acute effects of beetroot juice and caffeine co-ingestion during a team-sport-specific intermittent exercise test in semi-professional soccer players: a randomized, double-blind, placebo-controlled study

Reference: BMC Sports Sci Med Rehabil. 2022 Mar 29;14(1):52. doi: 10.1186/s13102-022-00441-1.

Authors: Erfan Berjisian, Kerry McGawley, Bryan Saunders, Raúl Domínguez, Majid S Koozehchian, Caio Victor Coutinho de Oliveira, Ramin Rafiei, Hossein Miraftabi, Amir Sarshin, Alireza Naderi

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Summary: Beetroot juice (BJ) and caffeine (CAF) are considered as ergogenic aids among athletes to enhance performance, however, the ergogenic effects of BJ and CAF co-ingestion are unclear during team-sport-specific performance. This study aimed to investigate the acute effects of BJ and CAF co-ingestion on team-sport-specific performance, compared with placebo (PL), BJ, and CAF alone. Sixteen semi-professional male soccer players (age: 19.8 ± 2.2 years, body mass: 69.2 ± 6.1 kg, height: 177.3 ± 6.0 cm) completed four experimental trials using a randomized, double-blind study design: BJ + CAF, CAF + PL, BJ + PL, and PL + PL. Countermovement jump with arm swing (CMJAS) performance and cognitive function by Stroop Word-Color test were evaluated before and after the Yo-Yo Intermittent Recovery Test level 1 (YYIR1). Also, rate of perceived exertion (RPE), heart rate, and gastrointestinal (GI) discomfort were measured during each session. No significant differences were shown between test conditions for total distance covered in YYIR1 (BJ + CAF: 1858 ± 455 m, CAF + PL: 1798 ± 422 m, BJ + PL: 1845 ± 408 m, PL + PL 1740 ± 362 m; p = 0.55). Moreover, CMJAS performance, cognitive function, and RPE during the YYIR1 were not significantly different among conditions (p > 0.05). However, the average heart rate during the YYIR1 was higher in CAF + PL compared to PL + PL (by 6 ± 9 beats/min; p < 0.05), and GI distress was greater in BJ + CAF compared to PL + PL (by 2.4 ± 3.6 a.u.; p < 0.05). These results suggest, neither acute co-ingestion of BJ + CAF nor BJ or CAF supplementation alone significantly affected team-sport-specific performance compared to the PL treatment.



#3 Epidemiology of soccer injuries in Korea women national team for 5 years

Reference: J Exerc Rehabil. 2022 Feb 24;18(1):68-73.  doi: 10.12965/jer.2142698.349. eCollection 2022 Feb.

Authors: Chang-Hwa Joo

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Summary: The purpose of this study was to analyze the characteristics of injuries in female national soccer players. The injuries data were recorded by Korea Football Association medical staff using the Daily Medical Report provided by the Asian Football Confederation during a total 21 training camps and friendly and official matches from January 2014 to December 2018. A total of 483 players in the national team training camps and matches participated in the study, of which 377 players experienced more than one injury. Sports injuries accounted for 89% of the total 1,019 injuries; general diseases accounted for the remaining 11%. The number of injuries per 1,000 exposure hours was higher in matches than in training sessions. Most injuries that occurred during training and matches involved the lower extremities (79%). The most common injury diagnosed during training and matches was muscle rigidity (45%), followed by contusions/hematomas/bruises (22%) and sprain (15%). The largest proportions of injuries in terms of absence from soccer play were minimal injury (67%), followed by mild (29%), moderate (3.5%), and severe (1%). As conclusion, the characteristics of injuries during training sessions and matches were different. Rehabilitation and injury prevention programs need to developed for female soccer players to improve the players' performance.



#4 Incidence of Injury for Professional Soccer Players in the United States: A 6-Year Prospective Study of Major League Soccer

Reference: Orthop J Sports Med. 2022 Mar 24;10(3):23259671211055136. doi: 10.1177/23259671211055136. eCollection 2022 Mar.

Authors: Brian Forsythe, Derrick M Knapik, Matthew D Crawford, Connor C Diaz, David Hardin, John Gallucci, Holly Jacinda Silvers-Granelli, Bert R Mandelbaum, Lawrence Lemak, Margot Putukian, Eric Giza

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Summary: Despite an abundance of injury research focusing on European professional soccer athletes, there are limited injury data on professional soccer players in the United States. The aim was to describe the epidemiology of injury across multiple years in Major League Soccer (MLS) players. A web-based health management platform was used to prospectively collect injury data from all MLS teams between 2014 and 2019. An injury was defined as an incident that required medical attention and was recorded into the health management platform anytime over the course of the 2014-2019 seasons. Injuries and exposure data were recorded in training and match settings to calculate injury incidence. A total of 9713 injuries were recorded between 2014 and 2019. A mean 1.1 injuries per year per player were identified, with midfielders sustaining the largest number of injuries. The most common injuries were hamstring strains (12.3%), ankle sprains (8.5%), and adductor strains (7.6%). The mean time missed per injury was 15.8 days, with 44.2% of injuries resulting in no days missed. Overall injury incidence was 8.7 per 1000 hours of exposure, declining over the course of the investigation, with a 4.1-times greater mean incidence during matches (14.0/1000 h) than training (3.4/1000 h). Between 2014 and 2019, the most commonly reported injuries in MLS players were hamstring strains, ankle sprains, and adductor strains. Injury incidence during matches was 4.1 times greater when compared with training, while overall injury incidence was found to decline during the course of the study period.



#5 Biomechanical Analysis and Training Method Research on Head Shot Strength of Football Players

Reference: J Healthc Eng. 2022 Mar 15;2022:7594124. doi: 10.1155/2022/7594124. eCollection 2022.

Authors: Yipeng Yao, Shanshan Xiang

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Summary: With the development of intelligent sports in China and the rapid improvement of the strength of colleges and universities, the reform of traditional football players' header shooting training methods is becoming more and more urgent in order to solve some problems in the development of sports and speed up the intelligent training of Chinese football players. Based on this, this paper studies the biomechanical analysis and training method based on the integration of header strength data of football players. A dynamic header tracking model of football players based on a local search algorithm is designed. The data collection is realized from the aspects of athletes' header shooting training, skill improvement, physical consumption, and trajectory. The biological data of header shooting power is comprehensively analyzed and evaluated by using a local search algorithm. The results show that the training system based on a local search algorithm has the advantages of high feasibility, high data accuracy, and fast response speed. It can effectively conduct accurate guidance and improve the shooting accuracy according to the biological characteristics of header shooting intensity. This paper studies the biological analysis and training method of header strength of football players based on a local search algorithm. This has certain reference significance for accelerating the construction of intelligent training of Chinese football players.



#6 Biomechanical Load Quantification Using a Lower Extremity Inertial Sensor Setup During Football Specific Activities

Reference: Sports Biomech. 2022 Mar 28;1-16. doi: 10.1080/14763141.2022.2051596. Online ahead of print.

Authors: Bram J C Bastiaansen, Riemer J K Vegter, E Wilmes, Cornelis J de Ruiter, Koen A P M Lemmink, Michel S Brink

Summary: Training load monitoring systems in football do not focus on lower extremities and therefore potentially neglect important information to optimise performance or reduce injury risk. The current study aims to present joint and segment angular accelerations as novel indicators to quantify lower extremity biomechanical load measured by a new inertial sensor setup. Relationships were explored with commonly used whole-body training load indicators using principal component analysis (PCA). Sixteen male amateur football players performed a linear sprint and an agility T-test. An inertial sensor setup, and local position measurement system were used to collect training load data. Hip Load, Knee Load, Thigh Load and Shank Load were introduced to quantify lower extremity biomechanical load. Three principal components were identified for both tests, explaining 91% and 86% of the variance. The indicators for the lower extremities contributed to the second principal component for both tests and provide distinct information compared to whole-body load indicators. The results show the potential to use an inertial sensor setup combined with common monitoring systems to evaluate training load, which may help optimise future performance and reduce injury risk. These relationships should be further examined during other football specific activities such as shooting or jumping.



#7 How spatial constraints afford successful and unsuccessful penetrative passes in elite association football

Reference: Sci Med Footb. 2022 Mar 30.  doi: 10.1080/24733938.2022.2060519. Online ahead of print.

Authors: Bruno Travassos, Ricardo Monteiro, Diogo Coutinho, Farzad Yousefian, Bruno Gonçalves

Summary: The aim of the present study was to examine the spatial relations between teams (macro-level) and groups of players (meso-level) that afford successful penetrative passes (off-ball advantage) in elite football. Three balanced home matches from a Premier League team with 91 ball possessions in which a pass was performed into the opposition defensive area and overpassed the first defensive line, promoting a perturbation of the defensive team equilibrium, were selected for analysis. The spatial relations between teams were measured through spatial variables that captured the areas occupied by the teams, while the spatial relations between players were measured through variables that captured the distances and angles between attacking and defending players near the ball. Results revealed, at the macro-level, higher values of width ratio between teams and the width of the attacking team for unsuccessful penetrative passes (UPP), when compared to successful penetrative passes (SPP). At the meso-level, a general decrease in distances and an increase in angles between attacking and defending players were observed between successful to unsuccessful penetrative passes. These findings highlight the importance of using positional data analysis to identify teams' tactical profiles and to potentiate coaches' interventions.



#8 Physical demands on professional Spanish football referees during matches

Reference: Sci Med Footb. 2022 Apr 7.  doi: 10.1080/24733938.2022.2064539. Online ahead of print.

Authors: Gemma Martínez-Torremocha, Maria Luisa Martin-Sanchez, Jorge Garcia-Unanue, Jose Luis Felipe, Víctor Moreno-Pérez, Víctor Paredes-Hernández, Leonor Gallardo, Javier Sanchez-Sanchez

Summary: Refereeing is a demanding and intermittent activity that combines high-speed and low-intensity action. The aim of this study is to analyse the external and internal load of professional Spanish football referees during matches, and to compare the physical demands between halves and between referees in different categories. The physical demands on 40 professional football referees from the first and second divisions were recorded using global positioning system (GPS) technology and heart rate bands. External load (distance covered, speed, acceleration and deceleration) and internal load (perceived exertion [RPE] and heart rate [HR]) were analysed. The referees in the first division reported lower mean HR and RPE results than those in the second division (p < 0.05). The total distance covered was similar between the categories (p > 0.05), but the distance covered at different speed ranges was different (p < 0.05). Finally, greater reductions in performance between the first and the second halves were found in the second division referees (p < 0.05). The results of this study show differences according to the category of referee. This emphasises the need for specific training for professional referees according to their level to ensure optimal performance during matches.



#9 Comparing Sleep in Shared and Individual Rooms during a Training Camp in Elite Youth Soccer Player's: A Short Report

Reference: J Athl Train. 2022 Apr 5.  doi: 10.4085/1062-6050-0042.22. Online ahead of print.

Authors: Júlio A Costa, Pedro Figueiredo, Michele Lastella, Fábio Y Nakamura, José Guilherme, João Brito

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Summary: The study aims were to analyse the impact of sleeping in shared (SR) vs. individual (IR) rooms on objective and subjective sleep, and on slow-wave sleep (SWS)-derived cardiac autonomic activity during an official training camp in elite youth soccer players. Training and match workloads were characterized between training camps. Players slept significantly longer during IR than SR (+ 1:28 [1:18-1:42] min, P < .001). Sleep efficiency was significantly higher during IR than SR (+ 12 [10-15] %; P < .001), while sleep latency was significantly shorter during IR than SR (-3 [-15 - -4] min; P < .001). Subjective sleep quality was significantly lower during IR than SR (-2 [-3- -2] arbitrary units; P < .001). No significant differences were found for SWS-derived cardiac autonomic activity, neither for training/match workloads between training camps. Sleep may be affected by sleeping in shared compared to individual rooms during soccer training camps.



#10 The influence of angle-specific torque of the knee flexors and extensors on the angle-specific dynamic control ratio in professional female soccer players

Reference: J Sports Sci. 2022 Apr 7;1-8. doi: 10.1080/02640414.2022.2061251. Online ahead of print.

Authors: Steven James Eustace, Rhys Morris, Jason Tallis, Richard Michael Page, Matt Greig

Summary: The purpose of this study was to assess whether dynamic torque ratios (DCR) from isokinetic strength assessments of eccentric knee flexors (eccKF) and concentric knee extensors (conKE) display differences when stratified into specific angle-specific DCR (DCRAST) groups. Fifty-two professional female soccer players (age 21.30 ± 4.44 years; height 166.56 ± 5.17 cm; mass 61.55 ± 5.73 kg) from the English Women's Super League completed strength assessments of both lower limbs on an isokinetic dynamometer at 60°∙s-1. Angle-specific torque (AST) were used to calculate DCRAST to create sub-groups using clustering algorithms. The results identified for the dominant side that the Medium DCRAST group elicited significantly higher conKE AST when compared to Low and High DCRAST groups at increased knee extension (P ≤ 0.05). For the non-dominant side, the High DCRAST group had significantly higher and lower eccKF and conKE AST compared to the Low DCRAST group at increased knee extension (P ≤ 0.05). This study highlights that the inclusion of AST data may subsequently help practitioners to prescribe exercise that promotes strength increases at targeted joint angles. In turn, these approaches can be used to help reduce injury risk, identify rehabilitation responses and help inform return to play.



#11 Relative Skeletal Maturity and Performance Test Outcomes in Elite Youth Middle Eastern Soccer Players

Reference: Med Sci Sports Exerc. 2022 Apr 1. doi: 10.1249/MSS.0000000000002912. Online ahead of print.

Authors: Lorenzo Lolli, Amanda Johnson, Mauricio Monaco, Valter Di Salvo, Warren Gregson

Summary: The aim was to explore the influence of differences in relative skeletal maturity on performance test outcomes in elite youth soccer players from the Middle East. We integrated skeletal age and performance assessments using mixed-longitudinal data available for 199 outfield players (chronological age range: 11.7 to 17.8 yr) enrolled as academy student-athletes (annual screening range: 1 to 5 visits). Skeletal age was determined as per the Tanner-Whitehouse II (TW-II) protocol. Relative maturity was calculated as the difference (∆) between TW-II skeletal age minus chronological age. Performance test outcomes of interest were 10-m sprinting, 40-m sprinting, countermovement jump (CMJ) height and maximal aerobic speed (MAS). Separate random-effects generalized additive models quantified differences in performance test outcomes by relative skeletal maturity. Estimated differences were deemed practically relevant based on the location of the confidence interval (95%CI) against minimal detectable change values for each performance test outcome. For 40-m sprinting, differences of +0.51 s (95%CI, +0.35 to +0.67 s) and + 0.62 s (95%CI, +0.45 to +0.78 s) were practically relevant for relative maturity status of ∆ = -1.5 yr versus ∆ = +0.5 and ∆ = +1 yr, respectively. For CMJ height, a difference of -8 cm (95%CI, -10 to -5 cm) was practically relevant for ∆ = -1.5 yr versus ∆ = +1 yr relative maturity status comparison. Effects for 10-m sprinting and MAS were unclear. Integration of skeletal age and performance assessments indicated conventional maturity status classification criteria were inconsistent to inform player development processes in our sample. Between-player differences in test performance may depend on a substantial delay in skeletal maturation (∆ ≤ -1.5 yr) and the performance outcome measure.



#12 Sex-related Anthropometrics in a Lower-Body Mobility Assessment Among Professional Soccer Athletes

Reference: Int J Sports Phys Ther. 2022 Apr 2;17(3):474-482. doi: 10.26603/001c.32595. eCollection 2022.

Authors: Corbin A Hedt, Jessica T Le, Tyler Heimdal, Justin Vickery, Erin Orozco, Patrick C McCulloch, Bradley S Lambert

Summary: The functional movement screen (FMS™) and Y-balance test (YBT) are commonly used to evaluate mobility in athletes. The primary aim of this investigation was to determine the relationship between demographic and anthropometric factors such as sex, body composition, and skeletal dimension and scoring on YBT and FMS™ in male and female professional soccer athletes. During pre-season assessments, athletes from two professional soccer clubs were recruited and underwent body composition and skeletal dimension analysis via dual-energy X-ray absorptiometry (DEXA) scans. Balance and mobility were assessed using the YBT and FMS™. A two-tailed t-test was used to compare YBT between sexes. Chi-square was used for sex comparisons of FMS™ scores. Correlation analysis was used to determine if body composition and/or skeletal dimensions correlated with YBT or FMS™ measures. Type-I error; α=0.05. 40 Participants were successfully recruited: (24 males: 27±5yr, 79±9kg; |16 females: 25±3yr, 63±4kg). YBT: Correlations were found between anterior reach and height (r=-0.36), total lean mass (LM)(r=-0.39), and trunk LM(r=-0.39) as well as between posterolateral reach and pelvic width (PW)(r=0.42), femur length (r=0.44), and tibia length (r=0.51)(all p<0.05). FMS™: The deep squat score was correlated with height(r=-0.40), PW(r=0.40), LM(r=-0.43), and trunk LM (r =-0.40)(p<0.05). Inline lunge scores were correlated with height(r=-0.63), PW(r=0.60), LM(r=-0.77), trunk LM(r=-0.73), and leg LM(r=0.70)(all p<0.05). Straight leg raise scores were correlated with PW (r=0.45, p<0.05). Females scored higher for the three lower body FMS™ measures where correlations were observed (p<0.05). Lower body FMS™ scores differ between male and female professional soccer athletes and are related to anthropometric factors that may influence screening and outcomes for the FMS™ and YBT, respectively. Thus, these anatomical factors likely need to be taken into account when assessing baseline performance and risk of injury to improve screening efficacy.



#13 C-Reactive Protein and Skin Temperature of the lower limbs of Brazilian elite soccer players like load markers following three consecutive games

Reference: J Therm Biol. 2022 Apr;105:103188.  doi: 10.1016/j.jtherbio.2022.103188. Epub 2022 Feb 3.

Authors: Warley Duarte, Jorge L Rodrigues Júnior, Leandro V Paula, Mauro H Chagas, André G P Andrade, Christiano E Veneroso, Suene F N Chaves, Tane K F Serpa, Eduardo M Pimenta

Summary: The aim of the study was to compare the levels and relative responses of C-Reactive Protein (CRP) and Skin Temperature (Tsk) of the lower limbs (LLs) of elite soccer players following three consecutive games with short intervals (< 4 days). Eleven male professional athletes (age, 29.26 ± 4.52 years) from an Brazil elite team were evaluated, with measurements obtained before (Baseline), and at Post-Games times (24, 48 and 72h). CRP and Tsk levels at 24 h and 48 h Post-Games times were higher than Baseline levels (CRP, p < 0.001, d > 0.9; Tsk, p < 0.04, d > 0.58), additionally, the levels of these variables (CRP vs. Tsk) showed positive correlations (p < 0.05, rs = 0.60-0.88). The relative responses these variables were evaluated (Δ%CRP; Δ%Tsk). The 48h responses of Game 3 are respectively higher than 48 h responses of games 1 and 2, in Δ%CRP (p < 0.03; G3 vs. G1, r = 0.66; G3 vs. G2, r = 0.88) and in Δ%Tsk (p < 0.003; G3 vs. G1, r = 0.88; G3 vs. G2, r = 0.88). The 48 h Post-Game time seems to represent valuable contributions to understanding the development regarding the magnitude and duration of inflammatory processes associated with recovery. Additionally, the positive correlations that were verified allow an increase in the robustness of the analysis of the load of consecutive games through CRP and Tsk of the LLs. Then, these results indicate a physiological stress and a probable cumulative effect of the game loads due to short intervals (< 4 days), which is reinforced by the verified outcome of the Total Distance covered (G3 < G2, p = 0.003; r = 0.88). These findings can contribute to better load control and greater robustness of injury prevention programs.



#14 Repeated Sprint Protocols With Standardized Versus Self-Selected Recovery Periods in Elite Youth Soccer Players: Can They Pace Themselves? A Replication Study

Reference: Pediatr Exerc Sci. 2022 Apr 7;1-9. doi: 10.1123/pes.2021-0082. Online ahead of print.

Authors: Florian A Engel, Stefan Altmann, Hamdi Chtourou, Alexander Woll, Rainer Neumann, Tomer Yona, Billy Sperlich

Summary: Replicating the studies of Gibson et al and Brownstein et al to assess performance, and physiological, and perceived variables during a repeated sprint protocol (RSP) with standardized versus self-selected recovery in youth soccer players. Nineteen male soccer players (age 13.1 [1.3] y) completed 2 separate RSPs. RSP1: 10 × 30-m sprints with 30-second recovery and RSP2: 10 × 30-m sprints interspersed with self-selected recovery periods. Mean time of both 10 × 30-m RSPs and self-selected recovery periods of RSP2 were assessed. Heart rate, blood lactate concentration, and rates of perceived exertion were measured following RSPs. RSP2 revealed longer recovery periods (RSP1: 30.0 [0.0] s; RSP2: 39.0 [7.7] s; P < .001; effect size d = 1.648) with shorter repeated sprint time (mean 30-m sprint time: RSP1: 4.965 [0.256] s; RSP2: 4.865 [0.227] s; P = .014; d = 0.414). Blood lactate concentration (P = .002-.005; d = 0.730-0.958), heart rate (P < .001; d = 1.353), and rates of perceived exertion (RSP1: 14.9 [1.9]; RSP2: 12.9 [2.1]; P = .016; d = 1.046) were higher following RSP1. In contrast to the original studies, the present replication study demonstrated that self-selected recovery periods during a RSP leads to better repeated sprint performance compared with standardized recovery periods in youth soccer players. The better repeated sprint performance with individual recovery durations in RSP2 was achieved with less physiological and perceived effort.



#15 Predicting Hamstring Strains in Soccer Players Based on ROM: An Analysis From a Gender Perspective

Reference: Res Q Exerc Sport. 2022 Apr 8;1-7. doi: 10.1080/02701367.2021.2011091. Online ahead of print.

Authors: Ángela Molina-Cárdenas, Tania Álvarez-Yates, Oscar García-García

Summary: The aim of this study was to explore if specific hip and knee range-of-movement (ROM) tests can predict a risk factor for hamstring strain (HS) injury in male and female soccer players. One hundred amateur soccer players (56 men and 44 women) performed six tests to determine hip and knee ROM: straight leg raise test (SLR), modified Thomas test (TT), hip internal and external rotation (ER), hip abduction and adduction, Nachlas test and Ridge test. A logistic regression analysis was carried out to create a predictive model for HS injuries. The percentage of HS injury was 20.45% and 30.35%, for female and male players. The logistic regression showed a significant model for both genders on the logit of suffering an HS injury with active-SLR and TT variables for females (R2CS = 0.491; R2N = 0.771) and active SLR and ER variables for males (R2CS = 0.623; R2N = 0.882). The predictive models correctly classify 95.5% and 94.6% of cases presenting good sensitivity (77.8% and 88.2%) and full (100%) and high (97.4%) specificity respectively. Furthermore, female players showed a greater ROM than males (p ≤ 0.01). Both female and male soccer players that suffered a HS injury had lower ROM in SLR, NT and RT and higher ROM in the TT that non-injured players. The tests that most likely predict HS injury are SLR and TT in females and SLR and ER in males. Thus, it is suggested to including specific exercises in amateur soccer players training programs to improve hip and knee ROM for injury prevention.



#16 Foot and ankle Osteoarthritis and Cognitive impairment in retired UK Soccer players (FOCUS): protocol for a cross-sectional comparative study with general population controls

Reference: BMJ Open. 2022 Apr 4;12(4):e054371. doi: 10.1136/bmjopen-2021-054371.

Authors: Shima Espahbodi, Gwen Fernandes, Eef Hogervorst, Ahmed Thanoon, Mark Batt, Colin W Fuller, Gordon Fuller, Eamonn Ferguson, Tobias Bast, Michael Doherty, Weiya Zhang

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Summary: Professional footballers commonly experience sports-related injury and repetitive microtrauma to the foot and ankle, placing them at risk of subsequent chronic pain and osteoarthritis (OA) of the foot and ankle. Similarly, repeated heading of the ball, head/neck injuries and concussion have been implicated in later development of neurodegenerative diseases such as dementia. A recent retrospective study found that death from neurodegenerative diseases was higher among former professional soccer players compared with age matched controls. However, well-designed lifetime studies are still needed to provide evidence regarding the prevalence of these conditions and their associated risk factors in retired professional football players compared with the general male population. The aim was to determine whether former professional male footballers have a higher prevalence than the general male population of: (1) foot/ankle pain and radiographic OA; and (2) cognitive and motor impairments associated with dementia and Parkinson's disease. Secondary objectives are to identify specific football-related risk factors such as head impact/concussion for neurodegenerative conditions and foot/ankle injuries for chronic foot/ankle pain and OA. This is a cross-sectional, comparative study involving a questionnaire survey with subsamples of responders being assessed for cognitive function by telephone assessment, and foot/ankle OA by radiographic examination. A sample of 900 adult, male, ex professional footballers will be recruited and compared with a control group of 1100 age-matched general population men between 40 and 100 years old. Prevalence will be estimated per group. Poisson regression will be performed to determine prevalence ratio between the populations and logistic regression will be used to examine risk factors associated with each condition in footballers. This study was approved by the East Midlands-Leicester Central Research Ethics Committee on 23 January 2020 (REC ref: 19/EM/0354). The study results will be disseminated at national and international meetings and submitted for peer-review publication.



#17 Body Pose Estimation Integrated With Notational Analysis: A New Approach to Analyze Penalty Kicks Strategy in Elite Football

Reference: Front Sports Act Living. 2022 Mar 10;4:818556. doi: 10.3389/fspor.2022.818556. eCollection 2022.

Authors: Guilherme de Sousa Pinheiro, Xing Jin, Varley Teoldo Da Costa, Martin Lames

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Summary: Body orientation of football players has proven to be an informative resource related to successful penalty kicks. OpenPose is one of the most popular open-source pose estimation technologies. This study aims: (i) to verify whether OpenPose can detect relevant body orientation angles from video data of penalty kicks in elite football and (ii) to investigate the relationship between these body angles and observable behaviors analyzed via an observational system for penalty kick analysis in football (OSPAF) with the penalty taker and goalkeeper strategy. A total of 34 penalty videos, with standardized viewing angle, from the main European leagues (2017-2020) were analyzed. Relevant body orientation variables were selected for penalty kicks analysis and were extracted from video data through OpenPose technique. The OSPAF, previously validated by experts, was used. The mean confidence score of OpenPose measures was 0.80 ± 0.14. OpenPose Retest reliability values was 0.976 ± 0.03. Logistic regressions were performed to investigate the relationship between OpenPose investigated variables (penalty taker: shoulder, hips, and nonkicking foot orientation; goalkeeper: right and left foot, anticipation), observable behaviors (OSPAF variables), and the strategy (penalty taker: goalkeeper dependent or independent; goalkeeper: shooter dependent or independent) in penalty kicks. The selected body orientation angle (goalkeeper anticipation) measured through OpenPose correlated significantly with the goalkeeper strategy. The prediction model of the goalkeeper's strategy had its accuracy increased to 97% when the variable goalkeeper anticipation was included [ χ2(35)χ(35)2 = 49.648, p < 0.001]. Lower degrees of goalkeeper anticipation, the goalkeeper tactical action (awaiting), and run up speed (slow) were associated with a kicker-dependent strategy. Regarding the penalty taker, the selected body angles measured through OpenPose did not associate significantly with the shooter strategy. Body orientation analysis by using OpenPose has shown sufficient reliability and provides practical applications for analyzing the strategies adopted by goalkeepers in penalty kicks in elite football.



#18 The exchange of health and performance information when transitioning from club to National football teams: A Delphi survey of National team practitioners

Reference: J Sci Med Sport. 2022 Mar 24;S1440-2440(22)00073-1. doi: 10.1016/j.jsams.2022.03.011. 

Authors: Alan McCall, Mike Davison, Andrew Massey, Chelsea Oester, Alexis Weber, Matthew Buckthorpe, Rob Duffield

Summary: To establish agreement in National team contexts when players transition from club to National team about (i) what medical and physical information to collect, (ii) how to use information (iii) identifying challenges to collection and (iv) collection methods. A series of sequential online questionnaires were sent to heads of medical and performance of the 32 National teams following the FIFA 2018 World Cup. Two separate Delphi's; 'Medical' and 'Physical' were administered. The 'Medical' respondent was the person responsible for player health. 'Physical' referred to the person responsible for physical performance. Content analyses were performed, with subsequent rounds designed according to responses of the previous. Agreement was considered at ≥70%. Twenty-three Medical (72%) and 14 (44%) Physical heads participated in Round 1 (3 rounds total). Seventeen Medical and 12 Physical respondents completed all rounds. Medical information agreed upon injury epidemiology, screening and injury treatment strategies. Physical information included training/match-loads, fatigue, wellness and current exercise programmes. Both Medical and Physical agreed information should be used to plan and individualise player programmes. Additionally medical information should guide coaches' national team selection. Communication, willingness to share and quality/completeness of information were agreed as main challenges. Medical and Physical respondents agreed a standardised reporting form and electronic shared database as best option to collect information. Our findings highlight the importance of health and performance information exchange between national and club teams. Further, this exchange should be cooperative, symbiotic and a two-way process to assist with improving player health.



#19 Comparing lab and field agility kinematics in young talented female football players: implications for ACL injury prevention

Reference: Eur J Sport Sci. 2022 Apr 11;1-25. doi: 10.1080/17461391.2022.2064771. Online ahead of print.

Authors: S Stefano Di Paolo, Eline Nijmeijer, Laura Bragonzoni, Evelien Dingshoff, Alli Gokeler, Anne Benjaminse

Summary: Modifiable (biomechanical and neuromuscular) anterior cruciate ligament (ACL) injury risk factors have been identified in laboratory settings. These risk factors were subsequently used in ACL injury prevention measures. Due to the lack of ecological validity, the use of on-field data in the ACL injury risk screening is increasingly advocated. Though, the kinematic differences between laboratory and on-field settings have never been investigated. The aim of the present study was to investigate the lower-limb kinematics of female footballers during agility movements performed both in laboratory and football field environments.Twenty-eight healthy young female talented football (soccer) players (14.9 ± 0.9 years) participated. Lower-limb joint kinematics was collected through wearable inertial sensors (Xsens Link) in three conditions: 1) laboratory setting during unanticipated sidestep cutting at 40-50°; on the football pitch 2) football-specific exercises (F-EX) and 3) football games (F-GAME). A hierarchical two-level random effect model in Statistical Parametric Mapping was used to compare joint kinematics among the conditions. Waveform consistency was investigated through Pearson's correlation coefficient and standardized z-score vector.In-lab kinematics differed from the on-field ones, while the latter were similar in overall shape and peaks. Lower sagittal plane range of motion, greater ankle eversion, and pelvic rotation were found for on-field kinematics (p<0.044). The largest differences were found during landing and weight acceptance.The biomechanical differences between lab and field settings suggest the application of context-related adaptations in female footballers and have implications in ACL injury prevention strategies.Highlights- Talented youth female football players showed kinematical differences between the lab condition and the on-field ones, thus adopting a context-related motor strategy.- Lower sagittal plane range of motion, greater ankle eversion, and pelvic rotation were found on the field. Such differences pertain to the ACL injury mechanism and prevention strategies.- Preventative training should support the adoption of non-linear motor learning to stimulate greater self-organization and adaptability- It is recommended to test football players in an ecological environment to improve subsequent primary ACL injury prevention programs.






10-min warm-up in hot climate assists thermal comfort, power output, and fatigue, during soccer-specific repeated-sprint ability

The study investigated the effect of two warm-up (WU) durations (i.e.10 min: WU10 and 20 min: WU20) in a hot climate (~31 C), on thermal comfort, power output and fatigue after a repeated-sprint test (RSA) in footballers.





Effect of alterations in whole-body cryotherapy exposure on post-match recovery markers in elite Premier League soccer players

The aim of this study was to investigate the impact of different levels of whole-body cryotherapy (WBC) exposure on subjective and objective measures of post-match recovery in footballers during a chronic exposure period.





Clubs that value their own (and/or who (have to) trust their own educational/developmental system)

I have posted some numbers regarding possible cost/benefit of "Having an academy" previously, which was about the possible revenue from academy players.


This post is about clubs actually utilizing their own players and to what extent.

In order to shed some light on that the percentage (%) of minutes played by club trained players were analysed for the season 2021/22 and domestic league matches played until 19/04/2022.


The definition of club trained players is a players who have been at their employer clubs for at least three years between the seasons during which they celebrated their 15th and 21st birthday.


Starting at league level, the numbers stretched from a record-low of 4.0% in the Greek Super League to a record-high of 26.0% in the Argentinean Liga Professional. On average, teams from the 40 leagues fielded club-trained players for 15.0% of domestic league minutes.


At the club level worldwide the Slovaks of MŠK Žilina (85.5%) needs to be mentioned as the top of clubs, followed by Envigado FC (COL) with 76,4%, CA Banfield (ARG) with 66,6%, Dynamo Kyiv (UKR) with 62,9%, CA Lanus (ARG) with 62,6% and Rosario Central (ARG) with 60,2 %. Among the 42 teams who did not use club-trained footballers are familiar names such as Brentford, Bayer Leverkusen, Bologna and Udinese.


As usual I am having a closer look on the Big-5 where Athletic Club sits at the top with 55,8% of minutes played deriving from their own players.


The figure below shows the top 30 clubs from the Big-5 leagues, with 5 from the top 10 deriving from Spain, followed by teams from League 1 (FRA) and Bundesliga (GER). Manchester United is the first Premier League club with 27,6% and Genoa CFC the first Italian site with 23,9% minutes played by club trained players.








Variations in the physical demands and technical performance of professional soccer teams over three consecutive seasons

The purpose of this study was twofold: (i) to analyze the seasonal variations in the physical demands of Turkish Super League teams considering their status in the final rankings and (ii) to analyze the seasonal variations in the technical performance of Turkish Super League teams considering their status in the final rankings.





Sprint Performance and Mechanical Force-Velocity Profile among Different Maturational Stages in Young Soccer Players

The aim of the present study was to determine the influence of maturation status on the components of the sprint force-velocity (F-V) profile in young soccer players.





Latest research in football - week 13 - 2022

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 Effects of congested match periods on acceleration and deceleration profiles in professional soccer

Reference: Biol Sport. 2022 Mar;39(2):307-317. doi: 10.5114/biolsport.2022.103725. Epub 2021 Apr 9.

Authors: Léo Djaoui, Adam Owen, Matt Newton, Pantelis Theodoros Nikolaidis, Alexandre Dellal, Karim Chamari

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Summary: The aim of the present study was to analyse the influence of congested periods of matches on the acceleration (Acc) and deceleration (Dec) profiles of elite soccer players. Twenty-three elite male professional soccer players participated in the study across 31 official matches. Assessed periods included: (i) congested periods (three to four days between games), and (ii) non-congested periods (more than four days between games). Physical activity during matches was recorded during games using a 10Hz global positioning system device, coupled with a 100 Hz accelerometer, and was analysed according to the periods. Maximal Acc- (73.2 ± 20.3 vs. 84.918.5 m), high Acc- (244.0 ± 49.5 vs. 267.0 ± 37.8 m), maximal Dec- (139.0 ± 44.8 vs. 152.039.3 m) and the total decelerating- distance (5132 ± 690 vs. 5245 ± 552 m) were lower in congested than in non-congested periods (p < 0.05, effect size 0.31-0.70). Neither a main effect of playing position nor a period*playing position interaction on Acc and Dec were observed (p > 0.05). It was concluded that Acc and Dec match activities were significantly affected during congested periods compared to non-congested highlighting a possible fatigue accumulation being responsible for the observed decrement in physical activity. Monitoring Acc and Dec metrics throughout particular periods of congested fixtures amongst professional soccer teams is advised and may be a way to assess physical and fatigue status.



#2 Characteristics of the Kicking Motion in Adolescent Male Soccer Players Who Develop Osgood-Schlatter Disease: A Prospective Study

Reference: Orthop J Sports Med. 2022 Mar 14;10(3):23259671221083567. doi: 10.1177/23259671221083567. eCollection 2022 Mar.

Authors: Seira Takei, Shuji Taketomi, Suguru Torii, Michio Tojima, Koji Kaneoka, Sakae Tanaka

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Summary: Osgood-Schlatter disease (OSD) is an apophysitis of the tibial tubercle caused by repeated traction of the patellar tendon during adolescence. Although OSD is associated more with sports such as soccer, it remains unclear whether the kicking motion itself is related to OSD onset. The purpose was to prospectively evaluate the kicking motion in adolescent soccer players who later developed OSD. The authors observed 47 Japanese adolescent male soccer players (mean age, 12 years) over 6 months in 2018-2019; none of the participants had OSD at study onset. The players underwent tibial tubercle ultrasound at baseline, and their kicking motion was evaluated using 3-dimensional (3D) motion analysis with 65 reflective markers. The 3D angle of the lumbar spine, thorax, and pelvis and the angular velocity of the hips, knees, and ankles were calculated for the support leg. The kicking motion was divided into 8 phases, and ball speed, kicking time, and positions of the support (nonkicking) leg and center of mass (COM) from the ball were calculated for each phase. Six months later, the players underwent another ultrasound and were divided into 2 groups: those diagnosed with OSD in the support leg (OSD group) and those without OSD (normal [NRL] group). All factors calculated using the kicking motion analysis at the baseline were compared between groups. There were 19 players in the OSD group and 28 players in the NRL group. Anthropometric measurements, ball speed, and kicking time were similar between the 2 groups. The forward translation of the COM and the support leg, the flexion angle of the thorax, and the rotation angle of the pelvis before impact with the ball were all significantly smaller in the OSD group than in the NRL group (P < .05). Moreover, the knee extension angular velocity of the support leg was significantly larger in the OSD group (P < .05) at ball impact. A kicking motion with small COM translation, small thoracic flexion, and small pelvic rotation before ball impact, as well as large knee extension angular velocity of the support leg at ball impact, may be associated with OSD onset.



#3 Leveling the Playing Field: A New Proposed Method to Address Relative Age- and Maturity-Related Bias in UK Male Academy Soccer Players

Reference: Front Sports Act Living. 2022 Mar 3;4:847438. doi: 10.3389/fspor.2022.847438. eCollection 2022.

Authors: Sofie Bolckmans, Janet L Starkes, Chris Towlson, Chris Barnes, Guy Parkin, Werner F Helsen

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Summary: Relative age selection bias persists within all major soccer leagues and youth soccer academies across the globe, with the relative age effect (RAE) being typically characterized as the over selection of relatively older players (who have sometimes also been shown to be early maturing). The aim of this study was to examine if a new allocation method (i) eliminates the RAE, and (ii) reduces the presence of any additional maturity-related differences in anthropometric and physical fitness characteristics which may exist between players within the same selection category. In the first phase, 1,003 academy soccer players [under (U) 9-16] from 23 UK professional soccer clubs were sampled and a clear RAE per birth quarter (Q) was observed for the overall sample (Q1 = 45.0% vs. Q4 = 9.8%) as well as for the different age categories. Using the newly suggested reallocation method, youth players were divided by allocation date which was defined as the midway point between the chronological age and the estimated developmental (ED) birthdate. Stature was used as an anthropometric reference point on the P50 of the growth curve to determine the developmental birthdate for this new method. After the reallocation of the players using ED, the distribution of players was more equally spread (Q1 = 25.3%, Q2 = 25.6%, Q3 = 22.4%, Q4 = 26.7%). After reallocation, the mean delta stature was reduced by 16.6 cm (from 40.3 ± 7.08 to 23.7 ± 4.09 cm, d = 2.87). The mean delta body mass difference after allocation was reduced by 6.7kg (from 33.2 ± 6.39 to 26.5 ± 4.85 kg, d = 1.18). The mean age difference increased from 1.8 to 3.9 years. A total of 42.7% of the sample would have been reallocated to a different age group compared to the current one. After reallocation, 45% of the anthropometric and physical fitness comparisons showed reductions in the within-group variation expressed as a percentage of coefficient of variation (CV%). The U10 players demonstrated the largest reduction in CV% (-7.6%) of the anthropometric characteristics. The U10 squad also showed the largest reduction in CV% for various physical fitness characteristics (-7.5%). By both eliminating the RAE and reducing temporary maturity-related anthropometric and physical fitness differences, soccer academies across the world may diversify and increase the size of the talent pool both for clubs and national youth teams. In conclusion, this study provides further evidence that the newly proposed allocation method shows the potential to remove the RAE and to create a more "leveled playing field" by reducing the within-group variation of anthropometric and physical fitness characteristics affording relatively younger, and eventually, late-maturing players the opportunity to develop their talent fairly.



#4 No sport for old players. A longitudinal study of aging effects on match performance in elite soccer

Reference: J Sci Med Sport. 2022 Mar 9;S1440-2440(22)00046-9. doi: 10.1016/j.jsams.2022.03.004.

Authors: Ezequiel Rey, Miguel Lorenzo-Martínez, Roberto López-Del Campo, Ricardo Resta, Carlos Lago-Peñas

Summary: This study aimed to examine the effects of age on match-related physical and technical-tactical performance in elite soccer players using a longitudinal design. Data were collected from 154 players who competed in the Spanish first division (LaLiga) between the 2012-13 and 2019-20 seasons. A total of 14,092 individual match observations were analyzed using a computerized tracking system (TRACAB, Chyronhego, New York, NY). The players were classified into five positional roles: central defenders (n = 37); external defenders (n = 44); central midfielders (n = 34); external midfielders (n = 22); and forwards (n = 17). The main results showed that (a) soccer players decreased by an average of 0.56% their total distance covered for each year that they got older. Similarly, the number of high-intensity efforts and distance covered at high-intensity running decreased by 1.80% and 1.42% per year, respectively; (b) players significantly increased their pass accuracy by an average of 0.25% each year that they got older; (c) the detrimental effect of age on total distance and high-intensity running was greater for external defenders, external midfielders, and forwards; and (d) the positive effect of age on pass accuracy was greater for central defenders and central midfielders. Elite soccer players with long-term careers were unable to maintain their match-related physical performance as they got older. However, players can annually improve their technical-tactical skills with increasing age as a possible compensation mechanism against physical performance declines related to aging.



#5 Management of anterior thigh injuries in soccer players: practical guide

Reference: BMC Sports Sci Med Rehabil. 2022 Mar 18;14(1):41. doi: 10.1186/s13102-022-00428-y.

Authors: Lasse Lempainen, Sandra Mechó, Xavier Valle, Stefano Mazzoni, Jose Villalon, Marco Freschi, Luca Stefanini, Alvaro García-Romero-Pérez, Maria Burova, Pavel Pleshkov, Ricard Pruna, Giulio Pasta, Jussi Kosola

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Summary: Most of the anterior thigh injuries are contusions or strains, however, some of these injuries can be career ending. Early diagnosis and correct treatment are key to successful outcome. Analyzing injury mechanism and adding both clinical and imaging findings, clinicians can make the right treatment decisions already often in the acute phase of the injury. Low grade contusions and muscle strains are treated well with planned rehabilitation, but complete tendon injuries or avulsions can require operative treatment. Also, neglected minor injuries could lead to chronic disabilities and time lost from play. Typical clinical presentation of anterior thigh injury is swelling and pain during hip flexion or knee extension. In more severe cases a clear gap can be palpated. Imaging methods used are ultrasound and magnetic resonance imaging (MRI) which are helpful for clinicians to determine more exact the extent of injury. MRI can identify possible tendon retractions which may need surgery. Clinicians should also be aware of other traumatic lesions affecting anterior thigh area such as myositis ossificans formation. Optimal treatment should be coordinated including acute phase treatment with rest, ice, and compression together with designed return-to-play protocol. The anatomical structure involved lines the treatment pathway. This narrative review describes these more common reasons for outpatient clinical visits for anterior thigh pain and injuries among soccer players.



#6 Small-Sided Games in Elite Football: Practical Solutions to Replicate the 4-min Match-Derived Maximal Intensities

Reference: J Strength Cond Res. 2022 Mar 23. doi: 10.1519/JSC.0000000000004249. Online ahead of print.

Authors: Andrea Riboli, Fabio Esposito, Giuseppe Coratella

Summary: The purpose of the study was to determine the area per player (ApP, m2·player-1) to replicate the maximal 4-min match-play period (4-minPeak) using small-sided or large-sided games (SSGs) lasting the same duration in elite football players. Twenty players (age: 26 ± 5 years) competing in European championship and international UEFA competitions were monitored during SSGs with (SSGwith) or without (SSGwithout) goalkeepers, both lasting 4-min. A total of 1,724 and 561 individual observations for SSGwith and SSGwithout across 99 and 34 different SSGs formats were undertaken. Whole (90-minavg) and 4-minPeak match demands were calculated. Relative (m·min-1) total, high-speed (HSRD), very high-speed (VHSRD), sprint, and acceleration/deceleration distance were collected. For both SSGwith and SSGwithout, ApP was small-to-very-largely correlated with TD, HSRD, VHSRD, and sprint, whereas an inverse trivial-to-small correlation with acceleration/deceleration was found. In SSGwith, the ApP to replicate 4-minPeak was larger (p < 0.001, effect size [ES]: 0.33-5.80) than that to mimic 90-minavg for total distance, HSRD, VHSRD, and sprint, whereas for acceleration/deceleration the ApP was lower (p < 0.001, ES: -3.13 to 0.48) for 4-minPeak. In SSGwithout, the ApP to replicate 4-minPeak was larger (p < 0.001, ES: 0.04-3.72) than that to mimic 90-minavg for HSRD, VHSRD, and sprint. Some positional differences (p < 0.05, ES: 0.22-1.10) in ApP were found. The ApP to replicate 4-minPeak was higher for SSGwith than SSGwithout (p < 0.001, ES: 0.67-3.58). These findings may help practitioners to recreate the 4-minPeak to manage ApP during SSGs in elite football.



#7 A Bayesian Approach to Predict Football Matches with Changed Home Advantage in Spectator-Free Matches after the COVID-19 Break

Reference: Entropy (Basel). 2022 Mar 4;24(3):366. doi: 10.3390/e24030366.

Authors: Jaemin Lee, Juhuhn Kim, Hyunho Kim, Jong-Seok Lee

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Summary: Since the coronavirus disease 2019 (COVID-19) pandemic, most professional sports events have been held without spectators. It is generally believed that home teams deprived of enthusiastic support from their home fans experience reduced benefits of playing on their home fields, thus becoming less likely to win. This study attempts to confirm if this belief is true in four major European football leagues through statistical analysis. This study proposes a Bayesian hierarchical Poisson model to estimate parameters reflecting the home advantage and the change in such advantage. These parameters are used to improve the performance of machine-learning-based prediction models for football matches played after the COVID-19 break. The study describes the statistical analysis on the impact of the COVID-19 pandemic on football match results in terms of the expected score and goal difference. It also shows that estimated parameters from the proposed model reflect the changed home advantage. Finally, the study verifies that these parameters, when included as additional features, enhance the performance of various football match prediction models. The home advantage in European football matches has changed because of the behind-closed-doors policy implemented due to the COVID-19 pandemic. Using parameters reflecting the pandemic's impact, it is possible to predict more precise results of spectator-free matches after the COVID-19 break.



#8 Change of Direction Speed and Reactive Agility in Prediction of Injury in Football; Prospective Analysis over One Half-Season

Reference: Healthcare (Basel). 2022 Feb 25;10(3):440. doi: 10.3390/healthcare10030440.

Authors: Dragan Mijatovic, Dragan Krivokapic, Sime Versic, Goran Dimitric, Natasa Zenic

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Summary: Agility is an important factor in football (soccer), but studies have rarely examined the influences of different agility components on the likelihood of being injured in football. This study aimed to prospectively evaluate the possible influences of sporting factors, i.e., flexibility, reactive agility (RAG), and change of direction speed (CODS), on injury occurrence over one competitive half-season, in professional football players. Participants were 129 football professional players (all males, 24.4 ± 4.7 years), who underwent anthropometrics, flexibility, and RAG and CODS (both evaluated on non-dominant and dominant side) at the beginning of second half-season 2019/20 (predictors). Over the following half-season, occurrence of injury was registered (outcome). To identify the differences between groups based on injury occurrence, t-test was used. Univariate and multivariate logistic regressions were calculated to identify the associations between predictors and outcome. Results showed incidence of 1.3 injuries per 1000 h of training/game per player, with higher likelihood for injury occurrence during game than during training (Odds Ratio (OR) = 3.1, 95%CI: 1.63-5.88) Univariate logistic regression showed significant associations between players' age (OR = 1.65, 95%CI: 1.25-2.22), playing time (OR = 2.01, 95%CI: 1.560-2.58), and RAG (OR = 1.21, 95%CI: 1.09-1.35, and OR = 1.18, 95%CI: 1.04-1.33 for RAG on dominant- and non-dominant side, respectively), and injury occurrence. The multivariate logistic regression model identified higher risk for injury in those players with longer playing times (OR = 1.81, 95%CI: 1.55-2.11), and poorer results for RAG for the non-dominant side (OR = 1.15, 95%CI: 1.02-1.28). To target those players who are more at risk of injury, special attention should be paid to players who are more involved in games, and those who with poorer RAG. Development of RAG on the non-dominant side should be beneficial for reducing the risk of injury in this sport.



#9 Effects of Mobile-Based Rehabilitation in Adolescent Football Players with Recurrent Lateral Ankle Sprains during the COVID-19 Pandemic

Reference: Healthcare (Basel). 2022 Feb 22;10(3):412. doi: 10.3390/healthcare10030412.

Authors: Xiaobo Qu, Kai Li, Sangcheul Nam

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Summary: Football is a sport involving dynamic movements, and ankle sprains are common sports injuries experienced by football players. Ankle sprains exhibit a high recurrence rate, and rehabilitation training is effective; however, expert-supervised rehabilitation (SVR) at training centers is difficult due to the recent COVID-19 pandemic. This study investigated the effects of mobile-based rehabilitation (MBR) performed at home by high school football players. Sixty players (SVR: 30 and MBR: 30) with recurrent ankle sprains were analyzed. The rehabilitation program consisted of strength and balance training, and the training intensity was gradually increased from week 1 to week 8. The SVR group underwent training at the center with experts, and the BMR group were provided with programs and feedback using mobile devices. Ankle muscle strength was evaluated by measuring isometric eversion, inversion, plantarflexion, and dorsiflexion contraction using a hand-held dynamometer, and dynamic balance was assessed using the Y-balance test (YBT; anterior, posteromedial, and posterolateral); the Foot and Ankle Outcome Score (FAOS) was used for the subjective evaluation. Measurements were conducted at weeks 1, 4, and 8. The patients visited the clinic within 1 week after the injury, and the first test was conducted after consent to participate in the research. Patients underwent the second test at an average of 3.2 weeks after the first test, and the last test at an average of 4.4 weeks after the second test. Although only the SVR group exhibited improvement in strength (eversion and dorsiflexion), YBT and subjective satisfaction at week 4, these measurements improved in both the SVR and MBR groups at week 8. Therefore, mobile-based rehabilitation could be a suitable alternative for high school athletes with ankle sprains who cannot undergo supervised rehabilitation.



#10 Does Femoroacetabular Impingement Syndrome Affect Self-Reported Burden in Football Players With Hip and Groin Pain?

Reference: Sports Health. 2022 Mar 23;19417381221076141. doi: 10.1177/19417381221076141. 

Authors: Mark J Scholes, Joanne L Kemp, Benjamin F Mentiplay, Joshua J Heerey, Rintje Agricola, Adam I Semciw, Richard B Souza, Thomas M Link, Sharmila Majumdar, Matthew G King, Peter R Lawrenson, Kay M Crossley

Summary: It is unknown if football players with femoroacetabular impingement (FAI) syndrome report worse burden than those with other causes of hip/groin pain, and to what extent this is mediated by cartilage defects and labral tears. Football players with FAI syndrome would report worse burden than other symptomatic players, with the effect partially mediated by cartilage defects and/or labral tears. Football (soccer and Australian football) players (n = 165; 35 women) with hip/groin pain (≥6 months and positive flexion-adduction-internal rotation test) were recruited. Participants completed 2 patient-reported outcome measures (PROMs; the International Hip Outcome Tool-33 [iHOT-33] and Copenhagen Hip and Groin Outcome Score [HAGOS]) and underwent hip radiographs and magnetic resonance imaging (MRI). FAI syndrome was determined to be present when cam and/or pincer morphology were present. Cartilage defects and labral tears were graded as present or absent using MRI. Linear regression models investigated relationships between FAI syndrome (dichotomous independent variable) and PROM scores (dependent variables). Mediation analyses investigated the effect of cartilage defects and labral tears on these relationships. FAI syndrome was not related to PROM scores (unadjusted b values ranged from -4.693 (P = 0.23) to 0.337 (P = 0.93)) and cartilage defects and/or labral tears did not mediate its effect (P = 0.22-0.97).

Conclusion: Football players with FAI syndrome did not report worse burden than those with other causes of hip/groin pain. Cartilage defects and/or labral tears did not explain the effect of FAI syndrome on reported burden.

Clinical relevance: FAI syndrome, cartilage defects, and labral tears were prevalent but unrelated to reported burden in symptomatic football players.



#11 The Effectiveness of Psychological Workshops for Coaches on Well-Being and Psychomotor Performance of Children Practicing Football and Gymnastics

Reference: J Sports Sci Med. 2021 Oct 1;20(4):586-593. doi: 10.52082/jssm.2021.586. eCollection 2021 Dec.

Authors: Dominika Wilczyńska, Anna Łysak-Radomska, Magdalena Podczarska-Głowacka, Wojciech Skrobot, Katarzyna Krasowska, Ewelina Perzanowska, Tomasz Dancewicz, Patrycja Lipińska, Will G Hopkins

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Summary: Coach workshops based on seven principles (inspiration, explanation, expectation, support, reward, appreciation, growth and winning) enhance the sport experience of adult athletes. Therefore, we have investigated the effects of such workshops with coaches of child athletes. Study participants were coaches of 57 9- to 12-year old girls (practicing gymnastics) and boys (practicing football). Three coaches of 28 children attended three workshops over 12 weeks, while a control group of 5 coaches of 29 children attended no workshops. Measures of well-being and psychomotor performance were taken on the children before and after the intervention; differences in mean changes between intervention and control groups were adjusted for baseline, standardized, and assessed with a conservative magnitude-based decision method. There were clear substantial effects of the workshop on motivation averaged across several dimensions (girls, large, most likely beneficial), on a decision test (boys, small-moderate, very likely beneficial), on state anxiety self-reflection (girls, moderate, likely harmful), and on reaction time (boys, small, possibly harmful). The beneficial effects of the workshop in this pilot study are encouraging, but the unclear and potentially harmful effects and the roles of presenter- and coach-specific effects need to be investigated further with a representative sample of coaches and more children before the workshop is recommended for implementation.



#12 International football players with cerebral palsy maintained their physical fitness after a self-training program during the COVID-19 lockdown

Reference: PeerJ. 2022 Mar 17;10:e13059. doi: 10.7717/peerj.13059. eCollection 2022.

Authors: Iván Peña-González, José Manuel Sarabia, Agustín Manresa-Rocamora, Manuel Moya-Ramón

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Summary: The COVID-19 global pandemic caused a complete stop in sport participation which meant a detraining period for athletes. High-level athletes had to train at home guided by their coaches and conditioning trainers in an effort to maintain their physical fitness. The aim of maintaining the training adaptations and physical fitness during the COVID-19 mandatory lockdown was especially important for CP athletes, in which the detraining period was expected to cause early declines in motor function, poor coordination and muscle weakness due to their disability. The present study assessed the effect of a guided self-training program on international CP football players' physical fitness during the COVID-19 mandatory lockdown. Fifteen CP football players from the Spanish National Team participated in the study. An experimental design with a pre- (T1) and a post-intervention (T2) assessment was carried out, with a 12-week period of players' self-training (divided in two periods of 6 weeks) which combined strength and endurance training. Physical performance assessment consisted in the free countermovement jump (CMJ), 5, 10 and 20-m sprint, the modified agility T-test (MAT) and a dribbling test. The Kruskal-Wallis test was used for between-group comparisons, while the Student's paired t test or the Fisher Pitman permutation test, based on the normality of the data, were used for within-group comparisons. The results showed no differences between sport classes (FT1, FT2 and FT3) in physical fitness change after the training program (Chi2 = 0.16 to 1.73; p = 0.42 to 0.92). Within-group comparisons showed an increase of jump height in the CMJ (4.19 cm [2.46, 5.93]; p < 0.001) and a maintenance of the 5, 10 and 20-m sprint, MAT and dribbling ability (<0.01 to 0.09 s; p = 0.19 to 0.97). To the authors' knowledge, this is the first study that examined the physical fitness adaptations to a training program with CP football players. The results show that a 12-week guided self-training program without football-specific stimulus may be effective to maintain or even improve the specific physical performance of international CP football players during a non-competitive period (as the COVID-19 lockdown). This study reveals that CP football players are able to show adaptations to the strength and endurance training and this could be the basis for future research regarding training adaptations in CP football players.



#13 Return to match running performance after a hamstring injury in elite football: a single-centre retrospective cohort study

Reference: BMJ Open Sport Exerc Med. 2022 Feb 24;8(1):e001240. doi: 10.1136/bmjsem-2021-001240. eCollection 2022.

Authors: Marloes I Hoppen, Gustaaf Reurink, Vosse A de Boode, Lisanne van der Kaaden, Lotte Jagtman, Tim Glazenburg, Bastiaan Bruning, Johannes L Tol

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Summary: The aim was to determine the number of matches to return to pre-injury match running performance after sustaining an acute hamstring injury. In this retrospective cohort study, the injuries of the players of the first, Under21, Under19, Under18 and Under17 teams of a professional football club in the period 2017-2020 were analysed. Acute hamstring injuries with a minimal absence from training or match play of 7 days were included. For running performance, we assessed the following variables: maximal velocity (km/hour), total distance, high-intensity distance (17.5-22.5 km/hour) and sprint distance (>22.5 km/hour). We calculated the average and 95% CI for these variables during the last five matches before the injury. The primary outcome was the number of matches to reach maximal velocity within the 95% CI of the player's individual pre-injury performance. Secondary outcome scores included the duration (in days and matches) to reach the other running performance variables. 18 hamstring injuries in 15 players were included. 15 out of 18 injuries (83%) showed a return to pre-injury maximal velocity in the second match after return to play. The median number of matches to return to pre-injury maximal velocity was 2 (IQR 1-2). In the first match after return to play, pre-injury total distance was reached in 100% of the injuries, pre-injury sprint distance was reached in 94% of the injuries and pre-injury high-intensity distance was reached in 89% of the injuries. Following an acute hamstring injury in elite football, pre-injury match running performance is reached in the first or second match.



#14 The Faroe Islands COVID-19 Recreational Football Study: Player-to-Player Distance, Body-to-Body Contact, Body-to-Ball Contact and Exercise Intensity during Various Types of Football Training for Both Genders and Various Age Groups

Reference: Biomed Res Int. 2022 Mar 17;2022:6822385. doi: 10.1155/2022/6822385. eCollection 2022.

Authors: Magni Mohr, Tórur Sjúrðarson, Eli N Leifsson, Morten B Randers, Nikolas Sten Knudsen, Manuel Mounir Demetry Thomasen, Jeppe Panduro, Malte Nejst Larsen, Thomas Bull Andersen, Peter Krustrup

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Summary: We determined player-to-player distance, body-to-ball contact, and exercise intensity during three training modalities in various football populations. 213 participants were recruited, ranging from 9-year-old boys to young men and 11-year-old girls to middle-aged women. All groups were analysed with video-filming and GPS-based Polar Pro monitors during three types of football training for 20 min, i.e., COVID-19-modified training (CMT) with >2-metre player-to-player distance, small-sided games (SSG), and simulated match-play with normal rules (SMP), in randomised order. Time spent in a danger zone (1.5 m) per-percent-infected-player (DZ PPIP) ranged from 0.015 to 0.279% of playing time. DZ PPIP for SSG was higher (P < 0.05) than CMT and SMP. The average number of contacts (within 1.5 m) with a potentially infected player ranged from 12 to 73 contacts/hour. SSG had more (P < 0.05) contacts than CMT and SMP, with SMP having a higher (P < 0.05) number of contacts than CMT. Time/contact ranged from 0.87 to 3.00 seconds for the groups. No player-to-player and body-to-ball touches were registered for CMT. Total player-to-player contacts were 264% higher (P < 0.05) in SSG than SMP, ranging from 80 to 170 and 25 to 56 touches, respectively. In all groups, a greater total distance was covered during SMP compared to CMT (38-114%; P < 0.05). All groups performed more high-intensity running (33-54%; P < 0.05) and had higher heart rates during SMP compared to CMT. Different types of football training all appear to exert a minor COVID-19 infection risk; however, COVID-19-modified training may be safer than small-sided game training, but also match-play. In contrast, exercise intensity is lower during COVID-19-modified training than match-play.



#15 Osgood-Schlatter Disease in youth elite football: Minimal time-loss and no association with clinical and ultrasonographic factors

Reference: Phys Ther Sport. 2022 Mar 9;55:98-105. doi: 10.1016/j.ptsp.2022.02.024. Online ahead of print.

Authors: Mohamed Schultz, Johannes L Tol, Linda Veltman, Lisanne Kaaden van der, Gustaaf Reurink

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Summary: Osgood-Schlatter Disease is the most common cause of knee pain in youth. Scientific research in youth elite football is limited. The aim was to assess clinical and ultrasonographic factors associated with Osgood-Schlatter Disease and calculate point prevalence of clinical diagnosis and time-loss in youth elite male football. We obtained data during the pre-season periodic health evaluation. Osgood-Schlatter Disease diagnosis was defined as (1) athlete-reported anterior knee pain and (2) clinical confirmation by pain provocation at the tibial tuberosity. Time-loss was defined as inability to participate in team training and/or competition. For the nested-case control study, we examined clinical and ultrasonographic factors in the U13 to U16 teams. We matched on calendar-age. The clinical factors were: self-reported history of Sever's disease, growth measures, leg muscles flexibility and strength and ultrasonographic bone maturity stages according to Ehrenborg, For the cross-sectional study, we included players of the U13 to U19 teams to calculate the point prevalence. The case-control study consisted 30 players and the cross-sectional study 127 players. Previous Sever's disease was strongly associated with Osgood-Schlatter Disease (OR = 16.8; p = 0.02; 95% CI = 1.6-174.5). None of the other clinical or ultrasonographic factors were associated. The point prevalence was 17% and 80% had no time-loss despite presence of clinical symptoms. Considering the 16.8OR, previous Sever's disease indicates a strong association with Osgood-Schlatter Disease. Although generally suggested, growth velocity and bone maturity are not associated in an age-matched comparison.



#16 Cognitive and Physical Effects of Warm-Up on Young Soccer Players

Reference: Motor Control. 2022 Mar 29;1-19. doi: 10.1123/mc.2021-0128. Online ahead of print.

Authors: Francisco Tomás González-Fernández, Hugo Sarmento, Sixto González-Víllora, Juan Carlos Pastor-Vicedo, Luis Manuel Martínez-Aranda, Filipe Manuel Clemente

Summary: This study analyzed the effects of with (WC) or without conducting a warm up on youth soccer players immediately before performing physical and cognitive tests. Fourteen youth soccer player (age 11.64 ± 0.50) participated in a counterbalanced cross-sectional study in which three conditions were tested: (a) basal lineal condition; (b) WC (immediately before the physical and cognitive tests); and (c) without WC (passive resting for 15 min between the warm-up and physical and cognitive tests). A 30-m sprint test, countermovement jump, and psychomotor vigilance task were also applied. The WC revealed significant improvements in countermovement jump (p < .05), 30-m sprint test performance (p < .05), and reaction time in psychomotor vigilance task (p < .05) in comparison to basal lineal condition and without WC. A 15-min rest after a warm-up has a meaningfully decremental effect on the physical and cognitive readiness of youth soccer players, in comparison with when they warm-up immediately before the demands are imposed.



#17 Acute Effects of Soleus Stretching on Ankle Flexibility, Dynamic Balance and Speed Performances in Soccer Players

Reference: Biology (Basel). 2022 Feb 26;11(3):374. doi: 10.3390/biology11030374.

Authors: Shi Huang, Hong-Jia Zhang, Xin Wang, Winson Chiu-Chun Lee, Wing-Kai Lam

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Summary: Most dynamic stretching protocols include the gastrocnemius muscle, but soleus stretches are often neglected, which is the key powerful muscle for the push-off (concentric) of all speed movements. The purpose of this study was to examine whether the added soleus stretch in a regular stretching protocol would have greater benefits for ankle flexibility, dynamic balance and functional performance. Fourteen healthy male soccer players received each of the stretching conditions (regular stretching only (Regular), regular stretching with soleus stretching (Soleus) and no stretching (Control)) randomly on different training days, with two-day separation. The ankle flexibility, standing heel-lift balance and speed performances were assessed following each stretching intervention. The active dynamic stretches were performed for 30 s with three repetitions on each of the three (Regular) and four (Soleus) muscles. One-way ANOVA with repeated measures (or the Friedman non-parametric test) was performed to determine any significant effect with alpha = 0.05. Our findings revealed that both the Regular and Soleus stretching groups showed an increased active range of ankle motion compared to the no-stretching control (Ps &lt; 0.05). In the heel raise balance test, both stretching groups experienced a significant increase in maximum plantarflexion strength as well as resultant anterior-posterior and medial-lateral CoP excursions compared to the no-stretching control (Ps &lt; 0.05). In the sprinting tasks, both the Soleus and Regular stretching groups induced faster linear and curved running times (Ps &lt; 0.05). When comparing the two stretching groups, Soleus stretching led to better ankle flexibility, maximum plantarflexion strength and curved running time (Ps &lt; 0.05). Thus, added stretches on the soleus muscles can provide further benefits to speed performances in soccer.



#18 In-Season Quantification and Relationship of External and Internal Intensity, Sleep Quality, and Psychological or Physical Stressors of Semi-Professional Soccer Players

Reference: Biology (Basel). 2022 Mar 18;11(3):467. doi: 10.3390/biology11030467.

Authors: Hadi Nobari, Roghayyeh Gholizadeh, Alexandre Duarte Martins, Georgian Badicu, Rafael Oliveira

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Summary: The purpose of this study was two-fold: (a) to describe and analyse the relationship of the in-season variations of external and internal intensity metrics as well as well-being measures across different periods of a semi-professional soccer season (early-, mid- and end-season); and (b) to describe training monotony (TM) and training strain (TS) for 20 weeks in a semi-professional soccer season. Eighteen semi-professional players (age: 29 ± 4.1) from the Asian First League team participated in this study. The players were monitored for 20 consecutive weeks during in-season for external training intensity, internal training intensity and well-being parameters. The in-season was organized into three periods: early-season (weeks 1-7); mid-season (weeks 8-13); and end-season (weeks 14-20). Total distance (TD), high-speed running distance (HSRD), sprint distance, rate of perceived exertion (RPE), session-RPE (s-RPE), TM, TS, heart rate average and maximum, as well as sleep quality, stress and muscle soreness were collected. Results revealed that TD, HSRD and sprint distance (total values) were meaningfully greater during end-season than in the early-season. RPE showed a significantly highest value during the end-season (4.27 AU) than in early- (3.68 AU) and mid-season (3.65 AU), p &lt; 0.01. TS showed significant differences between early-season with mid-season (p = 0.011) and end-season (p &lt; 0.01), and the highest value occurred in week 17 during end-season (6656.51 AU), while the lowest value occurred in week 4 during early-season (797.17 AU). The average TD periods showed a moderate to large correlation with RPE, sleep and s-RPE at early-, mid- and end-season. Increasing the training intensity without considering the well-being of the players affects the performance of the team. Examining processes of the relationship between training intensity and other psychological indicators among players will probably be effective in training planning. Sports coaches and fitness professionals should be wary of changes in TM and TS that affect players performance. Therefore, to better control the training, more consideration should be given by the coaches.



#19 The Impact of 120 Minutes of Soccer-Specific Exercise on Recovery

Reference: Res Q Exerc Sport. 2022 Mar 28;1-9. doi: 10.1080/02701367.2021.1964697. Online ahead of print.

Authors: Adam Field, Liam David Corr, Hugo Sarmento, Robert Naughton, Tom Clifford, Matthew Haines, Richard Michael Page, Liam David Harper

Summary: The extra-time (ET) period of soccer is competed during fixture congested schedules with often limited recovery time between matches. The aim of this study was to assess muscle damage recovery following 90- and 120-min (i.e., incorporation of ET) of simulated soccer match-play. Twelve semiprofessional soccer players completed 90 and 120-min treadmill-based soccer-specific exercise in a counterbalanced order. Creatine kinase (CK), creatinine, urea, aspartate aminotransferase, perceived muscle soreness, pain pressure threshold, reactive strength index, countermovement jump height, and isokinetic strength assessments of eccentric knee flexors at 60, 180 and 270 deg‧s-1 were taken at baseline and immediately-, 24, 48 and 72-hr post-exercise to assess recovery. No significant between-trial interactions except for CK were found. Pairwise comparisons detected a 53% increase in CK at 24-hr (455 ± 29 μ∙L-1) following 120-min of simulated match-play vs. the corresponding post 90-min time-point (299 ± 29 μ∙L-1; p < .01). The 120-min trial caused a 58% higher CK response at 72-hr (244 ± 25 μ∙L-1) vs. post 90-min comparisons (154 ± 29 μ∙L-1; p = .02). No interaction effects were detected for any other recovery variables. Creatine kinase and perceived muscle soreness remained elevated up to 72-hr in both trials (p < .01). These data indicate that 120 min of simulated soccer match-play delays the time-course of CK recovery up to 72-hr post-match. However, 120 min of simulated soccer has no additional impact on functional recovery and perceived muscle soreness vs. 90 min. Recovery should be investigated following 90- and 120-min of actual match-play.



#20 Are acute:chronic workload ratios of perceived exertion and running based variables sensible to detect variations between player positions over the season? A soccer team study

Reference: BMC Sports Sci Med Rehabil. 2022 Mar 28;14(1):51. doi: 10.1186/s13102-022-00445-x.

Authors: Hadi Nobari, Ersan Arslan, Alexandre Duarte Martins, Rafael Oliveira

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Summary: The aim of this study was to describe and compare the in-season variations of acute: chronic workload ratio (ACWR) coupled, uncoupled, and exponentially weighted moving average (EWMA) through session rating of perceived exertion (s-RPE), total distance (TD), high-speed running distance (HSRD) and sprint distance (SPRINT) in three different periods of an elite soccer season according to player positions. Twenty male elite players (age: 29.4 ± 4.4) from an Asian First League team were daily monitored for twenty consecutive weeks during the 2017-2018 in-season. Forty-seven trainings and twenty matches were monitored using global positioning system units (GPS) to collect TD, HSRD and SPRINT. Through the collection of s-RPE, TD, HSRD, and SPRINT by ACWR and EWMA were calculated for each training session. The results revealed that according to different periods of the season, workload measures observed in mid-season were meaningfully higher compared with early-season (g = ranging from 0.53 to 4.98) except for EWMASPRINT. In general, wingers and strikers tended to have greater scores in workload measures compared to the defenders and midfielders (g = ranging from 0.41 to 5.42). These findings may provide detailed information for coaches and sports scientists regarding the variations of acute and chronic workload ratio and external loading in-season and between player positions in an elite soccer team.



#21 Regional phase angle, not whole-body, is augmented in response to pre-season in professional soccer players

Reference: Res Sports Med. 2022 Mar 28;1-15. doi: 10.1080/15438627.2022.2052069. Online ahead of print.

Authors: Renêe de Caldas Honorato, Alex Soares Marreiros Ferraz, Witalo Kassiano, Priscila Custódio Martins, Diego Augusto Santos Silva, Vânia Marilande Ceccatto

Summary: The objective of this article was to assess the effects of six-week pre-season training on whole-body and regional bioelectrical impedance analysis (BIA)-derived parameters, body composition, power, and aerobic performance in professional soccer players. Ten professional soccer athletes participated in the present study. Whole-body and regional hamstrings BIA-derived parameters [resistance, reactance, impedance, phase angle (PhA)], body composition, total body water (TBW), intracellular (ICW), and extracellular (ECW) were measured before, at mid-point, and after sixth week of the pre-season. Power (countermovement jump and squat jump) and aerobic capacity (Yo-Yo test) were measured before and after pre-season. There was a significant increase in the regional PhA (+13.9%) but not in the whole-body. There was a reduction in fat mass (-4.1%), an increase in fat-free mass (+1.7%), TBW (+8.3%), ICW (+8.8%), and ECW (+7.6%), as well as an increase in jump height (+11.0%) and distance covered in the Yo-Yo test (+34.7%). From our results, it is possible to suggest that pre-season training can induce an increase in hamstring PhA as well as body recomposition and improvement of physical fitness in professional soccer players.



#22 Does anticipation of penalty kicks in soccer transfer across similar and dissimilar sports?

Reference: Cogn Process. 2022 Mar 30. doi: 10.1007/s10339-021-01073-y. Online ahead of print.

Authors: Matthew Andrew, Joe Causer

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Summary: The aim of the present study was to examine whether anticipation skill associated with penalty-kick scenarios is sport-specific, or whether it transfers between sports that have similar elements. A shortened participation history questionnaire was used to identify 97 soccer players, 47 invasion sport players (e.g., rugby), and 72 other sport players (e.g., swimming), as well as skill level (hours of engagement/competition level). These participants completed a video-based temporal occlusion anticipation test that required them to select the destination of the ball across a series of soccer penalty scenarios. Results indicated that the skilled soccer players were more accurate than the skilled and less-skilled invasion sport players and skilled and less-skilled other sport players. Skilled soccer players were also more accurate than the less-skilled soccer players, with less-skilled soccer players exhibiting similar accuracy to both the skilled and less-skilled invasion sport and other sport players indicating that processes associated with anticipation of penalty kicks may be specific to their sport.






Training load responses to football game profile-based training formats: effects of locomotive demands manipulation

The aim of this study was to compare internal and external load profiles of different game profile based training (GPBT) formats among elite young football players.





Accumulative weekly load in a professional football team: with special reference to match playing time and game position

The aim of this study was to compare weekly accumulative load during the in-season competitive period by professional soccer players according to the amount of time played in official matches (90-min, >60-min, <60-min, and 0-min) regarding the players’ position.





Latest research in football - week 12 - 2022

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 The prevalence and effect of the sites of pain in female soccer players with medial shin pain

Reference: J Sports Med Phys Fitness. 2022 Mar 25. doi: 10.23736/S0022-4707.22.13655-8. Online ahead of print.

Authors: Takumi Okunuki, Hirohisa Magoshi, Toshihiro Maemichi, Zijian Liu, Hirofumi Tanaka, Masatomo Matsumoto, Takuma Hoshiba, Tsukasa Kumai

Summary: Female soccer players are often diagnosed with medial shin pain, which includes tibial stress fracture, medial tibial stress syndrome, and chronic exertional compartment syndrome. As the possibility of varied sites of pain affecting sports activities has not been fully researched, an urgent discussion and evidence is required. This study investigates the prevalence and effect of sites of pain on the sports activities of female soccer players with medial shin pain. A questionnaire survey was conducted for 196 female soccer players with medial shin pain to assess symptom duration, the effect of practice and performance, and sites of pain. The players were classified into three conditions (tibial stress fracture, medial tibial stress syndrome, or medial shin pain with neurological symptoms) and compared based on sites of pain. We observed that medial tibial stress syndrome had a lower impact on performance compared to that of tibial stress fracture and medial shin pain with neurological symptoms. While participants with tibial stress fracture had to suspend practice sessions more frequently, the difference in symptom duration between the classified groups was not statistically significant. The effect of sites of pain on sports activities was not significantly different in participants with medial tibial stress syndrome. Medial shin pain should be evaluated carefully to differentiate between medial tibial stress syndrome and medial shin pain with neurological symptoms. Restriction of sports activities may help improve the patient's condition early, regardless of the presentation.



#2 Blood Pressure and Heart Rate Responses to an Isokinetic Testing Protocol in Professional Soccer Players

Reference: J Clin Med. 2022 Mar 11;11(6):1539. doi: 10.3390/jcm11061539.

Authors: Arturo Pérez-Gosalvez, Francisco García-Muro San José, Ofelia Carrión-Otero, Tomás Pérez-Fernández, Luis Fernández-Rosa

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Summary: The aim of this study was to determine blood pressure (BP) and heart rate (HR) responses triggered during an isokinetic testing protocol in professional soccer players and compare cardiovascular parameters at completion of this isokinetic protocol with those during a treadmill test. Using purposive sampling, 63 professional soccer players were recruited. Cardiovascular responses were measured noninvasively during a bilateral testing protocol of knee flexion and extension. Treadmill ergospirometry following an incremental speed protocol was performed to analyze the same cardiovascular parameters at rest and at completion of this test. There were significant differences in diastolic blood pressure (DBP) and HR according to field position. The parameters presented high homogeneity at both competitive levels. Systolic blood pressure, mean arterial pressure, HR, and rate pressure product at completion of the treadmill test were significantly higher than those at completion of the isokinetic protocol. Intermittent isokinetic testing protocol of the knee triggers normal and safe BP and HR responses in healthy professional soccer players. The HR of the defenders was higher than those of the forwards and midfielders but was independent of the competitive level. The values of cardiovascular parameters at isokinetic protocol completion were lower than those during the treadmill test.



#3 Body Composition Interactions with Physical Fitness: A Cross-Sectional Study in Youth Soccer Players

Reference: Int J Environ Res Public Health. 2022 Mar 18;19(6):3598. doi: 10.3390/ijerph19063598.

Authors: César Leão, Ana Filipa Silva, Georgian Badicu, Filipe Manuel Clemente, Roberto Carvutto, Gianpiero Greco, Stefania Cataldi, Francesco Fischetti

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Summary: This study aimed to: (i) analyze fat mass and physical fitness variations among age-groups and playing positions, and (ii) explore the relationship between fat mass and physical fitness in youth male soccer players. A total of 66 players from under-16, under-17, and under-19 were tested. Body mass, skinfolds, countermovement jump (CMJ), single-leg triple hop jump (SLTH), bilateral triple hop jump (BTH), and yo-yo intermittent recovery Level 2 (YYIR-2) were assessed. A two- and one-way ANOVA were conducted, and the effect size was measured. Interactions were found in skin folds and fat mass. The under-19 group was taller, heavier, with a greater BMI and muscle mass than the under-16 group. They also exceeded the under-16 and under-17 in SLTH, BTH, and YYIRT-2. The under-17 group jumped higher and longer than under-16 group. Goalkeepers were taller and heavier than the midfielders. Central defenders were taller and had more muscle mass than midfielders and were heavier than the midfielders and wingers. The wingers jumped higher than the midfielders and showed better YYIRT-2. BMI was small correlated with YYIRT-2 and moderately with CMJ. Fat mass had a moderate negative correlation with CMJ and YYIRT-2. Muscle mass largely correlated with CMJ, UTH, very large with BTH and moderate with YYIRT-2. Summarily, with increasing age, better performances and body compositions were registered. Muscle mass better influences performance than body fat. Body composition can distinguish players positions.



#4 Using Coordinated Visual and Verbal Cues in Complex Multimedia Materials to Improve Tactical Learning in Soccer

Reference: Int J Environ Res Public Health. 2022 Mar 12;19(6):3365. doi: 10.3390/ijerph19063365.

Authors: Nourhen Mezghanni, Ghazi Rekik, Zachary J Crowley-McHattan, Yosra Belkhir, Rayda Ben Ayed, Atyh Hadadi, Turki Mohsen Alzahrani, Cheng-Deng Kuo, Yung-Sheng Chen

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Summary: This study aimed to explore whether the use of coordinated visual and verbal cues in narrated diagrams would support novices in learning soccer scenes. Eighty female university students (Mage = 20 years, SD = 1.2) in physical education (PE) were randomly exposed to four multimedia material versions: (a) simple without cues, (b) simple with cues, (c) complex without cues, and (d) complex with cues. In the non-cued versions, students learned the evolution of soccer scenes via arrow-based diagrams accompanied by oral explanations. In the cued versions, game actions in narrations were spoken with a louder accent (verbal cueing), while at the same time, the corresponding arrows turned red in diagrams (visual cueing). After studying one of the four versions, participants were asked to complete immediate and delayed recall-reconstruction tests, and to indicate their attitudes towards instructional materials. The results demonstrate the instructional benefits of using coordinated dual-modality cues in the complex multimedia material, in terms of immediate (p = 0.03, d = 0.53) and delayed (p = 0.02, d = 0.85) recall performances. The findings encourage soccer teachers to verbalize game actions with a louder accent, while simultaneously coloring the corresponding arrows in the diagram when explaining complex game situations for novices.



#5 Countermovement Jump Force-Time Curve Analysis between Strength-Matched Male and Female Soccer Players

Reference: Int J Environ Res Public Health. 2022 Mar 12;19(6):3352. doi: 10.3390/ijerph19063352.

Authors: Christopher Thomas, Paul A Jones, Thomas Dos'Santos

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Summary: The purpose of this study was to compare countermovement jump force-time measures between strength-matched male and female soccer players. Males (n = 11) and females (n = 11) were strength-matched via isometric mid-thigh pull testing, whereby peak force values were normalised to body mass. Subjects performed three maximal-effort countermovement jumps (CMJs) on a force platform from which a range of kinetic and kinematic variables were calculated via forward dynamics. Thereafter, differences in gross measures were examined via independent t-tests, while differences in force-, power-, velocity-, and displacement-time curves throughout the entire CMJ were analysed using statistical parametric mapping (SPM). Jump height, reactive strength index modified, propulsion mean force, propulsion impulse, and propulsion mean velocity were all greater for males (d = 1.50 to 3.07). Relative force- and velocity-time curves were greater for males at 86-93% (latter half of the concentric phase) and 85-100% (latter half of the concentric phase) of normalized movement time, respectively. Time to take-off, braking phase time, braking mean velocity and impulse, propulsion phase time and centre of mass displacement were similar between males and females (d = -0.23 to 0.97). This research demonstrates the strength of SPM to identify changes between entire force-time curves. Continued development and the use of SPM analysis could present the opportunity for a refined comparison of strength-matched male and female CMJ performance with the analysis of entire force-time curves.



#6 Injury risk is greater in physically mature versus biologically younger male soccer players from academies in different countries

Reference: Phys Ther Sport. 2022 Mar 17;55:111-118. doi: 10.1016/j.ptsp.2022.03.006. Online ahead of print.

Authors: Elliott C R Hall, Jon Larruskain, Susana M Gil, Josean A Lekue, Philipp Baumert, Edgardo Rienzi, Sacha Moreno, Marcio Tannure, Conall F Murtagh, Jack D Ade, Paul Squires, Patrick Orme, Liam Anderson, Craig M Whitworth-Turner, James P Morton, Barry Drust, Alun G Williams, Robert M Erskine

Summary: The aim was to investigate if maturity status was associated with injury risk in male academy soccer players. 501 players (aged 9-23 years) from eight academies in England, Spain, Uruguay and Brazil participated in this study. Players were grouped by maturity offset as pre-peak height velocity (PHV), circa-PHV, post-PHV or adult. Injury prevalence proportion (IPP) and days missed were recorded for one season per player, with training/match exposure recorded in a sub-sample (n = 166). IPP for all injuries combined increased with advancing maturity, with circa-PHV (p = 0.032), post-PHV (p < 0.001) and adult (p < 0.001) higher than pre-PHV. IPP was higher in post-PHV and adult than pre-PHV for non-contact (p = 0.001 and p = 0.012), soft-tissue (both p < 0.001), non-contact soft-tissue (p < 0.001 and p = 0.005), muscle (both p < 0.001), thigh (both p < 0.001), ankle (p = 0.035 and p = 0.007) and hamstring injuries (p = 0.041 and p = 0.017). Ligament/tendon IPP was greater in adult versus pre-PHV (p = 0.002). IPP for growth-related injuries was lower in post-PHV than pre-PHV (p = 0.039). Injury incidence rates (n = 166) exhibited similar patterns to IPP in the full cohort. Injury patterns were similar between post-PHV and adult academy players but, crucially, relatively more of these groups suffered injuries compared to pre- and circa-PHV (except growth-related injuries).



#7 A Video-Based Tactical Task Does Not Elicit Mental Fatigue and Does Not Impair Soccer Performance in a Subsequent Small-Sided Game

Reference: Sports (Basel). 2022 Feb 27;10(3):31. doi: 10.3390/sports10030031.

Authors: Gianmarco Ciocca, Antonio Tessitore, Mauro Mandorino, Harald Tschan

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Summary: Mental fatigue can impair physical, technical, and tactical performance in sports. Since most previous research used general cognitive tasks to elicit mental fatigue, the aim of this study was to investigate whether a more sport-specific task could induce the effects of mental fatigue and impair the subsequent physical and technical performance in a soccer small-sided game. Ten soccer players performed two small-sided games on two different days in a crossover design. Before each small-sided game, they performed a video-based tactical task (30 min) and a control task (documentary watching, 30 min) in a randomized and counterbalanced order. Mental effort was measured through a visual analog scale after the tactical and control tasks. Subjective ratings of perceived exertion were assessed through the RPE questionnaire after the end of the SSG. Physical performance was assessed during the SSG through GPS technology. Results showed no differences (p &gt; 0.05) in physical performance between the two conditions. None of the technical variables were negatively affected by the video-based tactical condition, with the number of total passes (p = 0.003; ES = 0.72 medium) and successful passes (p = 0.003; ES = 0.82 large) results even improved by the video-based tactical task. The mental effort required by the video-tactical task was significantly higher than the control task (p = 0.002; ES = 2.09 huge). However, overall RPE did not differ between conditions. The video-based tactical task did not elicit mental fatigue and did not impair subsequent physical and technical performance. The higher ecological validity of the task and the higher motivation of the participants might have contributed to the results.



#8 Association between Concentric and Eccentric Isokinetic Torque and Unilateral Countermovement Jump Variables in Professional Soccer Players

Reference: J Funct Morphol Kinesiol. 2022 Feb 25;7(1):25. doi: 10.3390/jfmk7010025.

Authors: Bruno Mazziotti Oliveira Alves, Robson Dias Scoz, Ricardo Lima Burigo, Isabella Christina Ferreira, Ana Paula Silveira Ramos, Jose Joao Baltazar Mendes, Luciano Maia Alves Ferreira, Cesar Ferreira Amorim

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Summary: Isokinetic tests have been highly valuable to athletic analysis, but their cost and technical operation turn them inaccessible. The purpose of this study was to verify the correlation between unilateral countermovement jump variables and isokinetic data. Thirty-two male professional soccer players were subjected to the isokinetic testing of both knee extensors and flexors in concentric and eccentric muscle contractions. They also executed unilateral countermovement vertical jumps (UCMJ) to compare maximum height, ground reaction force, and impulse power with isokinetic peak torque. Data analysis was conducted through Pearson correlation and linear regression. A high correlation was found between dominant unilateral extensor concentric peak torque and the UCMJ maximum height of the dominant leg. The non-dominant leg jump showed a moderate correlation. No other variable showed statistical significance. Linear regression allowed the generation of two formulae to estimate the peak torque from UCMJ for dominant and non-dominant legs. Although few studies were found to compare our results, leading to more studies being needed, a better understanding of the unilateral countermovement jump may be used in the future as a substitute to the expensive and technically demanding isokinetic testing when it is unavailable, allowing the assessment of lower limb physical asymmetries in athletic or rehabilitation environments.



#9 Exploring the Y-Balance-Test scores and inter-limb asymmetry in soccer players: differences between competitive level and field positions

Reference: BMC Sports Sci Med Rehabil. 2022 Mar 23;14(1):45. doi: 10.1186/s13102-022-00438-w.

Authors: Francisco Tomás González-Fernández, Luis Manuel Martínez-Aranda, Moisés Falces-Prieto, Hadi Nobari, Filipe Manuel Clemente

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Summary: The postural stability seems to be important in the physical development of the soccer player and the specific tasks related to the game. In addition, it is related to the injury risk and therefore, with the injury prevention and retraining processes. In this context, the Y Balance Test (YBT) is presented as a tool to assess dynamic postural control. This study aimed to explore the differences and possible correlations in the YBT scores and inter-limb asymmetry for anterior (ANT), posteromedial (PM) and posterolateral (PL) directions by category and field position in soccer players. 173 males soccer players aged between 14 and 33 years old agreed to participate. Five categories and six field position were considered in this study. A standardised protocol was used at multiple clubs during the pre-season assessment of musculoskeletal function in soccer players. All the players performed the Y Balance Test (YBT) (official YBT Kit), assessing the dominant and non-dominant leg for three YBT directions (anterior-AN, posteromedial-PM and posterolateral-PL), inter-limb asymmetry and composite score. For AN, amateur and semiprofessional obtained the highest values for Dominant and Non-Dominant legs (Rangemean = 101.8-109.4%) and the lowest level in PRO players (mean: 62.0%). Concerning PM-PL, semiprofessional (Rangemean = 126.4-132.7%, dominant and non-Dominant respectively), followed by professional and amateur reported higher scores compared to youth categories. Inter-limb asymmetry showed higher values in lower age categories. The best composite scores were detected in semiprofessionals (Rangemean = 113.3-126.7% for dominant and Rangemean = 113.8-129.7% for non-Dominant leg), compared with the rest of the categories and for each field position evaluated. Comparisons between field-positions revealed that centre-backs were worse than wingers and forwards. In order to explain variations in dynamic balance between competitive levels within the same age-group, special considerations about training programmes and related co-variables should be considered.



#10 Post-Match Recovery in Soccer with Far-Infrared Emitting Ceramic Material or Cold-Water Immersion

Reference: J Sports Sci Med. 2021 Oct 1;20(4):732-742. doi: 10.52082/jssm.2021.732. eCollection 2021 Dec.

Authors: Tiago M Coelho, Renan F H Nunes, Fabio Y Nakamura, Rob Duffield, Marília C Serpa, Juliano F da Silva, Lorival J Carminatt, Francisco J Cidral-Filho, Mariana P Goldim, Khiany Mathias, Fabricia Petronilho, Daniel F Martins, Luiz G A Guglielmo

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Summary: We investigated the effects of two common recovery methods; far-infrared emitting ceramic materials (Bioceramic) or cold-water immersion on muscular function and damage after a soccer match. Twenty-five university-level soccer players were randomized into Bioceramic (BIO; n = 8), Cold-water immersion (CWI; n = 9), or Control (CON; n = 8) groups. Heart rate [HR], rating of perceived exertion [RPE], and activity profile through Global Positioning Satellite Systems were measured during the match. Biochemical (thiobarbituric acid reactive species [TBARS], superoxide dismutase [SOD], creatine kinase [CK], lactate dehydrogenase [LDH]), neuromuscular (countermovement [CMJ] and squat jump [SJ], sprints [20-m]), and perceptual markers (delayed-onset muscle soreness [DOMS], and the perceived recovery scale [PRS]) were assessed at pre, post, 24 h, and 48 h post-match. One-way ANOVA was used to compare anthropometric and match performance data. A two-way ANOVA with post-hoc tests compared the timeline of recovery measures. No significant differences existed between groups for anthropometric or match load measures (P > 0.05). Significant post-match increases were observed in SOD, and decreases in TBARS in all groups (p < 0.05), without differences between conditions (p > 0.05). Significant increases in CK, LDH, quadriceps and hamstring DOMS (p < 0.05), as well as decreases in 20-m, SJ, CMJ, and PRS were observed post-match in all groups (p < 0.05), without significant differences between conditions (p > 0.05). Despite the expected post-match muscle damage and impaired performance, neither Bioceramic nor CWI interventions improved post-match recovery.



#11 The Impact of Moderate and High Intensity Cardiovascular Exertion on Sub-Elite Soccer Referee's Cognitive Performance: A Lab-Based Study

Reference: J Sports Sci Med. 2021 Oct 1;20(4):618-625. doi: 10.52082/jssm.2021.618. eCollection 2021 Dec.

Authors: Isabelle Senécal, Samuel J Howarth, Greg D Wells, Isaac Raymond, Silvano Mior

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Summary: Soccer referees represent a specialized population who are required to perform decisional or perceptual tasks during physical exertion. Recent studies have demonstrated that submaximal acute exercise has a positive impact on cognitive performance. However, less is known about the impact of more strenuous exertion on cognitive performance. This study assessed the effect of moderate and maximal intensity exercise exertion on a cognitive performance in sub-elite soccer referees. Twelve experienced soccer referees (4 female, 8 male) were recruited. Data were collected on 2 separate days. Baseline fitness level was assessed by a standardized aerobic capacity test (VO2max Test) on Day 1, along with practice trials of the Stroop Color Word Test (Stroop Test) for evaluating cognitive performance. On Day 2, cognitive performance was assessed before, during, and after an incremental intensity exercise protocol based on the Fédération International de Football Association (FIFA) referee fitness test. Relative to results obtained at rest performance on the Stroop Test improved at moderate exertion and at maximal exertion during the modified FIFA fitness test (F = 18.97, p = .005). Mean time to completion (in seconds) of the interference Stroop task significantly improved (p < .05) between rest and moderate exertion [-3.0 ± 3.0 seconds] and between rest and maximal exertion [-4.8 ± 2.6 seconds]. In summary, we observed that cognitive performance was found to improve when sub-elite soccer referees performed moderate and maximal exercise relative to results obtained at rest. It is possible that referees focus their attention to improve goal-oriented processing in the brain during physical exertion.



#12 Gastrointestinal Hormones, Morphological Characteristics, and Physical Performance in Elite Soccer Players

Reference: Int J Sports Physiol Perform. 2022 Mar 23;1-11. doi: 10.1123/ijspp.2021-0484. Online ahead of print.

Authors: Iyed Salhi, Abderraouf Ben Aabderrahman, Raoua Triki, Cain C T Clark, Sabri Gaed, Anthony C Hackney, Ayoub Saeidi, Ismail Laher, Jennifer A Kurtz, Trisha A VanDusseldorp, Hassane Zouhal

Summary: The purpose was to determine the relationship between gastrointestinal hormones (leptin, glucagon-like peptide-1), ghrelin, cholecystokinin, peptide YY, morphological characteristics, and physical performances in elite soccer players. Q2 Twenty-two elite male soccer players (age = 23.1 [2.7] y, height = 177.0 [0.1] cm, weight = 70.2 [2.9] kg, body mass index = 22.1 [1.8] kg/m2) completed 3-day food records each week during the 5-week training period. Blood samples were drawn after an overnight fast before and after preseason training to assess gastrointestinal hormones (leptin, glucagon-like peptide-1, ghrelin, cholecystokinin, and peptide YY). Continuous analysis of the training load was used during the training period. Preintervention and postintervention tests assessed jumping (countermovement jump), sprinting (10, 20, and 30 m), and endurance fitness (the Yo-Yo Intermittent Recovery Test Level 1 [YYIRT1]) levels. Preseason training decreased body mass index (P = .001; effect size [ES] = 0.183) and body fat percentage (P = .001; ES = 0.516). There were increases in countermovement jump (P = .032; ES = 0.215), 20- (P = .016; ES = 0.195) and 30-m sprints (P = .001; ES = 0.188), and YYIRT1 performance (P = .001; ES = 0.9). Levels of cholecystokinin, peptide YY, and ghrelin did not change during preseason training, although changes in leptin (P = .001; ES = 0.41) and glucagon-like peptide-1 levels (P = .039; ES = 0.606) were recorded. Leptinemia correlated with anthropometric parameters (body mass index, r = .77, P = .001; percentage of body fat,r = .67, P = .006) and the total distance covered during the YYIRT1 (r = -.54; P = .03). Changes in morphological parameters and physical performance in elite-level male soccer players are related to variations in selected gastrointestinal hormones.



#13 The Practical Utility of Objective Training Load Indices in Division I College Soccer Players

Reference: J Strength Cond Res. 2022 Apr 1;36(4):1026-1030. doi: 10.1519/JSC.0000000000004227.

Authors: Troy A Coppus, Travis Anderson, Eoin Hurley, Diane L Gill, Pamela K Brown

Summary: The aim of this study was to investigate the association of subjective session rating of perceived exertion with objective training load measures and explored data reduction approaches for 26 commonly measured objective load metrics. One National Collegiate Athletic Association Division I male soccer team (N = 28) provided 26 objective measures via a global positioning system and heart rate monitor system and self-report rating of perceived exertion measures for all team activities through the 12-week 2019 fall championship season. The singular associations between session rating of perceived exertion (sRPE) and objective load metrics were assessed via repeated-measures correlation and collectively assessed via elastic net regression. Principal components analysis was then used to reduce the dimensionality of objective load variables. Level of significance for the study was α ≤ 0.05. The training load variable had the highest correlation with sRPE (r = 0.85) among the 26 metrics. Twenty variables were retained in the elastic-net regression and demonstrated an R2 of 0.76. The principal components analysis demonstrated a 4-component solution. The components were qualitatively described as "moderate- or high-intensity external load," "low-intensity load," "high-intensity internal load," and "average internal load" and accounted for 46, 32, 16, and 6% of the variance, respectively. The sRPE metric had strong correlations with multiple objective measures, demonstrating its utility for practitioners monitoring training load in collegiate soccer with limited resources. Furthermore, the consolidation of 26 metrics into 4 components while retaining data variability allows coaches to focus on a small number of metrics and employ a data-driven approach to training.



#14 Inter- and intra-microcycle external load analysis in female professional soccer players: A playing position approach

Reference: PLoS One. 2022 Mar 22;17(3):e0264908. doi: 10.1371/journal.pone.0264908. eCollection 2022.

Authors: Elba Diaz-Seradilla, Alejandro Rodríguez-Fernández, José Antonio Rodríguez-Marroyo, Daniel Castillo, Javier Raya-González, José Gerardo Villa Vicente

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Summary: This study analyzes the inter- and intra-differences in external load across the microcycle in professional female soccer players. External load during four consecutive microcycles (i.e., M1, M2, M3, and M4) and training sessions (i.e., MD-4, MD-3, MD-2, and MD-1) and a match day (i.e., MD) were registered in seventeen female professional soccer players (age: 26.3 ± 4.6 years; height: 166.3 ± 6.1 cm; body mass: 59.8 ± 6.8 kg; and body mass index: 21.6 ± 1.7 kg·m-2) who belonged to the same team in Spanish first division. A 10-Hz GPS that integrated a 100-Hz triaxial accelerometer was used to register external load. The results showed lower decelerations in M2 compared to M1 and M3 (p < 0.05), lower high-intensity distance (>16.0 km·h-1) in M3 vs. M2, and greater relative sprint distance (>21.0 km·min-1) in M4 vs. M1 and M3 (p < 0.05). MD-3 registered the highest load for all variables (p < 0.05). Forwards (FWs) performed (p < 0.05) significantly more sprints (meters and number > 21.0 km·h-1) than central midfielders (CMs) and central defenders (CDs) in MD-2 and MD. Both, fitness and conditioning staff should pay special attention to the external loads for each playing position in training sessions to optimize the training process.



#15 A standardized method for quantifying and characterizing repetitive head impacts in soccer matches using video footage

Reference: Sci Med Footb. 2022 Mar 19. doi: 10.1080/24733938.2022.2056233. Online ahead of print.

Authors: Tara Porfido, Jaclyn Caccese, Jessica Gutt, Conor Wentworth, Kerry Peek, Abigail C Bretzin, Carrie Esopenko

Summary: Soccer athletes experience repetitive head impacts (RHI) through purposeful heading and unintentional head impacts, which may be associated with acute and chronic brain injury. Previous soccer studies have sought to quantify and characterize RHI, but to-date no consistent, standardized methods exist. The Heads-Up Checklist (HUC), originally used for characterizing head impacts in hockey, was modified to be used in soccer (soccer HUC [SHUC]). Our aim was to determine the reliability of quantifying ball-to-head impacts using video verification and to develop and test the reliability of the SHUC to characterize RHI in soccer. Two trained reviewers used the SHUC to quantify ball-to-head impacts and characterize non-ball-to-head impacts in 38 male and female collegiate soccer matches. Intraclass correlation coefficient (ICC) and Cohen's Kappa were used to assess interrater reliability. Independent t-tests and Chi-square analyses were used to examine sex differences. The interrater reliability for quantifying ball-to-head impacts was excellent (ICC=0.97); however, only half of the non-ball-to-head impact characteristics had acceptable interrater reliability with two reviewers. Number of ball-to-head-impacts and RHI characteristics were consistent between males and females (p>0.05). Our results suggest that the SHUC is an applicable standardized method to quantify and characterize RHI from video footage of soccer matches; however, accurately characterizing some aspects of RHI is a challenging task that may be supplemented by head impact sensor data.



#16 Predicting ratings of perceived exertion in youth soccer using decision tree models

Reference: Biol Sport. 2022 Mar;39(2):245-252. doi: 10.5114/biolsport.2022.103723. Epub 2021 Apr 9.

Authors: Jakub Marynowicz, Mateusz Lango, Damian Horna, Karol Kikut, Marcin Andrzejewski

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Summary: The purpose of this study was to determine the effectiveness of white-box decision tree models (DTM) for predicting the rating of perceived exertion (RPE). The second aim was to examine the relationship between RPE and external measures of intensity in youth soccer training at the group and individual level. Training load data from 18 youth soccer players were collected during an in-season competition period. A total of 804 training observations were undertaken, with a total of 43 ± 17 sessions per player (range 12-76). External measures of intensity were determined using a 10 Hz GPS and included total distance (TD, m/min), high-speed running distance (HSR, m/min), PlayerLoad (PL, n/min), impacts (n/min), distance in acceleration/deceleration (TD ACC/TD DEC, m/min) and the number of accelerations/decelerations (ACC/DEC, n/min). Data were analysed with decision tree models. Global and individualized models were constructed. Aggregated importance revealed HSR as the strongest predictor of RPE with relative importance of 0.61. HSR was the most important factor in predicting RPE for half of the players. The prediction error (root mean square error [RMSE] 0.755 ± 0.014) for the individualized models was lower compared to the population model (RMSE 1.621 ± 0.001). The findings demonstrate that individual models should be used for the assessment of players' response to external load. Furthermore, the study demonstrates that DTM provide straightforward interpretation, with the possibility of visualization. This method can be used to prescribe daily training loads on the basis of predicted, desired player responses (exertion).



#17 Reliability and validity of a modified Illinois change-of-direction test with ball dribbling speed in young soccer players

Reference: Biol Sport. 2022 Mar;39(2):295-306. doi: 10.5114/biolsport.2022.104917. Epub 2021 Apr 9.

Authors: Issam Makhlouf, Amel Tayech, Mohamed Arbi Mejri, Monoem Haddad, David G Behm, Urs Granacher, Anis Chaouachi

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Summary: The purpose of this study was to assess test-retest reliability, discriminative and criterion-related validity of the modified Illinois change-of-direction (CoD) test with ball dribbling-speed (ICODT-BALL) in young soccer players of different biological maturity and playing levels. Sixty-five young male soccer players (11.4 ± 1.2 years) participated in this study. The participants were classified according to their biological maturity (pre- and circumpeak height velocity [PHV]) and playing-level (elite and amateur players). During the test-retest time period of two weeks, the following tests were performed during week one and as retest during week two: ICODT-BALL, ICODT, 4 × 9-m shuttle-run, countermovement-jump, triple-hop-test, maximum-voluntary isometric-contraction of back-extensors, Stork, Y-Balance, 10 and 30-m sprints. The ICODT-BALL showed excellent relative (r = 0.995, p < 0.001; ICC = 0.993) and absolute (SEM < 5%; SEM < SWCs(0.2, 0.6, 1.2)) reliability. The circum-PHV (22.8 ± 1.7-s) and elite (22.5 ± 0.9-s) players showed better ICODT-BALL performance than their pre-PHV (24.2 ± 2.5-s) and amateur (25.1 ± 2.8-s) counterparts (p = 0.028 and p < 0.001, respectively). The ICODT-BALL showed "very good" (AUC = 0.81) discriminant validity when comparing the elite and amateur players, and "moderate" (AUC = 0.67) discriminant validity when compared to pre-PHV and circum-PHV boys. ICODT-BALL demonstrated "large" positive associations with the ICODT (r = 0.65; 41.8% shared-variance) and sprint tests (r ≥ 0.52; 27.3 to 34.8% shared-variance). In addition, results showed "moderate" negative associations between ICODT-BALL and strength, and power measures, as well as a "small" negative relationship with balance tests. In conclusion, the ICODT-BALL is a valid and reliable test to evaluate the ability to quickly change directions while ball dribbling in young soccer players. Therefore, practitioners can use the ICODT-BALL as a tool for talent identification.



#18 Effect of training day, match, and length of the microcycle on workload periodization in professional soccer players: a full-season study

Reference: Biol Sport. 2022 Mar;39(2):397-406. doi: 10.5114/biolsport.2022.106148. Epub 2021 Jun 1.

Authors: José M Oliva-Lozano, Carlos D Gómez-Carmona, Víctor Fortes, José Pino-Ortega

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Summary: The aims of this study were to: (a) describe and compare the volume and intensity from the workload of professional soccer players between training and MD, and (b) analyse the effect that the length of the microcycle had on the workload. A cohort study was designed for a full season in La Liga 123. Wearable tracking systems collected the distance covered in meters (m), total number of high-intensity accelerations (ACCHIGH) and decelerations (DECHIGH), total number of high-speed running actions (HSRA), high-speed running distance (HSRD), high metabolic load distance (HMLD), and player load (PL) from training days (MD+1, MD-4, MD-3, MD-2, and MD-1) and MD. Significant differences were found between training and MD workload, MD workload being the most demanding for all intensity and volume variables (F = 36.35-753.94; p < 0.01; wp 2 = 0.21-0.85). The greatest training intensity and volume were found on MD-4 and MD-3 (p < 0.05). In addition, a novel finding was that the length of the microcycle had a significant effect on the workload both in volume and intensity (F = 4.84-14.19; p < 0.01; wp 2 = 0.03-0.09), except for relative ACCHIGH, DECHIGH, and HMLD. Although MD-4 and MD-3 were the most suitable days for loading the players, the results showed that MD elicited a unique stimulus in terms of volume and intensity. Consequently, coaches need to include specific training drills to adapt the players for the competitive demands. Finally, special focus should be placed on MD from short and regular microcycles (5-day, 6-day, or 7-day microcycles) since declines in physical performance were observed in comparison with long microcycles (8-day or 9-day microcycles).



#19 Speed and power-related gene polymorphisms associated with playing position in elite soccer players

Reference: Biol Sport. 2022 Mar;39(2):355-366. doi: 10.5114/biolsport.2022.105333. Epub 2021 Apr 21.

Authors: Miroslav Petr, Dan Thiel, Kvapilová Kateřina, Petr Brož, Tomáš Malý, František Zahálka, Pavlína Vostatková, Michal Wilk, Jakub Chycki, Petr Stastny

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Summary: Heritability studies on sport-related traits accepted that endurance, speed, power, and strength abilities include an active genetic predisposition to elite soccer participation. This study evaluates the influence of selected genetic variants on performance in speed, power, and strength laboratory tests on a group of elite soccer players, including their playing position. A ninety-nine male elite soccer players were compared to controls (n = 107) and tested for quadriceps and hamstrings isokinetic strength at speed 60°/s, 180°/s, and 300°/s, jump performance, and genotypes of ACTN3 (R577X, rs1815739), ACE (I/D, rs1799752), NOS3 (Glu298Asp, rs1799983), AMPD1 (34C/T, rs17602729), UCP2 (Ala55Val, rs660339), BDKRB2 (+9/-9, rs5810761) and IL1RN (VNTR 86-bp). The ACTN3 XX homozygotes in defenders had lower quadriceps and hamstring isokinetic strength in all tested speeds than ACTN3 RX and RR genotypes (p < 0.05). The ACTN3 RR homozygotes in defenders had higher quadriceps strength in all tested velocities than the RX heterozygotes (p < 0.05). We also found other associations between playing-position in soccer and increased strength of lower limbs for AMPD1 CC and NOS3 Glu/Glu genotypes, and IL1RN*2 allele carriers. Total genetic score regression explained 26% of the variance in jump performance and isokinetic strength. The ACTN3 R allele, NOS3 Glu/Glu genotypes, and IL1RN*2 allele pre-disposed the attackers and defenders playing position in elite soccer, where those positions have higher strength and power measures than midfielders. Midfielders have lower strength and power conditions than other playing positions without relation to strength and power genes.



#20 Training, psychometric status, biological markers and neuromuscular fatigue in soccer

Reference: Biol Sport. 2022 Mar;39(2):319-327. doi: 10.5114/biolsport.2022.104065. Epub 2021 Apr 9.

Authors: Okba Selmi, Ibrahim Ouergui, Danielle E Levitt, Hamza Marzouki, Beat Knechtle, Pantelis T Nikolaidis, Anissa Bouassida

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Summary: The study examined the relationship between psychometric status, neuromuscular, and biochemical markers of fatigue in response to an intensified training (IT) period in soccer. Fifteen professional soccer players volunteered to participate in the study (mean ± SD: age: 25 ± 1 years; body height: 179 ± 7 cm, body mass: 73.7 ± 16.2 kg, experience: 13.2 ± 3 years). Training load, monotony, strain, Hooper index and total quality recovery (TQR) were determined for each training session during a 2-week of IT. Counter-movement jump (CMJ) and biochemical responses [testosterone, cortisol, testosterone-to-cortisol ratio (T/C ratio), creatine kinase, and C-reactive protein] were collected before and after IT. Results showed that IT induced significant increases in cortisol, creatine kinase and C-reactive protein and significant decreases in T/C ratio and CMJ performance from before to after IT (p < 0.01, p < 0.001, p < 0.001, p < 0.01, p < 0.05, respectively). However, testosterone did not differ from before to after IT (p > 0.05). Training loads were positively correlated with Hooper index (p < 0.05) and negatively correlated with total quality recovery (p < 0.05). Hooper index was positively correlated with cortisol (p < 0.05), T/C ratio (p < 0.01), and creatine kinase (p < 0.01), and negatively correlated with CMJ (p < 0.05). Furthermore, TQR was negatively correlated with T/C ratio (p < 0.01), creatine kinase (p < 0.001), and C-reactive protein (p < 0.05), and positively correlated with CMJ (p < 0.01). Neuromuscular fatigue, muscle damage, and change in the anabolic/catabolic state induced by the IT were related to well-being and perceived recovery state among professional soccer players.



#21 Resisted sprint training with partner towing improves explosive force and sprint performance in young soccer players - a pilot study

Reference: Biol Sport. 2022 Mar;39(2):379-387. doi: 10.5114/biolsport.2022.103574. Epub 2021 Apr 21.

Authors: Anis Chaalali, Khalil Bouriel, Mehdi Rouissi, Moktar Chtara, Bessem Mkaouer, John Cronin, Anis Chaouachi, Karim Chamari

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Summary: The purpose of this study was to examine the effects of non-resisted (NRS) and partner-towing resisted (RS) sprint training on legs explosive force, sprint performance and sprint kinematic parameters. Sixteen young elite soccer players (age 16.6 ± 0.2 years, height 175.6 ± 5.7 cm, and body mass 67.6 ± 8.2 kg) were randomly allocated to two training groups: resisted sprint RS (n = 7) and non-resisted sprint NRS (n = 9). The RS group followed a six-week sprint training programme consisting of two "sprint training sessions" per week in addition to their usual soccer training. The NRS group followed a similar sprint training programme, replicating the distances of sprints but without any added resistance. All players were assessed before and after training: vertical and horizontal jumping (countermovement jump (CMJ), squat jump (SJ), and 5-jump test (5JT)), 30 m sprint performance (5, 10, and 20 m split times), and running kinematics (stride length and frequency). In the RS group significant (p < 0.05) changes were: decreased sprint time for 0-5 m, 0-10 m and 0-30 m (-6.31, -5.73 and -2.00%; effect size (ES) = 0.70, 1.00 and 0.41, respectively); higher peak jumping height (4.23% and 3.59%; ES = 0.35 and 0.37, for SJ and CMJ respectively); and 5JT (3.10%; ES = 0.44); and increased stride frequency (3.96%; ES = 0.76). In the NRS group, significant (p < 0.05) changes were: decreased sprint time at 0-30 m (-1.34%, ES = 0.33) and increased stride length (1.21%; ES = 0.17). RS training (partner towing) for six weeks in young soccer players showed more effective performances in sprint, stride frequency and lower-limb explosive force, while NRS training improved sprint performance at 0-30 m and stride length. Consequently, coaches and physical trainers should consider including RS training as part of their sprint training to ensure optimal sprint performance.



#22 Biological maturation influences selection process in youth elite soccer players

Reference: Biol Sport. 2022 Mar;39(2):435-441. doi: 10.5114/biolsport.2022.106152. Epub 2021 Jun 1.

Authors: Marcelo Massa, Alexandre Moreira, Renato A Costa, Marcelo R Lima, Carlos R Thiengo, Walter Q Marquez, Aaron J Coutts, Marcelo S Aoki

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Summary: This study examined the influence of birth date, salivary testosterone [sT] concentration, sexual maturity status, and general strength on the selection process of an elite Brazilian soccer club during a 12-month period, which was a 2nd phase of a 24-month selection process. The stature, body mass, sT, sexual maturity status [Tanner scale], and hand grip strength were assessed for 143 players during 2 weeks. From these 143 players, 100 players were dismissed [DIS] and 43 players were selected to integrate the club's under-14 squad. Following 1-year training period, the under-14 team was assembled with 9 players designated as starters [STA], and then, comparisons were conducted taking into account a group of non-starters (selected; SEL = 34 players) and STA (n = 09). The DIS, SEL, STA players, and reference population, were compared for birth distribution. A greater proportion of players was born in the first trimester in the STA [75.0%], SEL [57.1%] and DIS [50.0%] groups compared to the reference population [25.8%]. One-way ANOVA showed a higher sT for STA group [516.0 ± 129.9 pmol·L-1], compared to SEL [415.5 ± 117.9 pmol·L-1] and DIS groups [390.9 ± 84.9 pmol·L-1; p = 0.003), and Kruskall-Wallis test showed a higher gonadal development for STA compared to DIS [p = 0.001]. The current findings suggest a strong influence of birth date and biological maturation on young soccer players selection process. Soccer coaches should consider these influences when making decisions about player selection of elite youth players.



#23 Effects of melatonin ingestion on physical performance and biochemical responses following exhaustive running exercise in soccer players

Reference: Biol Sport. 2022 Mar;39(2):473-479. doi: 10.5114/biolsport.2022.106385. Epub 2021 Jul 2.

Authors: Mohamed Amine Farjallah, Ahmed Graja, Lobna Ben Mahmoud, Kais Ghattassi, Mariem Boudaya, Tarak Driss, Kamel Jamoussi, Zouheir Sahnoun, Nizar Souissi, Omar Hammouda

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Summary: Antioxidant supplementation has become a common practice among athletes to boost sport achievement. Likewise, melatonin (MEL) has been ingested as an ergogenic aid to improve physical performance. To date, no study has checked whether the multiple beneficial effects of MEL have an outcome during a maximum running exercise until exhaustion. Therefore, the present study aimed to evaluate the effect of MEL ingestion on physical performance and biochemical responses (i.e., oxidative stress) during exhaustive exercise. In a double blind randomized study, thirteen professional soccer players [age: 17.5 ± 0.8 years, body mass: 70.3 ± 3.9 kg, body height: 1.80 ± 0.08 m; maximal aerobic speed (MAS): 16.85 ± 0.63 km/h; mean ± standard deviation], members of a first league squad, performed a running exercise until exhaustion at 100% of MAS, after either MEL or placebo ingestion. Physical performance was assessed, and blood samples were obtained at rest and following the exercise. Compared to placebo, MEL intake prevented the increase in oxidative stress markers (i.e., malondialdehyde), alleviated the alteration of antioxidant status (i.e., glutathione peroxidase, uric acid and total bilirubin) and decreased post-exercise biomarkers of muscle damage (i.e., creatine kinase and lactate dehydrogenase) (p < 0.05). However, physical performance was not affected by MEL ingestion (p > 0.05). In conclusion, acute MEL intake before a maximal running exercise protected athletes from oxidative stress and cellular damage but without an effect on physical performance.







The diagonal positioning of the goals modifies the external training load and the tactical behaviour of young football players

The aim of this study was to identify how positioning the goals in diagonal configurations on the pitch modifies the external training load and the tactical behaviour of young football players during small-sided games (SSG).





Effects of Whole-Season Training and Match-Play on Hip Adductor and Abductor Muscle Strength in Soccer Players: A Pilot Study

No investigation has examined the influence of soccer training and match-play during the season on isometric hip adductor and abductor muscle strength. The authors hypothesised that maximal hip adductor and abductor muscle strength would increase after the preseason, maintain relatively constant levels across the season.





Latest research in football - week 11 - 2022

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 Center backs work hardest when playing in a back three: The influence of tactical formation on physical and technical match performance in professional soccer

Reference: PLoS One. 2022 Mar 17;17(3):e0265501. doi: 10.1371/journal.pone.0265501. eCollection 2022.

Authors: Leon Forcher, Leander Forcher, Darko Jekauc, Alexander Woll, Timo Gross, Stefan Altmann

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Summary: The purpose of this study was to investigate whether tactical formation affects the physical and technical match performance of professional soccer players in the first German Bundesliga. From official match data of the Bundesliga season 2018/19, physical (total distance, high-intensity distance, sprinting distance, accelerations, maximum velocity) and technical performance (short/middle/long passes, dribblings, ball-possessions) of players were analyzed. Players were categorized into five playing positions (center back, full back, central midfielder, wide midfielder, forward) and teams into eight different tactical formations (4-4-2, 4-4-2 diamond, 4-2-2-2, 4-3-3, 4-5-1, 4-2-3-1, 3-4-3, 3-5-2). Results revealed that the degree to which tactical formation affects match performance is position dependent. In terms of physical performance, center backs and full backs showed highest sprinting distances when playing in a formation with only three defenders in the back row (3-4-3, 3-5-2) compared to all other formations (ES range: 0.13≤ES≤1.27). Regarding technical performance, all positions except forwards displayed fewer short passes, middle passes and ball-possessions in the formations 4-3-3 and 4-2-3-1 compared to all other formations (0.02≤ES≤1.19). In conclusion, physical and technical performance of center backs, full backs and wide midfielders differed markedly between the tactical formations. Conversely, the physical and technical performance of central midfielders and forwards only showed small differences between the different tactical formations. These findings can help coaches scheduling their practice. For example, if a coach wants to change the playing formation, he can anticipate the physical and technical match performance changes depending on the respective playing position.



#2 The Effect of Intensity Soccer Training Sessions on Marked Biochemical Indicators of Blood Acidity of Saudi Young Soccer Players

Reference: Open Access J Sports Med. 2022 Mar 10;13:17-23. doi: 10.2147/OAJSM.S356075. eCollection 2022.

Authors: Ghareeb O Alshuwaier, Hadeel Ali Ghazzawi, Abdulrahman I Alaqil, Yahya R Alsharif, Mohammed Shaab Alibrahim, Khalid S Aljaloud

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Summary: The purpose was to assess the effect of low-to-moderate-intensity exercise on specific blood biomarkers and blood acidity in young Saudi Arabian professional soccer players. A total of 43 professional soccer players participated in the current study. A cross-sectional research method was used to compare the changes in the following blood biomarkers: calcium, magnesium, glucose, anion-gap metabolic acidosis, and carbon dioxide, after a range of low-to-moderate intensity training sessions. Measurements were taken in two soccer training sessions (Day 1, and Day 2). The exercise intensity was estimated by heart rate percentage of maximal heart rate. Wilcoxon signed-rank testing was used to analyze the results. Significant differences were found between and pre-and post-training sessions for anion-gap metabolic acidosis: Day 1: 12.55 vs 15.4 mmol/L; Day 2: 14.15 vs 16.35 mmol/L; and magnesium: Day 1: 0.82 vs 0.74 mmol/L; Day 2: 0.85 vs 0.74 mmol/L. Exercise caused anion-gap metabolic acidosis concentrations to rise post-training; magnesium levels decreased after training sessions on Day 1 and Day 2. The concentrations of anion-gap metabolic acidosis and magnesium were significantly affected by exercise intensity in the subjects, the former rose post-training while the latter fell. More studies are required to investigate the effects of different exercise intensities on other blood biomarkers in soccer players.



#3 The incidence and burden of injuries in elite English youth female soccer players

Reference: Sci Med Footb. 2022 Mar 17. doi: 10.1080/24733938.2022.2051730. Online ahead of print.

Authors: Jake Beech, Ben Jones, Ryan King, Pippa Bennett, Stephanie Young, Sean Williams, Keith Stokes, Stacey Emmonds

Summary: This study aimed to investigate the incidence, severity, and burden of injury in English elite youth female soccer players. Qualified therapists at six English girls' academies prospectively recorded all injuries that required medical attention or caused time loss for matches and training in 375 elite youth female soccer players (under-10 , U12, U14 and U16) during the 2019/2020 season. One hundred- and eleven time-loss injuries (52 from training, 59 from matches) were sustained, resulting in 1,946 days absent (779 days from training injuries, 1,167 days from match injuries) from soccer activities. The injury incidence for matches (9.3/1000 hours, 95% CIs: 7.2-11.9) was significantly greater than training (1.1/1000 hours, 95% CIs: 0.9-1.5, p<0.001). Additionally, the injury burden for matches (183 days lost/1000 hours, 95% CIs: 142-237) was significantly greater than training (17 days lost/1000 hours, 95% CIs: 13-22, p<0.001). Injury incidence and burden were greatest in the U16 age group, and were found to increase with age. Whilst injury incidence and burden are greater in matches than training, a large proportion of preventable injuries, soft-tissue and non-contact in nature, were sustained in training. Findings provide comparative data for elite youth female soccer players.



#4 Exploring interactions between maturity status and playing time with fluctuations in physical fitness and hormonal markers in youth soccer players

Reference: Sci Rep. 2022 Mar 16;12(1):4463. doi: 10.1038/s41598-022-08567-5.

Authors: Ebrahim Eskandarifard, Hadi Nobari, Mustafa Sogut, Filipe Manuel Clemente, António José Figueiredo

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Summary: The purpose of this study was to determine the differences in functional capacities and hormonal indices according to biological maturity and seasonal playing time status in young soccer players. Twenty-three male under-15 players (14.6 ± 0.2 years) were divided into two groups, based on their maturity status and seasonal playing time. They were measured for anthropometrics, Yo-Yo intermittent recovery level 1 (YYIR1), seven repeated sprint test (7RST), countermovement jump (CMJ), skeletal age, growth hormone, and insulin-like growth factor-1 (IGF-1) level. Age at peak height velocity (APHV) was determined to estimate the maturity timing. The results revealed that players who advanced in maturation were significantly heavier (p = 0.029) and had higher values in skeletal age (p < 0.001), sitting height (p = 0.005), CMJ (p = 0.038), and IGF-1 (p = 0.013). Players given greater playing time exhibited significantly lower fatigue index (p = 0.012), but higher CMJ (p = 0.003) and IGF-1 (p = 0.001) values. The overall results highlighted that early-maturing players and players with greater playing time obtained higher values in both CMJ and IGF-1. The findings may provide an insight on the coaches' evaluation of players and on the possible factors that may affect the future playing status of young male soccer players.



#5 Did the Absence of Crowd Support During the Covid-19 Pandemic Affect the Home Advantage in Brazilian Elite Soccer?

Reference: J Hum Kinet. 2022 Feb 10;81:251-258. doi: 10.2478/hukin-2022-0047. eCollection 2022 Jan.

Authors: Lucas de Castro Ribeiro, Fabiano de Souza Fonseca, Gustavo De Conti Teixeira Costa, Henrique de Oliveira Castro, João Paulo Victor da Silva Santos, Lucas Savassi Figueiredo

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Summary: This study aimed to investigate the impact of crowd absence due to the COVID-19 pandemic on home advantage in Series A and B of professional Brazilian male soccer. Moreover, we sought to compare the home advantage between different competitive levels. Data from 2018 to 2020 Brazilian professional soccer championships (Series A and B) were analyzed, consisting of 2280 matches. The effect of home advantage was calculated in relation to the number of points won, the number of wins, goals scored and goals conceded. Our results indicated that home advantage was reduced in Serie A. Specifically, the 2020 (absence of the crowd) and 2019 seasons showed smaller home advantage compared to the 2018 season. On the other hand, Serie B analyses indicated no changes in home advantage over the seasons analyzed. The comparison of home advantage between competitive levels indicated higher home advantage in Serie A, exclusively in the 2018 season. In addition to the absence of fans, other changes occurred in elite sports due to the pandemic, such as changes in rules and the calendar. Considering that home advantage is affected by multiple interacting factors, it is important to investigate specific sports leagues across the world to determine which factors had the greatest impact on the advantage of playing home matches.



#6 Variations in Internal and External Training Load Measures and Neuromuscular Performance of Professional Soccer Players During a Preseason Training Period

Reference: J Hum Kinet. 2022 Feb 10;81:149-162. doi: 10.2478/hukin-2022-0012. eCollection 2022 Jan.

Authors: Lucas A Pereira, Tomás T Freitas, Vinicius Zanetti, Irineu Loturco

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Summary: We described the internal and external training loads (TLs) experienced by soccer players over a 4-week preseason, examined their effects on vertical jump (VJ) performance, and investigated the relationships between different TL variables. Eighteen professional soccer players performed 17 training sessions and 1 friendly-match (FM) over the preseason. The internal TL was obtained using the session-rating of perceived exertion method. The external TL variables collected were total and high-intensity distances, body-load, and high-metabolic power distance via the GPS system. VJ performance was assessed 13 times throughout the study. Moreover, total quality recovery and delayed onset muscle soreness were assessed before every training session as a measure of recovery status. Players were divided, using a median split analysis, into two groups, according to their VJ performance (i.e., "lower" and "higher" VJ). External TL variables displayed similar variations across training sessions and were significantly interrelated (r ranging from 0.48 to 0.88). In periods where higher internal TLs were detected, impaired recovery status was noticed. Notably, the higher VJ group exhibited decreased jump performance at post-test and higher internal and external TLs across the entire preseason (compared to the lower VJ group). From our results it is suggested that professional soccer players with higher VJ performance are potentially more susceptible to concurrent training effects.



#7 Ultrasound Shear Modulus and Thickness of Lateral Abdominal Muscles in Different Contractile States in Relation To Self- Reported Hip/Groin Problems in Youth Soccer Players

Reference: J Hum Kinet. 2022 Feb 10;81:97-108. doi: 10.2478/hukin-2022-0009. eCollection 2022 Jan.

Authors: Pawel Linek, Nadine Booysen, Maria Stokes

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Summary: To date, no studies have assessed lateral abdominal muscles' (LAM) elasticity and thickness in relation to hip and groin symptoms in any population. The objectives were to a) assess the relationship between LAM ultrasound measurements (elasticity and thickness) and self-reported subscales of the Copenhagen Hip and Groin Outcome Score (HAGOS) and b) compare LAM elasticity and thickness between asymptomatic and symptomatic sides. Shear modulus and thickness of the oblique external (OE), internal (OI) and transversus abdominis (TrA) muscles in 25 young soccer players were assessed at rest and during isometric contraction using ultrasound shear wave elastography. HAGOS subscales were used to assess self-reported hip/groin problems. There was a significant (p < 0.05) moderate correlation between allometric-scaled OI resting thickness (mean of right and left) and the Activities of Daily Living (r = 0.40), Sport (r = 0.57) and Quality of Life (QOL) (r = 0.41) HAGOS subscales. Also, a moderate significant correlation was found between allometric-scaled TrA resting thickness and the QOL subscale (r = 0.47). Moderate correlations were found between resting OI shear modulus and the QOL (r = 0.44), between right TrA shear modulus during contraction and Symptoms (r = 0.57), and between the left TrA shear modulus during contraction and Physical Activity (r = 0.41) subscales. No differences were found between the symptomatic and asymptomatic side in thickness and elasticity measurements among soccer players with unilateral symptoms (p > 0.05). The relationships found between LAM and hip/groin problems in youth male soccer players indicate that muscles are thinner and more elastic (less stiff) in more symptomatic athletes.



#8 Energy Requirements and Nutritional Strategies for Male Soccer Players: A Review and Suggestions for Practice

Reference: Nutrients. 2022 Feb 4;14(3):657. doi: 10.3390/nu14030657.

Authors: Andrew T Hulton, James J Malone, Neil D Clarke, Don P M MacLaren

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Summary: Soccer is a high intensity intermittent sport, featuring critical events completed at high/maximal intensity which is superimposed onto an aerobic base of lower intensity activities and rest. Due to these varying energic demands and the duration of competition the need for optimal nutritional strategies to offset and delay fatigue are paramount. Over the last 50 years, several investigations have been reported on aspects of soccer be they nutrition-focused or those concerning the demands of the sport. Emanating from these scientific papers, observations have been made on the likely factors which result in the fatigue during match-play. Factors such as muscle glycogen depletion and hypoglycaemia are discussed. Studies on the energy demands of soccer have employed a variety of methodologies which are briefly reviewed and vary between the use of heart rate telemetry to the use of global positioning systems (GPS). Moving on from observations of the energy demands of the sport leads to the major focus of this review which highlights key nutritional strategies to support the preparation and recovery of male soccer players to enhance performance, or at least to enable players to perform adequately. This review examines relevant methodologies in assessing training and competitive energy costs as well as the concomitant energy intakes demanded for successful performance outcomes. In order to bring an applied aspect to the overall findings from areas discussed, some practical ideas of feeding strategies are presented.



#9 Match-Related Statistics Differentiating Winning and Losing Teams at the 2019 Africa Cup of Nations Soccer Championship

Reference: Front Sports Act Living. 2022 Feb 25;4:807198. doi: 10.3389/fspor.2022.807198. eCollection 2022.

Authors: Alliance Kubayi, Paul Larkin

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Summary: This study investigated game-related statistics differentiating the winning and losings teams of matches during the 2019 African Cup of Nations (AFCON) soccer tournament. The sample consisted of 38 games, with the data obtained from the InStat Scout platform. Data were analyzed using mean (M), SD, effect size (ES), structure coefficients (SCs), and the Wilcoxon signed-rank test. The results showed that the winning teams performed significantly better than the losing teams in terms of shots (M = 12.13, SD = 4.67, Z = -2.26, ES = 0.62), shots on target (M = 5.05, SD = 2.54, Z = -4.22, ES = 1.13), and shots from counter-attacks (M = 2.24, SD = 1.42, Z = -2.48, ES = 0.57). Shots on target (SC = 1.22), shots (SC = -0.73), fouls (SC = 0.60), total passes (SC = 0.44), and yellow cards (SC = -0.32) presented the highest discriminatory power. These findings highlight the key match performance variables which influence the game results and may assist coaches in developing and implementing team strategies to improve the likelihood of winning the AFCON championship.



#10 Small-Sided Soccer Games with Larger Relative Areas Result in Higher Physical and Physiological Responses: a Systematic and Meta-Analytical Review

Reference: J Hum Kinet. 2022 Feb 10;81:163-176. doi: 10.2478/hukin-2022-0013. eCollection 2022 Jan.

Authors: Gibson Moreira Praça, Mauro Heleno Chagas, Sarah da Glória Teles Bredt, André Gustavo Pereira de Andrade

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Summary: This study aimed to systematically review the influence of the relative area on athletes' physical and physiological responses (outcomes) during small-sided games of soccer which were not matched to the relative area. It also presents a meta-analysis comparing standard small-sided games protocols with different relative areas. We searched the Web of Science and Scopus electronic databases for literature published up to March 2020 following all PRISMA guidelines for selecting articles for a qualitative and quantitative synthesis. As a result, eleven articles matched the inclusion criteria. For the quantitative synthesis, a pooled random-effects model was used to make pairwise comparisons between protocols with larger or smaller areas in each selected study. Prediction intervals were used to assess the heterogeneity. We found positive effects of larger relative areas per player on their total distance (d = 0.73; 95% CI = 0.12-1.34; p = 0.006; medium to large effect), distance covered at high speed (d = 0.93; 95% CI = 0.22-1.65; p = 0.001; large effect), and mean heart rate (d = 0.52; 95% CI = 0.17-0.88; p = 0.008; medium effect). In other words, larger relative areas were found to induce higher physical and physiological responses in players. Future studies should consider the relative area per player when comparing data for different small-sided games configurations to avoid confounding variables. Also, coaches can use relative area per player calculations to easily predict increases and decreases in expected training loads for different versions of SSGs during training.



#11 Seasonal Training Load Monitoring Among Elite Level Soccer Players: Perceived Exertion and Creatine Kinase Variations Between Microcycles

Reference: J Hum Kinet. 2022 Feb 10;81:85-95. doi: 10.2478/hukin-2022-0008. eCollection 2022 Jan.

Authors: Bruno Mendes, Filipe Manuel Clemente, Francisco Calvete, Sandro Carriço, Adam Owen

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Summary: The primary aim of the investigation was to determine the daily load variations between the microcycles of an entire season of an elite group of professional soccer players. The second aim of this study was to determine the relationships between Foster's rating of perceived exertion (RPE), the Hooper index (HI) and CK levels over the weekly microcycles of the season. Thirty-five male professional soccer players participated in this study (3 goalkeepers, 6 wide defenders, 4 central defenders, 9 midfielders, 8 wide midfielders and 4 forwards) (25.7 ± 5.0 years, 182.3 ± 6.4 cm; 79.1 ± 7.0 kg). Significant differences between months in the variables of HI (p = 0.001; ES = 0.052), minT (p = 0.001; ES = 0.066), IL (p = 0.001; ES = 0.052, minimum effect) and CK (p = 0.002; ES = 0.031) were found. Comparison of the HI (p = 0.044; ES = 0.002), minT (p = 0.001; ES = 0.045), and IL (p = 0.001; ES = 0.045) revealed significant differences between microcycles. No significant differences were found in CK (p = 0.710; ES = 0.001) across the period. A significantly higher internal training load and fatigue perception in microcycles with only one official match was found. The greater load occurred 3 to 4 days before the game. In addition, it can be concluded that the first quarter of the season seemed to induce a greater physical demand on elite professional players.



#12 The maturity status but not the relative age influences elite young football players' physical performance

Reference: Sci Med Footb. 2022 Mar 15;1-8. doi: 10.1080/24733938.2022.2053338. Online ahead of print.

Authors: Iván Peña-González, Alejandro Javaloyes, Eduardo Cervelló, Manuel Moya-Ramón

Summary: Talent identification and selection process in young football is based on coaches' decisions regarding the players' performance at early ages. The aim of this study was to show how the maturity status and the relative age impact on young football players' physical performance and their coaches' efficacy expectations. The physical performance (1RM, Peak power output [PPO], 30-m sprint and t-test) of 118 young football players (U13 to U15; and their coaches' efficacy expectations were assessed. Relative age was calculated according to the players' date of birth within their selection year. The maturity status was estimated as the years from/to their peak height velocity (PHV). Linear regression analyses showed a significant relationship between players' physical performance and their maturity status but not with their relative age. In contrast, the maturity status of players only was associated to the coaches' efficacy expectations in the 1RM and PPO tests, whereas the relative age was a predictor of the coaches' expectations about players' performance in the t-test. These findings may be important for coaches and managers in young football academies since inter-individual differences in the maturity status but not in the relative age are related to physical performance despite the coaches' expectations.



#13 Time to change direction in training load monitoring in elite football? The application of MEMS accelerometers for the evaluation of movement requirements

Reference: Sci Med Footb. 2022 Mar 15;1-10. doi: 10.1080/24733938.2022.2053337. Online ahead of print.

Authors: Matthew Green, Patrick Ward, Matthew Bickley, Mark Gillett, Andy O'Boyle, Barry Drust

Summary: In elite football, the emphasis is placed on monitoring the output from the Global Positioning Systems (GPS) component of a Micro-Electro-Mechanical Systems (MEMS) device; however, this does not comprehensively overview the total demands due to the intermittent multidirectional nature. The aim of the study was to investigate the application of accelerometer data provided by MEMS, to evaluate movement requirements in elite football. A two-staged research approach, involving an effectiveness and efficacy stage, was deployed. The effectiveness stage examined two MEMS-accelerometer variables (PlayerLoadTM (PL) and PlayerLoadTM per meter (PL.m-1)) for four years and four months. Ninety-nine English Premier League outfield football players' participated. In the efficacy stage, 26 elite outfield football players completed three different training modalities (running, possession and dribbling) and a range of MEMS-accelerometer variables were analysed. In the effectiveness stage, the mean difference in PL for all training activities other than Set Pieces were similar to Matches (-283 to -246au). Model coefficients for PL.m-1 were smallest in Team Shape (-0.00114au), Attacking (0.00025au) and Games (0.00196au), and largest for Possession (0.03356AU), Defending (0.03182au) and Skills Games (0.03106au) compared to Matches. The findings suggest that PL.m-1 but not PL may be effective at describing differences in movement requirements. In the efficacy stage, PL.m-1 and inertial movement analysis (IMA) efforts were the only variables that had greater mean differences in the smaller conditions, confirming PL.m-1's suitability in evaluating movement requirements of different training activities and pitch dimensions. The findings suggest such a variable offers value in a monitoring strategy in football.



#14 The influence of exposure, growth and maturation on injury risk in male academy football players

Reference: J Sports Sci. 2022 Mar 14;1-10. doi: 10.1080/02640414.2022.2051380. Online ahead of print.

Authors: David M Johnson, Sean P Cumming, Ben Bradley, Sean Williams

Summary: Adolescence is a period of increased injury risk in youth footballers; however, no studies have considered the influence of growth-related factors and exposure time upon injury risk. Forty-nine elite male youth footballers were prospectively monitored for growth, lower-limb growth, maturation, training volume and injury for one season. Generalised linear mixed-effects models were used to model growth rate, lower-limb growth rate, maturation, and smoothed week-to-week changes in exposure on time-loss injury risk. The relationship between growth rate and injury incidence was linear (P = 0.031) and injury burden was non-linear (P = 0.019). The relationship between lower-limb growth rate and injury incidence was linear and positive (P = 0.098). A non-linear relationship was observed between lower-limb growth rate and injury burden (P = 0.001). A non-linear relationship between Percentage of Predicted Adult Stature and both injury incidence and injury burden were found, with peak risk occurring at 92% and 95% , respectively. There was a positive linear relationship between week-to-week changeand injury incidence (P = 0.001), and a non-linear relationship between week-to-week change and injury burden (P = 0.01). Practitioners should monitor the timing and rate of the growth spurt and exposure time to identify players at greater injury risk.



#15 Sports Injuries Among Players of The Polish National Team in Amputee Football in The Annual Training Cycle

Reference: J Hum Kinet. 2022 Feb 10;81:211-219. doi: 10.2478/hukin-2022-0021. eCollection 2022 Jan.

Authors: Zofia Kasińska, Piotr Kazimierz Urbański, Tomasz Tasiemski

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Summary: The aim of the study was to determine the frequency, type and origin of the occurrence of injuries in amputee football. The studied group comprised all members of the Polish national amputee football team (n = 25). During the 9-month observation period, 13 players incurred 22 injuries. The incidence proportion was 48.0 per 100 athletes (95% Cl, 28.4-67.6) and the incidence rate was 5.73 per 1000 athlete-days (95% Cl, 3.33-8.12). The study showed that 32.8% of the injuries were to the thigh, 13.6% to the ankle, and 9.1% to the knee. The obtained results indicate that amputee football players rather frequently incur play-related injuries, but a single athlete incurs relatively few of them, with the lower limb being most commonly injured.



#16 Effect of support foot placement on football instep kick performance

Reference: Sci Med Footb. 2022 Mar 24;1-7. doi: 10.1080/24733938.2022.2055781. Online ahead of print.

Authors: Yu-Cheng Ou, Man Kit Lei, Kuangyou B Cheng

Summary: Although the support foot plays an important role in kicking a football, there has been a paucity of research exploring the effect of the placement of the support foot on kicking performance. To investigate the kick performance under different support foot positions, ten male footballers were recruited to participate in two experiments: one determining the maximum ball speed and the second determining accuracy. The participants were instructed to plant their support foot on one of nine different spots marked in the form of a 3 × 3 shape on a piece of artificial grass and asked to kick the ball. In the first (maximum speed) test, the participants tried their best to kick the ball at the maximum ball speed from nine different support foot positions. In the second (accuracy) test, the participants kicked the ball toward the target area without restricting the support foot position. The ball speed, as well as the success rate, were recorded from each support foot position. Significantly higher ball speed and accuracy were obtained at medial positions than was the case at lateral positions from the nine spots. It was concluded that although footballers may choose different positions for support foot placement, the maximum ball speed and better accuracy could be expected when the support foot was next to or slightly in front of the ball centre without too much side-by-side separation (27-37 cm).



#17 Estimation of maximal oxygen uptake using the heart rate ratio method in male recreational football players

Reference: Eur J Appl Physiol. 2022 Mar 17;1-8. doi: 10.1007/s00421-022-04928-0. Online ahead of print.

Authors: Carlo Castagna, Peter Krustrup, Susana Póvoas

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Summary: Maximal oxygen uptake (VO2max) is associated with cardiovascular and metabolic health in the general population. The heart rate (HR) ratio method (HRratio) is a valid, easy and accessible method for estimating VO2max in well-trained subjects. This study examined the validity of using the HRratio to estimate VO2max in recreational football players in the untrained and trained states. Sixty-six participants (age 39.3 ± 5.8 years) were tested pre-training and 28 after 12 weeks, for VO2max assessment, running on a treadmill alternating speed (1 km h-1) and inclination (1%) increments every 30 s until exhaustion. Maximal HR (HRmax) was assessed directly with a multiple approach and estimated with selected equations. Resting HR (HRrest) was measured in supine position, after 15 min of rest. The HRratio method considers the product of HRmax/HRrest ratio by a theoretical proportionality factor (15 ml kg-1 min-1, TPF) to estimate VO2max. This population-specific proportionality factor (SPF) was 14.6 ± 2.6 ml kg-1 min-1. In the untrained state (n = 66), participants' actual VO2max (41.3 ± 6.2 ml kg-1 min-1) was moderately lower (~ 2 ml kg-1 min-1) than the estimated VO2max using the TPF. A nonsignificant difference (0.7 ml kg-1 min-1) was found when the VO2max was estimated using the SPF. When using HRmax equations and the TPF, a small nonsignificant difference (~ 1.5 ml kg-1 min-1) was reported between actual and estimated VO2max. In the trained state (n = 28), the estimated VO2max values were not significantly different from the actual VO2max (44.2 ± 5.2 ml kg-1 min-1), with large effect sizes when considering TPF and estimated HRmax. The results of this study provide evidence of the applicability of HRratio in estimating VO2max in male adult/middle-aged recreational football players.



#18 Deficits in eccentric antagonist/concentric agonist strength ratios: a comparative study of football players with and without osteitis pubis

Reference: Eur Rev Med Pharmacol Sci. 2022 Mar;26(5):1559-1564. doi: 10.26355/eurrev_202203_28221.

Authors: W S Mohammad, W M Elsais

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Summary: Dynamic hip stabilizers are essential for optimal performance in football players, particularly during kicking. Although the muscle strength deficits of hip muscles as an etiology of osteitis pubis (OP) in football players have not yet been well investigated, previous assessments give more attention to the concentric mode of strength for both hip flexor and extensor muscles. Functionally, the hip muscles interact in an eccentric/concentric pattern. This study aimed to compare the concentric, eccentric, and eccentric antagonist/concentric agonist ratios for hip flexor and extensor strength between football players with OP and healthy athletes. Thirty-four male footballers with OP and eighteen healthy footballers were tested using an isokinetic dynamometer at a speed of 180°/s. Football players with osteitis pubis demonstrated a significantly lower eccentric extensor/concentric flexor ratio and higher eccentric hip flexor/extensor ratio (p < 0.05) when compared with healthy participants. The present study demonstrated that football players with OP had a reduced capability to produce eccentric hip extension torque compared to healthy athletes. Consequently, the eccentric rather than the concentric weakness of hip extensors could be suggested as one of the intrinsic contributing factors for OP. Incorporating findings of the current study in clinical practice could afford critical information while evaluating the hip muscles in football players with OP for pre-screening, developing rehabilitation programs, and guiding the decision to return to sports after injury.



#19 Ramadan Nutritional Strategy: Professional Soccer Player Case Study

Reference: Nutrients. 2022 Jan 21;14(3):465. doi: 10.3390/nu14030465.

Authors: Alejandro Martínez-Rodríguez, Laura Miralles-Amorós, Manuel Vicente-Martínez, Nuria Asencio-Mas, Rodrigo Yáñez-Sepúlveda, María Martínez-Olcina

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Summary: The period of Ramadan induces changes in the usual eating patterns of individuals. During this period, Muslims must abstain from drinking and eating from dawn to dusk. Therefore, some research conducted on professional soccer players has observed that during and/or after Ramadan, performance, running speed, agility, dribbling speed, and endurance and/or skill performance in athletic events may be negatively affected by Ramadan intermittent fasting (RIF). The objective of this study was to analyze the influence of a dietary plan during RIF on performance and body composition in a professional soccer player. A 20-year-old elite player (86.0 kg, 188.5 cm) followed a dietary-nutritional plan with an isocaloric diet and was supplemented with glycerol. The athlete's strength and power in the lower limbs was assessed by performing a countermovement jump (CMJ) and Abalakov vertical jump (ABK) before and after Ramadan. After nutritional planning, the patient's body composition improved in terms of fat loss (6.61 to 5.70%) and muscle mass gain (50.26 to 51.50%). In addition, this translated into improvements in performance tests, both in the CMJ (36.72 to 40.00 cm) and ABK (39.16 to 49.34 cm). In conclusion, during a period of fasting, personalised nutritional planning and an appropriate supplementation and rest protocol can improve the body composition and performance of soccer players.



#20 Molecular Hydrogen Mitigates Performance Decrement during Repeated Sprints in Professional Soccer Players

Reference: Nutrients. 2022 Jan 25;14(3):508. doi: 10.3390/nu14030508.

Authors: Michal Botek, Deepesh Khanna, Jakub Krejčí, Michal Valenta, Andrew McKune, Barbora Sládečková, Iva Klimešová

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Summary: Hydrogen-rich water (HRW) supplementation has been shown to have an antifatigue effect across different modes of exercise. However, its effect on repeated sprint performance is unknown. The aim of this study was to assess the effect of pre-exercise HRW consumption on repeated sprint performance, lactate, and perceptual responses using a repeated sprint protocol. This randomized, double blinded, placebo controlled, crossover study included 16 professional, male soccer players aged 18.8 ± 1.2 years. Athletes performed two indoor tests, particularly 15 × 30 m track sprints interspersed by 20 s of recovery, separated by a 1-week washout period. Sprint time was measured at 15 m and 30 m. Ratings of perceived exertion were assessed immediately after each sprint, and post-exercise blood lactate concentration was measured after the last sprint. There were significantly faster sprint times after HRW consumption compared with placebo at 15 m for the 14th and 15th sprints, representing improvements in time of 3.4% and 2.7%, respectively. Sprint time at 30 m also significantly improved by 1.9% in the HRW group in the last sprint. However, neither lactate concentrations nor ratings of perceived exertion were significantly different between HRW and placebo. Pre-exercise HRW supplementation is associated with an increased ability to reduce fatigue, especially during the later stages of repeated sprint exercise.



#21 Changes of 25(OH)D Concentration, Bone Resorption Markers and Physical Performance as an Effect of Sun Exposure, Supplementation of Vitamin D and Lockdown among Young Soccer Players during a One-Year Training Season

Reference: Nutrients. 2022 Jan 25;14(3):521. doi: 10.3390/nu14030521.

Authors: Joanna Jastrzębska, Maria Skalska, Łukasz Radzimiński, Guillermo F López-Sánchez, Katja Weiss, Lee Hill, Beat Knechtle

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Summary: The main purpose of this research was to demonstrate the changes in 25(OH)D concentration, bone resorption markers, and physical fitness along the one-year training season in young soccer players. A total of 24 young soccer players (age: 17.2 ± 1.16 years, mass: 70.2 ± 5.84, height: 179.1 ± 4.26 cm) were tested at four different time points across one year (T1-September 2019; T2-December 2019; T3-May 2020; T4-August 2020). After T2 (during COVID-19 lockdown), players were divided into a supplemented (GS) group and a placebo group (GP). Variables such as 25(OH)D, calcium (Ca), phosphorus (P), parathyroid hormone (PTH), aerobic capacity, speed, and explosive power were measured. Analyses performed for all participants indicated significant changes in all selected blood markers and running speed. The highest values in 25(OH)D were noted during summertime in T1 and T4. After individuals were split into two groups, a two-factorial ANOVA demonstrated a significant time interaction for 25(OH)D, Ca, P, PTH, 30 m sprint, and counter-movement jump. Significant time x group effect was calculated for aerobic capacity. This study confirmed that 25(OH)D concentration varies between four seasons, with the greatest decreases in the low sunlight periods. Vitamin D supplementation did not cause a preventive and long-lasting effect of increasing the 25(OH)D concentration in the young soccer players.






Comparison of Immediate Effects of Foam Rolling on Flexibility, Balance, and Agility in Male Soccer Players

The aim was to evaluate and compare the acute effects of DS as well as DS followed by FR (DS + FR) on flexibility, dynamic balance, and agility in male soccer players.





Effect of bio-banding on physiological and technical-tactical key performance indicators in youth elite soccer

Effect of bio-banding on physiological and technical-tactical key performance indicators in youth elite soccer.





Latest research in football - week 10 - 2022

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 Effects of Football Training and Match-Play on Hamstring Muscle Strength and Passive Hip and Ankle Range of Motion during the Competitive Season

Reference: Int J Environ Res Public Health. 2022 Mar 2;19(5):2897. doi: 10.3390/ijerph19052897.

Authors: Víctor Moreno-Pérez, Gil Rodas, Marcelo Peñaranda-Moraga, Álvaro López-Samanes, Daniel Romero-Rodríguez, Per Aagaard, Juan Del Coso

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Summary: Deficits in hamstring muscle strength and in hip range of motion (ROM) have been considered risk factors for hamstring muscle injuries. However, there is a lack of information on how chronic exposure to regular football training affects hamstring muscle strength and hip ROM. The aim of this study was to examine the longitudinal effect of football training and competition during a complete season on hamstring muscle strength and hip ROM in football players. A total of 26 semi-professional football players underwent measurements of isometric hamstring muscle strength and passive hip flexion/extension, and internal/external hip rotation (IR/ER) ROM during the football season (pre-season, mid-season, end-season). Compared to pre-season, hamstring muscle strength increased in the dominant (+11.1%, p = 0.002) and non-dominant (+10.5%, p = 0.014) limbs in the mid-season. Compared to mid-season, hamstring strength decreased in the dominant (-9.3%, p = 0.034) limb at end-season. Compared to the pre-season, hip extension ROM decreased in mid-season in the dominant (-31.7%, p = 0.007) and non-dominant (-44.1%, p = 0.004) limbs, and further decreased at end-season (-49.0%, p = 0.006 and -68.0%, p &lt; 0.001) for the dominant and non-dominant limbs. Interlimb asymmetry for hip IR ROM increased by 57.8% (p &lt; 0.002) from pre-season to mid-season. In summary, while hamstring muscle strength increased during the first half of the football season in football players, a progressive reduction in hip extension ROM was observed throughout the season. The reduced hip extension ROM suggests a reduced mobility of the hip flexors, e.g., iliopsoas, produced by the continuous practice of football. Consequently, hip-specific stretching and conditioning exercises programs should be implemented during the football season.



#2 Speed and Agility Predictors among Adolescent Male Football Players

Reference: Int J Environ Res Public Health. 2022 Mar 1;19(5):2856. doi: 10.3390/ijerph19052856.

Authors: Cíntia França, Élvio Gouveia, Romualdo Caldeira, Adilson Marques, João Martins, Helder Lopes, Ricardo Henriques, Andreas Ihle

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Summary: This study aimed to examine the associations between lower-body explosive strength (squat jump-SJ, and countermovement jump-CMJ), speed (10- and 35-m linear sprints), and agility (t-test) capacities, after controlling for crucial predictors such as chronological age (CA) and body composition. The sample was composed of 164 adolescent male football players from under 19, under 17, and under 15 age groups. Body fat percentage (BF%) was significantly and positively related to body mass, speed, and agility. In contrast, BF% was a significant negative predictor of lower-body explosive strength. Sprint and t-test times were significantly and negatively correlated with lower-body explosive strength. After controlling for CA and body composition, SJ was the most significant predictor, accounting for 36 to 37% of the variance observed in the 35 m linear sprint and the t-test performance. Our main results suggest that lower-body explosive strength, particularly in the SJ, is a significant predictor of male adolescent male football players' speed and agility capacities. Conversely, detrimental relationships between BF% and these outcomes were observed. Sports agents should consider lower-body explosive strength development as part of the youth football training process, particularly to improve maximal sprint and change of direction times, which are crucial to game performance.



#3 Biological, Psychological, and Physical Performance Variations in Football Players during the COVID-19 Lockdown: A Prospective Cohort Study

Reference: Int J Environ Res Public Health. 2022 Feb 26;19(5):2739. doi: 10.3390/ijerph19052739.

Authors: Giulia My, Santo Marsigliante, Antonino Bianco, Daniele Zangla, Carlos Marques da Silva, Antonella Muscella

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Summary: This prospective cohort study aimed to evaluate whether COVID-19 lockdown caused biological, psychological, and/or physical performance variations in footballers. We compared the 2018/2019 and 2019/2020 seasons evaluating the plasma volume, hematological parameters, iron/ferritin, creatine kinase, vitamin D, cortisol, testosterone, and physiological state of players of the Italian football major league (Serie A). Measurements were performed before the preparatory period (T0), at the beginning (T1) and in the middle (T2) of the championship, and in March (T3) and at the end of season (T4). The results showed that in the 2019/2020 season affected by the lockdown, the weight, BMI, and fat mass percentage were higher than in the previous season. Hematocrit, hemoglobin, red blood cells, and ferritin decreased during both seasons, more significantly than in the regular season. During both seasons, creatine kinase increased from T2 whilst iron concentrations decreased in T3. Testosterone increased in both seasons from T0 to T3 and returned to initial levels at T4; cortisol increased in T2 and T3 during the 2018/2019 season but not during the COVID-19 season. Physical performance tests revealed differences associated with lockdown. Thus, although from a medical point of view, none of the evaluated changes between the two seasons were clinically relevant, training at home during lockdown did not allow the players to maintain the jumping power levels typical of a competitive period.



#4 Dynamic Monitoring of Football Training Based on Optimization of Computer Intelligent Algorithm

Reference: Comput Intell Neurosci. 2022 Feb 28;2022:2199166.doi: 10.1155/2022/2199166. eCollection 2022.

Authors: Jin Gang

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Summary: Nowadays, with the development of computer science and technology, computer intelligent algorithms are more and more widely used in various industries. Every calculation formula in the computer intelligent algorithm has systematic logic and singleness, in order to expound the dynamic algorithm of football training optimized by the computer intelligent algorithm in detail. In this paper, the monitoring system using the computer intelligent algorithm can dynamically observe people or objects and systematically analyze them. This paper mainly studies the research of a football training dynamic monitoring system based on the computer intelligent algorithm and the design and optimization of the computer intelligent dynamic monitoring system in football training. Finally, the overall composition of the computer intelligent dynamic monitoring system and the application of the optimized computer intelligent dynamic monitoring system to the analysis of sample data are studied.



#5 Football players with long standing hip and groin pain display deficits in functional task performance

Reference: Phys Ther Sport. 2022 Feb 26;55:46-54. doi: 10.1016/j.ptsp.2022.02.023. Online ahead of print.

Authors: Eliza A Roughead, Matthew G King, Kay M Crossley, Josh J Heerey, Peter R Lawrenson, Mark J Scholes, Adam I Semciw, Benjamin F Mentiplay, Joanne L Kemp

Summary: The aim was to i)Compare functional task performance between football players with and without hip/groin pain. ii) Explore the relationship, and sex-specific effects, between functional tasks and the Copenhagen Hip and Groin Outcome Score (HAGOS) in players with hip/groin pain. 183 (38 women) football players with a self-reported history of >6months of non-time-loss hip/groin pain and a positive flexion-adduction-internal rotation test, and 61 (14 women) asymptomatic players participatd in this study. Participants completed the hop-for-distance (HFD), one leg rise (OLR), side bridge (SB) endurance, and HAGOS. Study aims were assessed using linear models, controlling for body mass index and age, incorporating sex-specific interaction terms. Players with hip/groin pain could not hop as far (adjusted mean difference: -9 cm, 95% CI: -15 cm to -2cm, P=0.012) and completed fewer OLR repetitions (adjusted mean difference -7, 95% confidence interval -11 to -3 repetitions, P=0.001) compared to asymptomatic players. Symptomatic women, but not symptomatic men, with worse HAGOS scores had lower SB endurance. Independent of sex, football players with worse HAGOS scores could not hop as far and completed fewer OLR repetitions. Football players with hip/groin pain demonstrated deficits in HFD and OLR with the performance of these tasks associated with their HAGOS results. The study identifies potential impairments that can be targeted as a component of rehabilitation programs for football players with hip/groin pain.



#6 The influence of tactical and match context on player movement in football

Reference: J Sports Sci. 2022 Mar 7;1-15. doi: 10.1080/02640414.2022.2046938. Online ahead of print.

Authors: Sam Gregory, Sam Robertson, Robert Aughey, Grant Duthie

Summary: Player movement metrics in football such as speed and distance are typically analysed as aggregates, sometimes outside of any specific tactical or match context. This research adds context to a player's movement over the course of a match by analysing movement profiles s and bringing together tools from the sport science and sports analytics literature. Position-specific distributions of player movement metrics: speed, acceleration and tortuosity were compared across phases of play and in-game win probability using 25 Hz optical player tracking data from all 52 matches at the 2019 FIFA Women's World Cup. Comparing the distributions using the Kolmogorov-Smirnov test and Wasserstein distances, differences were identified in these movement profiles across, in and out of possession phases, with small negligible overall positional trends across in-game win probabilities. In-game win probabilities are used in tandem with phases to present a player specific case study. The results demonstrate how sports analytics metrics can be used to contextualise a subset of movement metrics from sport science and provide a framework for analysis of further movement metrics and sports analytics modelling approaches.



#7 Executive summary: Elite women's football-Performance, recovery, diet, and health

Reference: Scand J Med Sci Sports. 2022 Mar 7. doi: 10.1111/sms.14145. Online ahead of print.

Authors: Magni Mohr, Joao Brito, Maysa de Sousa, Svein Arne Pettersen

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Summary: The present special issue of Scandinavian Journal of Medicine & Science in Sports focuses on performance, recovery, diet, and health in elite women's football. Beside this summary, an editorial, topic reviews, and original articles written by several of the most published authors in football research are presented. It is, for example, highlighted that there is a great gender inequality in football research in favor of men, especially within elite football populations. Therefore, the broad-spectrum content of the special issue with focus on several performance areas in women's football, recovery strategies, nutrition, and psychological factors is highly warranted. Several of the topics examined and data presented are examined for the first on elite women's football, and therefore, we hope that this special issue will contribute to gender balance the research and emphasis on football in both genders.



#8 Muscular heat shock protein response and muscle damage after semi-professional football match

Reference: Scand J Med Sci Sports. 2022 Mar 5. doi: 10.1111/sms.14148. Online ahead of print.

Authors: Håvard Wiig, Kristoffer T Cumming, Vilde Handegaard, Jostein Stabell, Matthew Spencer, Truls Raastad

Summary: A typical football match leads to neuromuscular fatigue and physical performance impairments up to 72-96 h post-match. While muscle damage is thought to be a major factor, damage on the ultrastructural level has never been documented. The purpose of this study was to investigate post-match cellular muscle damage by quantifying the heat shock protein (HSP) response as a proxy for protein damage. Muscle biopsies, blood samples, countermovement jumps, and perception of muscle soreness were obtained from twelve semi-professional football players 1, 24, 48, and 72 h after a 90-min football match. Muscle biopsies were analyzed for αB-crystallin and HSP70 in the cytosolic and cytoskeletal sub-cellular fractions by Western blotting. Fiber type-specific αB-crystallin and HSP70 staining intensity, and tenascin-C immunoreactivity were analyzed with immunohistochemistry. Blood samples were analyzed for creatine kinase and myoglobin. Within 24 h post-match, a 2.7- and 9.9-fold increase in creatine kinase and myoglobin were observed, countermovement jump performance decreased by -9.7% and muscle soreness increased by 0.68 units. αB-crystallin and HSP70 accumulated in cytoskeletal structures evident by a 3.6- and 1.8-fold increase in the cytoskeletal fraction and a parallel decrease in the cytosolic fraction. In type I and II fibers, αB-crystallin staining intensity increased by 15%-41% and remained elevated at 72 h post-match. Lastly, the percentage of fibers with granular staining of αB-crystallin increased 2.2-fold. Football match play induced a muscular HSP stress response 1-72 h post-match. Specifically, the accumulation of HSPs in cytoskeletal structures and the granular staining of αB-crystallin suggests occurrence of ultrastructural damage. The damage, indicated by the HSP response, might be one reason for the typically 72 h decrease in force-generating capacity after football matches.



#9 Common genetic basis of ALS patients and soccer players may contribute to disease risk

Reference: Neurol Sci. 2022 Mar 5. doi: 10.1007/s10072-022-05990-4. Online ahead of print.

Authors: Sigal Ben-Zaken, Beatrice Nefussy, Yoav Meckel, Alon Eliakim, Dan Nemet, Marc Gotkine, Dana Lorber, Aviva Zeev, Vivian E Drory

Summary: The aim of the present study was to determine the prevalence of the ACSL A/G single nucleotide polymorphism among athletes and patients with amyotrophic lateral sclerosis (ALS). ALS is a progressive neurodegenerative disorder of motor neurons that leads to paralysis and death usually within 3-5 years from onset. Previous epidemiological studies reported a higher risk of ALS among soccer players. The ACSL (long-chain-fatty-acid-CoA ligase 1) gene codes the long-chain fatty-acid-coenzyme A ligase family that plays a key role in lipid biosynthesis and fatty acid oxidation. The ACSL A/G polymorphism is associated with endurance trainability. One hundred and seventy-eight ALS patients, 172 athletes (60 soccer players, 112 middle- and long-distance runners), and 111 nonathletic controls participated in the study. Genomic DNA was extracted from blood or buccal cells according to the salting-out procedure. Genotypes were determined using the TaqMan allelic discrimination assay. The prevalence of the ACSL AA genotype was significantly higher among soccer players (35.0%) and ALS patients (39.3%) compared to runners (16.1%) and controls (18.0%). However, ALS GG carriers had a higher mortality rate. We postulate that soccer players and ALS patients carry a common genetic predisposition that is related to impaired fatty acid utilization. Moreover, while the A allele might be associated with a genetic predisposition toward ALS, especially among soccer players, the G allele might be associated with disease severity. Further research is needed in order to explore the role of the ACSL rs6552828 polymorphism in ALS.



#10 Physical loading in professional soccer players: Implications for contemporary guidelines to encompass carbohydrate periodization

Reference: J Sports Sci. 2022 Mar 6;1-20. doi: 10.1080/02640414.2022.2044135. Online ahead of print.

Authors: Liam Anderson, Barry Drust, Graeme L Close, James P Morton

Summary: Despite more than four decades of research examining the physical demands of match-play, quantification of the customary training loads of adult male professional soccer players is comparatively recent. The training loads experienced by players during weekly micro-cycles are influenced by phase of season, player position, frequency of games, player starting status, player-specific training goals and club coaching philosophy. From a macronutrient perspective, the periodization of physical loading within (i.e., match versus training days) and between contrasting micro-cycles (e.g., 1, 2 or 3 games per week schedules) has implications for daily carbohydrate (CHO) requirements. Indeed, aside from the well-recognised role of muscle glycogen as the predominant energy source during match-play, it is now recognised that the glycogen granule may exert regulatory roles in activating or attenuating the molecular machinery that modulate skeletal muscle adaptations to training. With this in mind, the concept of CHO periodization is gaining in popularity, whereby CHO intake is adjusted day-by-day and meal-by-meal according to the fuelling demands and specific goals of the upcoming session. On this basis, the present paper provides a contemporary overview and theoretical framework for which to periodize CHO availability for the professional soccer player according to the "fuel for the work" paradigm.



#11 Soccer players show the highest seasonal groin pain prevalence and the longest time loss from sport among 500 athletes from major team sports

Reference: Knee Surg Sports Traumatol Arthrosc. 2022 Mar 8. doi: 10.1007/s00167-022-06924-5.

Authors: Michele Mercurio, Katia Corona, Olimpio Galasso, Simone Cerciello, Brent Joseph Morris, Germano Guerra, Giorgio Gasparini

Summary: Groin pain is a widely recognized medical issue among athletes. Groin pain can affect both player and team performance and sometimes can be a career-ending injury. The aim of this study was to assess seasonal groin pain prevalence and the average seasonal time loss from sport for each injury in different team sport athletes. The hip and groin functionality at the beginning of the following season was also investigated. A cross-sectional study was undertaken on 600 team sport athletes (soccer, futsal, basketball, volleyball, and water polo players). The seasonal prevalence of groin pain, level of competition (professional and non-professional), time loss, and concomitant injuries in addition to groin pain were reported and analyzed. The Copenhagen Hip and Groin Outcome Score (HAGOS) was used to assess hip and groin pain and function related to sport and activity. Among the 506 (84%) players included, 123 players (24.3%) reported groin pain. Overall, soccer players reported the highest groin pain prevalence (32.5%) followed by futsal (25.5%), basketball (25.2%), water polo (17.6%) and volleyball players (13.6%). Professional soccer, futsal and basketball athletes showed higher groin pain prevalence in comparison with non-professional athletes (p = 0.02, p = 0.005 and p = 0.004, respectively). The mean time loss from sport due to groin pain was 60.3 ± 66 days in soccer, 41.1 ± 16.6 days in futsal, 31.5 ± 18 days in water polo, 37.2 ± 14.2 days in basketball and 50.8 ± 24.6 days in volleyball. Significantly lower HAGOS values were found in athletes with groin pain for all sports evaluated compared to athletes with no groin pain history (p = 0.0001). Longer time loss from sport was correlated with lower HAGOS values in soccer (p = 0.002) and futsal (p = 0.002) players with groin pain. Concomitant injuries were correlated with lower HAGOS values in water polo players (p = 0.03). Seasonal groin pain occurs in as many as one in four team sport athletes. Soccer players show the highest groin pain prevalence and the longest time loss from sport. Professional athletes report higher prevalence of groin pain in comparison with non-professional athletes. HAGOS appears to be a valid outcome instrument to measure groin pain, correlating with both time loss from sport and concomitant injuries in athletes.



#12 Effect of an Energy Drink On Muscle and Liver Damage Enzymes, And Cardiovascular Indices in Soccer Players

Reference: Sci Med Footb. 2022 Mar 10;1-7. doi: 10.1080/24733938.2022.2051728. Online ahead of print.

Authors: Fahimeh AdibSaber, Soleyman Ansari, Alireza Elmieh, Hadi Rajabzadeh

Summary: Despite emerging evidence about the influence of energy drinks on the quality of athletes' performance, there is little information about their effects on exercise-induced damage markers after long-term activities. This study aimed to investigate the acute effects of hype energy drink (HED) to ameliorate liver and muscle damage enzymes and cardiovascular indices-induced by a soccer match. A total of 22 elite male soccer players (age 20.36 ± 1.91) were recruited. Participants performed two experimental conditions, separated by a 14-day washout period. They consumed 2 × 250 ml of HED or placebo for 5 d before the soccer match, on match day, and for 1-day post-match. Measurements of muscle (CK and LDH), and liver (ALT, AST, and ALP) damage indices, and blood pressure (BP) parameters were taken at baseline, pre-match, post-match, and 24 h post-match. The results showed that the levels of ALT, AST, ALP, CPK, and LDH enzymes significantly decreased in HED condition from pre-match to 24 h post-match, compared with placebo (p < 0.001). Also, consumption of energy drinks reduced systolic, diastolic, and mean BP. In conclusion, elevated serum levels of muscle and liver damage enzymes and higher values of BP indices are improved 24 hours after soccer match following HED ingestion, compared to placebo. Therefore, it seems that consuming HED can lead to faster recovery of muscle and liver damage and improve recovery in soccer players.



#13 Multimodal imaging of soccer ball-related ocular posterior segment injuries

Reference: Eur J Ophthalmol. 2022 Mar 9;11206721221086230. doi: 10.1177/11206721221086230.

Authors: William Carrera, Caleb Ng, Jayson Koppinger, Asma Saud, Judy J Chen, Anita Agarwal, Robert N Johnson, J Michael Jumper, Brandon Lujan, H Richard McDonald

Summary: The purpose was to investigate the clinical and anatomic characteristics of soccer ball-induced posterior segment injuries in the era of modern multi-modal imaging. Retrospective case series of patients with soccer ball injury and diagnostic imaging from 2007 to 2020 at a single vitreoretinal practice. Eight patients met inclusion criteria. Fundus photographs (FP) and optical coherence tomography (OCT) were obtained in eight patients, fundus autofluorescence (FAF) in five patients, fluorescein angiography (FA) in three patients, and en-face OCT and OCT-Angiography (OCT-A) were obtained in two patients each. FA and FAF identified traumatic pigment epitheliopathy secondary to commotio. Increased hypo-autofluorescence was associated with shallow, peripheral retinal detachment on FAF. OCT of the macula displayed outer retinal changes associated with commotio, and offered insight into the acute and subacute changes of traumatic macular hole formation. A patient displayed foveal hyper-reflectivity in the shape of an hourglass with retinal cyst at the level of the external limiting membrane (ELM) as seen on OCT and En-face OCT. A patient with commotio involving the macula lacked microvascular changes on OCT-A. OCT, FA, and FAF imaging may aid in the work-up and management of the soccer ball-related posterior segment injuries.



#14 Analyzing the relationship between self-efficacy and impulsivity in amateur soccer referees

Reference: PeerJ. 2022 Mar 4;10:e13058. doi: 10.7717/peerj.13058. eCollection 2022.

Authors: José López-Aguilar, Rafael Burgueño, Alfonso Castillo-Rodriguez, Wanesa Onetti-Onetti

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Summary: Soccer referees (SRs) are exposed to stressful situations during the competition that can affect decision-making, could be affected by impulsivity during the competition and therefore, require optimal psychological skills. The objective of this study was to ascertain and analyze the relationship between levels of impulsivity and self-efficacy of amateur SRs in the senior category. A total of 21 Spanish SRs participated in this study (age 23.57 ± 2.40 years and 7.81 ± 2.58 seasons of experience). Self-efficacy data were collected with the REFS questionnaire between 48 and 72 h before the competition. The impulsivity data were collected using the UPPS-P questionnaire 60 min before the start the competition. The results indicate that SRs with higher self-efficacy have lower levels of impulsivity, specifically in the dimensions of negative urgency (p < 0.01), positive urgency (p < 0.05), lack of premeditation (p < 0.001), and lack of perseverance (p < 0.001), as well as lower global impulsivity (p < 0.01). However, the SRs with the highest self-efficacy also obtained higher levels in the sensation seeking dimension (p < 0.05). In conclusion, the main finding of this study showed that self-efficacy is influenced by SR impulsivity prior to competition. These novel facts allow us to discover aspects related to decision-making in refereeing that can be trained to reach optimal levels.



#15 Weekly Variations of Well-Being and Interactions with Training and Match Intensities: A Descriptive Case Study in Youth Male Soccer Players

Reference: Int J Environ Res Public Health. 2022 Mar 2;19(5):2935. doi: 10.3390/ijerph19052935.

Authors: Ana Filipa Silva, Rafael Oliveira, Stefania Cataldi, Filipe Manuel Clemente, Francesca Latino, Georgian Badicu, Gianpiero Greco, César Leão, Valerio Bonavolontà, Francesco Fischetti

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Summary: The aim of this study was two-fold: (i) analyze the weekly variations of well-being and training/match intensity measures in youth soccer players, and (ii) test relations between well-being and training intensity outcomes. The study followed a descriptive case study design. Twenty-seven under-17 male soccer players were monitored for well-being and training intensity parameters over seventeen consecutive weeks. An adjusted version of the Hooper questionnaire was used to monitor the perceptive sleep quality, readiness, fatigue, and delayed onset muscle soreness (DOMS) early in the morning. The CR-10 Borg's scale was also used for monitoring the rate of perceived exertion (RPE) of players after training sessions. Repeated-measures analysis of variance was executed to test the between-week variations of both well-being and training intensity outcomes. Moreover, Pearson product moment correlation was used to test the relations between well-being and training intensity outcomes. Repeated measures ANOVA revealed significant differences between weeks in the sleep quality (F = 0.422; p &lt; 0.001; ηp2 = 0.140), readiness (F = 0.8.734; p &lt; 0.001; ηp2 = 0.251), fatigue (F = 4.484; p &lt; 0.001; ηp2 = 0.147), DOMS (F = 3.775; p = 0.001; ηp2 = 0.127), RPE (F = 7.301; p &lt; 0.001; ηp2 = 0.219), and session-RPE (F = 17.708; p &lt; 0.001; ηp2 = 0.405). Correlations between well-being and training intensity outcomes in the same week revealed moderate correlations between fatigue and session-RPE (r = 0.325). As conclusions, it was found that well-being and training intensity fluctuates over the season, while well-being outcomes seems to be related with training intensity, although with a small magnitude.



#16 Fitness, Fatness, and Academic Attainment in Male Schoolchildren from a Soccer Academy

Reference: Int J Environ Res Public Health. 2022 Mar 6;19(5):3106. doi: 10.3390/ijerph19053106.

Authors: Souhail Hermassi, Thomas Bartels, Lawrence D Hayes, René Schwesig

Summary: This investigation explored the association between anthropometric measures, fitness, and academic attainment (mathematics and science grade point average [GPA]) in male schoolchildren from a soccer academy. Thirty-one males (age: 10.3 ± 1.19 years; body mass: 41.7 ± 6.5 kg; height: 1.43 ± 0.07 m; body mass index (BMI): 20.2 ± 2.8 kg/m2) participated. Body mass, body fat percentage (%BF), and BMI were used as measures of anthropometry. The Yo-Yo Intermittent Recovery Test (level 1), squat and counter-movement jumps (SJ and CMJ), static balance, 10 and 15 m sprint, and a T-half test for change-of-direction (CoD) performance were used to measure fitness parameters. The GPA of mathematics and science determined academic attainment. All physical performance tests showed excellent relative reliability. ICC was between 0.87 (10 m sprint) and 1.00 (15 m sprint, CMJ). Regarding correlations between fatness and academic attainment, we found three correlations of practical value (r &gt; 0.5), but only for mathematics (BMI: r = 0.540, subscapular skinfold: r = 0.589, body fat: r = 0.560). Mathematics was relevantly correlated with 15 m sprint (r = 0.574) and Yo-Yo IR1 test (r = 0.770). Only static balance (r = 0.428) did not reach the relevance criteria (r &gt; 0.5). Science only showed large correlations with static balance (r = 0.620) and Yo-Yo IR1 test (r = 0.730). In conclusion, fatness and fitness are related to academic attainment in schoolchildren. In addition, except for static balance, all physical performance parameters were relevantly (r &gt; 0.5) correlated with mathematics.



#17 Fitness, Fatness, and Academic Attainment in Male Schoolchildren from a Soccer Academy

Reference: Int J Environ Res Public Health. 2022 Mar 6;19(5):3106. doi: 10.3390/ijerph19053106.

Authors: Souhail Hermassi, Thomas Bartels, Lawrence D Hayes, René Schwesig

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Summary: This investigation explored the association between anthropometric measures, fitness, and academic attainment (mathematics and science grade point average [GPA]) in male schoolchildren from a soccer academy. Thirty-one males (age: 10.3 ± 1.19 years; body mass: 41.7 ± 6.5 kg; height: 1.43 ± 0.07 m; body mass index (BMI): 20.2 ± 2.8 kg/m2) participated. Body mass, body fat percentage (%BF), and BMI were used as measures of anthropometry. The Yo-Yo Intermittent Recovery Test (level 1), squat and counter-movement jumps (SJ and CMJ), static balance, 10 and 15 m sprint, and a T-half test for change-of-direction (CoD) performance were used to measure fitness parameters. The GPA of mathematics and science determined academic attainment. All physical performance tests showed excellent relative reliability. ICC was between 0.87 (10 m sprint) and 1.00 (15 m sprint, CMJ). Regarding correlations between fatness and academic attainment, we found three correlations of practical value (r &gt; 0.5), but only for mathematics (BMI: r = 0.540, subscapular skinfold: r = 0.589, body fat: r = 0.560). Mathematics was relevantly correlated with 15 m sprint (r = 0.574) and Yo-Yo IR1 test (r = 0.770). Only static balance (r = 0.428) did not reach the relevance criteria (r &gt; 0.5). Science only showed large correlations with static balance (r = 0.620) and Yo-Yo IR1 test (r = 0.730). In conclusion, fatness and fitness are related to academic attainment in schoolchildren. In addition, except for static balance, all physical performance parameters were relevantly (r &gt; 0.5) correlated with mathematics.



#18 The Uptake of Nordic Hamstring Exercise Program for Injury Prevention in Major League Soccer and Its Barriers to Implementation in Practice

Reference: J Sport Rehabil. 2022 Mar 10;1-6. doi: 10.1123/jsr.2021-0262. Online ahead of print.

Authors: Paul Chesterton, Garrison Draper, Matthew Portas, Craig Tears

Summary: It is well demonstrated that Nordic hamstring (NH) program has poor compliance across European soccer clubs, but little is known about its implementation in Major League Soccer (MLS). The authors aimed to investigate MLS hamstring prevention practices and compliance with the NH program and understand the reasons for its inclusion or exclusion. A cross-sectional electronic survey was completed by 24 of the 26 (92%) MLS top-division soccer clubs. The survey, based on the Reach, Efficacy, Adoption, Implementation, and Maintenance framework, was sent to team medical staff. Medical staff were also asked for opinions on barriers to implementation. Eighteen clubs (75%) reported a formal hamstring injury prevention program, with eccentric exercises (94%; 95% CI [confidence interval], 74%-99%), high-speed running (94%; 95% CI, 74%-99%), and NH exercises (89%; 95% CI, 67%-97%) the most common strategies adopted. Fifteen clubs partially implemented the NH program, but only 5 (21%; 95% CI, 9%-40%) completed the full program and were classed as compliant. A total of 20 respondents reported that player perception and muscle soreness (83%; 95% CI, 64%-93%) were barriers to the implementation of the NH program. On a 5-point Likert scale, respondents "partially agreed" (4.13 [0.80]) that the NH exercise could substantially reduce injuries and would be "effective" at their own club (3.88 [0.61]). The NH exercise was valued, but negative player perception and muscular soreness were identified as barriers to implementing the full program. Manipulation of volume and frequency should inform future "effectiveness" research to prospectively assess such modifications in the context of MLS.



#19 High-speed training in a specific context in soccer: transition games

Reference: Int J Sports Med. 2022 Mar 10. doi: 10.1055/a-1794-9567. Online ahead of print.

Authors: Jose Asian-Clemente, Alberto Rabano-Munoz, Bernardo Requena, Luis Suarez-Arrones

Summary: The aims of this study were to compare the load of three tasks designed to train features of soccer: a transition game, a small-sided game with a change of playing area, and a large-sided game. Twenty young elite players performed these tasks. Variables measured were total distance covered (DC), distance covered at 14.0-17.9 km·h-1 (DC 14.0-17.9 km·h-1), distance covered at 18.0-21 km·h-1 (DC 18-21 km·h-1), distance covered at >21 km·h-1 (DC >21 km·h-1), peak speed, accelerations and decelerations >1.0 and >2.5 m·s-2, player load, and rate of perceived exertion. Transition games produced greater DC 18-21 km·h-1, DC >21 km·h-1, peak speed and Acc >2.5 m·s-2 than the other drills (p<0.01) and higher DC 14-17.9 km·h-1 (p<0.01), Dec >1 m·s-2 (p<0.05) and Dec >2.5 m·s-2 (p<0.01) than the large-sided game. Both sided games produced more DC (p<0.01), Acc >1 m·s-2 (p<0.01) and player load (p<0.01 and p<0.05, respectively) than the transition game. During the small-sided game, significantly higher DC 14-17.9 km·h-1, DC 18-21 km·h-1 and DC >21 km·h-1 were recorded in comparison with the large-sided game (p<0.01). The studied parameters showed lower variation in the transition game. Coaches could use transition games to train high speed running in counter-attack contexts.



#20 The impact of COVID-19 lockdown on soccer positional and physical demands in the Spanish La Liga

Reference: Sci Med Footb. 2022 Mar 18. doi: 10.1080/24733938.2022.2055784. Online ahead of print.

Authors: Tomás García-Calvo, Javier Fernandez-Navarro, Jesús Díaz-García, Roberto López-Del Campo, Fermín Martínez Fernández, Daniel Memmert

Summary: The present study aimed to analyse the playing surface area, dispersion and distance covered of professional football teams comparing the pre-lockdown and the post- lockdown periods. Positional and match physical demands data were collected from all matches played in the First Spanish Division (n = 760) during season 2019/2020. Pre-lockdown (1st - 27th matchday) and post-lockdown period (28th - 38th matchday) were compared. Variables related to team-level spatial (i.e., convex hull, team width and team length) and physical performance (i.e., total distance and high-speed running distance) were analysed using an optical tracking system (i.e., ChyronHego). In addition, these variables were concerning in respect to the match location contextual variable. Linear mixed models were used to examine the difference between the pre-lockdown and post- lockdown periods following a hierarchical structure considering players, matches and teams. The results revealed that the pandemic lockdown affected the teams' performance when comparing the periods before and after lockdown, showing a general decrease in the average values of the spatial and physical variables measured. The current data could assist practitioners in making informed decisions in order to design and improve training plans for similar situations in which teams return to competition after an unusual period with no training.



#21 An audit of performance nutrition services in English soccer academies: implications for optimising player development

Reference: Sci Med Footb. 2022 Mar 21;1-11. doi: 10.1080/24733938.2022.2055785. Online ahead of print.

Authors: Daniel J Carney, Marcus P Hannon, Nicholas M Coleman, Rebecca C Murphy, Graeme L Close, James P Morton

Summary: To audit the current provision of performance nutrition services provided to male adolescent players within academies from the English soccer leagues. Practitioners from all 89 academies (status categorised as one-four according to the Elite Player Performance Plan, EPPP) completed an online survey to audit: a) job role/professional accreditation status of persons delivering nutrition support, b) activities inherent to service provision, c) topics of education, d) on-site food, fluid and supplement provision and e) nutritional related data collected for objective monitoring. More full-time accredited nutritionists are employed within category one (14/26) versus category two (0/18), three (1/41) and four (0/4). Respondents from category one clubs report more hours of monthly service delivery (62 ± 57 h) than category two (12 ± 9 h), three (14 ± 26 h) and four (12 ± 14 h), inclusive of one-to-one player support and stakeholder education programmes. Category one practitioners reported a greater prevalence of on-site food, fluid and supplement provision on training and match days. Across all categories, players from the professional development phase receive more frequent support than players from the youth development phase, despite the latter corresponding to the most rapid phase of growth and maturation. We report distinct differences in the extent of service provision provided between categories. Additionally, players from all categories receive nutrition support from non-specialist staff. Data demonstrate that performance nutrition appears an under-resourced component of academy sport science and medicine programmes in England, despite being an integral component of player development.



#22 Return to Play and Player Performance After Foot Fracture in UEFA Soccer Players

Reference: Orthop J Sports Med. 2022 Mar 11;10(3):23259671221078308. doi: 10.1177/23259671221078308. eCollection 2022 Mar.

Authors: Connor C Diaz, Ophelie Z Lavoie-Gagne, Avinaash Korrapati, Nalin S John, Mariah I Diaz, Enrico M Forlenza, Nicholas A Trasolini, Brian Forsythe

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Summary: There is a paucity of information on rate and time to return to play (RTP) in elite-level soccer players who have sustained foot fractures. The purpose was to (1) determine the rate and timing of RTP after foot fracture (eg, tarsal, metatarsal, or phalangeal), (2) investigate foot fracture reinjury incidence after RTP, and (3) evaluate performance after foot fracture as compared with matched, uninjured controls. Athletes sustaining foot fractures were identified across the 5 major European soccer leagues (English Premier League, Bundesliga, La Liga, Ligue 1, and Serie A) between 2000 and 2016. Injured athletes were matched to controls (1:1) using demographic characteristics and performance metrics from 1 season before injury. The authors recorded RTP rate, reinjury incidence, player characteristics associated with RTP within 2 seasons of injury, player availability, field time, and performance metrics during the 4 seasons after injury. A total of 192 elite soccer players sustaining a foot fracture were identified; 40 players (20.8%) underwent operative treatment. Athletes missed an average of 69.41 ± 59.43 days and 5.15 ± 23.28 games. In the 4 seasons after injury, 80% of players returned to play, with 72% returning to play within 1 season of injury. Nine players (5%) sustained a subsequent foot fracture. Athletes with a foot fracture demonstrated significantly longer league retention compared with uninjured controls (P < .001). Elite soccer players older than 30 years of age were less likely to RTP (odds ratio, 0.67; P = .002), whereas career experience, field position, and baseline performance showed no significant association with RTP rates. Injured athletes demonstrated similar performance to controls during the 4 years after injury, and there were no position-dependent differences on subgroup analysis. The players who underwent operative treatment had more assists per 90 minutes and more team points per game during the first season after injury compared with athletes treated nonoperatively. Foot fractures in elite soccer players resulted in moderate loss of play time (69.41 days). RTP rates were high at 80%, although players older than 30 years of age were less likely to RTP. On RTP, athletes who sustained a foot fracture maintained performance similar to preinjury levels and to uninjured controls.






Fascial therapy, strength exercises and taping in soccer players with recurrent ankle sprains: A randomized controlled trial

The aim was to evaluate the effectiveness of a fascial therapy and strength training, combined with kinesio taping, in improving ankle range of motion, pain, strength and stability in footballers with recurrent sprains.





Screening Youth Soccer Players by Means of Cognitive Function and Agility Testing

The aims of this study was to investigate a valid and simple method of testing for a unique combination of cognitive and speed abilities for identifying promising soccer players at mid-childhood.





Latest research in football - week 9 - 2022

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 Is there a relationship between lower-extremity injuries and foot postures in professional football players? A prospective cohort study

Reference: Sci Med Footb. 2022 Feb;6(1):49-59. doi: 10.1080/24733938.2020.1870711. Epub 2021 Apr 8.

Authors: Afsaneh Safar Cherati, Salman Khalifeh Soltani, Navid Moghadam, Bahar Hassanmirzaei, Zohreh Haratian, Shayesteh Khalifeh Soltani, Meisam Rezaei

Summary: Lower extremity injuries are an ongoing concern for professional football players. This study aims to evaluate the relationship between foot posture and lower extremity injuries in professional football players. In this prospective cohort study, 420 male players of the Iran Premium football league were evaluated during the 2015-2016 season. The players were assessed for their foot types based on optical and static foot scans and foot posture index (FPI). The trained club physicians recorded all injuries during the season. The analyzed data of 244 players showed the highest rate of lower extremity injury in hamstrings, ankle, and groin, respectively. These injuries led to 46% of time loss. The probability of hamstrings injuries was higher among pronated players based on static, optic, FPI, and visual examination, 2.1, 1.8, 1.8, and 2.3, respectively. Medial Collateral Ligament (MCL) injuries were associated with subtalar joint abnormality defined by visual observation. An increased relative risk of leading-to-absence injuries among the flat foot group was significant based on optic scanning, FPI, and visual observation. Abnormal foot postures in professional football players may increase the risk of hamstring and MCL injuries and time loss due to lower extremity injuries.



#2 The Irish Football Player Pathway: Examining Stakeholder Coherence Throughout and Across the Player Development System

Reference: Front Sports Act Living. 2022 Feb 14;4:834633. doi: 10.3389/fspor.2022.834633. eCollection 2022.

Authors: Liam Sweeney, Áine MacNamara, Dan Horan

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Summary: Maximizing the efficiency of the player development system is a strategic priority for any professional football club or association. However, the successful development of a young footballer is largely dependent upon the roles and relationships of the different stakeholders invested in the developmental process. This study examined the level of horizontal (i.e., extent to which stakeholders across a pathway stage work with players in an agreed fashion to optimize their experience) and vertical (i.e., extent to which multiple stages of the pathway are coordinated and build chronologically from previous involvement toward long-term needs) stakeholder coherence throughout the Irish football player pathway following a restructuring of development policies and the implementation of a nationwide academy system between 2016 and 2020 under the Football Association of Ireland's (FAI) Player Development Plan. As a second aim, we explored each of the key stakeholders' alignment to academic talent development principles in order to provide practical recommendations for future player and coach development policies. Accordingly, a series of interviews were conducted with 31 key stakeholders currently engaged in the player pathway. These key stakeholders consisted of parents, coaches and members of the FAI as the National Governing Body for football in Ireland. Data were analyzed using Reflexive Thematic Analysis, with findings highlighting a lack of stakeholder coherence across the pathway, both vertically and horizontally. Stakeholders displayed inconsistency in their understanding of the purpose of the player pathway and its long-term strategic aims, as well as demonstrating poor and incohesive relationships with each of the different stakeholders. Moreover, talent development principles between the different stakeholders appeared well-understood overall, although the practical implementation of several of these principles in applied practice did not appear to exist. Results highlight the need for organizational intervention and structural change across the Irish player pathway to maximize long-term player development in the future. Practical implications for the FAI are discussed and recommendations are made to support optimal player development policies moving forward.



#3 A valid and reliable test of technical skill for vision impaired football

Reference: Sci Med Footb. 2022 Feb;6(1):89-97. doi: 10.1080/24733938.2021.1885725. Epub 2021 Feb 22.

Authors: Oliver R Runswick, Alexander Rawlinson, Naomi Datson, Peter M Allen

Summary: The International Paralympic Committee requires international federations to develop and implement sport-specific classification guidelines based on scientific evidence. Performance tests are key to developing new evidence-based criteria in football for athletes with vision impairment (VI). Therefore, the aim of this study was to develop a valid and reliable test of technical performance for VI football. To assure content and face validity, the Vision Impaired Football Skills (VIFS) test was based on recommendations from experienced players and coaches. To test construct validity, we compared 24 sighted football players split into two groups based on highest-level of performance but matched on experience. To test reliability participants completed the VIFS three times on two separate days. Results supported construct validity through detecting differences in performance times between the two groups (p = .004, g = 1.28 95% CI = 0.41 - 2.15). Bias between visits (.54s ± 2.93s; 95% LoA = -5.21- 6.29) and intraclass correlations (.81, 95% CI = .56 - .92) showed between-day agreement and reliability. Within-day reliability was good after a familiarisation trial. Results support the suitability for the VIFS test for classification research. Future work should establish feasibility for players with a VI.



#4 Sport-related concussion practices of medical team staff in elite football in the United Kingdom, a pilot study

Reference: Sci Med Footb. 2022 Feb;6(1):127-135. doi: 10.1080/24733938.2021.1892174. Epub 2021 Feb 28.

Authors: Craig Rosenbloom, Daniel Broman, Wing Chu, Robin Chatterjee, Katrine Okholm Kryger

Summary: The aim was to explore sport-related concussion (SRC) awareness, behaviours, and attitudes of medical team staff working in elite football in the United Kingdom. Including usage and awareness of the FA concussion guidelines, concussion education rates of players and coaching staff, and collection of baseline concussion assessments. 120 responses were gathered. High awareness rates of the FA guidelines were found (97%) with variable rates of player and coaching staff concussion education. Baseline concussion assessments were collected by 78%. Of those, 99% collected SCAT5 with low rates of other neuro-psychometric testing (17%). Confidence of pitch-side SRC recognition was high (93% feeling very confident or confident). Introduction of a 'concussion' substitute was seen as strongly positive for player welfare (85% strongly agreeing or agreeing). Awareness of FA concussion guidelines, and collection of SCAT5 baseline testing was high. Player and coaching staff concussion education rates were low, as was the use of neuro-psychometric testing beyond the use of the SCAT5. There was strong support the introduction of a 'concussion' substitute being a positive thing for player welfare.



#5 Association between match physical activity and neuromuscular characteristics in youth football

Reference: J Sports Med Phys Fitness. 2022 Mar 1. doi: 10.23736/S0022-4707.22.13537-1. Online ahead of print.

Authors: Lorenzo Francini, Carlo Castagna, Andrea Bosio, Darragh Connolly, Massimo Induni, Ferdinando Cereda, Ermanno Rampinini

Summary: The aim of this study was to examine the associations between maximal and submaximal neuromuscular field tests, match physical activity levels and biological maturation in youth football players. Sixty-four football players from under 14 to under 17 age groups were assessed. Players performed a Repeated-Sprint Ability test, Counter Movement Jump, 10-m and 30-m sprint test, as well as an assessment of peripheral muscle function following a multi-stage incremental (i.e. four intensity levels) change of direction test (COD). Knee extensors peak-torque (PTmax) and the decrement of torque values (dec) were considered as COD outcomes. Physical match activities were tracked by GPS technology, while rate of perceived exertion (RPE) was assessed using the CR10 Börg scale. Pearson's correlations (90% confidence interval) were used to examine the relationships. Small associations were found between field tests and match activities. The relationships increased from small to moderate for some tests when match data with RPE>5 were considered. The largest associations were found between distance covered <-2.5m·s-2 and both COD PTmax and dec when RPE>5. The results of the present study provide further evidence of a small-to-moderate association between muscular performance and match work-rate in young football players. Although physical and physiological evaluations fail to precisely estimate the quantity of physical activities performed during matches, it is suggested that they can be utilized to monitor the training effect over time in young football players.



#6 Differences in Older Adults Walking Football Initiation and Maintenance Influences Across Respondent Characteristics: A Cross-Sectional Survey

Reference: J Aging Phys Act. 2022 Feb 26;1-14. doi: 10.1123/japa.2021-0305. Online ahead of print.

Authors: Rachel Cholerton, Joanne Butt, Helen Quirk, Jeff Breckon

Summary: Despite health benefits gained from physical activity and sport participation, older adults are less likely to be active. This study investigates what influences 50- to 75-year-olds (N = 439) to initiate and maintain walking football, across gender, socioeconomic status, number of health conditions, and physical activity level. It also considers relationships between participant characteristics and influences, and intentions to play after a forced break (COVID-19). Results of a U.K. online cross-sectional survey found those with two or more health conditions rated social influences significantly higher in initiation and maintenance than participants with no health conditions. Multiple regression analysis found a positive walking football culture, and perceived use of maintenance resources contributed significantly to intentions to return to play after COVID-19 restrictions eased. Practitioners should consider providing opportunities for social connection, foster a positive walking football culture, and encourage players to utilize maintenance resources (e.g., scheduling sessions) in older adult walking football sessions.



#7 Impact of Anterior Cruciate Ligament Injury on European Professional Soccer Players

Reference: Orthop J Sports Med. 2022 Feb 22;10(2):23259671221076865. doi: 10.1177/23259671221076865. eCollection 2022 Feb.

Authors: Daniele Mazza, Edoardo Viglietta, Edoardo Monaco, Raffaele Iorio, Fabio Marzilli, Giorgio Princi, Carlo Massafra, Andrea Ferretti

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Summary: The impact of anterior cruciate ligament reconstruction (ACLR) on the performance and career of professional soccer players has not been extensively investigated. The aim was to evaluate in professional European soccer players (1) the ACL injury incidence, (2) the return-to-play (RTP) rate and time after ACLR, (3) career survival and athlete performance in the first 3 postoperative seasons after RTP, (4) factors likely related to different outcomes after ACLR, and (5) any related differences between the top 8 European soccer leagues. Included were professional soccer players in the top 8 European Soccer leagues (Serie A [Italy], Premier League [England], Ligue 1 [France], LaLiga [Spain], Bundesliga [Germany], Jupiler Pro League [Belgium], Liga NOS [Portugal], and Premier Liga [Russia]) who sustained an ACL injury during seasons 2014 to 2015, 2015 to 2016, and 2016 to 2017. Data were retrieved from publicly available online sources. Outcomes were evaluated based on player age (<25 years, 25-30 years, and >30 years), position (goalkeeper, defender, midfielder, and forward), affected side (dominant vs nondominant), and league. Overall, 195 players sustained an ACL injury, for a mean annual ACL injury incidence of 1.42%. The RTP rate was 95%, with a mean RTP time of 248 ± 136 days. Within the third postoperative season, 66 players (36%) competed in a lower level national league, and 25 (13.6%) ended their careers; a significant reduction in the mean minutes played per season was found in all 3 postoperative seasons. Player age correlated significantly with reduction in performance or recovery from an ACL injury. No significant correlation was found between postoperative player performance and affected side, position, league, or time to RTP. A substantial ACL injury incidence was found in top European elite soccer players; however, a high RTP rate in a reasonable time was seen after ACLR. Nevertheless, professional soccer players experienced a short-term decline in their performance.



#8 The influence of soccer shoes on plantar distribution in young players in a static condition. A pilot study

Reference: J Sports Med Phys Fitness. 2022 Mar 1. doi: 10.23736/S0022-4707.22.13644-3. Online ahead of print.

Authors: Giuseppe Messina, Francesco Pomara, Luca Petrigna, Maria C Piccione, Silvia Caserta, Marco Petrucci, Antonio Palma, Antonino Bianco

Summary: Injuries are a serious problem in soccer for the player but also for the society. It has been noted most of the injuries occurs during non-contact situations and, the soccer shoes have an important role. Unfortunately, few studies investigated the plantar distribution, argument that could help to deeply understand the causes behind the injuries. The objective was to evaluate the influence of the soccer shoes on plantar distribution in young players in a static condition. Young soccer players (range 11-18) were recruited and performed two tests on a baropodometric platform, one barefoot and one with technical soccer shoes. A student's t-test was performed to evaluate the differences between the conditions. Significative results were between the left plantar surface (p<0.05) and in the total surface anterior (p<0.05) with and without the soccer shoe. Related to the pressure values, soccer shoes resulted higher than barefoot condition. Significativity has been found also between the forefoot and the rearfoot in the left foot, in barefoot condition (p < 0.05). Soccer shoes generally produce a reduction in the contact plantar surface, especially in the anterior zone and the foot load is higher in the forefoot zone.



#9 Effects of Cool-Down Exercise and Cold-Water Immersion Therapy on Basic Fitness and Sport-Specific Skills among Korean College Soccer Players

Reference: Iran J Public Health. 2021 Nov;50(11):2211-2218. doi: 10.18502/ijph.v50i11.7575.

Authors: Yoon-Hyung Lee, Jin-Ho Yoon, Ki-Jae Song, Jae-Keun Oh

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Summary: We aimed to examine the effects of cool-down exercise and cold-water immersion therapy on agility, speed, power, balance, and sport-specific skill performance in college soccer players, and to provide baseline data for the development of effective recovery programs. In August 2020, 21 male college soccer players in Seoul, Korea, were randomly divided into the following groups: control group (CG, n=7), cool-down exercise group (CDG, n=7), and cool-down exercise plus cold-water immersion group (CDCWG, n=7). Agility, speed, power, balance, and sport-specific skill performance were assessed before and after the intervention. No significant differences in Southeast Missouri (SEMO) Agility Test, 20-m sprint test, vertical jump test, or Y-balance test (right) were observed among the groups; however, there was a significant effect of time (P<0.05) and a significant time × group interaction (P<0.05). Significant effects of time (P<0.001), group (P=0.043), and a time × group interaction (P=0.009) were observed in the Y-balance test (left). There were no between-group differences in the 22-m dribble test, shooting test (left), or shooting test (right); however, there were significant effects of time (P<0.05) and significant time × group interactions (P<0.05). No significant effects of group or time × group interactions were observed for the kicking test (left or right); however, there were significant effects of time (P<0.001). Addition of cold-water immersion therapy to a recovery program including cool-down exercise can promote recovery of basic and sport-specific abilities among college soccer players.



#10 Progression to the target vs. regular rules in Soccer small-sided Games

Reference: Sci Med Footb. 2022 Feb;6(1):66-71. doi: 10.1080/24733938.2020.1869811. Epub 2021 Jan 3.

Authors: Gibson Moreira Praça, André Gustavo Pereira Andrade, Sarah da Glória Teles Bredt, Felipe Arruda Moura, Pedro Emilio Drumond Moreira

Summary: This study compared the physical, physiological, and spatiotemporal responses of soccer athletes in small-sided games (SSG) in two experimental conditions: progression to the target rule (PG), in which they should take the ball to the opponent's endline to score points, and SSG with regular rules (RG), in which they should score goals to win the game. Twenty U-20 athletes played both SSG formats. The SSG were played as four 4-minute bouts with four minutes of passive recovery in two consecutive days. Heart rate, physical (distances and accelerations), and positional data (length, width, and spatial exploration) were collected by a 10 hz GPS device and compared between the protocols using a MANOVA with Bonferroni's correction for multiple comparisons. Results showed that the RG condition demanded more spatial exploration eliciting greater occupation of the pitch width. There were higher mean and maximum heart rates and greater low-to-moderate distances and accelerations in the RG, while the PG rule increased the distances covered at the highest speed and acceleration zones. The progression to the target rule should be adopted to emphasize players' ability to use the width during the offensive phase. Additionally, the PG rule should also be used to emphasize the development of speed and acceleration skills.



#11 Lower limbs muscle activation during instep kick in soccer: effects of dominance and ball condition

Reference: Sci Med Footb. 2022 Feb;6(1):40-48. doi: 10.1080/24733938.2021.1884283. Epub 2021 Mar 9.

Authors: Rodrigo Rabello, Filippo Bertozzi, Manuela Galli, Matteo Zago, Chiarella Sforza

Summary: Muscle activation has been studied in soccer players kicking stationary balls with the dominant foot. This study evaluated swinging and support limb muscle activation during the instep kick using different feet and ball approach conditions.Vastus medialis (VM), biceps femoris (BF), gastrocnemius medialis (GM) and tibialis anterior (TA) activations were evaluated during maximal instep kicks with both feet and the ball in five conditions (n = 18): stationary (STAT), approaching anteriorly (ANT), posteriorly (POST), laterally (LAT) and medially (MED). A repeated-measures two-way ANOVA compared activations between feet and ball conditions throughout the kicking (0-100%) and follow-through phases (101-200%). Close to ball contact (81-124%), non-dominant support GM had greater activation than the dominant one. The LAT and MED conditions differed within the cycle in the swinging VM (0-21%; 191-200%), BF (13-70%; 121-161%), GM (22-82%; 121-143%) and TA (0-32%; 55-97%; 186-200%) and in support VM (0-81%), BF (6-24%; 121-161%) and GM (24-87%). Players require greater support GM activation to stabilize the ankle during non-dominant kicks. Muscle activation differences between LAT and MED indicate that the kicking strategies are altered when kicking balls approaching from different directions.



#12 "I Gave Up Football and I Had No Intention of Ever Going Back": Retrospective Experiences of Victims of Bullying in Youth Sport

Reference: Front Psychol. 2022 Feb 15;13:819981. doi: 10.3389/fpsyg.2022.819981. eCollection 2022.

Authors: Xènia Ríos, Carles Ventura, Pau Mateu

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Summary: Bullying is a global issue that, beyond school, is present in different social contexts, such as sport environments. The main objective of this study was to get to know the experiences of victims of bullying in sport throughout their youth sport training. Semi-structured interviews to four Spanish women and seven Spanish men were carried out, within an age range of 17-27 (M age = 21 years, SD = 3.69). The following main themes were established by means of a hierarchical content analysis: (a) "bullying characterization," (b) "dealing with bullying," and (c) "consequences of bullying." The results show the presence of physical, verbal and social bullying in the sport context, with the changing room being the space where this type of behavior is most frequently developed. Most victims show an internal attribution (self-blame) for the bullying event, related to their motor skills and their personal physical and psychological characteristics. Double victimization can be observed, at the sport club and at the educational center. Passive strategies are used to deal with the situation, while little support is shown by sport agents (teammates and coaches). The victims, as a consequence of the bullying experience, suffer from short and long-term negative effects on a psychosocial level. The study highlights the necessity to design and implement programs focused on the prevention, detection and intervention of bullying for sport organizations, bearing in mind all the agents that make them up (coaches, management teams, families, and players). Furthermore, the importance of promoting the creation of safe sport environments, free from any kind of violence, is emphasized.



#13 Interchangeability of player movement variables from different athlete tracking systems in professional soccer

Reference: Sci Med Footb. 2022 Feb;6(1):1-6. doi: 10.1080/24733938.2021.1879393. Epub 2021 Feb 19.

Authors: Susanne Ellens, Daniel Hodges, Sean McCullagh, James J Malone, Matthew C Varley

Summary: This study assessed the interchangeability between 10-Hz multi-GNSS GPS devices (Vector®) and two optical tracking systems (TRACAB® and Second Spectrum®). The agreement between data from the optical tracking systems when processed with manufacturer and GPS-filtered software was also assessed. Thirty players competing in the English Premier League were monitored using three different tracking systems across five matches. To determine the interchangeability between systems, player movement variables including, total distance, high-speed running distance (19.8-25.2 km·h-1), sprinting distance (>25.2 km·h-1), efforts >19.8 km·h-1 and maximal speed were compared. Equations were formed using linear regression and linear mixed-effects models to allow interchangeability of player movement variables between systems. Over half of the variance of most interchangeability equations were explained and associated with very strong positive correlations (r > 0.72). Small to huge differences were found between systems for most player movement variables. Data of optical tracking systems had decreased values in speed variables >19.8 km·h-1 when processed through GPS software. This study provides equations for practitioners to interchange player movement variables between TRACAB, Second Spectrum and Vector GPS systems with reduced error. This will enable practitioners to combine and share data captured with different tracking systems to analyse and improve their training.



#14 Age- and size-corrected kicking speed and accuracy in elite junior soccer players

Reference: Sci Med Footb. 2022 Feb;6(1):29-39. doi: 10.1080/24733938.2021.1899274. Epub 2021 Jul 26.

Authors: Andrew H Hunter, Nicholas M A Smith, Thiago V Camata, Mathew S Crowther, Andrew Mather, Nicolau Melo Souza, Luiz Fernando Ramos-Silva, Nerylson Ferraz Pazetto, Felipe A Moura, Robbie S Wilson

Summary: Kicking powerfully and accurately is essential in soccer, and players who kick proficiently with both feet are highly sought after. Assessing performance in youth players is often confounded by more physically developed players outperforming their smaller peers. To alleviate such bias, we present a testing protocol and normative data developed with an elite Brazilian soccer academy that controls for players' age and size to assess kick performance with both feet. We measured kick speed and kick accuracy of 178 players and recorded their age (10-20 years), height, and mass. Combining age, height, and mass into an age and size index (ASI), we developed equations describing the relationship between ASI and performance. To determine the underlying predictors of performance, we also measured sprint ability and soccer-specific motor control of each foot with ball dribbling tasks. Kicking speed with the dominant foot was predicted by ASI, sprint speed, and motor control of the nondominant foot, while kicking speed with the nondominant foot was predicted by ASI and motor control of the nondominant foot. Kick accuracy with each foot was predicted by ASI and motor control of the corresponding foot. To improve kicking performance, we suggest training programs focus on motor control.



#15 The influence of training and competition on sleep behaviour of soccer referees

Reference: Sci Med Footb. 2022 Feb;6(1):98-104. doi: 10.1080/24733938.2021.1890812. Epub 2021 Feb 26.

Authors: Michele Lastella, Dean J Miller, Grace E Vincent, Nathan Elsworthy, Aaron T Scanlan, Rob Duffield

Summary: The aims of the present study were to (1) quantify sleep behaviours of soccer referees and (2) compare sleep behaviours between nights before training, before matches, and after matches. Fourteen professional soccer referees from the A-League (mean±SD; age 34 ± 4 years; sex: 11 males, 3 females) participated in this observational study. Referees' sleep behaviours were examined using sleep diaries and wrist activity monitors for 31 consecutive nights during the 2018-2019 A-League season. Separate linear mixed models were conducted to assess differences in sleep behaviours between nights before training, before matches, and after matches. On average, referees did not obtain recommended sleep durations across the in-season (mean±SD sleep duration: 6.4 h ± 0.7 h). Referees went to bed later, spent less time in bed, and slept significantly less post-matches compared to pre-training and pre-match nights (p< 0.05). Referees were particularly susceptible to inadequate sleep on nights following training and matches. The findings related to poor sleep behaviours highlight the importance of implementing monitoring systems to understand the sleep behaviours of referees, with further research encouraged to ascertain the efficacy of various sleep hygiene practices to optimise sleep in this population.



#16 Analysis of the Effect of Injuries on Match Performance Variables in Professional Soccer Players: A Retrospective, Experimental Longitudinal Design

Reference: Sports Med Open. 2022 Mar 3;8(1):31. doi: 10.1186/s40798-022-00427-w.

Authors: Javier Raya-González, Juan José Pulido, Marco Beato, José Carlos Ponce-Bordón, Roberto López Del Campo, Ricardo Resta, Tomás García-Calvo

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Summary: Knowing the impact of injuries is essential for their adequate management during reconditioning programs. This study aimed to analyze the changes in match performance parameters in professional soccer players after sustaining an injury, which was defined according to injury severity. Two-hundred and seven injuries related to one hundred and sixty-one professional soccer players from the Spanish LaLiga™ were considered for this study. All the injuries were classified according to their severity as minor (from 4 to 7 missed days), moderate (from 8 to 28 missed days), and major (more than 28 missed days). Through Mediacoach® videotracking system, time and external demand variables were collected and subsequently compared between pre-injury and return to play periods. The analyzed variables were (in m min-1): relative distance covered (RD; total distance covered·min-1), distance covered walking (0-6 km h-1), distance covered jogging (6-12 km h-1), distance covered running (12-18 km h-1), distance covered at intense running (18-21 km h-1), distance covered at high-speed running (21-24 km h-1), and sprinting (> 24 km h-1) distance covered. Significant reductions in playing time after suffering moderate and major injuries were observed. Significant reductions after minor injuries were observed in jogging (> 6 km h-1) and running (6-12 km h-1), while significantly greater distances at intense running (18-21 km h-1) and high-speed running (21-24 km h-1) were covered by players who suffer major injuries. Finally, relevant decreases in the maximum speed achieved after moderate and major injuries were found. In conclusion, this study shows the importance of high loads during reconditioning programs, as well as implementing strategies that allow reaching levels of maximum speed values after the return to play.



#17 Easier in Practice Than in Theory: Experiences of Coaches in Charge of Community-Based Soccer Training for Men with Prostate cancer-A Descriptive Qualitative Study

Reference: Sports Med Open. 2022 Mar 3;8(1):28. doi: 10.1186/s40798-022-00424-z.

Authors: Kickan Roed, Eik Dybboe Bjerre, Julie Midtgaard

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Summary: Evidence suggests that community-based exercise programs and sports participation benefit long-term physical activity adherence and promote health in clinical populations. Recent research shows that community-based soccer can improve mental health and bone health and result in fewer hospital admissions in men with prostate cancer. However, little knowledge exists on what coaches experience, leading to a scarcity of knowledge on how to assist them in promoting and supporting the sustainability of programs. The purpose of this study was to explore the experiences of non-professional soccer coaches in providing community-based soccer training for men with prostate cancer. We interviewed 13 out of 21 eligible non-professional soccer coaches in charge of delivering the Football Club Prostate Community program, which is community-based soccer training for men with prostate cancer at 12 local soccer clubs across Denmark. Qualitative content analysis, as described by Graneheim and Lundman, was applied to analyze the data using NVivo 12 software. We identified the five following overall categories with 10 subcategories on what the coaches experienced: (1) enabling training of a clinical population in a community setting, (2) dedication based on commitment, (3) coaching on the players' terms, (4) navigating the illness, and (5) ensuring sustainability. Collectively, the findings suggest that, while the coaches felt adequately prepared to coach, their coaching role developed and was refined only through interaction with the players, indicating that coaching clinical populations may be easier in practice than in theory and a potentially transformative learning experience. Non-professional soccer coaches in charge of delivering soccer training for men with prostate cancer value being educated about specific illness-related issues. Initial concerns about how to coach a clinical population disappeared once the coaches engaged with the players and developed their own team norms and illness management strategies. They also gained a broader perspective on their own lives, which they valued and would not otherwise have achieved by coaching a healthy population. Our study indicates that sustainable implementation and the program's sustainability can be promoted and supported through additional formal, easily accessible communication with trained health professionals and by networking with peer coaches.



#18 An End-to-End Deep Learning Pipeline for Football Activity Recognition Based on Wearable Acceleration Sensors

Reference: Sensors (Basel). 2022 Feb 10;22(4):1347. doi: 10.3390/s22041347.

Authors: Rafael Cuperman, Kaspar M B Jansen, Michał G Ciszewski

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Summary: Action statistics in sports, such as the number of sprints and jumps, along with the details of the corresponding locomotor actions, are of high interest to coaches and players, as well as medical staff. Current video-based systems have the disadvantage that they are costly and not easily transportable to new locations. In this study, we investigated the possibility to extract these statistics from acceleration sensor data generated by a previously developed sensor garment. We used deep learning-based models to recognize five football-related activities (jogging, sprinting, passing, shooting and jumping) in an accurate, robust, and fast manner. A combination of convolutional (CNN) layers followed by recurrent (bidirectional) LSTM layers achieved up to 98.3% of accuracy. Our results showed that deep learning models performed better in evaluation time and prediction accuracy than traditional machine learning algorithms. In addition to an increase in accuracy, the proposed deep learning architecture showed to be 2.7 to 3.4 times faster in evaluation time than traditional machine learning methods. This demonstrated that deep learning models are accurate as well as time-efficient and are thus highly suitable for cost-effective, fast, and accurate human activity recognition tasks.



#19 Combined Plyometric and Short Sprint Training in U-15 Male Soccer Players: Effects on Measures of Jump, Speed, Change of Direction, Repeated Sprint, and Balance

Reference: Front Physiol. 2022 Feb 18;13:757663. doi: 10.3389/fphys.2022.757663. eCollection 2022.

Authors: Ghaith Aloui, Souhail Hermassi, Thomas Bartels, Lawrence D Hayes, El Ghali Bouhafs, Mohamed Souhaiel Chelly, René Schwesig

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Summary: This study examined the effect of 8 weeks of biweekly combined plyometric and short sprint training into the typical within-season training schedule of youth male soccer players. Participants were allocated at random to an experimental group (EG; n = 17, age: 14.6 ± 0.5 years, body mass: 60.5 ± 7.1 kg, height: 1.64 ± 0.08 m, body fat: 11.3 ± 1.4%) and a control group (CG; n = 17, age: 14.6 ± 0.4 years, body mass: 61.0 ± 3.9 kg, height: 1.67 ± 0.05 m, body fat: 11.8 ± 1.4%). Measures obtained pre- and post-intervention included vertical and horizontal jump performances (i.e., squat jump (SJ), countermovement jump with aimed arms (CMJA), and five-jump test (FJT)) and sprint performances (i.e., 10 and 30 m sprint). In addition, change-of-direction ability (sprint with 90° Turns (S90°) and sprint 9-3-6-3-9 m with backward and forward running (SBF)), repeated shuttle sprint ability (RSSA), and dynamic balance performance (Y balance test) were measured pre- and post-intervention. The EG experienced higher jump (all p < 0.05; d ≥ 0.71), sprint (all p < 0.05; d ≥ 0.64), change-of-direction ability (all p < 0.05; d ≥ 0.66), RSSA (all parameters except the fatigue index p < 0.01; d ≥ 0.71), and dynamic balance (all p ≤ 0.05; d ≥ 0.50) improvement compared to the CG. Adding biweekly combined plyometric and short sprint training to standard training improves the athletic performance of youth male soccer players (under 15 (U15)).



#20 Effects of sodium pyruvate supplementation on repeated sprint exercise performance and recovery in male college soccer players: a randomized controlled trial

Reference: Ann Palliat Med. 2022 Feb;11(2):598-610. doi: 10.21037/apm-21-3862.

Authors: Yan-Ping Yang, Jun-Qiang Qiu, Meng-Yue Wang, Lin Feng, Dan Luo, Rui-Rui Gao, Fang-Qiang Zhou, Kai-Xuan Che

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Summary: Sodium pyruvate (PYR) has been reported to improve aerobic metabolism and attenuate metabolic acidosis. Aerobic capacity and the ability to remove hydrogen ions affect the recovery from repeated high intensity activities. However, the effects of PYR supplementation on repeated sprint exercise (RSE) performance have not been elucidated. This study explored the effects of PYR ingestion on RSE ability and recovery. A total of 14 male soccer athletes (aged 20±2 years) participated in this double-blinded crossover study. The subjects completed two experimental sessions after randomized ingestion of either PYR or the maltodextrin placebo (PLA) for 1 week. At each session, participants completed high-intensity interval exercise (HIIE) and RSE 60 minutes after supplementation. Additionally, acid-base parameters in venous blood, energy system contributions, and power output were assessed. Compared to PLA, PYR supplementation significantly increased the relative peak power output (PPO) of the first (P=0.034) and fifth (P=0.043) sprints, and the relative mean power output (MPO) of the fifth sprint (P=0.026). In addition, the mean PPO (P=0.031) and MPO (P=0.033) of sprints 1-6 were significantly elevated after PYR supplementation. After PYR administration, the phosphagen energy system [adenosine triphosphate (ATP)-phosphocreatine (PCr)] resynthesis of the fourth (P=0.034) and the overall recovery periods during HIIE (P=0.029) were higher than PLA administration. Additionally, the ATP-PCr resynthesis of the first (P=0.033) and fifth (P=0.019) recovery periods, and the mean of the six recovery periods during RSE (P=0.041) were increased in the PYR group compared to the PLA group. Furthermore, participants on the PYR regimen had higher blood pH, HCO3-, and base excess at pre-HIIE, post-HIIE, and pre-RSE (all P<0.05) compared to participants receiving PLA. PYR supplementation enhanced RSE performance, and the improvement may be attributed to accelerated restoration of the acid-base balance and ATP-PCr regeneration.



#21 Strength Level of Professional Elite Soccer Players after the COVID-19 Lockdown Period: A Retrospective Double-Arm Cohort Study

Reference: J Sports Med (Hindawi Publ Corp). 2022 Mar 3;2022:8242210. doi: 10.1155/2022/8242210. eCollection 2022.

Authors: Robson Dias Scoz, Ricardo Lima Burigo, Isabella Christina Ferreira, Luiz Hespanhol, Ana Paula Silveira Ramos, Adriano Schlosser, Jose Joao Baltazar Mendes, Luciano Maia Alves Ferreira, César Ferreira Amorim

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Summary: It is well known that periods of inactivity generate a loss of muscle strength, a fundamental component of sports performance in soccer. However, little information is available on the decrease in strength levels in professional soccer players after the quarantine lockdown that occurred during the COVID-19 pandemic. The aim was to compare the isokinetic peak torque profiles of professional soccer players from different teams before and after the quarantine period generated by COVID-19. A retrospective observational study was performed using data collected from two different professional elite-level soccer teams just before and immediately after the COVID-19 quarantine period. One team gave individual instructions to its players for conditioning maintenance at home during the quarantine period, while the other team used regular video calls to maintain the player's conditioning status on home training. The main outcomes were the mean peak torque of knee extensors and flexors, from concentric and eccentric contractions of each playing position. Analysis. A two-way ANOVA analysis was used to compare peak torque before and after the quarantine period and between both teams' strategies, showing a statistically significant reduction in eccentric knee flexor peak torque from the team that did not have remote monitoring. Remote monitoring programs are recommended so that athletes are less affected by the deleterious effects of confinement.






3-Week passive acclimation to extreme environmental heat increases physical and physiological performance semi-professional footballers

This study aimed to evaluate the influence of passive heat acclimation program among human participants in the physical performance, as well as in several physiological parameters.





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

Foam rolling (FR) has become a popular device for recovery to increase range of motion and decrease pain after sport practice and competition. The aim of this study was to analyze acute effects of FR on blood flow parameters (maximal velocity MVel, maximal volume MVol) measured by ultrasonography in footballers.






Latest research in football - week 8 - 2022

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 Impact of match-related contextual variables on weekly training load in a professional soccer team: a full season study

Reference: Biol Sport. 2022 Jan;39(1):125-134.  doi: 10.5114/biolsport.2021.102927. Epub 2021 Mar 7.

Authors: Jose M Oliva Lozano, Vincenzo Rago, Víctor Fortes, José M Muyor

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Summary: The purpose of this study was to analyse the impact of match-related contextual variables (match location, match outcome and level of the opponent) on the weekly training load in a professional soccer team throughout a full competitive season. Total distance, high-speed running distance (HSRD, > 18 km·h-1), highmetabolic load distance (HMLD, > 25.5 W·kg-1), player load and total number of impacts (above 3 G) were collected from training and match sessions in professional soccer players (n = 25) competing in LaLiga123. Comparisons of external load parameters by each match-related contextual variable were examined using a mixed-effect model. Differences between playing positions were found for total distance (p < 0.05; r = 0.11-0.15), HSRD (p < 0.05; r = 0.13-0.19), HMLD (p < 0.05; r = 0.12-0.19), player load (p < 0.05; r = 0.11-0.19) and impacts (p < 0.05; r = 0.15-0.26). However, no significant interaction was observed between match-related contextual variables and playing position for any variable (p > 0.05). In addition, a significant impact of match outcome (p < 0.05; r = 0.11-0.15), opponent level (p < 0.05; r = 0.11-0.17) and match location (p < 0.05; r = 0.14-0.20) on the weekly training load (before and after the match) was observed. In conclusion, match-related contextual variables seem to slightly affect weekly external training load. Thus, coaching and medical departments could consider the influence of these contextual variables when prescribing the training load relative to the match demands.



#2 Recovery following the extra-time period of soccer: practitioner perspectives and applied practices

Reference: Biol Sport. 2022 Jan;39(1):171-179. doi: 10.5114/biolsport.2022.104066. Epub 2021 Mar 11.

Authors: Adam Field, Liam David Corr, Chris James Thompson, Jean Carlos Gonzalez Lucena, Hugo Sarmento, Robert Joseph Naughton, Thomas Edward Brownlee, Matthew Haines, Richard Michael Page, Liam David Harper

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Summary: Research has demonstrated that the extra-time (ET) period of soccer negatively impacts recovery. However, it is not known to what extent recovery practices are being adapted by practitioners following ET and where gaps exist between research and practice. Therefore, this study explored soccer practitioner perceptions of recovery practices following ET matches. A total of 72 practitioners from across different levels of soccer and several countries completed a bespoke online survey. Inductive content analysis of the responses identified five higher-order themes: 'conditioning', 'player monitoring', 'recovery practices', 'training', and 'future research directions'. Mixed responses were received in relation to whether practitioners condition players in preparation for ET, though 72% allowed players to return to training based on fatigue markers following this additional 30-min period. Sixty-three (88%) practitioners believed that ET delays the time-course of recovery, with 82% highlighting that practices should be adapted following ET compared with a typical 90-min match. Forty-nine practitioners (68%) reduce training loads and intensities for up to 48 hr post ET matches, though training mostly recommences as 'normal' at 72 hr. Sixty-three (88%) practitioners believed that more research should be conducted on recovery following ET, with 'tracking players physiological and physical responses', 'nutritional interventions to accelerate recovery' and 'changes in acute injury-risk' being the three areas of research that practitioners ranked as most important. These data suggest practitioners and coaches adjust recovery practices following ET matches compared to 90 min. Further research on the efficacy of recovery strategies following ET matches is required to inform applied practice.



#3 DNN-based multi-output model for predicting soccer team tactics

Reference: PeerJ Comput Sci. 2022 Jan 20;8:e853. doi: 10.7717/peerj-cs.853. eCollection 2022.

Authors: Geon Ju Lee, Jason J Jung

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Summary: In modern sports, strategy and tactics are important in determining the game outcome. However, many coaches still base their game tactics on experience and intuition. The aim of this study is to predict tactics such as formations, game styles, and game outcome based on soccer dataset. In this paper, we propose to use Deep Neural Networks (DNN) based on Multi-Layer Perceptron (MLP) and feature engineering to predict the soccer tactics of teams. Previous works adopt simple machine learning techniques, such as Support Vector Machine (SVM) and decision tree, to analyze soccer dataset. However, these often have limitations in predicting tactics using soccer dataset. In this study, we use feature selection, clustering techniques for the segmented positions and Multi-Output model for Soccer (MOS) based on DNN, wide inputs and residual connections. Feature selection selects important features among features of soccer player dataset. Each position is segmented by applying clustering to the selected features. The segmented positions and game appearance dataset are used as training dataset for the proposed model. Our model predicts the core of soccer tactics: formation, game style and game outcome. And, we use wide inputs and embedding layers to learn sparse, specific rules of soccer dataset, and use residual connections to learn additional information. MLP layers help the model to generalize features of soccer dataset. Experimental results demonstrate the superiority of the proposed model, which obtain significant improvements comparing to baseline models.



#4 The Role of Crowd Support on Home Advantage during COVID-19 Restrictions on Italian Football Competitions. Comparison between 2018-19 and 2020-21 Seasons of the Italian Serie A and Serie B Championships

Reference: Sports (Basel). 2022 Jan 30;10(2):17. doi: 10.3390/sports10020017.

Authors: Matteo Vandoni, Ottavia E Ferraro, Alessandro Gatti, Luca Marin, Matteo Giuriato, Dario Silvestri, Nicola Lovecchio, Mariangela V Puci, Vittoria Carnevale Pellino

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Summary: The home advantage (HA) affects football competitions, especially due to the presence of crowd support. Even though several studies demonstrated that HA (which is influenced by the crowd) decreased in recent years, the empty stadia caused by COVID-19 restrictions offered unique situations to explore and quantify HA. For this reason, we aimed to assess HA in two seasons of the major Italian Championships. We conducted an observational study with the data from the last three seasons of the Italian football championship A-B series, analyzing a total of 2.964 individual game scores. To quantify the HA, the number of points won at home was calculated as a percentage of the total number of points won, home and away. In every season and for every team classification, HA was found (scored points > 50% in home matches). We reported a difference in HA median score for Serie B. Additionally, a difference was found in Serie A for middle-ranking HA median scores in the two seasons compared (p-value = 0.017), which was similarly found in Serie B (p-value = 0.009). The number of penalties was lower in the season with a crowd compared to one without a crowd (p = 0.001). The HA did not disappear in empty stadiums, so there must be other contributing factors. Additionally, we found that the referees were biased by the presence of the crowd in favor of the home teams, and this result could be considered by the football association during referees' training and formation.



#5 Assessing Omega-3 Intake in Sport: Brief Food Frequency Questionnaire is Associated with Omega-3 Index in Collegiate Women Soccer Players

Reference: J Athl Train. 2022 Feb 23. doi: 10.4085/1062-6050-0549.21. Online ahead of print.

Authors: Macy Essman, Danielle Christifano, Debra K Sullivan, Prabhakar Chalise, Aaron Carbuhn

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Summary: Omega-3 fatty acids modulate inflammatory processes and are considered beneficial for sport populations highlighting a need to practically assess omega-3 intake. Food frequency questionnaires (FFQ) are inexpensive, non-invasive, tools aimed to evaluate nutrient intakes like omega-3 fatty acids. A tailored, brief FFQ for estimating omega-3 intake has been previously reported in healthy adults to be associated with erythrocyte omega-3 fatty acid levels, a biomarker for omega-3 tissue status and indicative of intake. However, the association between a brief omega-3 FFQ with respective erythrocyte levels, particularly Omega-3 Index has yet to be explored in a sport population. The aim was to examine the association between omega-3 intake using a brief FFQ and Omega-3 Index (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and EPA+DHA) in collegiate women soccer players. Thirty-one NCAA Division I collegiate women soccer players participated in this study. The brief omega-3 FFQ assessed dietary omega-3 intake: DHA, EPA. OmegaQuant blood test measured erythrocyte omega-3 fatty acids (EPA, DHA) and Omega-3 Index (EPA+DHA) levels. Brief FFQ intake of EPA, DHA, and EPA+DHA were positively correlated with erythrocyte EPA (r = 0.48, p = 0.007), DHA (r = 0.73, p < 0.001), and Omega-3 Index (r = 0.73, p < 0.001). In a sample of collegiate women soccer players, the brief omega-3 FFQ is correlated with erythrocyte omega-3 fatty acid levels and may be a practical tool for health practitioners in assessing omega-3 intake within this collegiate sport population.



#6 Relationships of Final Velocity at 30-15 Intermittent Fitness Test and Anaerobic Speed Reserve with Body Composition, Sprinting, Change-of-Direction and Vertical Jumping Performances: A Cross-Sectional Study in Youth Soccer Players

Reference: Biology (Basel). 2022 Jan 27;11(2):197. doi: 10.3390/biology11020197.

Authors: Ana Filipa Silva, Sumer Alvurdu, Zeki Akyildiz, Filipe Manuel Clemente

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Summary: This study aimed to determine the relationships of locomotor profile (combination of a player's maximal oxygen uptake and running economy)-measured by the final velocity attained at 30-15 Intermittent Fitness Test (VIFT) and the anaerobic speed reserve (ASR)-with the body composition, countermovement jump (CMJ), sprinting performances, and change-of-direction (COD) ability of youth soccer players. A cross-sectional study design was implemented. A total of 124 youth soccer players from different age groups (15, 16, 17, 18, and 19 years old) were voluntarily recruited. ASR was determined based on the difference between maximal sprint speed (MSS) and VIFT. Players were tested for the following measures: (i) body composition (body mass and body fat percentage); (ii) CMJ (height of jump); (iii) sprinting time measured at 5, 10, 15, 20, 25, and 30 m; (iv) MSS measured in the best split time (5 m) over the 30 m test; (v) COD ability (time, asymmetry index); and (vi) final velocity at 30-15 IFT (VIFT). A Pearson product-moment correlation test was used to examine the relationships. Height and body mass exhibited large correlations with VIFT (r = 0.835 and r = 0.699, respectively) and small correlations with ASR (r = 0.177 and r = 0.256, respectively). The CMJ was largely correlated with VIFT (r = 0.631 to r = 0.650) while presenting small correlations with ASR (r = 0.227 to r = 0.232). Both VIFT and ASR had moderate (r = 0.3 to r = 0.5) correlations with sprinting time at different distances and very large correlations with MSS (r = 0.797 to r = 0.866). The COD time was largely correlated with VIFT (r = 0.765 and r = 0.775) while exhibiting small-to-moderate correlations with ASR (r = -0.279 and r = -0.301). In conclusion, it was found that locomotor performance at 30-15 VIFT presents high levels of correlation with anthropometry and physical fitness; ASR also presents correlations with these variables, but they are smaller. This suggest that ASR is an independent variable that should be considered for inclusion in information for characterizing players' capacities.



#7 Mental health problems and risk assessment in football players infected with SARS-CoV-2: a cross-sectional study

Reference: J Sports Med Phys Fitness. 2022 Feb 21. doi: 10.23736/S0022-4707.22.13493-6. Online ahead of print.

Authors: Yavuz Lima, Nevzad Denerel, Sergen Devran, Mehmet G Günver, Bülent Bayraktar, Simon Rice

Summary: Although the negative psychological impact of the pandemic on athletes is well known, there is currently insufficient evidence regarding mental health (MH) problems among athletes infected with SARS-CoV-2. The aim of the present study was to evaluate the association between MH problems, demographics, and SARSCoV-2 related variables in football players infected with SARS-CoV-2. An online survey included demographic questions, SARS-CoV-2 related questions, the Athlete Psychological Strain Questionnaire, and the Depression Anxiety Stress Scales-21 was distributed to male and female professional football players aged between 18-38 and infected with SARS CoV-2. A total of 261 football players participated in the study. The odds of athlete-specific distress in lowerlevel football players were up to 5.9 times more than those competing at the highest level (OR=3.06-5.93, 95% CI=1.27-14.43, p<0.01). The odds of depression and stress in lower-level football players were up to 6.7 times more than those competing at the highest level (both OR=3.70-6.77, 95% CI=1.18-19.20, p<0.01). In players who reported sleep problems, there was increased risk of athlete-specific distress (OR=2.43, 95% CI=1.31-4.52, p<0.01), depression (OR=3.71, 95% CI=1.98-6.95, p<0.01), anxiety (OR=2.93, 95% CI=1.62-5.28, p<0.01), and stress (OR=.7,08 95% CI=3.52-14.02, p<0.01). There was increased risk of depression and stress in female players (OR=5.78, 95% CI=2.03-16.4, p<0.01; OR=4.91, 95% CI=1.57-15.4, p<0.01; respectively). The odds of anxiety in players who reported severe SARS-C0V-2 symptoms were up to 2.2 times more than asymptomatic players (OR=2.28, 95% CI=1.08-4.82, p=0.03). MH problems in football players infected with SARS-CoV-2 were associated with female gender, participation in football in the lower-level, performance concerns, and sleep problems. MH assessment is indicated in athletes infected with SARS-CoV-2 to support detection, and appropriate and timely intervention.



#8 Most amateur football teams do not implement essential components of neuromuscular training to prevent anterior cruciate ligament injuries and lateral ankle sprains

Reference: Knee Surg Sports Traumatol Arthrosc. 2022 Feb 21. doi: 10.1007/s00167-022-06878-8. 

Authors: Nikki Rommers, Roland Rössler, Bruno Tassignon, Jo Verschueren, Roel De Ridder, Nicky van Melick, Lieselot Longé, Tim Hendrikx, Peter Vaes, David Beckwée, Christophe Eechaute

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Summary: Neuromuscular training (NMT) is effective at reducing football injuries. The purpose of this study was to document the use of NMT to prevent anterior cruciate ligament injuries and lateral ankle sprains in adult amateur football and to identify barriers for using NMT. A preseason and in-season online survey was completed by players and coaches of 164 football teams. The survey contained questions concerning injury history, type and frequency of NMT, and barriers when NMT was not used. A total of 2013 players (40% female) and 180 coaches (10% female) completed the preseason survey, whereas 1253 players and 140 coaches completed the in-season survey. Thirty-four percent (preseason) to 21% (in-season) of players used NMT, but only 8% (preseason) to 5% (in-season) performed adequate NMT (i.e. both balance and plyometric exercises, at least twice per week). In the subpopulation of players with an injury history, 12% (preseason) and 7% (in-season) performed adequate NMT. With respect to the coaches, only 5% (preseason) and 2% (in-season) implemented adequate NMT. Most important barriers for using NMT for both players and coaches were a lack of belief in its effectiveness, a lack of knowledge, the belief that stretching is sufficient, and not feeling the need for it. Most amateur football teams do not implement essential components of NMT. The results highlight the urgent need for developing strategies to enhance the adequate use of NMT in amateur football.



#9 Influence of the Weekly and Match-play Load on Muscle Injury in Professional Football Players

Reference: Int J Sports Med. 2022 Feb 21. doi: 10.1055/a-1533-2110. Online ahead of print.

Authors: Víctor Moreno-Perez, Miguel Angel Campos-Vazquez, Javier Toscano, Victor Javier Sotos-Martinez, Roberto López-Del Campo, Ricardo Resta, Juan Del Coso

Summary: The aim of this investigation was to examine the impact of the weekly training load and the match running patterns prior to a muscle injury as potential risk factors of muscle injury in professional football players. Forty male professional football players participated in the investigation. Running distances at different intensities 5 min and 15 min prior to the injury were compared to the same time-points in official matches of the same player with no injury events. Furthermore, the cummulative session rating of perceived exertion (sRPE) and training load of the week prior to the injury were compared to a control week (mean value of training weeks without injury). Nineteen players suffered 31 non-contact muscle injuries during matches. The distance covered at 21-24 km/h (p<0.001; effect size (ES)=0.62) and at>24 km/h (p=0.004; ES=0.51) over the 5-min period prior to the injury was greater than in matches without injury. The cumulative sRPE (p=0.014; ES=1.33) and training volume (p=0.002; ES=2.45) in the week prior to the injury was higher than in a control week. The current data suggest that the combination of a training week with a high load and a short period of high intensity running during the match might increase the risk of muscle injury in professional footballers.



#10 Lower Limb Injuries in an English Professional Football Club: Injury Analysis and Recommendations for Prevention

Reference: Phys Sportsmed. 2022 Feb 22. doi: 10.1080/00913847.2022.2045176. Online ahead of print.

Authors: Mohamad Y Fares, Katy Stewart, Michael McBride, John Maclean

Summary: Lower limb injuries constitute a problem in the sport of football. Our aim is to explore patterns and trends of lower limb injuries in an English professional football club. This is a descriptive epidemiological study. Reports provided by the club's physical therapy team were screened for injuries among professional football players sustained over four seasons, from 2015/2016 to 2018/2019. Data included setting of injury (in-match or training), anatomical location of injury, type of injury, number of days off and month of injury. A total of 296 lower limb injuries were recorded in our study, with a rate of 11.14 per 1000 football hours. Injury rate during games was 51.38 per 1000 football hours, significantly greater than that during training at 3.81 per 1000 football hours (p=0.021). The thigh was significantly the most commonly injured location at 4.67 per 1000 football hours (p<0.001). Grade I tears were the most common injury type at 1.73 per 1000 football hours, significantly greater than grade III tears (p=0.027), contusions (p=0.043), fractures (p=0.02), and lacerations (p=0.019). Injury rates were found to be greatest during preseason and declined as season progressed. On average, an injury sidelined the affected footballer for a total of 20 days. Lower limb injuries were more common during matches than training. The thigh is the most common injury location, and grade I muscle tear was the most common type of injury. Injury rates were higher early on in the season. Potential prevention strategies include spacing out competition, adopting training and exercise regimens that cater for recovery, and increasing research regarding injury mechanisms.



#11 A video-based analysis of situations bearing the risk of respiratory disease transmission during football matches

Reference: Sci Rep. 2022 Feb 22;12(1):3034. doi: 10.1038/s41598-022-07121-7.

Authors: Oliver Faude, Simon Müller, Sebastian Schreiber, Jonas Müller, Lukas Nebiker, Florian Beaudouin, Tim Meyer, Florian Egger

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Summary: We aimed to analyze the number and type of contacts involving the risk of respiratory disease transmission during football match play. We analysed 50 matches from different playing levels. Two reviewers evaluated the contacts of all players in each match. We focused on between-player contacts, crowding, actions with potentially increased aerosol and droplet production and within-player hand-to-head contacts. We categorized the duels with direct contact into frontal and other ones and measured contact duration. The number of between-player contacts were similar between playing levels (median 28.3 [IQR 22.6, 33] contacts per player-hour). Frontal contacts summed up to 8% of all contacts. Contacts involving the head occurred less than once per player and match with none lasting longer than 3 s. Crowding included between two and six players and the duration was mostly less than 10 s. Aerosol and droplet producing activities were three to four times more frequent in adult compared to youth players. Our results suggest that the risk of respiratory pathogen transmission is low during football matches. This conclusion is based on the finding that most close contact situations are of short duration and on the fact that it is an outdoor sport.



#12 The effects of individual and collective variability on youth players' movement behaviours during football small-sided games

Reference: Res Sports Med. 2022 Feb 24;1-16. doi: 10.1080/15438627.2022.2042293. Online ahead of print.

Authors: Diogo Coutinho, Bruno Gonçalves, Sara Santos, Bruno Travassos, Wolfgang Schöllhorn, Jaime Sampaio

Summary: This study aimed to identify the effects of playing with additional individual (IND), collective (COL) or individual-collective (MIX) variability on youth football players' performance during small-sided games. Twelve youth football players (U17, age = 16.1 ± 0.9 years) played a goalkeeper (Gk) + 6 outfield players a-side (Gk+6vs6+Gk) under four conditions: (i) playing in the 1:2:3:1 formation without any other rule (control condition, CTR); (ii) 1:2:3:1 formation with additional body restrictions changing each minute (individual condition, IND); (iii) using different tactical formations modified each minute (collective condition, COL; (iv) using different tactical formations and body restrictions varied each minute (individual-collective condition, MIX). Generally, there were similar behaviours across conditions, especially for the CTR and the MIX. Nevertheless, the CTR condition presented moderate higher values in the lateral direction (p ≤ .05), while also higher longitudinal synchronization compared to the IND (p ≤ .05). The COL condition presented higher spatial exploration (p ≤ .05), which may justify the higher values for distance covered while running and sprinting (p ≤ .05). Overall, coaches may use the IND condition to refine players' technical actions, while the COL condition to develop players' ability to perform in different playing positions and team structures.



#13 Postmatch Recovery Practices Carried Out in Professional Football: A Survey of 56 Portuguese Professional Football Teams

Reference: Int J Sports Physiol Perform. 2022 Feb 24;1-7. doi: 10.1123/ijspp.2021-0343. Online ahead of print.

Authors: Sérgio M Querido, João Brito, Pedro Figueiredo, Filomena Carnide, João R Vaz, Sandro R Freitas

Summary: In football (ie, soccer), the effectiveness of recovery practices is critical to maintain high levels of performance, prevent residual fatigue, and reduce injury risk. However, the recovery methods that professional football teams put in place up to 72 hours postmatch are widely unknown. This study aimed to characterize the postmatch recovery practices in Portuguese football teams in different postmatch periods and match locations. Portuguese football teams (total, N = 56; male: first league [n = 17], second league [n = 16], under-23 league [n = 12]; female: first league, n = 11) participated in the study. The practitioners in charge of recovery strategies in each team filled out the online questionnaire in the middle of the 2019-20 season. The questions focused on the type of recovery methods to be used at different times after home and away matches. After home matches, stretching, electrostimulation, active recovery, and massage were used with higher frequency (P < .017) in later postmatch periods (ie, 12-24, and 24-72 h) compared with immediately postmatch. After away matches, several differences were found (P < .017) for the stretching, electrostimulation, active recovery, cold-water immersion, massage, nutrition, and sleep between postmatch periods. Regarding match location, stretching (r = .19), active recovery (r = .39), cold-water immersion (r = .46), and massage (r = .29) showed a higher frequency of use immediately after home matches. Conversely, the use of compression garments (r = .27) was higher immediately after away matches. It was concluded that in professional football, recovery methods are not applied uniformly along postmatch periods and differ depending on the match location.



#14 Predictors of selection into an elite level youth football academy: A longitudinal study

Reference: J Sports Sci. 2022 Feb 25;1-16. doi: 10.1080/02640414.2022.2044128. Online ahead of print.

Authors: Daniel Fortin-Guichard, Inge Huberts, Jurrit Sanders, Ruud van Elk, David L Mann, Geert J P Savelsbergh

Summary: Talent identification in football is complex. Research regarding talent indicators that predict selection into professional academies is increasingly multi-disciplinary, though is typically cross-sectional, failing to consider whether the rate of change of those indicators influences selection. The aim of this study was to determine if longitudinal changes in talent indicators are associated with selection into a professional football academy. A total of 110 Dutch male football players (aged 8-12) playing in a youth development programme of a professional club were included in the study. Players were assessed regularly on their anthropometry, physical fitness, gross motor coordination, technical ability, and psychosocial capacities over four years. A subset of players was then selected into the academy. Cross-sectional and longitudinal analyses revealed the indicators that best predicted selection. The best indicator was the 30 m sprint speed, with prediction not improving when including other predictors or their rate of change. The individuals that the club ultimately selected at age 12 could have been predicted well above chance levels using the sprint speeds at age nine or ten. The relative consistency of the rate of improvement in indicators across participants meant that the rate at which they developed played little role in selections.



#15 Semi-quantitative magnetic resonance imaging scoring of the knee detects previous injuries in professional soccer players

Reference: Knee Surg Sports Traumatol Arthrosc. 2022 Feb 19. doi: 10.1007/s00167-022-06897-5.

Authors: Goetz Hannes Welsch, Anna-Maria Behr, Karl-Heinz Frosch, Enver Tahir, Milena Pachowsky, Frank Oliver Henes, Gerhard Adam, Kai-Jonathan Maas, Malte Lennart Warncke

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Summary: The medical examination ("medical") is an important procedure in professional soccer since it has high economic relevance. In addition to clinical tests, magnetic resonance imaging (MRI) is used to assess joint health. In the present study, the reliability of semiquantitative knee MRI during the "medical" in professional soccer was tested, and its relationship with clinical data and days missed due to knee injury was observed. In this cross-sectional study, between 2012 and 2019, 69 newly assigned players (age 18-35 years) from a professional soccer club underwent MRI (3.0 T) of both knee joints during their "medical". Reported knee injuries and previously missed days due to injury were obtained from player anamnesis and the "" database. Based on the established "Whole-Organ Magnetic Resonance Imaging Score" (WORMS), two independent radiologists graded the MRI results. Further evaluation was based on the mean score of both knees. The mean WORMS for all subjects was 13.9 (median 10.5, range 0-61). Players with previous injuries had significantly higher scores than players without reported injuries (22.1 ± 17.7 vs. 8.9 ± 4.4, p < 0.002). Three outliers (previously undetected injuries) in the group of players without reported injuries were observed (6.7%). The WORMS was significantly correlated with a prior knee injury (r: 0.424, p < 0.0001) and days missed due to injury (r: 0.489, p < 0.001). Age was correlated with the WORMS (r: 0.386, p < 0.001). In a linear regression model, prior injury was the only significant predictor of a high WORMS (p = 0.001). The WORMS was a significant predictor of days missed due to injury (p < 0.0002) and prior injury (sensitivity: 78%, specificity: 91%, p = 0.006). The intraclass correlation coefficient was excellent (0.89). Semiquantitative knee MRI for WORMS determination during the soccer "medical" is a robust and reliable method. Prior injury, even in players without documented trauma, was detected by the WORMS, and previously missed days due to injury were correlated with the semiquantitative MR knee score.



#16 Age-Related Electrocardiographic Characteristics of Male Junior Soccer Athletes

Reference: Front Cardiovasc Med. 2022 Feb 3;8:784170. doi: 10.3389/fcvm.2021.784170. eCollection 2021.

Authors: Elena Cavarretta, Luigi Sciarra, Giuseppe Biondi-Zoccai, Francesco Maffessanti, Antonia Nigro, Fabio Sperandii, Emanuele Guerra, Federico Quaranta, Chiara Fossati, Mariangela Peruzzi, Annachiara Pingitore, Dimitrios M Stasinopoulos, Robert A Rigby, Rachele Adorisio, Andrea Saglietto, Leonardo Calò, Giacomo Frati, Fabio Pigozzi

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Summary: Very limited data exist on normal age-related ECG variations in adolescents and no data have been published regarding the ECG anomalies induced by intensive training, which are relevant in pre-participation screening for sudden cardiac death prevention in the adolescent athletic population. The purpose of this study was to establish normal age-related electrocardiographic measurements (P wave duration, PR interval, QRS duration, QT, and QTc interval) grouped according to 2-year age intervals. A total of 2,151 consecutive healthy adolescent Soccer athletes (trained for a mean of 7.2 ± 1.1 h per week, 100% male Caucasians, mean age 12.4 ± 1.4 years, range 7-18) underwent pre-participation screening, which included ECG and transthoracic echocardiography in a single referral center. Their heart rate progressively slowed as age increased (p < 0.001, ranging from 80.8 ± 13.2 to 59.5 ± 10.2 bpm), as expected. The P wave, PR interval, and QRS duration significantly increased in older age classes (p = 0.019, p = 0.001, and p < 0.001, respectively), and after Bonferroni's correction, the difference remained significant in all age classes for QRS duration. The QTc interval diminished progressively with increasing age (p = 0.003) while the QT interval increased progressively (p < 0.001). Significant variations in the normal ECG characteristics of young athletes exist between different age groups related to increasing age and training burden, thus, age-specific reference values could be adopted, as already done for echocardiographic measurements, and may help to further discriminate potentially pathologic conditions.



#17 The effects of repeated sprint training with vs. without change of direction on measures of physical fitness in youth male soccer players

Reference: J Sports Med Phys Fitness. 2022 Feb 21. doi: 10.23736/S0022-4707.22.13521-8. Online ahead of print.

Authors: Yassine Negra, Senda Sammoud, Rodrigo Ramirez-Campillo, Raja Bouguezzi, Jason Morán, Helmi Chaabene

Summary: Fitness characteristics such as linear sprinting, repeated sprint ability, and change of direction (CoD) are important for male youth soccer players to maximize training safety and physical performance. We aimed to compare the effects of a 9-week repeated sprint training (RST) program, with and without change of direction (CoD) movements, on repeated sprint ability (RSA total time [RSAtotal], RSA best time [RSAbest]), CoD speed (505 CoD test), linear sprint speed (10-m and 20-m linear sprint), and aerobic endurance (AE; Yo-Yo intermittent endurance test level 1) in male youth soccer players. During the in-season period, 20 soccer players were randomly assigned to a RST with CoD (RSTCoD) group (n = 10, age = 15.4±0.4 years) or a repeated linear sprint training group (n = 10, age = 15.6±0.3 years). Both training groups completed approximately two 15 minutes RST sessions per week, with the only difference between training programmes being the inclusion of one CoD movement during sprint repetitions for the RSTCoD group. The two-way ANOVA with repeated measures revealed a significant, moderate effect of time for RSAbest and RSAtotal (effect size [d] = 0.69 and 0.67, respectively). Likewise, significant, moderate-to-large effects of time were found for CoD (d=0.83), 10-m and 20-m sprint (d=0.68 and 0.67, respectively), and AE (d=0.66). No significant group × time interactions were observed for any measure of physical fitness (d=0.00 to 0.16). RST with and without CoD movements is equally effective in improving RSA total and best time, CoD speed, linear sprint speed, and AE in youth male soccer players.



#18 The effects of repeated sprint training with vs. without change of direction on measures of physical fitness in youth male soccer players

Reference: J Sports Med Phys Fitness. 2022 Feb 21. doi: 10.23736/S0022-4707.22.13521-8. Online ahead of print.

Authors: Yassine Negra, Senda Sammoud, Rodrigo Ramirez-Campillo, Raja Bouguezzi, Jason Morán, Helmi Chaabene

Summary: Fitness characteristics such as linear sprinting, repeated sprint ability, and change of direction (CoD) are important for male youth soccer players to maximize training safety and physical performance. We aimed to compare the effects of a 9-week repeated sprint training (RST) program, with and without change of direction (CoD) movements, on repeated sprint ability (RSA total time [RSAtotal], RSA best time [RSAbest]), CoD speed (505 CoD test), linear sprint speed (10-m and 20-m linear sprint), and aerobic endurance (AE; Yo-Yo intermittent endurance test level 1) in male youth soccer players. During the in-season period, 20 soccer players were randomly assigned to a RST with CoD (RSTCoD) group (n = 10, age = 15.4±0.4 years) or a repeated linear sprint training group (n = 10, age = 15.6±0.3 years). Both training groups completed approximately two 15 minutes RST sessions per week, with the only difference between training programmes being the inclusion of one CoD movement during sprint repetitions for the RSTCoD group. The two-way ANOVA with repeated measures revealed a significant, moderate effect of time for RSAbest and RSAtotal (effect size [d] = 0.69 and 0.67, respectively). Likewise, significant, moderate-to-large effects of time were found for CoD (d=0.83), 10-m and 20-m sprint (d=0.68 and 0.67, respectively), and AE (d=0.66). No significant group × time interactions were observed for any measure of physical fitness (d=0.00 to 0.16). RST with and without CoD movements is equally effective in improving RSA total and best time, CoD speed, linear sprint speed, and AE in youth male soccer players.



#19 Coaches' Criteria for Talent Identification of Youth Male Soccer Players

Reference: Sports (Basel). 2022 Jan 18;10(2):14. doi: 10.3390/sports10020014.

Authors: Jan Fuhre, Arild Øygard, Stig Arve Sæther

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Summary: The main aim of this study was to examine which criteria coaches considered in the talent identification of youth male soccer players aged 13-16. The second aim was to describe how the coaches considered these criteria when identifying players for their club or regional teams and how these criteria take the impact of the relative age effect into consideration. We conducted qualitative, semi-structured interviews with six male coaches from a professional club academy or a regional team within the Norwegian Football Federation. In line with earlier research, the results showed that the coaches considered the technical, tactical, and mental factors as the most important in talent identification. Further in line with earlier research, they considered that the physiological and sociological factors were of secondary importance, while anthropometric measures were considered the least important. Regarding the relative age effect, the coaches were aware of the effect and its consequences, while few of them had ways to reduce the effect and its impact on their talent identification process. Even so, the coaches highlighted the importance of considering a holistic approach to talent identification. The results show similarities with earlier research, but there is still a need for more longitudinal studies that investigate criteria for talent identification in youth football.



#20 The Effects of Proprioceptive Training on Balance, Strength, Agility and Dribbling in Adolescent Male Soccer Players

Reference: Int J Environ Res Public Health. 2022 Feb 11;19(4):2028. doi: 10.3390/ijerph19042028.

Authors: Diana Victoria Gidu, Dana Badau, Marius Stoica, Adrian Aron, George Focan, Dan Monea, Alina Mihaela Stoica, Nicoleta Daniela Calota

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Summary: The aim of the study was to determine the effects of proprioceptive training (PT) on balance, strength, agility and dribbling in adolescent soccer players. In this research, we included an experimental (n = 48) and a control (n = 48) group (CG) with 14 years old players. The experimental group (EG) participated in an 8 week PT program, with four 30 min sessions per week. The experimental program included 12 bosu ball exercises to improve balance, stability and strength which were grouped into two subprograms: the first not using the soccer ball, the second subprogram using the soccer ball. The subprograms were implemented alternately during 16 proprioceptive training sessions, on two types of firm and foam surfaces. Pre- and post-tests included the static balance [Balance Error Scoring System (BESS)], vertical, horizontal, and lateral jumping, and the completion of agility ("arrowhead") and dribbling ("short dribbling") tests. Regarding the total BESS score, the CG has demonstrated progress between the pre- and the post-test, with 0.780 ± 0.895, fewer errors, while the EG had 5.828 ± 1.017 fewer errors. The difference between the two groups was of 5.148 fewer errors for the EG who had practiced the proposed program of proprioceptive training. The highest difference registered between the pre- and the post-test was at the test "single-leg forward jump with the right leg", with a result of 1.083 ± 0.459 cm for the CG and of 3.916 ± 0. 761 cm for the EG. Through the analysis of average differences between the pre- and the post-tests, we observe that, regarding the "Agility right side test", the EG has progressed with 0.382 s in comparison with the CG; regarding the "Agility left side test", the EG has progressed with 0.233 s compared to the CG; regarding the "Agility right and left side test", the EG has progressed with 0.196 s compared to the CG; in the "Short dribbling test", the EG has progressed with 0.174 s compared to the CG. The highest progress was made at the "Agility right side test", of 0.402 s for the EG, while the CG registered 0.120 s. Most of the results in all tests for both experimental groups show an effect size ranging from small to medium. The progress made by the experimental group in all tests was statistically significant, while in the control group the progress was mostly statistically insignificant for p < 0.05. The results suggest that a PT program performed at about 14 years of age could be successfully implemented in the training regime of soccer players to improve components of fitness along with dribbling skills. The results of the study revealed that sports training on the foam surfaces determined a superior progress of the development of proprioception compared to the increased training on the firm surfaces.






Association between offensive and defensive playing style variables and ranking position in a national football league

Association between offensive and defensive playing style variables and ranking position in a national football league.





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

The aims of the study were to describe the perceived load, fatigue and recovery profiles during congested and non-congested schedules in international football tournaments.





Eintracht Frankfurt Pre-match Warm-up

Below is a video from my latest stadium visit at Frankfurt - the pre-match warm-up of Eintracht Frankfurt against Greuther Fürth.





Quantifying volume and high-speed technical actions of professional soccer players using foot-mounted inertial measurement units

The aims of the study were two-fold: i) examine the validity and reliability of high-speed kicking actions using foot-mounted inertial measurement unit’s (IMU), ii) quantify soccer players within-microcycle and inter-positional differences in both the frequency and speed of technical actions.





Youth-to-Senior Transition in Elite European Club Soccer

The aim of this study was to assess the effectiveness of this direct youth-to-senior pathway by examining the extent to which club-trained players (CTPs) are currently involved in elite male European soccer.





In which league should you play as a youngster? A numerical perspective

Getting game time might be an interesting process and could be dependent on multiple factors. While every footballer would want play for the likes of Barca, PSG etc, other countries and clubs might (surely) display greater opportunities.

Below are some numbers indicating the average age of line-ups fielded, focusing on the Big 5 for Domestic league matches played between 01/01/2021 and 21/03/2022.



The youngest squads were recorded in the Croatian top division (25.3 years of age), the Mexican Liga Expansión and the Danish Superliga. At the opposite end of the spectrum (oldest squad) are: the Paraguayan top division (28.9 years of age), the Thai League 1 and the Primera División in Bolivia (not displayed).


Getting more precise about young players, the following chart displays the percentage of minutes played by footballers that have not celebrated their 21st birthday yet.



Venezuela sits at the top followed by the Danish top division declining rapidly (more than half) until Ligue 1 as the first Big Five league.


Considering 11 players in a team (and pretending there wont be a substitution in a game), there were 1.76 (U21) players in the starting line-up playing 90 minutes.


The Premier League, the Primera Division and the Serie A displaying only a quarter of that value.








The relationship between running distance and coaches’ perception of team performance in professional soccer during multiple seasons

This study analyzed how the physical movement profile of soccer matches evolved throughout a season by assessing the variability of different metrics depending on the season phase. In addition, the evolution of running distances was investigated in the relation to the team performance based on the coaches’ perception.





The New Generation of Professional Soccer Talent Is Born under the Bias of the RAE: RAE in International Male Youth Championships

In 2019, numerous championships of youth categories soccer national teams were held. The aim was to analyzed the existence of the Relative Age Effect (RAE) in four major male championships that.





Latest research in football - week 7 - 2022

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 Training load responses to football game profile-based training (GPBT) formats: effects of locomotive demands manipulation

Reference: Biol Sport. 2022 Jan;39(1):145-155. doi: 10.5114/biolsport.2021.102919. Epub 2021 Mar 9.

Authors: Antonio Dello Iacono, Viswanath Unnithan, Tzlil Shushan, Michael King, Marco Beato

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Summary: The aim of this study was to compare internal and external load profiles of different game profile-based training (GPBT) formats among elite young football players. Twenty-one participants (age: 18.7 ± 0.6 years) performed three sessions of three GPBT formats, which were matched for training volume but structured with different high-speed running and sprint demands: i) performed along linear paths (GPBT-L); ii) performed as repetitive actions of short distance including many multi-directional changes of direction (GPBT-S) and, iii) a combination of the other two protocols, that is linear high-speed runs and sprint efforts with a single change of direction (GPBT-M). External load outputs were collected using GPS units, physiological and perceptual responses were monitored with heart rate (HR) monitors, and ratings of perceived exertion (RPE), respectively. While no differences were found between formats for HR and RPE, distinct external load profiles were observed for high-speed running (HSD) and sprint distances (SD), (GPBT-L > GPBT-M > GBPT-S, all p < 0.05), and high-intensity acceleration and deceleration efforts (HIE), (GPBT-S > GPBT-M > GPBT-L, all p < 0.05). Moreover, the GPBT-S format was characterized by greater intra-session variability for HSD, SD, and HIE (CV% = 24.2%, 16.5% and 20.4%, respectively) and inter-session variability for HSD and SD (CV% = 10% and 15.7%, respectively) compared to the other two formats. Considering their load profiles and the associated reliability scores, football practitioners can implement GPBT formats interchangeably to elicit necessary internal load responses and selectively to prioritize specific external load outputs.



#2 The diagonal positioning of the goals modifies the external training load and the tactical behaviour of young football players

Reference: Biol Sport. 2022 Jan;39(1):135-144. doi: 10.5114/biolsport.2021.102929. Epub 2021 Mar 9.

Authors: Albert Canton, Carlota Torrents, Bruno Gonçalves, Angel Ric, Filippo Salvioni, Juliana Exel, Jaime Sampaio

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Summary: The aim of this study was to identify how positioning the goals in diagonal configurations on the pitch modifies the external training load and the tactical behaviour of young football players during small-sided games. Four teams of five outfield players and a goalkeeper played six small-sided games of five minutes' duration in three different scenarios: 1) Control: goals placed one in front of the other; 2) Right diagonal goals: goals placed in the right-hand corner of the offensive half-pitch; and 3) Left diagonal goals: goals placed in the left-hand corner of the offensive half-pitch. The positioning-derived data from each player were collected with 10-Hz GPS units and were used to compute external load and tactical variables. Regarding the external load variables, differences were mainly focused on distance covered while walking in defence and game pace (variability), with higher values for the diagonal scenarios. Also, the length/width ratios in offence and defence were most likely lower in diagonal scenarios. In conclusion, the results showed that players' adaptations to the environmental constraints of positioning the goals diagonally were the enhancement of the width team variable and the variability of the length.



#3 Accumulative weekly load in a professional football team: with special reference to match playing time and game position

Reference: Biol Sport. 2022 Jan;39(1):115-124. doi: 10.5114/biolsport.2021.102924. Epub 2021 Mar 4.

Authors: David Casamichana, Andrés Martín-García, Antonio Gómez Díaz, Paul S Bradley, Julen Castellano

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Summary: The aim of this study was to compare weekly accumulative load during the in-season competitive period by professional soccer players according to the amount of time played in official matches (90-min, >60-min, <60-min, and 0-min) regarding the players' position. Twenty-four professional outfield football players were monitored by GPS devices during training sessions and official matches and the accumulative weekly load were calculated for the following external load variables: total distance (TD; m), high speed running (HSR; >19.8 km·h-1), sprint meters (SPR; >25.2 km·h-1), high metabolic load distance (HMLD; >25.5 W·kg-1), number of accelerations (ACC; >3 m·s-2) and decelerations (DEC; <-3 m·s-2). This study revealed that players (as a whole o per demarcation) with more match playing time had a higher accumulative weekly load for most of the variables, but particularly at TD and HMLD (90-min and >60-min vs. <60-min and 0-min), HSR (90-min vs. <60-min and 0-min) and SPR (90-min vs. <60-min and 0-min). In addition, less positional variation was observed in relation to the competition requirements. This information would allow coaches to refine the required load with the objective of optimizing performance to soccer players.



#4 Reference values for collective tactical behaviours based on positional data in professional football matches: a systematic review

Reference: Biol Sport. 2022 Jan;39(1):110-114. doi: 10.5114/biolsport.2021.102921. Epub 2021 Mar 6.

Authors: Markel Rico-González, José Pino-Ortega, Julen Castellano, José M Oliva-Lozano, Asier Los Arcos

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Summary: Match collective tactical behaviours can be used as a reference to design and select training strategies to improve individual and team performance in professional football. The aim of the systematic review was to cluster the collective tactical variables used to highlight and compare male soccer teams' collective behaviour during professional official matches, providing reference values for each of them. A systematic review of relevant articles was carried out using three electronic databases (PubMed, SPORTdiscus and Web of Science). From a total of 1,187 studies initially found, 13 original articles were included in the qualitative synthesis. The articles found concerned studies carried out on the Spanish, Portuguese, English and Brazilian 1st divisions and during the European UEFA Champions League. The team length and width ranged from 31 to 46 m and from 35 to 48 m, respectively. The distance from a defending team's goalkeeper to the nearest teammate ranged from 9 ± 6 to 30 ± 7 m, the goal line-recovery location from 27 to 37 m, and the opponent's goal line from 42 to 50 m. The stretch index ranged from 7 to 16 m. Mean team area was ~900 m2 and the area of the pitch which included all outfield players divided by the 20 outfield players ranged from 79 ± 15 to 94 ± 16 m2. All studies provided greater distance and area values during the team-possession phase in comparison to the non-possession one. The ball location on the pitch determined the collective tactical behaviour of the teams. The differences between halves in the distance and area values were contradictory. Further studies should assess the effect of the interaction between the contextual factors on the collective tactical behaviour to obtain more accurate references. This could help football coaches in the design of suitable training tasks to optimize tactical performance.



#5 Utilisation of performance markers to establish the effectiveness of cold-water immersion as a recovery modality in elite football

Reference: Biol Sport. 2022 Jan;39(1):19-29. doi: 10.5114/biolsport.2021.103570. Epub 2021 Feb 18.

Authors: Jill Alexander, Chris Carling, David Rhodes

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Summary: Optimal strategies for recovery following training and competition in elite athletes presents ongoing debate. The effects of cold-water immersion (CWI) compared to passive recovery (PR) though a triad of performance measures after fatiguing exercise within a normal micro-cycle, during mid-competitive training cycle, in elite male footballers were investigated. Twenty-four elite footballers (age 20.58 ± 2.55 years; height 179.9 ± 5.6 cm; weight 75.7 ± 7.5 kg; body fat 6.2 ± 1.7%) were randomly assigned to CWI or PR following a fatiguing training session. Objective measures included eccentric hamstring strength, isometric adductor strength, hamstring flexibility and skin surface temperature (T sk ). Subjective measures included overall wellbeing. Data were collected at match day+3, immediately post-training, immediately post-intervention and 24 hrs post-intervention. Physiological, biomechanical and psychological measures displayed significant main effects for timepoint for eccentric hamstring strength, T sk , overall wellbeing, sleep, fatigue, stress and group for eccentric hamstring strength, T sk and sleep (groups combined). Group responses identified significant effects for timepoint for CWI and PR, for eccentric hamstring strength peak force, sleep, fatigue, and muscle soreness for CWI. Significant differences were displayed for eccentric hamstring strength (immediately post-intervention and immediately post-training) for peak force and between CWI and PR eccentric hamstring strength immediately post-intervention. Linear regression for individual analysis demonstrated greater recovery in peak torque and force for CWI. CWI may be useful to ameliorate potential deficits in eccentric hamstring strength that optimise readiness to train/play in elite football settings. Multiple measures and individual analysis of recovery responses provides sports medicine and performance practitioners with direction on the application of modified approaches to recovery strategies, within mid-competitive season training cycles.



#6 Can we evidence-base injury prevention and management in women's football? A scoping review

Reference: Res Sports Med. 2022 Feb 14;1-16. doi: 10.1080/15438627.2022.2038161. Online ahead of print.

Authors: K Okholm Kryger, A Wang, R Mehta, Fm Impellizzeri, A Massey, M Harrison, R Glendinning, A McCall

Summary: This review aimed, as part of a larger FIFA project aiming to steer women's football research, to scope literature on any level of competitive football for women, to understand the current quantity of research on women's football injuries. The study reviewed all injury-related papers scoped by a recent scoping review mapping all published women's football research with an updated search performed on 23 February 2021. Eligibility criteria assessment followed the recent scoping review with injury-specific research focus. A total of 497 studies were scoped. Most studies contained an epidemiological (N = 226; 45%) or risk factors assessment (N = 105; 21%). Less assessed areas included financial burden (N = 1; <1%) and injury awareness (N = 5; 1%). 159 studies (32%) assessed injuries of the whole body. The most common single location assessed in the literature was the knee (N = 134, 27%), followed by head/face (N =108, 22%). These numbers were, however, substantially lowered, when subdivided by playing level and age-group. The volume of research focuses especially on descriptive research and specific body locations (head/face and knee). Although information can be taken from studies in other sports, more football-specific studies to support management and prevention of injuries are warranted.



#7 High rate of muscle injury despite no changes in physical, physiological and psychophysiological parameters in a professional football team during a long-congested fixture period

Reference: Res Sports Med. 2022 Feb 13;1-12. doi: 10.1080/15438627.2022.2038159. Online ahead of print.

Authors: G S Pinheiro, R C Quintão, J G Claudino, C Carling, M Lames, B P Couto

Summary: This study aimed to analyse match availability, participation, and muscle injury incidence and to compare the effect of time intervals between matches (3-4 versus 6-7 days) on physical, physiological, and psychophysiological parameters in a professional football team during a prolonged congested fixture period. Thirteen professional male football players (29.2 ± 4.8 years old; 78.5 ± 8.3 kg; 179.3 ± 8.8 cm;) participated. Data were collected during 17 consecutive weeks for 35 official matches separated by an average interval of ≤ 3.5 days. Results showed a player availability of 84.8 ± 16.1% while match participation was 68.8% ± 6.4%. Muscle injury incidence was 19.0/ 1,000 hours of match exposure. These injuries occurred after individual players participated in sequences of 8.3 ± 3.3 consecutive matches with intervals of 3.8 ± 0.8 days. No differences were observed in physical performance or in fatigue-related parameters irrespective of the time interval between matches. A high player availability rate was observed. No differences were observed in physical, physiological, and psychophysiological indices of performance when comparing shorter and longer time intervals between consecutive matches.Prolonged exposure to fixture congestion resulted in an high risk of incurring muscle injury.



#8 Inhibition and Calendar Age Explain Variance in Game Performance of Youth Soccer Athletes

Reference: Int J Environ Res Public Health. 2022 Jan 20;19(3):1138. doi: 10.3390/ijerph19031138.

Authors: Florian Heilmann, Rainer Wollny, Franziska Lautenbach

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Summary: The assessment of core executive functions (EFs; i.e., inhibition, working memory, cognitive flexibility) has often been presented as a diagnostic tool for evaluating cognitive functions in recent publications. For example, EFs are essential in soccer because players must quickly adapt, change strategies, and inhibit responses in rapidly changing game situations. Previous research has shown relations between (subjectively rated) game performance and the EFs of soccer players. Nevertheless, the previous studies' samples were heterogeneous in their performance level (experts vs. amateurs), and the ratings were rather unsystematic (no validated rating protocol). Therefore, the current study aimed to predict soccer players' game performance (i.e., systematically rated by coaches) with the help of EF performance. Therefore, we assessed the game performance (small-sided game, Game Performance Assessment Instrument [GPAI]) and EFs (inhibition: flanker task; working memory: 3-back task; cognitive flexibility: number-letter task) of 94 male soccer players (12-19 years old) from Germany's highest competitive level. Multiple regression model results indicate that inhibition (i.e., flanker effect) and calendar age explain ~18% of players' game performance variance. Results have to be interpreted with regard to the age-dependency of game performance and EFs. In conclusion, even though the results are based on a cross-sectional study, it appears that calendar age needs to be considered when assessing EFs.



#9 Impact of Prolonged Absence of Organized Training on Body Composition, Neuromuscular Performance, and Aerobic Capacity: A Study in Youth Male Soccer Players Exposed to COVID-19 Lockdown

Reference: Int J Environ Res Public Health. 2022 Jan 20;19(3):1148. doi: 10.3390/ijerph19031148.

Authors: Sümer Alvurdu, Cihan Baykal, Zeki Akyildiz, Ömer Şenel, Ana Filipa Silva, Daniele Conte, Filipe Manuel Clemente

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Summary: The aim of this study is to examine how physical performance has changed after 15 weeks (109 days) long-term absence of organized training in youth soccer players imposed by the stay at home orders. A total of sixty-eight young male soccer players from different age categories (U15, U16, U17 and U19) voluntarily participated in the prospective cohort study. Body fat percentage (BF%), counter-movement jump (CMJ), 30 m sprint, change-of-direction (COD) and yo-yo intermittent recovery test level-1 (YYIRTL-1) were evaluated twice (before and after the detraining period). Subsequently, 2 × 2 repeated measures ANOVA was used to investigate group and time differences in repeated measurements. A significance level of p < 0.05 was implemented. CV and SWC values were calculated to test the reliability of the tests performed at different times. Statistical analysis was performed using the IBM SPSS statistics software (v.25, IBM, New York, NY, USA). Significant increments in BF%, 30 m sprint, and COD (left and right), and also significant decrements in CMJ and YYIRTL-1, were found after the detraining period. A long-term detraining period due to the stay at home orders has a detrimental effect on body composition, neuromuscular performances, and aerobic capacity in youth soccer players.



#10 Automatic Markerless Motion Detector Method against Traditional Digitisation for 3-Dimensional Movement Kinematic Analysis of Ball Kicking in Soccer Field Context

Reference: Int J Environ Res Public Health. 2022 Jan 21;19(3):1179. doi: 10.3390/ijerph19031179.

Authors: Luiz H Palucci Vieira, Paulo R P Santiago, Allan Pinto, Rodrigo Aquino, Ricardo da S Torres, Fabio A Barbieri

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Summary: Kicking is a fundamental skill in soccer that often contributes to match outcomes. Lower limb movement features (e.g., joint position and velocity) are determinants of kick performance. However, obtaining kicking kinematics under field conditions generally requires time-consuming manual tracking. The current study aimed to compare a contemporary markerless automatic motion estimation algorithm (OpenPose) with manual digitisation (DVIDEOW software) in obtaining on-field kicking kinematic parameters. An experimental dataset of under-17 players from all outfield positions was used. Kick attempts were performed in an official pitch against a goalkeeper. Four digital video cameras were used to record full-body motion during support and ball contact phases of each kick. Three-dimensional positions of hip, knee, ankle, toe and foot centre-of-mass (CMfoot) generally showed no significant differences when computed by automatic as compared to manual tracking (whole kicking movement cycle), while only z-coordinates of knee and calcaneus markers at specific points differed between methods. The resulting time-series matrices of positions (r2 = 0.94) and velocity signals (r2 = 0.68) were largely associated (all p < 0.01). The mean absolute error of OpenPose motion tracking was 3.49 cm for determining positions (ranging from 2.78 cm (CMfoot) to 4.13 cm (dominant hip)) and 1.29 m/s for calculating joint velocity (0.95 m/s (knee) to 1.50 m/s (non-dominant hip)) as compared to reference measures by manual digitisation. Angular range-of-motion showed significant correlations between methods for the ankle (r = 0.59, p < 0.01, large) and knee joint displacements (r = 0.84, p < 0.001, very large) but not in the hip (r = 0.04, p = 0.85, unclear). Markerless motion tracking (OpenPose) can help to successfully obtain some lower limb position, velocity, and joint angular outputs during kicks performed in a naturally occurring environment.



#11 Match Physical and Physiological Response of Amateur Soccer Referees: A Comparison between Halves and Match Periods

Reference: Int J Environ Res Public Health. 2022 Jan 24;19(3):1306. doi: 10.3390/ijerph19031306.

Authors: Eñaut Ozaeta, Uxue Fernández-Lasa, Inmaculada Martínez-Aldama, Ruth Cayero, Daniel Castillo

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Summary: The aim of this paper was to examine the differences in the external and internal load in amateur match officials between the 1st and 2nd half and among different 15 min periods. Twenty-three field referees (FRs) and 46 assistant referees (ARs) from the Spanish División de Honor participated in this study. Match external and internal loads were monitored showing that FRs recorded a lower Powermean, Speedmean, Cadencemean and Stiffnessmean (p < 0.05; d = 0.52 to 0.57) during the 2nd half and they also recorded a lower HRmean, and HRpeak, and spent less time in zone 5 (p < 0.05; d = 0.50 to 0.62). The FRs' match load decreased during the match but they performed higher Powermean and covered more distance in the last 15 min of the match (p < 0.01; d = 0.87 to 4.28). The ARs external load did not show significant variations between halves, but ARs recorded a lower HRmean and spent less time in zone 5 (p < 0.01; d = 0.41 to 0.63), and the highest values of Powermean, Speedmean, Cadencemean and Vertical oscillationmean during the first 15 min of the match (p < 0.05; d = 0.45 to 0.75). The highest values of HRmean and distance covered were in the 0-15 min period. Results suggest that match load decreases as the match progresses because of the neuromuscular fatigue but increases in the last 15 min.



#12 Sprint Performance and Mechanical Force-Velocity Profile among Different Maturational Stages in Young Soccer Players

Reference: Int J Environ Res Public Health. 2022 Jan 27;19(3):1412. doi: 10.3390/ijerph19031412.

Authors: Luis Miguel Fernández-Galván, Pedro Jiménez-Reyes, Víctor Cuadrado-Peñafiel, Arturo Casado

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Summary: The aim of the present study was to determine the influence of maturation status on the components of the sprint force-velocity (F-V) profile in young soccer players. Sixty-two young male soccer players from the same professional soccer academy took part in the present study. A cross-sectional design was implemented to compare the main components of the sprint F-V profile (i.e., maximal theoretical force (F0), velocity (V0), power (Pmax), and ratio of horizontal-to-resultant force (RFpeak), and decrease in the ratio of horizontal-to-resultant force (DRF)) and sprint performance (5, 20, and 30 m sprint time) among participants' maturation stages (i.e., pre-, mid- and post-peak height velocity (PHV) groups). The results show that the ES of differences in 5 min sprint performance, F0, and RFpe