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External load profile during different sport‑specific activities in semi‑professional soccer players

The aim of this study was to investigate the external load (EL) indicators differences in players of different playing positions (central backs CB, external strikers ES, fullbacks FB, midfielders MF, strikers ST, wide midfielder WM) between and within different sport-specific tasks and official matches.





Latest research in football - week 17 - 2023

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 Myocardial Work Index in Professional Football Players: A Novel Method for Assessment of Cardiac Adaptation

Reference: J Clin Med. 2023 Apr 23;12(9):3059. doi: 10.3390/jcm12093059.

Authors: Elena Refoyo, Jesús Troya, Ana de la Fuente, Almudena Beltrán, Oscar Luis Celada, Leonel Díaz-González, Roberto Pedrero-Tomé, Manuel García-Yébenes, Jose María Villalón

Summary: The global myocardial work index (GWI), a novel, valid, and non-invasive method based on speckle-tracking echocardiography, could provide value for calculating left ventricular (LV) function and energy consumption in athletes. We prospectively analyzed a single-center cohort of Spanish First-Division football players who attended a pre-participation screening program from June 2020 to June 2021, compared to a control group. All the individuals underwent an electrocardiogram and echocardiography, including two-dimensional speckle tracking and 4D-echo. The study aimed to evaluate the feasibility of myocardial work in professional football players and its correlations with other echocardiographic parameters. The study population comprised 97 individuals (49 professional players and 48 controls). The mean age was 30.48 ± 7.20 years old. The professional football players had significantly higher values of LVEDV (p < 0.001), LVESV (p < 0.001), LV-mass index (p = 0.011), PWTd (p = 0.023), and EA (p < 0.001) compared with the control group. In addition, the professional players had lower GCW (p = 0.003) and a tendency to show lower GWI values (p < 0.001). These findings could suggest that professional football players have more remodeling and less MW, related to their adaptation to intensive training. Significant differences in GLS (p = 0.01) and GWE (p = 0.04) were observed as a function of the septal thickness of the athletes. Irrespective of the MW variable, the parameters with better correlations across all the populations were SBP, DBP, and GLS. The GWI is a novel index to assess cardiac performance, with less load dependency than strain measurements. Future GWI analyses are warranted to understand myocardial deformation and other pathological differential diagnoses.



#2 Risk Factors for Sustaining a Second ACL Injury after Primary ACL Reconstruction in Female Football Players: A Study Investigating the Effects of Follow-Up Time and the Statistical Approach

Reference: Sports Med Open. 2023 May 12;9(1):29. doi: 10.1186/s40798-023-00571-x.

Authors: Anne Fältström, Martin Hägglund, Joanna Kvist, Luciana D Mendonça

Summary: Studies evaluating risk factors for sustaining an anterior cruciate ligament (ACL) injury have different, sometimes contrasting, results. Different follow-up times and statistical approaches may be a reason for these differences. The aim of this study was to explore if different follow-up times and statistical approaches, classification and regression tree (CART) analysis and Cox regression, would impact on the association between various candidate risk factors and ACL injury in female football players. In total, 112 active female football players, 18 ± 8 months after ACL reconstruction (mean age ± SD, 20 ± 2 years), were included and followed for at least 36 months. At baseline, all players underwent assessment of range of motion of knee and ankle joints, functional tests, and answered questionnaires regarding knee function, psychological and personality traits. Nineteen independent variables were included for the CART analysis and for univariable Cox regression and compared using four different follow-up times: 0-12, 0-24, 0-36, and 0->36 months. Forty-three (38%) players sustained a second ACL injury. The identified risk factors varied depending on follow-up time both with CART analysis and with Cox regression. CART identified 12 of the 19 independent variables and selected between 5 and 6 of the variables in the four different follow-up times associated with second ACL injury. The accuracy of the different follow-up times for the CART varied between 86 and 93% with 77-96% sensitivity and 70-81% specificity. Cox regression identified two risk factors: knee extension at 0-36 months and 0->36 months, and time between primary injury and surgery at 0->36 months. The accuracy varied between 54 and 64% with 44-88% sensitivity and 32-71% specificity. The identified risk factors associated with a second ACL injury varied depending on the follow-up time and statistical approach used. Thus, in future research on risk factors, the time athletes are followed up and the type of statistical methods used are important to discuss.



#3 Low adoption in women's professional football: teams that used the Nordic Hamstring Exercise in the team training had fewer match hamstring injuries

Reference: BMJ Open Sport Exerc Med. 2023 May 5;9(2):e001523. doi: 10.1136/bmjsem-2022-001523. eCollection 2023.

Authors: Jan Ekstrand, Anna Hallén, Håkan Gauffin, Håkan Bengtsson

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Summary: The primary objective was to study the reach, effectiveness, adoption, implementation and maintenance of the Nordic Hamstring Exercise (NHE) programme in women's elite teams in Europe in the 2020-21 season. The secondary objective was to compare hamstring injury rates between teams that used the NHE programme regularly in team training and teams that did not. Eleven teams participating in the Women's Elite Club Injury Study during the 2020-21 season provided data about injury rates and the implementation of the NHE programme. One team (9%) used the full original NHE programme, and four teams used the programme in the team training during parts of the season (team training group, n=5). Five teams did not use the NHE, or used it only sporadically for individual players, and one team used NHE only for players with a previous or current hamstring injury (no team training group, n=6). The team training group had a lower incidence of hamstring injuries during match-play (1.4 vs 4.0, p=0.028) than the non-team training group while no difference between groups was shown for the hamstring injury incidence in training (0.6 vs 0.7, p=0.502). A low adoption of the NHE programme was reported during the 2020-21 season. However, teams that used NHE for the whole team or most players had a lower hamstring injury incidence at match-play than teams that did not use the NHE or used it for individual players only.



#4 Symbolic consumption as a non-traditional predictor of brand loyalty in the sports industry, football club segment

Reference: Heliyon. 2023 Apr 18;9(4):e15474. doi: 10.1016/j.heliyon.2023.e15474. eCollection 2023 Apr.

Authors: Alfredo Guzmán Rincón, Ruby Lorena Carrillo Barbosa, Marelby Amado Mateus, Néstor Ordoñez Saavedra

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Summary: Brand loyalty is one of the main objectives of marketing, due to its impact on the sustainability of organisations; however, the explanation of how this type of loyalty is built in the sports industry is complex, due to the way it is organised. Traditionally, brand loyalty in this industry has been explained by satisfaction, service quality, commitment and trust, thus other variables that have been analysed from the marketing field have not been included in the models developed for the sports industry. The aim of this article was to explore the relationship between symbolic consumption as a non-traditional predictor of brand loyalty in the sports industry, more specifically in the football club segment. For this purpose, a quantitative cross-sectional study was defined, with a non-probabilistic sampling. To test the proposed relationship, modelling by means of partial least squares structural equations was chosen. The results showed that symbolic consumption is positively related to brand loyalty in the sports industry in the football club segment, with a large effect size. This study becomes a starting point for scholars who wish to further explore the relationship between symbolic consumption and brand loyalty in the context of sport. Likewise, for marketing professionals in the sports industry, it suggests the importance of symbolic consumption for the design of strategies that enable the creation of brand loyalty in consumers in the case of football clubs. In this sense, marketing professionals should seek to create advertising and promotional campaigns that appeal to strengthen the relationship of the sports consumer with their social groups based on the actual and ideal self-concept, as lifestyle.



#5 Highlighting Shooting Opportunities in Football

Reference: Sensors (Basel). 2023 Apr 24;23(9):4244. doi: 10.3390/s23094244.

Authors: Ilias Loutfi, Luis Ignacio Gómez-Jordana, Angel Ric, João Milho, Pedro Passos

Summary: The purpose of the present study was to create a two-dimensional model which illustrates a landscape of shooting opportunities at goal during a competitive football match. For that purpose, we analysed exemplar attacking subphases of each team when the ball was in the last 30 m of the field. The player's positional data (x and y coordinates) and the ball were captured at 25 fps and processed to create heatmaps that illustrated the shooting opportunities that were available in the first and second half in different field areas. Moreover, the time that the shooting opportunities were available was estimated. Results show that in the observed match, most of the shooting opportunities lasted between 1 and 2 s, with only a few opportunities lasting more than 2 s. The shooting opportunities did not display a homogenous distribution over the field. The obtained heatmaps provide valuable and specific information about each team's shooting opportunities, allowing the identification of the most vulnerable areas. Additionally, the amount, duration, and location of the shooting opportunities have shown significant differences between teams. This customizable model is sensitive to the features of shooting opportunities and can be used in real-time video analysis for individual and collective performance analysis.



#6 Injury Types and Training Habits among Soccer (Football) Athletes

Reference: Orthop Rev (Pavia). 2023 May 13;15:74883. eCollection 2023.

Authors: Jai Patel, Rohan Mangal, Thor Stead, Andrew Barbera, Latha Ganti

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Summary: For soccer athletes, injuries are frequent and pose a considerable health and financial burden for individuals and families. While studies have previously assessed the incidence of soccer injuries and preventive strategies male athletes use to reduce these occurrences, few have included women and players of varying skill levels. The aim was to report the frequency of injuries in a cohort of male and female soccer athletes and describe the training habits that have helped prevent injury. Two hundred (n=200) United States participants completed a questionnaire on soccer practicing frequency, habits, injuries, and treatments. A screening question ensured all respondents had played soccer for at least one year and determined eligibility for the study. Participant information related to age, sex, education, income, and race was also collected. JMP statistical software was used to analyze collected data and build multivariate regressions, mosaic plots, and histograms. The mean number of practice sessions per week was 3.60 +/- 1.64, and the median experience playing soccer was 2-4 years. Older participants were more likely to practice once (p = 0.0001) or twice (p= 0.0008) per week. Women were less likely to include warmups before playing soccer (p = 0.022). This was problematic as participants who did not include a proper warmup routine were more likely to have been absent from play for longer amounts of time following injury (p = 0.032). The four most common injury sites were knees (n = 35, 17.5%), ankles (n = 31, 15.5%), shoulders (n = 25, 12.5%), and head/neck (n = 24, 12%). 140 (47.62%) patients used pain medication as their main remedy, 128 (43.54%) went to physical therapy, and 26 (10.78%) underwent surgery. In any sample of soccer athletes involving variations in sex, race, and competitive play, injuries are highly common. Few studies before this one have included female athletes, and our findings highlight an important discrepancy in training habits between sexes. Women are less likely to follow a warmup regimen and are thus injured for longer. Incorporating dynamic stretching and plyometrics are particularly helpful to stay healthy.



#7 The Women's Soccer Health Study: From Head to Toe

Reference: Sports Med. 2023 May 17;1-10. doi: 10.1007/s40279-023-01860-x. Online ahead of print.

Authors: Daphne I Ling, Jo A Hannafin, Heidi Prather, Heidi Skolnik, Theresa A Chiaia, Polly de Mille, Cara L Lewis, Ellen Casey

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Summary: Women are under-represented in the sports literature despite increasing rates of sports participation. Our objective was to investigate the risks and benefits of an elite women's soccer career in five health domains: general, musculoskeletal, reproductive endocrinology, post-concussion, and mental. An online survey was distributed to retired US college, semi-professional, professional, and national team soccer players using personal networks, email, and social media. Short validated questionnaires were used to evaluate the health domains, including the Patient-Reported Outcomes Measurement Information System (PROMIS), Single Assessment Numerical Evaluation (SANE), Post-Concussion Symptom Scale (PCSS), and Patient Health Questionnaire (PHQ). A total of 560 eligible players responded to the survey over a 1-year period. The highest competitive levels were 73% college, 16% semi-professional, 8% professional, and 4% national team. The mean number of years since retirement was 12 (SD = 9), and 17.0% retired for involuntary reasons. The mean SANE scores (0-100 scale as percentage of normal) were knee = 75% (SD = 23), hip = 83% (SD = 23), and shoulder = 87% (SD = 21). The majority (63%) reported that their current activity level included participation in impact sports. A substantial proportion of players reported menstrual irregularities during their careers: 40% had fewer periods with increasing exercise and 22% had no periods for ≥ 3 months. The players (n = 44) who felt that post-concussion symptoms were due to soccer reported more time-loss concussions (F[2] = 6.80, p = 0.002) and symptom severity (F[2] = 30.26, p < 0.0001). Players who recently retired (0-5 years) reported the highest anxiety/depression scores and lowest satisfaction rates compared with those who retired 19+ years ago. Health concerns include musculoskeletal injuries, post-concussion symptoms, and lower mental health in the early years following retirement. This comprehensive survey provides initial results that will lay the foundation for further analyses and prioritize research studies that can help all female athletes.



#8 A color-related bias in offside judgments in professional soccer: A matter of figure-background contrast?

Reference: PLoS One. 2023 May 16;18(5):e0285500. doi: 10.1371/journal.pone.0285500. eCollection 2023.

Authors: Peter Wühr, Daniel Memmert

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Summary: We investigated the impact of outfit colors on the frequency of offside judgments in soccer. In a recent laboratory study, observers made more offside judgments against forwards wearing the outfit of Schalke 04 (blue shirts, white shorts) than against forwards wearing the outfit of Borussia Dortmund (yellow shirts, black shorts), when figure-background luminance contrast was higher for the former team. Here, we investigated whether a similar effect is present in real matches of the German Bundesliga. Study 1 revealed a higher offside score for Schalke 04 than for Borussia Dortmund in matches between these clubs. Studies 2-4 showed higher offside scores for teams wearing a blue/white outfit, and lower offside scores for teams wearing a yellow/black outfit, in their matches against all other Bundesliga teams. Together, results suggest that more offside judgments are made against teams of higher salience, possibly induced by differences in figure-background contrast. Notably, this color-related bias occurred in our study even though a Video-Assistant Referee (VAR) supervised the (offside) decisions of the Assistant Referees.



#9 Evaluation of Reaction Time during the One-Leg Balance Activity in Young Soccer Players: A Pilot Study

Reference: Children (Basel). 2023 Apr 19;10(4):743. doi: 10.3390/children10040743.

Authors: Fábio Saraiva Flôres, Joana Lourenço, Lucy Phan, Simon Jacobs, Renata Matheus Willig, Priscila Ellen Pinto Marconcin, Nuno Casanova, Denise Soares, Filipe Manuel Clemente, Ana Filipa Silva

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Summary: This study's aim was two-fold: (i) to test the intra-session reliability of the one-leg balance activity test; and (ii) to assess the influence of age on reaction time (RT) and the differences between dominant and non-dominant feet. Fifty young soccer players with an average age of 12.4 ± 1.8 years were divided into two groups: younger soccer players (n = 26; 11.6 ± 0.9 years) and older soccer players (n = 24; 14.2 ± 0.8 years). Each group then completed four trials (two with each leg) of the one-leg balance activity (OLBA) to evaluate RT under a single-leg stance. Mean RT and the number of hits were calculated, and the best trial was also selected. T-tests and Pearson correlations were performed for statistical analysis. Values for RT were lower, and the number of hits was higher while standing on the non-dominant foot (p = 0.01). MANOVA revealed that the "Dominant Leg" factor did not affect the multivariate composite (Pillai Trace = 0.05; F(4, 43) = 0.565; p = 0.689; Partial ETA Squared = 0.050; Observed Power = 0.174). The "Age" factor did not present an effect on the multivariate composite (Pillai Trace = 0.104; F(4, 43) = 1.243; p = 0.307; Partial ETA Squared = 0.104; Observed Power = 0.355). The results of the present investigation demonstrate that RT may be lower while standing on the non-dominant foot.



#10 The relationship of personality and executive functions in high-level soccer athletes: expertise-and gender-specific differences

Reference: Front Sports Act Living. 2023 Apr 28;5:1130759. doi: 10.3389/fspor.2023.1130759. eCollection 2023.

Authors: Jan Spielmann, Adam Beavan, Jan Mayer

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Summary: Psycho-cognitive factors such as personality and executive functions (EFs) are influential parameters when it comes to examining expertise in high-level soccer. Therefore, the profiles of those athletes are relevant both from a practical and scientific point of view. The aim of this study was to investigate the relationship between personality traits and executive functions with age group as an influential factor in high-level male and female soccer players. Personality traits and executive functions of 138 high-level male and female soccer athletes from the U17-Pros teams were assessed using the big-five paradigm. A series of linear regressions investigated contributions of personality on EF assessments and team, respectively. Linear regression models showed both negative and positive relationships between various personality traits, executive function performance and the influence of expertise and gender. Together, a maximum of 23% (R2 = 6%-23%) of the variance between EFs with personality and various teams, demonstrating that many unaccounted-for variables remain at play. The results of this study demonstrate the inconsistent relationship between personality traits and executive functions. The study calls for more replication studies to help strengthen the understanding of relationships between psycho-cognitive factors in high-level team sport athletes.



#11 Predictive modeling of the ratings of perceived exertion during training and competition in professional soccer players

Reference: J Sci Med Sport. 2023 May 8;S1440-2440(23)00081-6. doi: 10.1016/j.jsams.2023.05.001.

Authors: Emmanuel Vallance, Nicolas Sutton-Charani, Patrice Guyot, Stéphane Perrey

Summary: Evaluate the ability of predicting the ratings of perceived exertion from the external load variables in professional soccer players through a chronological perspective (i.e., past features values are considered additional features) through machine learning models by considering the playing position. Thirty-eight elite soccer players aged 19-27 years were observed during 151 training sessions, 44 matches across a full season. External load variables (58 derived from Global Positioning System and 30 from accelerometers) and the internal load derived from ratings of perceived exertion were collected for each player and each session and match. Machine learning models (linear regression, K-NN, decision trees, random forest, elastic net regression, XGBoost) were compared and interpreted in order to deepen the relationship between external load variables and ratings of perceived exertion according to the player position in a predictive perspective. Application of the machine learning models on the dataset provided enough predictive power to reduce the Root Mean Squared Error of 60 % from dummy predictions. The most accurate models (Root Mean Squared Error ≈ 1.1 for random forest and = 1 for XGBoost) highlighted a memory effect in subsequent ratings of perceived exertion values. Past ratings of perceived exertion values over one month were the strongest predicting factors of ratings of perceived exertion as compared to various external load indicators. The tree-based machine learning models showed statistically significant predictive ability, indicating valuable information for understanding the training load responses based on ratings of perceived exertion changes.



#12 Most common movements preceding goal scoring situations in female professional soccer

Reference: Sci Med Footb. 2023 May 19;1-9. doi: 10.1080/24733938.2023.2214106. Online ahead of print.

Authors: David Martínez-Hernández, Mark Quinn, Paul Jones

Summary: This study aimed to assess movements occurring during goal scoring situations in a female professional league.Data from all the goals on the Women's Super League 2018/2019 were collected through time-motion analysis using a modified version of the Bloomfield Movement Classification with differences analysed through chi-square. Analysis was performed on players (assistant, scorer [attackers], defender of assistant and defender of scorer [defenders]), movements, intensities and directions.Linear advancing motion (walking, jogging, running or sprint) (total percentage [95% CI] 37% attackers and 32.7% defenders) was the most common action preceding a goal, followed by deceleration (21.5% attackers; 18.4% defenders) and turn (19.2% attackers; 17.6% defenders). Other movements involved but with lower percentages were change in angle run (cut and arc run), ball blocking, lateral advancing motion (crossover and shuffle) and jumps. Players displayed similar tendencies but presented variations based on the role, with attackers performing more linear actions, subtle turns and cuts and defenders more ball blocking actions, lateral movements and high intensity linear actions and decelerations. Assistant performed the less percentage of involvements with at least 1 high intensity action (67.4%), scorer and defender of assistant showed similar values (86.3% and 87.1%), while defender of scorer had the highest percentage (97.3%).This study shows the importance of linear actions with other movements also being of high significance but with differentiated characteristics based on the role. This study could help practitioners design drills for the enhancement of physical capabilities related to movements occurring in goal scoring situations.



#13 Ethnic discrimination in Scandinavia: evidence from a field experiment in women's amateur soccer

Reference: Humanit Soc Sci Commun. 2023;10(1):230. doi: 10.1057/s41599-023-01734-7. Epub 2023 May 11.

Authors: Rasmus K Storm, Cornel Nesseler, Marthe Holum, Andreas Nygaard, Tor Georg Jakobsen

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Summary: In this paper, we examine ethnic discrimination using sport as a laboratory. Applying a field experiment in the three Scandinavian countries-Sweden, Norway, and Denmark-we test whether foreign female minority groups experience greater rejection rates when seeking inclusion in amateur soccer clubs. Soccer coaches were contacted by e-mail using native and foreign-sounding names from selected groups, requesting to participate in trial practice. Previous findings show persistent discrimination of foreign minority groups in the labour market, and recent work suggests that discrimination also occurs in the context of soccer. Our findings from Scandinavia show that Sweden is the only country that shows statistically significant signs of discriminatory patterns, and the probability of experiencing discrimination increases with cultural distance. However, cultural distance appears to have no influence in Norway and Denmark. We further investigate whether male or female coaches demonstrate different discriminatory behaviour when being contacted, but our analysis shows almost no gender differences. Findings suggest that how men and women differ in their discriminatory behaviour is context specific. The differences identified across nations and previous studies are discussed to better understand the mechanisms of discrimination.



#14 Comparison of Strength and Power Characteristics Before ACL Rupture and at the End of Rehabilitation Before Return to Sport in Professional Soccer Players

Reference: Sports Health. 2023 May 19;19417381231171566. doi: 10.1177/19417381231171566.

Authors: Luca Maestroni, Anthony Turner, Konstantinos Papadopoulos, Daniel Cohen, Vasileios Sideris, Philip Graham-Smith, Paul Read

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Summary: Strength and power is often reduced on the involved versus contralateral limb and healthy controls after anterior cruciate ligament (ACL) reconstruction, but no study has compared with preinjury values at the time of return to sport (RTS). Divergent recovery patterns in strength and power characteristics will be present at RTS relative to preinjury baseline data and healthy matched controls. Isokinetic strength tests, bilateral and single-leg countermovement jumps (CMJ; SLCMJ) were measured before ACL rupture in 20 professional soccer players. These then had surgical reconstruction (ACL group) and completed follow-up testing before RTS. Healthy controls (uninjured group) were tested at the same time as the ACL group preinjury. Values recorded at RTS of the ACL group were compared with preinjury. We also compared the uninjured and ACL groups at baseline and RTS. Compared with preinjury, ACL normalized quadriceps peak torque of the involved limb (difference = -7%), SLCMJ height (difference = -12.08%), and Reactive Strength Index modified (RSImod) (difference = -5.04%) were reduced after ACL reconstruction. No significant reductions in CMJ height, RSImod, and relative peak power were indicated at RTS in the ACL group when compared with preinjury values, but deficits were present relative to controls. The uninvolved limb improved quadriceps (difference = 9.34%) and hamstring strength (difference = 7.36%) from preinjury to RTS. No significant differences from baseline were shown in SLCMJ height, power, and reactive strength of the uninvolved limb after ACL reconstruction. Strength and power in professional soccer players at RTS after ACL reconstruction were often reduced compared with preinjury values and matched healthy controls. Deficits were more apparent in the SLCMJ, suggesting that dynamic and multijoint unilateral force production is an important component of rehabilitation. Use of the uninvolved limb and normative data to determine recovery may not always be appropriate.



#15 Leadership experiences of elite football team physicians during the COVID-19 pandemic: a pilot study

Reference: BMJ Lead. 2022 Jul 21;leader-2022-000603. doi: 10.1136/leader-2022-000603. Online ahead of print.

Authors: Sean Carmody, Gurneet Brar, Andrew Massey, Craig Rosenbloom, Vincent Gouttebarge, Mike Davison

Summary: The purpose of this study was to explore the leadership experiences of elite football team physicians during the COVID-19 pandemic. A pilot-study based on a cross-sectional design by means of an electronic survey was conducted. The survey relied on 25 questions divided into distinct sections including among others professional and academic experience, leadership experiences and perspectives. A total of 57 physicians (91% male; mean age: 43 years) gave their electronic informed consent and completed the survey. All participants agreed that the demands of their role had increased during the COVID-19 pandemic. Fifty-two (92%) participants reported that they felt they were expected to take more of a leadership role during the COVID-19 pandemic. Eighteen (35%) reported feeling under pressure to make clinical decisions which were not in keeping with best clinical practice. Additional roles, duties and demands expected of team doctors during the COVID-19 pandemic were subdivided into communication, decision-making, logistical, and public health demands. The findings from this pilot study suggest that the way in which team physicians at professional football clubs operate has altered since the onset of the COVID-19 pandemic, with greater demands placed on leadership skills including decision-making, communication and ethical stewardship. This has potential implications for sporting organisations, clinical practice and research.






Effect of Increasing the Number of Substitutions on Physical Performance during Periods of Congested Fixtures in Football

This study aimed to evaluate the impact on physical demands induced by FIFA’s new rule implemented based on the number of substitutions caused by COVID-19.





The Influence of Pitch Dimensions during Small-Sided Games to Reach Match Physical and Physiological Demands on the Soccer Players

The aims of this study were to (i) analyze the physical and physiological responses of four matches competition and (ii) to investigate the relationships among three different pitch dimensions of small-sided game (SSG) on the youth soccer players.





Latest research in football - week 16 - 2023

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 plyometric training on kicking performance in soccer players: A systematic review and meta-analysis

Reference: Front Physiol. 2023 Apr 13;14:1072798. doi: 10.3389/fphys.2023.1072798. eCollection 2023.

Authors: Yeqin Zhang, Danyang Li, Miguel-Ángel Gómez-Ruano, Daniel Memmert, Chunman Li, Ming Fu

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Summary: This systematic review and meta-analysis aimed to determine the pooled effect size (ES) of plyometric training (PT) on kicking performance (kicking speed and distance) in soccer players depending upon some related factors (i.e., age, gender, skill level, and intervention duration). This study was carried out according to the PRISMA guidelines. Four electronic databases-EBSCO, PubMed, Scopus, and Web of Science-were searched for relevant studies. A total of n = 16 studies yielding 17 ES with n = 553 participants were finally included in the meta-analysis. A random-effects model was used to calculate Hedge's g with a 95% confidence interval (CI), which showed that plyometric training had a large-sized positive effect on soccer kicking performance (g = 0.979, 95% CI [0.606, 1.353], p < 0.001). Subgroup analyses were performed according to participants' characteristics (i.e., age, gender, skill level) and intervention duration, demonstrating no significant differences between these subgroups. The study pointed out that plyometric training is a generally effective method to improve soccer players' kicking performance, which plays a crucial role in passing and shooting actions during games. As for soccer players and strength and conditioning coaches, the plyometric training aiming to enhance kicking performance has valuable implications in practice. Therefore, besides well-known training methods like power training in the weight room, plyometric training could be incorporated into the overall strength and conditioning programs for soccer players to reach high standards of kicking performance.



#2 Association between internal load responses and recovery ability in U19 professional soccer players: A machine learning approach

Reference: Heliyon. 2023 Apr 13;9(4):e15454. doi: 10.1016/j.heliyon.2023.e15454. eCollection 2023 Apr.

Authors: Guglielmo Pillitteri, Alessio Rossi, Carlo Simonelli, Ignazio Leale, Valerio Giustino, Giuseppe Battaglia

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Summary: The objective of soccer training load (TL) is enhancing players' performance while minimizing the possible negative effects induced by fatigue. In this regard, monitoring workloads and recovery is necessary to avoid overload and injuries. Given the controversial results found in literature, this study aims to better understand the complex relationship between internal training load (IL) by using rating of perceived exertion (RPE), recovery, and availability (i.e., subjective players' readiness status). In this cross-sectional study, twenty-two-professional soccer players (age: 18.5 ± 0.4 years, height: 177 ± 6 cm, weight: 67 ± 6.7 kg) competing in the U19 Italian Championship were monitored using RPE scale to assess IL, and TreS scale to detect information about recovery and training/match availability during an entire season (2021-2022). Autocorrelation analysis showed a repeated pattern with 7 days lag (weekly microcycle pattern) for all the variables considered (i.e., TL, recovery, and availability). For recovery (r = 0.64, p < 0.001) and availability (r = 0.63, p < 0.001) the best lag for both of them is 1 day. It indicates that recovery and availability are related to the past day value. Moreover, TL was found to be negatively affected by recovery and availability of the current day (lag = 0 day). Cross-correlation analysis indicates that TL is negatively affected by recovery (r = 0.46, p < 0.001) and availability (r = 0.42, p < 0.001) of the current day (lag = 0 day). In particular, lower recovery and availability will result in following lower TL. Furthermore, we found that TL negatively affects recovery (r = 0.52, p < 0.001) and availability (r = 0.39, p < 0.01) of the next day (lag = 1 day). In fact, the higher the TL in a current day is, the lower the recovery and availability in the next day will be. In conclusion, this study highlights that there is a relationship between TL and recovery and that these components influence each other both on the same day and on the next one. The use of RPE and TreS scale to evaluate TL and recovery/availability of players allows practitioners to better adjust and schedule training within the microcycle to enhance performance while reducing injury risk.



#3 High-intensity Actions in Elite Soccer: Current Status and Future Perspectives

Reference: Int J Sports Med. 2023 May 2. doi: 10.1055/a-2013-1661. Online ahead of print.

Authors: Alberto Filter, Jesús Olivares-Jabalera, Thomas Dos'Santos, Marc Madruga, JoséMaríaOliva Lozano, Alejandro Molina, Alfredo Santalla, Bernardo Requena, Irineu Loturco

Summary: Over the years, soccer has become more physically demanding; the number and frequency of high-intensity actions have increased, and these activities are decisive in determining the match outcome. Importantly, the reductionist approach commonly used to analyze high-intensity actions does not contemplate a more contextualized perspective on soccer performance. Traditionally, most investigations have only provided quantitative data regarding sprints (i. e. time, distances, frequency) without examining "how" (e. g. type of trajectory or starting position) and "why" (e. g. tactical role) soccer players sprint. In fact, other high-intensity actions, apart from running, are not even mentioned (i. e. curve sprints, change of direction, and specific-jump tasks). This has led to the use of tests and interventions that do not accurately reflect real game actions. Given the true technical-tactical-physical demands of each playing position, this narrative review collected a wide-spectrum of current soccer-related articles and provided a discussion regarding high-intensity actions, with a positional-based approach. In this narrative review, practitioners are encouraged to contemplate and consider the different elements that characterize high-intensity actions in soccer, in order to assess and train soccer players under a more sport-specific and integrative perspective.



#4 Reliability and validity of the 21-m shuttle-run test and its application to youth soccer players during the preseason training

Reference: Phys Act Nutr. 2023 Mar;27(1):55-59. doi: 10.20463/pan.2023.0007. Epub 2023 Mar 31.

Author: Kyeongho Byun

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Summary: This study has two purposes: first to assess the reliability and validity of the 21-m shuttle-run test (21-m SRT) and, second, to evaluate the practicality of the 21-m SRT for youth soccer players during preseason training. Twenty-seven youth soccer players (15.9 ± 0.7 yrs., males) participated in the present study. To assess the reliability of the test, each player performed the 21-m SRT twice, on separate days. Criterion validity of the 21-m SRT was determined by examining the relationship between directly measured V3 O2max and 21-m SRT performance. To test the practicality of the 21-m SRT, three 21-m SRTs and two graded exercise tests on a treadmill were performed by each youth soccer player during preseason training. Results revealed that the 21-m SRT has high correlation coefficients (r = 0.87) between test and retest and has moderate correlation coefficients (r = 0.465) between V3 O2max and SRT performance. As V3 O2max significantly increased after the training period, SRT performance (distance and heart rate immediately after the 67th shuttle run) also positively changed during the preseason training period. The 21-m SRT has high reliability with moderate validity, and it is an effective tool for coaches to examine aerobic capacity and the efficacy of a training program for youth soccer players during the preseason training period.



#5 Can the supplementation of vitamin D, sun exposure, and isolation during the COVID-19 pandemic affect the seasonal concentration of 25(OH)D and selected blood parameters among young soccer players in a one-year training season?

Reference: J Int Soc Sports Nutr. 2023 Dec;20(1):2206802. doi: 10.1080/15502783.2023.2206802.

Authors: Joanna Jastrzębska, Maria Skalska, Łukasz Radzimiński, Guillermo F López Sánchez, Lee Hill, Katja Weiss, Beat Knechtle

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Summary: This study examined the effect of vitamin D supplementation, sunlight radiationradiation, and home isolation during the COVID-19 pandemic on the seasonal changes in 25(OH)D concentration and selected biomarkers in young soccer players along a one-year training cycle. Forty elite young soccer players (age: 17.2 ± 1.16 years, body mass: 70.2 ± 5.84, and body height: 179.1 ± 4.26 cm) participated in the research. Only 24 players completed the measurements during all four time- points (T1-: September 2019, T2-: December 2019, T3-: May 2020, and T4-: August 2020) and were divided into two subgroups: supplemented group (GS) and placebo group (GP). Players from GS received 5,000 IU of vitamin D for 8 weeks (January-MarchJanuary-March 2020). Several biomarkers such as 25(OH)D, white blood cells (WBC), red blood cells (RBC), hemoglobin (HGB), muscle damage markersmarkers, and lipid profile were measured. AnalysisThe analysis of the total group demonstrated significant seasonal changes in 25(OH)D, HGB, asparagine aminotransferaseaminotransferase, and creatine kinase along the one1-year training cycle. The level of 25(OH)D concentrationinconcentration in T4 was significantly (p < 0.001, pη [ = 0.82) higher in both subgroups in comparison to T2 and T3. Moreover, the significant (p = 0.023) but poor (r = -0.23) correlation between 25(OH)D and WBC was calculated. Current research confirmed the significant seasonal changes in 25(OH)D concentration during four seasons. 8-weekEight-week vitamin D supplementation had no extended effect on the level of 25(OH)D concentration.



#6 Effectiveness of Injury Prevention Programs With Core Muscle Strengthening Exercises to Reduce the Incidence of Hamstring Injury Among Soccer Players: A Systematic Review and Meta-Analysis

Reference: Sports Health. 2023 May 4;19417381231170815. doi: 10.1177/19417381231170815.

Authors: Wesam Saleh A Al Attar, Mohamed A Husain

Summary: Muscles in the hamstring group are frequently injured in sporting activities. Injury prevention programs (IPPs), including eccentric training of the hamstrings, have proven to be of great value in decreasing the injury rate of hamstring muscles. The aim was too examine the effectiveness of IPPs that include core muscle strengthening exercises (CMSEs) in reducing hamstring injury rates. This systematic review with meta-analysis was based upon the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A systematic search was conducted for relevant studies published from 1985 to 2021 using the following databases: Cochrane Library, MEDLINE, AMED, PubMed, Web of Science, and Physiotherapy Evidence Database (PEDro). The initial electronic search found 2694 randomized controlled trials (RCTs). After removing duplicate entries, 1374 articles were screened by their titles and abstracts, and 53 full-text records were assessed, of which 43 were excluded. The remaining 10 articles were reviewed in detail, from which 5 studies met our inclusion criteria and were included in the current meta-analysis. Two researchers independently completed the abstract review and performed full-text reviews. A third reviewer was consulted to reach a consensus if any discrepancies were noted. Details were recorded about the participants, methodological aspects, eligibility criteria, intervention data, and outcome measures, including age; number of subjects in the intervention/control group; number of injuries in each group; and the duration, frequency, and intensity of the training conducted in the intervention. The pooled results of 4728 players and 379,102 exposure hours showed 47% hamstring injury reduction per 1000 h of exposure in the intervention group compared with the control group with an injury risk ratio of 0.53 (95% CI [0.28, 0.98], P = 0.04). The results indicate that CMSEs incorporated with IPPs reduce susceptibility and risk of hamstring injuries in soccer players.



#7 Prediction of Shooting Events in Soccer Videos Using Complete Bipartite Graphs and Players' Spatial-Temporal Relations

Reference: Sensors (Basel). 2023 May 5;23(9):4506. doi: 10.3390/s23094506.

Authors: Ryota Goka, Yuya Moroto, Keisuke Maeda, Takahiro Ogawa, Miki Haseyama

Summary: In soccer, quantitatively evaluating the performance of players and teams is essential to improve tactical coaching and players' decision-making abilities. To achieve this, some methods use predicted probabilities of shoot event occurrences to quantify player performances, but conventional shoot prediction models have not performed well and have failed to consider the reliability of the event probability. This paper proposes a novel method that effectively utilizes players' spatio-temporal relations and prediction uncertainty to predict shoot event occurrences with greater accuracy and robustness. Specifically, we represent players' relations as a complete bipartite graph, which effectively incorporates soccer domain knowledge, and capture latent features by applying a graph convolutional recurrent neural network (GCRNN) to the constructed graph. Our model utilizes a Bayesian neural network to predict the probability of shoot event occurrence, considering spatio-temporal relations between players and prediction uncertainty. In our experiments, we confirmed that the proposed method outperformed several other methods in terms of prediction performance, and we found that considering players' distances significantly affects the prediction accuracy.



#8 Decision-Making Time and Neuromuscular Coordination in Youth and Senior Soccer Goalkeepers

Reference: Sensors (Basel). 2023 May 4;23(9):4483. doi: 10.3390/s23094483.

Authors: Katarzyna Piechota, Edyta Majorczyk

Summary: The aim of this study was to compare soccer goalkeepers' decision-making times following a shot on goal and to determine goalkeepers' movement pattern structures using EMG in a typical game situation (two-on-one). Two groups of goalkeepers (n = 60) took part in the study: Group A, the senior group (22.00 ± 2.35 years of age), and Group B, the youth group (15.38 ± 1.32 years of age). The goalkeepers' decision-making times were measured by using EMG from the moment the attacker struck the ball until the completion of the saving action by the goalkeeper. Subsequently, the goalkeepers' movement pattern structure was determined (for both Groups A and B), and the values of muscle bioelectrical tension during a typical defensive situation in training conditions were revealed. The findings clearly indicate a significantly (p = 0.001) shorter decision-making time in experienced goalkeepers (250-260 ms) than in novices (300-320 ms). In addition, the movement pattern structure confirmed the hypotheses on the economization of effort and the visual-muscular coordination of the postural muscles (calf muscles) that affect soccer goalkeepers. The study also demonstrated a lower bioelectric tension of the gastrocnemius muscle (GAS.MED. RT-p = 0.008; GAS.LAT. RT-p = 0.030) in the expert goalkeepers.



#9 Maturity-associated variation in the body size, physical fitness, technical efficiency, and network-based centrality measures in young soccer players

Reference: Sci Rep. 2023 May 11;13(1):7693. doi: 10.1038/s41598-023-34833-1.

Authors: Paulo Henrique Borges, Julio Cesar da Costa, Luiz Fernando Ramos-Silva, Vanessa Menezes Menegassi, Gibson Moreira Praça, Felipe Arruda Moura, Enio Ricardo Vaz Ronque

Summary: This study aimed to observe the relationships between the maturity status on the network-based centrality measures of young athletes in small-sided soccer games (SSG). The study included 81 male players (14.4 ± 1.1 years). Measurements included height, sitting height, body mass, and bone age (TW3 method). The applied protocols were the following: Countermovement Jump (CMJ), Yo-Yo Intermittent Recovery Test Level 1 (YYIRT1), Repeated Sprints Ability (RSA), observational analysis of techniques, and interactions performed by players in SSG. The relationship between the set of evaluated variables within each maturity status was obtained from the correlational analysis of networks (P < 0.05). The maturity status explained a significant portion of the variance in body mass (η2 = 0.37), height (η2 = 0.30), sitting height (η2 = 0.30), and performance on the YYIRT1 (η2 = 0.08), CMJ (η2 = 0.14), and RSA (η2 = 0.13). No effect of maturity status on network-based centrality measures of young athletes was identified (P > 0.05). For the late maturity group, there was a correlation between the degree of centrality and physical growth indicators (rmean = 0.88). For players with maturation "on time", physical growth indicators relate to the degree of prestige (rmean = 0.36). It is concluded that body size and bone age impact how late and on-time maturity groups interact within the match.



#10 Reliability of individual acceleration-speed profile in-situ in elite youth soccer players

Reference: J Biomech. 2023 May;153:111602. doi: 10.1016/j.jbiomech.2023.111602. Epub 2023 Apr 26.

Authors: P Clavel, C Leduc, J-B Morin, M Buchheit, M Lacome

Summary: The aims of this study were to describe differences in the acceleration-speed (A-S) profile in-situ and to assess the week-to-week reliability of the A-S profile in-situ over a given training cycle of elite youth soccer players, in relation to the number of sessions included and analyse the effect of the inclusion or not of a specific sprint session. In this retrospective study, 18 male elite U19 football players (179.4 ± 7.1 cm; 69.0 ± 9.5 kg) participated. GPS data collected from three consecutive typical training weeks were used to calculate different combinations of A-S profile in-situ variables (theoretical maximal acceleration [A0], theoretical maximal speed [S0] and the slope of the acceleration-speed [ASslope]). The number (and content) of sessions affected mainly S0 while A0 remained similar with or without a sprint session. The reliability of the A-S profile in-situ is more related to the spread of points rather than a specific number of sessions (and thus points) and was improved when a high percentage of maximum speed (i.e. ≥ 95%) was reached. The present study showed low week-to-week variability for A0, S0 and ASslope. However, practitioners need to make sure that the values cover a sufficient range of raw data [20-95% of maximum speed] to build a clear and consistent linear regression, and in turn extrapolate meaningful A-S profile values.



#11 Effects of cold water immersion and protein intake combined recovery after eccentric exercise on exercise performance in elite soccer players

Reference: J Exerc Rehabil. 2023 Apr 27;19(2):126-133. doi: 10.12965/jer.2244596.298. eCollection 2023 Apr.

Authors: Hyoung-Won Kim, Chang-Hwa Joo

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Summary: The purpose of this study is to analyze the effects of the combined recovery method of cold water immersion (CWI) and protein supplement intake after eccentric exercise that causes muscle fatigue in elite soccer players. Eleven semiprofessional soccer players participated in this study. Participants were divided into CWI group, combined protein and CWI group (PCWI), and passive resting group (CON). The participants completed the eccentric exercise for one hour and performed one of three recovery methods. The muscle strength of the quadriceps and hamstring muscles significantly decreased at 48-hr postexercise compared to before exercise in all recovery groups (P<0.05), with no significantly different between the recovery groups. The time required to sprint 40 m was significantly longer in all groups at 24 hr and 48 hr after exercise than before exercise (P<0.05). The vertical jump height was significantly decreased at 48 hr after exercise compared to before exercise in the CON and CWI groups (P<0.05). The muscle soreness values were higher at 6 hr, 24 hr, and 48 hr after exercise than before exercise in all groups (P<0.001). The perceived recovery quality was reduced after exercise in the PCWI (P<0.01) and CON groups (P<0.001) compared to before exercise; it was unchanged in the CWI group. The recovery quality decreased at 6 hr, 24 hr, and 48 hr after exercise in all recovery groups (P<0.01). In conclusion, the combined recovery method was less effective than CWI alone for the recovery of exercise performance.



#12 Return to Play and Performance After Anterior Cruciate Ligament Reconstruction in the National Women's Soccer League

Reference: Orthop J Sports Med. 2023 May 4;11(5):23259671231164944. doi: 10.1177/23259671231164944. eCollection 2023 May.

Authors: Varag Abed, Ajith Dupati, Gregory S Hawk, Darren Johnson, Caitlin Conley, Austin V Stone

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Summary: The anterior cruciate ligament (ACL) is commonly injured in elite-level female athletes, which usually requires ACL reconstruction (ACLR). The aim was to analyze return to play (RTP) and changes in performance of players in the National Women's Soccer League (NWSL) after ACLR. NWSL players who sustained an ACL tear and underwent surgery between the 2013 and 2020 seasons were identified by multiple online resources. Players were classified as forwards, defenders, midfielders, and goalkeepers. RTP was assessed according to games played, games started, percentage of minutes played, plus/minus net per 90 minutes (a measure of a player's contribution to their team's performance while on the field), goals scored, and assists. A subanalysis was performed based on the median age at the time of the injury (≤24 vs ≥25 years). Nonparametric testing methods were used throughout the analysis. A total of 30 NWSL athletes were included. Midfielders had the highest percentage of injuries (n = 11; 36.7%), followed by forwards (n = 10; 33.3%). Overall, 27 players returned to the NWSL at a median of 12.1 months (IQR, 10.9-14.3 months), constituting a 90.0% RTP rate. There was a significant decrease in the percentage of minutes played from 1 year before the injury to 1 year after the injury (median, 87.9% [IQR, 80.7%-90.6%] vs 25.1% [IQR, 16.3%-57.2%], respectively; P = .031). Forwards and midfielders had a significant decrease in the number of assists from 1 year before the injury to 1 year after the injury (median, 3.0 [IQR, 1.0-3.0] vs 0.0 [IQR, 0.0-1.0], respectively; P = .037) as well as the number of goals scored when averaging across 2 seasons before the injury to 2 seasons after the injury (median, 3.0 [IQR, 1.5-5.5] vs 1.0 [IQR, 0.5-3.5], respectively; P = .031). On subanalysis, older players started in significantly more games (median, 12.0 [IQR, 3.8-18.5] vs 3.0 [IQR, 0.5-6.0], respectively; P = .048) and had a higher percentage of minutes played (median, 63.0% [IQR, 18.8%-77.3%] vs 14.9% [IQR, 2.0%-21.2%], respectively; P = .046) at 1 year after the injury versus younger players. There was a 90.0% RTP rate after ACLR in the NWSL. Players who returned to the NWSL had a lower percentage of minutes played in their first year after RTP, with older players starting in more games and having a greater percentage of minutes played. Compared with preinjury performance, forwards and midfielders had a significant decrease in the number of assists at 1 year after the injury as well as the number of goals scored at 2 years after the injury.



#13 Exploring the role of socioeconomic status and psychological characteristics on talent development in an English soccer academy

Reference: Sci Med Footb. 2023 May 10. doi: 10.1080/24733938.2023.2213191. Online ahead of print.

Authors: Adam L Kelly, Craig A Williams, Daniel T Jackson, Jennifer Turnnidge, Matthew J Reeves, James H Dugdale, Mark R Wilson

Summary: Social factors and psychological characteristics can influence participation and development in talent pathways. However, the interaction between these two factors is relatively unknown. The aim of this study was to investigate the implications of socioeconomic status and psychological characteristics in English academy soccer players (n=58; aged 11 to 16 years). To assess socioeconomic status, participants' home postcodes were coded according to each individual's social classification and credit rating, applying the UK General Registrar Classification system and CameoTM geodemographic database, respectively. Participants also completed the six factor Psychological Characteristics for Developing Excellence Questionnaire (PCDEQ). A classification of 'higher-potentials' (n=19) and 'lower-potentials' (n=19) were applied through coach potential rankings. Data were standardised using z-scores to eliminate age bias and data were analysed using independent sample t-tests. Results showed that higher-potentials derived from families with significantly lower social classifications (p=0.014) and reported higher levels for PCDEQ Factor 3 (coping with performance and developmental pressures) (p=0.007) compared to lower-potentials. This study can be used to support the impetus for researchers and practitioners to consider the role of social factors and psychological characteristics when developing sporting talent. For example, facilitating player-centred development within an academy and, where necessary, providing individuals with additional support.



#14 Severe CTE and TDP-43 pathology in a former professional soccer player with dementia: a clinicopathological case report and review of the literature

Reference: Acta Neuropathol Commun. 2023 May 10;11(1):77. doi: 10.1186/s40478-023-01572-3.

Authors: Suzan van Amerongen, Suzie Kamps, Kyra K M Kaijser, Yolande A L Pijnenburg, Philip Scheltens, Charlotte E Teunissen, Frederik Barkhof, Rik Ossenkoppele, Annemieke J M Rozemuller, Robert A Stern, Jeroen J M Hoozemans, Everard G B Vijverberg

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Summary: In the last decades, numerous post-mortem case series have documented chronic traumatic encephalopathy (CTE) in former contact-sport athletes, though reports of CTE pathology in former soccer players are scarce. This study presents a clinicopathological case of a former professional soccer player with young-onset dementia. The patient experienced early onset progressive cognitive decline and developed dementia in his mid-50 s, after playing soccer for 12 years at a professional level. While the clinical picture mimicked Alzheimer's disease, amyloid PET imaging did not provide evidence of elevated beta-amyloid plaque density. After he died in his mid-60 s, brain autopsy showed severe phosphorylated tau (p-tau) abnormalities fulfilling the neuropathological criteria for high-stage CTE, as well as astrocytic and oligodendroglial tau pathology in terms of tufted astrocytes, thorn-shaped astrocytes, and coiled bodies. Additionally, there were TAR DNA-binding protein 43 (TDP-43) positive cytoplasmic inclusions in the frontal lobe and hippocampus, and Amyloid Precursor Protein (APP) positivity in the axons of the white matter. A systematic review of the literature revealed only 13 other soccer players with postmortem diagnosis of CTE. Our report illustrates the complex clinicopathological correlation of CTE and the need for disease-specific biomarkers.



#15 College Soccer Student-Athletes Demonstrate Differences in Self-Reported Athlete Health When Grouped by Match Volume

Reference: J Sport Rehabil. 2023 May 9;1-8. doi: 10.1123/jsr.2022-0266. Online ahead of print.

Authors: Brett S Pexa, Justin P Waxman, Audrey E Westbrook, Kevin R Ford

Summary: Physical changes following activity are well documented, but there is limited information about self-reported outcomes around competitive matches. High training volumes and poor recovery could predispose athletes to overuse injury. The purpose of this study was to identify the changes in daily athlete health measures before, during, and after the day of each match in high- and low-volume groups. Fifty-five soccer athletes (age: 19.8 [1.2] y, 26 males, 29 females) provided daily measures of readiness, physical fatigue, mental stress, sleep quality, and soreness intensity match days, days 1 (D01) and 2 (D02) following matches, and standard practice days. Participants were grouped into high volume and low volume, based off the minutes played during the season. Soreness increased, readiness decreased, and fatigue increased on D01 compared with match days (P < .008) in the high-volume group. Between groups, the high-volume group demonstrated higher soreness on D01 and D02, lower readiness on D01 and D02, and lower fatigue on D01, compared with the low-volume group (P < .008). Soccer athletes demonstrate significant changes in self-reported athlete health variables around competitive matches. These changes are similar to physical outcomes, potentially indicating that the athlete health variables may be used to track athlete recovery from competition, potentially limiting the impact of overuse injuries.



#16 Dietary intakes and daily distribution patterns of macronutrients in youth soccer players

Reference: Front Nutr. 2023 Apr 20;10:1134845. doi: 10.3389/fnut.2023.1134845. eCollection 2023.

Authors: Diogo V Martinho, Robert J Naughton, César Leão, João Lemos, Adam Field, Ana Faria, André Rebelo, Élvio R Gouveia, Hugo Sarmento

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Summary: There has been an abundance of dietary analysis research conducted on adult male soccer players, while studies on youth players are lacking. Furthermore, the daily distribution of energy and macronutrient intake throughout the day has been reported to influence training adaptations, but this is often not considered in the literature. This study aims to quantify daily energy and macronutrient intake and assess their distribution over 5 days, and compare daily energy intakes and predicted daily energy expenditure in under-16 male soccer players. The sample included 25 soccer participants aged 14.8-15.7 years. Five-day self-reported food diaries were used to record the food/drink consumption. Intake was analyzed for total daily energy, macronutrient intakes, and distribution among meals (breakfast, lunch, dinner, and snacks). Daily energy expenditure was predicted by resting energy expenditure and physical activity levels developed for youth sports participants. The mean total energy intake was 1,928 ± 388 kcal∙day-1, whereas the estimated daily energy expenditure was 3,568 kcal∙day-1. Relative daily protein intakes were lower at breakfast, morning snack, afternoon snack, and night snack compared to lunch and dinner. Youth soccer players do not appear to meet energy requirements and daily CHO guidelines. Fluctuations in protein intake throughout the day were noted and may influence training adaptations (i.e., muscle protein synthesis and recovery).



#17 Soccer heading immediately alters brain function and brain-muscle communication

Reference: Front Hum Neurosci. 2023 Apr 20;17:1145700. doi: 10.3389/fnhum.2023.1145700. eCollection 2023.

Authors: Johnny V V Parr, Liis Uiga, Ben Marshall, Greg Wood

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Summary: There is growing evidence of a link between repetitive soccer heading and the increased incidence of neurodegenerative disease. Even a short bout of soccer heading has been shown to impair cognitive performance and disrupt movement control. However, a greater understanding of the mechanisms behind these immediate impairments is needed. The current study attempted to identify how a short bout of soccer heading alters brain function and brain-muscle communication during a movement task. Sixty soccer players were exposed to either an acute bout (i.e., 20 balls thrown underarm) of soccer heading (n = 30) or a control condition where participants (n = 30) headed soccer balls in virtual reality (VR). Before and after heading, we measured cognitive performance on the King-Devick test, as well as electromyography (EMG), electroencephalography (EEG) and brain-muscle communication (i.e., corticomuscular coherence; CMC) during a force precision task. Following the heading protocol, the VR group improved their cognitive performance whereas the Heading group showed no change. Both groups displayed more precise force contractions at post-test. However, the VR group displayed elevated frontal theta activity and global increases in alpha and beta activity during the contraction task, whereas the Heading group did not. Contrary to our expectations, the Heading group displayed elevated CMC, whereas the VR group showed no change. Our findings indicate a short bout of soccer heading may impair cognitive function and disrupt the organization of efficient neural processes that typically accompany motor skill proficiency. Soccer heading also induced corticomuscular hyperconnectivity, which could represent compensatory brain-muscle communication and an inefficient allocation of increased task-related neuromuscular resources. These initial findings offer insights to the mechanisms behind the impairments experienced after a short bout of repetitive soccer heading.






Shuttle Running Within a Small-Sided Game: Effects on Internal and External Workloads, in Young Elite Soccer Players

The purposes of this study were to compare the effects of 2 small-sided games (SSGs), shuttle running within the bout (SSG-S) versus possession play only (SSG-P) on acute physiological and metabolic responses, perception of effort, and performance.





Age and Maturation Matter in Youth Elite Soccer, but Depending on Competitive Level and Gender

This study aimed to explore the relevance of the relative age effect (RAE), maturity status and anthropometry, and their influence on coaches’ assessment of players’ performance, analyzing both genders and different types of academies (elite vs. non-elite only male displayed).





Latest research in football - week 15 - 2023

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 Quantifying the Magnitude and Longevity of the Effect of Repetitive Head Impacts in Adolescent Soccer Players: Deleterious Effect of Long Headers Extend Beyond a Month

Reference: Neurotrauma Rep. 2023 Apr 21;4(1):267-275. doi: 10.1089/neur.2022.0085. eCollection 2023.

Authors: Farzin Shamloo, Maria Kon, Elizabeth Ritter, Anne B Sereno

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Summary: There is growing interest in the effects of sports-related repetitive head impacts (RHIs) on athletes' cognitive capabilities. This study examines the effect of RHIs in data collected from adolescent athletes to estimate the magnitude and longevity of RHIs on sensorimotor and cognitive performance. A non-linear regression model estimated the longevity of RHI effects by adding a half-life parameter embedded in an exponential decay function. A model estimate of this parameter allows the possibility of RHI effects to attenuate over time and introduces a mechanism to study the cumulative effect of RHIs. The posterior distribution of the half-life parameter associated with short-distance headers (<30 m) is centered around 6 days, whereas the posterior distribution of the half-life parameter associated with long-distance headers extends beyond a month. Additionally, the magnitude of the effect of each short header is around 3 times smaller than that of a long header. The results indicate that, on both tasks, response time (RT) changes after long headers are bigger in magnitude and last longer compared to the effects of short headers. Most important, we demonstrate that deleterious effects of long headers extend beyond 1 month. Although estimates are based on data from a relatively short-duration study with a relatively small sample size, the proposed model provides a mechanism to estimate long-term behavioral slowing from RHIs, which may be helpful to reduce the risk of additional injury. Finally, differences in the longevity of the effects of short and long RHIs may help to explain the large variance found between biomechanical input and clinical outcome in studies of concussion tolerance.



#2 Relationship between respiratory muscles ultrasound parameters and running tests performance in adolescent football players. A pilot study

Reference: PeerJ. 2023 Apr 17;11:e15214. doi: 10.7717/peerj.15214. eCollection 2023.

Authors: Małgorzata Pałac, Damian Sikora, Tomasz Wolny, Paweł Linek

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Summary: Assessing the relationship between ultrasound imaging of respiratory muscles during tidal breathing and running tests (endurance and speed) in adolescent football players. Ultrasound parameters of the diaphragm and intercostal muscles (shear modulus, thickness, excursion, and velocity), speed (30-m distance), and endurance parameters (multi-stage 20-m shuttle run test) were measured in 22 male adolescent football players. The relation between ultrasound and running tests were analysed by Spearman's correlation. Diaphragm shear modulus at the end of tidal inspiration was moderately negatively (R = - 0.49; p = 0.2) correlated with the speed score at 10 m. The diaphragm and intercostal muscle shear modulus ratio was moderately to strongly negatively correlated with the speed score at 10 m and 30 m (about R = - 0.48; p = 0.03). Diaphragm excursion was positively correlated with the speed score at 5 m (R = 0.46; p = 0.04) and 10 m (R = 0.52; p = 0.02). Diaphragm velocity was moderately positively correlated with the speed score at 5 m (R = 0.42; p = 0.06) and 30 m (R = 0.42; p = 0.07). Ultrasound parameters were not significantly related to all endurance parameters (R ≤ 0.36; p ≥ 0.11). Ultrasound parameters of the respiratory muscles are related to speed score in adolescent football players. The current state of knowledge does not allow us to clearly define how important the respiratory muscles' ultrasound parameters can be in predicting some performance parameters in adolescent athletes.



#3 Piloting the use of football club community Trust's to create social Hubs for older adults

Reference: Public Health Pract (Oxf). 2023 Apr 2;5:100381. doi: 10.1016/j.puhip.2023.100381. eCollection 2023 Jun.

Authors: Steve Bullough, Lee Edmondson, Robbie Millar

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Summary: The research summarises the findings from a three-year pilot delivered through the EFL Trust and eleven Club Community Organisations. The aim was to create local social Hubs for older adults, to bring together local people to increase social connections, which may lead to additional physical activity, rather than a targeted physical activity intervention. The study was a three-year evaluation of the pilot, to track changes in attitudes and behaviours of participants, and gather feedback on the delivery mechanism and the service providers. The study included participant tracking surveys alongside interviews and focus groups with participants and service providers over the three-year pilot. The greatest impact was on participants' mental wellbeing as opposed to their physical activity levels or attitude/motivation for physical activity. Covid-19 restrictions were felt particularly hard by the most vulnerable in society and the tracking of participants quantified the negative impact of lockdown on life satisfaction and happiness, which the presence of the Hubs helped to redress. The Hubs model can offer a relatively low cost community based solution which adds to the menu of options in local health systems. The Hubs can help to tackle loneliness, enhance social interactions using the power of the football club to generate demand. The learning showed how to recruit, retain, and sustain networks of older adults using Hubs. The pilot showed the value CCOs can have in local service delivery for older adults, providing semi-structured Hubs which act as a conduit to wider engagement.



#4 The prevalence of relative age effects and the influence of the talent pool size on Australian male and female youth football

Reference: J Sports Sci. 2023 Apr 27;1-9. doi: 10.1080/02640414.2023.2204582. Online ahead of print.

Authors: Kyle J M Bennett, Andrew R Novak, Job Fransen, Rob Duffield

Summary: The current study explored the association between talent pool size and relative age effects in Football Australia's talent pathway. It also compared relative age effects between male and female players. Participants were 54,207 youth football players (females: n = 12,527, age-range = 14.0-15.9; males: n = 41,680, age-range = 13.0-14.9) eligible for the National Youth Championships. We developed linear regression models to examine the association between the member federation size and the probability of a player being born earlier in the year. We also analysed selection probabilities based on birth quartile and year half across three layers. Overall, talent pool size was associated with a higher probability of selecting a player born in the first half of the year over the second. More specifically, an increase of 760 players led to a 1% higher selection probability for those born in the first six months of a chronological age group. In addition, there were more occurrences of relative age effects in the male than the female sample. Future studies should focus on the impact of the talent pool size on relative age effects at each major talent identification/selection stage of a talent pathway.



#5 Tactical Knowledge by Decision Making and Motor Efficiency of Young Football Players in Different Playing Positions during a Three-a-Side Small-Sided Game

Reference: Behav Sci (Basel). 2023 Apr 5;13(4):310. doi: 10.3390/bs13040310.

Authors: Rui Matos, Carlos Moreira, Emília Alves, José Eduardo Teixeira, Filipe Rodrigues, Diogo Monteiro, Raul Antunes, Pedro Forte

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Summary: The aim of this study was to compare the tactical knowledge of young football players in different playing positions during a three-a-side small-sided game (SSG). Observational data was collected from 71 players (M = 12.16; SD = 1.55 years): 11 goalkeepers, 22 defenders, 15 midfielders, and 23 forwards. In total, 4 min of three-a-side SSGs (GR + 3 vs. 3 + GR) were recorded to assess tactical performance using a digital camera (GoPro Hero 6® version 02.01). The SSGs were performed on a field with a constant area (36 × 27 m). Video analyses were performed using LongoMatch® version 1.5.9 to record football performance; we then assessed tactical performance by using the Football Tactical Assessment System (Fut-Sat). This instrument evaluates the average of well-defined action indexes for each game in decision making principle and motor skills, specifically: (i) Decision Making Index (DMI); (ii) Motor Effectiveness Index (MEI); (iii) Effectiveness Index (I). The indexes were calculated by the ratio between the correct actions and the total. The Kruskal-Wallis test was used to evaluate differences between playing positions. The results showed that tactical performance by principles seems to be significantly different according to playing position. Differences were found between defenders and forwards (H = -11.92; p = 0.03) and defenders and midfielders (H = -16.13; p = 0.01) in contention principle. In conclusion, tactical knowledge of training based on the principles of the game can help coaches and players better understand and predict each player's actions during the game.



#6 Thermoregulatory, Cardiovascular and Perceptual Responses of Spectators of a Simulated Football Match in Hot and Humid Environmental Conditions

Reference: Sports (Basel). 2023 Mar 31;11(4):78. doi: 10.3390/sports11040078.

Authors: Johannus Q de Korte, Thijs M H Eijsvogels, Maria T E Hopman, Coen C W G Bongers

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Summary: Major sporting events are often scheduled in thermally challenging environments. The heat stress may impact athletes but also spectators. We examined the thermal, cardiovascular, and perceptual responses of spectators watching a football match in a simulated hot and humid environment. A total of 48 participants (43 ± 9 years; n = 27 participants <50 years and n = 21 participants ≥50 years, n = 21) watched a 90 min football match in addition to a 15 min baseline and 15 min halftime break, seated in an environmental chamber (Tair = 31.9 ± 0.4 °C; RH = 76 ± 4%). Gastrointestinal temperature (Tgi), skin temperature (Tskin), and heart rate (HR) were measured continuously throughout the match. Mean arterial pressure (MAP) and perceptual parameters (i.e., thermal sensation and thermal comfort) were scored every 15 min. Tri (37.3 ± 0.4 °C to 37.4 ± 0.3 °C, p = 0.11), HR (76 ± 15 bpm to 77 ± 14 bpm, p = 0.96) and MAP (97 ± 10 mm Hg to 97 ± 10 mm Hg, p = 0.67) did not change throughout the match. In contrast, an increase in Tskin (32.9 ± 0.8 °C to 35.4 ± 0.3 °C, p < 0.001) was found. Further, 81% of participants reported thermal discomfort and 87% a (slightly) warm thermal sensation at the end of the match. Moreover, the thermal or cardiovascular responses were not affected by age (all p-values > 0.05). Heat stress induced by watching a football match in simulated hot and humid conditions does not result in substantial thermal or cardiovascular strain, whereas a significant perceptual strain was observed.



#7 Relationship between Football-Specific Training Characteristics and Tibial Bone Adaptation in Male Academy Football Players

Reference: Sports (Basel). 2023 Apr 19;11(4):86. doi: 10.3390/sports11040086.

Authors: Ian Varley, Craig Sale, Julie P Greeves, John G Morris, Caroline Sunderland, Chris Saward

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Summary: We examined the relationship between football-specific training and changes in bone structural properties across a 12-week period in 15 male football players aged 16 years (Mean ± 1 SD = 16.6 ± 0.3 years) that belonged to a professional football academy. Tibial scans were performed at 4%, 14% and 38% sites using peripheral quantitative computed tomography immediately before and 12 weeks after increased football-specific training. Training was analysed using GPS to quantify peak speed, average speed, total distance and high-speed distance. Analyses were conducted with bias-corrected and accelerated bootstrapped 95% confidence intervals (BCa 95% CI). There were increases in bone mass at the 4% (mean ∆ = 0.15 g, BCa 95% CI = 0.07, 0.26 g, g = 0.72), 14% (mean ∆ = 0.04 g, BCa 95% CI = 0.02, 0.06 g, g = 1.20), and 38% sites (mean ∆ = 0.03 g, BCa 95% CI = 0.01, 0.05 g, g = 0.61). There were increases in trabecular density (4%), (mean ∆ = 3.57 mg·cm-3, BCa 95% CI = 0.38, 7.05 mg·cm-3, g = 0.53), cortical dentsity (14%) (mean ∆ = 5.08 mg·cm-3, BCa 95% CI = 0.19, 9.92 mg·cm-3, g = 0.49), and cortical density (38%) (mean ∆ = 6.32 mg·cm-3, BCa 95% CI = 4.31, 8.90 mg·cm-3, g = 1.22). Polar stress strain index (mean ∆ = 50.56 mm3, BCa 95% CI = 10.52, 109.95 mm3, g = 0.41), cortical area (mean ∆ = 2.12 mm2, BCa 95% CI = 0.09, 4.37 mm2, g = 0.48) and thickness (mean ∆ = 0.06 mm, BCa 95% CI = 0.01, 0.13 mm, g = 0.45) increased at the 38% site. Correlations revealed positive relationships between total distance and increased cortical density (38%) (r = 0.39, BCa 95% CI = 0.02, 0.66), and between peak speed and increased trabecular density (4%) (r = 0.43, BCa 95% CI = 0.03, 0.73). There were negative correlations between total (r = -0.21, BCa 95% CI = -0.65, -0.12) and high-speed distance (r = -0.29, BCa 95% CI = -0.57, -0.24) with increased polar stress strain index (38%). Results suggest that despite football training relating to increases in bone characteristics in male academy footballers, the specific training variables promoting adaptation over a 12-week period may vary. Further studies conducted over a longer period are required to fully elucidate the time-course of how certain football-specific training characteristics influence bone structural properties.



#8 Relationships between contract status and player performance in the Australian Football League

Reference: J Sports Sci. 2023 Apr 27;1-11. doi: 10.1080/02640414.2023.2190564. Online ahead of print.

Authors: Sam McIntosh, Sam Robertson

Summary: This study analysed the extent to which player performance differs within the Australian Football League (AFL) with respect to the status of a player's contract. AFL Player Ratings (AFLPR) and contract data were obtained during the 2013-2020 AFL seasons for all 827 players listed by an AFL club at the beginning of the 2020 season. A model of "expected performance" was created allowing for an exploration into the differential with actual performance as a function of contract status. Paired t-tests indicated that there was a difference in performance pre- and post-signing their contract for players who signed mid-season (mean change and 95% confidence interval of -1.48 ± 0.93 and -0.49 ± 0.48 AFLPR, at ten match intervals for those in- and out-of-contract at the conclusion of that year's season, respectively). Further differences existed between the groups of players who signed mid-season, as compared to those who signed during the off-season. Correlation analyses indicated that more consistent performers are somewhat less likely to see a reduction in performance post signing as compared to less consistent performers. The applications of these findings have the potential to support organisational decisions relating to the timing and nature of player contracting.



#9 What Are the Load and Wellness of Young Second-Team Football Players When Transitioning to the First Team? A Comparison of 2 Consecutive Preseasons

Reference: Int J Sports Physiol Perform. 2023 Apr 27;1-8. doi: 10.1123/ijspp.2022-0324. Online ahead of print.

Authors: Imanol Martin-Garetxana, Jon Ciaurri, Susana M Gil, Xabier Monasterio, Aitor Ugarte, Jose A Lekue, Jon Larruskain

Summary: The aim was to compare the load and wellness of second-team academy football players during a first-team preseason with those of first-team players and those of their previous second-team preseason. Athletic Club's first- (n = 10) and second-team (n = 9) players were prospectively followed during the 2019-20 first- and second-team and 2020-21 first-team preseasons. Weekly external and internal loads and average wellness z-scores (fatigue, sleep quality, muscle soreness, stress, and mood) were compared between preseasons and teams. While training together during the 2020-21 preseason, second-team players performed more decelerations <-3 m/s2 per week than first-team players (moderate effect size). For first-team players, there were only small differences between preseasons in external load, but session rating of perceived exertion was higher (moderate) and stress (moderate) and mood (large) z-scores were worse in 2020-21. For second-team players, more total distance (large), accelerations >3 m/s2 (large), and decelerations <-3 m/s2 (very large) were performed; total loading (moderate) and session rating of perceived exertion (moderate) were higher; and fatigue (very large) and stress (moderate) z-scores were worse during the 2020-21 first-team preseason compared to their previous second-team preseason. Players transitioning from the second team faced higher external and internal loads, fatigue, and stress during the first-team preseason compared to the previous second-team preseason. Player development and monitoring plans appear necessary to manage the transition from the academy to the first team.



#10 Characterization of Head Acceleration Exposure During Youth Football Practice Drills

Reference: J Appl Biomech. 2023 Apr 27;1-12. doi: 10.1123/jab.2022-0196. Online ahead of print.

Authors: Ty D Holcomb, Madison E Marks, N Stewart Pritchard, Logan Miller, Mark A Espeland, Christopher M Miles, Justin B Moore, Kristie L Foley, Joel D Stitzel, Jillian E Urban

Summary: Many head acceleration events (HAEs) observed in youth football emanate from a practice environment. This study aimed to evaluate HAEs in youth football practice drills using a mouthpiece-based sensor, differentiating between inertial and direct HAEs. Head acceleration data were collected from athletes participating on 2 youth football teams (ages 11-13 y) using an instrumented mouthpiece-based sensor during all practice sessions in a single season. Video was recorded and analyzed to verify and assign HAEs to specific practice drill characteristics, including drill intensity, drill classification, and drill type. HAEs were quantified in terms of HAEs per athlete per minute and peak linear and rotational acceleration and rotational velocity. Mixed-effects models were used to evaluate the differences in kinematics, and generalized linear models were used to assess differences in HAE frequency between drill categories. A total of 3237 HAEs were verified and evaluated from 29 football athletes enrolled in this study. Head kinematics varied significantly between drill categorizations. HAEs collected at higher intensities resulted in significantly greater kinematics than lower-intensity drills. The results of this study add to the growing body of evidence informing evidence-based strategies to reduce head impact exposure and concussion risk in youth football practices.



#11 Programming High-Speed and Sprint Running Exposure in Football: Beliefs and Practices of More Than 100 Practitioners Worldwide

Reference: Int J Sports Physiol Perform. 2023 Apr 28;1-16. doi: 10.1123/ijspp.2023-0013. Online ahead of print.

Authors: Antonio Dello Iacono, Marco Beato, Viswanath B Unnithan, Tzlil Shushan

Summary: The aim was to gain knowledge on the beliefs and practices of football practitioners applying high-speed and sprint running exposure programming strategies. One hundred two football practitioners from 22 different countries participated in a study consisting of a survey including 5 domains: demographic and professional characteristics (Who); importance of high-speed and sprint running exposure for physical-capability development, preparation for competition, and injury-prevention strategies (Why); exposure timing (When); methodological procedures for exposure monitoring and training scheduling (What); and effectiveness of common training practices (How). Data were analyzed using a combination of descriptive statistics, generalized mixed effects, and multinomial logistic regression models. Data revealed 5 main findings: (1) overall agreement on the importance of exposure for physical-capability development, preparation for competition, and injury-prevention strategies; (2) different exposure timing and selective training scheduling for starting and nonstarting players across typical and congested weeks; (3) lack of consensus on the conceptual constructs defining high-speed and sprint running metrics and the methodological procedures used for monitoring; (4) a probable association between match-related outcomes and exposure strategies used in training; and (5) a broad range of training methods considered effective to elicit exposure. This study provides actionable insights into the planning, implementing, and monitoring strategies for high-speed and sprint running exposure in football. While some conform with the evidence on high-speed and sprint running training in football, further research and professional debate are warranted to develop empirical knowledge and provide pragmatic recommendations to help practitioners in adopting evidence-informed decisions.



#12 Air pollution and elite adolescent soccer players' performance and well-being; an observational study

Reference: Environ Int. 2023 Apr 27;175:107943. doi: 10.1016/j.envint.2023.107943. Online ahead of print.

Authors: Adam Beavan, Sascha Härtel, Jan Spielmann, Michael Koehle

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Summary: Exercising outdoors may inadvertently lead to individuals inhaling levels of air pollution that may be detrimental to their health and activity-related performance. Endurance athletes are a particularly susceptible subgroup due to their high ventilation rates sustained over prolonged periods of time coupled with high training loads that often occur outdoors. In this study, we estimate the effects of air pollution on a series of athletic performance parameters in an elite adolescent soccer team. External, internal, and subjective loads and wellness questionnaires were recorded for the 26 matches and 197 training sessions carried out during the 2018-19 season for a U19 team competing in Germany. Each session was combined with hourly information on the concentration of PM10, O3 and NO2 in spatial proximity to each playing field for the duration of training or playing. Increases in PM10 and O3 had significant (p <.001) associations with decreasing total distance (m) ran per session. Furthermore, increases in O3 and NO2 concentrations were related to an increase in average heart rate (p <.05). Moreover, increases in PM10 concentration was associated with increased rating of perceived exertion (p <.001). Last, the total inhaled dose of O3 and NO2 over one session was linked to significant (p <.05) decreases in athletes' wellness scores on the following morning. We find supporting evidence of the negative effects of air pollution in elite adolescent soccer players in both matches and training. The negative impacts observed on several aspects of performance are present within an elite team that regularly trained in pollution levels well within the normal ranges of what the World Health Organisation (WHO) reports to be suitable air quality. Therefore, mitigation strategies such as monitoring the air quality at the training pitch are recommended to reduce athlete exposure to air pollution even when exercising in moderate air quality.



#13 Most modifiable risk factors for hamstring muscle injury in women's elite football are extrinsic and associated with the club, the team, and the coaching staff and not the players themselves: the UEFA Women's Elite Club Injury Study

Reference: Knee Surg Sports Traumatol Arthrosc. 2023 May 1. doi: 10.1007/s00167-023-07429-5.

Authors: Jan Ekstrand, Anna Hallén, Vittoria Marin, Håkan Gauffin

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Summary: The aim was to describe the perceived importance of suggested hamstring injury risk factors according to chief medical officers (CMOs) of European women's professional football clubs. A secondary objective was to compare if these perceptions differed between teams with a lower-than-average and higher-than-average hamstring injury burden. The CMOs of eleven European professional women's football clubs were initially asked to suggest modifiable risk factors for hamstring injury. These risk factors were rated in according with their perceived importance on a 5-graded Likert scale. Participating teams were divided in two groups depending on their hamstring injury burden during the 2020/21 season. The LOW group consisted of six teams that had a lower-than-average hamstring injury burden. The HIGH group consisted of five teams that had a higher-than-average hamstring injury burden. Twenty-one risk factors were suggested, most of which were extrinsic in nature, hence associated with the coaching staff, the team or the club organization rather than with the players themselves. The risk factors with the highest average importance were: "lack of communication between medical staff and coaching staff" and "load on players" (each with a weighted average of 3.9), followed by "lack of regular exposure to high-speed football actions during training" and "playing matches 2-3 times a week" (weighted average of 3.8 and 3.7). Differently from the LOW group, the HIGH group perceived the coaching factors (style of coach leadership, training/exercise surveillance by coaching staff) as more important. In accordance to the eleven CMOs recruited in this study, most risk factors for hamstring injuries are extrinsic in nature and associated with the club, the team, and the coaching staff, and not the players themselves.



#14 Incidence of football injuries sustained on artificial turf compared to grass and other playing surfaces: a systematic review and meta-analysis

Reference: EClinicalMedicine. 2023 Apr 13;59:101956. doi: 10.1016/j.eclinm.2023.101956. eCollection 2023 May.

Authors: Ilari Kuitunen, Ville Immonen, Oskari Pakarinen, Ville M Mattila, Ville T Ponkilainen

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Summary: Prior reviews have not conducted statistical synthesis of injury incidence on artificial turf in football. To analyse and compare the incidence of injuries sustained playing football (soccer) on artificial turf compared to grass and other playing surfaces. This was a systematic review and meta-analysis. We searched PubMed, Scopus, SPORTDiscus, and Web of Science databases in October 2022 without filters. All observational studies (prospective or retrospective) that analysed injuries sustained playing football on artificial turf and which included a control group that played on grass or other surface were included. Studies were included if they reported the number of injuries and the exposure time for the playing surfaces. Risk of bias was assessed by Newcastle-Ottawa Scale. A random effects model was used to calculate the pooled incidence rate ratios (IRR) with 95% confidence intervals. Protocol was registered with PROSPERO on October 30th, 2022. Registration number: CRD42022371414. We screened 1447 studies, and evaluated 67 full reports, and finally included 22 studies. Risk of bias was a notable issue, as only 5 of the 22 studies adjusted their analysis for potential confounders. Men (11 studies: IRR 0.82, CI 0.72-0.94) and women (5 studies: IRR 0.83, CI 0.76-0.91) had lower injury incidence on artificial turf. Professional players had a lower incidence of injury (8 studies: IRR 0.79, CI 0.70-0.90) on artificial turf, whereas there was no evidence of differences in the incidence of injury in amateur players (8 studies: IRR 0.91, CI 0.77-1.09). The incidence of pelvis/thigh (10 studies: IRR 0.72, CI 0.57-0.90), and knee injuries (14 studies: IRR 0.77, CI 0.64-0.92) were lower on artificial turf. The overall incidence of football injuries is lower on artificial turf than on grass. Based on these findings, the risk of injury can't be used as an argument against artificial turf when considering the optimal playing surface for football.



#15 Impact of (long) COVID on athletes' performance: a prospective study in elite football players

Reference: Ann Med. 2023 Dec;55(1):2198776. doi: 10.1080/07853890.2023.2198776.

Authors: E Wezenbeek, S Denolf, J G Bourgois, R M Philippaerts, B De Winne, T M Willems, E Witvrouw, S Verstockt, J Schuermans

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Summary: The aim was to investigate possible persistent performance deficits after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in elite athletes. A prospective cohort study in three Belgian professional male football teams was performed during the 2020 - 2021 season. Participants were submitted to strength, jump, and sprint tests and an aerobic performance test (the Yo-Yo Intermittent Recovery test (YYIR)). These tests were repeated at fixed time intervals throughout the season. Assessment of SARS-CoV-2 infection was performed by a polymerase chain reaction (PCR) test before each official game. Of the 84 included participants, 22 were infected with SARS-CoV-2 during follow-up. At the first testing after infection (52.0 ± 11.2 days after positive PCR testing) significantly higher percentages of maximal heart rate (%HRmax) were seen - within the isolated group of infected players- during (p = .006) and after the YYIR (2 min after, p = .013), compared to pre-infection data. This increase in %HRmax was resolved at the second YYIR testing after infection (127.6 ± 33.1 days after positive PCR testing). Additionally, when comparing the first test after infection in formerly infected to non-infected athletes, significantly higher %HRmax were found during (p < .001) and after the YYIR test (p < .001),No significant deficits were found for the jump, muscular strength or sprint tests. Aerobic performance seems compromised even weeks after infection. Simultaneously, anaerobic performance seemed to be spared. Because of the potential detrimental effects on the immune system, caution might be advised with high-intensity exposure until aerobic performance is restored.KEY MESSAGESElite football players' aerobic performance seems to be affected for weeks after they return to sports after a SARS-CoV-2 infection.Similarly, anaerobic performance tests showed no discernible changes between both before and after SARS-CoV-2 infections.Regular YYIR testing is recommended to monitor aerobic performance after SARS-CoV-2 infection.



#16 Electrocardiogram of Brazilian Elite Football Players: Filling a Gap

Reference: Arq Bras Cardiol. 2023 May 1;120(4):e20230090.  doi: 10.36660/abc.20230090. [Article in English, Portuguese]

Authors: Ricardo Stein, Filipe Ferrari, Anderson Donelli da Silveira

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#17 Youth-to-senior transition in women's and girls' football: Towards a better understanding of relative age effects and gender-specific considerations

Reference: PLoS One. 2023 May 4;18(5):e0283781. doi: 10.1371/journal.pone.0283781. eCollection 2023.

Authors: Paolo Riccardo Brustio, Roberto Modena, Gennaro Boccia, Matteo Vogliazzo, Adam Leigh Kelly

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Summary: This study aimed to evaluate youth-to-senior transition and the relative age effect in Italian female football national teams. Birthdate data of 774 female players selected for Under 17 (N = 416), 19 (N = 265) and National Senior team (N = 93) were analysed. The youth-to-senior transition rate was determined by the number of youth players competing in the Senior National team (and vice versa), whilst birth quarter (Q) distributions with a chi-square goodness-of-fit test. Only 17.4% of youth players were able to be selected for the Senior National team, whereas 31.2% of the players reached the high-senior level without being selected for youth age groups. Data revealed a skewed birth date distribution in Under 17 and 19 teams (on average, Q1 = 35.6% vs Q4 = 18.5%) but not in the Senior National team. Youth players born in Q1 were two times more likely to be selected than in Q4. In Under 17, goalkeepers, defenders, and midfielders of Q1 players were overrepresented. However, Q4 players recorded higher conversion rates than Q1 (Q1 = 16.4% vs. Q4 = 25.0%). National youth experience may not be a prerequisite for being selected at the senior level. Moreover, this confers a higher probability of playing in the National Senior team than players not selected in youth rosters.



#18 Performance in field-tests and dynamic knee valgus in soccer players psychologically ready and not ready to return to sports after ACL reconstruction

Reference: Knee. 2023 Apr 27;42:297-303. doi: 10.1016/j.knee.2023.04.011. Online ahead of print.

Authors: Ricardo V Correa, Evert Verhagen, Renan A Resende, Juliana M Ocarino

Summary: The objective was to compare the performance in field tests, dynamic knee valgus, knee function, and kinesiophobia of soccer players who were psychologically ready and not ready to return to unrestricted training or competitions after ACL reconstruction. Thirty-five male soccer players who had undergone primary ACL reconstruction at least 6 months were divided based on the Anterior Cruciate Ligament Return to Sport after Injury (ACL-RSI) questionnaire score into ready (≥60) and not-ready (<60) groups. The modified Illinois change of direction test (MICODT) and reactive agility test (RAT) were used to impose the demand for directional change and reactive decision-making. We assessed the frontal plane knee projection angle (FPKPA) during a single-leg squat and distance in crossover hop test (CHD). In addition, we assessed kinesiophobia through the shortened version of the Tampa Scale of Kinesiophobia (TSK-11) and knee function using the International Knee Documentation Committee Subjective Knee Form (IKDC). Independent t-tests were used to compare the groups. The not-ready group had lower performance on the MICODT (effect size (ES) = -1.2; p < 0.001) and RAT (ES = -1.1; p = 0.004) tests and higher FPKPA (ES = 1.5; p < 0.001). In addition, they presented lower IKDC (ES = 3.1; p < 0.001) and higher TSK-11 (ES = -3.3; p < 0.001) scores. Physical and psychological deficits may persist in some individuals after rehabilitation. On-field tests and dynamic knee alignment evaluation should be included in the athlete evaluation before the decision-making about clearance to sports participation, especially in athletes who perceive themselves as psychologically not ready.



#19 Better decision-making skills support tactical behaviour and reduce physical wear under physical fatigue in soccer

Reference: Front Physiol. 2023 Apr 12;14:1116924. doi: 10.3389/fphys.2023.1116924. eCollection 2023.

Authors: Felipe Dambroz, Israel Teoldo

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Summary: The purpose of this study was to verify whether decision-making skills influence the tactical behavior and physical performance of soccer players under acute physical fatigue, assessed in an actual game-play. The sample was comprised of 24 trained soccer players (18.25 ± 1.48 years old) from two Brazilian clubs grouped into two categories with 12 players each (with high and low decision-making skills). The assessment of decision making, tactical behavior, and physical performance were carried out using TacticUP®, FUT-SAT, and GPSports®, respectively. Acute physical fatigue was induced through the T-SAFT90 test. Results showed that under acute physical fatigue players with high decision-making skills maintained tactical behavior efficiency and had their paces reduced, in addition to displaying reduced total distance covered (p < 0.001), number of accelerations (p < 0.001), and decelerations (p < 0.001), and average movement speed (p < 0.001). On the other hand, players with low decision-making skills displayed reduced tactical behavior efficiency (p = 0.002) and maintained their movement pace under physical fatigue. It is concluded that decision-making skills contribute to players' tactical behavior efficiency under acute physical fatigue, besides promoting reduced physical strain in movement actions throughout the field.






Relationship between Objective and Subjective Fatigue Monitoring Tests in Professional Soccer

The purpose of this study was to evaluate the relationships between objective fatigue variables (Squat Jump (SJ) and Countermovement Jump (CMJ)) measured on day-2 to the game and subjective fatigue (Rating Perceived Exertion (RPE) measured on day-3 to the game and Hooper Index (HI) measured on day-2).





Do Repeated Sprints Affect the Biceps Femoris Long Head Architecture in Football Players with and without an Injury History?

The aim was to compare the biceps femoris long head (BFlh) architecture between football players with (twelve) and without (twenty) history of BFlh injury before and after a repeated sprint task. 





Top clubs for U20 players' employment

Game time is a crucial factor for player development. Players and agents might be interested in clubs and philosophies that enables game time, consequently, having a look on the percentage of minutes played by footballers who had not yet turned 20 in domestic league matches played over the last five years. A total of 1,168 clubs in 76 leagues worldwide were analysed.


Denmark’s Nordsjælland sits up top with a staggering 37% of minutes played by a player younger than 20 years of age. Slovakia’s MŠK Žilina and Septemvri Sofia of Bulgaria complete the podium.



Two Venezuelan clubs (Mineros de Guayana and Deportivo La Guaira) follow, as well as RSC Anderlecht located in Belgium.


Uruguay’s Defensor SC are the 3rd highest ranked non-European team, ahead of another Venezuelan team, Monagas SC, and Ecuador’s Independiente del Valle.


As usual a look at the Big5 clubs is in order. Borussia Dortmund leads with 12,5% of minutes played by players younger than 20. Stade Rennais and FC Barcelona follows with 9.4 and 8.2% respectively. Arsenal FC as the first Premier League team comes in at place 17 where 4,5% of minutes played by players under the age of 20. 



Interestingly, 6 from the first 10 clubs derive from the Ligue 1 (France), followed by Bundesliga and La Liga.


Furthermore, Ligue 1 represents 37% of all teams of the top 30 teams ranked by minutes played by players below the age of 20 in the BIG5. The Bundesliga (27%), La Liga and the Premier League (both 13%) sits in front of Serie A (Italy) with 10%.



To conclude this information, it can be said that players under the age of 20, should be mindful of minutes played in the aforementioned leagues. Consequently, considering playing in a league (and a club) that favors young and developing players could be of advantage with regards to game time.







Weekly External Load Performance Effects on Sports Injuries of Male Professional Football Players

This prospective study aimed to examine in detail the effects of sports injuries on professional football players’ weekly external load performances.





Soccer academy practitioners’ perceptions and application of bio-banding

The primary aims of this study were to examine the application of maturity status bio-banding within professional soccer academy programmes and understand the methods employed, the intended objectives, and the potential barriers to bio-banding.





Latest research in football - week 14 - 2023

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 Acute effects of the FIFA11+ and Football+ warm-ups on motor performance. A crossover randomized controlled trial

Reference: PLoS One. 2023 Apr 20;18(4):e0284702. doi: 10.1371/journal.pone.0284702. eCollection 2023.

Authors: Mojtaba Asgari, Marcus Schmidt, Benedikt Terschluse, Maximilian Sueck, Thomas Jaitner

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Summary: Few studies including contradictory results have addressed the acute effects of the 11+ on motor performance, indicating a potentially reduced applicability of the program for warming up before competitions. This study aims to compare the acute effects of a soccer-specific warm-up (Football+) and the 11+ on motor performance. Thirty-eight volunteer collegiate players (22 males; age = 21.1±1.9 years, height = 1.81± 0.06 m, weight = 73.4± 9.5 kg; 16 females; age = 21.3±1.5 years; height = 1.71± 0.07 m, weight = 67.8± 8.5 kg) underwent the 11+ and the Football+ in a randomized crossover design with a one-week washout. The Football+ starts with a self-estimated 40-50 percent running, followed by dynamic stretching of the hip muscles, shoulder contact, controlled lunge, Copenhagen exercise, and modified Nordic hamstring exercise. The second part involves roughly intensive small-sided games, followed by plyometric and anaerobic exercises in the third part. The warm ups' effects on performance were determined by a linear sprinting test (20 m), countermovement jump performance (CMJ), Illinois agility (IA), and dribbling speed (DS) tests. Within-subject differences were reported as the means and SD. Pairwise t tests at the significance level of p<0.05 were used to calculate the significant differences. Overall, except for the CMJ (mean = -0.43±3.20 cm, p = 0.21, d = -0.13), significant differences for the 20 m sprint (mean = 0.04±0.10 s, p = 0.005, d = 0.42), IA (mean = 0.65±0.45 s, p = 0.01, d = 1.43), and DS (mean = 0.60±1.58 s, p = 0.012, d = 0.38) were observed. In females, significant differences observed only for IA (mean difference = 0.52±0.42 s, p<0.001, d = 1.24) and DS (mean difference = 1.29±1,77 s, p = 0.005, d = 0.73), with the Football+ showing superiority. In males, significant differences were found only for 20 m sprinting (mean difference = 0.06±0.09, p = 0.005, d = 0.60) and IA (mean difference = 0.74±0.46, p<0.001, d = 1.62), with the Football+ having superiority. Although practicable for injury prevention, the 11+ may not optimize acute performance and prepare players for high-intensity physical tasks as well as a well-structured, roughly intensive warm-up. Further gender-specific studies should evaluate the long-term effects of the Football+ on performance and injury prevention.



#2 Using Deadlifts as a Postactivation Performance Enhancement Strategy in Warm-ups in Football

Reference: J Strength Cond Res. 2023 Apr 19. doi: 10.1519/JSC.0000000000004485. Online ahead of print.

Authors: Eduardo Abade, João Brito, Bruno Gonçalves, Luís Saura, Diogo Coutinho, Jaime Sampaio

Summary: Postactivation performance enhancement activities may be relevant warm-up strategies aiming to improve subsequent physical performance. The purpose of the current study was to investigate the effects of adding barbell deadlift or hex-bar deadlift exercises to current warm-up routines on running and jumping performances in football players. Ten highly trained male football players participated in the study during the competitive phase of the season. All players performed 3 protocols in the same week: a standard warm-up that included players' regular routines and 2 other protocols with the addition of barbell or hex-bar deadlift, after the end of the warm-up (3 sets of 3 reps, progressing set by set from 60% to 85% repetition maximum). All protocols had the same time interval between pretest (immediately after the warm-up) and posttest (15 minutes after the warm-up). Vertical jumping (countermovement jump [CMJ]; Abalakov jump [AJ]) and running performances (505 test) were impaired 15 minutes after the standard warm-up (CMJ: -6.7 ± 4.2%; AJ: -8.1 ± 8.4%; and 505 time: 1.4 ± 2.5%). For warm-up with the addition of barbell deadlift, vertical jump increased by 4.3 ± 5.6% (Cohen's dunb: 0.23 [0.02-0.47]) and 505 time decreased by -5.9 ± 3.6% (Cohen's dunb: 0.97 [-1.68 to -0.43]). The warm-up with hex-bar deadlift led to trivial changes for CMJ and AJ, but 505 time decrease by -2.7 ± 2.6% (Cohen's dunb: -0.53 [-1.01 to -0.13]). The deadlift exercise can be added to warm-up routines to maintain or even enhance acute physical performance. However, coaches and practitioners should be aware that performance enhancements resultant from deadlift may vary according to individual physical profiles.



#3 Predictors of linear sprint performance in professional football players

Reference: Biol Sport. 2023 Apr;40(2):359-364. doi: 10.5114/biolsport.2023.114289. Epub 2022 Jun 1.

Authors: Joel Barrera, António J Figueiredo, João Duarte, Adam Field, Hugo Sarmento

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Summary: The purpose of this study was to analyze the relationship between sprint performance (time), and strength and power capabilities in football players. A total of 33 professional Portuguese football players performed isokinetic strength assessments, countermovement jumps (CMJ), squat jumps (SJ), and 10, 20 and 30 m sprints. Pearson's correlation (r) was used to determine the relationships between variables. Concentric knee extensor torque at 180° · s-1 was largely-to-very largely correlated with 10 m (r = -0.726), 20 m (-0.657) and 30 m sprints (r = -0.823). Moderate inverse correlation were observed between CMJ (r = -0.425 and r = -0.405) and SJ height (r = -0.417 and r = -0.430), and 20 m and 30 m sprint performance, respectively. Multiple linear regression combining KEcon 180° · s-1 and KFcon 180° · s-1 demonstrated that the model was significant for predicting 10 m sprint time (F (2, 8) = 5.886; R 2 = 0.595). The model combining SJ, CMJ and KEcon 180° · s-1 was also significant for predicting 20 and 30 m sprint times (F (3, 7) = 2.475; R 2 = 0.515 and F (3, 7) = 5.282; R 2 = 0.562; respectively). In conclusion, peak torque at higher velocities and vertical jump performance correlates significantly with linear sprint performance (time). For practitioners seeking to improve linear sprint performance in football players, evaluation of high speed strength and vertical jump indices should be undertaken.



#4 Mechanisms of ACL injuries in men's football: A systematic video analysis over six seasons in the Qatari professional league

Reference: Biol Sport. 2023 Apr;40(2):575-586. doi: 10.5114/biolsport.2023.118024. Epub 2022 Jul 21.

Authors: Raouf Nader Rekik, Roald Bahr, Flavio Cruz, Paul Read, Rod Whiteley, Pieter D'hooghe, Montassar Tabben, Karim Chamari

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Summary: To assess the mechanisms of ACL injury in male professional football players in Qatar across multiple seasons using systematic video analysis. 15 ACL injuries occurred in competition among the professional football teams that participated in an injury Surveillance Programme during 6 seasons (2013/2014 to 2018/2019). High-definition broadcast videos of these injuries were analyzed (49 views; 34 slow motion) by five analysts who independently described the injury mechanisms (situation, behavior, biomechanical characteristics) using validated observational tools. A knee valgus mechanism was observed in two-thirds of the cases (1 with direct contact to the knee, 3 with indirect contact (other body parts) and 6 with no contact). No visible valgus was reported in 2 of the direct knee contact injuries, while 3 cases of non-contact and indirect contact injuries were unclear. We observed 4 main categories of injury situation among those (n = 12) classified as non-contact/ indirect contact (multiple combinations were possible): pressing (n = 6), tackling or being tackled (n = 4), blocking (n = 3) and screening (n = 2). Direct contact injuries (n = 3) were suffered by 2 players during tackling and 1 whilst being tackled. Contact injuries represented only 20% of ACL injuries occurring during competition in Qatari professional soccer players. Independent of the playing situation, knee valgus was frequently observed (10/15 cases). Pressing was the most common situation (6/15 cases) leading to injury. Landing after heading was not reported in any of these ACL injuries.



#5 Time-loss and recurrence rates after lateral ankle ligament sprains in male elite football players: summary of a systematic review and meta-analysis

Reference: Sportverletz Sportschaden. 2023 Apr 19. doi: 10.1055/a-2047-9031. Online ahead of print. [Article in German]

Authors: Zacharias Flore, Karen Hambly, Kyra De Coninck, Götz Welsch

Summary: A literature search was conducted to systematically review and meta-analyse time-loss and recurrence rates of lateral ankle sprains (LAS) in male professional football players. Six electronic databases were screened separately for time-loss and recurrence rates after lateral ankle sprains in elite football players. A total of 13 (recurrence) and 12 (time-loss) studies met the previously defined inclusion criteria. The total sample size of the recurrence studies was 36.201 participants (44.404 overall initial injuries, 7944 initial ankle sprain (AS) injuries, 1193 recurrent AS injuries). 16.442 professional football players (4893 initial AS injuries, 748 recurrent AS injuries) were subsequently meta-analysed. A recurrence rate of 17.11% (95% CI: 13.31-20.92%; df=12; Q=19.53; I2=38.57%) was determined based on the random-effects model. A total of 7736 participants were part of the time-loss studies (35.888 total injuries, 4848 total ankle injuries; 3370 AS injuries). Out of the 7736 participants, 7337 participants met the inclusion criteria with a total of 3346 AS injuries. The average time-loss was 15 days (weighted mean: 15.92, median: 14.95, min: 9.55; max: 52.9). A priori, we determined considerable heterogeneity (CI: 18.15-22.08; df=11; Q=158; I2=93%). There is an average time-loss of 15 days per LAS and a recurrence rate of 17%. LAS is one of the most common types of injury with high recurrence rates in professional football players. The high recurrence rates and long-term consequences show the necessity for research in the field of LAS in elite football. However, heterogeneous data lead to difficulties regarding the aspect of comparability.



#6 Hamstring muscle injury in football players. Part 2 : preventive strategies

Reference: Rev Med Liege. 2023 Apr;78(4):213-217. [Article in French]

Authors: François Delvaux, Jean-Louis Croisier, Christopher Carling, Emmanuel Orhant, Jean-François Kaux

Summary: Prevention of hamstring injuries represents an important issue for football players and clubs. Preventive strategies can be effective if they include multiple dimensions and are well-structured. Five points appear essential in order to obtain a high-quality preventive strategy: progressive muscle strengthening, optimal workload management, lumbopelvic stability exercises, development of physical condition and optimization of sprint technique. While recognizing the limitations of preventive screening and the difficulty of predicting future injury, screening tests appear relevant for the identification of an individual risk profile for each footballer and in defining each player's work priorities. Finally, secondary prevention starts with the implementation of rigorous and high-level rehabilitation, as well as a special attention to players with a history of hamstring injury.



#7 SARS-CoV-2 serological assay and viral testing: a report of professional football setting

Reference: Postgrad Med J. 2022 Jul 1;98(1161):529-532. doi: 10.1136/postgradmedj-2021-140176.

Authors: Bahar Hassanmirzaei, Zohreh Haratian, Ali Ahmadzadeh Amiri, Amir Ahmadzadeh Amiri, Navid Moghadam

Summary: PCR is the current standard test for the diagnosis of SARS-CoV-2 infection. However, due to its limitations, serological testing is considered an alternative method for detecting SARS-CoV-2 exposure. In this study, we measured the level of SARS-CoV-2 IgM and IgG antibodies of male professional football players and compared the results with the standard PCR test to investigate the association between the two tests. Participants were male professional football players and team officials. Nasopharyngeal swabs and peripheral blood samples were collected for the PCR and serological tests, respectively. Also, previous records of COVID-19 testing and symptoms were gathered. Those with previous positive PCR tests who tested negative for the second time were considered to be recovered patients. Of the 1243 subjects, 222 (17.9%) were seropositive, while 29 (2.3%) tested positive for the SARS-CoV-2 PCR test. Sixty percent of symptomatic cases with a negative PCR were found to be seropositive. The mean level of IgM was significantly higher in PCR-positive and symptomatic subjects, whereas the recovered cases showed significantly higher levels of IgG. Our study revealed an inconsistency of results between the two tests; therefore, although application of serological assays alone seems insufficient in diagnosing COVID-19 disease, the findings are beneficial in the comprehension and the management of the disease.



#8 Beyond physical ability-predicting women's football performance from psychological factors

Reference: Front Psychol. 2023 Mar 28;14:1146372. doi: 10.3389/fpsyg.2023.1146372. eCollection 2023.

Authors: Susann Dahl Pettersen, Monica Martinussen, Bjørn Helge Handegård, Lene-Mari Potulski Rasmussen, Roman Koposov, Frode Adolfsen

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Summary: Even though there is a clear agreement among researchers that psychological factors are a vital part of a football player's performance, the topic has not been investigated thoroughly. The present study aimed to examine the predictive value of psychological factors on female football players' match performance. A sample of 156 players from the top two leagues in Norway completed the following questionnaires: Perceived Motivational Climate in Sport Questionnaire 2 (PMCSQ-2), Big Five Inventory (BFI-20), Self-Regulated Learning questionnaire, and Grit-S and Sport Mental Toughness Questionnaire (SMTQ). Match performance data were collected from the online database of the performance analysis company InStat. Results from a linear mixed model analysis showed that perceived mastery climate and extraversion were the only significant predictors of performance. Other relevant indicators, such as mental toughness, self-regulated learning, and grit, did not predict performance. These findings suggest that the team climate facilitated by coaches may be more important for predicting match performance than individual psychological factors.



#9 Verbal Encouragement Improves Game Intensity, Technical Aspects, and Psychological Responses During Soccer-Specific Training

Reference: Int J Sports Physiol Perform. 2023 Apr 28;1-7. doi: 10.1123/ijspp.2022-0435. Online ahead of print.

Authors: Okba Selmi, Danielle E Levitt, Bilel Aydi, Waad Ferhi, Anissa Bouassida

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Summary: Soccer match outcomes rely on technical accuracy, intensity of play, and athlete motivation, and these parameters can be developed during sport-specific practice such as during small-sided games (SSGs). Verbal encouragement as a coaching technique improves exercise intensity and athlete enjoyment (indicative of motivation), but the impact on technical performance alongside these critical parameters remains unknown. The aim was to examine the effects of verbal encouragement on technical performance, exercise intensity, and enjoyment during SSGs. Sixteen male youth soccer players (mean [SD]; age: 17.2 [0.4] y; height: 176.3 [7.0] cm; body mass: 68.0 [4.1] kg; body fat: 11.9% [2.2%]) completed 4 sessions of 4-per-side SSG without a goalkeeper. Two sessions were conducted as SSGs with verbal encouragement and 2 without verbal encouragement. Each SSG lasted 25 minutes (4 × 4-min work, 3-min passive recovery between bouts) on a 25 × 35-m pitch. Heart rate (HR) was continuously recorded, and rating of perceived exertion was collected after each SSG. Video analysis was used to quantify technical actions during SSG. Enjoyment was assessed after each SSG using the Physical Activity Enjoyment Scale. Paired t tests revealed that SSGs with verbal encouragement induced higher HR (% maximum HR and mean HR), rating of perceived exertion, and Physical Activity Enjoyment Scale score than SSGs without verbal encouragement (all P < .001, all d ≥ 0.92, large). Compared with SSGs without verbal encouragement, SSGs with verbal encouragement resulted in an increased percentage of successful passes (P < .001, d = 0.73, medium) and number of interceptions (P < .001, d = 0.89, large) and fewer lost balls (P < .001, d = 0.68, medium). Coaches should use verbal encouragement during SSGs to improve physical effort, technical performance, and psychological status in soccer players.



#10 Changes in Hematological Parameters of Iron Status and Total Iron Concentrations in Different Biological Matrices during a Sports Season in Women's Soccer Players

Reference: Nutrients. 2023 Apr 11;15(8):1833. doi: 10.3390/nu15081833.

Authors: Víctor Toro-Román, María C Robles-Gil, Ignacio Bartolomé, Francisco J Grijota, Diego Muñoz, Marcos Maynar-Mariño

Summary: Iron (Fe) metabolism and concentrations change during a sports season. Fe deficiency affects a significant number of women athletes. The aims of the present study were: (i) to analyze changes in hematological parameters of Fe status and (ii) to analyze changes in Fe concentrations in different biological matrices (serum, plasma, urine, erythrocytes, and platelets) during a sports season. Twenty-four Spanish semi-professional women's soccer players (23.37 ± 3.95 years) participated in the present study. Three assessments were performed throughout the sports season (beginning, middle and end of the season). Nutritional intake was evaluated and female hormones, hematological parameters of Fe status and Fe concentrations in plasma, serum, urine, erythrocytes and platelets were determined. There were no differences in Fe intake. Hemoglobin and mean corpuscular hemoglobin concentrations increased at the end of the season compared to initial values (p < 0.05). There were no significant changes in extracellular Fe concentrations (plasma, serum, and urine). However, erythrocyte Fe concentrations were lower at the end of the season (p < 0.05). Hematological parameters of Fe status and intracellular Fe concentrations change throughout the sports season in women's soccer players.



#11 The Association between Training Frequency, Symptoms of Overtraining and Injuries in Young Men Soccer Players

Reference: Int J Environ Res Public Health. 2023 Apr 11;20(8):5466. doi: 10.3390/ijerph20085466.

Authors: Filipe Rodrigues, Diogo Monteiro, Ricardo Ferraz, Luís Branquinho, Pedro Forte

Summary: Overtraining is a prevalent issue among young men soccer players, particularly those who are driven to enhance their skills. While an intense training volume and effort might contribute to athletic growth, it can also have negative implications, including injury. The current study aimed at examining the association between training frequency, symptoms of overtraining and injuries in young men soccer players. A path analysis approach was used to examine the causal relationships between variables. The sample consisted of 189 young men soccer players aged 13-17 years old (age = 14.81, SD = 1.37). Participants reported that they were training, on average, 5.77 days (SD = 1.53) per week. Athletes were competing at a regional (n = 100) or national (n = 89) level. Concerning injuries, participants indicated, on average, 2.03 (SD = 1.16) injuries since they started practicing soccer. The results displayed a significant association, as theoretically expected, namely: (i) training frequency was significantly associated with overtraining symptoms (β = 0.15 [IC95% = 0.01, 0.29]); (ii) overtraining symptoms were significantly associated with the number of injuries (β = 0.19 [IC95% = 0.02, 0.35]). An indirect effect between training frequency and injuries was also observed (β = 0.15 [IC95% = 0.01, 0.29]). Thus, there is preliminary evidence that overtraining symptoms could play a mediating role. In conclusion, investigating the links between overtraining symptoms and injury in young men soccer players is critical, as it can assist in identifying overtraining warning signs, promote young players' health and safety, customize training regimens to individual needs, and contribute to a better understanding of sports-related injuries.



#12 Ability of Countermovement Jumps to Detect Bilateral Asymmetry in Hip and Knee Strength in Elite Youth Soccer Players

Reference: Sports (Basel). 2023 Mar 31;11(4):77. doi: 10.3390/sports11040077.

Authors: Hailey L Wrona, Ryan Zerega, Victoria G King, Charles R Reiter, Susan Odum, Devon Manifold, Karyn Latorre, Timothy C Sell

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Summary: Clinicians frequently assess asymmetry in strength, flexibility, and performance characteristics as a method of screening for potential musculoskeletal injury. The identification of asymmetry in countermovement jumps may be an ideal method to reveal asymmetry in other lower extremity characteristics such as strength that otherwise may require additional testing, potentially reducing the time and burden on both the athlete and clinicians. The present study aims to examine the ability of asymmetry in both the single-leg and two-leg countermovement jump tests to accurately detect hip abduction, hip adduction, and eccentric hamstring strength asymmetry. Fifty-eight young male elite soccer players from the same professional academy performed a full battery of functional performance tests which included an assessment of hip adductor and abductor strength profiles, eccentric hamstring strength profiles, and neuromuscular performance and asymmetries during countermovement jumps. Bilateral variables attained from both the single-leg and two-leg countermovement jump tests included concentric impulse (Ns), eccentric mean force (N), and concentric mean force (N) computed by the VALD ForceDecks software. Average maximal force (N) was calculated bilaterally for the strength assessments. Asymmetry was calculated for each variable using 100 × |(right leg - left leg)/(right leg)| and grouped into three categories: 0 to <10%, 10% to <20%, and 20% or greater. Analyses were performed for the two higher asymmetry groups. The accuracy to detect strength asymmetry was assessed as the sensitivity, specificity, and predictive values for positive and negative tests. The outcomes from the accuracy assessments suggest that the single-leg countermovement jump concentric impulse variable at the 20% threshold is indicative of a youth male soccer player having hip adduction strength asymmetry while also demonstrating more accuracy and applicability than the two-leg countermovement jump concentric impulse variable.



#13 Relative Individual Sprint in Most Demanding Passages of Play in Spanish Professional Soccer Matches

Reference: Sports (Basel). 2023 Mar 23;11(4):72. doi: 10.3390/sports11040072.

Authors: Juan Ángel Piñero, Marcos Chena, Juan Carlos Zapardiel, Alberto Roso-Moliner, Elena Mainer-Pardos, Miguel Lampre, Demetrio Lozano

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Summary: The objective of this research was to analyse the most demanding passages (MDP) considering the sprint variable relative to the maximum level of sprint ability of each player as a function of player position, final outcome and part of the match during the competitive phase of a professional soccer season. Global positioning system (GPS) data were collected from 22 players according to their playing position in the last 19 match days of the Spanish La Liga professional soccer in the 2020/2021 season. MDP were calculated from 80% of the maximum sprint speed of each player. Wide midfielders covered the greatest distance at >80% of the maximum speed (2.4 ± 1.63 seg) and the longest duration (21.91 ± 13.35 m) in their MDP. When the whole team was losing, it demonstrated greater distances (20.23 ± 13.04 m) and longer durations (2.24 ± 1.58 seg) compared to games in which it was winning. When the team ended up drawing, the relative sprint distance covered in the second half was significantly greater than in the first (16.12 ± 21.02; SD = 0.26 ± 0.28 (-0.03/-0.54). Different demands of MDP, according to the sprint variable relative to the maximum individual capacity in competition, are required when contextual game factors are considered.



#14 Effect of Heading a Soccer Ball as an External Focus During a Drop Vertical Jump Task

Reference: Orthop J Sports Med. 2023 Apr 17;11(4):23259671231164706. doi: 10.1177/23259671231164706. eCollection 2023 Apr.

Authors: Hadi Akbari, Satoshi Kuwano, Yohei Shimokochi

Summary: Research has demonstrated that performing a secondary task during a drop vertical jump (DVJ) may affect landing kinetics and kinematics. The aim was to examine the differences in the trunk and lower extremity biomechanics associated with anterior cruciate ligament (ACL) injury risk factors between a standard DVJ and a DVJ while heading a soccer ball (header DVJ). Participants comprised 24 college-level soccer players (18 female and 6 male; mean ± SD age, 20.04 ± 1.12 years; height, 165.75 ± 7.25 cm; weight, 60.95 ± 8.47 kg). Each participant completed a standard DVJ and a header DVJ, and biomechanics were recorded using an electromagnetic tracking system and force plate. The difference (Δ) in 3-dimensional trunk, hip, knee, and ankle biomechanics between the tasks was analyzed. In addition, for each biomechanical variable, the correlation between the data from the 2 tasks was calculated. Compared to the standard DVJ, performing the header DVJ led to significantly reduced peak knee flexion angle (Δ = 5.35°; P = .002), knee flexion displacement (Δ = 3.89°; P = .015), hip flexion angle at initial contact (Δ = -2.84°; P = .001), peak trunk flexion angle (Δ = 13.11°; P = .006), and center of mass vertical displacement (Δ = -0.02m; P = .010), and increased peak anterior tibial shear force (Δ = -0.72 N/kg; P = .020), trunk lateral flexion angle at initial contact (Δ = 1.55°; P < .0001), peak trunk lateral flexion angle (Δ = 1.34°; P = .003), knee joint stiffness (Δ = 0.002 N*m/kg/deg; P = .017), and leg stiffness (Δ = 8.46 N/kg/m; P = .046) compared to those in standard DVJs. In addition, individuals' data for these variables were highly and positively correlated between conditions (r = 0.632-0.908; P < .001). The header DVJ task showed kinetic and kinematic parameters that suggested increased risk of ACL injury as compared with the standard DVJ task. Athletes may benefit from acquiring the ability to safely perform header DVJs to prevent ACL injury. To simulate real-time competition situations, coaches and athletic trainers should incorporate such dual tasks in ACL injury prevention programs.



#15 Kinematic parameters and metabolic power in elite soccer players: A small sided a large sided games comparison

Reference: Front Physiol. 2023 Apr 7;14:1150713. doi: 10.3389/fphys.2023.1150713. eCollection 2023.

Authors: Nemanja Zlojutro, Serdar Eler, Marko Joksimovic, Nebahat Eler, Saša Marković, Aleksandar Kukrić, Kosta Goranovic

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Summary: The goal of this paper is to determine what happens in one minute (on average) in kinematic parameters and metabolic power in small sided games (SSG) (3v3; 5v5) and large sided games (LSG) (10v10) and in which games kinematic parameters and metabolic power are best developed. The participants of this study were 22 professional football players, height 182.95±6.52 cm, mass 77.17±8.21 kg, body mass index (BMI) 22.97±1.47 kg/m2, body fat 9.85±2.55 %, aged 27.1±5.4 yrs, who played in the Premier League of Bosnia and Herzegovina. Data total distance (TD), maximum speed (MS), number of accelerations (nAcc), number of decelerations (nDec), number of sprints (nS), high intensity distance (Z4≥19.8 km/h), sprint distance (Z5≥25.2 km/h) and movements requiring a certain metabolic power (Pmet), were collected using a 20 Hz Global positioning system (GPS) system Pro2 (GPEXE, Exelio srl, Udine, Italy), on a total of 307 individual observations. The results showed that the average total distance was significantly higher in the 5v5 (135.16±18.78 m) and 10v10 (133.43±20.06 m) games (F=64.26, p<0.001) compared to the 3v3 (108.24±11.26 m). Furthermore, the values of the variables Z4 (8.32±3.38 m, F=97.59), Z5 (1.84±1.53 m, F=123.64), nS (0.13±0.10 n, F=96.14) as well as Maxspeed (27.06±1.90 km/h, F=139.33), are statistically significantly higher (p<0.001) in the 10v10 game compared to the other two game formats. The average number of nAcc (0.40±0.32 n, F=9.86, p<0.001) and nDec (0.62±0.36 n, F=6.42, p<0.001) is statistically significantly higher in the 5v5 game. The results showed that the 5v5 game is significantly more metabolically demanding Pmet (2.76±0.67 W•kg-1, F=66.08, p<0.001) compared to the other two game formats. The data presented in this paper can be used as a basis for the construction of specific exercises based on kinematic and physiological requirements, and for planning and programming microcycles in football.



#16 Septic retrocalcaneal bursitis in a young soccer player treated with hindfoot endoscopic bursectomy: a case report

Reference: J Surg Case Rep. 2023 Apr 19;2023(4):rjad169. doi: 10.1093/jscr/rjad169. eCollection 2023 Apr.

Authors: Morimoto Shota, Tachibana Toshiya, Iseki Tomoya

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Summary: Septic retrocalcaneal bursitis (RB) is extremely rare with no reports on surgical treatment. Here, we describe a rare case of septic RB in a 14-year-old male soccer player who was treated with hindfoot endoscopic bursectomy. A 14-year-old male soccer player complained of right heel pain without trauma histories when he was playing a soccer. Based on physical examination, radiological findings and laboratory results, we diagnosed the patient with septic RB and started to treat with conservative treatment including a non-weightbearing splint and intravenous antibiotics therapy. However, his symptoms and laboratory results did not improve at 4 days after starting intravenous antibiotics therapy, and so we applied hindfoot endoscopic bursectomy for him. At 4 weeks after the surgery, he could return to the original sport at preinjury level without symptoms and complications. Septic RB in a 14-year-old male soccer player was successfully treated with hindfoot endoscopic bursectomy.



#17 Identifying Soccer Teams' Styles of Play: A Scoping and Critical Review

Reference: J Funct Morphol Kinesiol. 2023 Mar 30;8(2):39. doi: 10.3390/jfmk8020039.

Authors: Spyridon Plakias, Serafeim Moustakidis, Christos Kokkotis, Themistoklis Tsatalas, Marina Papalexi, Dionysios Plakias, Giannis Giakas, Dimitrios Tsaopoulos

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Summary: Identifying and measuring soccer playing styles is a very important step toward a more effective performance analysis. Exploring the different game styles that a team can adopt to enable a great performance remains under-researched. To address this challenge and identify new directions in future research in the area, this paper conducted a critical review of 40 research articles that met specific criteria. Following the 22-item Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines, this scoping review searched for literature on Google Scholar and Pub Med database. The descriptive and thematic analysis found that the objectives of the identified papers can be classified into three main categories (recognition and effectiveness of playing styles and contextual variables that affect them). Critically reviewing the studies, the paper concluded that: (i) factor analysis seems to be the best technique among inductive statistics; (ii) artificial intelligence (AI) opens new horizons in performance analysis, and (iii) there is a need for further research on the effectiveness of different playing styles, as well as on the impact of contextual variables on them.



#18 The seven phases of match status differentiate the running performance of soccer players in UEFA Champions League

Reference: Sci Rep. 2023 Apr 24;13(1):6675. doi: 10.1038/s41598-023-33910-9.

Authors: Marek Konefał, Łukasz Radzimiński, Jan Chmura, Toni Modrić, Michał Zacharko, Alexis Padrón-Cabo, Damir Sekulic, Sime Versic, Paweł Chmura

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Summary: The purpose of this research was to investigate the running performance of professional soccer players in relation to seven phases which resulted in the changing or maintaining the match status in the UEFA Champion League games during season 2020/2021. Moreover, we aimed to define which match status phases occur at the earliest stage of regular game time. This study involved professional soccer players from 24 teams participating in the group stage of UEFA Champions League in season 2020/21. The match status was divided into seven phases that result in changing or maintaining the match outcome: DW (Drawing to Winning); LD (Losing to Drawing); WW (Winning to Winning); DD (Drawing to Drawing); LL (Losing to Losing); DL (Drawing to Losing); WD (Winning to Drawing). Such running performance variables as: total distance covered (TDC) and distance covered in high-intensity running (HIR) were analyzed. Players participating in the UEFA Champions League matches cover the longest TDC in DW, DL and DD phases. TDC in these stages was between 111 and 123 m min-1. The highest HIR was recorded during phases: DW, DL and LL (range between 9.91 and 10.82 m min-1). In contrast, the lowest total distance and distance in HIR is covered during WD phase (only 105.57 ± 1.89 m min-1 and 7.34 m min-1 respectively). On average, phases resulting in the change of the match status occur during the first half, while all phases maintaining the result in the second half. Coaching staffs should consider registering and analysing the physical match performance in relation to described seven match status phases. Such information allows to prepare team-specific training drills, that players should perform more often in order to change or maintain the status of the game.






Effect of a Four-Week Soccer Training Program Using Stressful Constraints on Team Resilience and Precompetitive Anxiety

The present study examined the effects of stressful constraints during soccer trainings on psychological skill development and internal load when compared with control (non-stressful) trainings.





Monitoring training load in youth players: effects of a six-week training program and the association between external and internal loads

This study examined the effects of a six-week preparatory training program on physical performance and physiological adaptations in junior soccer players. Additionally, we investigated whether a relationship existed between external and internal loads.





Player loans in football

The temporary transfer of players is practiced regularly in professional football. It is used to allow the development of young players who do not yet have sufficient playing experience or a good enough sporting level to play in their owner club.

This suggests that players that are on loan are relatively young and probably younger than the rest of the squad. Indeed, players on loan are on average younger (24.41 years of age) than footballers belonging to employer teams (26.54 years). The most represented age group of players on loan is 22 years of age. Loans, however, by no means just involve footballers at the start of their career. Indeed, only 27.9% of the total number of players on loan are 21 years of age or under, while almost half (47.9%) are 24 or over.



The considerable percentage of relatively experienced players among those on loan indicates that this strategy is not uniquely used with the aim of developing the potential of young players. Several other objectives of clubs could be:

  • making room in squads
  • relaunching unused players irrespective of their age
  • limiting the sporting and financial risks linked to permanent transfers
  • acquiring reinforcements without transfer indemnities by just paying the players’ salary, and often even just a part of it, or none at all.

 Contrary to what one might have thought, the percentage of players on loan is higher for players aged between 22 and 25 (13.4%) than among footballers aged 21 or under (12.7%). After having signed their first professional contract and having become part of the first team squad of their owner club, many players do not find their place and are loaned out to other teams, which is often a prelude to a permanent departure.



Having the initial purpose of loaning players for development "debunked", having a closer look from the top down seems appropriate.  

The percentage of players on loan varies considerably according to league. The greatest percentages were observed in the two highest levels of Italian competitions: the Serie A (19.0%) and the Serie B (22.8%). The proportion of players on loan is also high in the Spanish second division, as well as in the third and fourth English divisions.



The presence at the top of the rankings of several lower level championships of associations with well-established leagues indicates the tendency of the most developed clubs to offer contracts to more players than they actually need, by relying on less competitive teams to nurture their development. This strategy is also widespread within clubs of the Argentinean top division (28 clubs).

Slicing further down and onto the club level, it can be seen that the record high in the percentage of players on loan was measured for Buenos Aires’s Barracas Central (50.0%). Frosinone Calcio, as one of the top sites in Serie B scores also very high (48,3%). Besides the given Italian teams, Girona FC (ESP) and  Schalke 04 (GER) are also from the Big5 leagues. Generally, the strategy of taking players on loan from top clubs has both advantages, such as having players at its disposal that would otherwise be inaccessible, and disadvantages, such as the constant rotation of squads.



Numerous BIG5 league teams figure among the clubs loaning out the most players present on the 1st March in the 75 leagues analysed. Arsenal tops the list with 25 footballers loaned out, followed by the Italians of Atalanta.


Eight English clubs are in the top20 places, which probably reflects the economic strength of the Premier League. 


The recent limits placed on international loans for players over 21 years of age by the FIFA specifically target the wealthiest clubs and aim at preventing them from hoarding too many players. While the limits introduced can effectively function as a deterrent, many of the clubs who are particularly active in loaning out players now turn towards a strategy of multi-ownership. The latter consists of taking over other clubs, usually abroad, where they can place footballers without having to loan them out.



Analysing the level of competition the players are loaned to make is another topic of interest. In 63.5% of cases, the clubs where players are loaned have a lower sporting level to the owner clubs. In 20.9% of instances, the level is equivalent, while players on loan to more competitive teams only account for 15.5% of total loans. This result confirms that loans principally serve the interests of the wealthiest clubs, by allowing them to control the career of more players than they could have in their squad and develop.



Last but not least, having a look on positions makes it clear that Forwards (13.1%), followed by Midfielders (9,1%), are the two most likely positions that are loaned out, while goalkeepers are the least likely (6,2%).



Poli R, Ravenel L & Besson R. Global analysis of player loans. CIES Football Observatory Monthly Report, 2023, 3/83.





Warm-up optimization in male soccer players: A comparison of SSG and traditional warm-up routines on physical fitness qualities

The aim of this study was to compare the effects of small-sided soccer games (SSSGs) and traditional warm-up (TWU) routines on physical fitness qualities in soccer players.





Contextualised high-intensity running profiles of elite football players with reference to general and specialised tactical roles

The present study aimed to contextualise physical metrics with tactical actions according to general and specialised tactical roles.





Latest research in football - week 13 - 2023

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 Successful Repair of M. obliquus Internus Abdominis Avulsion at the Iliac Crest-Operative Technique in Professional Soccer Players

Reference: Orthop Surg. 2023 Apr 11. doi: 10.1111/os.13699. Online ahead of print.

Authors: Heinz Lohrer, Andreas Höferlin

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Summary: Sports related injuries to the anterolateral abdominal wall have been described as side strain injuries or hip pointer. So far, only a few cases of avulsion injuries of the m. obliquus internus abdominis muscle from the iliac crest have been described. All were treated conservatively. The aim of this study is to present the surgical technique. This report presents three cases of professional soccer players who were treated surgically with transosseous reattachment to the iliac crest. These male players were 23, 25, and 29 years old. Two of them suffered a direct contusion and one an indirect injury. The diagnosis was suspected based on the patient's history and clinical examination and confirmed by MRI. In each case, the fibrocartilaginous layer of the m. obliquus internus was separated 2 cm from the iliac crest. All three players were operated by aponeurotic m. obliquus internus refixation to the lateral iliac crest (three transosseous drill holes). Return to play was 55, 60, and 122 days postoperatively. Functional limitations, symptoms, sports/recreational activities, and quality of life in terms of occupational, social, emotional, and lifestyle concerns were measured using the iHOT 12 instrument at 11.1 and 9.7 years postoperatively. Six weeks postoperatively, sport-specific training was started. After 2 to 4 months, all three patients were fully reintegrated into their elite sports and unrestricted sports ability was achieved. Long-term follow-up was performed using the German version of the iHOT-12 questionnaire and 92.7% and 99.9% were calculated for the two German speaking soccer players. Our cases demonstrate that transosseous suture reattachment was a successful procedure that allowed a safe and predictable return to sport. Full performance and excellent, long lasting treatment results were achieved.



#2 Prevalence and diagnostic significance of de-novo 12-lead ECG changes after COVID-19 infection in elite soccer players

Reference: Heart. 2023 Mar 27;heartjnl-2022-322211. doi: 10.1136/heartjnl-2022-322211. Online ahead of print.

Authors: Raghav T Bhatia, Aneil Malhotra, Hamish MacLachlan, Sabiha Gati, Sarandeep Marwaha, Nikhil Chatrath, Saad Fyyaz, Haroldo Aleixo, Samar Al-Turaihi, Aswin Babu, Joyee Basu, Paul Catterson, Robert Cooper, Joelle J N Daems, Harshil Dhutia, Filipe Ferrari, Juliette C van Hattum, Zafar Iqbal, Alexandros Kasiakogias, Antoinette Kenny, Tamim Khanbhai, Shafik Khoury, Chris Miles, David Oxborough, Kashif Quazi, Dhrubo Rakhit, Anushka Sharma, Amanda Varnava, Maria Teresa Tome Esteban, Gherardo Finocchiaro, Ricardo Stein, Harald T Jorstad, Michael Papadakis, Sanjay Sharma

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Summary: The efficacy of pre-COVID-19 and post-COVID-19 infection 12-lead ECGs for identifying athletes with myopericarditis has never been reported. We aimed to assess the prevalence and significance of de-novo ECG changes following COVID-19 infection. In this multicentre observational study, between March 2020 and May 2022, we evaluated consecutive athletes with COVID-19 infection. Athletes exhibiting de-novo ECG changes underwent cardiovascular magnetic resonance (CMR) scans. One club mandated CMR scans for all players (n=30) following COVID-19 infection, despite the absence of cardiac symptoms or de-novo ECG changes. 511 soccer players (median age 21 years, IQR 18-26 years) were included. 17 (3%) athletes demonstrated de-novo ECG changes, which included reduction in T-wave amplitude in the inferior and lateral leads (n=5), inferior leads (n=4) and lateral leads (n=4); inferior T-wave inversion (n=7); and ST-segment depression (n=2). 15 (88%) athletes with de-novo ECG changes revealed evidence of inflammatory cardiac sequelae. All 30 athletes who underwent a mandatory CMR scan had normal findings. Athletes revealing de-novo ECG changes had a higher prevalence of cardiac symptoms (71% vs 12%, p<0.0001) and longer median symptom duration (5 days, IQR 3-10) compared with athletes without de-novo ECG changes (2 days, IQR 1-3, p<0.001). Among athletes without cardiac symptoms, the additional yield of de-novo ECG changes to detect cardiac inflammation was 20%. 3% of athletes demonstrated de-novo ECG changes post COVID-19 infection, of which 88% were diagnosed with cardiac inflammation. Most affected athletes exhibited cardiac symptoms; however, de-novo ECG changes contributed to a diagnosis of cardiac inflammation in 20% of athletes without cardiac symptoms.



#3 Correlations Between Hamstring Muscle Architecture, Maturation, and Anthropometric Measures in Academy Soccer Players

Reference: Int J Sports Physiol Perform. 2023 Apr 14;1-10. doi: 10.1123/ijspp.2022-0031. Online ahead of print.

Authors: Matthew Brown, Martin Buchheit, Mathieu Lacome, Karim Hader, Gaël Guilhem

Summary: Muscle architecture is associated with motor performance and muscle injury. While muscle architecture and knee-flexor eccentric strength change with growth, the influence of anthropometric measures on these properties is rarely considered. This study aimed to investigate the relationship between hamstring muscle architecture and knee-flexor eccentric strength with anthropometric measurements. Sixty male footballers (16.6 [1.05] y) from the U16, U17, and U19 teams of an elite soccer club were included in this study. Fascicle length, pennation angle, and muscle thickness of the biceps femoris long head (BFlh) and semimembranosus muscles were measured in both legs using ultrasound. Knee-flexor eccentric strength, height, body mass, leg length, femur length, and peak height velocity (PHV) were measured within 1 week of the ultrasound images. A stepwise regression and 1-way analysis of variance tests were used to evaluate the effects of age, maturity, and anthropometric measurements on muscle properties. Variance within BFlh and semimembranosus muscle thickness (r < .61), semimembranosus pennation angle (r < .58), and knee-flexor eccentric strength (r = .50) were highly related to body mass. We observed no significant correlations between muscle architecture and age (P > .29). However, moderately greater BFlh muscle thickness was shown for the post-PHV compared with the PHV group (effect size ± 90% CI: 0.72 ± 0.49). In conclusion, weak correlations between muscle architecture and anthropometric measurements suggest that other factors (ie, genetics, training regimen) influence muscle architecture. The moderate effect of maturity on BFlh muscle thickness strongly suggests post-PHV hypertrophy of the BFlh muscle. Our results confirmed previous findings that eccentric knee-flexor strength is influenced by body mass.



#4 External and internal training load comparison between sided-game drills in professional soccer

Reference: Front Sports Act Living. 2023 Apr 4;5:1150461. doi: 10.3389/fspor.2023.1150461. eCollection 2023.

Authors: Marco Beato, Kevin L de Keijzer, Andrew J Costin

Summary: This study aims to quantify and compare the external and internal training load demands of sided-game drills in professional team players during the competitive season. Twenty-four male professional soccer players of the same club were enrolled in this study. Drills were categorized as large-sided games (LSG): 10vs10 (84 × 60 m or 72 × 60 m), Hexagon possession 9vs9 + 3 (36 × 48 m), Possession gate 8vs8 + 2 (36 × 44 m), Possession 7vs7 + 3 (30 × 32 m) or as Small-sided games (SSG): 6vs6 (48 × 42 m), and Possession 6vs4 (30 × 60 m). A total of 7 drills and 279 individual data points were included in this analysis. Distance covered, high-speed running (HSR), and sprinting distance were all calculated in meters per minute (m.min-1) while total accelerations (>3 m.s-2) and total decelerations (- < 3 m.s-2) were calculated in number of actions per minute (n.min-1). All external load was measured with global navigation satellite systems (GNSS) STATSports Apex units. Players' internal load was quantified using their rating of perceived exertion (RPE). We found that distance covered (p < 0.01, large), HSR (p < 0.01, large), and sprinting distance (p < 0.01, large) changed between drills (e.g., greater in LSG formats), acceleration (p < 0.01, large) and deceleration (p < 0.01, large) demands were greater in smaller formats (e.g., SSG 6vs6, and Possession 6vs4), while RPE was lower in the Possession gate 8vs8 + 2 format (p < 0.01, large). This study found that sided-games can replicate and sometimes exceed some match-specific intensity parameters, however, HSR and sprinting were consistently lower compared to official matches.



#5 Development and Predictive Validation of the Brazilian Adductor Performance Test for Estimating the Chance of Hip Adductor Injuries in Elite Soccer Athletes

Reference: Int J Sports Physiol Perform. 2023 Apr 20;1-7. doi: 10.1123/ijspp.2022-0306. Online ahead of print.

Authors: Jeffeson Hildo Medeiros de Queiroz, João Paulo Frota, Filipe Abdala Dos Reis, Rodrigo Ribeiro de Oliveira

Summary: To develop and validate the Brazilian Adductor Performance Test (BAPT) for predicting hip adductor muscle injuries in elite soccer athletes. A total of 108 soccer athletes were assessed, followed up for 3 months, and evaluated for a history of adductor injury 6 months before BAPT evaluation. The Shapiro-Wilk test was used as the normality test. The Mann-Whitney U test was used to compare BAPT scores between injured and uninjured athletes. Binary logistic regression was performed to identify the athletes' chances of injury based on their BAPT scores. A receiver operating characteristic curve was used to determine the cutoff point for the number of repetitions in the BAPT and Spearman bivariate correlation and identify factors potentially related to the test score. Furthermore, the intraclass correlation coefficient was used to determine interexaminer agreement. The level of significance was set at 95%.The BAPT scores for hip adductor injury history did not differ significantly (P = .08). A significant deficit was identified in the BAPT scores of the injured athletes at the 3-month follow-up (P = .001). The cutoff point identified was 33 repetitions. Low BAPT scores increased the chance of injury by 20% (odds ratio, 1.20%; P = .001). The interexaminer agreement was .96 (P = .001). BAPT can be used to identify athletes most likely to sustain hip adductor muscle injuries, indirectly reducing the rate of this injury in soccer clubs.



#6 The influence of ball in/out of play and possession in elite soccer: Towards a more valid measure of physical intensity during competitive match-play

Reference: Eur J Sport Sci. 2023 Apr 20;1-23. doi: 10.1080/17461391.2023.2203120. Online ahead of print.

Authors: Benjamin W C Jerome, Michael Stoeckl, Ben Mackriell, Thomas Seidl, Christian W Dawson, Daniel T P Fong, Jonathan P Folland

Summary: The physical demands of soccer match-play have typically been assessed using a low-resolution whole match approach ignoring whether the ball is in or out of play (BIP/BOP) and during these periods which team has possession. This study investigated the effect of fundamental match structure variables (BIP/BOP, in/out of possession) on the physical demands, and especially intensity, of elite match-play. For 1083 matches from a major European league, whole match duration, and player physical tracking data, were divided into BIP/BOP, and in/out of possession periods throughout the match, using on-ball event data. These distinct phases were used to derive absolute (m) and rate (m·min-1) of distance covered in total and within six speed categories during BIP/BOP and in/out possession. The rate of distance covered, an index of physical intensity, was >2-fold greater during BIP vs BOP. Whole match total distance covered was confounded by BIP time and poorly associated with physical intensity during BIP (r=0.36). Whole match rates of distance covered substantially underestimated those during BIP, particularly for higher running speeds (∼-62%). Ball possession markedly effected physical intensity, with the rates of distance covered running (+31%), at high-speed (+30%) and in total (+7%) greater out than in possession. Whole match physical metrics underestimated the physical intensity during BIP, and thus the rate(s) of distance covered during BIP are recommended for accurate measurement of physical intensity in elite soccer. The greater demands of being out of possession supports a possession based tactical approach to minimise fatigue and its negative consequences.



#7 Effects of 6 weeks in-season flywheel squat resistance training on strength, vertical jump, change of direction and sprint performance in professional female soccer players

Reference: Biol Sport. 2023 Apr;40(2):521-529. doi: 10.5114/biolsport.2023.118022. Epub 2022 Jul 21.

Authors: Javier Pecci, Alejandro Muñoz-López, Paul A Jones, Borja Sañudo

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Summary: Flywheel resistance training devices (FRTD) is shown effective in improving strength, sprinting, jumping and changes of direction (COD) performance in male soccer players, however, this is not elucidated in female soccer players. We aimed to assess the effect of FRTD on these physical abilities in females soccer players. 24 professional female soccer players (age: 20.4 ± 2.6 years) were randomly assigned to a flywheel training group (FWTG) that trained twice a week for 6 weeks on a rotary inertia device with an initial volume of 3 sets of 6 repetitions and an inertia of 0,025 kg · m-2, increasing intensity and volume or a control group (CG) that did not performed any additional resistance training program. Concentric peak torque of the knee extensors (CONEXT) and flexors (CONFLEX), eccentric peak torque of the knee extensors (ECCEXT) and flexors (ECCFLEX) at 60° · s-1 on an isokinetic dynamometer, countermovement jump (CMJ) height, COD and 30-metres sprint were assessed. Significant time by group interactions were found in CONEXT (p = 0.002; η²p = 0.425), CONFLEX (p = 0.037; η²p = 0.22), ECCEXT (p = 0.002; η²p = 0.43) and ECCFLEX (p = 0.008; η²p = 0.334). No time by group effect was found in CMJ (p = 0.061; η²p = 0.182), COD (p = 0.067; η²p = 0.184) or sprint (p = 0.926; η²p = 4.979 · e-4). In conclusion, 6 weeks of flywheel squat training improved strength (especially eccentric strength) but not soccer-specific abilities such as jumping, changing of direction or sprinting in professional soccer players.



#8 Recovery time variation during sprint interval training impacts amateur soccer players adaptations - a pilot study

Reference: Biol Sport. 2023 Apr;40(2):417-424. doi: 10.5114/biolsport.2023.116008. Epub 2022 Jun 1.

Authors: Gürkan Diker, Abdulkerim Darendeli, Karim Chamari, Alexandre Dellal, Sürhat Müniroğlu, Sadi Ön, Hüseyin Özkamçı

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Summary: The objective of the present study was to investigate the selected performance adaptations of amateur soccer players to 2 different running-based sprint interval training (SIT) protocols with different recovery intervals and work-rest ratios (1:5 & 1:1). Twenty-three subjects (age 21.4 ± 1.1 years; height 175.4 ± 4.7 cm; body mass 69 ± 6.4 kg) participated in the study. Before the 6-weeks training period, participants completed 3-weeks of low-intensity training preparation. Subsequently, the pre-tests (anthropometric measurements, repeated sprint test [12 × 20-m with 30-s recovery intervals], Yo-YoIRT1 & Yo-YoIRT2 and treadmill VO2max test) were conducted. Thereafter, participants were randomly divided into 3 sub-groups (1 - SIT with 150 s recovery intervals [SIT150, n = 8]; 2 - SIT with 30 s recovery intervals [SIT30, n = 7]; and 3 - control group [CG, n = 8]). SIT150 and SIT30 training groups completed sprint interval training (2-days/week; 30-s all-out running, 6-10 repetition with 150 s recovery intervals for SIT150 and 30 s for SIT30 groups, respectively), a soccer match (1-day) and routine soccer training (3-days) per week. The CG attended only routine training sessions and the soccer-match (4-days). The study experiments and the trainings were conducted during off-season. Yo-YoIRT1, Yo-YoIRT2, and VO2max were significantly improved both in SIT30 and SIT150 (p < 0.05) groups. Yo-YoIRT1 and VO2max were also significantly improved in CG (p < 0.05). Both the SIT150 and SIT30 training were shown to improve Yo-YoIRT1, Yo-YoIRT2 and VO2max performance compared to the control group, nevertheless, SIT150 was more efficient in improving the Yo-YoIRT1, Yo-YoIRT2 than SIT30. The authors of this study suggest using SIT150 to induce more effective performance outputs in amateur soccer players.



#9 Is there any relationship between match running, technical-tactical performance, and team success in professional soccer? A longitudinal study in the first and second divisions of LaLiga

Reference: Biol Sport. 2023 Apr;40(2):587-594. doi: 10.5114/biolsport.2023.118021. Epub 2022 Sep 6.

Authors: José M Oliva-Lozano, Helena Martínez-Puertas, Víctor Fortes, Roberto López-Del Campo, Ricardo Resta, José M Muyor

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Summary: The aim of this study was to analyze the association between teams' success at the end of the season and match running, and technical-tactical performance in two professional soccer leagues. Match running, and technical-tactical performance data were collected during two consecutive seasons. A Factor Analysis was conducted to reduce the number of performance variables into a fewer number of factors. The scree plot with parallel analysis revealed that five factors should be retained. Then, a multiple linear regression analysis was performed to explain which variables and factors were more associated with teams' success at the end of the season. The main findings of this study were that factor 3, which was correlated with goals scored, possessions ending with a goal, shots on target, goals from set plays, goals from a direct free kick, offsides, and goals conceded, was the most important contributor to teams' success (β = 0.66). In addition, this study observed a significant interaction (p = 0.001) between the second division of LaLiga and factor 2, which correlated with total distance (TD), sprinting distance (SPD), and sprinting actions (SPA) when opponent team owns the ball, tackles, shots inside the box, and fouls received. This implies that factor 2 had a different effect on the total points at the end of the season depending on the league. However, factor 2 had no effect on the first division. In conclusion, technical-tactical performance variables were usually more closely linked to the team's success in both leagues than match running performance data. Regarding the technical-tactical performance, teams may focus on drills that promote goal situations, shooting accuracy, the total of shots performed in match play, and set pieces. However, defensive skills need to be reinforced considering the importance of goals conceded for team success in both divisions. When it comes to the match running performance, teams are encouraged to focus on offensive actions, in which they possess and run with the ball (especially at high speed) and defensive actions in which the players perform continuous and high-intensity physical efforts to prevent the opponents from scoring, avoid counterattacks, stay compact, and defend the area and goal.



#10 Factors affecting match running performance in elite soccer: Analysis of UEFA Champions League matches

Reference: Biol Sport. 2023 Apr;40(2):409-416. doi: 10.5114/biolsport.2023.116453. Epub 2022 Jun 1.

Authors: Toni Modric, Sime Versic, Marko Stojanovic, Paweł Chmura, Marcin Andrzejewski, Marek Konefał, Damir Sekulic

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Summary: This study aimed to examine the independent effect of different match-related factors on match running performance (MRP) in elite soccer. Players' MRPs (n = 244) were collected during UEFA Champions League (UCL) group stage matches in the 2020-21 season. All MRP data were collected by the semi-automatic optical system InStat Fitness (InStat Limited, Limerick, Republic of Ireland). Match-related factors included match outcome, team quality, match location, opponent quality and difference in team quality, while MRP included cumulative and relative measures of total distance (TD and R-TD), low-intensity running (LIR and R-LIR) (≤ 4 m/s), moderate-intensity running (MIR and R-MIR) (4-5.5 m/s) and high-intensity running (HIR and R-HIR) (≥ 5.5 m/s). Linear mixed models were used to examine the collective effect of match-related factors on MRPs when controlling for between-player, between-playing position and between-team variation. The main findings were that match outcome was associated with reduced HIR (d = -0.38, p = 0.04), match location was associated with increased TD, R-TD, LIR and R-LIR (d = 0.54-0.87, all p < 0.01), while team quality, opponent quality and difference in team quality were not associated with MRP. These results show that (i) winning UCL matches was not strongly influenced by players' physical performance, (ii) away UCL matches were characterized by a slower match pace and greater match volume, and (iii) players' physical performance was similar irrespective of playing either in or against high- or low-quality teams. The findings from this study may help soccer coaches to ensure optimal physical preparation of players in elite soccer.



#11 Effects of re-warm-up protocols on the physical performance of soccer players: A systematic review with meta-analysis

Reference: Biol Sport. 2023 Apr;40(2):335-344. doi: 10.5114/biolsport.2023.116013. Epub 2022 Jun 1.

Authors: Francisco Tomás González Fernández, Hugo Sarmento, Álvaro Infantes-Paniagua, Rodrigo Ramirez-Campillo, Sixto González-Víllora, Filipe Manuel Clemente

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Summary: This systematic review aimed to (1) identify and summarize studies that have examined the effects of re-warm-up (RWU) protocols on the physical performance of soccer players (vertical jump height and sprint time) and (2) establish a meta-comparison between performing a re-warm-up and not performing one regarding the outcomes of the aforementioned outcomes. A systematic review of EBSCO, PubMed, SciELO, SPORTDiscus, and Web of Science databases was performed on 12 January, 2021, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. From the 892 studies initially identified, four studies were reviewed, and three of these were included in the present meta-analysis. Compared to a control condition, there was a moderate effect of RWU on vertical jump height (ES = 0.66; p = 0.001; I2 = 0.0%). However, compared to a control condition, there was a trivial effect of RWU on linear sprint time (ES = 0.19; p = 0.440; I2 = 38.4%). The nature of RWU enhances the performance of players with an emphasis on actions requiring vertical jumps. Therefore, the results provide essential information that soccer coaching staff can use to improve the performance of their teams. The limited number of studies available for the meta-analysis may have magnified the impact of heterogeneity on linear sprint time findings. More high-quality studies, with homogeneous study designs, may help to clarify the potential benefits of RWU for linear sprint time.



#12 Monitoring physical match performance relative to peak locomotor demands: implications for training professional soccer players

Reference: Biol Sport. 2023 Apr;40(2):553-560. doi: 10.5114/biolsport.2023.116450. Epub 2022 Jul 21.

Authors: José M Oliva-Lozano, Andrea Riboli, Víctor Fortes, José M Muyor

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Summary: This study aimed to analyse physical performance relative to peak locomotor demands of match play. Data were collected during 13 professional soccer matches. Initially, the 1-minute peak values were registered in each match, including the percentage of the total distance (TD), high-speed running distance (HSRD), sprinting distance (SPD), and high-metabolic load distance (HMLD), and a total of high-intensity accelerations and decelerations (Acc+Dec). Secondly, the time (measured in minutes) spent at different percentage ranges for the 1-minute peak values registered in each match was calculated. Thirdly, the physical performance required in the different percentage ranges for the 1-minute peak values were obtained. Finally, the time and physical performance required above the 90-minute average demands were calculated. The 90-minute average for all playing positions represented ~53% of the total distance (TD), ~23.4% of high-metabolic load distance (HMLD), ~16% of high-speed running distance (HSRD), ~11% of the total of high-intensity accelerations and decelerations (Acc+Dec), and ~6% of sprinting distance (SPD) for the 1-minute peak values. Likewise, statistically significant differences (p < 0.05) in the physical performance and time spent between specific percentage ranges for the 1-minute peak locomotor demands were also noted. In addition, all the variables reported that the physical performance required for above 90-minute average demands were significantly greater (p < 0.05) than the 90-minute average demands. Therefore, these findings may guide the prescription of training intensity by considering the physical performance relative to the peak locomotor demands of match play.



#13 Talent concentration and competitive imbalance in European soccer

Reference: Front Sports Act Living. 2023 Mar 30;5:1148122. doi: 10.3389/fspor.2023.1148122. eCollection 2023.

Authors: Bernd Frick, Tommy Kweku Quansah, Markus Lang

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Summary: While most of the available literature on competitive balance analyses its impact on ticket sales and TV audiences, less empirical research is available that examines the observable variation in competitive balance across leagues and over time. This paper studies the concentration of player talent and end-of-season league points to empirically assess whether leagues with a more equal distribution of player talent produce a more balanced competition than leagues with less equal distribution. The longitudinal data we use to estimate our empirical model comes from professional soccer leagues in twelve Western European countries from 2005/06 thru 2020/21, yielding 5,299 club-season observations. Our empirical analysis indicates that talent concentration in a league significantly and positively impacts points concentration in that league. However, in specifications controlling for year, country, and division, this impact is only weakly significant or insignificant, suggesting that talent concentration does not significantly affect competitive balance in that league. Additionally, our findings demonstrate that the relationship between talent and points concentration does not vary considerably across the European leagues or over time. Our results suggest that repeated participation in the UEFA Champions League, with its considerable monetary returns by (more or less) the same subset of teams, does not increase competitive imbalance in the respective national league. Thus, with relatively few additional regulatory interventions, the promotion and relegation system in the open European soccer leagues seems effective in ensuring a balanced competition.



#14 Differences in body composition, static balance, field test performance, and academic achievement in 10-12-year-old soccer players

Reference: Front Physiol. 2023 Mar 30;14:1150484. doi: 10.3389/fphys.2023.1150484. eCollection 2023.

Authors: Souhail Hermassi, Lawrence D Hayes, Thomas Bartels, René Schwesig

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Summary: This study aimed to compare 10-12-year-old Qatari male soccer players (n = 45) regarding different dimensions (anthropometric, academic and physical performance). Anthropometric parameters (body mass, fat percentage (%BF), body mass index (BMI)) academic achievement (mathematics and science grade point average [GPA]) and physical performance [Yo-Yo Intermittent Recovery Test (level 1), squat jumps (SJ), counter-movement jumps (CMJ), stork balance test, 10 and 15 m sprint tests, T-half test for change-of-direction (CoD) ability, hand-grip strength, medicine ball throw (MBT)] were measured. Schoolchild soccer players were divided into three groups: 12-year-old players (U12; n = 16), 11-year-old players (U11; n = 14), 10-year-old players (U10; n = 15). Apart from mathematics, Yo-Yo IR1 and 10 m sprint, all performance parameters showed significant age effects. The largest age-related difference was observed for 15 m sprint (p < 0.001). Both adjacent age groups displayed significant differences for 15 sprint (U10 vs. U11: p = 0.015; U11 vs. U12: p = 0.023). Concerning academic performance, a significant age effect was found for science (p < 0.001). There was a main age effect on academic performance difference between U10 and U11 (p = 0.007). Academic parameters did not correlate with any physical performance parameter or anthropometric parameter. The strongest correlations were detected for body height and agility T-half test (r = -0.686) and medicine ball throw (r = 0.637). The biological maturity was strongly correlated with handgrip strength (r = -0.635). Soccer coaches and physical education teachers can use these data as reference values for evaluation of school-aged soccer players, and for ascertaining specific training targets. Obviously, short sprinting ability and aerobic capacity are not functions of age and need a specific training for significant improvements.



#15 Virtual reality as a representative training environment for football referees

Reference: Hum Mov Sci. 2023 Apr 19;89:103091. doi: 10.1016/j.humov.2023.103091. Online ahead of print.

Authors: Tammie van Biemen, Daniel Müller, David L Mann

Summary: Visual experience plays an important role in facilitating referee decision-making. Video training can be used to train these perceptual-cognitive skills in discrete scenarios, for instance in foul situations in football, but is less suitable in other instances such as when seeking to make decisions in open-play scenarios due to a lack of representativeness. Recent technological advances enable the use of virtual reality (VR) to replicate game situations in a controlled and realistic manner. It is however not yet known how representative behaviour in VR would be of behaviour on-field in the natural environment. The aim of the study was therefore to examine the degree to which visual behaviour of football referees in virtual reality would reflect behaviour found when adjudicating matches on-field. Sub-elite football referees completed decision-making tasks in three experimental conditions: on-field (in a real match), in virtual reality and when observing video footage. Across the three environments we compared decision-making performance, visual behaviour (including search rate, fixation duration, and head movements) and the user experience of the referees. Results revealed that behaviour in the VR environment was indistinguishable from that on-field. In contrast, visual-motor behaviour when observing video footage was markedly different to that found on-field (and in VR). The results show that visual-motor behaviour in VR is representative of that found on-field and therefore suggests that VR offers promise as a representative training environment for sports officials to improve on-field performance in the natural environment.



#16 Comparison of the neuromuscular response to three different Turkish, semi-professional football training sessions typically used within the tactical periodization training model

Reference: Sci Rep. 2023 Apr 20;13(1):6467. doi: 10.1038/s41598-023-33630-0.

Authors: Joel M Garrett, Cedric Leduc, Zeki Akyildiz, Daniel J van den Hoek, Filipe Manuel Clemente, Mehmet Yildiz, Hadi Nobari

Summary: This study examined the neuromuscular responses to three typical football (soccer) training sessions and the reliability of peak speed (PS) measured during a submaximal running test (SRT) for identifying neuromuscular fatigue (NMF) status. Jump height (CMJH) and peak velocity (CMJPV) were collected from a CMJ test, while peak speed (PS) was collected during an SRT before and after each training session. Large effect size (ES) decreases were observed in each variable post-training (ES; - 1.42 to - 2.32). Significant differences (> 0.001) were detected between each football session's external load variables. Coefficients of variations were small (< 10%) with moderate (CMJPV; 0.53, PS; 0.44) and strong (CMJH; 0.72) intraclass correlation coefficients between pre-test measures. The demands of each football session aligned with the principles of tactical periodization and were sufficient to produce the fatigue necessary to elicit physiological adaptations. PS was also shown to be a viable measure of monitoring NMF status.



#17 Training Load Quantification in Women's Elite Football: A Season-Long Prospective Cohort Study

Reference: Int J Sports Physiol Perform. 2023 Apr 20;1-12. doi: 10.1123/ijspp.2022-0272. Online ahead of print.

Authors: Ulrik B Karlsson, Markus Vagle, Håvard Wiig, Live S Luteberget

Summary: The aim of this study was to investigate (1) if there are differences in training load and intensity between the different training days within a microcycle and (2) if training load and intensity within the different training days are stable over the course of a season. Data were collected over a full season from a team in the women's premier division in Norway. External load (total distance, high-speed-running distance, sprint distance, and the combined number of accelerations and decelerations [ACCDEC]) was assessed using a 10-Hz GPS system with a built-in accelerometer. Internal load was assessed through session rating of perceived exertion, which was multiplied with session duration (session rating of perceived exertion-load). Training days were classified in relation to their proximity to the upcoming match day (MD): MD - 4, MD - 3, MD - 2, and MD - 1. Contents on these days were standardized according to a weekly periodization model followed by the coaching staff. Differences between training days were analyzed using a linear mixed-effects model. All training days were significantly different from each other across multiple variables. ACCDEC values were highest on MD - 4 (147.5 [13.0] ACCDEC count), and all distance variables were highest on MD - 3. All measures of training load were significantly reduced from MD - 3 to MD - 2 (effect size [ES] = 1.0-4.1) and from MD - 2 to MD - 1 (ES = 1.6-4.3). A significant negative effect across the season was observed for session rating of perceived exertion-load and ACCDEC (ES = 0.8-2.1). These results provide evidence that elite female football teams can be successful in differentiating training load between training days when implementing a weekly periodization approach.






Positional and temporal differences in peak match running demands of elite football

Temporal changes in the total running demands of professional football competition have been well documented, with absolute running demands decreasing in the second half. However, it is unclear whether the peak match running demands demonstrate a similar decline.






Effects of Game Weekly Frequency on Subjective Training Load, Wellness, and Injury Rate in Male Elite Soccer Players

The aim was to compare the effects of playing one or two games per week on subjective perceived exertion (RPE) and (RPE-based) training load, monotony index, sleep, stress, fatigue, and muscle soreness (Hooper index), total mood disturbance, and injury rate in elite soccer players.





Latest research in football - week 12 - 2023

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 Development of a Return to Performance Pathway Involving A Professional Soccer Player Returning From A Multi-Structural Knee Injury: A Case Report

Reference: Int J Sports Phys Ther. 2023 Apr 2;18(2):450-466. doi: 10.26603/001c.73317. eCollection 2023.

Authors: Andrew Mitchell, Ollie Waite, Craig Holding, Matt Greig

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Summary: This case report describes a male professional soccer player returning to match play (English Championship League) following a medial meniscectomy that occurred during the course of rehabilitation after Anterior Cruciate Ligament (ACL) reconstruction. The player underwent a medial meniscectomy eight months into an ACL rehabilitation program and following 10 weeks of rehabilitation successfully returned to competitive first team match play. This report outlines description of the pathology, the rehabilitation progressions, and the sports specific performance requirements of the player as they progressed through the return to performance pathway (RTP). The RTP pathway included nine distinct phases with evidenced based criteria required to exit each phase. The first five phases were indoor as the player progressed from the medial meniscectomy, through the rehabilitation pathways to the "gym exit Phase". The gym exit Phase was assessed with multiple criteria: a) capacity; b) strength; c) isokinetic dynamometry (IKD); d) hop test battery; e) force plate jumps; and f) supine isometric hamstring rate of force (RFD) development qualities to evaluate the players readiness to start sport specific rehabilitation. The last four phases of the RTP pathway are designed to regain the maximal physical capabilities (plyometric and explosive qualities) in the gym and included the retraining of on-field sport specific qualities utilizing the 'control-chaos continuum.' The player successfully returned to team play in the ninth and final phase of the RTP pathway. The purpose of this case report was to outline a RTP for a professional soccer player who successfully restored specific injury criteria (strength, capacity and movement quality), physical capabilities (plyometric and explosive qualities). and on-field sport specific criteria utilizing the 'control-chaos continuum.'



#2 Prevention of sports-related concussion in soccer: a comprehensive review of the literature

Reference: Ann Med Surg (Lond). 2023 Mar 24;85(3):365-373. doi: 10.1097/MS9.0000000000000268. eCollection 2023 Mar.

Authors: Rr Suzy Indharty, Andre M P Siahaan, Rosarina, Martin Susanto, Steven Tandean, Marsal Risfandi

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Summary: Concussion is a common complaint among adult and adolescent athletes around the world and poses a safety risk in competitive, recreational, and noncontact sports. It is estimated that concussions occur at a rate of 0.5 per 1000 playing hours; however, the precision of this estimate is uncertain due to variations in the interpretation and reporting of concussions. Athletes with a history of concussions are more likely to sustain additional concussions, which can result in cognitive decline, depression, and early degenerative change. In order to lessen the likelihood of future difficulties, this study compiles the research on preventing sports-related concussion in soccer and presents a summary of the findings. We performed a literature search on PubMed, EBSCO (Elton B. Stephens Company), DOAJ (Directory of Open Access Journals), and Cochrane for the past 20 years. The search strategy was using Boolean terms based on any of the search terms of sports-related-concussion, soccer, and prevention. The studies were included based on inclusion and exclusion criteria. This research identified three systematic reviews, seven literature reviews, five cross-sectional studies, one randomized controlled trial, three prospective studies, and one retrospective study. As concussion prevention measures in soccer, several strategies can be implemented, including concussion education, rule/regulation changes, proper heading technique, behavioral skills training, vision training to improve sensory and anticipation, the use of supplements to prevent severe concussion and accelerate recovery, as well as prevention in youth sports and head impact detection. Good education, good technique, good training, and a good strengthening program can be implemented to prevent concussions in soccer. To determine the relationship between prevention and concussion, however, additional research is required.



#3 Skinfold thickness variation and associations with cardiorespiratory fitness in male soccer players of different ages

Reference: Eur Rev Med Pharmacol Sci. 2023 Mar;27(6):2200-2209. doi: 10.26355/eurrev_202303_31753.

Authors: P T Nikolaidis, K Weiss, B Knechtle

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Summary: The aim of the present study was to examine skinfold thickness (SKF) distribution in youth and adult male soccer players regarding cardiorespiratory fitness (CRF) and the role of age. Participants were youth [n=83, age 16.2 (1.0) years, mean (standard deviation)] and adult male soccer players [n=121, 23.2 (4.3) years], who were tested for SKF on 10 anatomical sites and Conconi test was used to assess velocity at maximal oxygen uptake (vVO2max). A between-within-subjects analysis of variance revealed a small interaction between the anatomical site and age group on SKF (p=0.006, η2=0.022), where adolescents had larger cheek (+0.7 mm; p=0.022; 95% confidence intervals - CI - 0.1, 1.3), triceps (+0.9 mm; p=0.017; 95% CI 0.2, 1.6) and calf (+0.9 mm; p=0.014; 95% CI 0.2, 1.5) SKF, while adults had larger chin (+0.5 mm; p=0.007; 95% CI 0.1, 0.8) SKF, and no difference was observed for the rest of the anatomical sites. No difference between adolescent and adult age groups was observed in average SKF (SKFavg) [9.0 (2.7) vs. 9.1 (2.5) mm; difference -0.1 mm; 95% CI, -0.8, 0.6; p=0.738]. Compared to adults, adolescents had a lower SKF coefficient of variation (SKFcv) [0.34 (0.10) vs. 0.37 (0.09); difference-0.03; 95% CI, -0.06, -0.01; p=0.020] and subscapular-to-triceps ration (STR) [1.08 (0.28) vs. 1.29 (0.37); difference-0.21; 95% CI, -0.31, -0.12; p<0.001]. The largest Pearson moment correlation coefficient between vVO2max and SKF was shown in the subscapular (r=-0.411; 95% CI, -0.537, -0.284; p<0.001) and the smallest in the patellar anatomical site (r=-0.221; 95% CI, -0.356, -0.085; p=0.002). In addition, vVO2max correlated moderately with SKFavg (r=-0.390; 95% CI, -0.517, -0.262; p<0.001) and SKFcv (r=-0.334; 95% CI, -0.464, -0.203; p<0.001). In summary, CRF was related to the thickness of specific SKF and the magnitude of thickness variation by the anatomical site (i.e., the smaller the variation, the better the CRF). Considering the relevance of specific SKF for CRF, their further use would be recommended for monitoring physical fitness in soccer players.



#4 Effects of a Short-Term Detraining Period on the Strength Deficit and Functional Performance of Highly Trained Soccer Players

Reference: J Strength Cond Res. 2023 Apr 3. doi: 10.1519/JSC.0000000000004496. Online ahead of print.

Authors: Irineu Loturco, Rafael Grazioli, Filipe Veeck, Fabio Y Nakamura, Martinho Inácio, Pedro Schons, Artur Preissler, Ronei S Pinto, Lucas A Pereira, Michael R McGuigan, Eduardo L Cadore

Summary: The aim of this study was to examine the effects of a 4-week detraining period on the neuromuscular performance of highly trained soccer players. Pre and post detraining, 18 adult soccer players (age: 27 ± 4.9 years; height: 180.2 ± 7.1 cm; body mass [BM]: 78.9 ± 7.6 kg) performed vertical jumps, 20-m linear sprints, curve sprint and change of direction speed tests, and a progressive loading test in the half-squat exercise with loads corresponding to 50, 100, and 150% of the players' BM to assess the peak-force (PF), mean power (MP), and strength-deficit (SDef). Pre and post differences in the variables of interest were analyzed using paired t-tests and effect sizes (ES). No significant changes were detected for vertical jumping height and sprint times. Higher PF at 50 and 100% BM and lower SDef were shown when comparing pre- and postassessments (ES = 0.66, 0.68, 0.55; p = 0.018, 0.016, and 0.046, respectively). The MP at 50 and 100% BM increased significantly after the detraining phase (ES = 0.56, 0.82; p = 0.049 and 0.007, respectively). The results indicate that these athletes were able to maintain and achieve satisfactory levels of performance after a short period of training cessation. Interestingly, some strength- and power-derived parameters improved significantly after short-term detraining, which may have important implications for training programs aimed at maximizing speed and power performance. It is recommended that coaches test their players not only at the beginning but also at the end of the season, to better evaluate variations in performance and thus create more efficient and tailored training strategies.



#5 Effects of FIFA 11 + warm-up program on kinematics and proprioception in adolescent soccer players: a parallelgroup randomized control trial

Reference: Sci Rep. 2023 Apr 4;13(1):5527. doi: 10.1038/s41598-023-32774-3.

Authors: Mohammadreza Seyedi, Mostafa Zarei, Abdolhamid Daneshjoo, Reza Rajabi, Elham Shirzad, Esmaeil Mozafaripour, Shadan Mohammadpour

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Summary: This study aimed to compare the effects of 8 weeks 11 + warm-up injury prevention program on kinematics and proprioception in adolescent male and female soccer players. Forty adolescent soccer players (20 males, 20 females) aged between 14-16 years old were randomly assigned into four groups. The experimental group performed the 11 + program for 8 weeks and the control group did their warm-up program. The kinematic variable in a cutting maneuver was measured using VICON motion analysis and ankle and knees' proprioception by joint position sense (JPS) was measured using a digital inclinometer. For kinematic variables only significant differences in knee valgus among females 11 + compared with female and male control groups were found (P < 0.05). Moreover, there were significant improvements in joint position sense variables in 11 + groups compared to control groups (P < 0.05). In conclusion, the 11 + program was proven to be a useful warm-up protocol in improving knee valgus and JPS among female and male adolescent soccer players. We suggest adding more training elements to the 11 + program that aimed to enhance the proper alignment of lower extremities which may consequently improve joint kinematics.



#6 Effect of interval and continuous small-sided games training on the bio-motor abilities of young soccer players: a comparative study

Reference: BMC Sports Sci Med Rehabil. 2023 Apr 4;15(1):51. doi: 10.1186/s13102-023-00664-w.

Authors: Farhad Daryanoosh, Hossein Alishavandi, Javad Nemati, Aref Basereh, Alireza Jowhari, Enayatollah Asad-Manesh, Rafael Oliveira, João Paulo Brito, Pablo Prieto-González, Tomás García-Calvo, Kayvan Khoramipour, Hadi Nobari

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Summary: The present study compared the effects of two different small-sided game (SSG) training methods, interval (ISSG) and continuous (CSSG) on the bio-motor abilities of young soccer players. Sixteen young soccer players (age: 19.5 ± 0.5 years; height: 177 ± 4.72 cm) were ranked based on the result of a running-based anaerobic sprint test (RAST) and randomly divided into two groups: CSSG (n = 8) and ISSG (n = 8). The training protocols were performed for eight weeks, three sessions per week. Participants were assessed twice (pre- and post-intervention) to estimate their anaerobic capacity with the RAST, aerobic capacity with Yo-Yo intermittent recovery test, body fat percentage with a bioimpedance analysis, speed with a 30-meter run test, and agility with the Illinois agility test. During the training session, the rating of the perceived exertion (RPE) and heart rate (mean and maximum) were recorded to assess the training load. In general, aerobic and anaerobic capacities improved after ISSG (p < 0.05, for all). The between-group analysis with repeated measures ANOVA revealed higher values for ISSG than CSSG groups post-intervention in anaerobic power (p = 0.042, ηp2 = 0.264). In addition, the independent t-test results indicated that ISSG presented lower values of mean heart rate (p = 0.023, effect size [ES] = 0.85) and RPE (p < 0.05, ES = 0.88) than CSSG. Moreover, higher values for maximum heart rate were revealed for ISSG than for the CSSG group (p = 0.004, ES = 0.85). In conclusion, the findings of this study suggests that ISSG can lead to better improvements in anaerobic power and aerobic capacity than CSSG. Additionally, the ISSG led to a lower mean heart rate and RPE than the CSSG. Therefore, coaches and trainers may want to consider incorporating ISSG into their training programs for young soccer players to enhance their bio-motor abilities.



#7 Ecological and Specific Evidence-Based Safe Return To Play After Anterior Cruciate Ligament Reconstruction In Soccer Players: A New International Paradigm

Reference: Int J Sports Phys Ther. 2023 Apr 2;18(2):526-540. doi: 10.26603/001c.73031. eCollection 2023.

Authors: Florian Forelli, Nicolas Le Coroller, Maxime Gaspar, Geoffrey Memain, Georgios Kakavas, Nicholas Miraglia, Patrice Marine, Pascal Maille, Timothy E Hewett, Alexandre Jm Rambaud

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Summary: Existing return to play (RTP) assessments have not demonstrated the ability to decrease risk of subsequent anterior cruciate ligament (ACL) injury after reconstruction (ACLR). RTP criteria are standardized and do not simulate the physical and cognitive activity required by the practice of sport. Most RTP criteria do not include an ecological approach. There are scientific algorithms as the "5 factor maximum model" that can identify risk profiles and help reduce the risk of a second anterior cruciate ligament injury. Nevertheless, these algorithms remain too standardized and do not include the situations experienced in games by soccer players. This is why it is important to integrate ecological situations specific to the environment of soccer players in order to evaluate players under conditions closest to their sporting activity, especially with high cognitive load. One should identify high risk players under two conditions: Clinical analyses commonly include assessments such as isokinetic testing, functional tests (hop tests, vertical force-velocity, profile), running, clinical assessments (range of motion and graft laxity), proprioception and balance (Star Excursion Balance Test modified, Y-Balance, stabilometry) and psychological parameters (kinesophobia, quality of life and fear of re-injury). Field testing usually includes game simulation, evaluation under dual-task conditions, fatigue and workload analysis, deceleration, timed-agility-test and horizontal force-velocity profiles. Although it seems important to evaluate strength, psychological variables and aerobic and anaerobic capacities, evaluation of neuromotor control in standard and ecological situations may be helpful for reducing the risk of injury after ACLR. This proposal for RTP testing after ACLR is supported by the scientific literature and attempts to approximate the physical and cognitive loads during a soccer match. Future scientific investigation will be required to demonstrate the validity of this approach.



#8 Expected goals in football: Improving model performance and demonstrating value

Reference: PLoS One. 2023 Apr 5;18(4):e0282295. doi: 10.1371/journal.pone.0282295. eCollection 2023.

Authors: James Mead, Anthony O'Hare, Paul McMenemy

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Summary: Recently, football has seen the creation of various novel, ubiquitous metrics used throughout clubs' analytics departments. These can influence many of their day-to-day operations ranging from financial decisions on player transfers, to evaluation of team performance. At the forefront of this scientific movement is the metric expected goals, a measure which allows analysts to quantify how likely a given shot is to result in a goal however, xG models have not until this point considered using important features, e.g., player/team ability and psychological effects, and is not widely trusted by everyone in the wider football community. This study aims to solve both these issues through the implementation of machine learning techniques by, modelling expected goals values using previously untested features and comparing the predictive ability of traditional statistics against this newly developed metric. Error values from the expected goals models built in this work were shown to be competitive with optimal values from other papers, and some of the features added in this study were revealed to have a significant impact on expected goals model outputs. Secondly, not only was expected goals found to be a superior predictor of a football team's future success when compared to traditional statistics, but also our results outperformed those collected from an industry leader in the same area.



#9 Effects of walking football on adherence, safety, quality of life and physical fitness in patients with prostate cancer: Findings from the PROSTATA_MOVE randomized controlled trial

Reference: Front Oncol. 2023 Mar 21;13:1129028. doi: 10.3389/fonc.2023.1129028. eCollection 2023.

Authors: Andreia Capela, Pedro Antunes, César André Coelho, Catarina Laranjeiro Garcia, Sandra Custódio, Rui Amorim, Telma Costa, Eduardo Vilela, Madalena Teixeira, Anabela Amarelo, Joana Silva, Ana Joaquim, Sofia Viamonte, João Brito, Alberto J Alves

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Summary: The aim was to analyze the feasibility and impact of a walking football (WF) program on quality of life (QoL), cardiorespiratory fitness (CRF), muscle strength, and balance program in men with prostate cancer under androgen deprivation therapy (ADT). Fifty patients with prostate cancer (stages IIb-IVb) under ADT were randomized to a 16-week WF program plus usual care (n=25) or usual care control group (n=25). The WF program consisted of three 90-minute sessions per week. Recruitment, withdrawal, adherence, enjoyment rate, and safety of the intervention were recorded throughout the study. Cardiorespiratory fitness was assessed before and after the interventions, while handgrip strength, lower limb muscle strength, static balance, and QoL were assessed before, during (week 8), and after (week 16) the interventions. Adverse events during sessions were also recorded. The WF group showed high levels of adherence (81.6 ± 15.9%) and enjoyment rate (4.5 ± 0.5 out of 5 points). In the intention-to-treat analysis, the WF group showed an improvement in chair sit-to-stand (p=0.035) compared to the control group. Within-group comparisons showed that handgrip strength in the dominant upper limb (p=0.024), maximal isometric muscle strength in the non-dominant lower limb (p=0.006), and balance in the dominant limb (p=0.009) improved over time in the WF group but not in the usual care group. The results obtained from the per-protocol analysis indicate that CRF improved significantly in the WF group as compared to the control group (p=0.035). Within-group analysis revealed that CRF (p=0.036), muscle strength in dominant (p=0.006) and non-dominant (p=0.001) lower limbs, and balance in the non-dominant lower limb (p=0.023) improved after 16 weeks of WF, but not in the control group. One major traumatic injury (muscle tear) was reported with a complete recovery before the end of the intervention. This study suggests that WF is feasible, safe, and enjoyable in patients with prostate cancer under hormonal therapy. Furthermore, patients who adhere to the WF program can expect cardiorespiratory fitness, muscle strength, and balance improvements.



#10 Are Football Players More Prone to Muscle Injury after COVID-19 Infection? The "Italian Injury Study" during the Serie a Championship

Reference: Int J Environ Res Public Health. 2023 Mar 15;20(6):5182. doi: 10.3390/ijerph20065182.

Authors: Alessandro Corsini, Andrea Bisciotti, Raffaele Canonico, Andrea Causarano, Riccardo Del Vescovo, Pierluigi Gatto, Paolo Gola, Massimo Iera, Stefano Mazzoni, Paolo Minafra, Gianni Nanni, Giulio Pasta, Ivo Pulcini, Stefano Salvatori, Marco Scorcu, Luca Stefanini, Fabio Tenore, Stefano Palermi, Maurizio Casasco, Stefano Calza

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Summary: Football was the first sport to resume competitions after the coronavirus disease 2019 (COVID-19) lockdown and promptly the hypothesis was raised of a potential relationship between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and musculoskeletal injuries in athletes. This study aimed to confirm the association between SARS-CoV-2 infection and muscle strain injury in a large population of elite football players and to investigate if the COVID-19 severity level could affect the risk of injury. A retrospective cohort study involving 15 Italian professional male football teams was performed during the Italian Serie A 2020-2021 season. Injuries and SARS-CoV-2 positivity data were collected by team doctors through an online database. Of the 433 included players, we observed 173 SARS-CoV-2 infections and 332 indirect muscle strains. COVID-19 episodes mostly belonged to severity level I and II. The injury risk significantly increased after a COVID-19 event, by 36% (HR = 1.36, CI95% 1.05; 1.77, p-value = 0.02). The injury burden demonstrated an 86% increase (ratio = 1.86, CI95% 1.21; 2.86, p-value = 0.005) in the COVID-19 severity level II/III versus players without a previous SARS-CoV-2 infection, while level I (asymptomatic) patients showed a similar average burden (ratio = 0.92, CI95% 0.54; 1.58, p-value = 0.77). A significantly higher proportion of muscle-tendon junction injuries (40.6% vs. 27.1%, difference = 13.5%, CI95% 0.002%; 26.9%, p-value = 0.047) was found when comparing level II/III versus Non-COVID-19. This study confirms the correlation between SARS-CoV-2 infection and indirect muscle injuries and highlights how the severity of the infection would represent an additional risk factor.



#11 Association between ACTN3 R577x and the physical performance of Chinese 13 to 15-year-old elite and sub-elite football players at different positions

Reference: Front Genet. 2023 Mar 10;14:1038075. doi: 10.3389/fgene.2023.1038075. eCollection 2023.

Authors: Shidong Yang, Wentao Lin, Mengmeng Jia, Haichun Chen

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Summary: The purpose of this study was to investigate the prevalence of ACTN3 polymorphisms in Chinese elite and sub-elite football players aged 13-15 years at different positions. Specifically we explored whether ACTN3 genotypes were linked with athletic performance of elite and sub-elite players at different positions. The RR genotype frequency of elite defenders (p = 0.018) and midfielders (p = 0.008) was significantly higher than that of sub-elite XX genotype in elite players. Furthermore, the R allele frequency of elite defenders (p = 0.003) and midfielders (p = 0.008) was significantly higher than that of sub-elite players. In all subjects, RR players performed faster and exhibited more explosive power than RX or XX players. RR, RX and XX elite players' 20 m/30 m sprint, 5 × 25-m repeated sprint ability (5 × 25 m RSA), and standing long jump were stronger than sub-elite players, but there was no significant different in aerobic endurance between elite and sub-elite players at different positions. In conclusion, there were significant differences in ACTN3 genotypes and alleles between elite and sub-elite players at different positions, and the RR genotype was significantly associated with power-related athletic performance in Chinese youth football players.



#12 "We're All the Same and We Love Football." Experiences of Players and Facilitators Regarding a Collaborative, Inclusive Football Program Between Academy and Special Olympics Footballers

Reference: Adapt Phys Activ Q. 2023 Mar 25;1-20. doi: 10.1123/apaq.2022-0139. Online ahead of print.

Authors: Melissa A Fothergill, Danna Baik, Hannah M Slater, Pamela L Graham

Summary: This study provides insight into an inclusive program between Special Olympics (SO) and academy football (soccer) players in the United Kingdom from the perspectives of players and facilitators. Qualitative focus groups were conducted across 30 participants (six facilitators, 14 Premier League academy players, and 10 SO players). Focus groups compared stakeholders' experiences of participating in a season-long inclusive football program. Three overarching higher order themes were generated, which highlighted positive outcomes from taking part. SO players provided endorsement for developing friendships and improving football skills, whereas academy players cited the positive impact that SO players had on their mood and motivation. Facilitators reflected on positive player outcomes and subsequent accomplishments. Overall, the findings indicated that this shared experience had psychosocial and football-specific benefits for everyone who participated. Facilitators indicated that these benefits could transition into everyday life but noted that there needs to be further considerations for future programs.



#13 Comparison of echocardiographic parameters of amputee football players with active football players and sedentary individuals

Reference: BMC Sports Sci Med Rehabil. 2023 Mar 24;15(1):41. doi: 10.1186/s13102-023-00651-1.

Authors: Ahmet Kurtoğlu, Ertuğrul Kurtoğlu, Nurettin Konar, Bekir Çar, Özgür Eken, Pablo Prieto-González, Hadi Nobari

Summary: The purpose of this study is to compare the echocardiographic (ECHO) parameters of amputee football players (AF) with those of athletes without a disability (football players) (FP), and sedentary individuals (SI). A total of 37 male participants (nAF = 12, nFP = 12, nSI = 13) were included in the study. All participants underwent a transthoracic echocardiographic examination. Aortic diameter in systole (ADs), aortic diameter in diastole (ADd), isovolumic contraction time (IVCT), isovolumic relaxation time (IVRT), left ventricular ejection fraction (LVEF), early (E) and late (A) wave velocities, myocardial systolic (S), early diastolic (E'), and late diastolic (A') myocardial rates, interventricular septal thickness (IVS), left ventricular end-diastolic diameter (LVDd) and left ventricular end-systole diameter (LVDs), left ventricular posterior wall thickness (LVPWd), left atrial diameter (LAD), and ascending aortic diameter (AAD) were measured. LVDd, E' were lower in AF than in FP. In contrast, LVDs, LVPWd, and A wave were higher in AF than in FP. When AF and SI groups were compared, ADs, LVPWd, A wave, IVRT, and S wave were higher in AF than in SI. ANOVA test showed a statistically significant difference between groups in LVPWd, A-wave, and E' wave. TTE data indicate that some parameters in AF differ from those observed in healthy individuals. The smaller LVEED diameter and higher PWT were found in AF. Although within normal limits, some ECHO parameters in the AF group differed from those without disability. Future studies should further investigate these differences using different and detailed measurement methods.



#14 Dictating play to the left wing: Does soccer make you more Democratic?

Reference: Front Sports Act Living. 2023 Mar 23;5:1004695. doi: 10.3389/fspor.2023.1004695. eCollection 2023.

Authors: Johan M Rewilak

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Summary: There is a correlation between soccer's popularity and states that traditionally vote Democrat in US elections. This has led to claims that where democrats lead, soccer follows. Yet, this relationship may not be entirely stable, as soccer may stimulate the Democratic party vote through its multicultural elements. Using the 1994 World Cup as a plausibly exogenous shock that positioned US soccer, we investigate whether US states that hosted the tournament increased their Democratic vote in future Presidential elections. A two-way fixed-effects estimator and a dynamic difference-in-difference estimator shows that if a US state was a 1994 World Cup host, it increased its Democratic vote share. However, when examining Major League Soccer franchises, this relationship breaks down but recovers when investigating the women's World Cup in 1999 and 2003. As the swing states of Florida and Georgia are hosting 2026 World Cup matches, the findings may hold key insights for the 2028 Presidential election.



#14 Soccer Players' Sleep Quality and Training Load Were Affected by the COVID-19 Lockdown: An International Survey

Reference: Int J Sports Physiol Perform. 2023 Apr 8;1-11. doi: 10.1123/ijspp.2022-0187. Online ahead of print.

Authors: Mohamed Romdhani, Jad Adrian Washif, Lee Taylor, Karim Chamari

Summary: The effect of the 2020 COVID-19 lockdown on athlete sleep and training behavior is documented, albeit without a worldwide soccer-specific focus. Soccer (football) players (N = 1639; 30 countries; age 22.5 [5.7] y; 81% ≤25 y; 56% male; 30% elite; 66% Muslim) answered a retrospective, cross-sectional questionnaire related to their behavioral habits before and during COVID-19 lockdown (survey period July to September 2020), including (1) Pittsburgh Sleep Quality Index PSQI, (2) Insomnia Severity Index (ISI), (3) bespoke questions about training behaviors, and (4) Muslim player focused sleep and training behavior questions. During lockdown (compared to prelockdown), PSQI (P < .001; moderate effect size [ES]) and ISI (P < .001; moderate ES) scores were higher in the overall sample and in elite versus nonelite (PSQI: P < .05; small ES and ISI: P < .001; small ES), >25 years versus ≤25 years (PSQI: P < .01; small ES and ISI: P < .001; moderate ES), females versus males (PSQI: P < .001; small ES), <1 month versus >1 month lockdown (PSQI: P < .05; small ES and ISI: P < .05; small ES), and players maintaining versus reducing training intensity (PSQI: P < .001; moderate ES and ISI: P < .001; small ES). Muslim players (41%) reported unfavorable sleep and/or training behaviors during Ramadan in lockdown compared to lockdown outside of Ramadan. Specific subgroups appear more vulnerable to lockdown effects, with training-intensity maintenance moderating negative effects relative to sleep. Policy and support (respectful of subgroup nuances) during lockdown-like challenges that facilitate training (including intensity) appear prudent, given their favorable relationship with sleep, mental health, and physical health, in the present data and elsewhere.



#15 Effects of Ramadan fasting on the diurnal variations of physical and cognitive performances at rest and after exercise in professional football players

References: Front Psychol. 2023 Mar 28;14:1148845. doi: 10.3389/fpsyg.2023.1148845. eCollection 2023.

Authors: Syrine Khemila, Mohamed Romdhani, Mohamed Amine Farjallah, Rihab Abid, Emna Bentouati, Mohamed Abdelkader Souissi, Salma Abedelmalek, Sergio Garbarino, Nizar Souissi

Summary: Ramadan fasting (RF) is characterized by daily abstinence from food and fluid intake from dawn to sunset. The understanding of the Ramadan effects on the diurnal variations of athletic and cognitive performance is crucial for practitioners, coach and researchers to prepare sport events and optimize performance. The aim of the present study was to reveal the effects of RF on the diurnal variation of physical and cognitive performances at rest and after exercise. In a randomized order, 11 male football players (age: 19.27 ± 0.9; height: 1.79 ± 0.04 cm; body mass: 70.49 ± 3.97 kg; BMI: 21.81 ± 1.59 kg/m2) completed a 30-s Wingate test [i.e., mean (MP) and peak powers (PP)] at 07:00, 17:00, and 21:00 h on five occasions: 1 week before Ramadan (BR); the second (R2); the third (R3); the fourth (R4) week of Ramadan; and 2 weeks after Ramadan (AR), with an in-between recovery period of ≥72 h. Simple (SRT) and choice (CRT) reaction times, mental rotation test (MRT) and selective attention (SA) test were measured before and after Wingate test. Rating of perceived exertion (RPE), body composition, dietary intake, profile of mood states (POMS) and Pittsburgh Sleep Quality Index (PSQI) were assessed over the five periods. Compared to BR, RF decreased MP at 17:00 h (p < 0.05, d = 1.18; p < 0.001, d = 2.21, respectively) and PP at 17:00 h (p < 0.05, d = 1.14; p < 0.001, d = 1.77, respectively) and 21:00 h (p < 0.01, d = 1.30; p < 0.001, d = 2.05, respectively) at R3 and R4. SRT (p < 0.001,d = 1.15; d = 1.32, respectively), number of correct answers (MRTE; p < 0.05, d = 1.27; d = 1.38, respectively) and SA (p < 0.01, d = 1.32; d = 1.64, respectively) increased during R2 and R3 in the evening before exercise compared to BR. Short term maximal exercise enhanced SRT (p < 0.01, d = 1.15; p < 0.001, d = 1.35, respectively), MRTE (p < 0.001, d = 2.01; d = 2.75 respectively) and SA (p < 0.05, d = 0.68; d = 1.18, respectively) during R2 and R3 in the evening. In comparison to BR, sleep latency and sleep duration increased during R3 (p < 0.001, d = 1.29; d = 1.74, respectively) and R4 (p < 0.001, d = 1.78; d = 2.19, respectively) and sleep quality increased in R2, R3 and R4 (p < 0.01, d = 1.60; p < 0.001, d = 1.93; d = 2.03, respectively). During RF, anaerobic and cognitive performances were unaffected in the morning but were impaired in the afternoon and evening. Short-term maximal exercise mitigates the negative effects of fasting on cognitive performance. Maximal exercise could thus partially counteract the effect of fasting on cognitive function.



#16 Osteomyelitis of the Pubis Treated by Masquelet Technique in a Football Player: A Case Report

Reference: J Orthop Case Rep. 2022 Dec;12(12):39-42. doi: 10.13107/jocr.2022.v12.i12.3456.

Authors: Hitomi Kitamura, Tomoaki Fukui, Keisuke Oe, Takehiko Matsushita, Ryosuke Kuroda, Takahiro Niikura

Summary: Osteomyelitis pubis is a rare disease that presents with fever, pubic or hip pain, pain during hip movement, and claudication to avoid pain. It most frequently affects young athletes involved in sports that require twisting and cutting, but its exact cause is unknown and no definite treatment has been established. We report a case of pubic osteomyelitis in a young football player who was treated using the Masquelet technique and antibiotics with a good clinical course. A 22-year-old male football player in a national-level university club team visited a nearby clinic complaining of high fever and mild pain in his bilateral hip joints. As a result of examination, we diagnosed osteomyelitis pubis and reconstructed the pubic symphysis by the Masquelet technique. In this case, the joint-like structure of the pubic symphysis was successfully reconstructed, and the patient was able to continue playing the sport. Three years and 3 months after surgery, he had no limitation of bilateral hip joint range of motion and did not display any symptoms while playing football. Masquelet technique could be a novel surgical method for managing osteomyelitis pubis, even in athletes.



#16 A framework of interpretable match results prediction in football with FIFA ratings and team formation

Reference: PLoS One. 2023 Apr 13;18(4):e0284318. doi: 10.1371/journal.pone.0284318. eCollection 2023.

Authors: Calvin C K Yeung, Rory Bunker, Keisuke Fujii

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Summary: While forecasting football match results has long been a popular topic, a practical model for football participants, such as coaches and players, has not been considered in great detail. In this study, we propose a generalized and interpretable machine learning model framework that only requires coaches' decisions and player quality features for forecasting. By further allowing the model to embed historical match statistics, features that consist of significant information, during the training process the model was practical and achieved both high performance and interpretability. Using five years of data (over 1,700 matches) from the English Premier League, our results show that our model was able to achieve high performance with an F1-score of 0.47, compared to the baseline betting odds prediction, which had an F1-score of 0.39. Moreover, our framework allows football teams to adapt for tactical decision-making, strength and weakness identification, formation and player selection, and transfer target validation. The framework in this study would have proven the feasibility of building a practical match result forecast framework and may serve to inspire future studies.



#17 Suggested improvements to the 11+ as identified by coaches, players, strength and conditioning staff and medical staff in New Zealand Football

Reference: BMJ Open Sport Exerc Med. 2023 Apr 4;9(2):e001463. doi: 10.1136/bmjsem-2022-001463. eCollection 2023.

Authors: Colleen Winstanley, Duncan Reid, Mark L Fulcher

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Summary: The aim of this study was to investigate the experience with the 11+, attitudes towards injury prevention, and potential improvements to the 11+ and the delivery of injury prevention strategies within football. A qualitative study design was used to investigate the views of four stakeholder groups (players, coaches, strength and conditioning staff and clinicians). Twenty-two adults participated (nine women; median age 35.5 years). Participants were purposively recruited and were based in New Zealand. They represented various levels of football, including different genders, ages and levels of play. Focus group interviews were conducted, which were recorded, transcribed and subject to thematic analysis. Four key themes were identified: understanding of the 11+ injury prevention warm-up, content of an ideal injury prevention programme, structure of the programme and education, adherence and dissemination. The study found that while participants appeared to have good awareness of the existing 11+ programme and an interest in injury prevention, adherence and enthusiasm towards the programme was limited. Participants highlighted a number of elements that may help shape the development of a new injury prevention strategy, including a desire to retain many of the elements of the 11+ and to have a proven programme. Participants wanted greater variety, more football-specific elements and to implement a new strategy throughout a session, rather than being seen as a stand-alone warm-up. Whether the intervention should also include strength-based exercises, or whether this should be promoted outside of a football training session, was less certain.



#18 "I hardly have a problem […] I have my period quite rarely too": Female football players' and their coaches' perceptions of barriers to communication on menstrual cycle

Reference: Front Sports Act Living. 2023 Mar 23;5:1127207. doi: 10.3389/fspor.2023.1127207. eCollection 2023.

Authors: Max Bergström, Malene Rosvold, Stig Arve Sæther

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Summary: Symptoms related to the menstrual cycle (MC) affect the performance level and health of female athletes in various ways. Previous research has reported MC symptoms such as pain, mood disturbance, reduced coordination and competition distraction as well as diminished performance levels and an increased injury risk among female elite athletes. Despite this, the coach-athlete communication related to the female hormonal cycle is limited. The aim of the present study was to explore the perceptions of MC communication in a group of junior elite football players and their male coaches in a case study of one youth football team in a specific club in Norway. The study used a qualitative approach with semi-structured interviews. In total, 8 female junior elite players (aged 16-20) from a Norwegian football team and 2 of their male coaches participated in the study. The data analysis revealed two main communication barriers: 1. interpersonal barriers (e.g., false assumptions about the coach/athletes and social discomfort) and 2. knowledge barriers (e.g., unaware/perceptions of insufficient knowledge levels). As the players seemed to be unaware of their insufficient MC knowledge (e.g., failed to see a connection between the MC and their health and performance level), the coaches perceived their knowledge as insufficient and coped mainly by outsourcing MC communication to female staff and apps. Hence, the MC communication was hindered by both the athletes and the coaches (e.g., mutual avoidance). In line with previous research, this study supports that there is a need for developing effective strategies to overcome the interpersonal barriers and knowledge gaps.



#19 The Importance of Crowd Support and Team Quality to Home Advantage in Brazilian Soccer League First Division

Reference: Percept Mot Skills. 2023 Apr 10;315125231169876. doi: 10.1177/00315125231169876.

Authors: Rodolfo A Dellagrana, Renan F H Nunes, Rodrigo L P Silva

Summary: Our aims in the present study were to analyze home advantage (HA) and number of goals scored in consideration of the presence or absence of crowd support and the influence of team quality during the last 11 seasons of the Brazilian Soccer League first division. We analyzed data from 4162 matches played in the Brazilian Soccer League in seasons 2012-2022 (3563 matches with an audience and 599 matches without an audience). We calculated HA by comparing the number of points won at home as a percentage of the total number of points gained, and we also recorded the number of goals scored by home and away teams. For analyses, we divided the teams based on home and away matches, with and without crowds, and we classified teams into three ability groups, based on the points scoring percentage of the team at the end of the season. There was a HA in all seasons analyzed (i.e., home teams won more than 50% of the total points won at home); but in matches in empty stadiums, the HA was reduced significantly, compared to matches with crowd support (66.6% with crowd vs. 57.2% without crowd, p < 0.05). The number of goals in all seasons was higher for home teams than for away teams; however, away teams scored more goals in empty stadiums than in stadiums with crowd support (p < 0.05). The HA was greater in matches with crowd support than in matches without crowd support (p < 0.01), independent of the team's ability level; but, top teams scored more goals than weaker teams (p < 0.01). In conclusion, in the Brazilian Soccer League, the HA and number of goals scored were affected by the presence or absent of an audience in the stadiums. While top teams scored more goals than weaker teams, the HA was lower without than with crowds, independent of team quality.



#20 Preparatory knee flexion movement facilitates faster sideways jumping execution in male collegiate soccer goalkeepers

Reference: Sports Biomech. 2023 Apr 10;1-15. doi: 10.1080/14763141.2023.2197876. Online ahead of print.

Authors: Masahiro Fujimoto, Masaomi Sato, Akinori Nagano, Mark W Rogers, Tadao Isaka

Summary: Preparatory lower-limb loading conditions may affect the jump-to-reach performance of soccer goalkeepers. This study investigated the effect of pre-jump lower-limb loading/unloading during bilateral knee flexion-extension movements on sideways jump-to-reach performance in 18 male collegiate soccer goalkeepers. Participants performed the two-choice (high and low targets) reaction-time single-leg jump-to-reach task under two conditions: without preparatory movements (no-prep) and with continuous alternating knee extension and flexion movements (prep). The 'go' cue was provided with different preparatory loading conditions during the pre-jump knee extension and flexion phases. Performance was assessed using three-dimensional kinematic data and ground reaction forces. A significant main effect of the preparatory condition was observed for the jump take-off time. Pairwise comparisons revealed that the jump take-off time was 3.4-4.4% faster when initiated during the knee flexion phase than the no-prep condition and the extension phase (p ≤ .028). Increasing lower-limb loading and downward body movement with knee flexion appeared to facilitate effective loading to take-off to reach the high target and faster downward-directed take-off to reach the low target, respectively. Pre-jump knee flexion movement could be utilised by soccer goalkeepers to facilitate faster take-off to maximise their chances of saving shots within the reach of single-leg side-jumping.







Effects of match contextual factors on internal and external load in elite Brazilian professional soccer players through the season

This study aimed to investigate the effects of contextual match factors (quality of opposition, match outcome, change of head coach or playing style) on internal and external load in elite Brazilian professional soccer players, considering the total and effective playing time.





Workloads of Different Soccer-Specific Drills in Professional Players

The objective of the present study was to assess the workload of soccer-specific drills in professional players over a two-season period in an established context.





The top 20 assistmen worldwide

With the quarterfinals of the UEFA Champions League in full throttle I thought it would be interesting to shine some light on individual players and their role of their team scoring goals.

Below are different graphs of individual players identifying the top 20 assistmen world wide.


The first one and its ranking is based on a) number of assists b) by weighting the number of assists with the sporting coefficient of the matches played deriving from domestic league matches between 01/03/2022 and 01/03/2023. 


Starting with the assists including the coefficient, Kevin De Bruyne comes out on top ahead of Ousmane Dembélé and Lionel Messi. From a club perspective there is only PSG and Tottenham Hotspur displaying two players in the top 20.



Looking purely at the number of assists in the date frame (01/03/2022 and 01/03/2023) of domestic league matches, there are more players from outside the big 5 on display. Dušan Tadić (AFC Ajax), Ahmed Sayed ‘Zizo’ (Zamalek SC) and Emil Hansson (Heracles) are making the top three with each player having 19 assists. 



Last but not least, here are the top twenty players world wide aged 23 or younger with regards to their assists.


Tresor from KRC Genk sits at the top followed by Filipe From Celtic FC, with 19 and 15 assists respectively. Number three is Rodriguez from New York City (14 assists) and Gakpo number 5 (13 assists) as the first player from a Big5 league.






Workloads of Different Soccer-Specific Drills in Professional Players

The objective of the present study was to assess the workload of soccer-specific drills in professional players over a two-season period in an established context.





How do soccer players sprint from a tactical context? Observations of an English Premier League soccer team

The aim of this study was to quantify and tactically contextualise (i.e., phase of play and tactical outcome [TO]) sprints (≥7.0 m/s) of an English Premier League (EPL) soccer team during match-play.






Latest research in football - week 11 - 2023

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 are hamstring strain injuries managed in elite men's football clubs? A survey with 62 Brazilian physical therapists

Reference: Phys Ther Sport. 2023 Mar 4;61:73-81. doi: 10.1016/j.ptsp.2023.03.001. Online ahead of print.

Authors: Henrique Gonçalves Valente, Rodrigo Ribeiro de Oliveira, Bruno Manfredini Baroni

Summary: The aim was to describe perceptions and practices of physical therapists from elite men's football clubs on the management of athletes with hamstring strain injury (HSI). Physical therapists from clubs engaged in the two main divisions of Brazilian men's football. Practices for assessment and rehabilitation of athletes with HIS were used as main outcome measures. This survey had 62 physical therapists from 35 of the 40 eligible clubs (87.5% representativeness). Despite heterogeneity on assessment practices, all respondents use imaging exams, adopt injury classification scales, and evaluate aspects related to pain, range of motion, muscle strength, and functional status of athletes with HSI. Rehabilitation programs are usually divided into 3 to 4 phases. All respondents usually apply electrophysical agents and stretching in HSI rehabilitation programs, 98.4% apply strengthening exercises (93.5% include eccentrics), 96.8% manual therapy, 95.2% exercises that mimic the functional demands of football, and 93.5% lumbopelvic stabilization exercises. Muscle strength was the most reported return to play criterion (71% of respondents). The present study allowed the sports physical therapy community to become aware of the approaches usually adopted for management of athletes with HSI who play in the highest level of Brazilian men's football.



#2 Former participation in professional football as an occupation in patients with isolated REM sleep behavior disorder leading to a synucleinopathy: a case-control study

Reference: J Neurol. 2023 Mar 20. doi: 10.1007/s00415-023-11591-8. Online ahead of print.

Authors: Alejandra Collía, Alex Iranzo, Mónica Serradell, Amaia Muñoz-Lopetegi, Gerard Mayà, Joan Santamaría, Raquel Sánchez-Valle, Carles Gaig

Summary: Contact sports such as football are associated with late development of neurodegenerative diseases, in part due to the deleterious effect of repetitive head impacts during participation. Isolated REM sleep behavior disorder (IRBD) represents an early manifestation of neurodegenerative diseases including Parkinson disease (RBD) and dementia with Lewy bodies (DLB). We hypothesized that former professional football participation would be overrepresented in IRBD. The aim was o assess former participation in professional football as an occupation in IRBD. In a case-control retrospective study, having played football as a professional occupation in the Spanish Football Professional Leagues was examined interviewing polysomnographically confirmed IRBD patients and matched controls without IRBD. Among 228 Caucasian Spanish IRBD patients with 68.5 ± 7.2 years, six (2.63%) were retired professional footballers. Length professional football career ranged between 11 and 16 years. Interval between football retirement and IRBD diagnosis was 39.5 ± 6.4 years. At IRBD diagnosis, the six footballers had synucleinopathy biomarkers including pathologic synuclein in the CSF and tissues, nigrostriatal dopaminergic deficit and hyposmia. Follow-up showed that three footballers developed PD and two DLB. None of the controls was a professional footballer. The percentage of professional footballers was higher in IRBD patients than in controls (2.63% versus 0.00%; p = 0.030) and among the general Spanish population (2.63% versus 0.62%; p < 0.0001). We found an overrepresentation of former professional footballers in IRBD patients who later developed PD and DLB after four decades from professional retirement. In professional footballers the development of a neurodegenerative disease may be first manifested by IRBD. Screening for IRBD in former footballers might identify individuals with underlying synucleinopathies. Further studies with larger samples are needed to confirm our observations.



#3 The Effect of cam and pincer morphology on hamstring injury rates and return to play in elite young male football players

Reference: Acta Orthop Traumatol Turc. 2023 Jan;57(1):36-39. doi: 10.5152/j.aott.2023.22115.

Authors: Engin Dinç, Serdar Arslan, Mahsum Akıkol

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Summary: This study aimed to determine the effects of cam and pincer morphology on the hamstring injury rate, treatment duration, and recurrence number of elite young male football players. Seventy-five elite young male football players were included in this study. Participants were evaluated physically and radiologically for femoroacetabular impingement during pre-season or pre-transfer routine health examinations. Athletes' injury and treatment data for 6 seasons were then collected prospectively and evaluated retrospectively. Athletes were divided into 2 groups: patients with cam and pincer morphology (group 1) and those without (group 2). Both groups were compared regarding the number of hamstring injuries, treatment duration, and recurrence numbers. The mean age was 20.35 ± 1.37 in group 1 (n = 23) and 18.92 ± 1.48 in group 2 (n = 52). There was a significant difference between the 2 groups regarding age and body weight. The rate of hamstring injuries in group 1 was higher than in group 2, and this difference was statistically significant. Although the recurrence rate (group 1-35.7%, group 2-27.8%) and treatment duration (group 1: 18.4 ± 10.1 days, group 2: 12.1 ± 6.2) in group 1 were higher than in group 2, there was no statistical significance between 2 groups. The present study has shown that hamstring injuries are more common in elite young male football players with cam and pincer morphology than those without. Therefore, further studies of musculoskeletal dysfunctions of femoroacetabular origin should be considered in the programs prepared to prevent and treat hamstring injuries.



#4 Maximum proportion of masks worn: Collaborative efforts in Japanese professional football

Reference: J Infect Public Health. 2023 Mar 15;S1876-0341(23)00090-4. doi: 10.1016/j.jiph.2023.03.009.

Authors: Tetsuo Yasutaka, Masaki Onishi, Wataru Naito, Yoshiaki Bando, Tomoaki Okuda, Michio Murakami

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Summary: Mass gathering events in Japan have gradually mitigated their novel coronavirus disease (COVID-19) control regulations, along with a minimum infection risk. The Japan Professional Football League (J.League) conducted pilot surveys on holding events with chant cheers. In this commentary, we introduce the collaborative efforts based on scientific knowledge among experts, J.League, and their fans. We performed risk assessment in advance, by updating a previously developed model. We further observed the average proportion of masks worn, chant cheering time of participants, and CO2 levels in the stand. The number of new COVID-19 cases in an event with 5,000 chant cheering participants and 35,000 non-chant cheering participants was estimated to be 1.02 times of an event, with 40,000 non-chant cheering participants. The average proportion of masks worn during the game was 98.9 %, for chant cheer participants. The chant cheering participants spent 50.0-51.1 % of their time chant cheering. Monitored average CO2 levels were ≤ 540 ppm, suggesting high ventilation rates in the stand. The high proportion of masks worn represents the willingness of norm-conscious fans to cooperate in regular recovery of the sport. This has proved to be one of the successful models for future mass gathering events.



#5 Patellofemoral Pain, Q-Angle, and Performance in Female Chinese Collegiate Soccer Players

Reference: Medicina (Kaunas). 2023 Mar 16;59(3):589. doi: 10.3390/medicina59030589.

Authors: Songhui You, Yinhao Shen, Qingguang Liu, Antonio Cicchella

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Summary: Female sports injuries have been neglected by science, and few relevant studies have considered female subjects. Knee pain in female soccer players is more common than in male soccer players. The number of days of absence from training and competition has been shown to be higher in females than males. The reporting of knee pain is common in female soccer players, but whether knee pain is associated with morphological features is unclear. The Q-angle of the knee has been hypothesized to be a causal factor in knee pain. Asian females have shown higher levels of valgus than non-sporting Caucasian populations, but no data exist for female Chinese players. The aim of our study was to investigate whether there are associations between knee pain, the Q-angle of the lower limb, jump performance, play time, and perceived exertion in female Chinese collegiate soccer players. We measured the Q-angle, patellofemoral/anterior knee pain (SNAPPS questionnaire), and CMJ and SJ performance of 21 subjects (age: 20.09 ± 1.13 years, weight: 56.9 ± 6.26 kg, height: 164.24 ± 4.48 cm, and >10 years of practice) before and after a match; Borg scale and play time results were also recorded. We found that our studied group had higher Q-angles in comparison to other ethnic groups reported in the literature, as well as an association of the Q-angle with the age, height, and weight of the players; however, contrary to other studies, we did not find any association between the Q-angle and knee pain, jumps, play time, or perceived exertion. Knee pain was not associated with any of the measured variables. Female Chinese soccer players showed higher Q-angles than players of other ethnic groups, a result that was associated with anthropometrics. The Q-angle was not found to be associated with knee pain, for which the sole determinant was body height.



#6 A Soccer Shot with Lengthy Consequences-Case Report & Current Literature Review of Commotio Cordis

Reference: J Clin Med. 2023 Mar 16;12(6):2323. doi: 10.3390/jcm12062323.

Authors: Philipp Spitaler, Markus Stühlinger, Agne Adukauskaite, Axel Bauer, Wolfgang Dichtl

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Summary: Commotio cordis, caused by objects being directly delivered to the chest, may cause cardiac arrest in young athletes, even without identifiable structural damage to the sternum, ribs or heart itself. Its prevention and management often remain suboptimal, resulting in dismal outcomes.  A 32-year semi-professional goalkeeper suffered from a non-penetrating blunt thoracic trauma after being struck by a high-velocity shot during a regional league soccer game. He immediately lost consciousness, collapsed, and was successfully resuscitated through early defibrillation of ventricular fibrillation. After an uneventful follow-up for approximately 6 years, recurrent episodes of ventricular tachycardia occurred, which could ultimately only be prevented by epicardial ablation. Very late recurrences of ventricular tachyarrhythmias may occur after ventricular fibrillation due to blunt chest trauma, even in the primary absence of evident structural myocardial damage.



#7 Association between Soccer Participation and Liking or Being Proficient in It: A Survey Study of 38,258 Children and Adolescents in China

Reference: Children (Basel). 2023 Mar 16;10(3):562. doi: 10.3390/children10030562.

Authors: Yibo Gao, Xiang Pan, Huan Wang, Dongming Wu, Pengyu Deng, Lupei Jiang, Aoyu Zhang, Jin He, Yanfeng Zhang

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Summary: Soccer participation among children and adolescents is low in China. To achieve a coordinated development of soccer in all regions and to promote the physical health of children and adolescents, this study aims to identify the influencing factors regarding the participation of children and adolescents in soccer programs through a cross-sectional analysis of the "soccer population" of children and adolescents. A total of 38,258 children and adolescents aged 7-18 years were included in this study. In addition, the analysis was conducted by dividing the regions where the children and adolescents live into three parts according to socioeconomic status, and by incorporating five dimensions, including environment, family, school, community, and individual levels to find the influencing factors of children and adolescents' participation in soccer. Chi-square test, Pearson's correlation, and one-way logistic regression analyses were used. The results showed that the area (r = 0.487) and the average annual precipitation (r = -0.367) were associated with the participation of children and adolescents in soccer programs. Moreover, the percentage of children and adolescents who participated in soccer programs (24.5%) was higher than those who liked soccer or were proficient in it (14.4%). Meanwhile, parental encouragement and support (OR = 0.627; 95% CI, 1.102-3.179), as well as the accessibility (OR = 0.558; 95% CI, 1.418-2.155), availability (OR = 1.419; 95% CI, 1.179-1.707), and safety of sports facilities (OR = 0.316; 95% CI, 0.614-0.865), influence children and adolescents' participation in soccer programs.



#8 Association between 2D:4D ratios and sprinting, change of direction ability, aerobic fitness, and cumulative workloads in elite youth soccer players

Reference: BMC Sports Sci Med Rehabil. 2023 Mar 28;15(1):45. doi: 10.1186/s13102-023-00654-y.

Authors: Hadi Nobari, Özgür Eken, Pablo Prieto-González, Rafael Oliveira, João Paulo Brito

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Summary: The aim of this study was two-fold: (i) to determine the correlation between 2D:4D, maximal oxygen uptake (VO2max), body fat percentage (BF%), maximum heart rate (HRmax), change of direction (COD), and accumulated acute and chronic workload variables; (ii) to verify if the length of the second digit divided by fourth digit (2D:4D) can explain fitness variables and accumulated training load. Twenty elite young football players (age: 13.26 ± 0.19 years; height: 165.8 ± 11.67 cm; body mass: 50.70 ± 7.56 kg; VO2max, 48.22 ± 2.29 1.min- 1) participated in the present study. Anthropometric and body composition variables (e.g., height, body mass, sitting height, age, BF%, body mass index, right and left finger 2D:4D ratios) were measured. The following fitness tests were also conducted: 30 - 15 Intermittent Fitness Test (VO2max and HRmax), COD (5-0-5 agility test), and speed (10-30msprint test. HRmax and the training load were also measured and monitored using the Rate of Perceived Exertion during the 26 weeks. There were associations between HRmax and VO2max, between 2D and 4D lengths and Left and Right hand ratios. Also, in AW with Right and Left 4D. The CW and de ACWR with the Right 4D. There were other associations between physical test variables and workload variables. Under-14 soccer players with low right and left-hand 2D:4D ratios did not perform better in the selected fitness tests to assess VO2max, COD, or sprint ability. However, it cannot be ruled out that the absence of statistically significant results may be related to the small sample size and the maturational heterogeneity of the participants.



#9 The role of working memory capacity in soccer tactical decision making at different levels of expertise

Reference: Cogn Res Princ Implic. 2023 Mar 29;8(1):20. doi: 10.1186/s41235-023-00473-2.

Authors: Dragan Glavaš, Mario Pandžić, Dražen Domijan

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Summary: Athletic skills acquired through deliberate practice are essential for expert sports performance. Some authors even suggest that practice circumvents the limits of working memory capacity (WMC) in skill acquisition. However, this circumvention hypothesis has been challenged recently by the evidence that WMC plays an important role in expert performance in complex domains such as arts and sports. Here, we have used two dynamic soccer tactical tasks to explore the effect of WMC on tactical performance at different levels of expertise. As expected, professional soccer players exhibited better tactical performance than amateur and recreational players. Furthermore, WMC predicted faster and more accurate tactical decisions in the task under auditory distraction and faster tactical decisions in the task without distraction. Importantly, lack of expertise × WMC interaction suggests that the WMC effect exists at all levels of expertise. Our results speak against the circumvention hypothesis and support a model of independent contributions of WMC and deliberate practice on expert performance in sports.



#10 Video analysis of Achilles tendon ruptures in professional male football (soccer) reveals underlying injury patterns and provides strategies for injury prevention

Reference: Knee Surg Sports Traumatol Arthrosc. 2023 Mar 28. doi: 10.1007/s00167-023-07384-1.

Authors: Tim Hoenig, Thomas Gronwald, Karsten Hollander, Christian Klein, Karl-Heinz Frosch, Peter Ueblacker, Tim Rolvien

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Summary: In professional football (soccer), Achilles tendon ruptures are severe injuries. Video analysis promotes a better understanding of the underlying situational and biomechanical patterns, and provides a roadmap for future research to improve the management and prevention of Achilles tendon ruptures. The purpose of this study was to identify injury patterns contributing to acute Achilles tendon ruptures in professional male football players. Professional male football players with an acute Achilles tendon rupture were identified using an online database. For every in-competition injury, the corresponding football match was detected. Video footage of the injury was accessed using or publicly available video databases. Situational patterns and injury biomechanics of the injury frame were independently analysed by two reviewers using a standardised checklist and a motion analysis software. Finally, consensus was reached to describe the main injury patterns of Achilles tendon ruptures in professional male football players. The search identified video footage of 80 Achilles tendon ruptures in 78 players. Most injuries (94%) occurred through indirect or non-contact mechanisms. The kinematic analysis revealed characteristic joint positions at the time of injury consisting of hip extension, knee extension, ankle dorsiflexion, foot abduction, and foot pronation in most cases. The underlying direction of movement was from flexion to extension (knee) and from plantarflexion to dorsiflexion (ankle). Player actions identified as main injury patterns were stepping back (26%), landing (20%), running/sprinting (18%), jumping (13%), and starting (10%). Most Achilles tendon ruptures in professional male football players are closed-chain indirect or non-contact injuries. Sudden loading to the plantarflexor musculotendinous unit remains to be the main component for most cases. By achieving a better understanding of underlying injury mechanisms, this study provides new strategies for the prevention of Achilles tendon ruptures.



#11 Effects of Concurrent High-Intensity and Strength Training on Muscle Power and Aerobic Performance in Young Soccer Players during the Pre-Season

Reference: Sports (Basel). 2023 Mar 6;11(3):59. doi: 10.3390/sports11030059.

Authors: Pierros Thomakos, Konstantinos Spyrou, Christos Katsikas, Nikolaos D Geladas, Gregory C Bogdanis

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Summary: The aim of the present study was to evaluate two different intervention programs applied during a 4-week pre-season period. Twenty-nine players participated in this study and were divided into two groups. One group (BallTrain, n = 12, age: 17.8 ± 0.4 years, body mass: 73.9 ± 7.6 kg, height: 178 ± 0.1 cm, body fat: 9.6 ± 5.3%) performed a higher percentage of aerobic training with ball and strength training using plyometrics and exercises with body weight. The other group (HIITTrain, n = 17, age: 17.8 ± 0.7 years, body mass: 73.3 ± 5.0 kg, height: 179 ± 0.1 cm, body fat: 8.0 ± 2.3%) trained with high-intensity interval training (HIIT) without the ball and performed resistance training with weights in the same session. Both groups trained for strength (two times/week) and performed aerobic-anaerobic fitness without the ball, passing games, and tactical and small-sided games. Lower limb power (CMJ) and aerobic fitness (Yo-Yo intermittent recovery test level 1-IR1) were evaluated before and after the four-week training program. Yo-Yo IR1 performance was improved in both groups, but the improvement was greater for the HIITTrain than BallTrain group (468 ± 180 vs. 183 ± 177 m, p = 0.07). CMJ showed a non-significant improvement in the BallTrain group (5.8 ± 8.8%, p = 0.16), but it decreased by 8.1 ± 9% (p = 0.001), in the HIITTrain group. In conclusion, we have shown that a short pre-season period of training results in improvements in aerobic fitness in both groups, with high-intensity interval training showing superior adaptations than training with the ball. However, CMJ performance was reduced in this group, possibly suggesting higher fatigue levels and overload, and/or showing the effects of concurrent HIITTrain and strength training in soccer.



#12 A data-driven framing of player and team performance in U.S. Women's soccer

Reference: Front Sports Act Living. 2023 Mar 8;5:1125528. doi: 10.3389/fspor.2023.1125528. eCollection 2023.

Authors: Sachin Narayanan, N David Pifer

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Summary: In establishing historical benchmarks for success on the pitch and striving to achieve parity off it, the United States Women's National Team (USWNT) and the National Women's Soccer League (NWSL) have long served as standard bearers for professional women's soccer around the globe. However, off-field dilemmas and incessant juxtapositions to men's soccer frequently overshadow the elements that make U.S. women's soccer unique; that is, in the quest to expose and rid the women's game of blatant misconduct, discriminatory practices, and negative stereotypes, relatively little attention has been devoted to performance features that separate the U.S. women's soccer product from its competition. Because many of the issues hindering the progress of women's soccer are rooted in media and managerial practices that marginalize or ignore its positive traits, a need exists for analyses that will properly identify its innate characteristics and competitive advantages so that media members, managers, and fans can accurately frame their perceptions of women competing in the sport. To this end, we collected reliable samples of public event data from 560 professional soccer matches and used ANOVAs and t-tests to identify the characteristics that distinguish U.S. women's soccer from other professional leagues and teams. In doing so, we showed that the USWNT tends to shoot from more opportune areas and press opponents at a higher rate, and that the NWSL has recently been matched in quality across certain performance metrics by England's FA Women's Super League.



#13 More than just a side effect: Dynamic knee valgus and deadbug bridging performance in youth soccer players and alpine skiers have similar absolute values and asymmetry magnitudes but differ in terms of the direction of laterality

Reference: Front Physiol. 2023 Mar 8;14:1129351. doi: 10.3389/fphys.2023.1129351. eCollection 2023.

Authors: Jonas Hanimann, Lynn Ellenberger, Thomas Bernhard, Martino V Franchi, Ralf Roth, Oliver Faude, Jörg Spörri

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Summary: From a preventative perspective, leg axis and core stabilization capacities are important for soccer players and alpine skiers; however, due to different sport-specific demands, the role of laterality clearly differs and may result in functional long-term adaptations. The aims of this study are 1) to determine whether there are differences in leg axis and core stability between youth soccer players and alpine skiers and 2) between dominant and non-dominant sides, and 3) to explore the outcomes of applying common sport-specific asymmetry thresholds to these two distinct cohorts. Twenty-one highly trained/national-level soccer players (16.1 years, 95% CI: 15.6, 16.5) and 61 alpine skiers (15.7 years, 95% CI: 15.6, 15.8) participated in this study. Using a marker-based 3D motion capture system, dynamic knee valgus was quantified as the medial knee displacement (MKD) during drop jump landings, and core stability was quantified as the vertical displacement during deadbug bridging exercise (DBB displacement ). For the analysis of sports and side differences, a repeated-measures multivariate analysis of variance was used. For the interpretation of laterality, coefficients of variation (CV) and common asymmetry thresholds were applied. There were no differences in MKD or DBB displacement between soccer players and skiers or between the dominant and non-dominant sides, but there was an interaction effect side*sports for both variables (MKD: p = 0.040, η2 p = 0.052; DBB displacement : p = 0.025, η2 p = 0.061). On average, MKD was larger on the non-dominant side and DBB displacement laterality on the dominant side in soccer players, whereas this pattern was reversed in alpine skiers. Despite similar absolute values and asymmetry magnitudes of dynamic knee valgus and deadbug bridging performance in youth soccer players and alpine skiers, the effect on the direction of laterality was opposite even though much less pronounced. This may imply that sport-specific demands and potential laterality advantages should be considered when dealing with asymmetries in athletes.



#14 Clinical Outcomes After ACL Reconstruction in Soccer (Football, Futbol) Players: A Systematic Review and Meta-Analysis

Reference: Sports Health. 2023 Mar 29;19417381231160167. doi: 10.1177/19417381231160167.

Authors: Ian S Hong, Lauren A Pierpoint, Justin E Hellwinkel, Alexander N Berk, Jonathan M Salandra, Joshua D Meade, Dana P Piasecki, James E Fleischli, Christopher S Ahmad, David P Trofa, Bryan M Saltzman

Summary: The risk factors for anterior cruciate ligament (ACL) tear for athletes participating in pivoting sports includes young age and female sex. A previous meta-analysis has reported a reinjury rate of 15% after ACL reconstruction (ACLR) for athletes across all sports. To the best of the authors' knowledge, this is the first systematic review and meta-analysis of available literature reporting outcomes after ACLR in soccer players. The aim was to review and aggregate soccer-specific outcomes data after ACLR found in current literature to help guide a more tailored discussion regarding expectations and prognosis for soccer players seeking operative management of ACL injuries. A comprehensive search of publications was performed using PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and SPORTDiscus databases. Inclusion criteria consisted of original studies, level of evidence 1 to 4, studies reporting clinical and patient-reported outcomes (PROs) after primary ACLR in soccer players at all follow-up length. The primary outcomes of interest were graft failure/reoperation rates, ACL injury in contralateral knee, return to soccer time, and PROs. Search of literature yielded 32 studies for inclusion that involved 3112 soccer players after ACLR. The overall graft failure/reoperation rate ranged between 3.0% and 24.8% (mean follow-up range, 2.3-10 years) and the combined ACL graft failure and contralateral ACL injury rate after initial ACLR was 1.0% to 16.7% (mean follow-up range, 3-10 years); a subgroup analysis for female and male players revealed a secondary ACL injury incidence rate of 27%, 95% CI (22%, 32%) and 10%, 95% CI (6%, 15%), respectively. Soccer players were able to return to play between 6.1 and 11.1 months and the majority of PROs showed favorable scores at medium-term follow-up.



#15 Association of Nonconcussive Repetitive Head Impacts and Intense Physical Activity With Levels of Phosphorylated Tau181 and Total Tau in Plasma of Young Elite Soccer Players

Reference: JAMA Netw Open. 2023 Mar 1;6(3):e236101. doi: 10.1001/jamanetworkopen.2023.6101.

Authors: Martin Cente, Janka Perackova, Pavol Peracek, Marek Majdan, Igor Toth, Martin Mikulic, Jozef Hanes, Sara Porubska, Marian Spajdel, Barbora Kazickova, Igor Jurisica, Peter Filipcik

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Summary: Head impacts resulting in traumatic brain injury (TBI) lead to the elevation of phosphorylated tau protein (p-tau181) in plasma. To our knowledge, this study is the first to investigate dynamics of p-tau181 levels and the ratio of p-tau181 to total tau in individuals after nonconcussive head impacts. The aim was o determine the association of repetitive low-intensity head impacts on p-tau181 and total tau protein levels in the plasma of young adult elite soccer players and assess the possible association of head impacts with focused attention and cognitive flexibility. In this cohort study, young elite soccer players performed intense physical activity with and without heading the ball. The study was conducted at a university facility in Slovakia from October 1, 2021, to May 31, 2022. Eligible participants were selected based on similarities in demographic variables, excluding those with a history of TBI. The primary study outcomes were the levels of total tau protein and p-tau181 in plasma samples and the cognitive status of the study participants. A total of 37 male athletes participated in the study (mean [SD] age: exercise group, 21.6 [1.6] years; heading group, 21.2 [1.5] years). We found significantly elevated levels of total tau and p-tau181 in the plasma of soccer players 1 hour after physical exercise (tau, 1.4-fold; 95% CI, 1.2-1.5; P < .001; p-tau181, 1.4-fold; 95% CI, 1.3-1.5, P < .001) and repetitive head impacts (tau, 1.3-fold; 95% CI, 1.2-1.4; P < .001; p-tau181, 1.5-fold; 95% CI, 1.4-1.7 P < .001). The ratio of p-tau181 to tau was significantly higher 1 hour after exercise and heading training, and remained elevated specifically in the heading group even after 24 hours (1.2-fold; 95% CI, 1.1-1.3; P = .002). Performance in cognitive tests revealed a significant decline in focused attention and cognitive flexibility after physical exercise and heading training; physical exercise of higher intensity without heading training was associated with a greater negative cognitive performance than heading only. In this cohort study of young elite soccer players, the elevation of p-tau181 and tau was observed after acute intense physical activity and nonconcussive repetitive head impacts. The increase of p-tau181 levels relative to tau after 24 hours indicated an acute enrichment of phosphorylated tau fraction in the periphery when compared with preimpact levels; an imbalance of tau proteins may have long-lasting consequences in the brain of head-impacted individuals.



#16 Developmental stage and lower quadriceps flexibilities and decreased gastrocnemius flexibilities are predictive risk factors for developing Osgood-Schlatter disease in adolescent male soccer players

Reference: Knee Surg Sports Traumatol Arthrosc. 2023 Mar 31. doi: 10.1007/s00167-023-07378-z.

Authors: Seira Takei, Suguru Torii, Shuji Taketomi, Satoshi Iizuka, Michio Tojima, Soichiro Iwanuma, Yukako Iida, Sakae Tanaka

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Summary: This study aimed to elucidate the influential predictive risk factors of Osgood-Schlatter disease (OSD) on the support (non-kicking) leg among adolescent soccer players considering peak height velocity (PHV) age and investigate the cut-off values of the predictive variables. A cohort of 302 Japanese adolescent male soccer players aged 12-13 years were followed over 6 months. All players underwent physical examination, tibial tubercle ultrasonography, anthropometric and whole-body composition measurements, and muscle flexibility test of the support leg at the baseline. The developmental stage was evaluated from the PHV age. The OSD of the support leg was diagnosed 6 months later; players were divided into the OSD and control (CON) groups. The predictive risk factors were analyzed by multivariate logistic regression analysis. There were 42 players who had developed OSD at baseline and they were excluded from the study. Among the 209 players, 43 and 166 belonged to the OSD and CON groups, respectively. The predictive risk factors of OSD development were PHV age ± 6 months at baseline (p = 0.046), apophyseal stage of tibial tuberosity maturity at baseline (p < 0.001), quadriceps flexibility ≥ 35° at baseline (p = 0.017), and decrease in gastrocnemius flexibility in 6 months (p = 0.009). PHV age ± 6 months at baseline, apophyseal stage of the tibial tuberosity at baseline, quadriceps flexibility ≥ 35° at baseline, and decrease in gastrocnemius flexibility in 6 months are predictive risk factors of OSD development in the support leg among adolescent male soccer players. It is crucial to know the PHV age of each player, and not only the flexibility of quadriceps muscle but also the gastrocnemius should be monitored to predict OSD.



#17 The effects of a 1-year recreational football protocol on bone health parameters in a group of healthy inactive 50-year-old men

Reference: J Clin Densitom. 2023 Mar 17;S1094-6950(23)00018-5. doi: 10.1016/j.jocd.2023.03.007.

Authors: Boutros Finianos, Antonio Pinti, Rawad ElHage

Summary: The main aim of the current study was to explore the effects of a 1-year recreational football protocol on bone health parameters (bone mineral content (BMC), bone mineral density (BMD), femoral neck geometry and composite indices of femoral neck strength) in a group of healthy inactive 50-year-old men. 51 middle-aged men voluntarily participated in this study, but only 41 of them completed it. Thus, the study population included 11 former football (FF) players and 30 inactive men. Inactive men were assigned to 3 different groups: controls (n=10), recreational football 30 (RF30; n=10) and recreational football 60 (RF60; n=10). The RF30 group performed two sessions of recreational football per week; the duration of each session was 30 minutes. The RF60 group performed two sessions of recreational football per week; the duration of each session was 60 minutes. The current study has demonstrated that whole body (WB) BMC, femoral neck BMD, cross-sectional moment of inertia, compression strength index, bending strength index and impact strength index increased in both experimental groups (RF30 and RF60) but not in the control group. The percentages of variations in bone health parameters were not significantly different between RF30 and RF60. In conclusion, this study suggests that recreational football is an effective method to improve bone health parameters in middle-aged men. In the studied population, most of the bone health benefits occurred after a low volume training protocol (2 * 30 minutes of recreational football per week).



#18 Cases of head injuries in football sport: A case study of Ghaziabad District, Uttar Pradesh

Reference: J Family Med Prim Care. 2022 Nov;11(11):6697-6703. doi: 10.4103/jfmpc.jfmpc_61_21. Epub 2022 Dec 16.

Authors: Kanishka Pandey

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Summary: In recent years public awareness of the potential long-term effects of concussions and mild traumatic brain injuries sustained in sport of football has increased. Players purposely use their head to direct the ball during play. There is a growing understanding of the link between blows to the head suffered in football and the potential for increased risk of injuries in later life.[1] This study aim is to reveal the similarities and differences the understanding of the link between blows to the head suffered in football and the potential for increased risk of injuries more specifically dementia in later life.[23] Heading an incorrect sized football can result in head injuries. As per FIFA guidelines a different sized football shall be used for different age groups. The schools in the Ghaziabad city were asked to fill in the questionnaires containing certain questions on Sports in general and football in particular. Descriptive and evaluative approach was used, which is generally used in comparative studies. The findings by various Universities established how heading can affect the brain, cognition, and speech of a person. It was found that a few developed nations like USA, England, Ireland have taken note of this issue and have issued guidelines based on the data and studies available. This study establishes that over-inflated footballs are being used in schools and also most of the schools have with them a single-sized football (which is against FIFA guidelines). Moreover, awareness of physical education instructors about different sizes of football and head injuries due to football is lacking. Also, clear guidelines on this issue are needed from the Ministry of Sports in India.



#19 Association between ACE and ACTN3 genes polymorphisms and athletic performance in elite and sub-elite Chinese youth male football players

Reference: PeerJ. 2023 Mar 24;11:e14893. doi: 10.7717/peerj.14893. eCollection 2023.

Authors: Shidong Yang, Wentao Lin, Mengmeng Jia, Haichun Chen

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Summary: Previous studies have shown controversial relationships between ACE I/D and ACTN3 R577x polymorphisms and athletic performance. Therefore, the aim of this study was to assess athletic performance indicators of Chinese youth male football players with different ACE and ACTN3 gene profiles. This study recruited 73 elite (26 13-year-olds, 28 14-year-olds, and 19 15-year-olds) and 69 sub-elite (37 13-year-olds, 19 14-year-olds, and 13 15-year-olds) and 107 controls (63 13-year-olds, and 44 14-year olds aged 13-15 years, all participants were of Chinese Han origin. We measured height, body mass, thigh circumference, speed, explosive power, repeat sprints ability, and aerobic endurance in elite and sub-elite players. We used single nucleotide polymorphism technology to detect controls elite and sub-elite players' ACE and ACTN3 genotypes, Chi-squared (χ 2) tests were employed to test for Hardy-Weinberg equilibrium. χ 2 tests were also used to observe the association between the genotype distribution and allele frequencies between controls and elite and sub-elite players. The differences in parameters between the groups were analyzed using one-way analysis of variance and a Bonferroni's post-hoc test, with statistical significance set at p ≤ 0.05. The genotype distribution of the ACE I/D and ACTN3 R577x polymorphisms in controls, elite and sub-elite football players were consistent with Hardy-Weinberg equilibrium, except for the ACE genotype distribution of sub-elite players.  The RR and DD genotypes were significantly different between elite and sub-elite players (p = 0.024 and p = 0.02, respectively).  Elite players were more likely to have the RR genotype and less likely to have the DD genotype compared with sub-elite players.  Both elite and sub-elite RR players' Yo-yo intermittent recovery level 1 (YYIR1) running distance was significantly longer than that of RX players (p = 0.05 and p = 0.025, respectively). However, there was no significantly different in YYIR1 running distance between elite and sub-elite RR players. Elite XX players' VO2 max was significantly higher than that of RX and sub-elite players. These results indicate that ACE I/D and ACTN3 R577x polymorphisms are not associated with muscle power in Chinese elite and sub-elite players. The XX genotype of ACTN3 is associated with the aerobic endurance of elite players.



#20 Examination of the ZXY Arena Tracking System for Association Football Pitches

Reference: Sensors (Basel). 2023 Mar 16;23(6):3179. doi: 10.3390/s23063179.

Authors: Jon Ingulf Medbø, Einar Ylvisåker

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Summary: Modern analyses of football games require precise recordings of positions and movements. The ZXY arena tracking system reports the position of players wearing a dedicated chip (transponder) at high time resolution. The main issue addressed here is the quality of the system's output data. Filtering the data to reduce noise may affect the outcome adversely. Therefore, we have examined the precision of the data given, possible influence by sources of noise, the effect of the filtering, and the accuracy of the built-in calculations. The system's reported positions of the transponders at rest and during different types of movements, including accelerations, were recorded and compared with the true positions, speeds, and accelerations. The reported position has a random error of ≈0.2 m, defining the system's upper spatial resolution. The error in signals interrupted by a human body was of that magnitude or less. There was no significant influence of nearby transponders. Filtering the data delayed the time resolution. Consequently, accelerations were dampened and delayed, causing an error of 1 m for sudden changes in position. Moreover, fluctuations of the foot speed of a running person were not accurately reproduced, but rather, averaged over time periods >1 s. Results calculated from measured values appeared accurate and were readily reproduced in a spreadsheet output. In conclusion, the ZXY system reports the position with little random error. Its main limitation is caused by averaging of the signals.





The influence of sprint performance, acceleration, and deceleration mechanical properties on change of direction ability in soccer

The study investigated the relationship between short sprint performance and mechanical parameters obtained during the acceleration and deceleration tasks with the change of direction (COD) performance in female and male soccer players.





The congested International Match Calendar in football: Views of 1055 professional male players

The International Match Calendar congestion affects players recovery. The views of a worldwide cohort of professional football players is shared in this communication.





Latest research in football - week 10 - 2023

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 Body Composition of Male Professional Soccer Players Using Different Measurement Methods: A Systematic Review and Meta-Analysis

Reference: Nutrients. 2023 Feb 25;15(5):1160. doi: 10.3390/nu15051160.

Authors: Jaime Sebastiá-Rico, Jose M Soriano, Noelia González-Gálvez, José Miguel Martínez-Sanz

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Summary: The performance of male soccer players (MSP) depends on multiple factors such as body composition. The physical demands of modern soccer have changed, so the ideal body composition (BC) requirements must be adapted to the present. The aim of this systematic review and meta-analysis was to describe the anthropometric, BC, and somatotype characteristics of professional MSP and to compare the values reported according to the methods and equations used. We systematically searched Embase, PubMed, SPORTDiscus, and Web of Science following the PRISMA statement. Random-effects meta-analysis, a pooled summary of means, and 95% CI (method or equation) were calculated. Random models were used with the restricted maximum likelihood (REML) method. Seventy-four articles were included in the systematic review and seventy-three in the meta-analysis. After comparing the groups according to the assessment method (kinanthropometry, bioimpedance, and densitometry), significant differences were found in height, fat mass in kilograms, fat mass percentage, and fat-free mass in kilograms (p = 0.001; p < 0.0001). Taking into account the equation used to calculate the fat mass percentage and ∑skinfolds, significant differences were observed in the data reported according to groups (p < 0.001). Despite the limitations, this study provides useful information that could help medical technical staff to properly assess the BC of professional MSP, providing a range of guidance values for the different BC.



#2 Hamstring muscle injury in football players - Part I : epidemiology, risk factors, injury mechanisms and treatment

Reference: Rev Med Liege. 2023 Mar;78(3):160-164.

Authors: François Delvaux, Jean-Louis Croisier, Christopher Carling, Emmanuel Orhant, Jean-François Kaux

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Summary: Due to its high frequency and recurrence rate, hamstring injury represents an important issue in football currently. The mechanisms of injury and the main modifiable and non-modifiable risk factors are now well documented and should allow the implementation of effective preventive strategies. In the treatment of the injured player, the physician will have to rely on a close collaboration with a quality sports physiotherapist and implement a series of key elements allowing an optimal return to the soccer field, which means at the same level of performance compared to the pre-injury period and with a minimal risk of recurrence. This article discusses these different elements in the form of a narrative review of the literature.



#3 Comparison of the Effects of Prebiotics and Synbiotics Supplementation on the Immune Function of Male University Football Players

Reference: Nutrients. 2023 Feb 25;15(5):1158. doi: 10.3390/nu15051158.

Authors: Lufang Zhang, Hui Xiao, Li Zhao, Zeting Liu, Lanmu Chen, Chenzhe Liu

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Summary: This study was conducted to compare the effects of long-term prebiotic and synbiotic supplementations on the immunosuppression of male football players after daily high-intensity training and a one-time strenuous exercise. A total of 30 male university student-athletes were recruited and randomly assigned to the prebiotic (PG, n = 15) or synbiotic group (SG, n = 15), receiving a prebiotic or synbiotic once per day for six weeks. Physiological assessments were conducted by a maximal oxygen uptake (VO2max) test and an exhaustive constant load exercise (75% VO2max test). Inflammatory cytokine and secretory immunoglobulin A (SIgA) were measured. VO2max, maximal heart rate (HRmax), and lactic acid elimination rate (ER) were used to evaluate aerobic capacity. Upper respiratory tract infection (URTI) complaints were evaluated using a questionnaire. URTI incidence and duration were significantly lower in the SG group than that in the PG group (p < 0.05). At baseline, SIgA and interleukin-1β (IL-1β) levels in the SG group (p < 0.01) as well as IL-1β and IL-6 in the PG group (p < 0.05) were significantly increased, and IL-4 concentration was markedly reduced in the PG group (p < 0.01). The concentrations of IL-4, IL-10 and transforming growth factor-β1 (TGF-β1) were significantly reduced in the PG and SG group immediately after the constant load exercise. Significantly decreased HRmax and enhanced ER (increased by 193.78%) were detected in the SG group, not in the PG group, during the constant load experiment (p < 0.05) and the recovery period (p < 0.01), respectively. However, VO2max value was not changed. These data suggest that synbiotic supplementation for six weeks has a more positive effect than prebiotics on the immune function and athletic performance of male university football players.



#4 Coaching, Mentorship, and Leadership Lessons Learned from Professional Football

Reference: Clin Sports Med. 2023 Apr;42(2):291-299. doi: 10.1016/j.csm.2022.11.009.

Authors: James M Whalen, Daryl J Nelson, Ryan J Whalen, Matthew T Provencher

Summary: Coaching, mentorship, and leadership are all paramount for the creation of a championship-winning football team. Looking back and studying the great coaches of professional football provides valuable insight into the qualities and the characteristics they possessed and how that impacted their leadership. Many of the great coaches from this game have instilled team standards and a culture that led to unprecedented success and sprouted into many other great coaches and leaders. Leadership at all levels of an organization is essential to consistently achieve a championship-caliber team.



#5 Type IX Superior Labrum Anterior and Posterior Lesion in a Professional Football Player: A Rare Pattern of Shoulder Instability in a Non-throwing Athlete

Reference: Cureus. 2023 Feb 7;15(2):e34753. doi: 10.7759/cureus.34753. eCollection 2023 Feb.

Authors: Edgar Amorim, Pedro Maganinho, Diogo Rodrigues-Gomes, Sérgio Rodrigues-Gomes, Nuno Sevivas

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Summary: Anterior shoulder instability is the most frequent type of glenohumeral instability, especially among young athletes. Superior labral anterior-posterior (SLAP) injuries involve the superior glenoid labrum where the long head of the biceps tendon (LHBT) inserts. There is still some debate regarding the pathogenesis, clinical presentation, and treatment of these lesions. We report a clinical case of an 18-year-old male professional football player with a rare type IX SLAP lesion. Given the recurrence of instability after prior nonoperative management, surgical treatment was seen as the best option, and a pan-labral arthroscopic repair suture anchor fixation was performed. Three months after undergoing a personalized postoperative rehabilitation program, he was able to return to full sport with the same competitive level, and no recurrent instability or other symptoms were reported throughout the 18-month follow-up period.



#6 Obstacles and opportunities for injury prevention in professional football in Qatar: exploring the implementation reality

Reference: BMJ Open Sport Exerc Med. 2023 Mar 10;9(1):e001370. doi: 10.1136/bmjsem-2022-001370. eCollection 2023.

Authors: Montassar Tabben, Evert Verhagen, Marit Warsen, Mokthar Chaabane, Yorck Schumacher, Khalid Alkhelaifi, Bahar Hassanmirzaei, Roald Bahr, Karim Chamari, Caroline Bolling

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Summary: Research focusing on reducing the risk of injuries has increased over the last two decades showing that prevention implementation in real life is challenging. The aim was to explore the experience and opinions of professional football stakeholders regarding injuries, their prevention and the implementation of preventive measures. Technical and medical staff from Qatar's premier football league with 22 professionals from 6 teams participated in this study. Seminstructured interviews were transcribed verbatim and analysed using the thematic analysis method. All the participants acknowledged the importance of injury prevention. They mentioned teamwork, trust and communication as critical factors for a successful injury prevention implementation. Teams' doctors see themselves mainly involved in the treatment and recovery process, and to a lesser degree, in the prevention process. Physiotherapists defined their primary responsibilities as screening for injury risk and providing individual exercises to players. The participants declared that the fitness coach is responsible for injury prevention implementation. All stakeholders reported that the fitness coach plays a vital role in communication by bridging the head coach and the medical staff. Stakeholders reported that the Qatari football league has a very particular context around the player, such as socioecological factors influencing injury prevention implementation. The fitness coach plays a vital role in the injury prevention implementation system, as one of the key actors for the process, as well as the bridge between the medical team and the head coach, resulting from their better communication with the head coaches. The findings support considering and understanding the contextual factors during the development of preventive strategies in football.



#7 Monitoring mood state to improve performance in soccer players: A brief review

Reference: Front Psychol. 2023 Feb 22;14:1095238. doi: 10.3389/fpsyg.2023.1095238. eCollection 2023.

Authors: Okba Selmi, Ibrahim Ouergui, Antonella Muscella, Danielle E Levitt, Katsuhiko Suzuki, Anissa Bouassida

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Summary: Psychological aspects of sport are key in maintaining athlete motivation and make a difference in competitive outcomes. Adjustments to training may be necessary according to athletes' emotional state. Therefore, it is important to assess and quantify mood states throughout the season in team sports, including among soccer players. The Profile of Mood States (POMS) is a widely used questionnaire that assesses emotional states characterized by positive or negative feelings and can be administered repeatedly to assess changes in mood state. This review aims to assess and summarize the current literature on mood state variation in soccer players with a specific focus on training loads, training modalities, and competitive performance. A literature search was systematically conducted and resulted in 156 records. After removing duplicates, items with irrelevant titles and abstracts were screened out, and full texts were then screened for relevance and compared with inclusion and exclusion criteria. The remaining 37 articles were included in the final qualitative synthesis. POMS scores were related to variability in training load, intensity of the training period, modality of training exercises, competitive performance and time of day in soccer players. Common recommendations include monitoring the mood state of soccer players during training sessions, matches, and throughout training periods to detect early signs of psychological disturbance and aid in optimizing high-level training performance. The POMS allows for monitoring of players' psychological state, providing coaches with data to aid in adjusting acute program variables according to players' psychological states and improve performance. Results offer practical support for the use of a simple POMS measurement as part of an overall program to monitor the players' psychological states. Results also highlight how training choices (i.e., load and exercise modality) and competitive performance are related to mood states (i.e., tension, anger, confusion, depression, fatigue, and vigor).



#8 The effects of repeated backward running training on measures of physical fitness in youth male soccer players

Reference: J Sports Sci. 2023 Mar 13;1-9. doi: 10.1080/02640414.2023.2184770. Online ahead of print.

Authors: Yassine Negra, Senda Sammoud, Aaron Uthoff, Rodrigo Ramirez-Campillo, Jason Moran, Helmi Chaabene

Summary: This study explored the effects of an 8-week repeated backward running training (RBRT) programme on measures of physical fitness in youth male soccer players. Youth male soccer players were randomly allocated into a RBRT group (n = 20; 13.95 ± 0.22y) or a control group (CG; n = 16; 14.86 ± 0.29y). The CG continued normal soccer training, while the RBRT group replaced some soccer drills with RBRT twice per week. Within-group analysis revealed that RBRT improved all performance variables (∆-9.99% to 14.50%; effect size [ES] = -1.79 to 1.29; p ≤ 0.001). Meanwhile, trivial-to-moderate detrimental effects on sprinting and change of direction (CoD) speed (∆1.55% to 10.40%; p ≤ 0.05) were noted in the CG. The number of individuals improving performance above the smallest worthwhile change ranged from 65-100% across all performance variables in the RBRT group, whereas<50% in the CG reached that threshold. The between-group analysis indicated that the RBRT group improved performance on all performance tasks more than the CG (ES = -2.23 to 1.10; p ≤ 0.05). These findings demonstrate that substituting part of a standard soccer training regimen with RBRT can enhance youth soccer players' sprinting, CoD, jumping, and RSA performance.



#9 Mild Hemophilia In A Competitive High School Soccer Player: A Case Report

Reference: J Athl Train. 2023 Mar 14. doi: 10.4085/1062-6050-0402.22. Online ahead of print.

Authors: Omole Oluwakorede, Reed Joan, Amy L Dunn, N Gleason Courtney

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Summary: In this case report, we discuss a case of a now 23-year-old athlete, diagnosed with mild hemophilia who successfully played varsity soccer throughout high school and continued to play intramural and club soccer while in college. A prophylactic protocol was developed by the athlete's hematologist to allow his safe participation in contact sports. Similar prophylactic protocols have been discussed by Maffet et al, that successfully allowed an athlete to participate in high level basketball. However, there still exist significant barriers to the athlete with hemophilia participating in contact sports. We discuss how athletes with adequate support networks can participate in contact sports. Decisions need to be made on a case-by-case basis and involve the athlete, family, team and medical personnel.



#10 How does the increase in foreign players affect football?

Reference: BMC Sports Sci Med Rehabil. 2023 Mar 15;15(1):32. doi: 10.1186/s13102-023-00643-1.

Authors: Ozan Sever, Erdem Ciğerci, Melih Öztop, Gökhan İpekoğlu, Süleyman Gönülateş, Zeki Akyildiz, Hadi Nobari

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Summary: In the study, we tried to analyze the effects of foreign players on Turkish Super League matches. For this purpose, in this long-term study, 1836 competition data played in 6 seasons between 2014 and 2020 was obtained from each year. Pearson's correlation coefficient applied between 18 different variables (goal, shoot, pass, cross, corner, offside, foul, yellow card, red card, accurate shot, percentage of the precise pass, rate of accurate access on opponent's field, the difference of ball possession percentage, shot difference, pass difference, big team superiority, home team superiority) and the number of foreign players (NoFP, active foreign players in 90 min.). In the Turkish Super League, within six seasons (2014-20), the NoFP in a match increased from 10.43 (38.06%) to 17.99 (64.26%). The increment was partially linear and statistically significant (F = 594.85) in all seasons. A positive association was found between NoFP several of passes (r = 0.219), percentage of accurate passes (r = 0.133), percentage of precise passes on the opponent's field (r = 0.139), exact pass difference between opponents (r = 0.114), and ball possession difference between opponents (r = 0.113). Fouls committed decreased with the increase of NoFP (r = -0.250). Although the win probability of the teams named The Big Three (Fenerbahçe, Galatasaray, and Beşiktaş) decreased from 67% (2014 season rate) to 50% in the last two seasons, no association was identified between the NoFP and big team superiority. Consequently, NoFP increment may improve the game quality by increasing accurate passes and passes in the opponent's field. The number of passes and the ball possession percentage difference between opponent teams may indicate that one team has control of the game by keeping possession or the other is tactically giving possession. These findings may suggest that the game evolved into half-field, tactical, set-play, possessioning competition. Analyzing variables such as game speed, intensity, the duration of the ball in play, running distance, energy consumption, and fatigue markers may light future studies.



#11 The relative age effect is widespread among European adult professional soccer players but does not affect their market value

Reference: PLoS One. 2023 Mar 23;18(3):e0283390. doi: 10.1371/journal.pone.0283390. eCollection 2023.

Authors: Eduard Bezuglov, Ryland Morgans, Mikhail Butovskiy, Anton Emanov, Larisa Shagiakhmetova, Bekzhan Pirmakhanov, Zbigniew Waśkiewicz, Artemii Lazarev

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Summary: The relative age effect (RAE) is most prevalent in highly competitive youth soccer and persists to a lesser extent in senior soccer. However, it is known that soccer players born in the second half of the year are as successful at senior level, indicating that they are equally talented although under-represented at youth level due to bias during the selection process, in which the emphasis is on more pronounced physical qualities in a specific period of time. Examining the prevalence of the RAE among professional soccer players depending on the level of competition and playing position, as well as analyzing the relationship between the player's birth quarter and market value, are of scientific interest. The dates of birth, playing position, and market value of all adult male soccer players included in the final rosters of teams from the top-division of 54 European countries, listed on on August 15th, 2020, were analyzed (18,429 soccer players in total). All players were categorized into four groups according to the quarter of birth (Q) and playing position. All teams were further sub-divided in groups depending on the soccer clubs' level of representation in the UEFA Champions League. Of 18,429 players, 30.9% were born in Q1, 25.7% in Q2, 23.8% in Q3 and 19.6% in Q4. The number of soccer players born in Q1 was lower in less competitive leagues. The number of players born in Q1 decreased as the level of competition decreased; the highest percentage of these players was observed in clubs that are among the top 50 ranked in UEFA or compete in the most prestigious European championships. The RAE was less pronounced in teams that participate in lower competitive championships. There was no significant difference in market value between players playing position and level of competition when born in different quarters. Although, the most expensive soccer players in the European championships were late-born forwards. Players of various groups differed in their market value. The RAE is currently prevalent in all the most competitive senior soccer leagues and teams in Europe regardless of playing position. There are no significant differences in market value between players of the same playing position and level of competition when born in different quarters. The most expensive soccer players in the European championships are forwards born in Q4. These findings may indicate that the under-representation of "late-born" soccer players in youth, and then consequently in adult soccer, is not associated with lower talent, but with other factors, possibly based on physiological characteristics and socio-cultural factors. Further measures are needed to mitigate the discriminatory effects of selection bias based on the RAE.



#12 Neurodegenerative disease among male elite football (soccer) players in Sweden: a cohort study

Reference: Lancet Public Health. 2023 Apr;8(4):e256-e265. doi: 10.1016/S2468-2667(23)00027-0. Epub 2023 Mar 16.

Authors: Peter Ueda, Björn Pasternak, Carl-Emil Lim, Martin Neovius, Manzur Kader, Magnus Forssblad, Jonas F Ludvigsson, Henrik Svanström

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Summary: Football (soccer) players might be at increased risk of neurodegenerative disease, which has led to questions regarding the safety of the sport and recent measures introduced by football associations to reduce heading of the ball. We aimed to assess the risk of neurodegenerative disease among male football players in the Swedish top division Allsvenskan, compared with matched controls. In this cohort study, we identified all male football players (amateurs and professionals) who had played at least one game in Allsvenskan from Aug 1, 1924 to Dec 31, 2019 and excluded players whose personal identity number could not be retrieved or be identified in the Total Population Register, and those who were not born in Sweden and who had immigrated to the country after age 15 years. Football players were matched with up to ten controls from the general population according to sex, age, and region of residence. We used nationwide registers to compare the risk of neurodegenerative disease (diagnoses recorded in death certificates, during hospital admissions and outpatient visits, or use of prescription drugs for dementia) among football players versus controls. We also assessed each type of neurodegenerative disease (Alzheimer's disease and other dementias, motor neuron disease, and Parkinson's disease) separately, and compared the risk of neurodegenerative disease among outfield players versus goalkeepers. Of 7386 football players who had played at least one game in the top Swedish division between Aug 1, 1924, and Dec 31, 2019, 182 players were excluded for an unretrievable personal identity number, and 417 were excluded due to their number not being identified in the Total Population Register. After a further exclusion of 780 players and 11 627 controls who were born outside of Sweden and who had immigrated to the country after age 15 years, 6007 football players (510 goalkeepers) were included in the study population along with 56 168 matched controls. During follow-up to Dec 31, 2020, 537 (8·9%) of 6007 football players and 3485 (6·2%) of 56 168 controls were diagnosed with neurodegenerative disease. The risk of neurodegenerative disease was higher among football players than controls (hazard ratio [HR] 1·46 [95% CI 1·33-1·60]). Alzheimer's disease and other dementias were more common among football players than controls (HR 1·62 [95% CI 1·47-1·78]), significant group differences were not observed for motor neuron disease (HR 1·27 [0·73-2·22]), and Parkinson's disease was less common among football players (HR 0·68 [0·52-0·89]). The risk of neurodegenerative disease was higher for outfield players than controls (HR 1·50 [95% CI 1·36-1·65]) but not for goalkeepers versus controls (HR 1·07 [0·78-1·47]), and outfield players had a higher risk of neurodegenerative disease than did goalkeepers (HR 1·43 [1·03-1·99]). All-cause mortality was slightly lower among football players than controls (HR 0·95 [95% CI 0·91-0·99]). In this cohort study, male football players who had played in the Swedish top division had a significantly increased risk of neurodegenerative disease compared with population controls. The risk increase was observed for Alzheimer's disease and other dementias but not for other types of neurodegenerative disease, and among outfield players, but not among goalkeepers. Our study expands on the data that can be used to assess and manage risks in the sport.



#13 Alive and kicking: suicide rates and major soccer events in Austria, Germany and Switzerland

Reference: Eur J Public Health. 2023 Mar 20;ckad042. doi: 10.1093/eurpub/ckad042. Online ahead of print.

Authors: Eva-Maria Pichler, Martin Ploederl, Lucas Rainer, Thomas S Gilhofer, Jonathan Michel, Jan Gerrit van der Stouwe, Thomas F Luescher, Christian M Schmied, Wolfram Kawohl, Jens Kronschnabel, David Niederseer

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Summary: Major sporting events are postulated to reduce suicide rates by increased social connectedness, by identifying with winning teams, or, conversely, to increase suicide rates by the 'broken promise effect'. In our observational epidemiological study, we investigated changes in suicide rates between 1970 and 2017 in Austria, Germany and Switzerland during the European and World Soccer Championships in general, and on days that the home team played, won or lost. Combining all three studied nations no statistically significant change in the incidence of daily suicides during soccer championships compared to a control period was noted (38.29 ± 9.02 vs. 37.33 ± 10.58; incidence risk ratio = 1.03; 95% confidence interval: 1.01-1.05, P = 0.05). Essentially, no differences in the expected directions were found, and none remained statistically significant after correcting for multiple comparisons in subgroups for country, age and gender in all three studied countries. Compared to a control period, neither a significant difference in the respective national suicide rate was found after Germany's four championship victories nor after Austria's emotional only win over Germany. Our results do not support the assumption of increased social connectedness and, thus, lowered suicide risk during major sporting events or changes in suicide risk depending on the outcome of important games as predicted by the broken promise effect or changes in self-efficacy by identification with winning teams.



#14 High-level soccer players have a low rate of return to performance after hip arthroscopy for femoroacetabular impingement syndrome

Reference: Knee Surg Sports Traumatol Arthrosc. 2023 Mar 22. doi: 10.1007/s00167-023-07336-9.

Authors: Sofie Sjövall Anari, Alexander Olsson, Axel Öhlin, Neel Desai, Eric Hamrin Senorski, Mikael Sansone, Ida Lindman

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Summary: Femoroacetabular impingement syndrome (FAIS) is a known cause of impaired sports performance in athletes and the relationship between FAIS and soccer players has previously been described. Hip arthroscopy is a viable treatment option that can facilitate athletes' return to sport (RTS). The aim of this study was to evaluate the RTS and return to performance (RTP) with objective measurements in high-level soccer players after hip arthroscopy for FAIS. Soccer players, with a hip sports activity scale (HSAS) level of 7 or 8 before symptom onset and undergoing hip arthroscopy for FAIS between 2011 and 2019 were identified in the Gothenburg hip arthroscopic registry. A total of 83 high-level soccer players, with a mean age of 23.9 (SD 4.4) years at surgery, were included. To verify the activity level and further stratify players as elite or sub-elite, player statistics were collected from soccer-specific scout webpages and the Swedish national soccer association. The return to sport was defined as return to one game of soccer. Return to performance was defined as playing at the same level, or higher, and participating in at least 80% of the number of games played the season before symptom onset or the season before surgery either the first or second season after hip arthroscopy. In total, 71 (85.5%, 95% confidence interval (CI) 76.1-92.3%) of the players returned to sport the first or second season after surgery. Compared to the season before symptom onset, 31 (37.3%, 95% CI 27.0-48.7%) players returned to performance the first or second season after surgery, and 32 (38.6%, 95% CI 28.1-49.9%) players returned to performance the first or second season after surgery compared to the season before surgery. A high rate of elite and sub-elite soccer players return to soccer after hip arthroscopy for FAIS. However, less than half of the players RTP when evaluating performance through level of play and number of games played.



#15 The Safe Landing warm up technique modification programme: An effective anterior cruciate ligament injury mitigation strategy to improve cutting and jump-movement quality in soccer players

Reference: J Sports Sci. 2023 Mar 23;1-11. doi: 10.1080/02640414.2023.2193451. Online ahead of print.

Authors: Jesús Olivares-Jabalera, Alberto Fílter, Thomas Dos Santos, José Ortega-Domínguez, Víctor M Soto Hermoso, Bernardo Requena

Summary: The objective of the study was to evaluate the effectiveness of the Safe Landing (SL), a 6-week technique-modification (TM) programme, on cutting and jump-landing movement quality in football players. In a non-randomized design, 32 male semi-professional football players from two Spanish clubs participated in the study: one served as the control group (CG, n = 11), while the other performed the SL (n = 15). Performance and movement quality of drop vertical jump and 70º change of direction (COD70) were evaluated through 2D video footage pre- and post-intervention. In such tasks, the Landing Error Scoring System for first (LESS1) and second (LESS2) landings, and the Cutting Movement Assessment Score (CMAS) were used for assessing movement quality. Pre-to-post changes and baseline-adjusted ANCOVA were used. Medium-to-large differences between groups at post-test were shown in CMAS, LESS1 and LESS2 (p < 0.082, ղ2 = 0.137-0.272), with small-to-large improvements in SL (p < 0.046, ES=0.546-1.307), and CG remaining unchanged (p > 0.05) pre-to-post. In COD70 performance, large differences were found between groups (p < 0.047, ղ2 = 0.160-0.253), with SL maintaining performance (p > 0.05, ES=0.039-0.420), while CG moderately decreasing performance (p = 0.024, ES=0.753) pre-to-post. The SL is a feasible and effective TM program to improve movement quality and thus potential injury risk in cutting and landing, while not negatively affecting performance.



#16 Using Social Network Analysis to Study Relationships Between Young Soccer Players' Bone Age, Body Size, and the Centrality of Their Pass Interactions

Reference: Percept Mot Skills. 2023 Mar 24;315125231165167. doi: 10.1177/00315125231165167.

Authors: Paulo Henrique Borges, Julio Cesar da Costa, Luiz Fernando Ramos-Silva, Felipe A Moura, Hélio Serassuelo Junior, Alexandre Moreira, Gibson Moreira Praça, Enio Ricardo Vaz Ronque

Summary: Prior research has suggested relevance to anthropometric variance of youth athletes at various stages of their maturation, and prior studies of youth players' soccer skills have failed to consider their interdependent interactions during play. Accordingly, to address both of these separate research omissions, we aimed in this study to analyze the relationships between young (U-13 and U-15 groups) soccer players' bone age and body size indicators and centrality measures of their pass interactions during small sided games. We included young 81 athletes (M age = 14.4, SD = 1.1 years) from whom we took anthropometric measurements of body mass, height, and trunk-cephalic height and obtained their bone age using the Tanner-Whitehouse 3 classification method. We also filmed small-sided games in the goal keeper/three player (GK3-3GK) format to analyze the centrality of their passing actions on the following measures: degree of centrality, closeness of centrality, degree of prestige, and proximity of prestige. There were no group differences in the prominence of passing actions across these three measures (tmean = -3.13; p > .05). Canonical correlations of these relationships were significant only in the U-13 group, in which centrality in passing actions was related to body size (r = 0.71; R2 = 0.21; ʌ = 0.28; p = .03). U-13 players who were physically larger and who presented higher bone age showed centralized main passing actions.



#17 Hard talk, costly walk: The evolution of a soft budget constraint syndrome in a football club at the periphery of Europe

Reference: Front Sports Act Living. 2023 Mar 7;5:1107988. doi: 10.3389/fspor.2023.1107988. eCollection 2023.

Authors: Bernt Arne Bertheussen

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Summary: A football club is exposed to a soft budget constraint (SBC) syndrome if it still survives after finding it impossible to break even financially in the long run. This in-depth case study presents a historical analysis of the evolution of an SBC syndrome in a top-tier Arctic football club over 30 years using public archive data. In oral speeches, strategy documents, and other official situations, the hierarchy at the club emphasized the importance of operating in a financially sustainable manner, that is, complying with a hard budget constraint approach (HBC). The club went along this path during the first years after entering the top tier in the mid-1980s. This was made possible by a team of low-cost local players. However, in line with increased media and sponsorship revenues in the 1990s, the economic threshold for competing at the top-level rose. Thus, during the last two decades of the club's financial history, the budget constraint (BC) approach softened. Primarily, a distant benefactor and capital injections from a joint-stock company owned mainly by the local bank and local energy company funded the overspending. Furthermore, the study uncovers how a soft financial control and monitoring system introduced by the national football association failed to emancipate the club from the SBC syndrome. The study finally suggests some measures that can eventually harden the BC at this as well as many other financially struggling European football clubs.



#18 The associations of transformational leadership and team cohesion on the psychological health of young football players through basic psychological needs

Reference: Sci Med Footb. 2023 Mar 27;1-10. doi: 10.1080/24733938.2023.2194287. Online ahead of print.

Authors: Sinan Yildirim, Alper Yildiz, Hande Türkeri Bozkurt, Emre Bilgin, Yılmaz Yüksel, Ziya Koruç

Summary: The present study examined the associations of transformational leadership behaviors and team cohesion with the psychological health (life satisfaction, positive and negative affect, and burnout) of athletes and the indirect relationship of basic psychological needs. The sample consisted of 252 (boys) players aged between 13 and 15. The model data fit was also verified. The results demonstrated that the transformational leadership behaviors of coaches were indirectly related to athletes' psychological health. Team cohesion was related to athletes' psychological health both directly and indirectly. Basic psychological needs played an indirect role in these relationships. Transformational leadership and team cohesion have important implications for the healthy development of young people.



#19 Assessment of left atrial morphological and functional differences in professional male football players: a prospective, case-control study

Reference: Cardiovasc J Afr. 2023 Mar 22;34:1-5. doi: 10.5830/CVJA-2023-010. Online ahead of print.

Authors: Sefa Gül, Hasan Güngör

Summary: Intensive physical activity in athletes leads to considerable changes in the morphology and physiology of the left atrium through physiological, exercise-induced remodelling. This study aimed to assess the mechanical and electrophysiological changes in professional football players using electrocardiographic and echocardiographic assessment tools. This prospective, case-control study was performed between February and June 2022. The population consisted of elite male football players (n = 49, group F) as the study group, and healthy male non-athlete individuals of matching age (n = 50, group C) as the control group. All participants underwent electrocardiographic and echocardiographic (two-dimensional and tissue Doppler) examinations. Volumetric and functional assessment of the left atrium was identified as the study's primary outcome. There was no significant difference between the groups in terms of demographic and morphometric characteristics (p > 0.05). Maximum and minimum P waves and PR-interval duration were significantly higher in group F than in group C (p = 0.011, p = 0.005 and p < 0.001). Diameter, maximum and minimum volumes of the left atrium, and their corresponding indexes were significantly increased in group F (p < 0.0). Ejection fraction of the left atrium was significantly lower in group F than in group C (p = 0.001). Pulmonary acceleration time and tricuspid annular plane systolic excursion was significantly higher in the football players (p = 0.023 and p < 0.001). Increased diameter, maximum and minimum volumes of the left atrium, and their corresponding indexes could be demonstrated in the elite football players. The morphological and functional changes in the left atrium might be a physiological consequence of left atrial cardiac remodelling to intensive and chronic training.



#20 How European Fans in Training (EuroFIT), a lifestyle change program for men delivered in football clubs, achieved its effect: a mixed methods process evaluation embedded in a randomised controlled trial

Reference: BMC Public Health. 2023 Mar 20;23(1):526. doi: 10.1186/s12889-023-15419-y.

Authors: Christopher Bunn, Victoria Palmer, Nai Rui Chng, Eivind Andersen, Cindy M Gray, Kate Hunt, Judith G M Jelsma, Heather Morgan, Maria Nijhuis-van der Sanden, Hugo V Pereira, Matthew Philpott, Glyn C Roberts, John Rooksby, Øystein B Røynesdal, Marlene N Silva, Marit Sørensen, Pedro J Teixeira, Theo van Achterberg, Irene van de Glind, Willem van Mechelen, Femke van Nassau, Hidde P van der Ploeg, Sally Wyke

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Summary: A randomised trial of European Fans in Training (EuroFIT), a 12-week healthy lifestyle program delivered in 15 professional football clubs in the Netherlands, Norway, Portugal, and the United Kingdom, successfully increased physical activity and improved diet but did not reduce sedentary time. To guide future implementation, this paper investigates how those effects were achieved. We ask: 1) how was EuroFIT implemented? 2) what were the processes through which outcomes were achieved? We analysed qualitative data implementation notes, observations of 29 of 180 weekly EuroFIT deliveries, semi-structured interviews with 16 coaches and 15 club representatives, and 30 focus group discussions with participants (15 post-program and 15 after 12 months). We descriptively analysed quantitative data on recruitment, attendance at sessions and logs of use of the technologies and survey data on the views of participants at baseline, post program and after 12 months. We used a triangulation protocol to investigate agreement between data from difference sources, organised around meeting 15 objectives within the two research questions. We successfully recruited clubs, coaches and men to EuroFIT though the draw of the football club seemed stronger in the UK and Portugal. Advertising that emphasized getting fitter, club-based deliveries, and not 'standing out' worked and attendance and fidelity were good, so that coaches in all countries were able to deliver EuroFIT flexibly as intended. Coaches in all 15 clubs facilitated the use of behaviour change techniques and interaction between men, which together enhanced motivation. Participants found it harder to change sedentary time than physical activity and diet. Fitting changes into daily routines, planning for setbacks and recognising the personal benefit of behaviour change were important to maintain changes. Bespoke technologies were valued, but technological hitches frustrated participants. EuroFIT was delivered as planned by trained club coaches working flexibly in all countries. It worked as expected to attract men and support initiation and maintenance of changes in physical activity and diet but the use of bespoke, unstable, technologies was frustrating. Future deliveries should eliminate the focus on sedentary time and should use only proven technologies to support self-monitoring and social interaction.






Testing the effects of 4-week training programs based on extreme and medium-sided soccer games

This study tested the effects of two training programs (1v1 vs. 5v5) on the physical fitness adaptations of youth soccer players. In specific, it was analyzed the effects of the training programs on the 5–0–5 change-of-direction time (5–0–5 time), countermovement jump (CMJ), and final velocity in the 30–15 Intermittent Fitness test (VIFT).





Effects of Age and Playing Tactics on the Individual Tactical Behavior in U10 and U12 Elite Spanish Soccer Players

The aim of this paper was to explore the effects of age and playing tactics on the individual tactical behavior and performance in young soccer players.





Latest research in football - week 9 - 2023

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 Peak match acceleration demands differentiate between elite youth and professional football players

Reference: PLoS One. 2023 Mar 1;18(3):e0277901. doi: 10.1371/journal.pone.0277901. eCollection 2023.

Authors: Bradley Thoseby, Andrew D Govus, Anthea C Clarke, Kane J Middleton, Ben J Dascombe

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Summary: Youth footballers need to be developed to meet the technical, tactical, and physical demands of professional level competition, ensuring that the transition between competition levels is successful. To quantify the physical demands, peak match intensities have been measured across football competition tiers, with team formations and tactical approaches shown to influence these physical demands. To date, no research has directly compared the physical demands of elite youth and professional footballers from a single club utilising common formations and tactical approaches. The current study quantified the total match and peak match running demands of youth and professional footballers from a single Australian A-League club. GPS data were collected across a single season from both a professional (n = 19; total observations = 199; mean ± SD; 26.7 ± 4.0 years) and elite youth (n = 21; total observations = 59; 17.9 ± 1.3 years) team. Total match demands and peak match running demands (1-10 min) were quantified for measures of total distance, high-speed distance [>19.8 km·h-1] and average acceleration. Linear mixed models and effect sizes identified differences between competition levels. No differences existed between competition levels for any total match physical performance metric. Peak total and high-speed distances demands were similar between competitions for all moving average durations. Interestingly, peak average acceleration demands were lower (SMD = 0.63-0.69) in the youth players across all moving average durations. The data suggest that the development of acceleration and repeat effort capacities is crucial in youth players for them to transition into professional competition.



#2 Validity and sensitivity of field tests' heart-rate recovery assessment in recreational football players

Reference: PLoS One. 2023 Mar 1;18(3):e0282058. doi: 10.1371/journal.pone.0282058. eCollection 2023.

Authors: Susana Póvoas, Peter Krustrup, Carlo Castagna

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Summary: We aimed at examining the criterion validity and sensitivity of heart-rate recovery (HRRec) in profiling cardiorespiratory fitness in male recreational football players in the untrained and trained status, using endurance field-tests. Thirty-two male untrained subjects (age 40 ± 6 years, VO2max 41.7 ± 5.7 ml·kg-1·min-1, body mass 82.7 ± 9.8 kg, stature 173.3 ± 7.4 cm) participated in a 12-week (2‒3 sessions per week) recreational football intervention and were tested pre- and post-intervention (i.e. untrained and trained status). The participants performed three intermittent field tests for aerobic performance assessment, namely Yo-Yo intermittent endurance level 1 (YYIE1) and level 2 (YYIE2) tests, and Yo-Yo intermittent recovery level 1 (YYIR1) test. VO2max was assessed by performing a progressive maximal treadmill test (TT) and maximal HR (HRmax) determined as the maximal value across the testing conditions (i.e., Yo-Yo intermittent tests or TT). HRRec was calculated as the difference between Yo-Yo tests' HRpeak or HRmax and HR at 30 s (HR30), 60 s (HR60) and 120 s (HR120) and considered as beats·min-1 (absolute) and as % of tests' HRpeak or HRmax values. Significant post-intervention improvements (p<0.0001) were shown in VO2max (8.6%) and Yo-Yo tests performance (23-35%). Trivial to small (p>0.05) associations were found between VO2max and HRRec (r = -0.05-0.27, p>0.05) across the Yo-Yo tests, and training status either expressed as percentage of HRpeak or HRmax. The results of this study do not support the use of field-test derived HRRec to track cardiorespiratory fitness and training status in adult male recreational football players.



#3 Energy expenditure, dietary intake and energy availability in female professional football players

Reference: BMJ Open Sport Exerc Med. 2023 Feb 23;9(1):e001553. doi: 10.1136/bmjsem-2023-001553. eCollection 2023.

Authors: Marcus Smavik Dasa, Oddgeir Friborg, Morten Kristoffersen, Gunn Pettersen, Guy Plasqui, Jorunn Kaiander Sundgot-Borgen, Jan H Rosenvinge

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Summary: The aim was to quantify energy expenditure and intake in professional female footballers playing on a national and/or international level. Second, to determine the prevalence of low energy availability among these players, defined as <30 kcal/kg fat-free mass (FFM)/day. Fifty-one players completed a 14-day prospective observational study during the 2021/2022 football season. Energy expenditure was determined using the doubly labelled water method. Energy intake was assessed using dietary recalls, while global positioning system determined the external physiological load. Descriptive statistics, stratification and the correlation between explainable variables and outcomes were conducted to quantify the energetic demands. The mean energy expenditure for all players (22±4 years) was 2918±322 kcal. Mean energy intake was 2274±450 kcal, resulting in a discrepancy of ~22%. Carbohydrate intake was below the recommended guidelines on match day at 4.5±1.9 g/kg. The mean energy availability was 36.7±17.7 kcal/kg FFM/day on matchday and 37.9±11.7 kcal/kg FFM/day on training days, resulting in a prevalence of 36% and 23% for low energy availability during the observational period, respectively. These elite female football players displayed moderate energy expenditure levels and failed to meet the recommended levels of carbohydrate intake. In conjunction with inadequate nutritional periodisation, this will likely hamper performance through inadequate muscle glycogen resynthesis. In addition, we found a considerable prevalence of low energy availability on match and training days.



#4 Epidemiology of Football Injuries of the German Bundesliga: A Media-Based, Prospective Analysis over 7 Consecutive Seasons

Reference: Sports Med Open. 2023 Mar 3;9(1):20. doi: 10.1186/s40798-023-00563-x.

Authors: Karen Aus der Fünten, Tobias Tröß, Abed Hadji, Florian Beaudouin, Ida Bo Steendahl, Tim Meyer

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Summary: This study describes the implementation of a standardised, prospective injury database covering the entire 1st male German football league ("Bundesliga") based on publicly available media data. For the first time, various media sources were used simultaneously as the external validity of media-generated data was low in the past compared to data obtained by way of the "gold standard", i.e. by the teams' medical staffs. The study covers 7 consecutive seasons (2014/15-2020/21). The primary data source was the online version of the sport-specific journal "kicker Sportmagazin™" complemented by further publicly available media data. Injury data collection followed the Fuller consensus statement on football injury studies. During the 7 seasons, 6653 injuries occurred, thereof 3821 in training and 2832 in matches. The injury incidence rates (IRs) per 1000 football hours were 5.5 [95% CI 5.3-5.6], 25.9 [25.0-26.9] per 1000 match, and 3.4 [3.3-3.6] per 1000 training hours. Twenty-four per cent of the injuries (n = 1569, IR 1.3 [1.2-1.4]) affected the thigh, 15% (n = 1023, IR 0.8 [0.8-0.9]) the knee, and 13% (n = 856, IR 0.7 [0.7-0.8]) the ankle. Muscle/tendon injuries contributed 49% (n = 3288, IR 2.7 [2.6-2.8]), joint/ligament injuries 17% (n = 1152, IR 0.9 [0.9-1.0]), and contusions 13% (n = 855, IR 0.7 [0.7-0.8]). Compared to studies using injury reports from the clubs' medical staff, media data revealed similar proportional distributions of the injuries, but the IRs tended towards the lower end. Obtaining specific locations or diagnosis especially with regard to minor injuries is difficult. Media data are convenient for investigating the quantity of injuries of an entire league, for identifying injuries for further subanalysis, and for analysing complex injuries. Future studies will focus on the identification of inter- and intraseasonal trends, players' individual injury histories, and risk factors for subsequent injuries. Furthermore, these data will be used in a complex system approach for developing a clinical decision support system, e.g. for return to play decisions.



#5 Design and Validation of a Test to Evaluate the Execution Time and Decision-Making in Technical-Tactical Football Actions (Passing and Driving)

Reference: Behav Sci (Basel). 2023 Jan 26;13(2):101. doi: 10.3390/bs13020101.

Authors: Guillermo Andres Calle-Jaramillo, Enoc Valentin Gonzalez-Palacio, Lewis Adrian Perez-Mendez, Andres Rojas-Jaramillo, Jose Antonio Gonzalez-Jurado

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Summary: Reaction time and decision-making (DMA) in football have usually been evaluated using edited images or videos of game situations. The purpose of this research is to design and validate a test that simultaneously evaluates execution time (ET) and decision-making (DMA) in the subcategories of type of action (TA) and direction of movement (DM). A quantitative, cross-sectional, and descriptive study of 30 young players. A total of 32 stimuli were programmed, corresponding to 64 responses, from which the total index (TI) was obtained from the division between DMA and ET. The content validity index (CVI = 0.78) showed a high degree of consensus among experts. In the validation process, the intraclass correlation coefficient (ICC) was used to assess intraclass and interobserver reliability, and a moderate level of agreement was found between subjects for the TA (ICC = 0.593) and ET (ICC = 0.602) and a moderate high level of concordance for DM (ICC = 0.804) and TI (ICC = 0.855). Regarding interobserver reliability, an excellent level of agreement was found for all variables: TA (ICC = 0.998), DM (ICC = 0.998), ET (ICC = 1.000), and TI (ICC = 1.000). For the relationship between intraobserver and interobserver variables, statistical significance was established as p < 0.01. Finally, the intraobserver ETM (5.40%) and interobserver ETM (0.42%) was low compared with the reference value (5.9%). The designed test meets the validity criteria since the variables show sufficient intraclass reliability (test-retest) and reliability among observers.



#6 Exploring the Effects of Tasks with Different Decision-Making Levels on Ball Control, Passing Performance, and External Load in Youth Football

Reference: Children (Basel). 2023 Jan 26;10(2):220. doi: 10.3390/children10020220.

Authors: Diogo Coutinho, Adam Leigh Kelly, Sara Santos, Pedro Figueiredo, David Pizarro, Bruno Travassos

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Summary: This study aimed to understand how the design of decision-making tasks affects youth football players' ball control, passing performance, and external load. A total of 16 male youth football players (age: 12.94 ± 0.25 years) competed in various tasks based on the following levels of decision-making: (i) low decision-making (Low DM), which consisted of a predefined ball control and passing sequence; (ii) moderate decision-making (Mod DM), which consisted of maintaining possession in a square with four players and two balls while maintaining the same position; and (iii) high decision-making (High DM), which consisted of a 3 vs. 3 + 2 neutral players ball possession game. The study design consisted of a pre-post design (a 6 min pre-test game, a 6 min intervention, and a 6 min post-test game). The players' ball control and passing performance were measured using the game performance evaluation tool and notational analysis, while GPS data were used to determine their physical performance. The pre-post test analysis revealed decrements in players' ability to identify more offensive players after the Mod DM task (W = 9.50, p = 0.016), while there was an increase in their ability to receive the ball towards the space following the High DM task (t = -2.40, p = 0.016). Analysis between groups showed lower values in most ball control variables for the Low DM task compared to the Mod DM task (ball control execution, p = 0.030; appropriateness, p = 0.031; motor space, p = 0.025), while there were also lower values in the distance covered while sprinting (p = 0.042). Overall, prescriptive tasks (Low DM) that are repetitive in nature may affect players' perceptual attunement, whereas static tasks (e.g., Mod DM) may limit their ability to locate players in more offensive positions. Moreover, game-based situations (High DM) seem to acutely enhance players' performance, possibly due to contextual dependency. Overall, coaches should carefully consider the type of practice structure when designing tasks that aim to improve players' technical skills in youth football.



#7 Task-Involving Motivational Climate and Enjoyment in Youth Male Football Athletes: The Mediation Role of Self-Determined Motivation

Reference: Int J Environ Res Public Health. 2023 Feb 9;20(4):3044. doi: 10.3390/ijerph20043044.

Authors: Nuno Amaro, Diogo Monteiro, Filipe Rodrigues, Rui Matos, Miguel Jacinto, Beatriz Cavaco, Sandro Jorge, Raúl Antunes

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Summary: This study aimed at examining the mediation role of self-determined motivation (identified and integrated regulation and intrinsic motivation) in the association between task-involving climate and enjoyment in youth male football athletes. A total of 109 youth males (M = 14.38; SD = 1.55) were recruited to participate in this study. The survey included sociodemographic data and validated instruments such as the Motivational Climate Sport Youth Scale, the Behavioral Regulation Sport Questionnaire, and the Sports Enjoyment Scale. The results showed that the task-involving climate was a positive and significant predictor of integrated regulation and intrinsic motivation. In addition, integrated regulation and intrinsic motivation were positive and significant predictors of enjoyment. The results of the mediation analysis revealed a partial mediation role of self-determined motivation in the relationship between task-involving climate and enjoyment. Significant indirect effects only occurred through intrinsic motivation. Providing higher levels of enjoyment in the sport context could be an excellent option for leisure activities for children and youth, as long as self-determined motivation and task-involving climates provided by the coaches are present.



#8 Effect of Supplementation with Black Chokeberry ( Aronia melanocarpa) Extract on Inflammatory Status and Selected Markers of Iron Metabolism in Young Football Players: A Randomized Double-Blind Trial

Reference: Nutrients. 2023 Feb 15;15(4):975. doi: 10.3390/nu15040975.

Authors: Błażej Stankiewicz, Mirosława Cieślicka, Jan Mieszkowski, Andrzej Kochanowicz, Bartłomiej Niespodziński, Andrzej Szwarc, Tomasz Waldziński, Joanna Reczkowicz, Elżbieta Piskorska, Miroslav Petr, Anna Skarpańska-Stejnborn, Jędrzej Antosiewicz

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Summary: The use of herbal medicinal products and supplements in amateur and professional sports has increased in the last decades. This is because most of these products and supplements contain bioactive compounds with a variety of biological properties that exert a physiological effect on the human body. The aim of this study was to analyze the effect of dietary supplementation with lyophilized black chokeberry extract on the levels of pro-inflammatory cytokines, hepcidin, and selected markers of iron metabolism in a group of young football players. This double-blind study included 22 male football players (mean = 19.96 ± 0.56), divided into two groups: supplemented and placebo. Before and after a 90-day period of training combined with supplementation (6 g of lyophilized black chokeberry extract), participants performed maximal multistage 20-m shuttle run tests at the beginning and at the end of the supplementation period, with blood sampled for analysis at different times before and after exercise. The levels of IL-6, IL-10, ferritin, myoglobin, hepcidin, 8-OHdG, albumin, and TAC were analyzed. The analysis of variance revealed a significant effect of 90-day supplementation with the lyophilized extract on changes in the IL-6 and IL-10 levels, and TAC induced by maximal aerobic effort. In conclusion, supplementation with lyophilized black chokeberry extract improves the performance and antioxidant status of serum in humans and induces protective changes in inflammatory markers.



#9 Effects of substitute allowance on match activity characteristics in Japanese professional football across 2019, 2020, and 2021 seasons

Reference: J Sports Sci. 2023 Feb 25;1-7. doi: 10.1080/02640414.2023.2182878. Online ahead of print.

Authors: Makoto Ayabe, Shunsuke Sunami, Hideaki Kumahara, Satoshi Ishizaki

Summary: This study aimed to examine the effects of substitute player allowance per match on running performance in Japanese professional football over three consecutive seasons with different numbers of maximum substitutes. Match running performance was obtained from all outfield players in the official matches of the 1st Division of the Japan Professional Football League over three seasons (2019/2020/2021; 22291 player files) by a 4th generation TRACAB® system which provided the total distance covered (TD) and the number of sprinting runs (SP; ≥24.0 km/h for≥1.0 s). The players were divided according to play time: full match (STA), replaced during match (REP), and substitutes during match (SUB). The number of SUBs increased significantly from 2019 to 2021 (p < 0.05). SUB had a significantly higher average speed than STA and REP. The analysis of covariance with the number of recovery days, ambient temperature, and relative humidity as covariates revealed that the TD and SP significantly differed based on the number of SUBs (p < 0.05). Stepwise regression analysis showed that the number of SUBs significantly contributed to the TD and SP. These results suggest that the new law, which increased the maximum SUB allowance from three to five, improved the match running performance in Japanese professional football.



#10 Football training as a non-pharmacological treatment of the global aging population-A topical review

Reference: Front Aging. 2023 Feb 9;4:1146058. doi: 10.3389/fragi.2023.1146058. eCollection 2023.

Authors: Magni Mohr, Ioannis G Fatouros, Muhammad Asghar, Pasqualina Buono, George P Nassis, Peter Krustrup

Summary: In the present topical mini-review, the beneficial impact of small-sided game football training for the increasing elderly global population is presented. As a multicomponent type of physical activity, football training executed on small pitched with 4-6 players in each team is targeting a myriad of physiological systems and causes positive adaptations of relevance for several non-communicable diseases, of which the incidence increases with advancing age. There is strong scientific evidence that this type of football training promotes cardiovascular, metabolic and musculo-skeletal health in elderly individuals. These positive adaptations can prevent cardiovascular disease, type 2 diabetes, sarcopenia and osteoporosis, and lower the risk of falls. Also, football training has been proven an efficient part of the treatment of several patient groups including men with prostate cancer and women after breast cancer. Finally, regular football training has an anti-inflammatory effect and may slow the biological aging. Overall, there is a growing body of evidence suggesting that recreational football training can promote health in the elderly.



#11 Daytime Napping Benefits Passing Performance and Scanning Activity in Elite Soccer Players

Reference: J Sports Sci Med. 2023 Mar 1;22(1):75-83. doi: 10.52082/jssm.2023.75. eCollection 2023 Mar.

Authors: Masaki Nishida, Shuta Okano, Atsushi Ichinose, Shutaro Suyama, Sumi Youn

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Summary: The present study explored the effect of a daytime napping opportunity on scanning activity, which is an essential component of successful soccer performance. Fourteen male elite collegiate soccer players performed the Trail Making Test (TMT), which was used to assess complex visual attention. In addition, a soccer passing test, modified with reference to the Loughborough Soccer Passing Test, was used to evaluate passing performance as well as scanning activity. A cross-over design was applied to examine nap and no-nap interventions. Participants (N = 14, mean age: 21.6 SD = 0.5 years, height: 1.73 ± 0.06 m, body mass: 67.1 ± 4.5 kg) were randomly allocated to a midday nap (40 minutes) or no-nap group. Subjective sleepiness was measured using the Karolinska Sleepiness Scale, and perceptive fatigue was evaluated by the visual analog scale. There were no significant differences in subjective measurements or TMT between the nap and no-nap groups. However, the performance time for the passing test and scanning activity was significantly shorter (p < 0.001) and scanning activity was significantly more frequent in the nap condition than in the no-nap condition (p < 0.00005). These results suggest that daytime napping is beneficial for soccer-related cognitive function, represented by visuospatial processing and decision-making, and particularly as a potential countermeasure to mental fatigue. Considering that inadequate sleep and residual fatigue are commonly observed in elite soccer, this finding may have practical implications for the preparation of players.



#12 Warm-up stretching exercises and physical performance of youth soccer players

Reference: Front Physiol. 2023 Feb 15;14:1127669. doi: 10.3389/fphys.2023.1127669. eCollection 2023.

Authors: Jordan Hernandez-Martinez, Rodrigo Ramirez-Campillo, Tiago Vera-Assaoka, María Castillo-Cerda, Bastian Carter-Truillier, Tomás Herrera-Valenzuela, Antonio López-Fuenzalida, Hadi Nobari, Pablo Valdés-Badilla

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Summary: This study aims to compare the effects of standard warm-up versus warm-up using stretching exercises on the physical performance of male youth soccer players. Eighty-five male soccer players (age: 10.3 ± 4.3 years; body mass index: 19.8 ± 4.3 kg/m2) were assessed for countermovement jump height (CMJ, cm), 10 m, 20 m and 30 m running sprint speed (s) and ball kicking speed (km/h) for the dominant and non-dominant leg under five (randomized) warm-up conditions. Using 72 h of recovery between conditions, the participants completed a control condition (CC) and four experimental conditions, including static stretching (SSC), dynamic stretching (DSC), ballistic stretching (BSC), and proprioceptive neuromuscular facilitation (PNFC) exercises. All warm-up conditions had a duration of 10 minutes. The main results indicate that no significant differences (p > 0.05) were found between warm-up conditions compared to CC in CMJ (CC = 28.1 ± 4.9; SSC = 28.4 ± 4.9; DSC = 30.9 ± 4.8; BSC = 30.9 ± 5.2; PNFC = 28.4 ± 5.0), 10 m sprint (CC = 2.42 ± 0.4; SSC = 2.50 ± 0.4; DSC = 2.30 ± 0.3; BSC = 2.27 ± 0.3; PNFC = 2.53 ± 0.4), 20 m sprint (CC = 5.42 ± 0.9; SSC = 5.59 ± 0.9; DSC = 5.37 ± 0.9; BSC = 5.40 ± 0.9; PNFC = 5.44 ± 0.9), 30 m sprint (CC = 8.05 ± 1.3; SSC = 8.27 ± 1.3; DSC = 8.01 ± 1.3; BSC = 8.00 ± 1.3; PNFC = 8.12 ± 1.3), ball kicking speed for dominant (CC = 56.2 ± 4.9; SSC = 55.3 ± 5.2; DSC = 56.9 ± 5.8; BSC = 57.3 ± 5.8; PNFC = 55.7 ± 5.2) and non-dominant leg (CC = 52.8 ± 3.4; SSC = 51.8 ± 4.6; DSC = 53.5 ± 5.4; BSC = 53.6 ± 4.9; PNFC = 52.5 ± 4.0). In conclusion, compared to standard warm-up, stretching-based warm-up exerts no effect on male youth soccer players jump height, sprint speed and ball kicking speed.



#13 Reduced Match Exposure in the Previous 2 Matches Accounts for Hamstring Muscle Injury Incidence in Professional Football Players

Reference: Sports Health. 2023 Mar 10;19417381231158117. doi: 10.1177/19417381231158117.

Authors: Víctor Moreno-Pérez, Juan Del Coso, Roberto López-Del Campo, Ricardo Resta, José Romero-Sangüesa, Javier Courel-Ibáñez, Alberto Méndez-Villanueva

Summary: Hamstring strain injuries are one of the most prevalent injuries in football (soccer). We examined the influence of accumulated match-play exposure on the occurrence of hamstring strain injury in professional football from 2 teams (Spanish 1st Division, LaLiga) over 3 seasons, and determined specific cut-off points as indicators of injury risk. We hypothesized that overloaded players would be more likely to sustain a hamstring injury. Playing time, total running distance, and high-speed running (>24 km/h) distance during official matches of players that sustained a hamstring injury were compared with uninjured, paired controls. Cumulative playing time and running performance of 4 matches before the injury was computed. Relative risk (RR) of injury occurrence was estimated by generalized estimating equations. Diagnostic accuracy was determined by receiver operating characteristics and the area under the curve. Thirty-seven hamstring strain injuries occurred, representing 23 ± 18 absence days per injury. Thirty-seven controls (uninjured players) were used as comparators. Low match-play exposures during 1 and 2 matches before injury were likely to explain injury occurrence (RR: 14-53%; P < 0.01). Metrics from the match before the hamstring muscle strain demonstrated the best accuracy to predict injury occurrence: high-speed running distance ≤328 m (sensitivity, 64%; specificity, 84%), playing time ≤64 min (sensitivity, 36%; specificity, 97%), and running distance ≤5.8 km (sensitivity, 39%; specificity, 97%). Relatively reduced competitive exposure in the previous 2 matches was associated with higher hamstring injury risk in professional football players. Screening simple metrics such as the accumulated match exposure during official matches and considering specific cut-off points for some running variables may be good indicators of injury risk and may assist in better individual injury management in professional soccer players.



#14 Cold water immersion after a soccer match: Does the placebo effect occur?

Reference: Front Physiol. 2023 Feb 21;14:1062398. doi: 10.3389/fphys.2023.1062398. eCollection 2023.

Authors: Nidhal Nasser, Houssem Zorgati, Hamdi Chtourou, Alexandre Guimard

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Summary: Although cold water immersion (CWI) is one of the most widely used post-exercise strategies to accelerate recovery processes, the benefits of CWI may be associated with placebo effects. This study aimed to compare the effects of CWI and placebo interventions on time course of recovery after the Loughborough Intermittent Shuttle Test (LIST). In a randomized, counterbalanced, crossover study, twelve semi-professional soccer players (age 21.1 ± 2.2 years, body mass 72.4 ± 5.9 kg, height 174.9 ± 4.6 cm, ˙V�˙ O2max 56.1 ± 2.3 mL/min/kg) completed the LIST followed by CWI (15 min at 11°C), placebo (recovery Pla beverage), and passive recovery (Rest) over three different weeks. Creatine kinase (CK), C-reactive protein (CRP), uric acid (UA), delayed onset muscle soreness (DOMS), squat jump (SJ), countermovement jump (CMJ), 10-m sprint (10 mS), 20-m sprint (20 mS) and repeated sprint ability (RSA) were assessed at baseline and 24 and 48 h after the LIST. Compared to baseline, CK concentration was higher at 24 h in all conditions (p < 0.01), while CRP was higher at 24 h only in CWI and Rest conditions (p < 0.01). UA was higher for Rest condition at 24 and 48 h compared to Pla and CWI conditions (p < 0.001). DOMS score was higher for Rest condition at 24 h compared to CWI and Pla conditions (p = 0.001), and only to Pla condition at 48 h (p = 0.017). SJ and CMJ performances decreased significantly after the LIST in Rest condition (24 h: -7.24%, p = 0.001 and -5.45%, p = 0.003 respectively; 48 h: -9.19%, p < 0.001 and -5.70% p = 0.002 respectively) but not in CWI and Pla conditions. 10 mS and RSA performance were lower for Pla at 24 h compared to CWI and Rest conditions (p < 0.05), while no significant change was observed for 20 mS time. These data suggests that CWI and Pla intervention were more effective than the Rest conditions in recovery kinetics of muscle damage markers and physical performance. Furthermore, the effectiveness of CWI would be explained, at least in part, by the placebo effect.



#15 Return to Play and Pattern of Injury After ACL Rupture in a Consecutive Series of Elite UEFA Soccer Players

Reference: Orthop J Sports Med. 2023 Mar 3;11(3):23259671231153629. doi: 10.1177/23259671231153629. eCollection 2023 Mar.

Authors: Luca Farinelli, Elisabeth Abermann, Amit Meena, Peter Ueblacker, Jochen Hahne, Christian Fink

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Summary: Anterior cruciate ligament rupture represents a career-threatening injury for professional soccer players. The aim was to analyze the pattern of injury, return to play (RTP), and performance of a consecutive series of elite professional soccer players after anterior cruciate ligament reconstruction (ACLR). We evaluated the medical records of 40 consecutive elite soccer players who underwent ACLR by a single surgeon between September 2018 and May 2022. Patient age, height, weight, body mass index, position, injury history, affected side, RTP time, minutes played per season (MPS), and MPS as a percentage of playable minutes before and after ACLR were retrieved from medical records and from publicly available media-based platforms. Included were 27 male patients (mean ± SD age at surgery, 23.2 ± 4.3 years; range, 18-34 years). The injury occurred during matches in 24 players (88.9%), with a noncontact mechanism in 22 (91.7%). Meniscal pathology was found in 21 patients (77.8%). Lateral meniscectomy and meniscal repair were performed in 2 (7.4%) and 14 (51.9%) patients, respectively, and medial meniscectomy and meniscal repair were performed in 3 (11.1%) and 13 (48.1%) patients, respectively. A total of 17 players (63.0%) underwent ACLR with bone-patellar tendon-bone autograft and 10 (37.0%) with soft tissue quadriceps tendon. Lateral extra-articular tenodesis was added in 5 patients (18.5%). The overall RTP rate was 92.6% (25 of 27). Two athletes moved to a lower league after surgery. The mean MPS% during the last preinjury season was 56.69% ± 21.71%; this decreased significantly to 29.18% ± 20.6% (P < .001) in the first postoperative season and then increased to 57.76% ± 22.89% and 55.89% ± 25.8% in the second and third postoperative seasons. Two (7.4%) reruptures and 2 (7.4%) failed meniscal repairs were reported. ACLR in elite UEFA soccer players was associated with a 92.6% rate of RTP and 7.4% rate of reinjury within 6 months after primary surgery. Moreover, 7.4% of soccer players moved to a lower league during the first season after surgery. Age, graft selection, concomitant treatments, and lateral extra-articular tenodesis were not significantly associated with prolonged RTP.



#16 Ankle dorsiflexion range of motion and landing postures during a soccer-specific task

Reference: PLoS One. 2023 Mar 16;18(3):e0283150. doi: 10.1371/journal.pone.0283150. eCollection 2023.

Authors: Hadi Akbari, Yohei Shimokochi, Bahram Sheikhi

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Summary: Ankle dorsiflexion range of motion (DF-ROM) has been shown to be associated with poor landing posture. However, previously used tasks have been controlled, and it is unclear whether clinical measurements of the ankle DF-ROM, are associated with landing positions during sport-specific task. This study sought to determine the relationship between ankle DF-ROM and landing positions. Thirty male soccer players participated in this study. The ankle DF-ROM was measured by the weight bearing lunge test in degrees using a cell phone app (TiltMeter). Landing patterns were assessed during a soccer-specific task using landing error scoring system items using Kinovea software. Simple correlations were used to evaluate the relationships between ankle DF-ROM and landing error scores. Significant correlations were found between ankle DF-ROM and landing errors (r = -0.450, P = 0.006). A decreased ankle DF-ROM was associated with greater landing errors in a soccer specific situation. These results suggest that ankle DF-ROM may serve a useful clinical measure for identifying poor landing posture in the real-world environment. Therefore, assessment of ankle DF-ROM could be included in the screening process, which could help identify the cause of the faulty motion.



#17 Starters and non-starters soccer players in competition: is physical performance increased by the substitutions?

Reference: BMC Sports Sci Med Rehabil. 2023 Mar 16;15(1):33. doi: 10.1186/s13102-023-00641-3.

Authors: Alfonso Castillo-Rodríguez, José Luis González-Téllez, Antonio Figueiredo, José Luis Chinchilla-Minguet, Wanesa Onetti-Onetti

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Summary: Non-starters soccer players have a great role within the team, being indispensable to reduce fatigue, as well as to maintain and increase the team's performance during the match. This study aimed to analyze the physical performance of the starter and non-starters players during competitive soccer matches. Twenty-two soccer players participated in this study, divided into two groups according to the role in the match (starters or non-starters). WIMU Global Positioning System devices were used in order to record physical performance metrics. Independent samples t-test and one-way ANOVA tests were performed to compare starters and non-starters, and the playing position, respectively, and two-way ANOVA test was perform with these factors too. There were no differences in the main physical performance metrics between starters and non-starters players during competition, although there were differences in physical performance metrics according to the playing position. Midfielders performed highest distance per minute, player load, and distance covered between 12 and 21 km·h- 1 (p < .05). Finally, distance covered at speeds greater than 24 km·h- 1 was predicted by the playing role (starters and non-starters) and playing position factors with 88% of explained variance (ηp2 = 0.772). The main findings of this study showed that non-starter players had a similar physical performance during competitive matches as the starter players for whom they are substituted. In addition, the playing position determined different physical performance, contributing in this manuscript that behavior and decision-making of the players could be affected by their position in the field. More studies are needed on non-starter player performance and contextual factors that could influence the physical responses of these players.



#18 Trends in Relative Age Effects of Top-Level Female Soccer Players: A Japanese Study

Reference: Percept Mot Skills. 2023 Mar 15;315125231162745. doi: 10.1177/00315125231162745.

Authors: Shigeki Matsuda, Hiroaki Ishigaki

Summary: We investigated recent trends in relative age effect (RAE) findings of top-level female soccer players in Japan, using data from the 2016 to 2020 seasons. We conducted two main analyses: (a) An examination of RAE for all registered players in the Japan Women's Soccer League (Nadeshiko League) from 2016 to 2020; and (b) an examination of RAE of newly registered players in the league from 2017 to 2020. In the first analysis, we found a significant difference between the number of players born in Q1 (April-June) versus Q4 (January-March), with the number of players born in Q1 greater and with the ratio between these groups ranging from 1.5 to 1.7. In the second analysis, we found a significant relationship between Q1 and Q4 for the 2017 season alone. However, the Q1/Q4 ratio ranged from 1.4 to 1.9, and the semester ratio of S1 (Q1 + Q2))/S2 (Q3 + Q4) ranged from 1.2 to 1.3, suggesting a birth month bias. Thus, there was a RAE in female soccer players playing recently in Japan's top-level leagues; and the size of the effect did not change significantly across recent seasons.



#19 Sex difference in soccer instep kicking

Reference: J Sports Sci. 2022 Oct;40(20):2217-2224. doi: 10.1080/02640414.2022.2139881.

Authors: Tsuyoshi Iitake, Maya Hioki, Hitoshi Takahashi, Hiroyuki Nunome

Summary: We aimed to clarify the differences in soccer instep kicking dynamics between sex groups. The instep kicking of seven female (height: 160.3 ± 6.1 cm; mass: 54.3 ± 5.2 kg) and seven male (height: 173.0 ± 5.9 cm; mass: 70.0 ± 9.0 kg) players were recorded by a motion capture system (500 Hz). Joint moments of the kicking leg were computed and normalized by the body mass and height. Statistical parametric mapping was used to compare the entire kicking motion between the two groups. Significantly slower resultant ball velocity seen in female players was most likely explained by their significantly slower run-up velocity, shorter leg length and lower foot-ball velocity ratio. Female players exhibited significantly smaller knee joint moment in the latter part (80-86%) of kicking. Also, significantly smaller positive work done by knee extension moment and the ratio of work (knee extension/hip flexion) were found in female players. These results suggested that the suppressed knee extension moment action was identified as a key kinetic characteristic in the instep kicking of female players, and to compensate for this action, they more rely on the work due to hip flexion moment to execute the instep kicking.



#20 Effects of plyometric vs. strength training on strength, sprint, and functional performance in soccer players: a randomized controlled trial

Reference: Sci Rep. 2023 Mar 14;13(1):4256. doi: 10.1038/s41598-023-31375-4.

Authors: Shahnaz Hasan

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Summary: Plyometric training (PT) has been shown to have numerous benefits and few harmful effects. This study aimed to compare the effects of PT vs. strength training on muscle strength, sprint, and lower limb functional performance in soccer players. Ninety participants (mean age 22.5 years) were equally and randomly divided into three groups: a plyometric training group (PTG; n = 30), a strength training group (STG; n = 30), and a control group (CG; n = 30). In PTG: bounding, hurdling, and drop jumping exercises were performed. In STG: isometric exercises of knee extension (at 60º knee flexion), quadriceps (in supine), hip adductors (in crook lying), and straight leg raise were performed. In CG: no specific training was given. All interventions were performed for eight weeks. Isometric strength (IS), sprint (ST), and single-leg triple hop (SLTH) tests were outcome measures. The wilcoxon signed ranks test was used for with-in-group analysis, and Kruskal Wallis and Mann-Whitney u tests were used for between-group analyses. In PTG: in comparison to a baseline measurement, IS increased by 8.83% (p < 0.05), ST decreased by 20.14% (p < 0.05), and SLTH increased by 7.78% (p < 0.05). In STG: IS increased by 15.76% (p < 0.05), ST decreased by 30.26% (p < 0.05), and SLTH increased by 12.41% (p < 0.05). In CG: IS increased by 5.72% (p < 0.05), ST decreased by 15.54% (p < 0.05), and SLTH increased by 4.41% (p < 0.05). The greatest improvements were observed in STG, followed by PTG and CG. Strength training was found to be more effective than PT in improving muscle strength, sprint, and lower limb functional performance in male soccer players.



#21 The association of dietary insulin load and dietary insulin index with body composition among professional soccer players and referees

Reference: BMC Sports Sci Med Rehabil. 2023 Mar 13;15(1):31. doi: 10.1186/s13102-023-00635-1.

Authors: Mohammad Beba, Mohammad Gholizadeh, Mohammad Sharifi, Tohid Seifbarghi, Kurosh Djafarian

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Summary: There has been limited research undertaken about the association of dietary insulin load (DIL) and dietary insulin index (DII) with body composition in non-athletic adults, however, to the best of our knowledge No previous study has investigated such an association in an athletic population. The aim of this study was to explore the association of DII and DIL with body compositions in male and female soccer players and referees. The cross-sectional study was conducted on 199 professional male and female soccer players and referees. A 147-item semi-quantitative food frequency questionnaire (FFQ) was adopted to congregate the participants' dietary data. Body composition was measured using InBody to gain a detailed understanding of fat mass, percent body fat (PBF), lean mass, percent muscle mass (PMM), and bone mineral content (BMC). Waist circumference (WC), hip circumference (HC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) were obtained from all participants. Other body composition parameters include a body shape index (ABSI), abdominal volume index (AVI), body adiposity index (BAI), body roundness index (BRI), conicity index (CI), weight-adjusted waist index (WWI) and waist-to-hip-to-height ratio (WHHR) were calculated using a particular defined formula. Results of multiple linear regression revealed that there is a significant association between DIL and BMI (P = 0.04) in < 18 male soccer players, CI (P = 0.04) and WWI (P = 0.03) in ≥ 18 female soccer players, PBF (P = 0.02), PMM (P = 0.01) and WWI (P = 0.01) in ≥ 18 female soccer players. Nevertheless, no significant associations between DIL and body composition parameters were found in the referees. Additionally, there is a significant association between DII and BMC (P = 0.02) in male soccer referees, however, no significant associations were found in young soccer players and female athletes. This study demonstrates that DIL is positively associated with BMI, CI, and WWI in male soccer players and PBF, and WWI in female soccer players. Although, there was an observed negative association between DIL and PMM in females. In addition, a significant negative association between DII and BMC was observed in male soccer players.






Physical Fitness Variations between Those Playing More and Those Playing Less Time in the Matches in Youth Soccer Players

The purpose of this study was (i) to compare two groups (players with more vs. less match play time) regarding body composition, vertical and horizontal jumping performance, and aerobic capacity; and (ii) to test the relationships between physical fitness and play time.





Physical Impact of a Typical Training Session with Different Volumes on the Day Preceding a Match in Academy Soccer Players

The present study aimed to determine the physical impact of different training durations on MD-1 on the subsequent matchday performance (MD).





Latest research in football - week 8 - 2023

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 COVID-19 Pandemic on Injury Incidence in Japanese Male Professional Soccer Players

Reference: Orthop J Sports Med. 2023 Feb 24;11(2):23259671221149373. doi: 10.1177/23259671221149373. eCollection 2023 Feb.

Authors: Ryo Matsunaga, Masashi Nagao, Ryuichiro Akagi, Atsushi Fukai, Takashi Sando, Hiroshi Ikeda, Shuji Taketomi

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Summary: The outbreak of the 2019 novel coronavirus disease (COVID-19) led to an enforced quarantine period and limited training and match activities for athletes. To report the influence of the COVID-19 pandemic on the occurrence of injury in Japanese male professional soccer players. In total, 21 clubs in the 2019 season and 28 clubs in the 2020 season from the Japan Professional Football League were prospectively followed, and 16 clubs in 2019 and 24 clubs in 2020 were analyzed in this study. Individual training, match exposure, and time-loss injuries were recorded using an electronic data capture system. The influence of COVID-19-related suspension during the 2020 season was retrospectively investigated via comparisons with the 2019 season. Total activity time included 114,001 hours in training and 16,339 hours in matches in 2019 and 170,798 hours in training and 25,411 hours in matches in 2020. The mean training interruption period caused by COVID-19 in 2020 was 39.9 days (range, 3-65 days), and the mean game-interruption period was 70.1 days (range, 58-79 days). The total number of injuries was 1495 in 2019 and 1701 in 2020. The overall injury incidence per 1000 hours of exposure was 5.7 in 2019 and 5.8 in 2020. The overall injury burden per 1000 hours of exposure was 155.5 days in 2019 and 130.2 days in 2020. The muscle injury incidence was highest in May 2020, immediately after the suspension period. The overall injury incidence did not differ between 2019 and 2020. However, muscle injury incidence notably increased in the 2 months after the COVID-19 pandemic suspension period.



#2 High-speed running and sprinting in professional adult soccer: Current thresholds definition, match demands and training strategies. A systematic review

Reference: Front Sports Act Living. 2023 Feb 13;5:1116293. doi: 10.3389/fspor.2023.1116293. eCollection 2023.

Authors: Antonio Gualtieri, Ermanno Rampinini, Antonio Dello Iacono, Marco Beato

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Summary: The aims of this systematic review were (1) to summarize the evidence on absolute velocity thresholds used to classify high-speed running and sprinting, (2) to examine the existing evidence about the individualized thresholds approach, (3) to describe high-speed and sprint running distance match demands, and (4) to provide training strategies for eliciting HSR and sprinting during training sessions in professional adult soccer. This systematic review was conducted following the PRISMA 2020 guidelines. After the authors' screening, 30 studies were included in this review. This review found that, to date, there is no consensus on the absolute thresholds defining high-speed and sprint running in adult soccer players. Until international standards are defined, it is reasonable to set absolute thresholds considering the range of values found in the literature collected in this review. Relative velocity thresholds could be considered for specific training sessions whose goal is to reach near maximal velocity exposure. During official matches, high-speed and sprint running distances ranged from 911 to 1,063 m and 223-307 m, respectively, in professional female soccer players, while ranges from 618 to 1,001 m and 153-295 m, respectively, in professional male soccer players. During training, game-based drills designed in formats using relative areas per player greater than 225 m2 and 300 m2 appear to be adequate for achieving high-speed running and sprinting exposure, respectively, for male players. The combination of game-based, running exercises and soccer circuit-based drills is advisable to ensure adequate high-speed and sprint running exposure both at a team and individual level.



#3 Football (Soccer) as a Probable Cause of Long-Term Neurological Impairment and Neurodegeneration: A Narrative Review of the Debate

Reference: Cureus. 2023 Jan 27;15(1):e34279. doi: 10.7759/cureus.34279. eCollection 2023 Jan.

Authors: Daniele Ramsay, Alice Miller, Bibire Baykeens, Hamaas Hassan, Steve Gentleman

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Summary: Football (soccer) is the most widely played sport across the globe. Due to some recent high-profile cases and epidemiological studies suggesting football can lead to neurodegeneration, scientific and public interest has been piqued. This has resulted in research into whether an association between football participation and neurodegeneration or neurological impairment is present. It has been theorised that a combination of repeated sub-concussive and concussive injuries, due to ball-heading and head collisions, may lead to neurodegeneration. However, evidence remains conflicting. Due to the popularity of the sport, and the serious conditions it has been linked to, it is important to determine whether repeated head impacts during football participation can play a causative role in neurodegenerative disease. To answer this question, a review of the current literature was carried out. Epidemiological evidence showed a higher incidence of amyotrophic lateral sclerosis amongst amateur and professional footballers and that footballers in positions that involve less contact and heading, e.g., goalkeepers lead significantly longer lives. Additionally, imaging studies reach a similar conclusion, reporting changes in brain structure, blood flow, and inflammatory markers in footballers when compared to controls. However, studies looking at an association between heading frequency and cognition show a lack of consensus on whether a higher heading exposure results in reduced cognition. Similarly, in neuropathological studies, signs of chronic traumatic encephalopathy (CTE) have been found in some former players, with contrasting studies suggesting low levels of CTE-type pathology are found in the general population, regardless of exposure to head trauma. The majority of studies suggest a link between football and neurodegenerative disease. However, the high prevalence of retrospective cohort and cross-sectional studies, often plagued by recall bias, undermine the conclusions drawn. Therefore, until larger prospective cohort studies are conducted, concrete conclusions cannot be made. However, caution can be exercised to limit head impacts.



#4 Dynamic valgus knee revealed with single leg jump tests in soccer players

Reference: J Sports Med Phys Fitness. 2023 Mar;63(3):461-470. doi: 10.23736/S0022-4707.22.14442-7.

Authors: Ádám Uhlár, Mira Ambrus, Zsombor Lacza

Summary: Dynamic valgus knee occurs in sports that involve jumps and landing such as soccer and pose an increased risk for anterior cruciate ligament injury. Visual estimation is biased by the athlete's body type, the experience of the evaluator and the movement phase at which the valgus is assessed - thus the result is highly variable. The aim of our study was to accurately assess dynamic knee positions during single and double leg tests through a video-based movement analysis system. Young soccer players (U15, N.=22) performed single leg squat, single leg jump, and double leg jump tests while the knee medio-lateral movement was monitored with a Kinect Azure camera. Jumping and landing phases of the movement were determined within the continuous recording of the knee medio-lateral position over the ankle and the hip vertical position. Kinect measurements were validated by Optojump (Microgate, Bolzano, Italy). Soccer players retained their predominantly varus knee positions in all phases of double-leg jumps, which was far less prominent in single leg tests. Interestingly, a marked dynamic valgus was observed in athletes who participated in traditional strengthening exercises, while this valgus shift was mostly prevented in those who participated in antivalgus training regimes. All these differences were only revealed during single leg tests, while the double leg jump tests masked all valgus tendencies. We propose to use single-leg tests and movement analysis systems for evaluating dynamic valgus knee in athletes. These methods can reveal valgus tendencies even in soccer players who have a characteristic varus knee while standing.



#5 Mortality of Spanish soccer referees and coaches: a retrospective cohort study

Reference: Sci Med Footb. 2023 Mar 2;1-7. doi: 10.1080/24733938.2023.2184485. Online ahead of print.

Authors: José Carlos Diz, Iván Rodríguez, Santiago Iglesias-Sueiro, Eva Diz Ferreira, Miguel A Sanchez-Lastra, Carlos Ayán

Summary: There is evidence that elite soccer players live longer than general population, but there is no information on soccer coaches and referees. We aimed to analyze the longevity of both professionals, comparing them with soccer players and with general population. In this retrospective cohort study, a total of 328 male Spanish soccer coaches, 287 referees, and 1230 soccer players, all born before 1950, were divided in two cohorts, matched 2:1 with coaches and referees. We compared the survival of the cohorts with the Kaplan-Meier estimator and significance with the log-rank test. We calculated hazard ratios of death for coaches and referees compared with male Spanish general population of the same period. Differences in survival among cohorts were found, but they did not reach statistical significance. The estimated median survival time was 80.1 years (95% CI 77.7-82.4) for referees, 78 years (95% CI 76.6-79.3) for coaches, 78.8 years (95% CI 77.6-80) for referees matched with players, and 76.6 years (95% CI 75.3-77.9) for coaches matched with players. Both coaches and referees had lower mortality than general population, but this advantage disappeared after 80 years of age. We found no differences in longevity among Spanish elite soccer referees, coaches and players born before 1950. Both coaches and referees had lower mortality than general population, but this advantage disappeared after 80 years of age.



#6 Speed-Related Abilities Are Similarly Improved After Sled Training Under Different Magnitudes of Velocity Loss in Highly Trained Soccer Players

Reference: Int J Sports Physiol Perform. 2023 Jan 1;1-8. doi: 10.1123/ijspp.2022-0354. Online ahead of print.

Authors: Rafael Grazioli, Irineu Loturco, Filipe Veeck, Igor Setuain, Laura A Zandavalli, Martinho Inácio, Ronei S Pinto, Eduardo L Cadore

Summary: We examined the effects of two 8-week resisted-sprint training programs under different magnitudes of velocity loss (VL) on the speed-related performance of highly trained soccer players. Twenty-one soccer players (age: 25.9 [5.4] y) were randomly assigned to 1 of 2 groups: (1) the "moderate-load group," players who trained with sled loads that induced 15%VL relative to unloaded sprint velocity (n = 11); and (2) the "heavy-load group," players who trained with sled loads that induced 40% VL relative to unloaded sprint velocity (n = 10). Linear sprint (10 m), curve sprint, change-of-direction speed, resisted-sprint performance at 15% VL and 40% VL, and vertical jumping ability were tested pretraining and posttraining. A 2-way repeated-measures analysis of variance was used to test for differences between groups. In addition, percentage changes were calculated for speed-related abilities and compared with their respective coefficients of variation to determine whether individual changes in performance were greater than the test variance (ie, "true change"). A main effect of time was detected for 10-m sprint, curve sprint, change-of-direction speed, and 15% VL and 40% VL resisted-sprint times, with significant decreases in sprint times (P = .003, P = .004, P = .05, P = .036, and P = .019, respectively). Jump variables did not change significantly over time. There were no group-by-time interactions for any tested variable (P > .05), but the "true change" analysis revealed meaningful individual changes in both groups. Both moderate- and heavy-sled loading conditions may optimize the development of speed-related abilities in highly trained soccer players. Nevertheless, resisted-sprint training responses may differ meaningfully when assessed on an individual basis.



#7 Relationship between body size and skeletal age with muscle damage in young soccer players

Reference: Int J Sports Med. 2023 Mar 2. doi: 10.1055/a-2046-2747. Online ahead of print.

Authors: Luiz Fernando Ramos-Silva, Julio Cesar da Costa, Paulo Henrique Borges, Felipe A Moura, Rafael Deminice, Donizete Cícero Xavier de Oliveira, Raul Osiecki, Enio Ronque

Summary: This study verified the relationship between body size and skeletal age (SA) with the behavior of blood markers of muscle damage and delayed onset muscle soreness (DOMS) after a soccer match in the U-13 and U-15 categories. The sample consisted of 28 soccer players in the U-13 and 16 in the U-15 categories. Creatine kinase (CK), lactate dehydrogenase (LDH), and DOMS were evaluated up to 72h after the match. Muscle damage was elevated at 0h in U-13, and from 0h to 24h in U-15. DOMS increased from 0h to 72h in U-13 and from 0h to 48h in U-15. Significant associations of SA and fat-free mass (FFM) with muscle damage markers and DOMS were observed only in U-13, specifically at time 0h, when SA explained 56% of CK and 48% of DOMS and FFM explained 48% of DOMS. Concluded that in the U-13 category, higher SA is significantly associated with muscle damage markers, and increase in FFM is associated with muscle damage markers and DOMS. Furthermore, U-13 players need 24h to recover pre-match muscle damage markers and more than 72h to recover DOMS. In contrast, the U-15 category needs 48h to recover muscle damage markers and 72h to recover DOMS.



#8 Effects of short bout small-sided game training on acid-based balance markers in youth male soccer players

Reference: Sci Rep. 2023 Mar 2;13(1):3510. doi: 10.1038/s41598-023-30646-4.

Authors: Jakub Kryściak, Tomasz Podgórski, Paweł Chmura, Marek Konefał, Jan Chmura, Marius Brazaitis, Toni Modric, Marcin Andrzejewski

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Summary: This study aimed to compare the effects of 1 × 1 small-sided games (SSGs) with different bout durations on external (ETL) and internal training loads (ITL) in youth soccer players. Twenty U18 players were divided into two groups performing six 1 × 1 SSGs with 30 and 45 s bout durations on a playing field of 10 by 15 m. ITL indices, including the percentage of maximum heart rate (HR), blood lactate (BLa) level, pH, bicarbonate (HCO3-) level, and base excess (BE) level, were measured at rest, after each SSG bout, and 15 and 30 min after the entire exercise protocol. ETL (Global Positioning System metrics) was recorded during all six SSG bouts. The analysis showed that the 45 s SSGs had a greater volume (large effect) but a lower training intensity (small to large effect) than the 30 s SSGs. A significant time effect (p < 0.05) was observed in all ITL indices and a significant group effect (F1, 18 = 8.84, p = 0.0082, ƞ2 = 0.33) in the HCO3- level only. Finally, the changes in the HR and HCO3- level were smaller in the 45 s SSGs than in the 30 s SSGs. In conclusion, 30-s games, characterized by a higher intensity of training effort, are more physiologically demanding than 45-s games. Secondly during short-bout SSG training the HR and BLa level have limited diagnostic value for ITL. Extending ITL monitoring using other indicators, such as the HCO3- and BE levels, appears reasonable.



#9 Female athlete triad cross-sectional study of soccer players by level of competition

Reference: J Phys Ther Sci. 2023 Mar;35(3):170-174. doi: 10.1589/jpts.35.170. Epub 2023 Mar 1.

Authors: Chiaki Matsumoto, Masahiro Ishizaka, Akira Kubo, Masafumi Itokazu

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Summary: The aim was to determine the actual status of the Female Athlete Triad (low energy availability, menstrual dysfunction, and bone mineral density loss) in soccer players. The survey was conducted between February 1 and March 1, 2022. It included 115 females between the ages of 12 and 28 registered with the Japan Football Association, from teams at different levels. Players in the top league did not differ in height and weight but were older and had a better understanding of caloric intake. There were no differences in amenorrhea or history of bone fractures based on league. Of the female soccer players in the four different levels of competition, only the players in the top league had a better understanding of available energy and took preventive measures against the Female Athlete Triad.



#10 The Social Media Presence of Professional Sports Team Physicians Is High Among Major League Soccer, Major League Lacrosse, Major League Rugby, Winter Olympics, and Women's National Basketball Association, But Highest Among MLS Team Physicians

Reference: Arthrosc Sports Med Rehabil. 2022 Dec 20;5(1):e59-e65. doi: 10.1016/j.asmr.2022.10.008. eCollection 2023 Feb.

Authors: Sayyida S Hasan, Hashim Shaikh, Keshin Visahan, Sergio Navarro, Irvin Sulapas, Theodore Shybut

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Summary: The purpose was to quantify the social media utilization of professional sports team physicians on popular platforms and analyze differences between physician users and physician non-users for smaller major professional sports: Major League Soccer (MLS), Major League Lacrosse (MLL), Major League Rugby (MLR), Winter Olympics (WO) and Women's National Basketball Association (WNBA). Physicians for the MLS, MLL, MLR, WO, and WNBA were identified and characterized based on training background, practice setting, years of experience, and geographic location. Social media presence on Facebook, Twitter, LinkedIn, Instagram, and ResearchGate were determined. Differences between social media users and non-users were analyzed via chi-squared tests for nonparametric variables. Secondary analysis consisted of univariate logistic regression to identify associated factors. 86 team physicians were identified. 73.3% of physicians had at least one social media profile. 80.2% of physicians were orthopedic surgeons. Specifically, 22.1% had a professional Facebook page, 24.4% had a professional Twitter page, 58.1% had a LinkedIn profile, 25.6% a ResearchGate profile, and 9.3% an Instagram account. All physicians with a social media presence were fellowship-trained. Seventy-three percent of team physicians in the MLS, MLL, MLR, WO, or WNBA have social media presence, with over half using LinkedIn. Fellowship-trained physicians were significantly more likely to use social media, and 100% of physicians with social media presence were fellowship trained. MLS and WO team physicians were significantly more likely to use LinkedIn (P = .02). MLS team physicians were significantly more likely to use social media overall (P = .004). No other metric significantly impacted social media presence. The influence of social media is vast. It is important to explore the extent that sports team physicians utilize social media and how this use may influence patient care.



#11 Comparison of soccer instep kicking kinematics with and without elastic taping

Reference: Sports Biomech. 2023 Mar 3;1-12. doi: 10.1080/14763141.2023.2184419. Online ahead of print.

Authors: Nahoko Sato, Hiroyuki Nunome, Yuichi Mizukami

Summary: The present study aimed to determine the effect of elastic taping on soccer instep kicking kinematics. Fifteen male university soccer players performed maximal instep kicking with and without Y-shaped elastic taping on the skin surface of the rectus femoris muscle. Their kicking motions were captured at 500 Hz using a motion capture system. The thickness of the rectus femoris muscle was measured using an ultrasound scanner prior to the kicking session. The thickness of the rectus femoris muscle and kicking leg kinematics in both the conditions were compared. The thickness of the rectus femoris muscle increased significantly after elastic tape application. In conjunction with this change, kinematic variables of the kicking leg, such as peak hip flexion angular velocity and knee and foot linear velocities significantly increased. However, there was no change in the knee extension angular and hip linear velocities. The elastic tape application caused deformation of the rectus femoris muscle and improvement of the instep kicking performance. The study findings provide a new insight on the effect of elastic taping on dynamic sports performance, such as in soccer instep kicking.



#12 Changes in Estimated Body Composition and Physical Fitness of Adolescent Boys after One Year of Soccer Training

Reference: Children (Basel). 2023 Feb 16;10(2):391. doi: 10.3390/children10020391.

Authors: Cíntia França, Diogo V Martinho, Élvio Rúbio Gouveia, Francisco Martins, Adilson Marques, Tiago Ribeiro, Marcelo de Maio Nascimento, Helder Lopes, Ana Rodrigues, Andreas Ihle

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Summary: Sports participation is one of the most popular forms of physical activity among youngsters. This study aimed to examine the changes in the estimated body composition, strength, and flexibility of adolescent boys after 12 months of soccer training compared with those of age-matched controls with non-sports participation. We assessed 137 boys (62 soccer players and 75 controls) at baseline (TM1) and 12 months later (TM2). The differences in estimated body composition, strength, and flexibility were investigated using a repeated measure analysis of variance. The analysis revealed a significant main effect of soccer training on fat mass (F = 73.503, p ≤ 0.01, η2 = 0.59) and fat-free mass (F = 39.123, p ≤ 0.01, η2 = 0.48). Over time, the soccer group decreased their fat mass and increased their fat-free mass, while the opposite results were observed for the controls. Among physical fitness tests, a substantial effect of soccer training was evidenced for the sit-up performance (F = 16.224, p ≤ 0.01, η2 = 0.32). Regarding the time factor, significant effects were noted for height and handgrip strength. No significant differences were detected for flexibility. Overall, the benefits of soccer training were exhibited by the larger improvements in fat mass, fat-free mass, sit-ups, and handgrip strength performance, underlining the important role of soccer participation during adolescence.



#13 Validation of a New Soccer Shooting Test Based on Speed Radar Measurement and Shooting Accuracy

Reference: Children (Basel). 2023 Jan 20;10(2):199. doi: 10.3390/children10020199.

Authors: Felix Engler, Andreas Hohmann, Maximilian Siener

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Summary: Due to poor results, the German talent identification and development of the German soccer association DFB no longer performs a shooting test since a few years. The aim of this study was to create and validate a new soccer shooting test that allows valid conclusions to be drawn from the shooting quality of youth soccer players about their overall soccer skills. The shooting test was performed with a total of 57 male club players (age: 15.24 ± 0.864 years) from four different teams from the first, second, fifth, and the seventh division of the respective age group (under 15-year-olds until under 17-year-olds). Each subject took one shot at maximum shot speed and eight target shots, measuring accuracy and the shot speed. A multivariable linear regression analysis with forward selection revealed significant values for the variables average shot speed nondominant leg (p < 0.001) and total score (p = 0.004; accuracy × speed of every target shot). Based on these two variables, the soccer skills could be derived from the shooting skills of the adolescents in 57.4% of the cases. The study shows the importance of a good technique with the nondominant leg and of the ability to shoot accurately as well as fast simultaneously.



#14 Using A-Mode Ultrasound to Assess the Body Composition of Soccer Players: A Comparative Study of Prediction Formulas

Reference: Diagnostics (Basel). 2023 Feb 12;13(4):690.doi: 10.3390/diagnostics13040690.

Authors: Paul Muntean, Monica Neagu, Elena Amaricai, Horia G Haragus, Roxana Ramona Onofrei, Adrian Neagu

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Summary: For elite athletes, monitoring body composition is important for maximizing performance without health risks. Amplitude (A)-mode ultrasound (AUS) has attracted increasing attention as an alternative to skinfold thickness measurements commonly used for assessing the amount of body fat in athletes. AUS accuracy and precision, however, depend on the formula used to predict body fat percentage (%BF) from subcutaneous fat layer thicknesses. Therefore, this study evaluates the accuracy of the 1-point biceps (B1), 9-sites Parrillo, 3-sites Jackson and Pollock (JP3), and 7-sites Jackson and Pollock (JP7) formulas. Relying on the previous validation of the JP3 formula in college-aged male athletes, we took AUS measurements in 54 professional soccer players (aged 22.9 ± 3.83 y, mean ± SD) and compared the results given by different formulas. The Kruskal-Wallis test indicated significant differences (p < 10-6), and Conover's post hoc test revealed that the JP3 and JP7 data come from the same distribution, whereas the data given by B1 and P9 differ from all the others. Lin's concordance correlation coefficients for B1 vs. JP7, P9 vs. JP7, and JP3 vs. JP7 were 0.464, 0.341, and 0.909, respectively. The Bland-Altman analysis indicated mean differences of -0.5 %BF between JP3 and JP7, 4.7 %BF between P9 and JP7, and 3.1 %BF between B1 and JP7. This study suggests that JP7 and JP3 are equally valid, whereas P9 and B1 overestimate %BF in athletes.



#15 Sudden Cardiac Arrest in Basketball and Soccer Stadiums, the Role of Automated External Defibrillators: A Review. For the BELTRAN Study (BaskEtbaLl and soccer sTadiums: Registry on Automatic exterNal defibrillators)

Reference: Arrhythm Electrophysiol Rev. 2023 Jan;12:e03. doi: 10.15420/aer.2022.30.

Authors: Mario D Bassi, Juan M Farina, Jorge Bombau, Mario Fitz Maurice, Guillermo Bortman, Elaine Nuñez, Manlio Márquez, Norberto Bornancini, Adrian Baranchuk

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Summary: Sudden cardiac arrest (SCA) during sports events has a dramatic impact on stadium-goers and the public and is often associated with poor outcomes unless treated with an automated external defibrillator (AED). Despite this, stadiums vary in AED use. This review aims to identify the risks and incidences of SCA, and the use of AEDs in soccer and basketball stadiums. A narrative review of all relevant papers was conducted. Athletes across all sports face an SCA risk of 1:50,000 athlete-years, with the greatest risk of SCA in young male athletes (1:35,000 person-years) and black male athletes (1:18,000 person-years). Africa and South America have the poorest soccer SCA outcomes at 3% and 4% survival. AED use on-site improves survival greater than defibrillation by emergency services. Many stadiums do not have AEDs implemented into medical plans and the AEDs are often unrecognisable or are obstructed. Therefore, AEDs should be used on-site, use clear signalling, have certified trained personnel, and be incorporated into stadiums' medical plans.



#16 Age of first exposure to soccer heading: Associations with cognitive, clinical, and imaging outcomes in the Einstein Soccer Study

Reference: Front Neurol. 2023 Feb 9;14:1042707. doi: 10.3389/fneur.2023.1042707. eCollection 2023.

Authors: Molly F Charney, Kenny Q Ye, Roman Fleysher, Bluyé DeMessie, Walter F Stewart, Molly E Zimmerman, Mimi Kim, Richard B Lipton, Michael L Lipton

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Summary: The objective of this study is to assess the role of age at first exposure (AFE) to soccer heading as a predictor of known adverse associations of recent and longer-term heading with brain microstructure, cognitive, and behavioral features among adult amateur soccer players. The sample included 276 active amateur soccer players (196 male and 81 female) aged 18-53 years old. AFE to soccer heading was treated as a binary variable, dichotomized at ≤ 10 years vs. >10 years old, based on a recently promulgated US Soccer policy, which bans heading for athletes ages 10 and under. We found that soccer players who began heading at age 10 or younger performed better on tests of working memory (p = 0.03) and verbal learning (p = 0.02), while accounting for duration of heading exposure, education, sex, and verbal intelligence. No difference in brain microstructure or behavioral measures was observed between the two exposure groups. The findings indicate that, among adult amateur soccer players, AFE to heading before age 10 compared to later start of heading, is not associated with adverse outcomes, and may be associated with better cognitive performance in young adulthood. Cumulative heading exposure across the lifespan, rather than early life exposure, may drive risk for adverse effects and should be the focus of future longitudinal studies to inform approaches to enhance player safety.



#17 How do soccer players sprint from a tactical context? Observations of an English Premier League soccer team

Reference: J Sports Sci. 2023 Feb 27;1-12. doi: 10.1080/02640414.2023.2183605. Online ahead of print.

Authors: Paul Caldbeck, Thomas Dos'Santos

Summary: The aim of this study was to quantify and tactically contextualise (i.e., phase of play and tactical outcome [TO]) sprints (≥7.0 m/s) of an English Premier League (EPL) soccer team during match-play. Videos of 901 sprints (10 matches) were evaluated using the Football Sprint Tactical-Context Classification System. Sprints occurred within a variety of phases of play (attacking/defensive organisation and transitions) and TOs, both out- and in-possession, with position-specific differences. Most sprints were completed out-possession (58%), with "closing down" the most observed TO (28%). In-possession, "run the channel" (25%) was the most observed TO. Centre backs predominantly performed "ball down the side" sprints (31%), whereas central midfielders mostly performed "covering" sprints (31%). Central forwards and wide midfielders mostly performed "closing down" (23% and 21%) and "run the channel" (23% and 16%) sprints when out- and in-possession, respectively. Full backs most frequently performed "recovery" and "overlap" runs (14% each). This study provides insights into the specific physical-tactical characteristics of sprints performed from an EPL soccer team. This information can be used to assist in the development of position-specific physical preparation programmes, and more ecologically valid and contextualised gamespeed and agility sprint drill construction to better reflect the demands of soccer.



#18 Indirect Rectus Femoris Injury Mechanisms in Professional Soccer Players: Video Analysis and Magnetic Resonance Imaging Findings

Reference: Clin J Sport Med. 2023 Feb 28. doi: 10.1097/JSM.0000000000001131. Online ahead of print.

Authors: Aleksi Jokela, Sandra Mechó, Giulio Pasta, Pavel Pleshkov, Alvaro García-Romero-Pérez, Stefano Mazzoni, Jussi Kosola, Filippo Vittadini, Javier Yanguas, Ricard Pruna, Xavier Valle, Lasse Lempainen

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Summary: The aim was to describe injury mechanisms and magnetic resonance imaging (MRI) findings in acute rectus femoris (RF) injuries of soccer players using a systematic video analysis. Professional male soccer players aged between 18 and 40 years, referred for injury assessment within 7 days after a RF injury, with an available video footage of the injury and a positive finding on an MRI. Rectus femoris injury mechanisms (specific scoring based on standardized models) in relation to RF muscle injury MRI findings were used as independent variables while Rectus femoris injury mechanism (playing situation, player/opponent behavior, movement, and biomechanics), location of injury in MRI were used as main outcome measures. Twenty videos of RF injuries in 19 professional male soccer players were analyzed. Three different injury mechanisms were seen: kicking (80%), sprinting (10%), and change of direction (10%). Isolated single-tendon injuries were found in 60% of the injuries. Of the kicking injuries, 62.5% included complete tendon ruptures, whereas both running injuries and none of the change of direction injuries were complete ruptures. The direct tendon was involved in 33% of the isolated injuries, and the common tendon was affected in all combined injuries. Rectus femoris injuries typically occur during kicking among football players. Most of the RF injuries involve a complete rupture of at least one tendon. Kicking injuries can also affect the supporting leg, and sprinting can cause a complete tendon rupture, whereas change of direction seems not to lead to complete ruptures.



#19 Erratum: The Qatar 2022 World Cup warm-up: Football goal-scoring evolution in the last 14 FIFA World Cups (1966-2018)

Reference: Front Psychol. 2023 Feb 10;14:1156698. doi: 10.3389/fpsyg.2023.1156698. eCollection 2023.

Authors: Frontiers Production Office

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#20 The Design of GNSS/IMU Loosely-Coupled Integration Filter for Wearable EPTS of Football Players

Reference: Sensors (Basel). 2023 Feb 4;23(4):1749. doi: 10.3390/s23041749.

Authors: Mingu Kim, Chulwoo Park, Jinsung Yoon

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Summary: This study presents the filter design of GNSS/IMU integration for wearable EPTS (Electronic Performance and Tracking System) of football players. EPTS has been widely used in sports fields recently, and GNSS (Global Navigation Satellite System) and IMU (Inertial Measurement Unit) in wearable EPTS have been used to measure and provide players' athletic performance data. A sensor fusion technique can be used to provide high-quality analysis data of athletic performance. For this reason, the integration filter of GNSS data and IMU data is designed in this study. The loosely-coupled strategy is considered to integrate GNSS and IMU data considering the specification of the wearable EPTS product. Quaternion is used to estimate a player's attitude to avoid the gimbal lock singularity in this study. Experiment results validate the performance of the proposed GNSS/IMU loosely-coupled integration filter for wearable EPTS of football players.



#21 Definition of High-Risk Motion Patterns for Female ACL Injury Based on Football-Specific Field Data: A Wearable Sensors Plus Data Mining Approach

Reference: Sensors (Basel). 2023 Feb 15;23(4):2176. doi: 10.3390/s23042176.

Authors: Stefano Di Paolo, Eline M Nijmeijer, Laura Bragonzoni, Alli Gokeler, Anne Benjaminse

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Summary: The aim of the present study was to investigate if the presence of anterior cruciate ligament (ACL) injury risk factors depicted in the laboratory would reflect at-risk patterns in football-specific field data. Twenty-four female footballers (14.9 ± 0.9 year) performed unanticipated cutting maneuvers in a laboratory setting and on the football pitch during football-specific exercises (F-EX) and games (F-GAME). Knee joint moments were collected in the laboratory and grouped using hierarchical agglomerative clustering. The clusters were used to investigate the kinematics collected on field through wearable sensors. Three clusters emerged: Cluster 1 presented the lowest knee moments; Cluster 2 presented high knee extension but low knee abduction and rotation moments; Cluster 3 presented the highest knee abduction, extension, and external rotation moments. In F-EX, greater knee abduction angles were found in Cluster 2 and 3 compared to Cluster 1 (p = 0.007). Cluster 2 showed the lowest knee and hip flexion angles (p < 0.013). Cluster 3 showed the greatest hip external rotation angles (p = 0.006). In F-GAME, Cluster 3 presented the greatest knee external rotation and lowest knee flexion angles (p = 0.003). Clinically relevant differences towards ACL injury identified in the laboratory reflected at-risk patterns only in part when cutting on the field: in the field, low-risk players exhibited similar kinematic patterns as the high-risk players. Therefore, in-lab injury risk screening may lack ecological validity.






Genetic Variations between Youth and Professional Development Phase English Academy Football Players

The purpose of this study was to examine differences in the genotype frequency distribution of thirty-three single nucleotide variants (SNVs) between youth development phase (YDP) and professional development phase (PDP) academy football players.





Effect of playing position and microcycle days on the acceleration speed profile of elite football players

The aim of this study was to analyse the differences in the A–S profile of elite football players induced

by playing position and the microcycle day.





Latest research in football - week 7 - 2023

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 Video Analytics in Elite Soccer: A Distributed Computing Perspective

Reference: Proc IEEE Sens Array Multichannel Signal Process Workshop. 2022 Jun;2022:221-225.  doi: 10.1109/SAM53842.2022.9827827. Epub 2022 Jul 22.

Authors: Debesh Jha, Ashish Rauniyar, Håvard D Johansen, Dag Johansen, Michael A Riegler, Pål Halvorsen, Ulas Bagci

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Summary: Ubiquitous sensors and Internet of Things (IoT) technologies have revolutionized the sports industry, providing new methodologies for planning, effective coordination of training, and match analysis post game. New methods, including machine learning, image and video processing, have been developed for performance evaluation, allowing the analyst to track the performance of a player in real-time. Following FIFA's 2015 approval of electronics performance and tracking system during games, performance data of a single player or the entire team is allowed to be collected using GPS-based wearables. Data from practice sessions outside the sporting arena is being collected in greater numbers than ever before. Realizing the significance of data in professional soccer, this paper presents video analytics, examines recent state-of-the-art literature in elite soccer, and summarizes existing real-time video analytics algorithms. We also discuss real-time crowdsourcing of the obtained data, tactical and technical performance, distributed computing and its importance in video analytics and propose a future research perspective.



#2 An assist for cognitive diagnostics in soccer (Part II): Development and validation of a task to measure working memory in a soccer-specific setting

Reference: Front Psychol. 2023 Jan 23;13:1026017. doi: 10.3389/fpsyg.2022.1026017. eCollection 2022.

Authors: Simon Knöbel, Franziska Lautenbach

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Summary: Cognitive diagnostics is of increasing interest to researchers and practitioners in the context of talent identification and performance enhancement in professional soccer. Research addressing the relevance of cognitive skills for sports performance has been based on the cognitive component approach (i.e., general cognitive processes) and the expert performance approach (i.e., sport-specific cognitive processes). Following the aim to combine the strengths of both approaches, we have previously developed and validated tasks to measure inhibition and cognitive flexibility in a soccer-specific setting, including a soccer-specific motor response. In line with the broad consistency on three core executive functions, this further development of diagnosing executive functions is to be completed with a task for the assessment of working memory. For this purpose, 60 amateur players with a soccer experience of at least one competitive season (M age = 25.95, SD age = 4.59) first conducted a computer-based version of the n-back (3-back) task followed by a 3-back task that required a soccer-specific motor response (i.e., pass) performed in a soccer-specific setting (i.e., SoccerBot100). Results show good reliability for both tasks. With regard to convergent validity, significant correlations between the computerized and soccer-specific task could be determined in target trials for response time (r = 0.446) and accuracy (r = 0.401). Thus, the soccer-specific n-back task can be considered a potentially valid instrument for assessing working memory and potentially allows soccer clubs to diagnose the three core executive functions in a consistent soccer-specific setting.



#3 Dietary supplements and beverages: Knowledge, attitudes, and practices among semi-professional soccer players in KwaZulu-Natal, South Africa

Reference: S Afr J Sports Med. 2022 Jan 1;34(1):v34i1a14018. doi: 10.17159/2078-516X/2022/v34i1a14018. eCollection 2022.

Authors: S Nyawose, R Naidoo, N Naumovski, A J McKune

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Summary: The ingestion of dietary supplements and beverages is prevalent in soccer, at the amateur and professional level. The absence of professional advice at non-professional level makes amateur soccer players susceptible to ingesting unsafe supplements. The aim was to determine the knowledge, attitudes and practices of ABC Motsepe League (semi-professional) players in KwaZulu-Natal regarding the use of dietary supplements and beverages. Three hundred and forty-three soccer players participated in a cross-sectional study. Knowledge, attitudes and practices were determined using a questionnaire. Researchers visited twelve teams. On the day of the visit to each team, information sheets and questionnaires were given to participants. Questionnaires were collected immediately following completion. Descriptive statistics were used, including means and standard deviations, where applicable. Inferential statistics, Chi-square and binomial tests were used to analyse the results. Statistical significance was set at p < 0.05. Sports beverages were the most recommended and commonly used, followed by energy beverages. Dietary supplements were the least-known used. Participants used beverages and dietary supplements to assist in providing more energy (67%), improve health (65%) and improve performance (55%) (p<0.001). Seventy-three percent of participants lacked knowledge about the anti-doping policy (p<0.001), with 87% having never attended a workshop on the safe use of supplements and beverages, or anti-doping awareness campaigns (p<0.001). Thirty-eight percent had not heard of the South African Institute for Drug-Free Sport (SAIDS), and 84% were not familiar with the yearly updated World Anti-Doping Agency's (WADA) prohibited list (p<0.001). Of the 59% who did not take dietary supplements or beverages, 75% had insufficient information regarding them (p<0.001), 66% indicated that dietary supplements and beverages were costly (p=0.001), and 55% indicated they did not need dietary supplements and beverages (p=0.32). There is a need for an educational programme on the safe use of dietary supplements, and sports and energy beverages among KwaZulu-Natal semi-professional soccer players.



#4 Cognitive function in soccer athletes determined by sleep disruption and self-reported health, yet not by decision-reinvestment

Reference: Front Neurol. 2023 Feb 6;13:872761. doi: 10.3389/fneur.2022.872761. eCollection 2022.

Authors: Jasmin Pourhassan, Jane Sarginson, Wolfgang Hitzl, Kneginja Richter

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Summary: Sleep disruption (SD) increases sympathetic activity and cortisol secretion, and delays cognitive functions such as reaction-time (RT). Sympathetic activity of disturbed sleepers, is similar to those of so-called decision-reinvesters. Decision-reinvestment refers to traits in individuals with greater tendency to ruminate and reinvest in their decisions, with significant decrease in both motor-control and cognitive performance. Decision-making quality is a crucial attribute to athletic performance which relies on RT. Consequently, SD affects pitch-performance negatively, particularly in decision-reinvesters. This observational pilot-study examined the relationship between SD and cognitive function, perceived health, as well as reinvestment strategies. The hypothesis was that athletes with lower SD perceive their health better, report lower stress levels, perform better in cognitive tasks, and show lower tendency for decision-reinvestment. Twenty-one football player recorded their sleep with fit-trackers for 7 nights. Participants self-reported their mental and physical health, decision-reinvestment strategy, sleep behaviour, and perceived stress levels. Athletes then performed a set of cognitive tests to examine memory function (Backwards Corsi), selective attention (STROOP), and cognitive flexibility (Wisconsin Card Sorting Test, WCST). Normality was tested with a Shapiro-Wilk test, and analysed with a Pearson's or Spearman's correlation test. Significant correlation appeared between extended sleep-interruptions and Backwards Corsi RT, r = 0.66, p = 0.010, as further in total sleep time and wellbeing r = 0.50, p = 0.029. A negative correlation exist in regard of pain scores and Backwards Corsi scores r = -0.57, p = 0.110. Physical health correlated with error-rates in the WCST, r = 0.69, p ≤ 0.001. Also, reinvestment negatively correlated with physical health, r = -0.80, p ≤ 0.001. Wellbeing relies on total sleep-time. Athletes with extended sleep-interruptions are slower in recalling memory, and those with greater reported pain have lower memory scores. Participants who rate physical health greater, have more error-rates in the WCST; indicating that cognitive flexibility is enhanced in individuals with inferior perceived health. However, individuals with lower physical health scores also have greater tendency to ruminate and reinvest in decisions, suggesting interrelation between reinvestment and physical health.



#5 External load profile during different sport-specific activities in semi-professional soccer players

Reference: BMC Sports Sci Med Rehabil. 2023 Feb 22;15(1):22. doi: 10.1186/s13102-023-00633-3.

Authors: Guglielmo Pillitteri, Valerio Giustino, Marco Petrucci, Alessio Rossi, Marianna Bellafiore, Ewan Thomas, Angelo Iovane, Antonino Bianco, Antonio Palma, Giuseppe Battaglia

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Summary: Global Positioning System (GPS) devices are widely used in soccer for monitoring external load (EL) indicators with the aim of maximizing sports performance.The aim of this study was to investigate the EL indicators differences in players of different playing positions (i.e., central backs, external strikers, fullbacks, midfielders, strikers, wide midfielder) between and within different sport-specific tasks and official matches. 1932 observations from 28 semi-professional soccer players (age: 25 ± 6 years, height: 183 ± 6 cm, weight: 75.2 ± 7 kg) were collected through GPS devices (Qstarz BT-Q1000EX, 10 Hz) during the season 2019-2020. Participants were monitored during Official Match (OM), Friendly Matches (FM), Small Sided Games (SSG), and Match-Based Exercises (MBE). Metabolic (i.e., metabolic power, percentage of metabolic power > 35w, number of intense actions per minute, distance per minute, passive recovery time per minute) and neuromuscular indicators (i.e., percentage of intense accelerations, percentage of intense decelerations, change of direction per min > 30°) were recorded during each task. Statistically significant differences were detected in EL indicators between playing positions within each task and between tasks. In particular, results from the two-way ANOVA tests showed significant interaction, but with small effect size, in all the EL indicators between playing positions for each task and within tasks. Moreover, statistical differences, but with small effect size, between playing positions were detected in each task and for each EL indicator. Finally, the strongest statistical differences (with large effect size) were detected between tasks for each EL indicator. Details of the Tukey post-hoc analysis reporting the pairwise comparisons within and between tasks with playing positions are also provided. In semi-professional soccer players, different metabolic and neuromuscular performance were detected in different playing position between and within different tasks and official matches. Coaches should consider the different physical responses related to different physical tasks and playing position to design the most appropriate training program.



#6 Soccer and Benign Paroxysmal Positional Vertigo

Reference: Case Rep Otolaryngol. 2023 Feb 14;2023:3744863. doi: 10.1155/2023/3744863. eCollection 2023.

Authors: Nikolaj Warming, Stephanie Balslev Andersen, Dan Dupont Hougaard

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Summary: Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo among adults. The etiology of BPPV is unknown in approximately 50 percent of cases. This condition is also termed primary BPPV, if the etiology is unknown, and secondary BPPV if patients have identified predisposing factors. A few studies suggest that there is a correlation between the development of BPPV and specific sports. A 19-year-old male presented with recurrent episodes of vertigo during soccer play. Eight months prior to referral, the patient was involved in a car accident with a mild head trauma. The patient was later diagnosed with BPPV several times. Soccer might be a plausible BPPV trigger, especially if there is a prehistory of head trauma. This is most likely due to the demands of the game such as the change of directions, repetitive head impacts (headers or head collisions), accelerations/decelerations, jumps, foot landings, and rapid head movements.



#7 Match Load Physical Demands in U-19 Professional Soccer Players Assessed by a Wearable Inertial Sensor

Reference: J Funct Morphol Kinesiol. 2023 Feb 7;8(1):22. doi: 10.3390/jfmk8010022.

Authors: Guglielmo Pillitteri, Valerio Giustino, Marco Petrucci, Alessio Rossi, Ignazio Leale, Marianna Bellafiore, Ewan Thomas, Angelo Iovane, Antonio Palma, Giuseppe Battaglia

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Summary: Wearable inertial sensors are poorly used in soccer to monitor external load (EL) indicators. However, these devices could be useful for improving sports performance and potentially reducing the risk of injury. The aim of this study was to investigate the EL indicators (i.e., cinematic, mechanical, and metabolic) differences between playing positions (i.e., central backs, external strikers, fullbacks, midfielders, and wide midfielder) during the first half time of four official matches (OMs). 13 young professional soccer players (Under-19; age: 18.5 ± 0.4 years; height: 177 ± 6 cm; weight: 67 ± 4.8 kg) were monitored through a wearable inertial sensor (TalentPlayers TPDev, firmware version 1.3) during the season 2021-2022. Participants' EL indicators were recorded during the first half time of four OMs. Significant differences were detected in all the EL indicators between playing positions except for two of them (i.e., distance traveled in the various metabolic power zones (<10 w) and the number of direction changes to the right >30° and with speed >2 m). Pairwise comparisons showed differences in EL indicators between playing positions. Young professional soccer players showed different loads and performances during OMs in relation to playing positions. Coaches should consider the different physical demands related to playing positions in order to design the most appropriate training program.



#8 Reliability of the Coimbra Reactive Agility Soccer Test (CRAST)

Reference: J Funct Morphol Kinesiol. 2023 Jan 18;8(1):11. doi: 10.3390/jfmk8010011.

Authors: António Nóbrega, Hugo Sarmento, Vasco Vaz, Vítor Gouveia, Joel Barrera, Andreia Martins, Tomás Santos, João Pedro Duarte

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Summary: Agility is a fitness-skill-related component that should be a part of the standard physiological testing for soccer players and one of the key performance indicators in soccer. The present study aimed to assess the reliability of the CRAST as a research tool in the study of soccer skills. Twenty-one university soccer players (chronological age: 19.3 ± 1.4 years; body mass: 69.6 ± 8.2 kg; stature: 173.5 ± 6.5 cm; federated training experience: 9.7 ± 3.6 years) volunteered for the testing protocol. The CRAST requires players to complete random courses six times as quickly as possible. In addition, the CRAST requires players to control and dribble the markers (four different colors: green, yellow, blue, and red). The soccer players completed three trials, each separated by one week. The first trial accounted for familiarization; the second and third were considered for analysis. The correlation for overall performance was very strong. The reliability of the CRAST was slightly better for total time than that for the penalty score (0.95 vs. 0.93). The TEM and the associated CV range of 7.04%-7.54% were for the penalty score and the total time, respectively. For both measurements, the ICC values also represent excellent reliability, as both values were over 0.900. The CRAST is a reliable protocol for assessing agility in soccer players.



#9 Majority of competitive soccer players return to soccer following hip arthroscopy for femoroacetabular impingement: female and older aged players are less likely to return to soccer

Reference: Knee Surg Sports Traumatol Arthrosc. 2023 Feb 21. doi: 10.1007/s00167-023-07349-4.

Authors: Niv Marom, Reena Olsen, Joost A Burger, Matthew S Dooley, Struan H Coleman, Anil S Ranawat, Bryan T Kelly, Danyal H Nawabi

Summary: The aim was to determine return to soccer rates and soccer performance in a large cohort of competitive soccer players after hip arthroscopic surgery for the treatment of femoroacetabular impingement (FAI) and to identify possible risk factors associated with not returning to soccer. An institutional hip preservation registry was retrospectively reviewed for patients identified as competitive soccer players who underwent primary hip arthroscopy for FAI performed between 2010 and 2017. Patient demographics and injury characteristics as well as clinical and radiographic findings were recorded. All patients were contacted for return to soccer information using a soccer-specific return to play questionnaire. Multivariable logistic regression analysis was used to identify potential risk factors for not returning to soccer. Eighty-seven competitive soccer players (119 hips) were included. 32 players (37%) underwent simultaneous or staged bilateral hip arthroscopy. The mean age at surgery was 21.6 ± 7.0 years. Overall, 65 players (74.7%) returned to soccer, of which 43 players (49% of all included players) returned to pre-injury level of play or better. Most common reasons for not returning to soccer were pain or discomfort (50%) followed by fear of re-injury (31.8%). The mean time to return to soccer was 33.1 ± 26.3 weeks. Among 22 players who did not return to soccer, 14 (63.6%) reported satisfaction from surgery. Multivariable logistic regression analysis revealed female players (odds ratio [OR] = 0.27; confidence interval [CI] = 0.083 to 0.872; p = 0.029) and older aged players (OR = 0.895; 95% CI = 0.832 to 0.963; p = 0.003) were less likely to return to soccer. Bilateral surgery was not found to be a risk factor. Hip arthroscopic treatment for FAI in symptomatic competitive soccer players allowed three-quarters of them to return to soccer. Despite not returning to soccer, two-thirds of players who did not return to soccer were satisfied with their outcome. Female and older aged players were less likely to return to soccer. These data can better guide clinicians and soccer players with realistic expectations related to the arthroscopic management of symptomatic FAI.



#10 An overview of injury prevention for soccer players in Pakistan: A sports rehab perspective

Reference: J Pak Med Assoc. 2023;73(1(B)):435-437. doi: 10.47391/JPMA.15-23.

Authors: Muhammad Furqan Hassan, Furqan Ahmed Siddiqi, Muhammad Salman Bashir, Farooq Azam Rathore

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Summary: Soccer (football) is one of the most popular weight-bearing sports in the world, which involves activities such as jumping, running and turning. Soccer related injuries have the highest incidence in all sports and are more common in young amateur players. The most important modifiable risk factors include neuromuscular control, postural stability, hamstring strength and core dysfunction. The International Federation of Football Association introduced FIFA 11+; an injury prevention programme for reduction in the rate of injuries in amateur and young soccer players. It focusses on the training of dynamic, static and reactive neuromuscular control, proper posture, balance, agility and control of the body. This training protocol is not being used in Pakistan at amateur level who neither possess the resources, nor the knowledge or proper guidance in risk factor assessment, prevention, and subsequent sport injury management. In addition, the physicians and rehabilitation community are not much familiar with it except for those directly involved in sports rehabilitation. This review highlights the importance of including FIFA 11+ training programme in the curriculum and faculty training.



#11 Effects of Combined Horizontal Plyometric and Change of Direction Training on Anaerobic Parameters in Youth Soccer Players

Reference: Sports (Basel). 2023 Jan 26;11(2):27. doi: 10.3390/sports11020027.

Authors: Yiannis Michailidis, Panagiotis Venegas, Thomas Metaxas

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Summary: The aim of this study is to investigate whether the combination of soccer training, plyometric training (PT), and change of direction (COD) exercises would enhance anaerobic performance to a greater extent than training on its own in youth U17 soccer players. Twenty youth players participated in this study. Players were randomly separated into two groups: the control group (CG, n = 9) and the intervention group (EX), which performed extra PT and COD exercises (EX, n = 11). The duration of the training program was six weeks. Sprint 10 m, 30 m, countermovement jump (CMJ), single leg countermovement jump (CMJ right and left), squat jump (SJ), 505 test, and Illinois agility test were measured pre and post of the training program. The performance in the 505 test improved for the EX group (right leg: p = 0.031, left leg: p = 0.004). In addition, Illinois test performance increased in the EX group (2.9%, p = 0.019). The performances of the two groups differed significantly in the Illinois agility test (p = 0.001). This study supports that a short-term combined program of PT and COD exercises can improve change of direction ability in youth U17 soccer players. The lack of effect of the intervention program on sprint and jump performance may be due to the type and volume of plyometric exercises used. The results reflect the training principle of specialization of stimulus. The improvement in performance was presented in tests that had similar characteristics to training stimuli.



#12 Protein Intake in NCAA Division 1 Soccer Players: Assessment of Daily Amounts, Distribution Patterns, and Leucine Levels as a Quality Indicator

Reference: Sports (Basel). 2023 Feb 14;11(2):45. doi: 10.3390/sports11020045.

Authors: Jun Kwon, Morgan M Nishisaka, Alexandra F McGrath, Aleksandra S Kristo, Angelos K Sikalidis, Scott K Reaves

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Summary: Dietary protein is required to support recovery and adaptation following exercise training. While prior research demonstrates that many athletes meet total daily protein needs, intake seems to be predominantly skewed toward the evening meal. An even distribution of protein doses of ≥0.24 g/kg BW consumed throughout the course of a day is theorized to confer greater skeletal muscle anabolism outcomes compared to a skewed pattern of intake. Protein quality is also an important dietary consideration for athletes, with the amino acid leucine seemingly serving as the primary driver of the postprandial anabolic response. The present study investigates protein consumption characteristics among a cohort of NCAA D1 soccer players and evaluates differences between male and female athletes. Athletes were instructed to complete 3-day food diaries, which were subsequently analyzed and compared to UEFA expert group-issued nutrition guidelines for soccer players. Breakfast, lunch, and dinner accounted for 81.4% of the total daily dietary protein intake. Most athletes (77.8%) ingested optimum amounts of protein at dinner but not at breakfast (11.1%) or lunch (47.2%). In addition, statistically significant sex-based differences in daily dietary protein intake, meal-specific protein amounts, and protein quality measures were detected. Findings indicate suboptimal dietary protein intake practices among the collegiate soccer athletes.



#13 Weekly screening of youth male football players: a 14-week longitudinal investigation of interactions between groin pain and long lever adductor squeeze strength

Reference: J Sci Med Sport. 2023 Feb 10;S1440-2440(23)00031-2. doi: 10.1016/j.jsams.2023.02.003.

Authors: Matthew D DeLang, J Craig Garrison, Joseph P Hannon, Lasse Ishøi, Kristian Thorborg

Summary: The aim was o explore relationships between groin pain and adductor squeeze strength in male academy football players over a 14-week period. Weekly monitoring of youth male football players consisted of reporting groin pain and testing long lever adductor squeeze strength. Players who reported groin pain at any time during the study period were stratified into the "groin pain" group while players who did not report pain remained in the "no groin pain" group. Baseline squeeze strength was retrospectively compared between groups. Players that developed groin pain were examined via repeated measures ANOVA at four timepoints: baseline, last squeeze before pain, pain onset, and return to pain-free. 53 players were included (age 14.4 ± 1.6 years). Baseline squeeze strength was not different between players in the "groin pain" (n = 29, 4.35 ± 0.89 N/kg) versus "no groin pain" group (n = 24, 4.33 ± 0.90 N/kg, p = 0.83). At a group level, players with no groin pain maintained similar adductor squeeze strength throughout 14 weeks (p > 0.05). Compared to baseline (4.33 ± 0.90 N/kg), players with groin pain had decreased adductor squeeze strength at the last squeeze before pain (3.91 ± 0.85 N/kg, p = 0.003) and at pain onset (3.58 ± 0.78 N/kg, p < 0.001). Adductor squeeze strength at the point where pain subsided (4.06 ± 0.95 N/kg) was not different from baseline (p = 0.14). Decreases in adductor squeeze strength manifest one-week prior to groin pain onset and further decrease at pain onset. Weekly adductor squeeze strength may be an early detector for groin pain in youth male football players.



#14 Effect of Increasing the Number of Substitutions on Physical Performance during Periods of Congested Fixtures in Football

Reference: Sports (Basel). 2023 Jan 19;11(2):25. doi: 10.3390/sports11020025.

Authors: Abraham García-Aliaga, Adrián Martín-Castellanos, Moisés Marquina Nieto, Diego Muriarte Solana, Ricardo Resta, Roberto López Del Campo, Daniel Mon-López, Ignacio Refoyo

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Summary: (I) This study aimed to evaluate the impact on physical demands induced by FIFA's new rule implemented based on the number of substitutions caused by COVID-19. (II) Sixty-six matches were analysed in peak periods (microcycles of three matches in a week) in the competition period before and after the pandemic. The variables collected were organised by team (22 from LaLigaTM SmartBank 2019-2020) for a total of 132 team records and 1077 player performance reports using a multi-camera tracking system and Mediacoach® software. Physical performance variables were analysed in the first half, second half and whole match, thus determining the individual and collective performances of the team. (III) This study shows how, despite the increase in substitutions allowed with the new rule, physical performance increased in some variables in the congested periods (e.g., total distance run and distance run in the first and second halves). Additionally, the players' physical performance involved in a substitution was greater than it was for players who completed the game. (IV) The new substitution rule helps to maintain and even improve physical performance. This measure could improve intensity levels in both individual and team performance. It could even safeguard the physical integrity of the players by reducing the risk of injury, as fewer players have to play the full match.



#15 Measuring direct and indirect tendon parameters to characterize the proximal tendinous complex of the rectus femoris in football and futsal players

Reference: Front Physiol. 2023 Feb 7;14:986872. doi: 10.3389/fphys.2023.986872. eCollection 2023.

Authors: Sandra Mechó, Raquel Lisbona Ortega, Ricard Pruna, Lexa Nescolarde Selva, Jordi Morillas Pérez, Alfonso Rodríguez-Baeza, Javier Martínez Agea, Ricard Pérez-Andrés

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Summary: The aim was to present unprecedented radiological parameters that characterize the angle between the direct and indirect tendons of the proximal rectus femoris (RF) and its inclinations and to evaluate the population variability according to demographic variables. From September 2019 to July 2021, using MRI multiplanar reconstructions of the proximal thigh/hip, two blinded radiologists measured the direct and indirect tendon angle and the inclination of each tendon in different planes. The intra- and inter-observer agreements were assessed with Bland-Altman analysis and intraclass correlation coefficient (ICC). The correlations between radiological parameters and demographic variables were evaluated using linear regression, Student's t-test, and analysis of variance. We performed 112 thigh/hip MRI scans on 91 football players of different age, gender, and disciplines (football and futsal). For observer 1 (the reference), the mean direct and indirect tendon angle was 56.74° ± 9.37, the mean indirect tendon slope was -7.90° ± 7.49, and the mean direct tendon slope was 22.16° ± 5.88. The three measurements showed inter- and intra-observer agreement (mean differences ∼0). No correlation was observed between age and the parameters. Likewise, no statistically significant differences were found for gender, dominant limb, examined limb, and sport. There is an inter- and intra-observer agreement in the measurements of the direct and indirect tendon angle and the inclination of each tendon. There is population variability in the proximal tendinous complex unrelated to demographic factors. These results allow further detection of morphological patterns that represent a risk factor for lesions in the RF in professional football and futsal players and other sports.



#16 Peak Running Speeds in Professional Male Football: Influence of Division and Playing Position

Reference: J Strength Cond Res. 2023 Mar 1;37(3):636-640. doi: 10.1519/JSC.0000000000004298. Epub 2022 Jul 1.

Authors: Jack T Fahey, Kristian Aldred, Matt Greig, David Rhodes

Summary: Well-established physical demands of competitive professional football facilitate prescription and monitoring of training. However, many factors influence these physical demands with implications for efficacious practice. Match-play data were analyzed over 2 seasons using global positioning systems technology, differentiating English Championship (33 matches) and League One (27 matches) demands. Playing position categorized wide and central defenders and midfielders and forwards. Peak running speeds defined the outcome measure, assessing the influence of the competition level and playing position across 1, 5, and 10-minute rolling average durations using a linear mixed model. Significant effects were detected for the competition level (F1,324.5 = 5.44, p = 0.02) and playing position (F4,328.3 = 89.90, p < 0.001). League One matches demonstrated greater peak running speeds than Championship matches (mean difference = 2.72 m·min-1 [95% confidence intervals: 0.4, 5.0]). No difference was observed between central and wide midfielders (mean difference = 0.62 m·min-1 [95% confidence intervals: -3.1, 4.3]). Wide midfielders presented faster peak running speeds than forwards (mean difference = 18 m·min-1 [95% confidence intervals:14.1, 22.1], p < 0.05), central defenders (mean difference = 25 m·min-1 [95% confidence intervals: 21.7, 29.8], p < 0.05), and wide defenders (mean difference = 12 m·min-1 [95% confidence intervals: 8.2, 16.5], p < 0.05). Interaction effects were found for division*position (F4,328.3 = 2.57, p = 0.038) demonstrating greater running speeds in League One, except for central defenders. Wide midfielders presented greater peak 1-minute running speeds, whereas 5 and 10-minute peak running speeds were greatest in central midfielders. The sensitivity of peak running speeds to competition level and playing position has implications for training prescription, monitoring particularly when transitioning between competition levels, determining and monitoring positional training intensities, and objective targets for progressive overload during rehabilitation.



#17 The pattern of non-contact injuries in a South African professional football team

Reference: S Afr J Sports Med. 2022 Jan 1;34(1):v34i1a13723. doi: 10.17159/2078-516X/2022/v34i1a13723. eCollection 2022.

Authors: J Swart, C Varekamp, J Greyling

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Summary: The incidence, pattern and severity of non-contact injuries in European football has been researched extensively. In South African football only two studies have been conducted to date and with disparate outcomes. Further research into injury rates in South African football is therefore warranted. The aim was to determine the incidence and pattern of non-contact injuries in a South African professional football team during the course of a single season (2016-2017) in relation to competition exposure, training load and playing position. Thirty-four male professional football players belonging to a single team competing in the Premier Soccer League (PSL) in South Africa were studied. Non-contact time-loss injuries (total training and match injuries) were recorded. Injury incidence, location, severity, type, and playing position (defender, midfielder, attackers, goalkeepers) during either match play or training were recorded. The non-contact incidence was 52 injuries with an injury rate of 3.74 per 1 000 exposures (training and competition). Competitions resulted in an incidence of 26.4 injuries per 1 000 exposure and training incidence 2.08 injuries per 1 000 exposures. Hamstring, groin and quadriceps injuries were the most frequently injured locations and muscle-tendon injuries accounted for the majority of injuries. The majority of injuries (52%) occurred during match play while 48% occurred during training. The greatest absolute number of injuries were sustained by midfielders (50%), followed by defenders (33%) and attackers (17%). However, relative to player numbers, the greatest number of injuries during match play were for defenders (44%), attackers (32%) and midfielders (24%). During training attackers sustained the most injuries (39%), followed by defenders (31%) and midfielders (30%). Goalkeepers did not sustain any non-contact injuries during the duration of the study. The non-contact injury incidence in South African professional football players is similar to European football players. Hamstrings and groin injuries are predominant and were sustained throughout the competitive season. Defenders sustained the most non-contact injuries within the team relative to exposure time compared to attackers and midfielders. To our knowledge, injuries relative to player position have not been reported previously.



#18 Sport during the COVID-19 bio-bubble: Wellness and opinions in South African elite football

Reference: S Afr J Sports Med. 2022 Jan 1;34(1):v34i1a12528. doi: 10.17159/2078-516X/2022/v34i1a12528. eCollection 2022.

Authors: K Bahdur, L Pillay, D Dell'oca

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Summary: COVID-19 imposed challenges on professional sport, with restrictions leading to the delay in the completion of the South African Premier Soccer League (PSL). Creating a biologically safe environment (BSE) provided a solution enabling the 2019/2020 season to be completed. Evaluating the impact that the BSE had on player wellness and what coping mechanisms were used in the BSE. A questionnaire was distributed to PSL teams on the final weekend in the BSE. It consisted of three validated psychology questionnaires. An additional section focused on the impact and coping strategies during the PSL's BSE. A total of 37 completed questionnaires were analysed. General anxiety (4.7±4.2) and depression levels (4.8±3.9) were at an overall low. The health of the players, as well as separation from and concerns about family, were the greatest contributors to anxiety. Electronic communication with family and friends, social interactions with others in the BSE and time spent on self-reflection were important coping mechanisms for players. As time progressed, they adapted to the BSE. The BSE did not have a negative impact on the anxiety and depression levels of the respondents, with a variety of coping mechanisms key helping them adapt in the BSE.



#19 Injury, illness, and medication use surveillance during the 2020 COSAFA Women's championship: a prospective cohort study of football players from Southern Africa

Reference: Sci Med Footb. 2023 Feb;7(1):74-80. doi: 10.1080/24733938.2021.1971745. Epub 2021 Aug 30.

Authors: Nonhlanhla S Mkumbuzi, Senanile B Dlamini, Fidelis Chibhabha, Fredrick M Govere

Summary: Systematic analyses of injuries, illnesses or medication use and their risk factors among female African athletes are scarce, which has implications for management of these athletes. This prospective cohort study analysed the incidence and characteristics of injuries, illnesses and medication use during the 2020 COSAFA Women's Championship. The medical personnel of all participating teams reported all new injuries, illnesses and medication used by players daily. Sixty-three injuries were reported: 45 match and 18 training injuries; 45.5 (95% CI: 32.2 to 58.8) injuries/1000 match-hours and 21.7 (95% CI: 11.7 to 31.7) injuries/1000 training-hours, respectively. Most (n = 55, 87%) were caused by contact with another player and involved the lower extremity (n = 43; 68%). Fifty-eight illnesses were reported: 44.4 (95% CI: 33.0 to 58.8) illnesses/1000 player-days, mostly diarrhoea (n = 25; 43.1%) and dysmenorrhoea (n = 18; 31%). No cases of COVID-19 were reported. In total, 175 medications were prescribed: 168.8 (95% CI: 143.8 to 193.8) medications/1000 player-days. Non-steroidal anti-inflammatory drugs (NSAIDs) (n = 60; 34.3%) and analgesics (n = 33; 18.9%) were the most commonly prescribed drugs. Incidences of injury and illnesses were high but time loss was low, likely due to high NSAIDs use. Further studies should be conducted in order to inform appropriate prevention or management protocols in this population.






Variations in Accumulated-Training Load Parameters and Locomotor Demand with Consideration of Puberty in Elite Young Soccer Players

The study’s purposes were to examine the associations of training load parameters with locomotor demand and puberty status in elite young soccer players and to predict the percentage of changes in their performance ability with adjustments to the training load parameters, using multivariate regression analysis, while considering PHV and maturity offset.





Associations among Maturity, Accumulated Workload, Physiological, and Body Composition Factors in Youth Soccer

The purposes of this study were: (i) to analyze the correlation between accumulated workload (AW)—based on season periods—with maturity, linear sprints, maximum oxygen uptake (VO2max), maximum heart rate, and body composition; and (ii) to compare the playing positions based on the mentioned parameters.





Latest research in football - week 6 - 2023

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 High-intensity circuit training change serum myostatin but not myogenin in adolescents' soccer players: a quasi-experimental study

Reference: BMC Sports Sci Med Rehabil. 2023 Feb 6;15(1):15. doi: 10.1186/s13102-023-00627-1.

Authors: Amirhosein Ziyaiyan, Mohammadreza Kordi, Martin Hofmeister, Karim Chamari, Wassim Moalla, Abbas Ali Gaeini

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Summary: Skeletal muscle contractions due to exercise lead to the secretion of many proteins and proteoglycan peptides called myokines. Myostatin (MSTN) and Myogenin (MyoG) are two of the most important skeletal muscle growth regulatory factors related to myoblast differentiation and muscle hypertrophy. The present study aims at investigating the effects over eight weeks of high-intensity circuit training (HICT) on serum MyoG and MSTN in male soccer players. The present study is a quasi-experimental study on 21 male soccer players (Experimental group: n = 11, Control group: n = 10) (ages 15.0 ± 3.4 years, body mass 55.7 ± 7.8 kg, height 173.3 ± 8.0 cm, Body mass index 18.4 ± 1.9 kg m-2, maximum oxygen uptake 61.89 ± 3.01 ml kg-1 and the peak height velocity 14.5 ± 0.3 years). Participants were randomly divided into two groups: training group and a control group. The first resting blood samples were obtained in the morning-fasting state, and the second blood samples were obtained after the maximum aerobic test at pre- and post-HICT. There were non-significant differences in resting serum values of MyoG (p = 0.309, p > 0.05) but significant differences in resting serum values of MSTN between the training and control groups after eight weeks of HICT (p = 0.003, p < 0.05). No significant differences were observed between groups in the acute response of serum values of MyoG (p = 0.413, p < 0.05) and MSTN (p = 0.465, p < 0.05) to the maximum aerobic test after eight weeks of HICT. These results suggest that eight weeks of HICT can decrease the resting serum values of MSTN but not change the resting serum values of MyoG in male adolescent soccer players. Also, eight weeks of HICT does not affect the acute response of MSTN and MyoG after a maximum aerobic test.



#2 Cortical thickness and neurocognitive performance in former high-level female soccer and non-contact sport athletes

Reference: Scand J Med Sci Sports. 2023 Feb 6. doi: 10.1111/sms.14324. Online ahead of print.

Authors: Franziska Katharina Haase, Annika Prien, Linda Douw, Nina Feddermann-Demont, Astrid Junge, Claus Reinsberger

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Summary: Long-term effects of playing soccer (football) on the brain structure and function of the brain are vividly debated. While some studies showed differences in neurocognitive performance and structural brain changes in retired male players, data on female players are scarce. The present study compares cortical thickness and neurocognitive performance in former high-level female soccer (SOC) and non-contact sport athletes (CON). 3T T1-weighted 3D MPRAGE MRI was performed and vertex-wise cortical thickness was analyzed using FreeSurfer (v. 6.0.0). Neurocognitive performance in seven domains of SOC and CON was assessed. A multivariate linear model was used to analyze interactions with respect to heading frequency and a history of concussion. SOC (n=15, mean age 38.3 ± 5.1 years) and CON (n=16, mean age 36.6 ± 5.8 years) had a similar cortical thickness and performed similarly in the neurocognitive tests except for verbal memory and psychomotor speed, where SOC performed significantly worse than CON. Moderate headers had a significantly larger cortical thickness than rare headers in the right inferior parietal region. Visual memory and cortical thickness were positively correlated in the group of frequent headers and negatively correlated in CON, but not in the other header groups. In contrast to previous reports in male football players, female players did not reveal cortical thinning in comparison to control athletes, whereas neurocognitive profiles of female football players might not significantly differ from male athletes. Small sample sizes, subjective header assessment and the case-control study design require a cautious interpretation.



#3 'Football and dancing are in our blood': culture promoting sports practice among immigrants in Europe

Reference: Health Promot Int. 2023 Feb 1;38(1):daac202. doi: 10.1093/heapro/daac202.

Authors: Sílvia Monserrate-Gómez, Lourdes Rubio-Rico, Roser Cuesta-Martínez, Rosa-Dolors Raventós-Torner, Alba Roca-Biosca, Inmaculada de Molina-Fernández

Summary: The current state of knowledge indicates that regular sports practice helps prevent and treat non-communicable diseases. The promotion of sport is, therefore, an important community health intervention for maintaining and improving the health of individuals and populations. Culture is identified as being associated with sports practice and sedentary behaviour of ethnic and national minorities. This study aims qualitatively to analyse the potential for culture as a basis for the promotion of sport among immigrants in four regions of Mediterranean Europe. Ten focus groups (n = 62) were conducted with immigrants-adults and young people over the age of 11-and people involved in promoting sport. Thematic content analysis was conducted. The results enabled identifying two major issues: sport as a vehicle for cultural expression and synergies between sport and culture. Accordingly, sport serves to express global, local and non-ethno-national cultural belonging. Regarding synergies, culture and sport feed each other positively and contribute to immigrants' health and cultural well-being. Culture as a strategy for promoting sports practice requires an interdisciplinary approach that involves collaboration between healthcare practitioners and social sciences professionals. There is also a need to use the various axes of cultural definition-global, local and non-ethno-national-of those involved, and for them to take part themselves in designing sports activities. Moreover, promoting sport through non-ethno-national axes of cultural definition may help with immigrants' social inclusion, as intercultural relations between migrants and newcomers are promoted.



#4 The England football team is better managed than the country's health policy

Reference: BMJ. 2022 Dec 7;379:o2953. doi: 10.1136/bmj.o2953.

Authors: Nason Maani, Martin McKee

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#5 Changes After a Conventional vs. an Alternative Therapy Program on Physical, Psychological, and Injury-Related Parameters in Male Youth Soccer Players With Patellar Tendinopathy During Return to Competition

Reference: J Strength Cond Res. 2023 Feb 7. doi: 10.1519/JSC.0000000000004467. Online ahead of print.

Authors: Marc Niering, Thomas Muehlbauer

Summary: Changes after a conventional (CON) vs. alternative (ALT) therapy program on physical, psychological, and injury-related or pain-related parameters in soccer players with patellar tendinopathy (PT) during return to competition were examined. Thirty-four male youth soccer players (15-16 years) with PT were randomly assigned to a CON (n = 18) or ALT (n = 16) program. The ALT program consisted of 60 minutes of balance training, eccentric and isometric exercises, static stretching, and a dual-task progression. The CON program consisted of 30 minutes of eccentric and isometric exercises and static stretching. Both programs were conducted until painlessness was reported during full training load. Assessments of muscle power (drop jump, jump and reach), change of direction speed (CODS) (acyclic sprint), speed (tapping, 30-m linear sprint), endurance (Yo-Yo intermittent recovery test level-1), the Achievement Motives Scale Sport, and injury-related or pain-related correlates were performed immediately, 6 weeks, 16 weeks, and 20 weeks after the respective therapy program. Players in the ALT group required a shorter program duration (ALT: 47.1 ± 15.6 days, CON: 58.2 ± 24.6 days) and achieved the same (muscle power, speed, endurance) or greater (CODS) improvements in physical performances, the same enhancements in psychological measures (achievement motives), and better values for injury-related or pain-related correlates (injury incidence, pain-related training interruptions). Results indicate that both programs effectively improve relevant outcome parameters in players with PT. The ALT therapy is more time efficient than the CON therapy. Therapists should consider this multimodal training program for effective treatment of athletes to shorten their return to competition time and minimize the risk of secondary injuries.



#6 The incidence of anterior cruciate ligament injury in youth and male soccer athletes: an evaluation of 17,108 players over two consecutive seasons with an age-based sub-analysis

Reference: Knee Surg Sports Traumatol Arthrosc. 2023 Feb 13. doi: 10.1007/s00167-023-07331-0.

Authors: Diego Costa Astur, Gabriel Furlan Margato, Alexandre Zobiole, Diego Pires, Luis Fernando Zucanovic Funchal, Andrew Esteban Jimenez, Eduardo Vasconcelos Freitas, Moises Cohen

Summary: The aim was to evaluate the incidence of anterior cruciate ligament (ACL) injuries in male athletes from professional soccer clubs over two consecutive seasons (2018-2019) with a sub-analysis based on age category: under-13 (U-13), under-15 (U-15), under-17 (U-17), and under-20 (U-20) years. A total of 17,108 young male soccer players were retrospectively reviewed from sixty-three professional clubs in the four highest Brazilian soccer divisions. Data regarding the number of athletes and the number of ACL injuries confirmed by magnetic resonance imaging (MRI) exams in the 2018 and 2019 seasons were collected. Incidence of ACL injury were compared by season, age category (under-13; under-15; under 17; and under-20), demographic region, and club division. Clubs from all regions of Brazil participated in the study. A total of 336 primary ACL injuries were diagnosed over the two seasons (8,167 athletes during the 2018 season and 8,941 athletes during the 2019 season) among all athletes, which corresponds to 2% of the included athletes. There were 11 cases (0.3%) in the under-13, 53 cases (1.3%) in the under-15, 107 cases (2.5%) in the under-17, and 165 cases (3.8%) in the under-20 age category. There was a higher incidence of ACL injury in the older age groups (p < 0.001). A total of 336 ACL injuries were identified in 17,108 youth soccer players from 63 professional clubs with an overall incidence of 2% over 2 seasons of competition. ACL injury rate ranged from 0.3% to 3.8% and was higher in the older and more competitive club divisions.



#7 Collagen supplementation augments changes in patellar tendon properties in female soccer players

Reference: Front Physiol. 2023 Jan 26;14:1089971. doi: 10.3389/fphys.2023.1089971. eCollection 2023.

Authors: Joonsung Lee, Josh E Bridge, David R Clark, Claire E Stewart, Robert M Erskine

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Summary: We investigated the effect of collagen hydrolysate supplementation on changes in patellar tendon (PT) properties after 10 weeks' training in female soccer players from a Football Association Women's Super League Under 21 s squad. We pair-matched n = 17 players (age: 17 ± 0.9 years; height: 1.66 ± 0.06 m; mass: 58.8 ± 8.1 kg) for baseline knee extension (KE) maximum isometric voluntary contraction (MIVC) torque, age, height, and body mass, and randomly assigned them to collagen (COL) or placebo (PLA) groups (COL n = 8, PLA n = 9). Participants consumed 30 g collagen hydrolysate supplementation or energy-matched PLA (36.5 g maltodextrin, 8.4 g fructose) and plus both groups consumed 500 mg vitamin C, after each training session, which comprised bodyweight strength-, plyometric- and/or pitch-based exercise 3 days/week for 10 weeks in-season. We assessed KE MIVC torque, vastus lateralis muscle thickness and PT properties using isokinetic dynamometry and ultrasonography before and after 10 weeks' soccer training. KE MIVC torque, muscle thickness and tendon cross-sectional area did not change after training in either group. However, COL increased PT stiffness [COL, +18.0 ± 12.2% (d = 1.11) vs. PLA, +5.1 ± 10.4% (d = 0.23), p = 0.049] and Young's modulus [COL, +17.3 ± 11.9% (d = 1.21) vs. PLA, +4.8 ± 10.3% (d = 0.23), p = 0.035] more than PLA. Thus, 10 weeks' in-season soccer training with COL increased PT mechanical and material properties more than soccer training alone in high-level female soccer players. Future studies should investigate if collagen hydrolysate supplementation can improve specific aspects of female soccer performance requiring rapid transference of force, and if it can help mitigate injury risk in this under-researched population.



#8 Movement retraining programme in young soccer and rugby football players: A feasibility and proof of concept study

Reference: J Bodyw Mov Ther. 2023 Jan;33:28-38. doi: 10.1016/j.jbmt.2022.09.017. Epub 2022 Sep 30.

Authors: Paolo Dainese, Nadine Booysen, Anna Mulasso, Mattia Roppolo, Maria Stokes

Summary: Movement screening to identify abnormal movement patterns can inform development of effective interventions. The primary objective of this study was to evaluate the feasibility of using a movement screening tool in combination with a tailored movement control retraining programme in young soccer and rugby football players. A secondary objective was to investigate changes in movement control patterns post-intervention, to provide proof of concept (PoC) for movement retraining. 52 male amateur players, including 34 soccer players (mean age 15 ± 2 years) and 18 rugby players (mean age 15 ± 1 years) participated. They were screened for movement control ability using a shortened version of the Hip and Lower Limb Movement Screening (Short-HLLMS) and completed an eight-week movement control retraining programme. Evaluation of feasibility included consent from players invited, adherence, attendance at the exercise sessions, drop-out and adverse events. Short-HLLMS total score and The Copenhagen Hip and Groin Outcome Score (HAGOS) were analysed to provide PoC for retraining movement control. Feasibility outcomes were favourable. Significant statistical changes occurred post-intervention in the Short-HLLMS total score (paired-samples t-test) and in three HAGOS subscales (symptoms, physical function in daily living and in sport and recreation) (Wilcoxon-Signed Rank Test) in both groups. Feasibility of using the Short-HLLMS in combination with a movement control retraining programme in soccer and rugby players was promising. The data provided PoC for the potential application of a shortened version of the HLLMS to evaluate changes in movement control and to inform targeted motor control programmes.



#9 Curcumin Attenuates Delayed-Onset Muscle Soreness and Muscle Function Deficits Following a Soccer Match in Male Professional Soccer Players

Reference: Int J Sports Physiol Perform. 2023 Jan 1;1-7. doi: 10.1123/ijspp.2022-0283. Online ahead of print.

Authors: William Abbott, Emily J Hansell, Adam Brett, Jakob Škarabot, Lewis J James, Tom Clifford

Summary: The aim was to examine the effects of acute curcumin (CURC) supplementation on recovery from a soccer match in male professional players. In a randomized, placebo-controlled, crossover design, 11 players from the under-23 team of an English Premier League club (age 19 [1] y, body mass 79.4 [7.9] kg, height 180.8 [5.7] cm) consumed 500 mg of CURC or a control (medium-chain triglycerides) immediately and 12 and 36 hours after a 90-minute match. Countermovement jump height (CMJ), reactive strength index (RSI), delayed-onset muscle soreness (DOMS, 0-200 mm), and subjective well-being were measured before and 12, 36, and 60 hours postmatch. Global positioning systems measured external load during matches, and dietary intake was recorded across the testing period. External load and dietary intake did not differ between conditions (P ≥ .246). CURC attenuated deficits in CMJ (P ≤ .004) and RSI (P ≤ .001) and reduced DOMS (P ≤ .004) at all postmatch time points (except 60 h post for RSI). The greatest difference between control and CURC was 12 hours post for CMJ (P < .001, 1.91 [4.40] cm, 95% CI, 1.25 to 2.57, g = 0.36) and RSI (P = .003, 0.40 [0.41] AU, 95% CI, 0.17 to 0.63, g = 0.90) and 36 hours post for DOMS (P < .001, 47 [23] mm, 95% CI, -67 to -27, g = 2.12). CURC intake <36 hours after a soccer match attenuated DOMS and muscle function deficits, suggesting that CURC may aid recovery in professional male soccer players.



#10 Adding A Structured Educational Session to the Rehabilitation Program of Soccer Players Following Anterior Cruciate Ligament Reconstruction: A Feasibility Study

Reference: Int J Sports Phys Ther. 2023 Feb 1;18(1):81-91. doi: 10.26603/001c.68141. eCollection 2023.

Authors: Abdullah Almuhaya, Ali Albarrati, Ahmed Alhowimel, Faris Alodaibi

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Summary: While a lack of psychological preparedness and fear of movement may be linked with the anterior cruciate ligament (ACL) re-injury, these variables are rarely addressed throughout the therapy stages via educational sessions. Unfortunately, in terms of reducing fear, increasing function, and returning to play, no research has been done yet on the efficacy of adding organized educational sessions to the rehabilitation programs of soccer players post-ACL reconstruction (ACLR). Therefore, the study's aim was to assess the feasibility and acceptability of adding organized educational sessions to the rehabilitation programs post-ACLR. A feasibility randomized controlled trial (RCT) was conducted in a specialized sports rehabilitation center. Participants post ACL reconstruction were randomized to either usual care with a structured educational session (intervention group) or usual care alone (control group). This feasibility study investigated three aspects: recruitment, intervention acceptability and randomization, and retention. The outcome measures included Tampa Scale of Kinesiophobia, ACL-Return to Sport after Injury, and International Knee Documentation Committee for knee function. Measurements were done at baseline and one week after the intervention. All of the 36 players who were undergoing rehabilitation post-ACLR at the center at the time of the study were invited to participate in the study. Thirty-five players (97.2%) agreed to participate in the study. The participants responded to some questions about the acceptability of the intervention and randomization and most of them thought they were appropriate. 30 (85.7%) participants completed the follow-up questionnaires one week after the randomization. This feasibility research found that adding a structured educational session to the rehabilitation program for soccer players after ACLR is feasible and acceptable. Full-scale RCTs with longer follow-ups and multiple locations are recommended.



#11 Sex Differences in Copper Concentrations during a Sports Season in Soccer Players

Reference: Nutrients. 2023 Jan 18;15(3):495. doi: 10.3390/nu15030495.

Authors: Víctor Toro-Román, Diego Muñoz, Marcos Maynar-Mariño, Sara Clemente-Gil, María C Robles-Gil

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Summary: Physical training produces changes in the concentrations of trace mineral elements. Sex differences in copper (Cu) concentrations in athletes are scarce. The objectives of this study were (i) to analyze changes in intracellular (erythrocytes and platelets) and extracellular (plasma and urine) Cu concentrations during a sports season in soccer players and (ii) to analyze sex differences. A total of 46 soccer players (22 men and 24 women) participated in the study. Three assessments were performed throughout the sports season. Anthropometry, body composition, nutritional intake, physical condition, female hormones (menstrual cycle) and hematology were evaluated, as well as Cu determination (plasma, urine, erythrocytes, and platelets). Regarding longitudinal differences, there were discrepancies in plasma, urine, absolute erythrocyte, and absolute platelet Cu concentrations (p < 0.05). There were differences between sexes in Cu concentrations in urine, erythrocytes relative to cell number and in platelets relative to cell number (p < 0.05). During a sports season, there are changes in Cu concentrations in soccer players. Likewise, there could be sex differences in urinary, erythrocyte and platelet Cu concentrations.



#12 Weekly variations of accelerometer variables and workload of professional soccer players from different positions throughout a season

Reference: Sci Rep. 2023 Feb 14;13(1):2625. doi: 10.1038/s41598-023-29793-5.

Authors: Hadi Nobari, Gibson Moreira Praça, Sarah da Glória Teles Bredt, Pablo Prieto González, Filipe Manuel Clemente, Jorge Carlos-Vivas, Luca Paolo Ardigò

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Summary: The current study aimed to analyze, using accelerometer-based activity, acute workload, chronic workload, acutechronic workloads ratio, training-monotony and training-strain throughout a competitive soccer-season and to compare these variables between players from different playing positions. Twenty-one professional soccer-players were monitored during the 48 weeks of the season. Players were grouped according to their position. Four lateral-defenders and four winger-players formed LDW group, four central-defenders and four forwards formed CDF group, and six midfielder-players formed MDF group. Accelerometer-based variables were collected during training and match contexts and were used to generate indicators of weekly acute and chronic workload, training monotony, training strain and metabolic power. A one-way ANOVA compared all dependent variables between groups, and effect sizes for pairwise comparisons were calculated. Results revealed variations in the weekly load throughout the season, which demands caution from coaches to avoid injuries. There were no differences in weekly-loads for all dependent variables (P > 0.05, small-to-moderate effects). We conclude that the weekly-load is not constant during a competitive season and players from different positions have similar weekly-loads. Therefore, previously reported in the literature, possible match-related positional differences might be compensated by differences in training-related loads, leading to a similar profile when considering the whole week.



#13 The Influence of Pitch Dimensions during Small-Sided Games to Reach Match Physical and Physiological Demands on the Youth Soccer Players

Reference: Sensors (Basel). 2023 Jan 23;23(3):1299. doi: 10.3390/s23031299.

Authors: Alfonso Castillo-Rodríguez, Álvaro Durán-Salas, Jesús Vicente Giménez, Wanesa Onetti-Onetti, Luis Suárez-Arrones

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Summary: The aims of this study were to (i) analyze the physical and physiological responses of four matches competition and (ii) to investigate the relationships among three different pitch dimensions of small-sided game (SSG) on the youth soccer players. Fifteen male U19 soccer players (age 17.3 ± 0.5 years, height 175.7 ± 5.6 cm, weight 68.5 ± 8.6 kg, playing experience 7.8 ± 1.4 years) were randomly assigned to three play areas: small (50 m2), medium (SSG-m, 150 m2) and large (SSG-l, 250 m2) area per player including goalkeeper. During the 4-week intervention, both groups performed three sets of 8 min with a passive rest period of 5 min between games. Differences in time-motion characteristics of players were measured with the Global Positioning System and assessed using a repeated measures ANOVA to compare the three game conditions and the magnitude-based inference to evaluate the pairwise comparison effects. The results showed that only the variables distance covered between 7.0-12.9 km·h-1 was not statistically significantly different among game conditions (p < 0.05; η = 0.21; small) and physiological response (i.e., hear rate of playing time spent 85-89% HRmax) also showed differences (p < 0.05; η = 0.25; small). The responses in SSG-m and SSG-l established them ass the format sizes ideal for replicating the physical responses during match competition. These findings could provide relevant information for coaches for use adequate pitch size (areas of 150 m2 and 250 m2) to reach the match-play scenarios found in match competition.



#14 Influence of Scoring Systems on Mental Fatigue, Physical Demands, and Tactical Behavior during Soccer Large-Sided Games

Reference: Int J Environ Res Public Health. 2023 Jan 23;20(3):2087. doi: 10.3390/ijerph20032087.

Authors: Jesús Díaz-García, José Carlos Ponce-Bordón, Abel Moreno-Gil, Ana Rubio-Morales, Miguel Ángel López-Gajardo, Tomás García-Calvo

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Summary: Constraints are common in soccer training to develop physical, technical-tactical, and mental training concurrently. This study examined how different scoring systems influence physical, tactical, and mental demands during large-sided games in soccer. Eighteen youth-elite male (17.39 ± 1.04 y) soccer players completed three 8 vs. 8 large-sided games where the different score systems were i) official score system (OSS; i.e., 1 goal = 1 goal), ii) double the value of the goal-4 min (DVx4; i.e., 1 goal = 1 goal from 0.00 to 7.59 min, and 1 goal = 2 goals from 8.00 to 12.00 min), and iii) double the value of the goal-8 min (DVx8; i.e., 1 goal = 1 goal from 0.00 to 3.59 min, and 1 goal = 2 goals from 4.00 to 12.00 min). Physical demands and tactical behaviors were recorded during tasks using a global positioning system and video camera. Mental fatigue was recorded pre- and post-task using a visual analogue scale. Also, the ratio of perceived exertion and mental load were recorded after tasks were finished. Results reported the highest values of mental and physical demands in DVx4. Mental fatigue increased during all three large-sided games, although this increase was significantly higher in DVx4 compared with OSS (p = 0.006) and DVx8 (p = 0.027). Tactical behavior showed a trend towards more direct play during DVx4, which was less observed during DVx8, and not at all during OSS. In conclusion, changing the scoring system affects physical, tactical, and mental demands.



#15 Age and Maturation Matter in Youth Elite Soccer, but Depending on Competitive Level and Gender

Reference: Int J Environ Res Public Health. 2023 Jan 21;20(3):2015. doi: 10.3390/ijerph20032015.

Authors: Honorato J Ginés, Florentino Huertas, Tomás García Calvo, Jose Carlos Ponce-Bordón, António J Figueiredo, Rafael Ballester

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Summary: This study aimed to explore the relevance of the relative age effect (RAE), maturity status and anthropometry, and their influence on coaches' assessment of players' performance, analyzing both genders and different types of academies (elite vs. non-elite). The sample included 603 soccer players (385 male), from the under 12 (U12), under 14 (U14) and under 16 (U16) categories, belonging to elite and nonelite teams. Coaches' assessment of players' performance, chronological age, anthropometric characteristics, maturity offset (MO) and peak height velocity (PHV) were registered. Our results showed that RAE was present in both genders within the elite, but not in the nonelite academies. Early maturity players were overrepresented in the male elite, but not in the female academies. No relationship was found between RAE and anthropometry in male elite academies. Male elite players showed better anthropometric characteristics than nonelite players, while this pattern of results was not found for female players. The coaches' assessment on players' current performance was not influenced by the chronological age nor anthropometry, but it was linked to the PHV. Coaches from nonelite academies rated better in current assessment of performance the taller players. Our findings suggest that maturity status and RAE play an independent and important role in the talent selection process.



#16 How Different Predominant SARS-CoV-2 Variants of Concern Affected Clinical Patterns and Performances of Infected Professional Players during Two Soccer Seasons: An Observational Study from Split, Croatia

Reference: Int J Environ Res Public Health. 2023 Jan 20;20(3):1950. doi: 10.3390/ijerph20031950.

Authors: Jasna Nincevic, Anamarija Jurcev-Savicevic, Sime Versic, Toni Modric, Ante Turic, Ante Bandalovic, Boris Becir, Marijana Mijakovic, Ivana Bocina, Damir Sekulic

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Summary: There are limited data describing clinical patterns and match running performance (MRP) among players with COVID-19 infection before and after infection, particularly related to different predominant SARS-CoV-2 variants, as well as in comparison to uninfected players. This observational study was conducted during two consecutive soccer seasons in one professional club in Split, Croatia. There were four clusters of mild, self-limited, or asymptomatic infection characterised by low adherence to preventive measures. Infected players had significantly more symptoms (t-test = 3.24; p = 0.002), a longer period of physical inactivity (χ2 = 10.000; p = 0.006) and a longer period of self-assessment for achieving full fitness (χ2 = 6.744; p = 0.034) in the 2020-2021 season (Wuhan wild strain and Alpha variant) than in the 2021-2022 season (Omicron variant). It was also found that, despite the milder clinical presentation of the infection in the 2021-2022 season, the players had significantly more abnormal laboratory findings (χ2 = 9.069240; p = 0.002), although without clinical significance at the time of the study. As for the MRP, player performance in the 2021-2022 season was not negatively affected by the Omicron variant, while there was an improvement in MRP in scores for a sample of all players. The RTP protocol was correctly applied because it helped the athletes to recover their pre-infection physical capacities relatively quickly. This study advances the understanding that an optimally and individually planned RTP protocol is crucial for the MRP of infected players. Future research needs to replicate the findings of abnormal laboratory results and extend the study focusing on their potential long-term clinical significance.



#17 Characterization of Static Strength, Vertical Jumping, and Isokinetic Strength in Soccer Players According to Age, Competitive Level, and Field Position

Reference: Int J Environ Res Public Health. 2023 Jan 18;20(3):1799. doi: 10.3390/ijerph20031799.

Authors: João Nuno Gouveia, Cíntia França, Francisco Martins, Ricardo Henriques, Marcelo de Maio Nascimento, Andreas Ihle, Hugo Sarmento, Krzysztof Przednowek, Diogo Martinho, Élvio Rúbio Gouveia

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Summary: Muscular strength is strongly related to speed and agility tasks, which have been described as the most decisive actions preceding goals in the soccer game. This study aimed to characterize the players' strength indicators and to analyze the variation associated with age, competition level, and positional role. Eighty-three male soccer players from A team (n = 22), B team (n = 17), U-23 (n = 19), and U-19 (n = 25) participated in this study. Handgrip strength was assessed using a hand dynamometer (Jamar Plus+), countermovement jump (CMJ) and the squat jump (SJ) were evaluated using Optojump Next, and a Biodex System 4 Pro Dynamometer was used to assess the isokinetic strength of knee extension/flexion. Team A players showed increased lower-body strength compared to their peers, mainly through their increased vertical jumping capacity (i.e., CMJ and SJ; ps < 0.019), and superior performance in isokinetic assessments (i.e., peak torque, total work, and average power). Overall, older players outperformed their younger peers regarding vertical jumping, static strength, and average power in isokinetic strength (ps < 0.005). This study emphasizes the superior strength levels of professional soccer players compared with their lower-division peers, even after controlling by age. This information is of great value to sports agents and coaches, underlining the need to design and include strength-specific content during soccer training.



#18 Epidemiology of Injuries in Amateur Male Soccer Players: A Prospective One-Year Study

Reference: Healthcare (Basel). 2023 Jan 25;11(3):352. doi: 10.3390/healthcare11030352.

Authors: Afxentios Kekelekis, Zoe Kounali, Nikolaos Kofotolis, Filipe Manuel Clemente, Eleftherios Kellis

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Summary: The purpose of this study was to prospectively monitor and analyze injuries in Greek amateur male soccer players over one competitive season. One hundred and thirty male soccer players in a regional amateur league participated in this study. Injury data and exposure were collected from six teams during training and competition match over one season (2018/19). Injuries were collected weekly and were classified by setting, mechanism, severity, type, calendar distribution, period of injury occurrence, and anatomical location. A total of 103 injuries were recorded during the season, with an incident rate (IR) of 5.5 injuries/1000 h with 95% confidence intervals (CI) values of 4.45 (lower limit) and 6.09 (upper limit). Furthermore, IR was greater for the posterior thigh (IR 1.83/1000 h, 95% CI 1.21-2.44) and hip/groin complex (IR 1.45/1000 h, 95% CI 0.90-1.99) compared to other anatomical locations. Similarly, muscle injuries had greater IR (IR 3.61/1000 h, 95% CI 2.74-4.47) than other tissues. Amateur soccer players had a seven-fold greater chance of getting injured during games (IR 20.76/1000 h, 95% CI 15.28-26.24) rather than during training (IR 3.077/1000 h, 95% CI 2.16-3.80), while injury rates were higher towards the end of a session and peaked in October and February of the season. Based on these results, amateur soccer may benefit from injury prevention strategies incorporated into their regular training practice and focus on muscle injuries, especially in the posterior thigh and the hip/groin complex.



#19 Use of Exploratory Factor Analysis to Assess the Fitness Performance of Youth Football Players

Reference: J Strength Cond Res. 2023 Feb 13. doi: 10.1519/JSC.0000000000004414. Online ahead of print.

Authors: Fabrizio Perroni, Carlo Castagna, Stefano Amatori, Erica Gobbi, Mario Vetrano, Vincenzo Visco, Laura Guidetti, Carlo Baldari, Marco Bruno Luigi Rocchi, Davide Sisti

Summary: Football performance involves several physical abilities that range in aerobic, anaerobic, and neuromuscular domains; however, little is known about their interplay in profiling individual physical attributes. This study aimed to profile physical performance in youth football players according to their training status. One hundred seven young male soccer players (age 13.5 ± 1.4 years; height 168 ± 7 cm; body mass 57.4 ± 9.6 kg; and body mass index 20.2 ± 2.1 kg·m-2) volunteered for this study. Players' physical performance was assessed with football-relevant field tests for sprinting (10 m sprint), vertical jump (countermovement jump), intermittent high-intensity endurance (Yo-Yo Intermittent Recovery Test Level 1, YYIRT1), and repeated sprint ability (RSA). The training status was assumed as testosterone and cortisol saliva concentrations; biological maturation was estimated using the Pubertal Development Scale. Exploratory factor analysis (EFA) revealed 3 main variables depicting anthropometric (D1, 24.9%), physical performance (D2, 18.8%), and training status (D3, 13.3%), accounting for 57.0% of total variance altogether. The level of significance was set at p ≤ 0.05. The RSA and YYIRT1 performances were largely associated with D2, suggesting the relevance of endurance in youth football. This study revealed that for youth football players, a 3-component model should be considered to evaluate youth soccer players. The EFA approach may help to disclose interindividual differences useful to talent identification and selection.



#20 Commentary: The impact of UEFA Euro 2020 football championship on Takotsubo Syndrome: Results of a multicenter national registry

Reference: Front Cardiovasc Med. 2023 Jan 26;10:1122436. doi: 10.3389/fcvm.2023.1122436. eCollection 2023.

Authors: Francesco Barone-Adesi

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#21 Predicting Injuries in Football Based on Data Collected from GPS-Based Wearable Sensors

Reference: Sensors (Basel). 2023 Jan 20;23(3):1227. doi: 10.3390/s23031227.

Authors: Tomasz Piłka, Bartłomiej Grzelak, Aleksandra Sadurska, Tomasz Górecki, Krzysztof Dyczkowski

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Summary: The growing intensity and frequency of matches in professional football leagues are related to the increasing physical player load. An incorrect training model results in over- or undertraining, which is related to a raised probability of an injury. This research focuses on predicting non-contact lower body injuries coming from over- or undertraining. The purpose of this analysis was to create decision-making models based on data collected during both training and match, which will enable the preparation of a tool to model the load and report the increased risk of injury for a given player in the upcoming microcycle. For this purpose, three decision-making methods were implemented. Rule-based and fuzzy rule-based methods were prepared based on expert understanding. As a machine learning baseline XGBoost algorithm was considered. Taking into account the dataset used containing parameters related to the external load of the player, it is possible to predict the risk of injury with a certain precision, depending on the method used. The most promising results were achieved by the machine learning method XGBoost algorithm (Precision 92.4%, Recall 96.5%, and F1-score 94.4%).



#22 The Assessment of Body Composition and Nutritional Awareness of Football Players According to Age

Reference: Nutrients. 2023 Jan 30;15(3):705. doi: 10.3390/nu15030705.

Authors: Wiktoria Staśkiewicz, Elżbieta Grochowska-Niedworok, Grzegorz Zydek, Mateusz Grajek, Karolina Krupa-Kotara, Agnieszka Białek-Dratwa, Sylwia Jaruga-Sękowska, Oskar Kowalski, Marek Kardas

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Summary: The optimal body composition for health is an individual trait and is determined by genetic factors, sex, age, somatotype, physical activity, and individual variability. The present study aims to assess how professional football players' body composition has changed over the training macrocycle in various age groups and to determine the correlation between nutritional awareness and body composition maintenance. Thirty-eight football players participated in the study, with 16 players classified in the younger age group (19-25) and 22 in the older age group (26-31). Using the direct segmented multi-frequency electrical impedance analysis technique, the athletes' body composition was assessed six times across a training macrocycle made up of preparatory, competitive, and transitional periods. The Sports Nutrition Knowledge Questionnaire was used to evaluate nutrition knowledge. The above correlations show that both younger and older athletes with higher awareness are better able to adjust their nutrition to meet the goals of the preparation period and can achieve greater gains in muscle mass and greater reductions in body fat. According to the study's results, athletes who are better conscious of their nutritional needs during competition experience less muscle loss and exhibit more consistent body weight and BMI levels. Football players' body composition suffers detrimental alterations throughout the transition period. Higher body mass, lean body mass content, and skeletal muscle mass are traits of older players. Higher nutritional knowledge reduces the negative modifications of body composition consisting of muscle mass reduction and fat gain. Nutritional knowledge influences the stability of body composition in both age groups during all the analyzed periods: Preparation, competition, and transition.



#23 The Evaluation of Asymmetry in Isokinetic and Electromyographic Activity (sEMG) of the Knee Flexor and Extensor Muscles in Football Players after ACL Rupture Reconstruction and in the Athletes following Mild Lower-Limb Injuries

Reference: J Clin Med. 2023 Feb 1;12(3):1144. doi: 10.3390/jcm12031144.

Authors: Łukasz Oleksy, Anna Mika, Iwona Sulowska-Daszyk, Renata Kielnar, Zofia Dzięcioł-Anikiej, Joanna Zyznawska, Olga Adamska, Artur Stolarczyk

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Summary: This study was aimed at evaluating knee stabilizer (quadriceps and hamstring) muscle strength and the medio-lateral symmetry of hamstring fatigue in football players after ACL reconstruction and with mild lower extremity injuries. The study comprised 65 professional football players who were divided into three groups: Group 1 (n = 24; 22.7 ± 3.6 years; 175 ± 4 cm; 77.3 ± 7.6 kg) after ACL reconstruction, Group 2 (n = 21; 20.5 ± 3.7 years; 177 ± 6 cm; 74.3 ± 9.1 kg) with mild lower-limb injuries (grade 1 muscle strains) and Group 3 (n = 20; 23.1 ± 2.8 years; 178 ± 6 cm; 75.8 ± 8.8 kg) without injuries in the past 3 years. The concentric isokinetic test (10 knee flexions and extensions at 60, 180 and 300°/s with a 30 s interval for rest) was performed on both limbs. Fatigue symmetry between the medial and lateral hamstrings was measured with sEMG during 60 s of isometric contractions. In comparison to the other groups, the injured leg demonstrated significantly lower values of peak torque for the quadriceps (G1-G2 = 48%, 38%, 14%; G1-G3 = 49%, 25%, 14%) and hamstring muscles (G1-G2 = 36%, 35%, 18%; G1-G3 = 64%, 28%, 17%) as well as lower values of hamstring muscle work (G1-G2 = 262 J, 157 J; G1-G3 = 219 J, 179 J) and power (G1-G2 = 34 W; 11 W; G1-G3 = 29 W, 12 W). No significant differences were noted in strength between Groups 2 and 3. The significantly higher fatigue of the BF compared to the SEM muscle was seen in Group 1 for the involved (mean difference = 0.12) and uninvolved limbs (mean difference = -0.10), but in Group 2, a non-significant trend towards asymmetry was also noted. No asymmetry in hamstring muscle fatigue was determined in Group 3. The results of our study allow us to indicate that active football players who previously met the RTS criteria, had deficits in lower-limb muscle performance 2-3 years after reconstruction, which could lead to ACL re-injury. This observation is potentially of importance because these deficits may not be subjectively reported by such athletes and also may not be visible in regular orthopedic and physiotherapeutic assessment.







An evidence-based approach to assessing the effectiveness of training regimen on athlete performance: Youth soccer as a case study

Athletic performance data are modeled in an effort to better understand the relationship between both hours spent training and a measurement of “commitment” to that training, and improvements in performance. Both increased training time and greater commitment were predicted to produce larger increases in performance improvement, and commitment was predicted to be the more important determinant of improvement.





Shortcomings of applying data science to improve professional football performance: Takeaways from a pilot intervention study

Existing research using tracking data has mostly focused on what occurred on the pitch, such as the determinants of effective passing. There have yet to be studies attempting to use findings from data science to improve performance.





Latest research in football - week 5 - 2023

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 High-Intensity Position-Specific Drills on Physical and Technical Skill Performance in Elite Youth Soccer Players

Reference: J Strength Cond Res. 2022 Nov 23. doi: 10.1519/JSC.0000000000004360. Online ahead of print.

Authors: Cao Cuong Le, Fadi Ma'ayah, Kazunori Nosaka, Daniel Hiscock, Christopher Latella

Summary: Soccer physical preparation has been extensively researched with previous emphasis on high-intensity interval running and small-sided games. However, neither approach considers positional differences. The purpose of this study was to investigate the feasibility and short-term effects of a novel position-specific conditioning training (PSCT) paradigm on physical and technical abilities of young soccer players. Fifteen male Vietnamese professional youth soccer players (16.1 ± 0.4 years, 171.7 ± 4.8 cm, 63.9 ± 3.8 kg) undertook a 3-week control period followed by a 3-week intervention with PSCT drills performed twice per week. Position-specific conditioning training comprised purposely designed drills for attackers, defenders, and wingers, respectively. The intensity and duration were the same for all drills (4 × 4 minutes at ∼90% heart rate maximum [HRmax], separated by a 4-minute recovery at 70% HRmax) but differed in the technical and tactical actions performed. Outcome measures included Yo-Yo intermittent recovery test level 1, repeated sprint ability, 10-m and 30-m sprint time, and the Loughborough Soccer Passing Test for technical skills in a fatigued and nonfatigued state. Position-specific conditioning training drills induced a desirable intensity for effective conditioning purpose (89.0 ± 2.1% HRmax) with low interplayer variability (coefficient of variation = 2.4%). Yo-Yo intermittent recovery test level 1 performance improved (p < 0.05) after the control (Δ178.7 ± 203.3 m) and intervention (Δ176.0 ± 225.7 m) periods without a difference between. These results confirmed the feasibility of PSCT as a novel high-intensity training approach for soccer players. Improvements in aerobic capacity were noted, despite no effect on other physical and technical measures. PSCT may be suitable for individual training, return-to-play stages of rehabilitation, during off-season, or in academy settings when time is not a constraint.



#2 Soccer clubs as avenues for gender transformative socialization of adolescent boys in Cape Town and Mthatha, South Africa: A qualitative study

Reference: PLoS One. 2023 Feb 2;18(2):e0280932. doi: 10.1371/journal.pone.0280932. eCollection 2023.

Authors: Yandisa Msimelelo Sikweyiya, Natalie Leon, Mark N Lurie, Mandla Majola, Christopher J Colvin

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Summary: In this paper, we explore the gender socialization of adolescent boys in soccer clubs, and ask whether there are opportunities for integrating gender transformative elements into that socialization. This qualitative study involved 11 in-depth interviews and informal conversations with male soccer coaches from Gugulethu township and Mthatha town in the Western Cape and Eastern Cape provinces of South Africa, respectively. Data were analyzed using a thematic analysis approach. We found that the coaches felt that the adolescent boys in their soccer clubs faced serious social and emotional challenges, with the boys' poor socio-economic backgrounds and fragmented family structures being major contributors to these challenges. Most coaches also gave themselves the responsibility to try to address some of the challenges faced by their club members. To do this, they employed specific strategies, including creating an alliance with parents and professionals. In the process, the coaches engaged the boys on topics around respect, sexual and reproductive health, and avoiding alcohol, drugs, and involvement in criminal gangs. Some coaches also played a social fathering role to club members as a way of helping them to think differently about their lives, redirect risky practices, and reduce the chance for poor health outcomes. These findings highlight the role of soccer clubs and coaches as potential avenues for health- and equity-promoting gender socialization of adolescent boys.



#3 Injury Burden in Professional European Football (Soccer): Systematic Review, Meta-Analysis, and Economic Considerations

Reference: Clin J Sport Med. 2022 Nov 22. doi: 10.1097/JSM.0000000000001107. Online ahead of print.

Authors: Luca Pulici, Denis Certa, Matteo Zago, Piero Volpi, Fabio Esposito

Summary: We performed a systematic review and meta-analysis to evaluate the injury burden and the related economic cost in European professional male football players. Multiple database research was performed up to August 5, 2022 (PubMed, EMbase, Scopus, Cochrane Library), including only studies that reported severity in the number of days of absence for each injury, incidence reported in the number of injuries/1000 hours, or reported number of injuries and exposure time and adult male football players, professionals from European clubs. Two reviewers extracted data and assessed paper quality with the Strengthening the Reporting of Observational Studies in Epidemiology statement and the Newcastle-Ottawa Scale. Twenty-two studies have reported incidence, severity, and burden of injuries in professional football. The highest injury burden was found for ligament-joint injuries (37.9 days/1000 hours; 222 397 €/1000 hours) and for muscle injuries (34.7 days/1000 hours; 203 620 €/1000 hours). Injury locations with high burden were knee injuries (34.8 days/1000 hours; 20 4206 €/1000 hours)-mainly anterior cruciate ligament injuries (14.4 days/1000 hours; 84 499 €/1000 h)-followed by thigh injuries (25.0 days/1000 hours; 146 700 €/1000 hours), hamstrings injuries (15.4 days/1000 hours; 90 367 €/1000 hours), hip-and-groin injuries (16.1 days/1000 hours; 94 475 €/1000 hours), primarily adductor muscles injuries (9.4 days/1000 hours; 55 159€/1000 hours), and ankle injuries (13.1 days/1000 h; 76 871 €/1000 hours) with ankle sprains (7.4 days/1000 hours; 43 423 €/1000 hours). Being exposed to injury risk has serious consequences for individual and club performance and economy. This review identified the most relevant targets in injury management, compared their injury data with reference values, and provided economic evidence when trying to gain buy-in from the key decision makers.



#4 Interrelationships Between Multiple Speed Tests in Youth Soccer: Are Players Equally Efficient at Performing Different Sprint and Change of Direction Tasks?

Reference: J Strength Cond Res. 2022 Nov 14. doi: 10.1519/JSC.0000000000004341. Online ahead of print.

Authors: Tomás T Freitas, Lucas A Pereira, Pedro E Alcaraz, Eduardo L Cadore, Rafael Grazioli, Paulo H S M Azevedo, Ian Jeffreys, Irineu Loturco

Summary: We investigated the relationships between linear and multidirectional sprint tests in elite young soccer players, using different speed measurements and their associated deficits. Twenty-three under-17 and 17 under-16 soccer players performed, on the same day, 17-m linear sprint (with 10-m split times), curve sprints for "good" and "weak" sides (CSGS and CSWS, respectively), and zigzag and 505 change of direction (COD) tests. The Pearson's product moment test was used to determine the relationships among the tested variables. Significance level was set at p < 0.05. Large and very large significant correlations were observed between CSGS and CSWS and 10-m (r = 0.73 and r = 0.53, respectively; p < 0.0001) and 17-m sprint velocity (r = 0.84 and r = 0.74, respectively; p < 0.0001). Moderate and significant associations were identified between zigzag and 17-m sprint performances (r = 0.40; p = 0.02). No significant relationships were found between 505 performance and 17-m sprint velocity and between the different COD tasks (p > 0.05). Significant correlations were observed between sprint performance at 10- and 17-m and both CS and COD deficits (r values ranging from 0.37 to 0.54; p < 0.05). In general, higher linear sprinting velocities were associated with superior performances in smoother multidirectional tasks (i.e., CS and zigzag tests) but not in more aggressive COD maneuvers (i.e., 505). Faster athletes in linear actions presented greater CS and COD deficits. No associations were detected between the different COD measurements, supporting the notion that the technical and mechanical demands of COD actions are angle and velocity dependent. From a practical perspective, comprehensive speed testing batteries (i.e., incorporating linear sprints, CS, and different COD assessments) should be administered to young soccer players, to better understand their ability to change direction and sprint over multiple trajectories.



#5 Predicting Severity of Head Collision Events in Elite Soccer Using Preinjury Data: A Machine Learning Approach

Reference: Clin J Sport Med. 2022 Nov 4. doi: 10.1097/JSM.0000000000001087. Online ahead of print.

Authors: Gabriel Tarzi, Christopher Tarzi, Ashirbani Saha, Michael D Cusimano

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Summary: The aim was to develop machine learning (ML) models that predict severity of head collision events (HCEs) based on preinjury variables and to investigate which variables are important to predicting severity. Data on HCEs were collected with respect to severity and 23 preinjury variables to create 2 datasets, a male dataset using men's tournaments and mixed dataset using men's and women's tournaments, to perform ML analysis. Machine learning analysis used a random forest classifier based on preinjury variables to predict HCE severity. Elite athletes participating in analyzed tournaments were investigated with 23 preinjury variables collected for each HCE. Predictive ability of the ML models and association of important variables was used as main outcome measure. The ML models had an average area under the receiver operating characteristic curve for predicting HCE severity of 0.73 and 0.70 for the male and mixed datasets, respectively. The most important variables for prediction were the mechanism of injury and the event before injury. In the male dataset, the mechanisms "head-to-head" and "knee-to-head" were together significantly associated (P = 0.0244) with severity; they were not significant in the mixed dataset (P = 0.1113). In both datasets, the events "corner kicks" and "throw-ins" were together significantly associated with severity (male, P = 0.0001; mixed, P = 0.0004). ML models accurately predicted the severity of HCE. The mechanism and event preceding injury were most important for predicting severity of HCEs. These findings support the use of ML to inform preventative measures that will mitigate the impact of these preinjury factors on player health.



#6 Does Prematch Neuromuscular Performance Affect Running Performance in Collegiate Elite Female Soccer?

Reference: J Strength Cond Res. 2022 Oct 18. doi: 10.1519/JSC.0000000000004344. Online ahead of print.

Authors: Ai Ishida, Garrison Draper, Jason B White, S Kyle Travis

Summary: The purpose of this study was to investigate whether prematch neuromuscular performance affected match physical performance by player position in Division I collegiate female soccer. Fourteen players participated (20.7 ± 1.3 years; 165.1 ± 6.0 cm; 63.3 ± 7.0 kg) in this study. Players were selected based on being free from injuries, playing for a duration of ≥72 minutes, and match intervals were ≥2 days. Data included 73 observations (n = 5 defenders, n = 7 midfielders, and n = 2 forward) from 14 official matches. Prematch neuromuscular performance was assessed using countermovement jump (CMJ) with polyvinyl chloride pipe on dual force plates. Countermovement jump variables included jump height (JH) and relative peak power (RPP). Match physical performance included average speed, high-speed running (HSR), and number of high accelerations and decelerations. Linear mixed model was compiled with fixed effects of loaded with fixed effect of JH, RPP, and position and random effects per individual player. In CMJ and player position model, RPP was a significant predictor for average HSR (p = 0.003) while fixed effects of JH and position were not significant (p = 0.15-0.86). The fixed and random effects explained 34.8 and 42.1% of variances in average HSR. In CMJ-only model, RPP significantly predicted the variances in average HSR (p = 0.001). The fixed effects and random effects of the model explained 22.7 and 51.8% of the variance in average HSR. However, position-only was not a significant predictor for average HSR in the position-only model (p = 0.26 and 0.33). Prematch CMJ RPP may be the greatest predictor of average HSR in collegiate female soccer.



#7 Relationships between training load, peak height velocity, muscle soreness and fatigue status in elite-level young soccer players: a competition season study

Reference: BMC Pediatr. 2023 Feb 3;23(1):55. doi: 10.1186/s12887-023-03869-7.

Authors: Hadi Nobari, Özgür Eken, Okan Kamiş, Rafael Oliveira, Pablo Prieto González, Rodrigo Aquino

Summary: This study aimed to compare training load parameters, delayed onset muscle soreness (DOMS), and fatigue status between season periods (1st and 2nd halves) in U14 soccer players and to analyze the relationships between training load parameters based on season periods (1st and 2nd halves) with peak height velocity (PHV), DOMS, and fatigue status in under-14 (U14) young elite soccer players. Additionally, it was intended to analyze if fatigue, DOMS and PHV could explain training load parameters across the season. Twenty U14 players that competed in the national league participated in this study. The players were monitored during the whole season (26 weeks), and evaluations were carried out at the end of the in-season. Anthropometric and body composition parameters and the maturity offset of each player were utilized to compute each player's age at PHV. Players reported their levels of DOMS and fatigue status using Hooper index questionnaires. The internal load was monitored using the rating of perceived exertion (RPE). Acute weekly internal load (AW), chronic weekly internal load (CW), acute: chronic workload ratio (ACWR), training monotony (TM), and training strain (TS) were also obtained. The main results showed that TM was higher in the 2nd half, while CW, AW and DOMS were higher in the 1st half of the season. Moreover, the main correlations showed a positive correlation between PHV and TS (2nd half of the season) and between fatigue and TM (1st half of the season). In conclusion, variations in well-being status and PHV cannot explain the variations in internal training loads in elite U14 soccer players. In addition, internal training load indices during the first half of the competitive season can promote a fundamental base for progression loads during the second period of the competitive season.



#8 Mechanisms of Hamstring Injury in Professional Soccer Players: Video Analysis and Magnetic Resonance Imaging Findings

Reference: Clin J Sport Med. 2022 Nov 25. doi: 10.1097/JSM.0000000000001109. Online ahead of print.

Authors: Aleksi Jokela, Xavier Valle, Jussi Kosola, Gil Rodas, Lluís Til, Maria Burova, Pavel Pleshkov, Håkan Andersson, Giulio Pasta, Paolo Manetti, Gabriel Lupón, Ricard Pruna, Alvaro García-Romero-Pérez, Lasse Lempainen

Summary: The aim was to describe the injury mechanisms and magnetic resonance imaging (MRI) findings in acute hamstring injuries of male soccer players using a systematic video analysis. Descriptive case series study of consecutive acute hamstring injuries from September 2017 to January 2022. Professional male soccer players aged between 18 and 40 years, referred for injury assessment within 7 days after an acute hamstring injury, with an available video footage of the injury and positive finding on MRI. Hamstring injury mechanisms (specific scoring based on standardized models) in relation to hamstring muscle injury MRI findings were used as independent variables and Hamstring injury mechanism (playing situation, player/opponent behavior, movement, and biomechanical body positions) and MRI injury location as main outcome measures. Fourteen videos of acute hamstring injuries in 13 professional male soccer players were analyzed. Three different injury mechanisms were seen: mixed-type (both sprint-related and stretch-related, 43%), stretch-type (36%), and sprint-type (21%). Most common actions during injury moments were change of direction (29%), kicking (29%), and running (21%). Most injuries occurred at high or very high horizontal speed (71%) and affected isolated proximal biceps femoris (BF) (36%). Most frequent body positions at defined injury moments were neutral trunk (43%), hip flexion 45-90 degrees (57%), and knee flexion <45 degrees (93%). Magnetic resonance imaging findings showed that 79% were isolated single-tendon injuries. According to a video analysis, most hamstring injuries in soccer occur during high-speed movements. Physicians should suspect proximal and isolated single-tendon-most often BF-hamstring injury, if represented injury mechanisms are seen during game play. In addition to sprinting and stretching, also mixed-type injury mechanisms occur.



#9 Power, Endurance, and Body Composition Changes Over a Collegiate Career in National Collegiate Athletic Association Division I Women Soccer Athletes

Reference: J Strength Cond Res. 2023 Jan 18.  doi: 10.1519/JSC.0000000000004413. Online ahead of print.

Authors: Bridget A McFadden, Brittany N Bozzini, Harry P Cintineo, Samuel P Hills, Alan J Walker, Alexa J Chandler, David J Sanders, Mark Russell, Shawn M Arent

Summary: The purpose of this study was to determine longitudinal changes in fitness and body composition throughout athletes' 4-year collegiate soccer careers. Performance testing occurred before preseason during freshman, sophomore, junior, and senior year in 17 female Division I soccer players. Body composition was assessed through air-displacement plethysmography to determine percent body fat (%BF), fat-free mass (FFM), and body mass (BM). Maximal countermovement vertical jump height was assessed through contact mat using arm swing (CMJAS) and hands-on-hips (CMJHOH) methods to calculate power (CMJwatts/HOHwatts). Aerobic capacity (V̇o2max) and ventilatory threshold (VT) were assessed by indirect calorimetry during a maximal graded exercise test on a treadmill. Linear mixed models were used to assess changes across academic years (p < 0.05). No changes occurred in %BF, BM, V̇o2max, VT, CMJAS, or CMJwatts. A time main effect was seen for FFM (p = 0.01) with increases from freshman to senior (p = 0.02). Time main effects were observed for CMJHOH (p < 0.001) and CMJHOHwatts (p < 0.001) with increases from freshman to junior (CMJHOH,p = 0.001; CMJHOHwatts, p = 0.02) and senior (CMJHOH, p < 0.001; CMJHOHwatts, p = 0.003) as well as sophomore to senior (CMJHOH, p < 0.001; CMJHOHwatts, p = 0.02). Countermovement vertical jump with hands on hips also increased from sophomore to junior (p = 0.005). The lower FFM and power capabilities as freshmen compared with upperclassman indicate a potential limited readiness. Coaches and training staff should account for these developmental differences when entering the preseason. Adequate conditioning programs before starting a collegiate program may help build a fitness foundation and prepare freshmen athletes to compete at the same level as their upperclassmen counterparts.



#10 Sprint and Jump Training on Sand vs. Grass Surfaces: Effects on the Physical Performance of Young Soccer Players

Reference: J Strength Cond Res. 2023 Feb 1. doi: 10.1519/JSC.0000000000004472. Online ahead of print.

Authors: Lucas A Pereira, Tomás T Freitas, Santiago Zabaloy, Ricardo C A Ferreira, Matheus L Silva, Paulo H S M Azevedo, Irineu Loturco

Summary: The aims of this study were to (a) examine the effects of a 6-week sand training program including both sprint and jump exercises on the speed-related and vertical jump performance of elite young soccer players and (b) compare the changes induced by a sand training scheme with those induced by a similar training program (in volume, intensity, and exercise types) performed on grass. Twenty-four under-20 soccer players were randomly allocated to 2 training groups, as follows: "sand" (n = 12) or "grass" (n = 12) groups. Athletes performed squat and countermovement jumps, linear sprints, and Zigzag change-of-direction speed tests at pre-, mid- (after 6 training sessions), and postintervention (after 12 training sessions). Both groups exhibited similar increases in the vertical jump and Zigzag performance after the 6-week training period (p values ranging from 0.0001 to 0.025; effect size ranging from 1.05 to 3.78, for main effect of time). No significant changes were detected for the linear sprint velocity for both the groups (p values ranging from 0.079 to 1.00; effect size ranging from 0.07 to 0.65, for main effect of time). In summary, training on sand or grass surfaces resulted in similar improvements in the physical performance of elite young soccer players. This study confirms the current evidence on the effectiveness of both soft and harder training surfaces in improving the sprint and jump performance of team-sport athletes.



#11 Pain provocation tests and clinical entities in male football players with longstanding groin pain are associated with pain intensity and disability

Reference: Musculoskelet Sci Pract. 2023 Jan 10;63:102719. doi: 10.1016/j.msksp.2023.102719.

Authors: Mathias F Nielsen, Lasse Ishøi, Carsten Juhl, Per Hölmich, Kristian Thorborg

Summary: Clinical examination of male football players with longstanding groin pain can be considered difficult. Pain provocation tests are used to examine and classify longstanding groin pain into clinical entities as adductor-, iliopsoas-, inguinal-, and pubic-related. It is unknown if pain provocation tests and clinical entities are associated with pain intensity and disability. The aim was to investigate if the number of positive pain provocation tests and clinical entities are associated with pain intensity and disability, measured by the Copenhagen 5-Second Squeeze Test (5SST) and the Copenhagen Hip and Groin Outcome Score (HAGOS), respectively. Forty male football players (age: mean 24 years [SD: 3.2]; height: mean 182 cm [SD: 5.7]; weight: mean 78 Kg [SD: 6.6]) with longstanding groin pain for a median of 8.5 months (IQR: 4-36) were included. The players underwent a bilateral groin examination with 33 pain provocation tests and were classified with clinical entities (0-7) based on the test findings. The number of positive pain provocation tests (median 10, range 2-23) correlated with pain intensity (5SST: rs = 0.70 [95% CI: 0.50, 0.83]) and disability (HAGOS subscales Sport: rs =-0.62 [95% CI: -0.81, -0.36], Pain: rs = -0.38 [95% CI: -0.69, -0.06], Symptoms: rs = 0.52 [95% CI: -0.73, -0.24], ADL: rs = -0.48 [95% CI: -0.71, -0.18]). The number of clinical entities (median 3, range: 1-7) showed similar but weaker correlations to pain intensity and disability. In male football players with longstanding groin pain, the number of positive pain provocation tests and clinical entities shows weak to strong correlations with pain intensity and disability. Consequently, when pain intensity and disability are severe, a higher number of pain provocation tests may be positive, and more clinical entities may be present.



#12 Adjusting to Changing Environments: Virtual Preseason SCAT5 Assessment in Canadian Male Youth Football Players

Reference: Clin J Sport Med. 2022 Nov 8. doi: 10.1097/JSM.0000000000001086. Online ahead of print.

Authors: Reid A Syrydiuk, Linden C Penner, Stacy Sick, Paul Eliason, Jean-Michel Galarneau, Benjamin Leggett, Olivia Galea, Kathryn J Schneider, Carolyn A Emery

Summary: The aim was to provide preseason reference scores for Canadian youth tackle football players on the Sport Concussion Assessment Tool 5 (SCAT5) and to examine whether age, concussion history, and self-reported medical diagnoses are associated with SCAT5 subcomponent performance. Five hundred one male youth football players (ages 13-18 years) participated in the 2021 season. SCAT5 subcomponents were assessed by age group (13-14, 15-16, 17-18), concussion history (0, 1, 2+, and yes/no), and self-reported diagnoses (headache disorder, attention-deficit/hyperactive disorder, learning disability/dyslexia, and depression, anxiety, or other psychiatric disorder). Virtual video administration (vs traditional in-person testing) of the SCAT5 was completed, and subcomponent scores included total number of symptoms (/22), symptom-severity score (/132), Standardized Assessment of Concussion [orientation (/5), immediate memory (/30), concentration (/5), delayed recall (/10)], and modified Balance Error Scoring System (/30). Kruskal-Wallis, one-way analysis of variance , Mann-Whitney U, or independent t tests were used to assess possible associations depending on number of groups and data normality. Virtual SCAT5 assessment scores across all outcomes did not differ by age group or concussion history. The median number of symptoms and median symptom-severity score at baseline was 2, and 173 players (34.5%) reported no symptoms. Median total number of errors on the modified Balance Error Scoring System was 3. Participants with certain self-reported diagnoses (attention-deficit/hyperactive disorder, dyslexia) demonstrated poorer performance on some SCAT5 subcomponents (symptom reporting, Standardized Assessment of Concussion). Baseline SCAT5 performance did not differ by age group or concussion history in male youth football players. Diagnoses of the self-reported disorders examined may be important considerations for interpretation of the SCAT5 assessment.



#13 Bilateral Ischial Tuberosity Stress Fractures in an Adolescent Football Player: A Case Report

Reference: Clin J Sport Med. 2022 Dec 6. doi: 10.1097/JSM.0000000000001103. Online ahead of print.

Authors: Jared M Jones, Grant M Wallenfelsz, Phillip R Worts, Andrew M Wong

Summary: Pelvic stress fractures are rare, making up an estimated 1% to 7% of all stress fractures with the primary locations being the pubic rami, pubic symphysis, and sacrum. Two cases of stress fractures of the ischium have been previously described in the literature, with both occurring in the ischial body. In this case, a 17-year-old high school American football player presented with nonspecific pelvic pain and bilateral point tenderness on deep palpation of the ischial tuberosities. Advanced imaging identified bilateral ischial tuberosity stress fractures. This report outlines the diagnosis and management of the first reported case of bilateral ischial tuberosity stress fractures. We report how ischial tuberosity stress fractures present clinically, potential management strategies, and highlight the use of computed tomography imaging for pelvic stress fractures. Knowledge of unusual stress fracture locations may improve early diagnosis, limit complications, reduce healthcare costs, and promote an accelerated recovery time.



#14 Health football beats them all: subgroup analysis of the 3F (Fit&Fun with Football) study on white coat hypertension, sustained hypertension, dippers, nondippers, and on pharmacologically un(treated) arterial hypertension

Reference: J Hypertens. 2022 Dec 19. doi: 10.1097/HJH.0000000000003360. Online ahead of print.

Authors: Bastian Schrader, Charis Conradi, Stephan Lüders, Bernhardt Vaske, Martin Koziolek, Eugen Gehlenborg, Hermann Haller, Albrecht Elsässer, Joachim Schrader

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Summary: The 3F study (Fit&Fun with Football) demonstrated a significant reduction in blood pressure, antihypertensive medication, body weight, stress and depression through health football. Health football could be a popular tool to unleash the full preventive potential of physical activity. This work analyses the effect of health football on hypertensive subgroups dipper, nondipper, white coat hypertension (WCH), sustained hypertension, (un)treated hypertensive patients (UH, TH). A prospective interventional study with 1-year follow-up. Football group (FG): n = 103, 'health'-football training (1×/week, 90 min) led by licensed football coaches. Physical inactive, hypertensive patients older than 45 years were compared with a control group (CG) (n = 105). Subgroups were divided by ambulatory blood pressure monitoring (ABPM), casual blood pressure (CBP), medication schedule and compared by blood pressure (BP), laboratory results and weight. In all three subgroups (WCH vs. sustained hypertension, TH vs. UH, D vs. ND), health football reduced BP and weight significantly compared with the CG, and compared with the admission. An even greater effect in CBP was found in people with WCH than in sustained hypertension (FG: WCH: 141-127 mmHg, sustained Hypertension (SH): 142-132 mmHg; CG: WCH: 141-143 mmHg, SH: 140-141 mmHg). In contrast, the significant reduction in CBP and ABPM was comparable in treated and untreated patients, although antihypertensive drugs were reduced significantly more frequently in FG than in CG. BP reduction in nondippers and dippers was also comparable. In the nondipper group, nocturnal BP was significantly reduced in the FB (122.0-111.5 mmHg), but not in the CG or the dippers. All evaluated football subgroups achieved a significant BP reduction (compared with CG). This applied to dipper, nondipper, (un)treated hypertension, WCH and SH. All mentioned subgroups displayed a clear benefit. The even greater reduction in BP in WCH demonstrates the importance of physical activity before the additional prescription of antihypertensive medications, underscoring the recommendations of the ESC and ISH in WCH.



#15 Risk factors for hamstring muscle injury in male elite football: medical expert experience and conclusions from 15 European Champions League clubs

Reference: BMJ Open Sport Exerc Med. 2023 Jan 24;9(1):e001461. doi: 10.1136/bmjsem-2022-001461. eCollection 2023.

Authors: Jan Ekstrand, Peter Ueblacker, Wart Van Zoest, Raymond Verheijen, Bruno Vanhecke, Maikel van Wijk, Håkan Bengtsson

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Summary: The aim was to describe the perceived importance of suggested hamstring injury risk factors according to chief medical officers (CMOs) of European male professional football clubs. A secondary objective was to compare if these perceptions differed between teams with a lower-than-average hamstring injury burden and teams with a higher than average hamstring injury burden. First, CMOs of 15 European professional male football clubs were asked to suggest risk factors for hamstring injury in their club. The perceived importance of the suggested risk factors was then rated by all participants on a 5-graded Likert scale. Participating teams were divided in two groups depending on their hamstring injury burden during the 2019/2020 and 2020/2021 seasons. The LOW group consisted of seven teams that had a lower than average hamstring injury burden. The HIGH group consisted of eight teams that had a higher-than-average hamstring injury burden. Twenty-one risk factors were suggested. The majority were extrinsic in nature, associated with coaching staff, team or club rather than players themselves. 'Lack of communication between medical staff and coaching staff' had the highest average importance (weighted average=3.7) followed by 'Lack of regular exposure to high-speed football during training sessions' (weighted average=3.6). The HIGH group perceived the player factors fatigue and wellness as more important than the LOW group. According to CMOs recruited in this study, most risk factors for hamstring injuries are extrinsic and associated with the club and coaching staff, and not the players themselves.



#16 Variations in cumulative workload and anaerobic power in adolescent elite male football players: associations with biological maturation

Reference: BMC Sports Sci Med Rehabil. 2023 Jan 31;15(1):11. doi: 10.1186/s13102-023-00623-5.

Authors: Hadi Nobari, Armin Gorouhi, Javier Mallo, Demetrio Lozano, Pablo Prieto-González, Elena Mainer-Pardos

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Summary: It is considered that the maturity condition of young football players is related to their physical performance during short high-intensity efforts dependent on anaerobic power ability. Hence, the aim was to determine possible relationships between maturity status and training intensity by measuring the footballer´s peak height velocity (PHV), maturity offset and anaerobic power. Seventeen youth male players of different playing positions participated in the study and performed tests at three different stages of the season (early-, mid- and end-season) All the anthropometric parameters and biomarkers related to maturation were controlled during the season. The training intensity and load was monitored and the anaerobic power of the players was assessed by a running-based anaerobic sprint test (RAST). The analysis of all the recorded data revealed a positive relationship between PHV and anaerobic power in the early- and end-season stages (p < 0.05). Maturity offset and anaerobic power (mean RAST) showed an absolute correlation in early- and end -season stages (r: - 0.39 to 0.91). The multiple linear regression analysis revealed that min RAST was the best predictor for both PHV and maturity offset. The analysis of the training intensity and workloads showed a positive effect on the performance in the fitness test (p < 0.05). Additionally, players experienced less fatigue at the end-season stage than at the early-season. The results show that coaches might benefit from monitoring training loads and the maturity status of the players in order to enhance their physical performance during the season.



#17 Sensitivity of rapid antigen tests for COVID-19 during the Omicron variant outbreak among players and staff members of the Japan Professional Football League and clubs: a retrospective observational study

Reference: BMJ Open. 2023 Jan 30;13(1):e067591. doi: 10.1136/bmjopen-2022-067591.

Authors: Michio Murakami, Hitoshi Sato, Tomoko Irie, Masashi Kamo, Wataru Naito, Tetsuo Yasutaka, Seiya Imoto

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Summary: Rapid antigen tests have been used to prevent the spread of the COVID-19; however, there have been concerns about their decreased sensitivity to the Omicron variant. In this study, we assessed the sensitivity and specificity of the rapid antigen test compared with the PCR test among the players and staff members of the Japan Professional Football League and clubs. Furthermore, we evaluated the relationship between the sensitivity and the duration from the onset of symptoms to testing or vaccine status. We used 656 results from both the rapid antigen and PCR tests for COVID-19 using samples collected on the same day from 12 January to 2 March 2022, during the Omicron variant outbreak in Japan. The sensitivity of the rapid antigen test compared with the PCR test was 0.63 (95% CI: 0.53 to 0.73) and the specificity was 0.998 (95% CI: 0.995 to 1.000). There were no significant associations between the sensitivity and the duration from the onset of symptoms to testing (including asymptomatic cases in the category) or vaccination status (p>0.05) with small effect sizes (Cramer's V or φ: ≤0.22). Even during the Omicron outbreak, the sensitivity of the rapid antigen tests did not depend on the duration from the onset of symptoms to testing.



#18 Match performance of football teams in different competition phases: Analysis on the data of eight consecutive seasons in the Chinese Super League

Reference: Front Psychol. 2023 Jan 11;13:1069082. doi: 10.3389/fpsyg.2022.1069082. eCollection 2022.

Authors: Pei Li, Shisheng Zhong, Paweł Chmura, Hongyou Liu

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Summary: The study aims to quantify the variation in the physical and technical match performance of football teams in different months of a season in the Chinese Super League (CSL). Data of 1,899 matches in the seasons 2012-2019 of CSL collected by Amisco Pro® were analysed. The generalised mixed modelling was employed to estimate the per match mean values of six physical performance-related parameters and 16 technical performance-related parameters of CSL teams in every month of all the eight seasons. Results showed that: (1) the mean values of all the analysed physical performance-related parameters (total/sprint/HSR/MSR distance, sprint/HSR efforts) of CSL teams through a season were characterised like a 'U' shape, the highest value was observed in the beginning of season (March), then decreased gradually, reaching the lowest in August, and rebounded progressively from September to November; (2) the mean values of eight technical performance-related parameters (goals, shots, shot accuracy, individual possession, individual possession in the last third, crosses, cross accuracy and yellow cards) presented trivial changes through the whole season; (3) the number of passes, passes per shot, forward passes, and time in individual possession showed trivial changes from March to October, but showed a substantially increase in November (the last month of season); (4) Pass accuracy, forward pass accuracy, and the number of mean ball touches per individual possession substantially increased in June, July and August, whilst the number of challenges, ground challenges, air challenges, tackles and fouls all substantially decreased in these 3 months. These results could provide detailed information to help the practitioners choose the best training and match preparation strategy in the means of periodisation in different season phases.






Decline in Running Performance in Highest-Level Soccer: Analysis of the UEFA Champions League Matches

This study aimed to examine match running performance across 15-min match periods for players on different playing positions.





Biochemical and Physical Performance Responses to a Soccer Match after a 72-Hour Recovery Period

The aims of this study was to determine the biochemical and physical performance responses to a soccer match after a 72-h recovery period.





Latest research in football - week 4 - 2023

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 Level of Selected Blood Parameters in Young Soccer Players in Relation to the Concentration of 25(OH)D at the Beginning and End of Autumn

Reference: Biology (Basel). 2023 Jan 13;12(1):129. doi: 10.3390/biology12010129.

Authors: Joanna Jastrzębska, Maria Skalska, Łukasz Radzimiński, Guillermo F López Sánchez, Katja Weiss, Beat Knechtle

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Summary: This study aimed to demonstrate the changes of selected blood parameters in relation to 25(OH)D concentration during the autumn period in young soccer players. A total of 35 participants' results (age: 17.5 ± 0.6 years, body mass 71.3 ± 6.9 kg) were tested twice: in mid-September and in mid-December and divided into subgroups with regard to two criteria. First, according to the initial level of the 25(OH)D concentration (optimal group-ODG, suboptimal group-SDG), second, according to drops in 25(OH)D concentration (high drop group-HDG, low drop group-LDG). A significant decrease (p &lt; 0.001) in the 25(OH)D concentration was reported in the total group (TGr) and in all subgroups. Blood parameters such as white blood cells, red blood cells, haemoglobin and haematocrit increased significantly (p &lt; 0.05) in TGr during the analysed period of time. The analysis of changes in the lipid profile did not expose significant differences except triglycerides. The asparagine amino transferase and creatine kinase activity decreased significantly after autumn in all analysed groups. The declining level of 25(OH)D concentration should be compensated (e.g., with vitamin D supplementation) during autumn. Applied training loads could also influence the blood parameters variability in young soccer players. Regular measurements of 25(OH)D concentration are helpful in identifying potential drops and allows for the preparation of individual supplementation plans for the players.



#2 Effects of Biological Age on Athletic Adaptations to Combined Plyometric and Sprint with Change of Direction with Ball Training in Youth Soccer Players

Reference: Biology (Basel). 2023 Jan 12;12(1):120. doi: 10.3390/biology12010120.

Authors: Hamza Marzouki, Samar Sbai, Ibrahim Ouergui, Okba Selmi, Marilia S Andrade, Ezdine Bouhlel, Mabliny Thuany, Katja Weiss, Pantelis T Nikolaidis, Beat Knechtle

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Summary: There is evidence for the effectiveness of youth combined plyometric and sprint with change of direction (COD) training. However, the evidence is not well-known regarding the in-season effects of biological age (peak height velocity-PHV) on the motor adaptive processes following combined plyometric and COD with ball training (P-CODBT) in youth soccer players. This study aimed to examine the in-season effects of P-CODBT (8 weeks and twice a week) on the athletic performances of male youth soccer players, circa- and post-PHV. In a randomized controlled training study with pre-to-post measurements, forty-eight male players were assigned into two experimental (performing P-CODBT; n = 12 × circa-PHV and n = 12 × post-PHV) and two control groups (CONG; n = 12 × circa-PHV and n = 12 × post-PHV). The pre- and post-training participants were assessed for their anthropometric, linear sprinting with and without a ball, COD speed with and without a ball, vertical jump, dynamic balance, and endurance-intensive performances. After the intervention, the experimental condition induced significant (all p &lt; 0.0001) and small to large effect size (ES = 0.263-3.471) additional gains only on explosive measures compared to CONG. Both the experimental (all p &lt; 0.0001; ES = 0.338-1.908) and control (p = 0.011-0.0001; ES = 0.2-1.8) groups improved their athletic performances over the training period. The improvements generated by p-CODBT were not affected by biological age. In-season short-term P-CODBT (twice a week) could be safe way to generate benefits in explosive performances in youth soccer players, which are relevant components of match-winning actions in soccer.



#3 Factors influencing the implementation of the EuroFIT lifestyle change program in professional football clubs in Europe: a qualitative study in four European countries

Reference: Transl Behav Med. 2023 Jan 24;ibac100. doi: 10.1093/tbm/ibac100. Online ahead of print.

Authors: Femke van Nassau, Anita Huis, Irene van de Glind, Eivind Andersen, Christopher Bunn, Cindy M Gray, Kate Hunt, Judith G M Jelsma, Willem van Mechelen, Heather Morgan, Øystein Røynesdal, Hugo V Pereira, Hidde P van der Ploeg, Glyn C Roberts, Marlene N Silva, Marit Sørensen, Sally Wyke, Maria W G Nijhuis-van der Sanden, Theo van Achterberg

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Summary: This paper investigated facilitators and barriers to implementing the European Football Fans in Training program (EuroFIT) in professional sports clubs in England, the Netherlands, Norway, and Portugal. We analyzed qualitative data collected at clubs that delivered EuroFIT, based on semi-structured interviews with coordinating staff (n = 15), coaches (n = 16), and focus group interviews with participants (n = 108), as well as data from clubs that considered delivering EuroFIT in the future, based on interviews with staff (n = 7) and stakeholders (n = 8). Facilitators for implementation related to the content and structure of the program, its evidence-base, and the context for delivery in the football stadia. Financial and human resources were both facilitators and barriers. Further barriers were mostly practical, relating to human resources and infrastructure. Major differences between countries related to experience and commitment to running community projects, and differences in infrastructure, financing, and human resources. Professional football clubs' ability to support health promotion efforts depended on their ethos and the financial and human resources available to them. Overall, the EuroFIT program was well received by clubs, coaches, participants, and stakeholders, which was reflected by the many facilitators supporting sustained implementation. For sustainable implementation, it is crucial that clubs and their stakeholders engage fully with the EuroFIT program and understand that for an adequate program delivery their views (ethos) and ways of working influence the implementation and thereby the effectiveness of EuroFIT. An important prerequisite for future roll out of EuroFIT would be a strong EuroFIT delivery partner organization to ensure financial and human resources while overseeing and guiding the quality of delivery in clubs.



#4 Football movement profile analysis and creatine kinase relationships in youth national team players

Reference: Physiol Int. 2023 Jan 24. doi: 10.1556/2060.2023.00160. Online ahead of print.

Authors: György Szigeti, Gábor Schuth, Tamás Kovács, Péter Revisnyei, Alija Pasic, Ádám Szilas, Tim Gabbett, Gábor Pavlik

Summary: Creatine kinase (CK) is widely used as a monitoring tool to make inferences on fatigue and readiness in elite soccer. Previous studies have examined the relationship between CK and GPS parameters, however these metrics may not accurately describe the players' load during soccer-specific movements. Football Movement Profile (FMP) monitoring is a viable option for such purposes, providing solely inertial sensor-based data and categorizing movements according to intensity (very low, low, medium, high) and movement type (running-linear locomotive, dynamic - change of direction or speed). We investigated the relationship between the FMP distribution of youth (U16-U21) national team soccer players and the absolute day-to-day change in CK. We applied Spearman's correlations, principal component analysis and K-means clustering to classify players' CK responses according to their specific FMP. Moderate to large negative associations were found between very low intensity FMP parameters and CK change (r = -0.43 ± 0.12) while large positive associations were identified between CK change and other FMP metrics (r = 0.62 ± 0.12). Best fitting clustering methods were used to group players depending on their CK sensitivity to FMP values. Principal component analysis explained 83.0% of the variation with a Silhouette score of 0.61 for the 4 clusters. Our results suggest that soccer players can be clustered based on the relationship between FMP measures and the CK change. These findings can help to plan soccer training or recovery sessions according to the desired load on skeletal muscle, as FMP monitoring might bridge the limitations of GPS telemetry.



#5 An evaluation of the quality of CPR chest compressions performed on football-equipped and obese simulation manikins

Reference: Prehosp Emerg Care. 2023 Jan 24;1-11. doi: 10.1080/10903127.2023.2172494. Online ahead of print.

Authors: Jennifer A Longo, Katie J Lyman, Thomas A Hanson, Bryan Christensen, Gianluca Del Rossi

Summary: Protective athletic equipment may hamper the delivery of effective chest compressions. Unfortunately, an algorithm for managing cardiac arrest emergencies with equipment-laden athletes has yet to be established by national CPR certifying agencies. Further, athletes classified as being overweight or obese carry adipose in the thoracic region, which has been reported to inhibit the ability of rescuers to provide quality chest compressions. Thus, the purpose of this study was two-fold. The first purpose was to assess the ability of emergency responders to perform CPR chest compressions on an obese manikin. The second purpose was to analyze the effect of American football protective equipment on the performance of chest compressions by emergency responders. Fifty emergency responders completed four 2-minute bouts of compression-only CPR. The scenarios included performing chest compressions on both traditional and obese CPR manikins, and performing chest compressions over a set of shoulder pads/chest protector that is used in the sport of American football on both traditional and obese manikins. The most notable outcomes in this study were related to chest compression depth, which fell well below the minimum recommended depth published by the American Heart Association in all conditions. Mean compression depth was significantly lower when performed on the obese manikin (avg over pads = 32.8, SD = 9.2 mm; avg no pads = 38.2, SD = 9.1 mm) compared to the traditional manikin (avg over pads = 40.0, SD = 10.9 mm; avg no pads = 40.8, SD = 14.8 mm), with statistical analyses revealing a significant effect due to both manikin size (p < 0.001) and the presence of equipment (p = 0.003), and a statistically significant interaction effect (p = 0.035). Chest recoil data revealed a statistically significant effect due to both manikin size (p = 0.017) and the presence of chest/shoulder safety pads (p = 0.003). Within this sample of emergency responders, chest compressions were adversely affected both by the equipment and obesity. Additionally, the traditional manikin received comparable chest compressions regardless of the presence or absence of football protective equipment, albeit both conditions resulted in poor depth performance.



#6 The Qatar 2022 World Cup warm-up: Football goal-scoring evolution in the last 14 FIFA World Cups (1966-2018)

Reference: Front Psychol. 2023 Jan 4;13:954876. doi: 10.3389/fpsyg.2023.954876. eCollection 2022.

Authors: Branimir Mićović, Bojan Leontijević, Milivoj Dopsaj, Aleksandar Janković, Zoran Milanović, Amador Garcia Ramos

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Summary: The aim of this study was to elucidate pattern of attacking actions leading up to goal scoring during the 14 FIFA World Cups from 1966 to 2018. The study analysed 1881 goals scored during a total of 732 matches. We employed observational methodology design. Before goal analysis began, it was developed the observing protocol in which data related to selected variables, by system of notation, was entered after reviewing each individual goal scoring action. The analysis of all video material was carried out independently by four experienced examiners (three of them are Ph.D in sports science and one is Ph.D. candidate in sports science with at least 7 years of coaching and experience as analyst in football). The inter-and intra-observer reliability presented good level of agreement. The kappa values ranged from 0.82 (goal scoring through open play) to 1.00 (action leading up to goal), showing a very high agreement for all performance variables. Interclass correlation was very high (ICC = 0.966, 95% upper and lower confidence intervals were between 0.933 and 1.00). A statistically significant trend (p < 0.05) from 1966 to 2018 was identified towards a higher relative frequency of goals scored from set play and collective actions from open play. The Chi-square did not reveal significant differences in the frequency of goal scoring patterns and goal-scoring zones. The results also revealed that the majority of goals were scored between the 76th and 90th minutes of a match (22.7%), from open play (70.5%), inside the penalty area (54.7%), one touch finishing (62.5%), and collective attacks in open play (55.8%). These findings may provide a possible strategic direction for improving goal-scoring performance in football, as well as practical implementation in World Cup tournament preparation.



#7 Relationship between Repeated Sprint Ability, Countermovement Jump and Thermography in Elite Football Players

Reference: Sensors (Basel). 2023 Jan 5;23(2):631. doi: 10.3390/s23020631.

Authors: Carlos Majano, Jorge García-Unanue, Antonio Hernandez-Martin, Javier Sánchez-Sánchez, Leonor Gallardo, Jose Luis Felipe

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Summary: Football is a very demanding sport which requires players to exert maximum effort, producing fatigue and eventually injuries. Thermography can be used to detect fatigue and prevent its consequences through thermal asymmetries in the bilateral body areas; however, its adequacy for elite footballers has not been widely studied. Therefore, the objective of the present investigation was to determine the suitability of thermography to detect fatigue in male football players. For this reason, twenty participants were gathered into a pair of subgroups (low [&lt;0.2 °C] vs. high thermal asymmetry [≥0.2 °C]) based on a thermography session of the lower limbs (thighs, calves, and hamstrings). After the thermography session, players performed CMJs before and after an RSA test (6 × 30 m/20″). A mixed two-way analysis of variance and Bonferroni post hoc pairwise comparisons were undertaken to analyse the results. No significant differences (p &gt; 0.05) were found in any of the RSA test variables between low and high thermal asymmetry groups for thighs and calves. On the other hand, the low thermal asymmetry hamstring group reported a smaller percentage difference in sprints for the first sprint (%Diff) and a larger percentage difference in sprints two and three with respect to the best sprint (%Best). For CMJs, the low thermal asymmetry hamstring group reported significantly higher values post-RSA test, indicating better performance. Accordingly, thermography can provide information about performance in CMJ and RSA tests through hamstring asymmetries over 0.2 °C. Meanwhile, larger asymmetries than 0.2 °C in calves and thighs do not seem to be related to performance in these tests; therefore, coaches should consider if it is optimal to align players with high hamstring asymmetries.



#8 Weekly External Load Performance Effects on Sports Injuries of Male Professional Football Players

Reference: Int J Environ Res Public Health. 2023 Jan 8;20(2):1121. doi: 10.3390/ijerph20021121.

Authors: Francisco Martins, Adilson Marques, Cíntia França, Hugo Sarmento, Ricardo Henriques, Andreas Ihle, Marcelo de Maio Nascimento, Carolina Saldanha, Krzysztof Przednowek, Élvio Rúbio Gouveia

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Summary: One of the most challenging issues professional football players face throughout their careers is injuries. Those injuries often result from suboptimal training programs that were not designed according to the players' individual needs. This prospective study aimed to examine in detail the effects of sports injuries on professional football players' weekly external load performances. Thirty-three male professional football players were monitored using 10-Hz Global Positioning System (GPS) units (Apex pro series, StatSports) during an entire season. The variables considered in the analysis were total distance (TD), high-speed running (HSR), accelerations (ACC), and decelerations (DEC). The comparisons were made between the four-week block before injury (-4T), four-week block after return (+4T), and players' season averages (S). Players displayed significantly higher values of TD, HSR, ACC, and DEC in the -4T, compared to the other two moments (+4T and S). Furthermore, the comparison between the +4T and S showed no significant variations in the GPS metrics. It was shown that a significant increase in players' weekly external load performance over a four-week period may have a negative effect on the occurrence of injuries from a professional football standpoint. Future research should consider the effects of injury severity on players' external load variations.



#9 Muscle Contractile Properties Measured by the Tensiomyography (TMG) Method in Top-Level Football Players of Different Playing Positions: The Case of Serbian Super League

Reference: Int J Environ Res Public Health. 2023 Jan 4;20(2):924. doi: 10.3390/ijerph20020924.

Authors: Lazar Pajović, Lazar Toskić, Veroljub Stanković, Ljubiša Lilić, Borislav Cicović

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Summary: The aim of this study is to investigate the differences in muscle contractile properties measured by the TMG method between top-level football players of different playing positions. The sample consisted of 57 football players from the Serbian Super League, divided into three groups: defenders-DF, midfielders-MF, and forwards-FW. Muscles included in the study were the Rectus Femoris (RF), Vastus Medialis (VM), Vastus Lateralis (VL), Biceps Femoris (BF), and Semitendinosus (ST) of the right (R) and left (L) leg. The TMG parameters used in this study were contraction time (Tc), delay time (Td), relaxation time (Tr), maximal displacement (Dm), and sustain time (Ts). The ANOVA results showed that differences in TMG parameters between top-level football players of different playing positions are small and exist only in the Tr of RF (F = 4.658, p = 0.014), BF (F = 4.433, p = 0.016), and ST muscle (F = 3.808, p = 0.028), and the Tc (F = 3.214, p = 0.048) and Td (F = 3.705, p = 0.031) of the VM muscle. All differences were detected between DF and FW players, and all differences were in the left (non-dominant) leg. The results obtained in this study indicate that the training and selection process in football, from the aspect of functional and mechanical muscle properties, should be similar for all players, regardless of playing position. It has been shown that TMG has relatively low sensitive strength for detecting differences between football players of different playing positions.



#10 Effects of a Football Simulated Exercise on Injury Risk Factors for Anterior Cruciate Ligament (ACL) Injury in Amateur Female Players

Reference: Biology (Basel). 2023 Jan 12;12(1):124. doi: 10.3390/biology12010124.

Authors: Harriet Ferguson, Jessica Piquet, Monèm Jemni, Anne Delextrat

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Summary: Females are more at risk of Anterior Cruciate Ligament (ACL) injuries than males; however, there is limited literature on neuromuscular risk factors such as angle-specific hamstring/quadriceps functional strength ratios (Hecc/Qcon) and rate of torque development (RTD) in female footballers. The aim of this study was to investigate the effects of fatigue on these neuromuscular risk factors. Thirty-three amateur players (20.3 ± 2.0 years old, 1.67 ± 9.31 m, 63.4 ±8.1 kg, 23.6 ± 5.7% body fat) performed strength assessments of the quadriceps (concentrically, Qcon) and hamstrings (eccentrically, Hecc) on both legs on an isokinetic dynamometer, before and immediately after a football-specific exercise. Results showed significantly lower peak Hecc (-15.1 to -15.5%), peak Hecc/Qcon (-8.8 to -12.9%) and RTD (-14.0 to -17.0%) for hamstring eccentric contractions after fatigue in the dominant and non-dominant legs. Furthermore, significant decreases in Hecc/Qcon were observed at 10° only in the dominant leg (-15.5%), and at 10°, 20° and 30° in the non-dominant leg (-15.1 to -21.8%). These results suggest a reduced capacity of the hamstrings to stabilise the knee joint with fatigue. Unlike results previously shown on men, the non-dominant leg seemed more affected, highlighting the need to consider specific prevention measures in females.



#11 Do Repeated Sprints Affect the Biceps Femoris Long Head Architecture in Football Players with and without an Injury History?-A Retrospective Study

Reference: Biology (Basel). 2023 Jan 8;12(1):96. doi: 10.3390/biology12010096.

Authors: Ricardo Pimenta, Hugo Antunes, Tomás Lopes, António Veloso

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Summary: The aim of this study was to compare the biceps femoris long head (BFlh) architecture between football players with (twelve) and without (twenty) history of BFlh injury before and after a repeated sprint task. Fascicle length (FL), pennation angle (PA) and muscle thickness (MT) were assessed at rest and in the active condition before and after the repeated sprint protocol. Athletes with previous BFlh injury showed shorter FL at rest (p = 0.014; η2p = 0.196) and active state (p &lt; 0.001; η2p = 0.413), and greater PA at rest (p = 0.002; η2p = 0.307) and active state (p &lt; 0.001; η2p = 0.368) before and after the task. Intra-individual comparisons showed that injured limbs have shorter FL at rest (p = 0.012; η2p = 0.519) and in the active state (p = 0.039; η2p = 0.332), and greater PA in passive (p &lt; 0.001; η2p = 0.732) and active conditions (p = 0.018; η2p = 0.412), when compared with contralateral limbs. Injured players, at rest and in the active condition, display shorter BFlh FL and greater PA than contralateral and healthy controls after repeated sprints. Moreover, the BFlh of injured players presented a different architectural response to the protocol compared with the healthy controls.



#12 How Football Players' Age Affect Passing Patterns of Play According to Field Location

Reference: Children (Basel). 2023 Jan 13;10(1):157. doi: 10.3390/children10010157.

Authors: Nuno Coito, Hugo Folgado, Diogo Monteiro, Bruno Travassos

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Summary: This study aimed to characterize the passing patterns that support collective tactical behaviour in football players of different ages (U15, U17, and U19) in different field zones. Two hundred and twenty-eight male players, divided into U15, U17, and U19, participated in the study. Cluster analysis was used to group the passes into three sizes (short, medium, and long). The chi-square test was used to analyse the effect of player age on game-passing patterns in each field zone. The results revealed that long and medium passes were used more in areas close to the goals and short passes in the middle area of the field, concerning all ages (p &lt; 0.001). Furthermore, the analysis of the relative distance between the ball carrier and the receiver indicated that older players (U17 and U19) used more distant players to pass the ball in medium and long passes. These results can help coaches design small-sided games according to the players' ages and adjust to the field's space and the numerical relationship, thus creating a greater transfer from training to competition.



#13 Agility Skills, Speed, Balance and CMJ Performance in Soccer: A Comparison of Players with and without a Hearing Impairment

Reference: Healthcare (Basel). 2023 Jan 13;11(2):247. doi: 10.3390/healthcare11020247.

Authors: Hakan Yapici, Yusuf Soylu, Mehmet Gulu, Mehmet Kutlu, Sinan Ayan, Nuray Bayar Muluk, Monira I Aldhahi, Sameer Badri Al-Mhanna

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Summary: This study investigates the differences in agility, speed, jump and balance performance and shooting skills between elite hearing-impaired national team soccer players (HISP) and without-hearing-impairment elite soccer players (woHISP). Players were divided into two groups, the HISP group (n = 13; 23.5 ± 3.1 years) and the woHISP group (n = 16; 20.6 ± 1.4 years), and were tested in three sessions, seven apart, for metrics including anthropometrics, speed (10 m, 20 m and 30 m), countermovement jump (CMJ), agility (Illinois, 505, zigzag), T test (agility and shooting skills), and balance. The results showed that 30 m, 20 m and 10 m sprint scores, agility/ skills (sec), shooting skills (goals), zigzag, Illinois, and 505 agility skills, and countermovement jump scores were significantly lower among players with hearing impairments (p &lt; 0.05). There were no significant T test differences between HISP and woHISP (p &gt; 0.05). The HISP showed right posterolateral and posteromedial, and left posterolateral and posteromedial scores that were lower than the woHISP group (p &lt; 0.05). Anterior scores were not significantly different between each leg (p &gt; 0.05). In conclusion, the HISP group showed higher performance scores for speed (10 m, 20 m and 30 m), CMJ, agility (Illinois, 505, zigzag) and T test (sec and goals), but not balance. Hearing-impaired soccer players are determined by their skill, training, and strategy, not their hearing ability.



#14 Does Inspiratory Muscle Training Affect Static Balance in Soccer Players? A Pilot Randomized Controlled Clinical Trial

Reference: Healthcare (Basel). 2023 Jan 14;11(2):262. doi: 10.3390/healthcare11020262.

Authors: Silvana Loana de Oliveira-Sousa, Martha Cecilia León-Garzón, Mariano Gacto-Sánchez, Alfonso Javier Ibáñez-Vera, Luis Espejo-Antúnez, Felipe León-Morillas

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Summary: Inspiratory muscle training (IMT) is effective in improving postural stability and balance in different clinical populations. However, there is no evidence of these effects in soccer players. A single-blind, two-arm (1:1), randomized, placebo-controlled pilot study on 14 soccer players was performed with the main aim of assessing the effect of IMT on static balance, and secondarily, of examining changes in the respiratory muscle function. The experimental group (EG) received an IMT program with progressive intensity, from 20% to 80%, of the maximal inspiratory pressure (MIP). The sham group (SG) performed the same program with a fixed load of 20% of the MIP. Static balance and respiratory muscle function variables were assessed. A two-factor analysis of variance for repeated measures was used to assess differences after training. Statistical significance was set at p &lt; 0.05. Significant increases were observed in the EG on length of sway under eyes open (from 2904.8 ± 640.0 to 3522.4 ± 509.0 mm, p = 0.012) and eyes closed (from 3166.2 ± 641.3 to 4173.3 ± 390.8 mm, p = 0.004). A significant increase in the maximal voluntary ventilation was observed for both groups (EG p = 0.005; SG p = 0.000). No significant differences existed between the groups. IMT did not improve the static balance in a sample of soccer players. Conducting a high-scale study is feasible and could refine the results and conclusions stemming from the current pilot study.



#15 Psychological Intervention Based on Mental Relaxation to Manage Stress in Female Junior Elite Soccer Team: Improvement in Cardiac Autonomic Control, Perception of Stress and Overall Health

Reference: Int J Environ Res Public Health. 2023 Jan 4;20(2):942. doi: 10.3390/ijerph20020942.

Authors: Eleonora Pagani, Naomi Gavazzoni, Giuseppina Bernardelli, Mara Malacarne, Nadia Solaro, Emanuele Giusti, Gianluca Castelnuovo, Piero Volpi, Giulia Carimati, Daniela Lucini

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Summary: Chronic stress may represent one of the most important factors that negatively affects the health and performance of athletes. Finding a way to introduce psychological strategies to manage stress in everyday training routines is challenging, particularly in junior teams. We also must consider that a stress management intervention should be regarded as "efficacious" only if its application results in improvement of the complex underlying pathogenetic substratum, which considers mechanistically interrelated factors, such as immunological, endocrine and autonomic controls further to psychological functioning and behavior. In this study, we investigated the feasibility of implementing, in a standard training routine of the junior team of the Italian major soccer league, a stress management program based on mental relaxation training (MRT). We evaluated its effects on stress perception and cardiac autonomic regulation as assessed by means of ANSI, a single composite percentile-ranked proxy of autonomic balance, which is free of gender and age bias, economical, and simple to apply in a clinical setting. We observed that the simple employed MRT intervention was feasible in a female junior soccer team and was associated with a reduced perception of stress, an improved perception of overall health, and a betterment of cardiac autonomic control. This data may corroborate the scientific literature that indicates psychological intervention based on MRT as an efficacious strategy to improve performance, managing negative stress effects on cardiac autonomic control.



#16 Dynamometric Strength Profile of Hip Muscles in Youth Soccer Players

Reference: Int J Environ Res Public Health. 2023 Jan 11;20(2):1291. doi: 10.3390/ijerph20021291.

Authors: Guido Contreras-Díaz, Luis Javier Chirosa-Ríos, Ignacio Chirosa-Ríos, Antonio Riego-Ruiz, Leonardo Intelangelo, Marcelo Tuesta-Roa, Jorge Morales-Zúñiga, Daniel Jerez-Mayorga

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Summary: Soccer is the most widely practiced sport in the world, demanding high-speed activities such as jumps, sprints and changes of direction. Therefore, having optimal levels of muscle strength improves performance and reduces the injury rate. The objectives of our study were (i) to determine the dynamometric profile of hip muscle strength in young soccer players by position, evaluated at different isokinetic speeds, (ii) to describe the conventional and functional unilateral muscle strength ratios, (iii) to analyze the bilateral balance. Thirty-seven male soccer players (age 17.02 ± 0.92 years) participated in the study. Strength assessment was performed with a functional electromechanical dynamometer, and concentric and eccentric strength of abductors, adductors, extensors and hip flexors were measured bilaterally at 0.5 m/s and 1 m/s. For eccentric right hip abduction at 0.5 m/s, defenders are significantly stronger than midfielders (p = 0.013) and stronger than forwards (p = 0.140). For eccentric right hip adduction at 0.5 m/s, defenders are significantly stronger than midfielders (p = 0.005) and stronger than forwards (p = 0.253), as for eccentric right hip adduction at 1 m/s, defenders are significantly stronger than midfielders (p = 0.014) and stronger than forwards (p = 0.084). There is a significant effect for the conventional strength ratio of left abduction/adduction at 1 m/s. The conventional strength ratio of forwards is significantly higher than that of defenders (p = 0.045) and higher than that of midfielders (p = 0.152).



#17 Relationship between Body Composition and Specific Motor Abilities According to Position in Elite Female Soccer Players

Reference: Int J Environ Res Public Health. 2023 Jan 11;20(2):1327. doi: 10.3390/ijerph20021327.

Authors: Mima Stanković, Ilma Čaprić, Dušan Đorđević, Stefan Đorđević, Adem Preljević, Admira Koničanin, Džejla Maljanović, Hamza Nailović, Iso Muković, Igor Jelaska, Goran Sporiš

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Summary: Contemporary top-division soccer is characterized by high-intensity activity throughout the entire match, which also requires high levels of a wide range of the players' functional and motor abilities. Furthermore, motor and functional requirements vary in relation to the players' position on the pitch. In view of the above, the objective of this study was to determine any differences in body composition and specific motor abilities in relation to position. Twenty elite female soccer players (age: 20.90 ± 3.70 years; height: 166.95 ± 5.83 cm; weight: 58.97 ± 7.50 kg; training experience: 9.50 ± 4.11 years) were recruited for the purpose of this study. Based on their position within the team, the players were divided into three groups: defenders (N-7), midfielders (N-6), and forwards (N-7). The instruments used included the InBody770 (for body composition assessment), Optojump and Polar for the assessment of specific motor abilities. The results obtained indicate a strong link between the parameters body composition and specific motor abilities; however, the level of significance varies, as do the variables concerning specific motor abilities and body composition in relation to the players' position on the pitch. In accordance with these results, coaches and others working in the soccer industry should be apprised of the necessity of a tailored approach when it comes to planning the development of specific motor abilities, as well of with the importance of balanced body composition as prerequisites for achieving top results.



#18 Relationship between Objective and Subjective Fatigue Monitoring Tests in Professional Soccer

Reference: Int J Environ Res Public Health. 2023 Jan 14;20(2):1539.  doi: 10.3390/ijerph20021539.

Authors: João Lourenço, Élvio Rúbio Gouveia, Hugo Sarmento, Andreas Ihle, Tiago Ribeiro, Ricardo Henriques, Francisco Martins, Cíntia França, Ricardo Maia Ferreira, Luís Fernandes, Pedro Teques, Daniel Duarte

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Summary: Studying fatigue is challenging because it is influenced by physiological, psychological, and sociological states. Fatigue can be assessed objectively or subjectively, but the literature has difficulty understanding how an analytical test relates to a response via a questionnaire. Thus, the purpose of this study was to evaluate the relationships between objective fatigue variables (Squat Jump (SJ) and Countermovement Jump (CMJ)) measured on day-2 to the game and subjective fatigue (Rating Perceived Exertion (RPE) measured on day-3 to the game and Hooper Index (HI) measured on day-2). The sample comprised 32 professional football players from the First Portuguese League aged 25.86 ± 3.15 years. The Spearman correlations and regression analyses were used to study the relationships between the variables. The results showed statistically significant (p &lt; 0.05) but small correlations (0.113-0.172) between several objective metrics and the subjective metrics evaluated. In addition, we found two weak models with statistical significance (p &lt; 0.05) between the dependent objective variables (contact time, height, and elasticity index) and the HI (R2 = 3.7%) and RPE (R2 = 1.6%). Also, nine statistically significant (p &lt; 0.05) but weak models were observed between the subjective dependent variables (HI and RPE) and contact time (R2 = 1.8-2.7%), flight time (R2 = 1.1-1.9%), height (R2 = 1.2-2.3%), power (R2 = 1.4%), pace (R2 = 1.2-2.1%), and elasticity index (R2 = 1.6%). In conclusion, objective and subjective fatigue-monitoring tests in professional soccer do not measure identical but rather complementary aspects of fatigue, and therefore, both need to be considered to gain a holistic perspective.






Overestimation of maximal aerobic speed by the Université de Montréal track test and a 1500-m-time trial in soccer

The aim was 1) to compare two different cardiopulmonary exercise testing (CPET) based methods to assess maximal aerobic speed (MAS) and 2) to investigate the convergent validity of two common field tests to estimate MAS in footballers.





From Junior to Elite in Soccer: Exploring the Relative Age Effect and Talent Selection in Spanish Youth National Teams

This study has the twofold purpose of analyzing RAE in Spanish youth national soccer teams and examining the prediction value of being selected for national youth teams to be a professional.





Latest research in football - week 3 - 2023

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 sprint versus strength training on risk factors for hamstring injury in football players

Reference: J Sports Med Phys Fitness. 2023 Jan 18. doi: 10.23736/S0022-4707.22.14529-9. Online ahead of print.

Authors: Alessandro Sancese, Luke Taylor, Greg Walsh, Erin Byrd, Anne Delextrat

Summary: This study aimed to compare the effects of in-season sprint training vs. Nordic hamstring exercise (NHE) training on risk factors for hamstring strain injuries (HSI). Eighteen male university football players (20.9±2.5 years; 181±7 cm; 75.8±9.1 kg; 15.2±3.5% of body fat) were randomly allocated to a sprint group or NHE group. They completed baseline isokinetic strength and sprint mechanics assessments prior to their assigned intervention performed twice weekly for 4-weeks, before post-testing. A mixed design ANOVA with repeated measures assessed time, group and interaction effects for all risk factors. There were significant increases in hamstring eccentric peak torque at 60°·s-1 (+8% - 9.9%), the torque produced at 20° (+15%) and 10° (+21% - 31%), as well as a rightward shift in angle of peak torque towards knee extension (-27% - -36%) in both groups (P<0.05). We also observed a significant increase (+24.5%) in hamstring eccentric peak torque at 180°·s-1 in the strength group only and significant improvements (+29.4%) in the rate of torque development of the dominant leg at 60°·s-1 in the sprint group only (P<0.05). No significant effect was noted on sprint performance or sprint mechanics (P>0.05). These findings suggest that both training programs can be effective to mitigate the risk of HSI, but through different mechanisms.



#2 Using machine learning pipeline to predict entry into the attack zone in football

Reference: PLoS One. 2023 Jan 18;18(1):e0265372. doi: 10.1371/journal.pone.0265372. eCollection 2023.

Authors: Leandro Stival, Allan Pinto, Felipe Dos Santos Pinto de Andrade, Paulo Roberto Pereira Santiago, Henrik Biermann, Ricardo da Silva Torres, Ulisses Dias

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Summary: Sports sciences are increasingly data-intensive nowadays since computational tools can extract information from large amounts of data and derive insights from athlete performances during the competition. This paper addresses a performance prediction problem in soccer, a popular collective sport modality played by two teams competing against each other in the same field. In a soccer game, teams score points by placing the ball into the opponent's goal and the winner is the team with the highest count of goals. Retaining possession of the ball is one key to success, but it is not enough since a team needs to score to achieve victory, which requires an offensive toward the opponent's goal. The focus of this work is to determine if analyzing the first five seconds after the control of the ball is taken by one of the teams provides enough information to determine whether the ball will reach the final quarter of the soccer field, therefore creating a goal-scoring chance. By doing so, we can further investigate which conditions increase strategic leverage. Our approach comprises modeling players' interactions as graph structures and extracting metrics from these structures. These metrics, when combined, form time series that we encode in two-dimensional representations of visual rhythms, allowing feature extraction through deep convolutional networks, coupled with a classifier to predict the outcome (whether the final quarter of the field is reached). The results indicate that offensive play near the adversary penalty area can be predicted by looking at the first five seconds. Finally, the explainability of our models reveals the main metrics along with its contributions for the final inference result, which corroborates other studies found in the literature for soccer match analysis.



#3 Analysis of scored goals in the cerebral palsy football World Cup

Reference: J Sports Sci. 2023 Jan 18;1-9. doi: 10.1080/02640414.2023.2167257. Online ahead of print.

Authors: Iván Peña-González, Juan F Maggiolo, Alejandro Javaloyes, Manuel Moya-Ramón

Summary: This study aimed to report the goal patterns in cerebral palsy (CP) football for a better understanding of the performance of this para-sport. All goals (270) of the 48 2019 IFCPF World Cup matches were analysed through match reports, and 65% of them were analysed by video footage. The results showed 5.6 goals per match. Teams that scored more and conceded fewer goals correlated to a better ranking position in the championship (r= 0.72-0.73; p< 0.01). The distribution of goals scored was not biased by halves (49.3% vs 50.7%; χ2= 0.1; p= 0.88) nor by 15-min periods (26.3% vs 23.0% vs 23.3% vs 27.4%; χ2= 0.5; p= 0.92). In 91.7% of the matches, the team which scored the first goal went on to win the match (χ2= 81.5; p< 0.01). FT3 players scored more goals by player (χ2= 22.1; p< 0.01), while there were no statistical differences in the distribution of goals conceded by goalkeepers according to their sport class (χ2= 4.7; p= 0.09). The goals were scored mainly from organized attacks (74.4%), from the penalty area (52.5%) and through individual action (51.9%). All this information could be crucial for coaches in CP football to plan their game strategies.



#4 The Five-substitution Option Enhances Teams' Running Performance at High Speed in Football

Reference: Int J Sports Med. 2023 Jan 20. doi: 10.1055/a-1982-9808. Online ahead of print.

Authors: Alejandro López-Valenciano, Víctor Moreno-Perez, Roberto López-Del Campo, Ricardo Resta, Juan Del Coso

Summary: The aim of this investigation was to describe how the introduction of the five-substitution option affected football teams' running performance. A comparative analysis was performed in 17 professional football teams for the 2019-2020 (up to three substitutions) vs 2020-2021 (five substitutions option) seasons in LaLiga. The five-substitution option increased the number of substitutions (from 2.9±0.1 to 4.2±1.0 substitutions/match, respectively; p<0.01, Effect Size (ES)=2.11) but it did not change the time selected for the first substitution (from 57.5±13.0 to 56.2±13.7 min; p=0.06, ES=0.1). Total running distance was similar between seasons but running distance at 21.0-23.9 km/h (from 3.0±0.4 to 3.2±0.4 km; p=0.01, ES=0.6) and at≥24.0 km/h (from 3.0±0.6 to 3.2±0.5 km; p=0.01, ES=0.3) were higher with the five-substitution option. These increases were associated with a higher distance covered by starting players (p<0.05) rather than an effect of substitute players.: With the five-substitution option, team coaches increased the number of substitutions per match which enhanced the possibilities of the team's staff to manage players' physical load. The five-substitution option allowed also increased running performance at≥21.0 km/h during the matches.



#5 Relationships Between Sprint, Acceleration, and Deceleration Metrics with Training Load in Division I Collegiate Women's Soccer Players

Reference: J Hum Kinet. 2023 Jan 4;85:53-62. doi: 10.2478/hukin-2022-0109. eCollection 2022 Dec.

Authors: Dieanna C Prudholme, Jared W Coburn, Scott K Lynn, Robert G Lockie

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Summary: Player load is a variable derived from GPS technology that quantifies external load demands. Sprints and change-of-direction movements are high-intensity activities that place stress on the body. Research is needed to determine which sprint metrics may relate to and predict player load during practice sessions in collegiate women's soccer players, as coaches could manipulate the most impactful variables. This study analyzed which sprint metrics related to GPS player load in women's soccer players from one Division I team. Data from 19 practice sessions for 18 field players were analyzed. Players wore GPS sensors during all training sessions, and the variables assessed were player load, sprint count, sprint volume, sprint distance, average top speed, maximum top speed, and the number of accelerations and decelerations in different speed zones (±1, ±2, ±3, ±4, ±5 m/s2). Pearson's correlations (p < 0.05) analyzed relationships between the sprint variables and player load. Stepwise regression analyses (p < 0.05) determined if any metrics predicted player load. The results indicated significant relationships between player load and sprint count, maximum top speed, sprint distance, sprint volume, number of decelerations at -1, -2, and -3 m/s2, and accelerations at 1, 2, and 5 m/s2(r = 0.512-0.861, p ≤ 0.025). Sprint distance and decelerations at 1 m/s2predicted player load (p = 0.001, r2= 0.867). Maximal sprinting and decelerations and accelerations at different speeds were significant contributors to player load in collegiate women's soccer players. Sprint distance, decelerations, and accelerations could be targeted in training drills via dimension and movement manipulation to adjust training intensity for collegiate women's soccer players.



#6 Validation of a motion model for soccer players' sprint by means of tracking data

Reference: Sci Rep. 2023 Jan 17;13(1):865. doi: 10.1038/s41598-023-27999-1.

Authors: Takuma Narizuka, Kenta Takizawa, Yoshihiro Yamazaki

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Summary: In soccer game analysis, the widespread availability of play-by-play and tracking data has made it possible to test mathematical models that have been discussed mainly theoretically. One of the essential models in soccer game analysis is a motion model that predicts the arrival point of a player in t s. Although many space evaluation and pass prediction methods rely on motion models, the validity of each has not been fully clarified. This study focuses on the motion model proposed by Fujimura and Sugihara (Fujimura-Sugihara model) under sprint conditions based on the equation of motion. A previous study indicated that the Fujimura-Sugihara model is ineffective for soccer games because it generates a circular arrival region. This study aims to examine the validity of the Fujimura-Sugihara model using soccer tracking data. Specifically, we quantitatively compare the arrival regions of players between the model and real data. We show that the boundary of the player's arrival region is circular rather than elliptical, which is consistent with the model. We also show that the initial speed dependence of the arrival region satisfies the solution of the model. Furthermore, we propose a method for estimating valid kinetic parameters in the model directly from tracking data and discuss the limitations of the model for soccer games based on the estimated parameters.



#7 Effect of High-Intensity vs. Moderate-Intensity Resistance Training on Strength, Power, and Muscle Soreness in Male Academy Soccer Players

Reference: J Strength Cond Res. 2023 Jan 18. doi: 10.1519/JSC.0000000000004387. Online ahead of print.

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

Summary: The aim of this study were to investigate the impact of high-intensity, low-volume (HRT) vs. moderate-intensity, and high-volume resistance training (MRT) vs. soccer training only (control group [CON]) on changes in strength, power, and speed and to compare delayed onset muscle soreness (DOMS) between groups in male academy soccer players (ASP). Twenty-two ASP (age: 18 ± 1 years) were assigned to HRT (n = 8), MRT (n = 7), or CON (n = 7). High-intensity resistance training completed 2 sets of 4 repetitions parallel back squat (PBS) repetitions at 90% 1 repetition maximum (1RM), while MRT performed 3 sets of 8 repetitions PBS repetitions at 80% 1RM, both once a week for 6 weeks in-season, alongside regular soccer training. All groups completed the following pretraining and posttraining assessments: 3RM PBS, bilateral vertical and horizontal countermovement jumps (CMJ), squat jump (SJ), and 30-m sprint. Delayed onset muscle soreness was assessed using a visual analog scale throughout training. High-intensity resistance training and MRT experienced similar increases compared with CON in absolute PBS 3RM (p < 0.001), SJ height (p = 0.001), and CMJ height (p = 0.008) after training. There was a greater increase in PBS 3RM relative to body mass after HRT than MRT and CON (p = 0.001) and horizontal CMJ distance improved in HRT but not in MRT or CON (p = 0.011). There was no change in 10-m, 20-m, or 30-m sprint performance in any group. High-intensity resistance training volume was 58 ± 15% lower than that of MRT (p < 0.001), and DOMS measured throughout training did not differ between groups (p = 0.487). These findings suggest that 1 HRT session a week may be an efficient method for improving strength and power in ASP in-season with minimal DOMS.



#8 Effect of a Four-Week Soccer Training Program Using Stressful Constraints on Team Resilience and Precompetitive Anxiety

Reference: Int J Environ Res Public Health. 2023 Jan 16;20(2):1620.  doi: 10.3390/ijerph20021620.

Authors: Juan Martin Tassi, Jesús Díaz-García, Miguel Ángel López-Gajardo, Ana Rubio-Morales, Tomás García-Calvo

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Summary: The present study examined the effects of stressful constraints during soccer trainings on psychological skill development and internal load when compared with control (nonstressful) trainings. A total of 51 elite male youth soccer players (27 in the experimental group, M = 16.54 years; 24 in the control group, M = 15.44 years) participated in the study. In a 12-week longitudinal survey, team resilience, using the Spanish version of the Characteristics of Resilience in Sports Teams Inventory, and anxiety, using the Sport Anxiety Scale, were measured at baseline (after 4 weeks of regular trainings), postprotocol (after 4 weeks of control or experimental trainings), and follow-up (after 4 weeks of regular trainings). Results show that, when compared with the control group, a program with stressful constraints helped young soccer players to develop better psychological skills: specifically, increased ability to cope with impairments in resilience (both resilience characteristics and team vulnerability under pressure; p &lt; 0.001). Increases in anxiety (p = 0.06) and decreases in preoccupation (p &lt; 0.001) and lack of concentration (p &lt; 0.001) were also observed. The adaptation of human behavior to specific trainings may explain these results. In conclusion, the regular exposure of young soccer players to stressful situations during trainings shows benefits for their psychological skill development in soccer. Then, benefits on internal load were also observed.



#9 Mental health problems, health risk behaviors, and prevention: A qualitative interview study on perceptions and attitudes among elite male soccer players

Reference: Front Public Health. 2023 Jan 5;10:1044601. doi: 10.3389/fpubh.2022.1044601. eCollection 2022.

Authors: Pia Kvillemo, Anders Nilsson, Anna K Strandberg, Karl Björk, Tobias H Elgán, Johanna Gripenberg

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Summary: The purpose of this study was to investigate the perception of mental health problems and health risk behaviors among Swedish male elite soccer players and their attitudes toward possible prevention strategies. Twenty elite soccer players, aged 15-30 years, were recruited through purposive sampling and interviewed via a digital video calling platform. A semi-structured interview guide, encompassing questions about mental health problems, health risk behaviors among soccer teams, peer-relations, relations to coaches, and attitudes toward health risk behaviors, along with proposals for effective interventions, was employed. The interviews were transcribed verbatim and analyzed with qualitative content analysis. The informants reported positive feelings in relation to playing soccer, good health, and few health risk behaviors. Risk factors included a large income, excessive free time, and the need for excitement. Stress and mental health problems were linked to performance pressure, social media, and injuries. Hesitation to talk openly about personal problems due to concerns about negative consequences and the "macho culture" was highlighted as barriers to admit and seek help for personal problems. Some statements indicated openness and the club's efforts to destigmatize personal problems. Positive attitudes toward prevention and suggestions for various measures were prominent. Future research and implementation of interventions should focus on the prevention of health risk behaviors and alleviation of stress and performance pressure, as well as continue the efforts to destigmatize mental health problems and raise awareness among coaches of the importance of their communication and behavior for players' mental health and performance. This could be achieved by developing strategic and systematic policy work, information, and dialogue among players and coaches, in addition to individual digital or face-to-face support, provided by professionals outside the soccer context.



#10 Effect of core training on skill-related physical fitness performance among soccer players: A systematic review

Reference: Front Public Health. 2023 Jan 5;10:1046456. doi: 10.3389/fpubh.2022.1046456. eCollection 2022.

Authors: Shengyao Luo, Kim Geok Soh, Lingling Zhang, Xiuwen Zhai, Jaka Sunardi, Yongqi Gao, He Sun

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Summary: This study aims to present an in-depth review of the available literature on the effect of core training on skill-related physical fitness performance among soccer players, as well as to offer suggestions for researchers and coaches. The data in this study were presented based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Using scientific databases and web search engines including Scopus, Ebscohost, Web of Science, PubMed, and Google Scholar, researchers collected studies from the published literature. Only 26 of the 84 articles satisfied all the inclusion criteria and were thus included in the systematic review. The quality of each study was determined using the PEDro scale. The scores for 26 studies range between three and six. Core training can improve soccer players' skill-related physical fitness, including their power, speed, balance, and agility. The core is the anatomic and functional center of the body as well as its "engine." All movements emanate from the center of the body and are transmitted to the extremities. The core muscles differ from the limb muscles because they frequently cocontract, thus making the torso hard to the point whereby all the muscles work together to become synergists. Theoretically, a strong core permits the passage of force from the lower body to the upper body with minimal energy loss in the torso. Based on the 26 studies, this review suggests that core training should be incorporated into the daily training sessions of soccer players, with a minimum frequency and length of 15 min per training session, twice per week, for 4 weeks.



#11 Seasonal analysis of match load in professional soccer players: An observational cohort study of a Swiss U18, U21 and first team

Reference: Front Physiol. 2023 Jan 4;13:1023378. doi: 10.3389/fphys.2022.1023378. eCollection 2022.

Authors: Linda Ammann, Stefan Altmann, Ludwig Ruf, Billy Sperlich

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Summary: The aim of this study was to quantify and compare various external match load measures in three age groups and leagues in male soccer (U18 in highest league of their age group vs U21 in fourth highest league vs first team in highest league). In this retrospective observational cohort study accelerations, decelerations, absolute and relative high-speed running as well as sprint distance, dynamic stress load, explosive distance, high intensity bursts total distance, high metabolic load (HML) distance, speed intensity, total distance, total time, and total loading were assessed in 416 individual player matches of 59 players. All these external load measures showed large inter-individual variability. At a group level, one-way ANOVAs or Kruskal-Wallis tests revealed statistically significant differences between the three teams for all measures analyzed (all p < 0.05), except accelerations. The first team displayed statistically significant higher dynamic stress load, explosive distance, HML distance, speed intensity, total distance and total loading compared to the two youth teams (all p < 0.05). The U18 featured statistically significant higher number of decelerations, absolute and relative high-speed running distance, high metabolic load distance, speed intensity, relative sprint distance, total distance, and total time than the U21, while for U21 higher dynamic stress load was observed than for U18 (all p < 0.05). Based on our data we conclude a routinely monitoring of match loads of different age groups and competitive settings to be required to 1) provide an indication of what players need to be prepared for, 2) track the athletic and match evolution, and 3) individually tailor training programs allowing players to fulfill the short- and long-term sport-specific requirements.



#12 The Relationship Between Subjective Wellness and External Training Load in Elite English Premier League Goalkeepers and a Comparison With Outfield Soccer Players

Reference: Int J Sports Physiol Perform. 2023 Jan 23;1-6. doi: 10.1123/ijspp.2022-0205. Online ahead of print.

Authors: Sophie Grimson, Gary Brickley, Nicholas J Smeeton, Adam Brett, Will Abbott

Summary: The aim was to investigate the relationship between training load and subjective wellness in English Premier League goalkeepers (GKs) and examine potential positional differences in subjective wellness. A total of 34 players (GK = 7, outfield = 27) completed a daily subjective wellness questionnaire assessing sleep quality, sleep hours, fatigue, mood, soreness, and total wellness over two and a half seasons. Ten-Hertz GPS devices were worn during training to calculate previous-day and 7-day total distance, player load, total dives, total dive load, average time to feet, and high, medium, and low jumps. All previous 7-day training loads were associated with all wellness markers (r = .073 to .278, P < .05). However, associations between previous 7-day dive load and mood, average time to feet, and both sleep quality and quantity, and between low jumps and sleep quality, were not significant. For previous-day metrics, total distance was associated with all wellness markers (r = .097 to .165, P < .05). In addition, player load and high jump were associated with fatigue, soreness, and wellness (r = .096 to .189, P < .05). Total dives and soreness were also related (r = .098, P < .05), and relationships were evident between average time to feet, medium jumps, and all wellness markers excluding sleep quality (r = .114 to .185, P < .05). No positional differences in subjective wellness occurred (P > .05). Some GK GPS variables are associated with subjective wellness, which could inform training-load prescription to maximize recovery and performance. In addition, GKs are no more vulnerable to poorer subjective wellness when compared with outfield players.



#13 Can prognostic factors for indirect muscle injuries in elite football (soccer) players be identified using data from preseason screening? An exploratory analysis using routinely collected periodic health examination records

Reference: BMJ Open. 2023 Jan 24;13(1):e052772. doi: 10.1136/bmjopen-2021-052772.

Authors: Tom Hughes, Richard Riley, Michael J Callaghan, Jamie C Sergeant

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Summary: In elite football, periodic health examination (PHE) may be useful for injury risk prediction. The objective was to explore whether PHE-derived variables are prognostic factors for indirect muscle injuries (IMIs) in elite players. 134 outfield elite male players from an English Premier League football club, over 5 seasons (1 July 2013-19 May 2018) were observed. The outcome was any time-loss, lower extremity index IMI (I-IMI). Prognostic associations were estimated using odds ratios (ORs) and corresponding statistical significance for 36 variables, derived from univariable and multivariable logistic regression models. Missing data were handled using multiple imputation. Non-linear associations were explored using fractional polynomials. During 317 participant-seasons, 138 I-IMIs were recorded. Univariable associations were determined for previous calf IMI frequency (OR 1.80, 95% CI 1.09 to 2.97), hamstring IMI frequency (OR 1.56, 95% CI 1.17 to 2.09), if the most recent hamstring IMI occurred >12 months but <3 years prior to PHE (OR 2.95, 95% CI 1.51 to 5.73) and age (OR 1.12 per 1-year increase, 95% CI 1.06 to 1.18). Multivariable analyses showed that if a player's most recent previous hamstring IMI was >12 months but <3 years prior to PHE (OR 2.24, 95% CI 1.11 to 4.53), this was the only variable with added prognostic value over and above age, which was a confirmed prognostic factor (OR 1.12 per 1-year increase, 95% CI 1.05 to 1.18). Allowing non-linear associations conferred no advantage over linear associations. PHE has limited use for injury risk prediction. Most variables did not add prognostic value over and above age, other than if a player experienced a hamstring IMI >12 months but <3 years prior to PHE. However, the precision of this prognostic association should be confirmed in future.



#14 Influence of the time-task constraint on ocular metrics of semi-elite soccer players

Reference: Sci Med Footb. 2023 Jan 27;1-8. doi: 10.1080/24733938.2023.2172203. Online ahead of print.

Authors: Vicente Luis-Del Campo, Jesús Morenas Martín, Juan Luis León Llamas, Juan Francisco Ortega Morán, Jesús Díaz-García, Tomás García-Calvo

Summary: This study novelty aimed to investigate the influence of manipulating the available time to perform the training tasks on soccer players´ ocular metrics, following training. Specifically, pupillary response (pupil diameter) and saccadic features (latency, accuracy, velocity, and number) were measured with a portable eye tracker following training to reflect the mental load accumulated by players during the training sessions. Nine semi-elite soccer players performed two training sessions, based on large-sided games, on an artificial grass field. These two sessions were composed of the same tasks but varying the required time to complete the task goals (Session 1: No time limitations to perform the tasks; Session 2: Limited time to perform the tasks). The participants performed, before (pre-test) and after (post-test) each training session, a prosaccade task in a room near the playing field. Findings revealed a differentiated effect of the available time to complete the training tasks on ocular metrics because significant differences were found in all variables after training (p < .001 for pupil diameter; p < .01 for saccade accuracy and number of saccades; p < .05 for saccade velocity and latency). Ocular metrics could be a promising tool to evaluate mental load following practice because they were sensitive to the time-task constraint, providing researchers a valuable information for a better planning of the mental workload when designed training tasks.



#15 Focus of Attention During ACL Injury Prevention Exercises Affects Improvements in Jump-Landing Kinematics in Soccer Players: A Randomized Controlled Trial

Reference: J Strength Cond Res. 2023 Feb 1;37(2):337-342. doi: 10.1519/JSC.0000000000004201. Epub 2021 Dec 23.

Authors: Nazanin Dalvandpour, Mostafa Zareei, Hamed Abbasi, Behrouz Abdoli, Mohammad A Mohammadian, Nikki Rommers, Roland Rössler

Summary: Anterior cruciate ligament tears are severe and complex knee injuries that commonly occur in soccer. Prevent injuries enhance performance (PEP) is an exercise-based prevention program to effectively reduce anterior cruciate ligament injuries. It is, however, unclear how the delivery of the program contributes to its effectiveness. Therefore, we aimed to investigate the effect of the focus of attention that was emphasized during the delivery of the PEP program on jump-landing kinematics in male, elite-level, U21 soccer players. Forty-two players participated in this randomized controlled trial and were allocated to (a) the internal focus of attention (IF) group, receiving instructions focusing on the execution of the exercise (b), the external focus of attention (EF) group, receiving instructions focusing on the outcome of the exercise, or (c) the control group. Before and after the 8-week intervention, players performed a jump-landing task during which we measured hip and knee angles at the initial contact, peak knee flexion, and peak vertical ground reaction force using a 3-dimensional motion analyzer. A repeated-measures analysis of variance was used to compare groups over time. Significant time-by-group interaction effects with large effect sizes were found for hip flexion at all moments (p < 0.032; η2 > 0.15) and for the knee flexion angle at initial contact and maximum knee flexion (p < 0.001; η2 > 0.35), all in favor of the EF group. This shows that EF during PEP improves hip and knee joint kinematics in the sagittal plane more than IF. Therefore, EF during PEP instructions is preferred to increase the effectiveness of this injury prevention program.



#16 Soccer academy practitioners' perceptions and application of bio-banding

Reference: PLoS One. 2023 Jan 26;18(1):e0274079. doi: 10.1371/journal.pone.0274079. eCollection 2023.

Authors: Chris Towlson, Demi Jo Watson, Sean Cumming, Jamie Salter, John Toner

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Summary: The primary aims of this study were to examine the application of maturity status bio-banding within professional soccer academy programmes and understand the methods employed, the intended objectives, and the potential barriers to bio-banding. Using a mixed method design, twenty-five professional soccer academy practitioners completed an online survey designed to examine their perceptions of the influence of maturation on practice, their perceptions and application of bio-banding, and the perceived barriers to the implementation of this method. Frequency and percentages of responses for individual items were calculated. In the next phase of the study, seven participants who had experience with, or knowledge of, the bio-banding process within an academy youth soccer setting were recruited to complete a semi-structured interview. Interview data was transcribed and analysed using a combination of deductive and inductive approaches to identify key themes. The main findings across the two phases of the study were that [1] there is consensus among the practitioners that the individual effect of maturation impacts their ability to accurately assess the soccer competencies, [2] the majority (80%) of the sample had implemented bio-banding, with practitioners showing a clear preference for using the Khamis and Roche method to bio-band players, with the greatest perceived benefit being during maturity-matched formats, specifically for late or post-PHV players, [3] Practitioners perceived that bio-banding enhances their ability to assess academy soccer players, and [4] practitioners who have used bio-banding believe that the method is an effective way of enhancing the perception of challenge thereby providing a number of psycho-social benefits. Findings suggest that a collaborative and multi-disciplinary approach is required to enhance the likelihood of bio-banding being successfully implemented within the typical training schedules across the adolescent phase of the player development pathway.



#17 A fully automatic method for segmentation of soccer playing fields

Reference: Sci Rep. 2023 Jan 26;13(1):1464. doi: 10.1038/s41598-023-28658-1.

Authors: Carlos Cuevas, Daniel Berjón, Narciso García

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Summary: This paper proposes a strategy to segment the playing field in soccer images, suitable for integration in many soccer image analysis applications. The combination of a green chromaticity-based analysis and an analysis of the chromatic distortion using full-color information, both at the pixel-level, allows segmenting the green areas of the images. Then, a fully automatic post-processing block at the region-level discards the green areas that do not belong to the playing field. The strategy has been evaluated with hundreds of annotated images from matches in several stadiums with different grass shades and light conditions. The results obtained have been of great quality in all the images, even in those with the most complex lighting conditions (e.g., high contrast between sunlit and shadowed areas). In addition, these results have improved those obtained with leading state-of-the-art playing field segmentation strategies.



#18 Predictive modeling of lower extremity injury risk in male elite youth soccer players using LASSO Regression

Reference: Scand J Med Sci Sports. 2023 Jan 26. doi: 10.1111/sms.14322. Online ahead of print.

Authors: Mathias Kolodziej, Andreas Groll, Kevin Nolte, Steffen Willwacher, Tobias Alt, Marcus Schmidt, Thomas Jaitner

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Summary: The purpose was to (1) identify neuromuscular and biomechanical injury risk factors in elite youth soccer players and (2) assess the predictive ability of a machine learning approach. Fifty-six elite male youth soccer players (age: 17.2 ± 1.1 years; height: 179 ± 8 cm; mass: 70.4 ± 9.2 kg) performed a 3D motion analysis, postural control testing, and strength testing. Non-contact lower extremities injuries were documented throughout 10 months. A least absolute shrinkage and selection operator (LASSO) regression model was used to identify the most important injury predictors. Predictive performance of the LASSO model was determined in a leave-one-out (LOO) prediction competition. Twenty-three non-contact injuries were registered. The LASSO model identified concentric knee extensor peak torque, hip transversal plane moment in the single-leg drop landing task and COP sway in the single-leg stance test as the three most important predictors for injury in that order. The LASSO model was able to predict injury outcomes with a likelihood of 58% and an AUC of 0.63 (sensitivity = 35%; specificity = 79%). The three most important variables for predicting the injury outcome suggest the importance of neuromuscular and biomechanical performance measures in elite youth soccer. These preliminary results may have practical implications for future directions in injury risk screening and planning, as well as for the development of customized training programs to counteract intrinsic injury risk factors. However, the poor predictive performance of the final model confirms the challenge of predicting sports injuries, and the model must therefore be evaluated in larger samples.







Between-match variation of peak match running intensities in elite football

The current study aimed to quantify the between-match variability in peak match running intensities across discrete moving average durations (1–10 min).





Comparison of training and match load between metabolic and running speed metrics of professional footballers by playing position

The aims of this study were to compare the training and match load of professional soccer players according to the playing position, and analyse the relationship between the metabolic and running speed metrics.





Latest research in football - week 2 - 2023

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 Game Weekly Frequency on Subjective Training Load, Wellness, and Injury Rate in Male Elite Soccer Players

Reference: Int J Environ Res Public Health. 2022 Dec 29;20(1):579. doi: 10.3390/ijerph20010579.

Authors: Rim Sioud, Raouf Hammami, Javier Gene-Morales, Alvaro Juesas, Juan C Colado, Roland van den Tillaar

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Summary: The aim was to compare the effects of playing one or two games per week on subjective perceived exertion (RPE) and (RPE-based) training load, monotony index, sleep, stress, fatigue, and muscle soreness (Hooper index), total mood disturbance, and injury rate in elite soccer players. Fourteen males from a first-division soccer club (age: 24.42 ± 4.80 years) competed in two games per week for six weeks and one game per week for twelve weeks (a total of 24 games). Paired t-tests and non-parametric Wilcoxon signed ranks evaluated the significance of the differences (p &lt; 0.05). The main findings were that RPE was significantly larger when playing two games per week compared with one game. However, subject total and mean training load, mood disturbance, monotony, and subjective perception of sleep, stress, fatigue, muscle soreness monitoring (Hooper index), and the number of injuries were not different. The findings suggested that competing in two matches per week does not negatively influence injury rate and players' perceptions of training load or wellness, even though players perceive two games per week as more physically demanding compared with one game per week.



#2 High Levels of PM10 Reduce the Physical Activity of Professional Soccer Players

Reference: Int J Environ Res Public Health. 2022 Dec 30;20(1):692. doi: 10.3390/ijerph20010692.

Authors: Michał Zacharko, Robert Cichowicz, Adam Depta, Paweł Chmura, Marek Konefał

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Summary: The aim of this study is to determine the impact of air quality, analyzed on the basis of the PM10 parameter in three regions of Poland, on the physical activity of soccer players from the Polish Ekstraklasa. The study material consisted of 4294 individual match observations of 362 players during the 2019/2020 domestic season. The measured indices included the parameter of air quality-PM10-and players' physical activities: total distance (TD) and high-speed running (HSR). Poland was divided into three regions (North, Central, South). The statistical analysis of particulate matter (PM) and athletes' physical activities, compared by region, revealed the effects in relation to the PM10 (H = 215.6566(2); p = 0.0001) and TD (H = 28.2682(2); p = 0.0001). Players performed better in regards to physical parameters in the North Region, where air pollution is significantly lower than in other regions. This means that even a short stay in more polluted regions can reduce the performance of professional footballers, which can indirectly affect the outcome of the match. Therefore, greater actions should be taken to improve air quality, especially through changes in daily physical activity, as this will reduce the carbon footprint.



#3 Effects of Virtual Reality Exercises versus Isokinetic Exercises in comparison with Conventional Exercises on the Imaging Findings and Inflammatory Biomarker Changes in Soccer Players with Non-Specific Low Back Pain: A Randomized Controlled Trial

Reference: Int J Environ Res Public Health. 2022 Dec 28;20(1):524. doi: 10.3390/ijerph20010524.

Authors: Gopal Nambi, Mshari Alghadier, Faizan Zaffar Kashoo, Osama R Aldhafian, Naif A Nwihadh, Ayman K Saleh, Mohamed A Omar, Tohamy G T Hassan, Mohamed Nagah Ahmed Ibrahim, Hassan Fathy El Behairy, Abdehamid A Attallah, Mohammed Abdelgwad Ismail

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Summary: Chronic non-specific low back pain (CNLBP) is the most common musculoskeletal problem. The purpose of this study was to investigate the effects of advanced physiotherapeutic exercise programs on imaging findings and inflammatory biomarkers in soccer players with CNLBP. In total, 60 CNLBP participants were divided into virtual reality exercise (VRE; n = 20), isokinetic exercise (IKE; n = 20), and conventional exercise (n = 20) groups. Pain intensity, imaging findings (muscle cross-sectional area (CSA) and muscle thickness), and changes in inflammatory biomarkers (CRP, TNF-α, IL-2, IL-4, and IL-6) were measured at baseline and after four weeks. After four weeks of intervention, there was a significant improvement (p = 0.001) in pain intensity for the VRE vs. IKE (0.7; CI 95% 0.38 to 1.07) and VRE vs. conventional (3.0 CI 95% 2.68 to 3.31) groups. The IKE group showed a greater number of significant changes in muscle CSA and muscle thickness than the other two groups (p &lt; 0.001). Moreover, the VRE group showed significant improvement in inflammatory biomarker measures compared with the other two groups (p &lt; 0.001). In CNLBP, virtual and isokinetic exercises had equal effects on reducing pain intensity. Isokinetic exercise is beneficial in increasing the muscle CSA and thickness, and virtual exercises are helpful for attenuating the inflammation process in soccer players with CNLBP.



#4 Contextualised high-intensity running profiles of elite football players with reference to general and specialised tactical roles

Reference: Biol Sport. 2023 Jan;40(1):291-301. doi: 10.5114/biolsport.2023.116003. Epub 2022 May 10.

Authors: Wonwoo Ju, Dominic Doran, Richard Hawkins, Mark Evans, Andy Laws, Paul S Bradley

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Summary: The present study aimed to contextualise physical metrics with tactical actions according to general and specialised tactical roles. A total of 244 English Premier League players were analysed by coding player's physical-tactical actions via the fusion of tracking data and video. Data were analysed across 5 general (Central Defensive Players = CDP, Wide Defensive Players = WDP, Central Midfield Players = CMP, Wide Offensive Players = WOP, Central Offensive Players = COP) and 11 specialised positions (Centre Backs = CB, Full-Backs = FB, Wing-Backs = WB, Box-to-Box Midfielders = B2BM, Central Defensive Midfielders = CDM, Central Attacking Midfielders = CAM, Wide Midfielders = WM, Wide Forwards = WF, Centre Forwards = CF). COP covered more distance at high-intensity (> 19.8 km · h-1) when performing actions such as 'Break into Box', Run in Behind/Penetrate', and 'Close Down/Press' than other positions (ES: 0.6-5.2, P < 0.01). WOP covered more high-intensity 'Run with Ball' distance (ES: 0.7-1.7, P < 0.01) whereas WDP performed more 'Over/Underlap' distance than other positions (ES: 0.9-1.4, P < 0.01). CDP and WDP covered more high-intensity 'Covering' distances than other positions (ES: 0.4-2.4, P < 0.01). Nonetheless, data demonstrated that implementing specialised positional analysis relative to a generalised approach is more sensitive in measuring physical-tactical performances of players with the latter over or underestimating the match demands of the players compared to the former. A contextualised analysis may assist coaches and practitioners when designing position or even player-specific training drills since the data provides unique physical-tactical trends across specialised roles.



#5 Positional and temporal differences in peak match running demands of elite football

Reference: Biol Sport. 2023 Jan;40(1):311-319. doi: 10.5114/biolsport.2023.116006. Epub 2022 May 10.

Authors: Bradley Thoseby, Andrew D Govus, Anthea C Clarke, Kane J Middleton, Ben J Dascombe

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Summary: Temporal changes in the total running demands of professional football competition have been well documented, with absolute running demands decreasing in the second half. However, it is unclear whether the peak match running demands demonstrate a similar decline. A total of 508 GPS files were collected from 44 players, across 68 matches of the Australian A-League. GPS files were split into the 1st and 2nd half, with the peak running demands of each half quantified across 10 moving average durations (1-10 min) for three measures of running performance (total distance, high-speed distance [> 19.8 km · h-1] and average acceleration). Players were categorised based on positional groups: attacking midfielder (AM), central defender (CD), defensive midfielder (DM), striker (STR), wide defender (WD) and winger (WNG). Linear mixed models and effect sizes were used to identify differences between positional groups and halves. Peak running demands were lower in the second half for STR across all three reported metrics (ES = 0.60-0.84), with peak average acceleration lower in the second half for DM, WD and WNG (ES = 0.60-0.70). Irrespective of match half, AM covered greater peak total distances than CD, STR, WD and WIN (ES = 0.60-2.08). Peak high-speed distances were greater across both halves for WIN than CD, DM and STR (ES = 0.78-1.61). Finally, STR had lower peak average acceleration than all positional groups across both halves (ES = 0.60-1.12). These results may help evaluate implemented strategies that attempt to mitigate reductions in second half running performance and inform position specific training practices.



#6 Hamstring muscle architecture and myotonometer measurements in elite professional football players with a prior strained hamstring

Reference: Biol Sport. 2023 Jan;40(1):93-99. doi: 10.5114/biolsport.2023.112092. Epub 2022 Jan 3.

Authors: F Javier Núñez, Juan Carlos Martínez, Jan-Arie Overberg, Nacho Torreno, Luis Suarez-Arrones

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Summary: The purpose of this study was to compare the fascicle length, angle pennation and mechanical properties of the biceps femoris long head (BFlh) in dominant and non-dominant limbs in previously injured and uninjured professional football players. Fifteen professional football players were recruited to participate in this study. Seven players had suffered a BFlh injury during the previous season. Myotonometry mechanical properties were measured in the proximal, common tendon and distal BFlh using MyotonPRO, and angle pennation and fascicle length were also measured. We observed significantly higher distal BFlh frequency, stiffness, decrement, relaxation and creep than in the common tendon and proximal BFlh. The previously injured players showed significantly higher frequency and stiffness, and lower relaxation and creep in the dominant BFlh than did uninjured players. There were no significant differences between the fascicle length and angle pennation in previously injured and uninjured BFlh. Myotonometric measurement provides a quick and inexpensive way to check the properties of the BFlh in professional football players. Professional football players with previous BFlh injury showed higher intrinsic tension and a poorer capacity to deform than did players with no injury to the BFlh.



#7 Development of novel calibration model(s) to predict whole-body density in professional football players

Reference: Sci Med Footb. 2023 Jan 17;1-9. doi: 10.1080/24733938.2023.2166680. Online ahead of print.

Authors: Claire Mills, Mark De Ste Croix, David James, Stephen-Mark Cooper 

Summary: Questions continue to be raised about the validity that is in existence to estimate Db, in professional male footballer players. Phase 1: n = 28 anthropometric variables were used on n = 206 footballers, using regression analyses to determine standard error of estimate and R2. A cut-off correlation coefficient set at r = 0.950 and 90% R2. Phase 2: all variables (z-scores, −x�- = 0.0, SD = ±1.0) to help reduce heteroscedasticity, β, r, t, significance of t and P-values were calculated. Phase 3: a forced stepwise-backwards regression analysis approach with nine predictors which met the acceptance criteria (r = 0.950, R2 = 90% and β weights) was used to develop a 'best fit' and a 'practical' calibration model. Phase 4: cross-validation of the two newly developed calibration method using LoA. The 'best fit' model SEM (0.115 g ml-1), the highest R2 (6.6%) (P ≤ 0.005), whereas the 'practical' calibration model SEM (0.115 g ml-1), R2 (4.7%) (P ≤ 0.005) with r values = 0.271 and 0.596 and R2 (%) coefficients = 0.3526 for the 'best fit' and 'practical' calibration models, respectively (P = 0.01). The two calibration models supported an ecologically and statistically valid contribution and can provide sound judgements about professional footballers' body composition.



#8 From Optical Tracking to Tactical Performance via Voronoi Diagrams: Team Formation and Players' Roles Constrain Interpersonal Linkages in High-Level Football

Reference: Sensors (Basel). 2022 Dec 27;23(1):273. doi: 10.3390/s23010273.

Authors: Nelson Caldeira, Rui J Lopes, Dinis Fernandes, Duarte Araujo

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Summary: Football performance behaviour relies on the individual and collective perceptual attunement to the opportunities for action (affordances) available in a given competitive environment. Such perception-action coupling is constrained by players' spatial dominance. Aiming to understand the influence of team formation and players' roles in their dynamic interaction (interpersonal linkages), Voronoi diagrams were used to assess the differences in players' spatial dominance resulting from their interactions according to ball-possession status in high-performance football. Notational (i.e., team formation, players' role, and ball-possession status) and positional data (from optical sensors) from ten matches of the men's French main football league were analysed. Voronoi diagrams were computed from players' positional data for both teams. Probability density functions of the players' Voronoi cell areas were then computed and compared, using the Kolmogorov-Smirnov test, for the different variables (i.e., team formation, player role, and ball-possession status) and their classes. For these variables, the players' Voronoi cell areas presented statistical differences, which were sensitive to team formation classes (i.e., defenders, midfielders, and forwards) and relative pitch location (interior or exterior in the effective play space). Differences were also found between players with similar roles when in different team formations. Our results showed that team formation and players' roles constrain their interpersonal linkages, resulting in different spatial dominance patterns. Using positional data captured by optical sensors, Voronoi diagrams can be computed into compound variables, which are meaningful for understanding the match and thus offer information to the design representative training tasks.



#9 Modulation of Oxidative Stress and Antioxidant Response by Different Polyphenol Supplements in Five-a-Side Football Players

Reference: Nutrients. 2022 Dec 30;15(1):177. doi: 10.3390/nu15010177.

Authors: Lucrecia Carrera-Quintanar, Lorena Funes, María Herranz-López, Néstor Vicente-Salar, Raul Bonet-García, Carles Blasco-Peris, Vicente Micol, Antoni Pons, Enrique Roche

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Summary: Oxidative stress is associated with playing soccer. The objective of the present report was to study the influence of different polyphenolic antioxidant-rich beverages in five-a-side/futsal players. The study was performed with a no supplemented control group (CG) and two supplemented groups with an almond-based beverage (AB) and the same beverage fortified with Lippia citriodora extract (AB + LE). At day 22, participants played a friendly futsal game. Blood extractions were performed at the beginning of intervention (day 1), before and after match (day 22) to determine oxidative stress markers and antioxidant enzyme activities in plasma, neutrophils and peripheral blood mononuclear cells (PBMCs). Malondialdehyde increased significantly in controls after the match in neutrophils, PBMCs and plasma compared to pre-match. Protein carbonyls also increased after the match in plasma in CG. In addition, malondialdehyde levels in neutrophils were significantly lower in the supplemented groups compared to controls. Post-match samples showed significant increases in neutrophil antioxidant activities in CG. Supplemented groups displayed variable results regarding neutrophil antioxidant activities, with superoxide dismutase activity significantly lower than in controls. Finally, post-match myeloperoxidase activity increased significantly in controls compared to pre-match and supplemented groups. In conclusion, polyphenolic antioxidant and anti-inflammatory supplements could be instrumental for optimal recovery after high intensity futsal games.



#10 Dietary Intake, Body Composition and Performance of Professional Football Athletes in Slovenia

Reference: Nutrients. 2022 Dec 24;15(1):82. doi: 10.3390/nu15010082.

Authors: Matjaž Macuh, Jana Levec, Nenad Kojić, Bojan Knap

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Summary: This is the first study to examine the nutritional status of professional Slovenian football players. This study aimed to analyze the dietary intake of elite football players during their preparation phase of the season and to investigate whether there is a relationship between energy and macronutrient intake with body composition and physical performance. Twenty-three footballers completed a three-day dietary and physical activity diary and underwent body composition measurements via bioelectrical impedance vector analysis (BIVA). Fifteen participants also took part in the Cooper treadmill test to assess their physical performance in correlation with their nutritional intake. Football players had an energy intake that was significantly too low for their needs, reflecting low energy availability. The average carbohydrate (CHO) intake was below the Union of European Football Associations (UEFA) recommendations, i.e., &lt;4 g CHO/kg body weight (BW). Additionally, players had adequate intakes of protein and fat, and inadequate intakes of saturated fat, fiber, calcium and vitamin D. There was a positive correlation between protein intake and lean body mass. Additionally, a negative correlation was observed between body fat mass and carbohydrate intake as well as between performance with the percentage of energy intake from fat. Results of this study highlight what aspects of nutrition might be improved upon in professional football players to maximize performance, longevity and body composition of athletes, as well as the necessity of a nutritionist role in this process.



#11 The Influence of Stud Characteristics of Football Boots Regarding Player Injuries

Reference: Int J Environ Res Public Health. 2022 Dec 30;20(1):720. doi: 10.3390/ijerph20010720.

Authors: Alejandro Castillo-Domínguez, Marcelino Torrontegui-Duarte, Joaquín Páez-Moguer, Álvaro Gómez-Del-Pino, Pablo Cervera-Garvi, Elena Mainer-Pardos, Demetrio Lozano, Jerónimo García-Romero

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Summary: The main aim of this study was to analyze the relationship between sole pattern parameters of football boots with the frequency of injuries that occur in semiprofessional and amateur footballers. The study sample was composed of 77 male football players. All were at least 18 years old, played at least 10 h per week, gave signed informed consent to take part and properly completed the Visual Analogue Scale. This study analysed data from each player's medical history, including age, injuries, years of practice, field type and surface condition information. The visual analogic score in semiprofessional players was higher (2.05 ± 2.43) than in amateur players (1.00 ± 1.1). A total of 141 lesions were collected, equivalent to 1.81 injuries for each football player studied (n = 77). The result of the ROC curve indicated that the player's years of practice could predict significantly (p &lt; 0.05) the presence of lower limb injuries, with an area under the curve of 0.714. This study described the predictive capacity of sole pattern characteristics concerning lower limb injuries in amateur and semiprofessional footballers. Football boot variables associated with the number of studs were associated with foot and ankle overload injuries.



#12 An After-School Football Session Transiently Improves Cognitive Function in Children

Reference: Int J Environ Res Public Health. 2022 Dec 22;20(1):164. doi: 10.3390/ijerph20010164.

Authors: Daniele Magistro, Simon B Cooper, Ruth Boat, Fabio Carlevaro, Francesca Magno, Cristian Castagno, Martina Simon, Giovanni Musella

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Summary: The aim of the present study was to evaluate the effect of a real-world after-school football session on subsequent cognitive function in primary school children. Following ethical approval, 100 children (aged 8-9 year) from the same after-school football club were randomly assigned to either an intervention (60 min football activity) or control (continued to rest) group. Cognitive function (selective visual attention, short term memory and long-term memory) was assessed prior to, immediately following and 45 min following the football session (and at the respective timepoints in the control group). Data were analysed via two-way (group * time) mixed methods ANOVA. The pattern of change in all domains of cognition over time, was different between the football and control groups (group * time, all p &lt; 0.001). Specifically, performance on all cognitive tasks was greater immediately following the football session in the intervention group compared to the control group (selective visual attention, p = 0.003; short-term memory, p = 0.004; long-term memory, p &lt; 0.001). However, there was no difference between the group 45 min following the football session (p = 0.132-0.393). These findings suggest that an after-school football session enhances cognition immediately post-activity in primary school children.



#13 Football-specific extension of the IOC consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020

Reference: Br J Sports Med. 2023 Jan 6;bjsports-2022-106405.  doi: 10.1136/bjsports-2022-106405.

Authors: Markus Waldén, Margo Mountjoy, Alan McCall, Andreas Serner, Andrew Massey, Johannes L Tol, Roald Bahr, Michel D'Hooghe, Natália Bittencourt, Francesco Della Villa, Michiko Dohi, Gregory Dupont, Mark Fulcher, Dina Christina Christa Janse van Rensburg, Donna Lu, Thor Einar Andersen

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Summary: Several sports have published consensus statements on methods and reporting of epidemiological studies concerning injuries and illnesses with football (soccer) producing one of the first guidelines. This football-specific consensus statement was published in 2006 and required an update to align with scientific developments in the field. The International Olympic Committee (IOC) recently released a sports-generic consensus statement outlining methods for recording and reporting epidemiological data on injury and illness in sport and encouraged the development of sport-specific extensions.The Fédération Internationale de Football Association Medical Scientific Advisory Board established a panel of 16 football medicine and/or science experts, two players and one coach. With a foundation in the IOC consensus statement, the panel performed literature reviews on each included subtopic and performed two rounds of voting prior to and during a 2-day consensus meeting. The panel agreed on 40 of 75 pre-meeting and 21 of 44 meeting voting statements, respectively. The methodology and definitions presented in this comprehensive football-specific extension should ensure more consistent study designs, data collection procedures and use of nomenclature in future epidemiological studies of football injuries and illnesses regardless of setting. It should facilitate comparisons across studies and pooling of data.



#14 The effect of neuromuscular injury reduction programs which contain neck exercises on the incidence of soccer-related head and neck injuries

Reference: J Athl Train. 2023 Jan 16. doi: 10.4085/1062-6050-0340.22. Online ahead of print.

Authors: Kerry Peek, Theo Versteegh, Stella Veith, Matt Whalan, Suzi Edwards, Marnee J McKay, Andrew Gardner

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Summary: There is growing concern among soccer players, coaches and parents regarding head and neck injuries, including concussion, particularly from heading a ball. Thus, creating a need to explore soccer-specific head injury risk reduction initiatives. One such initiative is to condition the neck musculature of young players by adding neuromuscular neck exercises into existing injury reduction exercise programs. The aim was to investigate the effect of neuromuscular neck exercises completed as part of an injury risk reduction exercise program on the incidence of soccer-related head and neck injuries in adolescent (12-18 years) soccer players. Two sports high School and six soccer clubs participated in this study with a total of 364 male and female soccer players, aged 12-18 years. We targeted one sports high school and two soccer clubs who completed neuromuscular neck exercises contained within an injury reduction program during training (Neck Training Group) as well as another sports high school and four soccer clubs who completed an injury reduction program but without neck exercise (Comparison Group) during the 2021 soccer season. Self-reported injury data were collected from each player at the end of the season and used to calculate incidence rate ratios (IRR) with 95% confidence intervals (95%CI). In total, 364 players completed the study, including 146 players in the Neck Training Group and 218 players in the Comparison Group. Despite players in the Neck Training Group being less likely to self-report a concussion (incidence rate ratio (IRR): 0.23 (95%CI 0.03-1.04) and pain on heading a ball (IRR:0.62 (95%CI 0.34-1.07), only lower incidence of potential concussive events (IRR:0.38 (95%CI 0.14-0.90); p<0.05) was significant. Integrating neuromuscular neck exercises into injury reduction exercise programs has the potential to reduce the risk of sustaining a potential concussive event, concussion and/or pain on heading a ball in adolescent soccer players.



#15 Acute Effects of Kinesio Taping on Functional Performance in Healthy Soccer Players: A Randomized, Controlled Crossover Trial

Reference: J Funct Morphol Kinesiol. 2022 Dec 20;8(1):2. doi: 10.3390/jfmk8010002.

Authors: Giuseppe Annino, Anas Alashram, Cristian Romagnoli, Emanuele Balducci, Marco De Paolis, Vincenzo Manzi, Elvira Padua

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Summary: This study aimed to investigate the acute effects of the Kinesio tape (KT) application on functional performance in healthy athletes. In this randomized, controlled crossover trial, a total of sixteen healthy soccer players (male = 14; age = 23.28 ± 3.13 years old) were assigned randomly into either KT over quadriceps, KT over hamstring, KT over quadriceps plus hamstring, or no intervention control condition. Four conditions were applied in a crossover design through three consecutive test sessions for each condition with a washout period of 2 days between the trials. Afterwards, all participants performed a 5-min warm-up routine and four sets of 30-s static stretching exercises for the hamstring and gluteal muscles for three consecutive treatment sessions. The running, jump, and flexibility tests were used to assess the functional performance of healthy athletes. A total of sixteen participants completed the study. No significant differences in the jump, flexibility, and running tests among the conditions were reported (p &gt; 0.05). These findings suggest that KT application has no acute effects in improving functional performance in healthy athletes. However, further studies with larger sample sizes are needed to verify our results.



#16 The Assessment of Ankle Range-of-Motion and Its Relationship with Overall Muscle Strength in a Cross-Section of Soccer Players

Reference: Sports (Basel). 2023 Jan 5;11(1):12. doi: 10.3390/sports11010012.

Authors: Piergiorgio Francia, Carlo Ferri Marini, Leonardo Bocchi, Barbara Piccini, Giuseppe Seghieri, Ario Federici, Sonia Toni, Francesco Lucertini

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Summary: Soccer (football) practice can induce a limitation of ankle range of motion (ROM) that is a possible risk factor for injury and other negative consequences over time. The main objective of this research was to investigate the effects of soccer practice on ankle ROM throughout the entire period of a sports career of soccer players (SP). Furthermore, the relationship between ankle ROM and muscle strength in SP of different ages was studied. A total of 204 SP (range 6.7-45.1 years) and 87 controls (range: 7.5-45.2 years) matched for age, body mass index (BMI), and gender, were assessed. Ankle ROM in both plantar flexion (APF) and dorsiflexion (ADF) in addition to handgrip strength (HGS) were evaluated using an inclinometer and the Jamar hydraulic hand dynamometer, respectively. The comparison between SP and control groups showed a significant reduction in ankle ROM of both APF (26.3 ± 7.2° vs. 32.6 ± 7.4°; d = -0.90; p &lt; 0.001) and ADF (95.5 ± 15.6° vs. 105.5 ± 15.8°; d = -0.66; p &lt; 0.001). In SP, the results of the ANOVAs test indicate that age had a significant effect on ADF (F = 4.352, p = 0.038, partial eta-squared (ηp2) = 0.015) but not on APF (F = 0.430, p = 0.746, ηp2 = 0.001). Moreover, considering only the SP, a weak inverse correlation between ADF and HGS group ADF was found (rs = -0.27; p &lt; 0.001). Factors such as the non-linear trend of growth in young SP could hinder the definition of the relationship between ankle ROM, age, and muscle strength. However, the appropriate consideration of age and muscle strength could facilitate the management of ankle ROM in PF of different ages.



#17 Risk Factors for Symptomatic Bilateral Lumbar Bone Stress Injury in Adolescent Soccer Players: A Prospective Cohort Study

Reference: Am J Sports Med. 2023 Jan 20;3635465221146289. doi: 10.1177/03635465221146289.

Authors: Toshiharu Tsutsui, Satoshi Iizuka, Seira Takei, Toshihiro Maemichi, Suguru Torii

Summary: Lumbar bone stress injury (BSI) is a high-risk long time-loss injury for adolescent soccer players. However, the risk factors for lumbar BSI are unclear. The purpose was to identify the risk factors for bilateral lumbar BSI for adolescent soccer players. Adolescent soccer players underwent orthopaedic examination, whole-body dual energy x-ray scan, lumbar magnetic resonance imaging (MRI), and muscle tightness testing at baseline. Lumbar lordosis (LL), sacral slope, maturity stage of lumbar vertebral body, and bone marrow edema (BME) at the L5 were examined via MRI. In addition, bone mineral density and content; trunk lean body mass via dual energy x-ray scan; and bilateral muscle tightness including the iliopsoas, hamstrings, and quadriceps were measured. Lumbar BSI was diagnosed as positive bilateral BME and extension-based lumbar pain. All participants were examined twice, one at 6 months and one at 1 year, after the baseline examination. Multivariate logistic regression analysis was performed to identify the risk factors for bilateral lumbar BSI. A total of 69 (26.3%) players were diagnosed with bilateral lumbar BSI. Asymptomatic BME (odds ratio [OR], 4.260; 95% CI, 2.153-8.431), apophyseal stage of the lumbar vertebral body (OR, 3.438; 95% CI, 1.698-6.959), sacral slope relative to LL ≥5° (OR, 4.067; 95% CI, 2.021-8.181), and hamstring tightness ≥50° (OR, 3.221; 95% CI, 1.385-7.489) were significantly associated with bilateral lumbar BSI. The incidence of bilateral lumbar BSI was common at 26.2%. Asymptomatic BME, sacral anterior tilt relative to LL, immature lumbar epiphyses, and hamstring tightness were found to be risk factors for bilateral lumbar BSI. The results of this study suggest that regular MRI examination could facilitate the early detection of BME, and improvement in hamstring flexibility and lumbosacral alignment may prevent bilateral lumbar BSI in young athletes.



#18 Sports, football and dermatology

Reference: J Eur Acad Dermatol Venereol. 2023 Feb;37(2):217. doi: 10.1111/jdv.18836.

Authors: Johannes Ring

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Do conditioning focused various-sided training games prepare elite youth male soccer players for the demands of competition?

This study aimed to compare the relative and peak demands of conditioning-focused various sided training games (VSG) to competition matches in elite youth male soccer players according to playing position.





The influence of maturity on recovery and perceived exertion, and its relationship with illnesses and injuries in young soccer players

The aim of this study was to investigate the association of internal load markers and recovery status with risk of illnesses and non-contact injuries in young soccer players characterised by different maturity status.





Latest research in football - week 1 - 2023

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 Monitoring training load in youth soccer players: effects of a six-week preparatory training program and the association between external and internal loads

Reference: Biol Sport. 2023 Jan;40(1):63-75. doi: 10.5114/biolsport.2023.112094. Epub 2022 Jan 3.

Authors: Sandra Lechner, Achraf Ammar, Omar Boukhris, Khaled Trabelsi, Jordan M Glenn, Jesper Schwarz, Omar Hammouda, Piotr Zmijewski, Hamdi Chtourou, Tarak Driss, Anita Hoekelmann

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Summary: This study examined the effects of a six-week preparatory training program on physical performance and physiological adaptations in junior soccer players. Additionally, we investigated whether a relationship existed between external and internal loads. Youth soccer players (aged 16 years old) from a youth football academy participated in six weeks of pre-conditioning training. Wireless Polar Team Pro and Polar heart rate sensors (H10) were used to monitor physical performance indicators (sprint and acceleration scores, covered distance, maximum and average speed and duration), physiological responses (maximum and average heart rate [HR] and R-R interval, time in HR zones 4+5, and heart rate variability [HRV]), and training load score. Additionally, muscle status and rating of perceived exertion (RPE) scores were measured using digital questionnaires. Significant increases were observed in the majority of physical performance indicators [i.e., sprints (p = 0.015, ES = 1.02), acceleration (p = 0.014, ES = 1), total distance (p = 0.02, ES = 0.87), as well as maximum speed (p = 0.02, ES = 0.87)]. A trend towards improvement was observed in the remaining performance indicators (i.e., distance/min and avg speed; ES = 0.6), training load (ES = 0.2), muscle status (ES = 0.3)), and all physiological responses parameters (ES = 0.1 to 0.6). Significant correlations were found between the majority of external load parameters (i.e., performance indicators) and objective (i.e., physiological responses) and subjective (i.e., RPE, muscle status) internal load parameters (p < 0.001). The highest number of moderate-large correlations were registered between performance indicators and time in HR zone 4+5 (0.58 < r < 0.82), training load (0.53 < r < 0.83), average HR (0.50 < r < 0.87), maximal HR (0.51 < r < 0.54) and average R-R interval (0.58 < r < 0.76). HR zone 4+5, average and maximal HR, average R-R interval, and training load score may help control training parameters and reduce the risk of under- or over-training in youth soccer players. However, these conclusions should be confirmed and replicated in future studies with more diverse subject populations.



#2 Body size, maturation and motor performance in young soccer players: relationship of technical actions in small-sided games

Reference: Biol Sport. 2023 Jan;40(1):51-61. doi: 10.5114/biolsport.2023.110749. Epub 2022 Jan 3.

Authors: Julio Cesar da Costa, Paulo Henrique Borges, Luiz Fernando Ramos-Silva, Vinicius Muller Reis Weber, Alexandre Moreira, Enio Ricardo Vaz Ronque

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Summary: The objective of this study was to investigate the relative contributions of body size, skeletal age, and motor performance variables with technical actions through an ecological model during small-sided soccer games, and the interaction of biological maturation with technical and motor performance in young players. In this cross-sectional study, eighty-two young players (14.4 ± 1.1 years), belonging to state-level soccer teams and divided by category (U-13 and U-15), were included. Players having an injury in the evaluation period were not included in the study. Measurements of body size, skeletal age (SA), motor tests, and technical actions in small-sided games (SSG) were performed (3 × 3 plus goalkeeper) in two periods (halves) of four minutes. Differences between age groups were found for SA (ES = -2.36), chronological age (ES = -3.89), body mass (ES = -2.09), height (ES = -1.90), and fat-free mass (ES = -2.09). Positive associations were found between body size (R = 0.43 to R = 0.48) and manipulation (R = 0.50 to R = 0.52) indicators and numbers of technical actions (CB and SS), except for stature with LB (R = -0.42) in the U-13 age group. In the U-15 category, skeletal age (R = -0.29 to R = -0.30) and body mass (R = -0.28 to R = -0.29) were negatively associated with the number of technical actions (RB, NB, LB, and OB) (P > 0.05) and positively with the balance with LB (R = 0.26). In conclusion, body size, SA, and motor performance influenced technical actions in SSG differentially in each category. U-13 heavier players and those with a better motor performance presented higher involvement due to the higher.



#3 Substitute running outputs in elite youth male soccer players: less peak but greater relative running outputs

Reference: Biol Sport. 2023 Jan;40(1):241-248.  doi: 10.5114/biolsport.2023.112969. Epub 2022 Mar 16.

Authors: Michael G Sydney, Martin Wollin, Dale Chapman, Nick Ball, Jocelyn K Mara

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Summary: Coaches consider substitute players to be a substantial factor in influencing the outcome of a soccer match. Substitute players are expected to make physical impact on the match by superseding the running output of the player they replaced and are a key tool for managing in-game fatigue and influencing the outcome of a game. This study investigated the physical impact and internal response of substitute players, compared to starting and full-match players. We also sought to determine if differences between substitution statuses were influenced by playing position. Players wore 15-Hz global positioning system tracking devices across 29 competition matches and were categorised according to their substitution status (full-match, starters, substitutes) and playing position (external defender, midfield, external attacker and central attacker). Peak total (TD) and high-speed running (> 5.0 m/s) distance (HSRD) were calculated using 1-, 2- and 5-minute rolling epochs. Relative running demands were reported as TD and HSRD per minute of total playing time. Substitute players performed less peak TD and HSRD in 1-, 2- and 5-minute epochs, and reported lower RPE compared to starting and full-match players. In contrast, substitutes performed greater relative HSRD per minute than starting and full-match players (p < 0.001, |d| range = 0.35-1.34). In conclusion, substitute players may have a relative physical impact but do not replicate or supersede the peak demands of full-match players. Coaches and practitioners should implement targeted warm-up interventions to enhance substitute readiness to meet the peak running demands in order to have a more effective physical impact.



#4 Effects of pitch size on soccer players' physiological, physical, technical, and tactical responses during small-sided games: a meta-analytical comparison

Reference: Biol Sport. 2023 Jan;40(1):111-147. doi: 10.5114/biolsport.2023.110748. Epub 2022 Jan 21.

Authors: Filipe Manuel Clemente, Gibson Moreira Praça, Rodrigo Aquino, Daniel Castillo, Javier Raya-González, Markel Rico-González, José Afonso, Hugo Sarmento, Ana Filipa Silva, Rui Silva, Rodrigo Ramirez-Campillo

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Summary: One of the most often-used task constraints in designing small-sided games (SSGs) is the manipulation of pitch size to promote increases or decreases in the relative area per player. Such adjustments cause changes in the acute responses during SSGs. This systematic review with meta-analysis aimed to compare the effects of smaller vs. larger pitch sizes on soccer players' physiological, physical, technical, and tactical responses during SSGs. Comparisons between smaller and larger pitches were not considered based on a specific size, but also between using at least two dimensions in the same comparative study, aiming to understand differences between using smaller and larger (independently of the specific dimensions). The data sources utilized were PubMed, PsycINFO, Scielo, Scopus, SPORTDiscus, and Web of Science. The database search initially yielded 249 titles. From those, 41 articles were eligible for the systematic review and meta-analysis. Results revealed that, compared to smaller pitches, SSGs played on larger pitches induced greater values for heart rate (p < 0.001; ES = 0.50), rate of perceived exertion (p < 0.001; ES = 0.70), total distance (p < 0.001; ES = 1.95), high-speed running (p < 0.001; ES = 1.20), stretch index (p < 0.001; ES = 1.02) and surface area (p < 0.001; ES = 1.54). No significant differences were found between pitch size regarding the numbers of accelerations (p = 0.232; ES = 0.45), decelerations (p = 0.111; ES = 0.85), passes (p = 0.897; ES = 0.02), dribbles (p = 0.823; ES = -0.05), or positional centroid (p = 0.053; ES = 0.56). Larger pitch sizes can be implemented as a meaningful task constraint to increase the internal and external load experienced by soccer players during SSGs, as well as to increase the dispersion of players while acting together. These results were found independent of format and age group.



#5 Injury incidence and risk factors in youth soccer players: a systematic literature review. Part II: Intrinsic and extrinsic risk factors

Reference: Biol Sport. 2023 Jan;40(1):27-49. doi: 10.5114/biolsport.2023.109962. Epub 2022 Jan 3.

Authors: Mauro Mandorino, Antonio J Figueiredo, Masar Gjaka, Antonio Tessitore

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Summary: Injury is defined as a complex phenomenon determined by the non-linear interaction of several intrinsic and extrinsic factors. The objective of the present study was to perform a systematic literature review on the injury risk factors in young soccer players. After electronic database searching, articles in line with the inclusion criteria were selected for the systematic review. Injury risk factor data were extracted and grouped in intrinsic and extrinsic risk factors. The main findings of the current review are as follows: (1) alteration in neuromuscular control such as limb asymmetry and dynamic knee valgus are important intrinsic risk factors; (2) maturation status may impair neuromuscular control and increase the risk of injury; (3) fatigue and poor recovery contribute to the onset of overuse injuries; (4) the impact of anthropometric factors is still unclear; (5) previous injuries increase the risk of re-injuries; (6) highly skilled players are more exposed to risk of injuries; (7) high external workloads increase the risk of injuries; (8) playing position, as well as sport specialization, exposes young soccer players to greater injury risk. Many factors (e.g., neuromuscular control, training load, maturity status) can modify the susceptibility to injury in young soccer players. Being aware of the complex interaction between these factors is essential to identify players at higher risk of injury, develop adequate prevention strategies, and from a scientific point of view move from a reductionist to a complex system approach.



#6 Warm-up optimization in amateur male soccer players: A comparison of small-sided games and traditional warm-up routines on physical fitness qualities

Reference: Biol Sport. 2023 Jan;40(1):321-329. doi: 10.5114/biolsport.2023.114286. Epub 2022 May 10.

Authors: Rohit K Thapa, Filipe M Clemente, Jason Moran, Felipe Garcia-Pinillos, Aaron T Scanlan, Rodrigo Ramirez-Campillo

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Summary: The aim of this study was to compare the effects of small-sided soccer games (SSSGs) and traditional warm-up (TWU) routines on physical fitness qualities in soccer players. Following a between-subject, randomized design, amateur-level soccer players were assigned to a SSSG warm-up (n = 10; age: 19.3 ± 2.8 years) or TWU group (n = 10; age: 19.3 ± 2.4 years). Players completed multiple trials of 10-m and 30-m linear sprints, change-of-direction speed (CODS) tests, and countermovement jumps (CMJ) prior to and following the warm-up routine. Separate mixed ANOVAs were performed to assess group effects (SSSG vs. TWU), time effects within each group (pre- vs. post-warm-up), and their interaction for each physical fitness quality. No significant interaction effects were observed for any dependent variable. Significant improvements were evident between baseline and follow-up measurements for 10-m sprint time (p = 0.002, Hedges' g effect size [g] = 0.59) and CMJ variables (height: p = 0.016, g = 0.20; power: p = 0.003, g = 0.19; force: p = 0.002, g = 0.14) in the TWU group and for CODS performance time (p = 0.012, g = 0.51) and CMJ variables (height: p < 0.001, g = 0.46; power: p = 0.002, g = 0.35; force: p = 0.001, g = 0.27) in the SSSG warm-up group. Both SSSG and TWU protocols improved selected physical fitness qualities with SSSG more effective at improving CODS and CMJ performance, and TWU more effective at improving linear speed. Soccer coaches may choose between SSSG or traditional warm-up activities according to player needs and preferences; however, the superior effects of SSSG suggest it might offer greater benefits than TWU in preparing players for optimal physical output.



#7 Elite young soccer players have smaller inter-limb asymmetry and better body composition than non-elite players

Reference: Biol Sport. 2023 Jan;40(1):265-272. doi: 10.5114/biolsport.2023.114840. Epub 2022 Apr 21.

Authors: Lucia Mala, Mikulas Hank, Petr Stastny, Frantisek Zahalka, Kevin R Ford, Piotr Zmijewski, David Bujnovsky, Miroslav Petr, Tomas Maly

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Summary: Body composition (BC) and inter-limb anthropometric asymmetries (LA) may influence the physical performance of soccer players. This study aimed to determine differences in BC and LA among soccer across four performance levels. The study involved 110 male soccer players participating in Czech senior teams who were grouped into four different performance levels (i.e. G1: national team, G2: 1st division, G3: 2nd division, G4: 3rd division). The following BC and LA parameters were compared among groups: body height, body mass, absolute fat-free mass, relative fat-free mass (FFMrel), percentage of fat mass (FM), total body water (TBW), intracellular water (ICW), extracellular water (ECW), phase angle, and bilateral muscle mass differences in the upper and lower extremities. Significant differences were observed in BC parameters among all groups (λ = 0.06, F75,246 = 5.38, p = 0.01, ηp 2 = 0.62). High-performance players (i.e. G1, G2) had significantly (p < 0.01) lower FM than lower performance players (i.e. G3, G4). The lowest values of FFMrel, relative TBW, relative ICW and ECW were detected in the lowest-performance players (i.e. G4). Significantly lower bilateral muscle mass differences were detected in G1 players (2.71 ± 1.26%; p < 0.01) compared with G4 players (3.95 ± 1.17%). G1 and G2 players had a higher proportion of muscle mass in the torso (p < 0.01) and upper limbs than G3 and G4 (p < 0.01). Elite and high-performance players have better BC and lower inter-limb anthropometric asymmetries compared with low-performance level players.



#8 Machine learning application in soccer: a systematic review

Reference: Biol Sport. 2023 Jan;40(1):249-263. doi: 10.5114/biolsport.2023.112970. Epub 2022 Mar 16.

Authors: Markel Rico-González, José Pino-Ortega, Amaia Méndez, Filipe Manuel Clemente, Arnold Baca

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Summary: Due to the chaotic nature of soccer, the predictive statistical models have become in a current challenge to decision-making based on scientific evidence. The aim of the present study was to systematically identify original studies that applied machine learning (ML) to soccer data, highlighting current possibilities in ML and future applications. A systematic review of PubMed, SPORTDiscus, and FECYT (Web of Sciences, CCC, DIIDW, KJD, MEDLINE, RSCI, and SCIELO) was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. From the 145 studies initially identified, 32 were fully reviewed, and their outcome measures were extracted and analyzed. In summary, all articles were clustered into three groups: injury (n = 7); performance (n = 21), which was classified in match/league outcomes forecasting, physical/physiological forecasting, and technical/tactical forecasting; and the last group was about talent forecasting (n = 5). The development of technology, and subsequently the large amount of data available, has become ML in an important strategy to help team staff members in decision-making predicting dose-response relationship reducing the chaotic nature of this team sport. However, since ML models depend upon the amount of dataset, further studies should analyze the amount of data input needed make to a relevant predictive attempt which makes accurate predicting available.



#9 A review of machine learning applications in soccer with an emphasis on injury risk

Reference: Biol Sport. 2023 Jan;40(1):233-239. doi: 10.5114/biolsport.2023.114283. Epub 2022 Mar 16.

Authors: George P Nassis, Evert Verhagen, João Brito, Pedro Figueiredo, Peter Krustrup

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Summary: This narrative review paper aimed to discuss the literature on machine learning applications in soccer with an emphasis on injury risk assessment. A secondary aim was to provide practical tips for the health and performance staff in soccer clubs on how machine learning can provide a competitive advantage. Performance analysis is the area with the majority of research so far. Other domains of soccer science and medicine with machine learning use are injury risk assessment, players' workload and wellness monitoring, movement analysis, players' career trajectory, club performance, and match attendance. Regarding injuries, which is a hot topic, machine learning does not seem to have a high predictive ability at the moment (models specificity ranged from 74.2%-97.7%. sensitivity from 15.2%-55.6% with area under the curve of 0.66-0.83). It seems, though, that machine learning can help to identify the early signs of elevated risk for a musculoskeletal injury. Future research should account for musculoskeletal injuries' dynamic nature for machine learning to provide more meaningful results for practitioners in soccer.



#10 Injury incidence and risk factors in youth soccer players: a systematic literature review. Part I: epidemiological analysis

Reference: Biol Sport. 2023 Jan;40(1):3-25. doi: 10.5114/biolsport.2023.109961. Epub 2022 Jan 3.

Authors: Mauro Mandorino, António J Figueiredo, Masar Gjaka, Antonio Tessitore

Summary: The analysis of the epidemiological data and the risk factors underlying injuries is crucial to promote prevention strategies in young soccer players. The objective of the present study was to perform a systematic literature review on the epidemiological data, described in the first part, and injury risk factors, presented in the second part. After electronic database searching, articles in line with the inclusion criteria were selected for the systematic review. Epidemiological data were extracted and discussed in this first part of the review. Data were grouped as follows: injury incidence, injury severity, and re-injury, injury types, injury mechanisms, and anatomical location. The principal findings of this first part of the review are as follows: (1) injury incidence is higher in older players and during matches than during training; (2) sex and maturity status may increase risk of injury; (3) male soccer players are more prone to muscle strains and ligament sprains while female players suffer more ligament sprains; (4) most injuries are located in the ankle and thigh in young male soccer players, and in the ankle and knee in female players; (5) severe injuries are less frequent but the incidence increases in older players. Re-injuries represent only a small percentage. Although soccer is considered a safe sport, many injuries are recorded in young soccer players every year. Injury predisposition changes in relation to age, sex, and biological age. Coaches and physical trainers should be aware of individual differences in order to promote prevention strategies and personalised training.



#11 Injury incidence and risk factors in youth soccer players: a systematic literature review. Part I: epidemiological analysis

Reference: Biol Sport. 2023 Jan;40(1):3-25. doi: 10.5114/biolsport.2023.109961. Epub 2022 Jan 3.

Authors: Mauro Mandorino, António J Figueiredo, Masar Gjaka, Antonio Tessitore

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Summary: The analysis of the epidemiological data and the risk factors underlying injuries is crucial to promote prevention strategies in young soccer players. The objective of the present study was to perform a systematic literature review on the epidemiological data, described in the first part, and injury risk factors, presented in the second part. After electronic database searching, articles in line with the inclusion criteria were selected for the systematic review. Epidemiological data were extracted and discussed in this first part of the review. Data were grouped as follow