Place Matters: A Study on the Influence of Birthplace and the Place of Development on Soccer Academy Players' Careers.

The effect of birthplace (the place where a player is born and grows up) is one of the key variables associated with soccer player development and achievement. However, recent studies have questioned the influence of contextual variables on selection and promotion processes related to birthplace. The main purposes of this study were: (1) establish whether there is a difference between the birthplace and sporting growth according to the stages of entry into the academy, (2) to evaluate the influence of geographical and contextual variables on sporting development, and (3) assess the chances of making a professional team debut. Applied logistic regression was used in order to analyse the birthplace and growth of 1411 male soccer players, of which 40.1% are incorporated in the U-12 category from a Spanish First division club, and the results showed a statistically significant association between a change from one's birthplace to the place of sporting growth and later success (79%). Key contextual variables such as number of inhabitants, population density, proximity to sports facilities, average household income and presence of sports clubs have been considered. The analysis of the contextual variables revealed that there was a positive relationship between certain variables, like a higher population, and being selected for the academy (p < 0.01; r = 0.28). Finally, the findings showed that players who experienced a geographical transition were 38% more likely to make a professional debut. The importance of considering the place of sporting growth when analysing the "birthplace effect" has therefore been demonstrated.

Acute pre- and post-competitive soccer match-play changes in neuromuscular factors, physical performance, and muscle response in youth male players.

There is a paucity of literature analyzing the impact of fatigue from actual competitive soccer match-play on measures of neuromuscular function and muscle damage markers in youth players. Aims The main purpose was to analyze the acute pre- and post-competitive soccer match-play changes in measures of landing mechanics, stretch-shortening cycle capability, physical performance, muscle damage, and match intensity. A secondary purpose was to explore whether the players' maturity status and chronological age were associated with post-soccer match-play responses. Methods Thirty-two male youth outfield soccer players from two chronological competition age groups (U14 and U16) were assessed pre-and post-competitive soccer match-play for 2D dynamic knee valgus at landing (DKV), leg stiffness, reactive strength index, 20 m sprint time, CMJ-Abalakov jump height, creatine kinase and urea activity and visual analogue scale for muscle soreness (VAS). Players' maturity status was also estimated using a previously validated regression equation. Results There were statistically significant (p < 0.05) post-competitive soccer match-play impairments in all measures of stretch-shortening cycle capability and muscle damage markers assessed irrespective of the age group. Likewise, significant post-match play alterations in landing mechanics (DKV of the dominant leg) and physical performance (sprint time and jump height) scores were documented for the U14 players. Significant interactions between maturity and landing mechanics and VAS responses to competitive soccer match-play were also found whereby more mature players demonstrated larger post-match changes. Conclusion The findings of this study suggest the existence of a negative influence of competitive match-play on neuromuscular function and muscle damage in youth soccer.

Estimating Maturity Status in Elite Youth Soccer Players: Evaluation of Methods.

PURPOSE: The objective of this study is to evaluate the concordance of predicted maturity status classifications (pre-, circa-, or post-peak height velocity (PHV)) relative to observed age at PHV in youth soccer players. METHODS: Longitudinal height records for 124 male soccer players were extracted from academy records spanning the 2000 to 2022 seasons. Age at PHV for each player was estimated with the Superimposition by Translation and Rotation model. Players were classified as pre-, circa-, or post-PHV using both ±1- and ±0.5-yr criteria to define the circa-PHV interval. Maturity status was estimated with several prediction protocols: maturity offset (Mirwald, Moore-1, Moore-2), maturity ratio (Fransen), and percentage of predicted adult height (PAH%) using the Khamis-Roche and Tanner-Whitehouse 2 equations using several bands: 85% to 96%, 88% to 96%, 88% to 93%, and 90% to 93% for the circa-PHV interval, and visual evaluation of individual growth curves alone or with PAH% based on Khamis-Roche and Tanner-Whitehouse 2. Concordance of maturity status classifications based on complete growth curves and predicted estimates of maturity status was addressed with percentage agreement and Cohen's kappa. RESULTS: Visual evaluation of the growth curves had the highest concordance (≈80%) with maturity status classifications (pre-, circa-, post-PHV) based on longitudinal data for individual players. Predicted maturity offset with the Mirwald, Moore-1, and Fransen equations misclassified about one-third to one-half of the players, whereas concordance based on PAH% varied with the band used, but not with the method of height prediction. CONCLUSIONS: Visual assessment of the individual growth curves by an experienced assessor provides an accurate estimate of maturity status relative to PHV. Maturity offset prediction equations misclassify the majority of players, whereas PAH% provides a reasonably valid alternative.

The combined effects of growth and maturity status on injury risk in an elite football academy.

This study aimed to explore the interaction between growth rate on specific injury incidence and burden on pre-, circa- and post-peak height velocity (PHV) periods. Injury and stature data collected during the 2000-2020 seasons in an elite football academy were retrospectively analysed. Only players with height measurements from childhood until the attainment of adult height were included in the study (N = 84). Growth data were smoothed using a cubic spline to calculate daily growth rate and height. Growth rate was categorised into three groups: fast (> 7.2 cm/year), moderate (3.5-7.2 cm/year) and slow (< 3.5 cm/year). Percentage of observed adult height was used to classify players as pre-PHV (< 88%), circa-PHV (88-95%) or post-PHV (> 95%). Overall and specific injury incidence and burden and rate ratios for comparisons between growth rate groups were calculated on pre-, circa- and post-PHV periods, separately. Overall injury incidence and burden were greater in pre-PHV players with quicker growth rates compared to players growing moderately and slowly. All in all, players with more rapid growth-rates were at higher risk for growth-related injuries in all pre-, circa- and post-PHV periods. Post-PHV, the incidence and burden of joint/ligament injuries were 2.4 and 2.6-times greater in players growing slowly compared to players growing moderately. Practitioners should monitor growth rate and maturity status and consider their interaction to facilitate the design of targeted injury risk reduction strategies.

Lost in transition: Exploring injury risk in academy footballers shifting between the second and first teams.

OBJECTIVES: To compare the injury profiles of football players shifting between second and first teams with those of second- and first-team players, and to examine the opinions of shifting players. DESIGN: Prospective cohort study. METHODS: 170 male players from Athletic Club (second team = 90, shifting = 20, first team = 60) were followed over eight seasons. Injuries and exposure time were recorded following the FIFA consensus, and 18 shifting players answered a seven-item questionnaire on their experience. RESULTS: 35 % shifting players became full-time first-team players, in contrast to only 8 % of second-team players (odds ratio = 6.4, p < 0.01). There were no differences in the overall injury incidence, but the overall burden of injuries was higher in second-team (172 days lost/1000 h) and shifting players (194 days lost/1000 h) compared with first-team players (114 days lost/1000 h, p < 0.01). Shifting players had a higher burden of knee joint/ligament injuries compared with first-team players (137 vs. 18 days lost/1000 h, p < 0.01) and anterior cruciate ligament (ACL) ruptures (122 vs. 10 days lost/1000 h, p < 0.01). There was a trend towards a higher burden of ACL ruptures in shifting players than in second-team players (122 vs. 41 days lost/1000 h, p = 0.07). Shifting players reported constant pressure and better communication with the second-team coaching staff than with the first-team staff. CONCLUSIONS: The high burden of injuries in shifting players, particularly from ACL ruptures, highlights the need for action. Ensuring high-quality communication between second- and first-team staff remains a key challenge.

Competitive season effects on polyunsaturated fatty acid content in erythrocyte membranes of female football players.

BACKGROUND: An optimal and correctly balanced metabolic status is essential to improve sports performance in athletes. Recent advances in omic tools, such as the lipid profile of the mature erythrocyte membranes (LPMEM), allow to have a comprehensive vision of the nutritional and metabolic status of these individuals to provide personalized recommendations for nutrients, specifically, the essential omega-3 and omega-6 fatty acids, individuating deficiencies/unbalances that can arise from both habitual diet and sportive activity. This work aimed to study the LPMEM in professional female football players during the football season for the first time and compare it with those defined as optimal values for the general population and a control group. METHODS: An observational study was carried out on female football players from the Athletic Club (Bilbao) playing in the first division of the Spanish league. Blood samples were collected at three points: at the beginning, mid-season, and end of the season for three consecutive seasons (2019-2020, 2020-2021, and 2021-2022), providing a total of 160 samples from 40 women. The LPMEM analysis was obtained by GC-FID by published method and correlated to other individual data, such as blood biochemical parameters, body composition, and age. RESULTS: We observed a significant increase in docosahexaenoic acid (DHA) (p 0.048) and total polyunsaturated fatty acid (PUFA) (p 0.021) in the first season. In the second season, we observed a buildup in the membrane arachidonic acid (AA) (p < .001) and PUFA (p < .001) contents when high training accumulated. In comparison with the benchmark of average population values, 69% of the football players showed lower levels of omega-6 dihomo-γ-linolenic acid (DGLA), whereas 88%, 44%, and 81% of the participants showed increased values of AA, eicosapentaenoic acid (EPA), and the ratio of saturated and monounsaturated fatty acids (SFA/MUFA), respectively. Regarding relationships between blood biochemical parameters, body composition, and age with LPMEM, we observed some mild negative correlations, such as AA and SFA/MUFA ratio with vitamin D levels (coefficient = -0.34 p = .0019 and coefficient = -.25 p = .042); DGLA with urea and cortisol (coefficient = -0.27 p < .006 and coefficient = .28 p < .0028) and AA with age (coefficient = -0.33 p < .001). CONCLUSION: In conclusion, relevant variations in several fatty acids of the membrane fatty acid profile of elite female football players were observed during the competitive season and, in comparison with the general population, increased PUFA contents were confirmed, as reported in other sportive activities, together with the new aspect of DGLA diminution, an omega-6 involved in immune and anti-inflammatory responses. Our results highlight membrane lipidomics as a tool to ascertain the molecular profile of elite female football players with a potential application for future personalized nutritional strategies (diet and supplementation) to address unbalances created during the competitive season.

An injury burden heat map of all men's and women's teams of a professional football club over a decade.

The aim was to present a descriptive 10-season summary of injury data from all teams of a professional football club using a heat map approach. Injuries and exposure time were registered according to the FIFA consensus in all men's and women's teams from Athletic Club over 10 seasons. A team-by-injury table was created, showing the incidence, median severity, and burden in each cell. Cells were coloured based on the injury burden value using a green - yellow-red gradient (lowest to highest). The highest overall injury burden was found in the women's 2nd and 1st teams and the men's U(under)17 team (>200 days lost/1000 h). Muscle injury burden demonstrated an increasing pattern with age. Knee joint/ligament injuries, particularly anterior cruciate ligament ruptures, had the highest impact on women's teams, followed by the men's 2nd team. In comparison, ankle joint/ligament injuries had a relatively low injury burden in most teams. Growth-related injuries were the most impactful injuries in the men's U15 and younger teams, and the women's U14 team. In conclusion, epidemiological data on injuries can inform and guide injury management processes. New and improved visualization methods might be important assets when presenting injury data to key decision-makers.

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

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

The burden of injuries according to maturity status and timing: A two-decade study with 110 growth curves in an elite football academy.

Injuries have a negative impact on the development of football players. Maturation is a potential risk factor for football injuries but available data on this topic provide limited evidence due to methodological shortcomings. The aim of this study was to describe the injury burden of male academy football players according to growth curve-derived maturity status and timing. Injury and growth data were collected from 2000 to 2020. Longitudinal height records for 110 individual players were fitted with the Super-Imposition by Translation and Rotation model to estimate age at peak height velocity (PHV). Players were clustered according to maturity status (pre-, circa-, post-PHV, or adults) and timing (early, on-time, late maturers). Overall and specific injury burdens (days lost/player-season) and rate ratios for comparisons between groups were calculated. Overall injury burden increased with advanced maturity status; pre-PHV players had 3.2-, 3.7-, and 5.5-times lower burden compared with circa-PHV, post-PHV, and adult players, respectively. Growth-related injuries were more burdensome circa-PHV, while muscle and joint/ligament injuries had a higher impact post-PHV and in adults. Further, in the pre-PHV period, late maturers showed lower burden of overall, growth-related, anterior inferior iliac spine osteochondrosis, and knee joint/ligament injuries compared with on-time maturers. In adult players, however, injuries were less burdensome for early maturers than on-time and late maturers. In addition, joint/ligament injuries of adult late maturers were 4.5-times more burdensome than those of early maturers. Therefore, monitoring maturity seems crucial to define each player's maturation profile and facilitate design of targeted injury prevention programmes.Highlights Injury burden is significantly lower in football players at pre-peak height velocity (PHV). Growth-related injuries are most burdensome circa-PHV, while muscle and joint/ligament injuries are more burdensome post-PHV and especially in adults.Before PHV, growth-related and knee joint/ligament injuries have lower burden in players who mature late than those who mature on-time. Adult late maturers have greater burden of overall and joint/ligament injuries than early maturers.Football academies should regularly assess the maturity status and timing of young football players, as the impact of injuries varies with maturation status and timing.Management of the maturity-related injury risk profile, in combination with other relevant factors (training load, neuromuscular and biomechanical factors, physiotherapy, coaching, communication, psychosocial factors …), might help improve the success of player development programmes and protect the health of young football players.

Peak Height Velocity Affects Injury Burden in Circa-PHV Soccer Players.

Growth and maturation are potential risk factors for soccer injuries. This research sought to describe how peak height velocity (PHV) affects overall and specific injury burden in circa- and post-PHV elite academy soccer players. Injuries and growth data collected from 2000 to 2020 were studied retrospectively. Longitudinal height records for 124 players were fitted with the Super-Imposition by Translation and Rotation model to calculate PHV (cm/year) and age at PHV. Players were classified according to PHV percentile (fast:≥75th; average: 25-75th; slow:≤25th) and maturity status (circa- or post-PHV). Overall and specific injury burden (days lost/player-season) and rate ratios for comparisons between groups were calculated based on zero-inflated negative binomial models. Confidence intervals were calculated at the 95% confidence level (CI) and the significance level was set at<0.05. In circa-PHV, players with fast PHV had 2.6 (CI: 1.4-4.8)- and 3.3 (CI:1.3-6.7)-times higher overall burden and 2.9 (CI:1.1-7.1)- and 4.1 (CI: 1.4-15.2)-times higher for growth-related injury burden compared to players with average and slow PHV, respectively. Regular monitoring of growth seems important to detect players at higher risk for being disrupted by growth-related injuries.

Injuries are negatively associated with player progression in an elite football academy.

BACKGROUND: The aim was to investigate the association of injuries with male football player continuity, progression and chances of reaching the First team in an elite academy. METHODS: Injuries and exposure time were prospectively recorded, following the FIFA guidelines, over 6 seasons (2011-2017) in Under (U)12, U14, U16, U19, 2nd/3rd team and First team players from the same professional football club. RESULTS: U19 and 2nd/3rd team players progressing to the next level had a lower injury burden and higher match availability compared to players that did not progress. Injury burden was lower in players progressing from U12 to U14. All players progressing from the 2nd/3rd teams to the First team had a match availability higher than 84% and did not suffer an anterior cruciate ligament (ACL) rupture or an injury requiring over 200 (+200) days to return to play. In U19 and 2nd/3rd team players, injuries requiring +100 and +200 days to return to play, ACL ruptures and groin pain, but not hamstring and ankle ligament injuries, were associated with lower odds of continuing in the academy each season. CONCLUSION: Injuries were negatively associated with player progression, and injury prevention and return-to-play strategies should be a priority for football academies.

Relative skeletal maturity status affects injury burden in U14 elite academy football players.

Maturation progresses at different times and at different rates between individuals. Thus, differences in maturity status exist among players in the same chronological age-based category, especially in U14 players. The purpose of this prospective study was to describe injury burden according to the relative skeletal maturity status in U14 elite academy football players. From 2011 to 2020, injuries and individual exposure (training and match) were prospectively recorded in 183 male U14 players. Skeletal age (SA) was assessed using the Tanner-Whitehouse 2 method. Relative skeletal maturity status [SA minus chronological age (CA)] was classified as follows: early (SA-CA > 0.5), on-time (SA-CA ± 0.5), and late (SA-CA < -0.5). Overall and specific injury burden (days lost/1000 h) and rate ratios for comparisons between groups were calculated. Overall injury burden was 2.8 times higher (3.6 times in training) in early maturers compared with late maturers. Growth-related injuries were the most burdensome injuries in all three groups, but significant differences were not found between groups. Muscle injuries were 4 times more burdensome in early maturers compared with on-time and late maturers. Besides, joint/ligament injuries were 7 and 12 times less burdensome in late maturers than in on-time and late maturers, respectively. Significant differences between groups in overall and specific injury burden were not found in matches. Our results showed different injury patterns in U14 early, on-time, and late maturers. Hence, monitoring maturity seems crucial to detect potential injuries that cause the greatest disruption, and facilitate design of targeted injury prevention programs.

Injury risk is greater in physically mature versus biologically younger male soccer players from academies in different countries.

OBJECTIVES: To investigate if maturity status was associated with injury risk in male academy soccer players. DESIGN: Prospective cohort surveillance study. SETTING: Professional soccer academies. PARTICIPANTS: 501 players (aged 9-23 years) from eight academies in England, Spain, Uruguay and Brazil. MAIN OUTCOME MEASURES: Players were grouped by maturity offset as pre-peak height velocity (PHV), circa-PHV, post-PHV or adult. Injury prevalence proportion (IPP) and days missed were recorded for one season per player, with training/match exposure recorded in a sub-sample (n = 166). RESULTS: IPP for all injuries combined increased with advancing maturity, with circa-PHV (p = 0.032), post-PHV (p < 0.001) and adult (p < 0.001) higher than pre-PHV. IPP was higher in post-PHV and adult than pre-PHV for non-contact (p = 0.001 and p = 0.012), soft-tissue (both p < 0.001), non-contact soft-tissue (p < 0.001 and p = 0.005), muscle (both p < 0.001), thigh (both p < 0.001), ankle (p = 0.035 and p = 0.007) and hamstring injuries (p = 0.041 and p = 0.017). Ligament/tendon IPP was greater in adult versus pre-PHV (p = 0.002). IPP for growth-related injuries was lower in post-PHV than pre-PHV (p = 0.039). Injury incidence rates (n = 166) exhibited similar patterns to IPP in the full cohort. CONCLUSIONS: Injury patterns were similar between post-PHV and adult academy players but, crucially, relatively more of these groups suffered injuries compared to pre- and circa-PHV (except growth-related injuries).

Playing Position and the Injury Incidence Rate in Male Academy Soccer Players.

CONTEXT: Whether playing position influences injury in male academy soccer players (ASPs) is unclear. OBJECTIVE: To determine if playing position was associated with injury in ASPs. DESIGN: Descriptive epidemiology study. SETTING: English, Spanish, Uruguayan, and Brazilian soccer academies. PATIENTS OR OTHER PARTICIPANTS: A total of 369 ASPs from the under-14 to under-23 age groups, classified as post-peak height velocity using maturity offset, and grouped as goalkeepers, lateral defenders, central defenders, lateral midfielders, central midfielders, or forwards. MAIN OUTCOME MEASURE(S): Injuries were recorded prospectively over 1 season. Injury prevalence proportion (IPP), days missed, and injury incidence rate (IIR, injuries/1000 training or match hours, n = 116) were analyzed according to playing position. RESULTS: No association with playing position was observed for any injury type or location regarding IPP (P ≥ .089) or days missed (P ≥ .235). The IIR was higher in central defenders than in lateral defenders for general (9.30 versus 4.18 injuries/1000 h, P = .009), soft tissue (5.14 versus 1.95 injuries/1000 h, P = .026), and ligament or tendon injuries (2.69 versus 0.56 injuries/1000 h, P = .040). The central versus lateral or forward positions were not associated with IPP (P ≥ .051) or days missed (P ≥ .083), but general IIR was greater in the central position than the lateral or forward positions (8.67 versus 6.12 injuries/1000 h, P = .047). CONCLUSIONS: Academy soccer players' playing positions were not associated with IPP or days missed, but the higher general, soft tissue, and ligament or tendon IIRs in central defenders suggest that this position warrants specific attention regarding injury-prevention strategies. These novel findings highlight the importance of considering training or match exposure when investigating the influence of playing position on injury in ASPs.

The genetic association with injury risk in male academy soccer players depends on maturity status.

It is currently unknown if injury risk is associated with genetic variation in academy soccer players (ASP). We investigated whether nine candidate single nucleotide polymorphisms were associated (individually and in combination) with injury in ASP at different stages of maturation. Saliva samples and one season's injury records were collected from 402 Caucasian male ASP from England, Spain, Uruguay, and Brazil, whose maturity status was defined as pre- or post-peak height velocity (PHV). Pre-PHV COL5A1 rs12722 CC homozygotes had relatively higher prevalence of any musculoskeletal soft tissue (22.4% vs. 3.0%, p = 0.018) and ligament (18.8% vs. 11.8%, p = 0.029) injury than T-allele carriers, while VEGFA rs2010963 CC homozygotes had greater risk of ligament/tendon injury than G-allele carriers. Post-PHV IL6 rs1800795 CC homozygotes had a relatively higher prevalence of any (67.6% vs. 40.6%, p = 0.003) and muscle (38.2% vs. 19.2%, p = 0.013) injuries than G-allele carriers. Relatively more post-PHV EMILIN1 rs2289360 CC homozygotes suffered any injury than CT and TT genotypes (56.4% vs. 40.3% and 32.8%, p = 0.007), while the "protective" EMILIN1 TT genotype was more frequent in post- than pre-PHV ASP (22.3 vs. 10.0%, p = 0.008). Regardless of maturity status, T-alleles of ACTN3 rs1815739 and EMILIN1 rs2289360 were associated with greater absence following ankle injury, while the MMP3 rs679620 T-allele and MYLK rs28497577 GT genotype were associated with greater absence following knee injury. The combination of injury-associated genotypes was greater in injured vs. non-injured ASP. This study is the first to demonstrate that a genetic association exists with injury prevalence in ASP, which differs according to maturity status.

Putative Role of MCT1 rs1049434 Polymorphism in High-Intensity Endurance Performance: Concept and Basis to Understand Possible Individualization Stimulus.

Monocarboxylate transporters (MCTs) have been proposed as important mediators of the exchange between lactate (La-) producer and La- recipient (consumer) cells. Previous studies have suggested that the MCT1 A1470T genotype could be related to different physical performance phenotypes. This study followed the guidelines for Strengthening the Reporting of Genetic Association Studies (STREGA) and aimed to evaluate the distribution of the MCT1 polymorphism rs1049434 in endurance-trained athletes compared to the untrained population. Moreover, this study explored the potential influence of the polymorphism alleles phenotypes on high-intensity exercise performance. In a cross-sectional study fashion, a total of 85 triathletes from northern Spain were genotyped for MCT1 rs1049434 and compared to a control group of 107 healthy male participants (1000 Genomes Research Study for Iberian Populations in Spain). All athletes performed a 30 s Wingate all-out test (WAnT) on a cycle ergometer. Peak and mean power (absolute and relative) were measured. After verification of the Hardy-Weinberg equilibrium, the findings indicated that the MCT1 TT genotype was overrepresented in triathletes in comparison to the genotypic frequency of the general Spanish population. No significant associations were found between any MCT1 genotype and peak or mean power performance in the WAnT. Further studies are required to understand the relationship among MCT1 A1470T polymorphism, endurance-trained athletes, and high-intensity performance.

The relative age effect in young athletes: A countywide analysis of 9-14-year-old participants in all competitive sports.

The relative age effect (RAE) has primarily been investigated in male athletes involved in popular sports and high-level competitions. However, occurrence of RAE in other types of sports at the grassroots level, particularly in female athletes, is less well-studied. Thus, we examined the RAE in a large cohort of young athletes who participated in all competitive sports in Bizkaia, Spain, according to gender and specificity of the sport. The birth dates of 38,381 participants (65.1% males and 34.9% females) aged 9-14 years old in 37 competitive sports were analyzed. Birth dates were divided into four birth-quarters and compared to those of all children born in the same period using a χ2 goodness-of-fit test and standardized residuals. The effect size Cramer's V was measured, and odds ratio and 95% confidence intervals were calculated to determine the odds of athletes born in January playing in the highest leagues. In the total sample, in boys RAE was evident in football, but only in higher-competition leagues (p<0.001, large effect size). In girls, RAE was evident in the most popular team sports: basketball (p<0.001, large effect size in basketball 1st league), handball and football (p<0.05, both small effect sizes). Players born in January were 3.23- and 2.89-times more likely to play in the 1st leagues than those born in December, for boys (football) and girls (basketball) respectively. In the overall analysis and in the remaining sports, presence of RAE was negligible. Therefore, the date of birth does not seem to be a constraint to participating in most sports in Bizkaia. The potential mechanisms for RAE are multifactorial and complex, yet a combination of factors, such as the popularity of a sport and the depth of competition, physicality and social influences may be involved. We discuss these mechanisms and potential measures to mitigate RAE.

The GALNTL6 Gene rs558129 Polymorphism Is Associated With Power Performance.

Díaz, J, Álvarez Herms, J, Castañeda, A, Larruskain, J, Ramírez de la Piscina, X, Borisov, OV, Semenova, EA, Kostryukova, ES, Kulemin, NA, Andryushchenko, ON, Larin, AK, Andryushchenko, LB, Generozov, EV, Ahmetov, II, and Odriozola, A. The GALNTL6 gene rs558129 polymorphism is associated with power performance. J Strength Cond Res 34(11): 3031-3036, 2020-The largest genome-wide association study to date in sports genomics showed that endurance athletes were 1.23 times more likely to possess the C allele of the single nucleotide polymorphism rs558129 of N-acetylgalactosaminyltransferase-like 6 gene (GALNTL6), compared with controls. Nevertheless, no further study has investigated GALNTL6 gene in relation to physical performance. Considering that previous research has shown that the same polymorphism can be associated with both endurance and power phenotypes (ACTN3, ACE, and PPARA), we investigated the association between GALNTL6 rs558129 polymorphism and power performance. According to this objective we conducted 2 global studies regarding 2 different communities of athletes in Spain and Russia. The first study involved 85 Caucasian physically active men from the north of Spain to perform a Wingate anaerobic test (WAnT). In the second study we compared allelic frequencies between 173 Russian power athletes (49 strength and 124 speed-strength athletes), 169 endurance athletes, and 201 controls. We found that physically active men with the T allele of GALNTL6 rs558129 had 5.03-6.97% higher power values compared with those with the CC genotype (p < 0.05). Consistent with these findings, we have shown that the T allele was over-represented in power athletes (37.0%) compared with endurance athletes (29.3%; OR = 1.4, p = 0.032) and controls (28.6%; OR = 1.5, p = 0.015). Furthermore, the highest frequency of the T allele was observed in strength athletes (43.9%; odds ratio [OR] = 1.9, p = 0.0067 compared with endurance athletes; OR = 2.0, p = 0.0036 compared with controls). In conclusion, our data suggest that the GALNTL6 rs558129 T allele can be favorable for anaerobic performance and strength athletes. In addition, we propose a new possible functional role of GALNTL6 rs558129, gut microbiome regarding short-chain fatty acid regulation and their anti-inflammatory and resynthesis functions. Nevertheless, further studies are required to understand the mechanisms involved.

An injury audit in high-level male youth soccer players from English, Spanish, Uruguayan and Brazilian academies.

OBJECTIVES: To identify the most common injury types/locations in high-level male youth soccer players (YSP). DESIGN: Prospective cohort surveillance study. SETTING: Professional soccer club academies. PARTICIPANTS: Six hundred and twenty-four high-level male YSP [Under 9 (U9) to U23 year-old age groups] from academies in England, Spain, Uruguay and Brazil. MAIN OUTCOME MEASURES: Injury type, location and severity were recorded during one season. Injury severity was compared between age groups, while injury type and location were compared between nations. RESULTS: Four hundred and forty-three training or match injuries were recorded, giving an injury rate of 0.71 per player. Non-contact injuries were most common (58.5%), with most (44.2%) resolved between 8 and 28 days. Most injuries (75.4%) occurred in the lower limbs, with muscle (29.6%) the most commonly injured tissue. U14 and U16 suffered a greater number of severe injuries relative to U12 and U19/U20/U23/Reserves. Tendon injury rate was higher in Brazil vs. Spain (p < 0.05), with low back/sacrum/pelvis injury rate highest in Spain (p < 0.05). CONCLUSIONS: The proportion of severe injuries in U14 and U16 suggests YSP injury risk is maturation-dependent. Minimal differences in type and location between high-level YSP from four different countries suggest injury rates in this population are geographically similar.

Muscle injuries in the academy of a Spanish professional football club: A one-year prospective study / Lesiones musculares en las distintas categorías de un club profesional de futbol Español: estudio prospectivo de una temporada

Introduction: Due to its high incidence, muscle injury is one of the major problems for football players. The aim was to analyse the rate and characteristics of muscle injuries in the academy of a Spanish professional football team (Spanish First Division) during a complete competitive season (2015-2016) using a prospective cohort design. Material and methods: Time-loss injuries and exposure time were recorded following the UEFA consensus in 139 elite young football players from 4 levels (Senior, U19, U16 and U14) over one season. Results: A total of 118 injuries were recorded. Overall injury incidence was 1.47 muscle injuries/1000h, with a lower incidence in younger players. Nevertheless, injury burden (days lost/1000h) was similar between levels. The injuries with the highest incidence and burden were hamstring and adductor injuries in Senior (50 and 58 days respectively), hamstring injuries in U19 and U16 (109 vs 89), and adductor injuries in U14 (175 days). Regarding the severity of injuries, it was observed that moderate injuries were the most common injuries and muscle injuries during competition had a higher incidence towards the end of the matches (75-90′). Conclusions: Muscle injury prevention strategies are necessary in players from all levels and should be adapted to their specific needs, with hamstring and adductor injuries being the main problem in the present study (AU)

Introducción: Debido a su elevada incidencia, las lesiones musculares son uno de los principales problemas para los futbolistas a lo largo de su carrera profesional. El objetivo de este estudio fue analizar la incidencia lesional y las características de las lesiones musculares de la cantera de un equipo de fútbol profesional (primera división española) durante una temporada completa (2015---2016). Material y métodos: Se registraron las lesiones y el tiempo de exposición de 139 jugadores de fútbol de 4 categorías (sénior, U19, U16 y U14) durante una temporada siguiendo los criterios UEFA. Resultados: Un total de 57 lesiones musculares fueron registradas. La incidencia lesional fue de 1,47 lesiones musculares/1.000 h, siendo esta incidencia menor cuanto menor era la categoría. No obstante, las consecuencias en forma de días de baja/1.000 h fueron similares entre categorías. Las lesiones más comunes y las que produjeron el mayor número de días de baja fueron las de isquiosurales y aductores en los sénior (50 y 58 días, respectivamente), las de isquiosurales en U19 y U16 (109 vs. 89 días), y las de aductores en U14 (175 días). Además, las lesiones moderadas fueron las más comunes y las lesiones musculares producidas en competición tuvieron una mayor incidencia hacia la fase final de los partidos (75-90 min). Conclusiones: Las estrategias preventivas de lesiones musculares son necesarias en futbolistas de todas las categorías y deben ser adaptadas a sus necesidades específicas, siendo las lesiones de isquiosurales y aductores el mayor problema para los jugadores del presente estudio (AU)