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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. 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. 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. Injuries were negatively associated with player progression, and injury prevention and return-to-play strategies should be a priority for football academies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The aim of this article was to identify differences in the anthropometric and physiological characteristics of first team and reserve young soccer players (10-14 years old) at both the beginning and end of the soccer season. Body composition was calculated by measuring weight, height, skinfold, limb circumference, and joint diameter. [Vo.sub.2]max was estimated by Astrand's test. Sprint and jump tests were also performed. In general, first team players (FTPs) were taller and leaner. However, the most relevant difference that we found at the beginning of the season was that FTPs had shorter sprint times than reserves in the 30-m test (both flat and with 10 cones). Moreover, these differences in sprint time were more marked at the end of the season. In addition, jump test performance by the reserves declined from the beginning to the end of the season. These results indicate that sprint time is an important factor associated with selection as an FTP between the ages of 10 and 14 years. The progression of the FTPs during the course of the season is better than that of the reserves and is associated with a different degree of growth and maturity. These findings should be taken into account by trainers and coaches to avoid a bias against late maturing or younger soccer players. KEY WORDS development, anthropometry, physical fitness, speed

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. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the study was to ascertain the influence of relative age on entry to a professional soccer club and on long-term career attainment. Methods: We analysed the birth dates (divided into four birth quarters, BQ) and the career attainment of 1071 soccer players who entered their club in the under 12 (U12), U14, U16, U19, Reserves and First Team groups. Results: There was an overrepresentation of players born in BQ1 in all groups except from the Reserves and First Team. Forty players (4.7%) became professional, 18 born in BQ1 and 9 in BQ4. More players born in BQ4 who had entered the club in the U12 and U14 groups became professional, compared to players born in the rest of the quarters. The odds for a player born in BQ4 to become professional were 3 times larger, 95% CI [1.38, 6.56] than players born in the rest of the BQs. Conclusions: The overrepresentation of relatively older players is evident among players that entered the club at younger ages. Although this overrepresentation declines with increasing age, it influences career attainment. Interestingly, once relatively young players are within the club, their chances to become professional are larger. [ABSTRACT FROM AUTHOR]

Most studies of the relative age effect (RAE) refer to popular sports. In contrast, we examined to what extent the RAE is present in elite water polo players, as well as the association between handedness and RAE. For these purposes, laterality, anthropometry, month of birth, performance and playing position of participants in the 2011, 2013 and 2015 World Championships (623 women, 622 men) were analised. No RAE was observed in the total sample. However, the proportion of male left-handed field players born in the first quarter (11%) was lower than those born in the second (35.3%) and fourth quarter (29.4%). Regarding the overall laterality, the amount of left handed players was similar to the general population (10%). Nevertheless, there was a larger amount of left-handed wings than expected both in men (23.7%) and women (34.4%). Left-handed male players performed more shots, shots/minute and also scored more goals than right-handed players. Women left-handed players were younger and they performed more shots/minute. There is no RAE in elite male and female water polo players. However, laterality could be a possible moderator of the RAE particularly in left handed players, which should be taken into account in future studies. [ABSTRACT FROM AUTHOR]