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Football is a popular sport, but little is known about the youth-to-senior transition rates in elite players, particularly in large and successful countries. This study aims to investigate the youth-to-senior transition rate in the Italian national football team, both prospectively and retrospectively, and to explore if Relative Age Effects (RAEs) affect this transition. Data from 885 players selected in youth and senior Italian national teams between 2000 and 2021 were included in the study. For each player, the birthdate and the number of selection in Under 16, 17, 19, 21 and senior team was considered. The 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. Prospectively, the transition rate increased as age increased (i.e., from ~20% in U16 to ~50% in U19). Retrospectively, less than 10–20% of youth players were subsequently selected for the senior team. Data revealed a skewed birth date distribution in all age groups, and the RAEs magnitude decreased when age increased (i.e., ORs for Q1 vs Q4 was ~ 9 in U16 and ~ 1.7 in senior teams). Nevertheless, the RAE magnitude was smaller for successfully transitioned players. In conclusion, most players in the senior team were not previously selected for youth teams suggesting that junior international experience may not be a prerequisite for later success. Moreover, while the birthdate strongly influences the selection of youth national teams, its impact is less evident in the youth-to-senior transition. [ABSTRACT FROM AUTHOR]

The relative age effect (RAE) is a selection bias resulting from the interaction between the selected dates and birthdates. Nevertheless, the impact of birthdate on the junior-to-senior transition in international track and field is unclear. This study aimed to quantify the RAE's magnitude and test if birthdate affects the junior-to-senior transition rate. The birthdate and performances of 5,766 sprinters (female: 51.0%) and 5,863 jumpers (female: 45.9%) were collected. Elite athletes (operationally defined as the World's all-time Top 200, 100 and 50 athletes) were identified according to Under 18 and Senior categories. Skewed quartile distributions were observed in the Under 18 (effect size ranged = 0.15–0.10) but not in the Senior category. RAE magnitude increased according to performance level (i.e., from Top 200 to Top 50) and was higher in males than females. Relatively younger athletes showed significantly higher transition rates with a higher chance of maintaining top level in the senior category (odds ratio (OR) ~ 1.64). The probability of maintaining success was lower for sprinters than jumpers (OR ~ 0.70), influenced by decade of birth and continental place but similar for male and female athletes. Data corroborate that relatively younger athletes are disadvantaged in the junior category but advantaged when transitioning to the senior category. [ABSTRACT FROM AUTHOR]

This retrospective study investigated whether corrective adjustment procedures can remove the relative age effect (RAE) from world-class junior sprinters at the beginning of their career. A total of 2,918 male and 3,029 female athletes competing in sprint races (100 m, 200 m, and 400 m) of the World Athletics lists between 2000 and 2018 were considered. Longitudinal quadratic trendline equations across ages 16–25 yrs were calculated considering athletes' exact age and respective performance. Corrective adjustment calculations from the estimated longitudinal quadratic equations were applied at 16 yrs and 17 yrs. RAE was investigated for the whole sample and top-level athletes (i.e., first Top50 and Top100) considering the uncorrected and corrected performance. Moderate to large RAE was observed in Top50 and Top100 at 16 yrs. Differently, a lower RAE was observed at 17 yrs. When re-examining the data using the corrective adjustment calculations, the RAE disappeared in all sprint events and both genders at 16 yrs, while a more equal distribution was observed at 17 yrs. Corrective adjustment procedures can remove or at least reduce the RAE in world-class sprinters. Applying simple equations based on exact age might improve the accuracy of performance evaluation and talent identification in international track and field sprint competitions. [ABSTRACT FROM AUTHOR]