This study was aimed at analyzing physical fitness in 9–11-year-old children and verifying whether it is affected by body mass index (BMI), peak height velocity (PHV), quartile distribution (QD), and sport practice (SP), also considering any potential effects of sex. One thousand one hundred forty-three Italian primary school children (50.7% males) underwent anthropometric measurements (body mass, height, and BMI) and physical tests for measuring coordination (Plate Tapping, PT), handgrip strength (HandGrip, HG), lower-limb power (standing long jump, SLJ), low-back flexibility (sit-and-reach, SR), and sprint (20 m sprint, 20 m) skills. A series of analyses of covariance (ANCOVAs) were conducted using age as a covariate to examine differences among subgroups for BMI, PHV, QD, and SP in relation to the different physical tests (i.e., PT, HG, SLJ, SL, 20 m). Sex was included in each model as fixed independent variable. Principally, participants with higher SP and BMI reported higher and lower performance (p < 0.001) in SLJ, SR, and 20 m tests, respectively. Differently, for higher BMI levels, higher HG performance was reported (p < 0.001). PHV and QD had isolated effects, whereas no effect emerged for PT. Sex interactions were found only for SP subcategories in SR (p ≤ 0.001, ES range = 0.74–1.30). Although physical performance in 9–11-year-old (non-competitive, pre-puberty) Italian students does not seem to be characterized by involuntary factors (such as PHV and QD), substantial opposite trends seem to exist for voluntary factors (such as BMI and SP), thus suggesting how an adequate lifestyle and physical activity could crucially lead to valuable fitness benefits.

The relative age effect and transition rates across a national soccer program in male and female youth to senior players. A longitudinal analysis

This study investigated the relative age effect (RAE) and its impact on performance in male basketball players participating in Turkish youth championships across U14, U16, and U18 age categories between 2017 and 2023 except 2020-2021 because of COVID-19 pandemics. An archival data model was employed, analysing data from 3113 players between 2017 and 2023. The months of birth were divided into four three-month periods and called Q1 to Q4. Statistical analyses included Chi-square tests with odds ratios, Welch ANOVA, and principal component analysis (PCA) used to visualize performance variable structures. Results indicated a significant RAE across all age groups, with Q1-born players consistently overrepresented and demonstrating superior performance in key metrics such as playing time, points, field goals, and efficiency score. The RAE was most pronounced in the U14 category, peaked at U16, and, while still present, was less prominent in U18, suggesting a convergence of biological maturity and the increasing influence of technical-tactical skills at older ages. PCA further revealed that early-born players were more likely to occupy central and productive roles on the court. These findings emphasize that coaches and policy-makers should consider RAE in their selection processes to ensure that long-term potential is not overlooked due to initial age-related disparities.

Abstract This study estimates the impact of relative age (i.e., the difference in classmates’ ages) on both the speed and quality of individuals’ transition from education to the labour market, and investigates whether and how this impact passes through characteristics of students’ educational careers—topics that have been largely overlooked in prior work. We use rich data pertaining to schooling and to labour market outcomes one year after graduation to conduct instrumental variables analyses. We find that a one-year increase in relative age increases the likelihood of (i) being employed then by 3.5 percentage points (baseline 91.2%), (ii) having a permanent contract by 5.1 percentage points (baseline 42.6%), and (iii) having full-time employment by 6.5 percentage points (baseline 79.5%). These relative age effects are partly mediated by intermediate outcomes such as having had a schooling delay at the age of sixteen or taking on student jobs. The final mediator is particularly notable as no earlier studies examined relative age effects on student employment.

This study examines the main forms of discrimination, including gender inequality, racial bias, economic barriers, challenges faced by athletes with disabilities, the impact of the industrialisation of sport, and the influence of the Relative Age Effect (RAE). The method used is a literature study covering academic research, international agency reports, policy documents, and case studies. The results of the study show that gender inequality is still evident in the distribution of resources, competition opportunities, leadership positions, and media coverage. Racial bias arises through stereotypes, subjective coaching assessments, and economic inequality. Athletes from low-income families face limitations in accessing quality coaching, facilities, and competitions, while athletes with disabilities often face barriers in accessing adequate facilities and support. RAE also contributes to creating indirect but persistent inequalities in athlete development. These various forms of discrimination have an impact on athletes' psychological well-being, career opportunities, and the effectiveness of sports organisation management. The research findings emphasise the need for inclusive policies, anti-discrimination training, equal access to facilities, transparent selection processes, and more balanced media coverage

Background: The Relative Age Effect (RAE) refers to the advantage conferred to athletes born earlier within a selection year. In karate, particularly at the highest level, evidence is lacking. This study aimed to examine the presence of RAE among male and female karate athletes competing at the Tokyo 2020 Olympic Games, in two competitive disciplines: kata and kumite. Methods: Data from 81 athletes (42 males, 39 females) were retrieved from open-access databases. Birthdates were grouped into quartiles (Q1–Q4) and semesters (S1–S2). Chi-squared tests and odds ratios (ORs) were used to assess deviations from a uniform distribution, while binary logistic regression examined the association between semester of birth and medal attainment. Results: The overall distribution of birth quartiles significantly deviated from a uniform distribution (χ2(3) = 9.81, p = 0.020), indicating a higher proportion of athletes born in Q1 (38%) compared with Q4 (19%; OR = 2.07). RAE was particularly evident in kumite (χ2(3) = 17.87, p < 0.001; OR = 3.50 for Q1 vs. Q4) and among female athletes (χ2(3) = 9.92, p = 0.019), whereas no significant effect was found in kata or among males. Logistic regression revealed no significant association between semester of birth and medal success (OR = 0.49, 95% CI [0.20–1.21], p = 0.125). Conclusions: This study provides the first evidence of RAE in Olympic karate, especially among females and in kumite. However, relative age did not predict performance outcomes, suggesting that once athletes reach the Olympic level, technical and tactical factors outweigh birthdate advantages.

ABSTRACT The aim of this study was to evaluate the influence of age category (AC) and relative age effects (RAEs) on the running performance of youth soccer players. We analysed matches from the men’s U17 (n = 47) and U20 (n = 50) World Cups. A total of 452 (U17 = 218; U20 = 234) soccer players who played 90 minutes in matches during each tournament were evaluated in order to analyse the impact of AC and RAEs on running performances obtained by multiple camera computerised optical tracking system (OTS) (TRACAB). Running performance included: total distance covered (m), distance in the speed categories of Zone1,2,3,4,5 (m), attempted high-speed runs (count), attempted sprint (count), and top speed (km·h−1). Results showed a significant chronological age effect on total distance, Zones 2,3,4,5, attempted high-speed runs and sprints, and top speed for U20 compared to U17 (p < 0.001). Zone 1 was significantly lower in U20 compared with U17 (p < 0.001). There were no significant RAEs within both categories based on running performance (p > 0.05). In conclusion, match running performance increases with age from the U17 to the U20 categories, whereas differences between birth quartiles are negligible. At these ages, the effects of RAE on performance appear to be eliminated, although its influence on selection and participation still remains. Therefore, coaches and practitioners should be aware of this distinction when making decisions related to talent identification and development.

BackgroundThe relative age effects (RAE) have been a hot topic in the field of sport research, and although the phenomenon has been found in most sports in China, there is currently no literature on the RAE phenomenon in Chinese basketball, which has implications for explaining some of the phenomena in that sport. A large body of research suggests that RAE contributes significantly to the phenomena of brain drain and inequality in sport participation. The purpose of this study was to analyze whether RAE exists in Chinese youth men’s basketball and whether RAE has an impact on the performance of athletes and teams, thus supporting the subsequent proposal of measures to balance the age effect.MethodsThis study analyzed the date of birth and performance rankings of all male athletes (n = 3926) who participated in the Chinese Youth Basketball Championships (U14, U15, and U17) from 2021 to 2023. The study divided the month of birth into quarters and semesters. Differences between actual observed and theoretical birth date distributions were statistically analyzed using the chi-square test, and subsequent calculations were made using the dominance ratio test.ResultsIt was found that RAE was present in all three groups of Chinese youth male basketball players (p < 001). The percentages of athletes born in the first half of the year were 61.2% (U14), 59.9% (U15), and 59.0% (U17), and the percentages of athletes born in the first quarter were 38.6% (U14), 35.8% (U15), and 34.8% (U17).ConclusionsAs a result of RAE, U15 athletes born closer to the beginning of the year are likely to achieve better results, whereas athletes born closer to the end of the year are less likely to achieve athletic excellence.

Youth motor performance changes are not strictly linear during their sports career, and within-year birth timing may introduce relative age differences, known as the relative-age effect. In a cross-sectional study of 170 male young soccer players (8–12 years old), field tests were compared between adjacent age groups and within each of them: countermovement jump (with and without arm swing); 15 m linear sprint and agility test with and without the ball. Non-parametric tests with post hoc comparisons revealed significant differences between consecutive birth years in physical skills, particularly between the youngest and oldest groups. Specifically, differences were noted in the jumping test between U12 and U11, and between U10 and U9. Additionally, linear sprint and agility tests showed significance in U13 versus U12 and U10 versus U9. Finally, dribbling skills mature later (in both tests, U13 v U12, U12 v U11; with the ball, U10 v U9). Differences were found within the groups based on the semester, but not the trimester of birth, confirming a progressive yet non-linear pattern and semester-level within-year differences. These findings suggest the key role of motor skills development trajectories in creating individualized training programs tailored to the needs of individual young soccer players.

This study explores the influence of relative age on the athletic and academic performance of young swimmers, while also considering other contributing factors such as training conditions, anthropometric characteristics, and coaches’ subjective evaluations. A descriptive, explanatory, and prospective design was employed, using quantitative (questionnaires) and observational methods. The sample consisted of 33 national-level swimmers (11 males and 22 females). Variables analyzed included sex, date of birth, training data, academic performance (AP), final sport performance (SP), coaches’ perceptions of daily performance, and anthropometric measurements. Results indicated no direct effect of relative age on the main variables. However, ANCOVA revealed significant differences based on birth quartile (p = .001), month of birth (p = .001), training frequency (p = .003), and body weight when mediated by sport category. Additionally, significant associations were found between relative age and sport performance when BMI was included as a covariate (p = .036), along with year and month of birth (p = .038; p = .027). Coaches’ perceptions of performance were also significantly related to competitive category (p = .033). It is concluded that while relative age may influence athletic performance, its effect appears to be mediated by contextual and individual factors related to the athlete’s preparation and environment.

This study explores the influence of relative age on the athletic and academic performance of young swimmers, while also considering other contributing factors such as training conditions, anthropometric characteristics, and coaches' subjective evaluations. A descriptive, explanatory, and prospective design was employed, using quantitative (questionnaires) and observational methods. The sample consisted of 33 national-level swimmers (11 males and 22 females). Variables analyzed included sex, date of birth, training data, academic performance (AP), final sport performance (SP), coaches' perceptions of daily performance, and anthropometric measurements. Results indicated no direct effect of relative age on the main variables. However, ANCOVA revealed significant differences based on birth quartile (p = .001), month of birth (p = .001), training frequency (p = .003), and body weight when mediated by sport category. Additionally, significant associations were found between relative age and sport performance when BMI was included as a covariate (p = .036), along with year and month of birth (p = .038; p = .027). Coaches' perceptions of performance were also significantly related to competitive category (p = .033). It is concluded that while relative age may influence athletic performance, its effect appears to be mediated by contextual and individual factors related to the athlete's preparation and environment.

BackgroundThe Relative Age Effect (RAE) refers to the advantage in physical and psychological development that children born earlier in the year often experience, which can influence their participation in sports.AimAnalyze the influence of RAE on motor competence (MC) in school-aged children, focusing on differences across birth quartiles and types of sports participation.MethodsA cross-sectional study was conducted with 1,031 children aged 12.02 ± 2.95 years, stratified by birth quartile (Q1–Q4) and sports participation. MC was assessed using the Motor Competence Assessment (MCA) test battery. Statistical analyses included one-way ANOVA and a three-way MANCOVA.ResultsParticipants born in Q1 exhibited significantly higher MC scores compared to those born in Q3 and Q4, particularly in the Manipulative domain (p < 0.05, η2 = 0.01). Sports participation had the strongest effect (p < 0.01, η2 = 0.10), with participants in team sports demonstrating higher MC across all domains. Boys outperformed girls in Manipulative skills (p < 0.01, η2 = 0.12). Furthermore, the interaction between birth quartile, sports participation, and sex was also significant (p = 0.02, η2 = 0.01), indicating that the influence of RAE on MC depends on additional contextual factors.ConclusionsWhile RAE had a statistically significant but small effect on MC, sports participation, particularly team sports, and sex may play more dominant roles. These findings underscore the importance of promoting equitable access to organized physical activity while considering the nuanced and context-dependent nature of the RAE.

Talent identification in youth sports is a multifactorial process, with athletic profiling and the Relative Age Effect (RAE) playing critical roles. However, few studies have investigated their combined influence on long-term success in youth basketball. This study explores how athletic profiles and RAE influence future success in young male basketball players. A total of 131 players (age: 14.5 ± 0.7 years; height: 180.6 ± 9.7 cm) were assessed on speed, agility, vertical jump, and endurance. RAE was evaluated via birth quarter distribution. A principal component analysis followed by hierarchical clustering revealed four distinct performance profiles: Hybrid (n = 45), Elevated (n = 34), Resilient (n = 35), and Explosive (n = 19). These clusters were cross-referenced with players’ future levels of competition: Amateur (n = 105), Developmental (n = 19), and Elite (n = 9). Both athletic profiles and RAE showed statistically noteworthy associations with future achievement (p < 0.10). Notably, players in the Resilient cluster—characterized by lower physical test scores and later birthdates—were more likely to reach the Elite level. These findings highlight the importance of accounting for individual developmental trajectories and relative age in talent identification. They support a more holistic, long-term approach to player evaluation, challenging the assumption that early physical superiority reliably predicts future elite status.

Background/Objectives: The integration of strength training in grassroots youth soccer remains limited, often due to persistent myths regarding its safety and utility. This study evaluated the effectiveness of a tailored, playful strength training program in young players and analyzed the influence of the Relative Age Effect (RAE) on physical development and training response. Methods: A 14-week quasi-experimental pretest-posttest design was conducted with 27 federated male soccer players aged 9-10 years (experimental: n = 15; control: n = 12). The intervention consisted of twice-weekly, game-based strength training sessions integrated into the regular team routine. Outcomes included validated anthropometric (BMI) and functional (handgrip strength, standing long jump, Illinois agility test) indicators. RAE was analyzed according to birth quartile. Non-parametric statistical analyses and effect size (r) calculations were used. Results: The experimental group achieved significantly greater pre-post gains in handgrip strength than controls (right and left). Agility and standing long jump improved within the experimental group, but between-group differences were not significant. BMI decreased within the experimental group, yet the net between-group difference in BMI change was not significant in the context of a higher baseline BMI (p = 0.047). Although the Relative Age Effect (RAE) influenced baseline BMI, no moderating effect was detected on performance variables or training-induced changes in this sample. Conclusions: In U10 soccer players, a playful, context-integrated strength program produced superior gains in handgrip strength compared with usual practice. Improvements in agility and standing long jump were observed within the intervention group, but did not exceed those of the controls. BMI changes were not different between the groups and must be interpreted with caution, given baseline imbalances. In this sample, RAE did not moderate training response.

ObjectivesThis study aimed to investigate the relationship between the relative age effect (RAE) and success in ice hockey during adolescence and adulthood in male Swedish players, as well as potential interactions between relative age (RA) and biological maturation.MethodsAnthropometric data were collected from high schools with a certified ice hockey programme over 20 years. Birth dates were extracted from public databases to calculate numerical relative age (n = 2211 players). Biological maturity timing was defined as the z-score of the percentage of adult height (z%AH) reached at term 1 (~ 16 years of age). Retrospective longitudinal data on selection to junior national teams (U16, U18, U20) and the National Hockey League (NHL) were retrieved from open databases. Junior and adult success probabilities were modelled using generalised logistic modelling (GLM). Spearman correlation analysis was used to assess the correlation between the anthropometric data, relative age, and biological maturation. In addition, the predictor z%AH was added to the GLMs to characterise interactions.ResultsIndividuals with a higher relative age were overrepresented in Swedish ice hockey programmes. Players born between January and March (Q1) were about twice as likely to reach the U16 national team as players born between October and December (Q4). Consequently, in a GLM, relative age was identified as a significant predictor of junior success. The addition of z%AH improved model fit for U16 selection, and an interaction between z%AH and RA was observed (p < 0.05). In contrast, relative age was not a significant predictor of reaching the NHL (p = 0.21). There was no interaction between the RA and z%AH (p = 0.44) for adult success. When cross-tabulated, the players most likely to reach both the NHL and the U16 national team were either born early and matured late or born late and matured early.ConclusionEarly-born and early-maturing players in certified Swedish high school programmes are more likely to be selected for the U16 national team. In terms of adult success, RA had no significant effect on the likelihood of playing in the NHL. However, in a combined model, regardless of relative age, players with late biological maturity timing were more likely to reach the NHL.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40798-025-00902-0.

BackgroundA previous study confirmed the existence of the relative age effect (RAE) in the top ten leagues of the Union of European Football Associations (UEFA) during the 2016–2017 season, reporting that the effect was particularly pronounced among defenders and midfielders. The present study investigates whether this effect persists. Specifically, it aims to examine the RAE among professional male footballers in UEFA’s top ten leagues during the 2023–2024 season, and to explore how the effect varies by playing position and league.MethodsThe study analysed the birthdates and playing positions of 5,238 professional footballers. Birthdates were categorised into four quartiles: Q1 (January 1 to March 31), Q2 (April 1 to June 30), Q3 (July 1 to September 30), and Q4 (October 1 to December 31), and were examined in detail by league and position.ResultsPlayers born in Q1 (30.3%) were overrepresented compared to those born in Q4 (20.5%) (χ² = 132.470, p < .05). This difference was statistically significant in most leagues, particularly in Serie A (χ² = 33.535, V = 0.14), Ligue 1 (χ² = 23.741, V = 0.11), LaLiga (χ² = 22.491, V = 0.12), and Bundesliga (χ² = 21.681, V = 0.12), but not in Premier League (χ² = 1.665, p = .645). In terms of playing position, the RAE was present across all groups (p < .05), with the most pronounced effect observed among goalkeepers (χ² = 40.006, V = 0.15). Positional RAE patterns varied across leagues: significant differences were found for goalkeepers in Serie A, Süper Lig, and LaLiga; for defenders in LaLiga and Jupiler Pro League; for midfielders in Serie A, Ligue 1, Süper Lig, and Eredivisie; and for forwards in Ligue 1, Bundesliga, and Scottish Premiership (p < .05).ConclusionThe findings indicate that the RAE persists in professional football within UEFA’s top leagues. The effect is evident across all playing positions and varies by league context.

Introduction: The relative age effect (RAE) refers to performance advantages for individuals born early in a selection period compared to later-born peers, potentially biasing early talent identification in youth sports. This study extends prior research on the Z Strategy for detecting sports talents in Chilean schoolchildren. Objective: To analyze the relative age effect in detecting potential sports talents among Chilean 8th-grade students using the 2013 Physical Education SIMCE database and Z Strategy results. Methodology: A retrospective cross-sectional study was conducted with a representative sample of approximately 12,000 8th-grade students (ages 13-16, 50% female) assessed in 2013. Anthropometric and physical fitness data were collected via standardized tests. The Z Strategy identified talents as students with values ≥2 standard deviations above the mean in at least one variable, standardized by age and sex. Birthdates were categorized into quartiles (Q1-Q4), and distributions were compared using chi-square tests. Results: 1,242 students (13%) were identified as potential talents. Males showed significant RAE with 36% born in Q1 versus 15% in Q4 (p&lt;0.001), while females had uniform distribution (~25% per quartile). Overall, 61% of talents were born in the first half of the year compared to 38% in the second half. Discussion: Findings align with international literature indicating widespread RAE in youth sports, particularly stronger in males due to maturation differences, as reported in studies on soccer and athletics. The absence in females matches reports of weaker RAE in female contexts. Conclusions: RAE significantly biases talent detection in Chilean male students, necessitating adjustments for equitable identification.

Relative Age Effect in Swimming: Insights from a National Talent Program

IntroductionUnderstanding the motor competence development of young children requires both cross-sectional and longitudinal analyses. This is crucial for identifying relative age effects and tracking individual developmental trajectories. However, there are limited data in Southeast Asia, particularly in Singapore.MethodsThis study monitored the development of motor competence of 75 children in Singapore, aged 3–4.5 years, over an 18-month period. Four data points were conducted using the Movement Assessment for Children, 2nd Edition (MABC-2) at six-month intervals. Data were analyzed using repeated measures multivariate analysis of variance (MANOVA), two-way analysis of variance (ANOVA), and post-hoc multiple comparisons.ResultsCross-sectional analysis revealed a positive age effect across all eight motor tasks, with older children demonstrating higher fine and gross motor competence. Longitudinal analysis showed significant improvement in seven out of eight motor tasks over the 18-month period, except for the task of jumping on mats.ConclusionThe most pronounced age effect was observed between children aged 3.5 and 4.0 years, suggesting a potential period of accelerated motor development within this age range. The significant improvements in motor competence observed over the 18-month period underscore the critical nature of early childhood for motor skill acquisition. Additionally, the study highlights the importance of frequent monitoring (e.g., every 6 months) to identify children with motor delays and facilitate timely interventions.

Past research shows that relative age effects (RAEs) are highly prevalent in ice hockey. Early-born players benefit from more exposure, especially in the early stages of development, and are frequently considered "more talented." Although RAEs are apparent in these early stages, little is known about how it affects pathways leading to the highest levels of competition. This study aims to look more closely at the associations between RAEs and players' career trajectories in 4 hockey nations: Canada, Finland, Czechia, and Slovakia. Specifically, it aims to: (1) evaluate the prevalence of RAEs in each country, (2) identify players' career pathways and examine the impact of RAEs on the players, and (3) compare these effects for each nation. Data were drawn from 4,306 players (100% males born between 1992 and 2002), who were invited to national development and selection camps between 2009 and 2019. Trajectory clusters were estimated from the players' participation in 8 career milestones, from U17 to representation of their country at the Olympic Games. Group comparisons were conducted based on birth quartiles and hockey nations. The results confirmed the presence of RAEs in the four hockey nations. Consistent with past research, early-born players are overrepresented in the early career stage, whereas late-born players begin to emerge during transition to junior level (U20). Some nation-specific differences were observed. This provides further support for the stakeholders of ice hockey association looking to enhance their national team selection processes and discover structuring pathways that offer development opportunities for all groups of players.