Relative age effect on muscle power in Brazilian youth: a population study

Resumen

This study aimed to examine the relative age effect on muscle power in a large sample of Brazilian children and adolescents. The sample consisted of 87,766 girls and boys aged 7-16 years, data collected in repeated cross-sectional surveillance carried out since 1999. The participants were grouped into four age subgroups within each chronological age based on birthdates. Upper and lower limbs muscle power were assessed using the 2-Kg medicine ball throw and horizontal jump tests, respectively. The normative distribution of physical fitness components was used for classification. The results showed a significant association between relative age and normative classification of muscle power. Among boys, there was a sequential increase in the frequency of individuals classified as "very good/excellent" as the relative age increased. A similar trend was observed among girls. The findings provided evidence of a relative age effect on muscle power in Brazilian children and adolescents. These findings have implications for the organization of structured physical activities and sports, as early-born individuals may have an advantage in performance. Further research is needed to explore the underlying mechanisms and potential interventions to mitigate the relative age effect and promote equal opportunities for all youth in physical activities and sports.