The association between skill-related fitness performance and birth quartiles among children at age 12 years

Background: The birth year is a criterion for grouping competitive categories in various sports. Children born in the early months of the calendar can benefit during their formative process because they have a higher chronological age and are more likely to be in more advanced stages of biological maturation. Objectives: To test the association between skill-related fitness performance and birth quartiles for understanding the relative age effect (RAE) among 12-year-old children in Malaysia.Method: A total of 462 school children (226 boys and 236 girls) with mean age of 12.5 ± 0.5 years were involved in this study. The children underwent four skill-related fitness assessments: 30-metre run, agility t-test, stork balance stand test, and standing broad jump test. Agglomerative hierarchical clustering (AHC) was used to assign participants to the high performance (HPG), moderate performance (MPG), and low-performance (LPG) groups. The groups were split into a contingency table according to four quartiles: Q1 (January to March), Q2 (April to June), Q3 (July to September), and Q4 (October to December). The Chi-square test was used to test the association between performance groups and birth quartile variables.Results: Among the boys, the HPG, MPG, and LPG comprised 105, 81, and 40, children respectively. Among the girls, the HPG, MPG, and LPG comprised 104, 77, and 55 children, respectively. Results of the Chi-square revealed the p-values (0.016) and (0.032) for boys and girls, respectively, were lower than the significance level of alpha = 0.5, demonstrating that the presence of a performance group depends on the variety of birth-month quartiles.Background: The birth year is a criterion for grouping competitive categories in various sports. Children born in the early months of the calendar can benefit during their formative process because they have a higher chronological age and are more likely to be in more advanced stages of biological maturation.Conclusions: The relative age cut-off point has an impact on children's skill-related fitness performance in both boys and girls.