Associations Between Relative Age, Siblings, and Motor Competence in Children and Adolescents.

Background: Motor competence is a key determinant of children's physical, cognitive, and social development, and it is influenced by various biological and environmental factors. Among these, relative age and the presence of siblings have been proposed as potential contributors, yet their impact remains underexplored, especially in school-aged populations.

Objective: This study investigates the influence of relative age and the effects of the presence of siblings on the motor competence of children and adolescents.

Methods: The motor competence level of 747 students, 381 from primary school (mean age = 8.81 ± 1.8 years) and 366 from secondary school (mean age = 13.52 ± 1.22 years), was measured by the means of the Canadian Agility and Movement Skill Assessment. Participants were queried about their birth date and whether they had any older siblings.

Results: Overall, motor competence exhibited an upward trend with chronological age, reaching its peak among children aged 14 years old. Analysis revealed a significant impact of relative age effects on motor competence among primary children, with considerably higher scores in the first semester (p = 0.017). Conversely, no clear trend was observed for secondary children. Having siblings did not significantly affect motor competence proficiency. Multiple regression analysis further confirmed that relative age did not contribute to this lack of association (quarter of birth: p = 0.003; β = -0.144; siblings: p = 0.697; β = -0.019).

Conclusions: These findings suggest that physical education teachers should be aware of the influence of relative age not only when assessing motor competence but also when designing and implementing their teaching practice in primary school settings. In contrast, the effect of relative age appears to be less significant in secondary education, where it may be less relevant for both evaluation and teaching practice. Further research should explore longitudinal designs and consider additional psychosocial and environmental variables to better understand how these factors influence motor competence development over time.