The influence of relative age effects on the cardiorespiratory fitness levels of children age 9 to 10 and 11 to 12 years of age.

The aims of this study were firstly to examine whether there was an observed relative age effect in the cardiorespiratory fitness scores of 9-10 and 11-12 year old children, and secondly whether any observed effect was maintained after controlling for somatic maturity. Cardiorespiratory fitness data from 11,404 children aged 9-10 years and 3,911 children aged 11-12 years were obtained from a large cross-sectional field-based fitness testing program. A one-way ANOVA revealed a statistically significant relative age effect (p < .01) existed in the 20mSRT scores across all the age groups. Furthermore, ANCOVA analyses identified a statistically significant relative age effect was maintained after controlling for somatic maturation (p < .05). From a public health perspective these results confirm the existence of relative age effects for the first time and consequently may hold implications for relatively younger children in the accurate assessment of their cardiorespiratory fitness scores.