Maturity-Related Variation in Moderate-to-Vigorous Physical Activity Among 9-14 Year Olds

Abstract

Maturation status can vary considerably among youth of similar chronological age. To date, little is known about the relationship between maturation status and level of physical activity among boys and girls. PURPOSE: The purpose of this study was to compare levels of objectively measured physical activity between early, average, and late maturing boys and girls. Additionally, age- and gender-related differences in physical activity were examined according to chronological and biological age. METHODS: Moderate-to-vigorous physical activity (MVPA) was assessed with an Actigraph accelerometer in 161 (76 boys, 85 girls) 9-14 year olds over 7 consecutive days. Anthropometric variables (age, height, sitting height, body mass, and leg length) were measured while the body mass index (BMI) and maturity offset (i.e., years from peak height velocity) were derived. Biological maturity groups (early, average, and late) were created based on the mean estimated age at peak height velocity for boys and girls separately. Differences among maturity groups were examined using analysis of covariance, controlling for chronological age, body mass, and/or BMI. Analysis of variance was used to examine differences in MVPA among chronological age groups, while differences in MVPA among biological age groups were examined with analysis of covariance, controlling for chronological age. Gender comparisons among age groups were examined with dependent t-tests. RESULTS: Levels of MVPA were similar between early, average, and late maturing boys and girls after adjusting for differences in chronological age. The level of MVPA was higher among chronologically younger, compared to older, participants (p < 0.05) and gender differences in MVPA were found at 10-, 12-, and 13-years (boys > girls) (p< 0.05). Age- and gender-related differences disappeared when boys and girls were aligned according to biological age that accounted for chronological age. CONCLUSIONS: The results of this study suggest that the differences in MVPA between early, average, and late maturing boys and girls were largely explained by differences in chronological age, rather than differences in body size. The results also suggest that biological age may be important to consider when activity levels are compared among boys and girls of varying chronological age.