Introduction: Sex differences in the rate of decline in physical activity (PA) are most pronounced during adolescence. However, once boys and girls are aligned on biological age, sex differences in the patterns of PA become attenuated. The aim of this study was to test whether biological maturation can account for sex differences in participation in PA over time from late childhood to early adolescence.
Methods: A prospective cohort of children (N = 2100; 1064 boys) was followed from ages 11 to 14 yr, with repeated assessments of PA and anthropometry. Self-reported participation in organized and free play activities was used to track participation in PA. Biological age was measured using an estimate of years to attainment of peak height velocity. Mixed-effects models were used to test whether controlling for biological age attenuates the effect of chronological age and sex on PA.
Results: As expected, the rate of decline in participation in PA was greater for girls than for boys (B = −1.18, P < 0.01). In multivariable analyses, adjusting for biological age completely attenuated the effect of sex and chronological age for participation in free play activities, but not for participation in organized play. Overall, biological age was a stronger predictor of participation than chronological age.
Conclusions: The effect of biological age on sex by chronological age differences may be specific to certain types of PA participation. Given the importance of maturation to participation in activity, it is suggested that public health strategies target biological not chronological age to prevent declines in PA during adolescence particularly when promoting habitual or lifestyle activity.
1Department of Family Medicine, McMaster University, Hamilton, Ontario, CANADA; 2Centre for Addictions and Mental Health, Toronto, Ontario, CANADA; and 3Community Health Sciences Brock University, St. Catharines, Ontario, CANADA
Address for correspondence: John Cairney, Departments of Family Medicine, Psychiatry and Behavioural Neuroscience, and CanChild Centre for Childhood Disability Research, McMaster University, 175 Longwood Road South, Suite 201a, Hamilton, Ontario L8P 0A1, Canada; E-mail: email@example.com.
Submitted for publication June 2013.
Accepted for publication September 2013.