Early determinants of physical activity in adolescence

Objective: To examine the effects of early social, anthropometric, and behavioural variables on physical activity in adolescence.

Setting: Pelotas, southern Brazil. Participants 4453 adolescents aged 10-12 years participating in the Pelotas 1993 birth cohort study (follow-up rate 87.5%).

Conclusions: Physical activity in adolescence does not seem to be programmed by physiological factors in infancy. A positive association between birth order and activity may be due to greater intensity of play in childhood and adolescence. Tracking of physical activity from age 4 to 10-12 years, however, suggests that genetic factors or early habit formation may be important.