A social ecological assessment of physical activity among urban adolescents.

Objectives: To examine the physical, social and temporal contexts of physical activity, as well as sex variations of the associations among 314 urban adolescents.

Methods: Three-day physical activity recall measured contextual information of physical activities. Logistic regressions and generalized estimating equation models examined associations among physical activity types and contexts, and sex differences.

Results: Active transportation was the most common physical activity. Home/neighborhood and school were the most common physical activity locations. School was the main location for organized physical activity. Boys spent more time on recreational physical activity, regardless of the social context, compared to girls. The average physical activity level was significantly lower for girls than for boys after school.

Conclusions: Physical activity promotion interventions need to target physical activity environments and social contexts in a sex-specific manner.