School-based physical activity interventions for children and youth:Keys for success

Given the rising trend in obesity in children and youth and age-related decline in moderate-to-vigorous-intensity physical activity（MVPA）in several Western,African,and Asian-Pacific countries;and strong evidence that past physical activity（PA）interventions have had only a small effect on children’s and youth’s overall activity levels,;it is important to clarify whether school-based PA interventions warrant resource allocation.Schools represent an accessible and cost-effective setting