Childhood obesity prevalence has increased dramati- cally over the past 30 years in the United States. The percentage of overweight 6 to 19 years old children and adolescents has tripled since 1980 [1]. Children who par-ticipate in regular physical activity (PA) are less likely to be obese and may be more likely to be physically active as adults [2]. Recent recommendations suggest that youth should accumulate 60 minutes or more of moder- ate-to-vigorous PA per day [3]. Evidence indicates that only 42% of 6 to 12 year olds, and 8% of 12 to 19 year olds, meet recommendations [4]. Thus, a need exists to identify evidence-based strategies that increase children’s PA.
Group PA settings, such as physical education, recess, and out-of-school programs and clubs provide PA op- portunities [5]. These settings, according to Social Cog- nitive Theory [6], are physical and social environments that reciprocally interact with personal factors to deter- mine PA. Several studies have examined the social and physical environment influences on habitual child PA [7,8], and how to increase PA by making changes in the physical environment [9-12]. However, few studies have examined social environmental influences during group PA settings [13].