Background: Some researchers have questioned if activity programs would be more effective if based outside school (eg, community leagues) rather than within schools. This study compared participation in activity programs based within and outside of school, and estimated the associations between participation and moderate-vigorous physical activity (MVPA) among adolescent girls.
Methods: Within the Trial of Activity for Adolescent Girls, independent samples of 1559 6th-grade girls (age 11 to 12) and 3282 8th-grade girls (age 13 to 14) reported program participation using questionnaires. MVPA was measured using accelerometers. Linear mixed models accounted for school and site clustering.
Results: Sixth-grade girls reported 5 times as many programs outside school as within school (4.1 vs. 0.8); daily MVPA was 0.29 minutes higher (1.2% of the mean) for each additional program outside school. Compared with 6th-grade girls, 8th-grade girls participated in 1.3 fewer programs outside school, while programs' association with MVPA was unchanged. Conversely, school programs' association with MVPA was greater in 8th grade. Daily MVPA was 1.33 minutes higher per school program, and participation declined 0.13.
Conclusion: Programs within and outside schools can both increase activity among adolescent girls. Intervention research should focus on increasing participation in school programs, and increasing movement during programs outside school.