The effectiveness of school-based physical activity interventions for adolescent girls: a systematic review and meta-analysis

Physical activity (PA) decreases during the transition from childhood to adolescence, with larger declines observed in girls. School-based interventions are considered the most promising approach for increasing adolescents' PA levels although, it is unclear which types of school-based interventions have the greatest impact. The objective of this systematic review is to assess the impact and design of school-based PA interventions targeting adolescent girls. A systematic search was conducted using four electronic databases (PubMed, Web of Science, SPORTDiscus and PsychInfo). This systematic review was registered with PROSPERO (Registration number: CRD42016037428) and PRISMA guidelines (2009) were followed throughout. Twenty studies were identified as meeting the inclusion criteria and were included in a narrative synthesis. Seventeen studies were eligible for inclusion in a meta-analysis. There was a significant small positive treatment effect for school-based PA interventions for adolescent girls (k = 17, g = 0.37, p < 0.05). After an outlier was removed (residual z = 7.61) the average treatment effect was significantly reduced, indicating a very small positive effect (k = 16, g = 0.07, p = 0.05). Subgroup analysis revealed very small significant effects for multi-component interventions (k = 7, g = 0.09, p < 0.05), interventions underpinned by theory (k = 12, g = 0.07, p < 0.05), and studies with a higher risk of bias (k = 13, g = 0.09, p < 0.05). Intervention effects were very small which indicates that changing PA behaviors in adolescent girls through school-based interventions is challenging. Multi-component interventions and interventions underpinned by theory may be the most effective approaches to positively change adolescent girls' PA.