Abstract
BACKGROUND: Previous research has shown that social contextual factors are important in understanding physical activity (PA) behavior, although little is known about how these factors may relate to PA, especially in underserved adolescents (low income, minorities). This study examined how motivation may differentially mediate the relationship of two social contextual variables (i.e., peer and parent social support) and moderate-to-vigorous PA (MVPA). METHODS: Baseline data (n = 1421 sixth graders, 54% female, 72% African American) from the Active by Choice Today (ACT) trial in underserved adolescents were analyzed. Motivation was examined as a mediator of the relationships between peer social support, parent social support, and MVPA (measured by 7-day accelerometer estimates). RESULTS: Motivation and peer but not parent support were significantly related to MVPA overall. Significant mediation effects were found indicating motivation partially mediated the relation between peer social support and MVPA and to a lesser degree parent support and MVPA. CONCLUSIONS: These findings provide support for the importance of social contextual influences, especially peer social support, on underserved adolescents' PA and motivation for PA.