OPENING THE BLACK BOX: HOW DO PEOPLE CHANGE IN PHYSICAL ACTIVITY INTERVENTIONS?

755 As the health benefits of physical activity and the high prevalence of sedentary lifestyles become more thoroughly documented, the need grows for interventions that effectively promote physical activity. Many intervention approaches have demonstrated some effects, but there is a continuing need to improve both interventions and our understanding of how they work. Physical activity interventions are based on a variety of theories of behavior change. These theories lead intervention designers to attempt to change selected psychological, social, and environmental factors that are believed to mediate the behavior change. In addition to evaluating the behavioral outcomes, it is also important to assess whether the intervention is changing the targeted mediators and whether the mediators explain the observed behavior change. These analyses can help refine both interventions and behavior change theories. This symposium features results from four major physical activity interventions for adults that are theoretically based and include measures of hypothesized mediators. Presenters will report the physical activity outcomes, as well as the extent to which mediators are related to physical activity changes. The four studies represent a variety of populations and intervention strategies.