Mediators of a physical activity intervention among women with a family history of breast cancer.

The current study examined mediators of an efficacious physical activity intervention. Women with a mean age of 42.6 (range 23-61) years and a family history of breast cancer were randomized to either an Internet-based physical activity intervention (n = 28) or an active control condition (n = 27) for three months. Data were collected between November 2010 and August 2011. Hypothesized mediators were examined using a product of coefficients model with bootstrapped standard errors. Significant mediation was observed for both self-efficacy and behavioral processes. Specifically, the regression coefficients of the indirect effects ("ab path": unstandardized effect of the intervention on physical activity that occurred through the mediator) were ab = 38.58 (95% confidence interval [CI]: 8.66-92.76) for self-efficacy, and ab = 42.02 (95% CI: 6.76-104.84) for behavioral processes. Other factors examined in this study, including cognitive processes, decisional balance, and perceived risk of breast cancer, were not statistically significant mediators. Findings suggest that self-efficacy and behavioral processes may be key constructs to use in targeting future physical activity interventions among women with a family history of breast cancer.