Mediators of physical activity outcomes in a peer-led intervention for breast cancer survivors

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OBJECTIVES: Physical activity (PA) adoption can reduce treatment-related sequelae of breast cancer. Peer-led PA interventions are a promising and relatively inexpensive approach to scaling up interventions. The current study seeks to identify mediators of PA change amongst cancer survivors enrolled in a peer-led behavior change intervention. The study team partnered with the American Cancer Society's Reach to Recovery program (RTR) whose volunteers' provided information and support to breast cancer survivors. METHODS: Participants were 76 survivors (mean age 55.6 years, 1.1 years since diagnosis) who were randomized to PA Plus RTR (12-week PA telephone counseling delivered by RTR volunteers) or contact control. Data was collected on PA (self-reported and objectively measured) and potential mediators (self-efficacy, exercise decisional balance [ratio of the pros/advantages to the cons/disadvantages] and social support) at baseline and 12 weeks. Using a multiple mediation approach with bootstrapped standard errors, we examined mediators of the intervention effect on PA outcomes. RESULTS: Compared to control, PA Plus RTR participants had higher mean self-efficacy, lower decisional balance cons and social support at 12 weeks controlling for baseline. Higher mean self-efficacy was associated with greater minutes of self-reported PA, whereas higher decisional balance pros was associated with higher objectively measured PA at 12 weeks. There were significant indirect effects of self-efficacy on self-reported PA and decisional balance on objectively measured PA. CONCLUSIONS: PA Plus RTR increased self-reported and objectively measured PA by changing theoretical constructs hypothesized to be associated with behavior change. Peers delivering a PA intervention should focus on increasing survivors' self-efficacy for exercise especially in challenging circumstances such as being on vacation, and also help to overcome disadvantages of exercise such as taking time away from family.