Abstract / Summary
Theory-based physical activity (PA) interventions improve moderate to vigorous physical activity (MVPA) among breast cancer survivors, yet limited research has examined when psychosocial changes occur during intervention delivery. Understanding temporal changes in theoretical constructs during PA adoption may enhance intervention delivery and outcomes. The purpose of this study is to examine longitudinal changes in self-efficacy, self-regulation and affect (intrapersonal constructs from Social Cognitive Theory) and social support (interpersonal construct) during a 12-week theory-based PA program (webMFT) and their association with participants' active minutes (measured by Fitbit) over 12 weeks and intervention engagement (receipt of 12 weekly peer coaching calls). In a randomized controlled trial with 61 participants, 30 were randomized to receive webMFT (mean age = 58.1 [SD = 8.55], 1.40 years post-diagnosis [SD = 0.5], 80% Stage 0-1 cancer, 80% White) delivered by 10 peer coaches. Only the webMFT participants were assessed; the comparison group (MVPA Tracking) was not included in the analyses. webMFT participants received a Fitbit tracker and weekly PA coaching calls tailored to Fitbit PA data. At baseline, 4, 8 and 12 weeks, they completed questionnaires assessing multidimensional self-efficacy (task, coping, scheduling), self-regulation skills, affective response and social support for PA. Mixed effects regression models examined changes in constructs and their association with Fitbit active minutes/week and intervention engagement. Increases in total self-efficacy, scheduling self-efficacy, positive affect and social support from family and friends were significantly associated with participants' PA over 12 weeks. There were no significant associations between changes in self-regulation skills, task or coping self-efficacy with PA. Improvements in total self-efficacy, scheduling self-efficacy, self-regulation, affective response and family social support were positively associated with intervention engagement. Participants' self-efficacy, specifically, for scheduling PA, positive affect and social support for PA adoption and intervention engagement merit future examination.