Abstract
BACKGROUND: Although physical activity is beneficial for breast cancer survivors, the majority do not meet public health physical activity recommendations. The purpose of this study was to test a social cognitive theory model of physical activity behavior in a sample of long-term breast cancer survivors using both self-report and objective measures of physical activity. METHODS: Participants (N = 1527) completed measures of physical activity, self-efficacy, goals, outcome expectations, fatigue, and social support at baseline and 6-month follow-up. A subsample (n = 370) was randomly selected to wear an accelerometer. It was hypothesized that self-efficacy directly and indirectly influences physical activity through goals, social support, fatigue, and outcome expectations. Relationships were examined using panel analysis within a covariance modeling framework. RESULTS: The hypothesized model provided a good model-data fit (χ(2) = 1168.73, df = 271, p = <0.001, CFI = 0.96, SRMR = 0.04) in the full sample when controlling for covariates. At baseline, self-efficacy directly and indirectly, via goals, outcome expectations, and social support, influenced physical activity. These relationships were also supported across time. Additionally, the hypothesized model was supported in the subsample with accelerometer data (χ2 = 656.88, df = 330, p < 0.001, CFI = 0.95, SRMR = 0.05). CONCLUSIONS: This study validates a social cognitive model for understanding physical activity behavior in long-term breast cancer survivors. Future studies should be designed to replicate this model in other breast cancer survivor populations, and the findings should be applied to the development of future physical activity programs and studies for this population.