Predicting physical activity change in cancer survivors: an application of the Health Action Process Approach.

Purpose Previous research has not examined the utility of the Health Action Process Approach (HAPA) to predict physical activity (PA) change in cancer survivors. The aim of the study was to investigate the efficacy of a HAPA-based model in predicting temporal change in moderate-to-vigorous physical activity (MVPA) in cancer survivors. Methods Participants enrolled in the Wearable Activity Technology and Action Planning (WATAAP) trial completed validated questionnaires (n = 64) to assess HAPA constructs (action and maintenance self-efficacy, outcome expectancies, action planning, risk perceptions, and intention) and wore an ActiGraph to measure PA at baseline, 12 weeks, and 24 weeks later. Data were analyzed using variance-based structural equation modeling with residualized change scores for model variables. Results Consistent with predictions, changes in action self-efficacy (β = 0.490, p < 0.001, ES = 0.258) and risk perceptions (β = 0.312, p = 0.003, ES = 0.099) were statistically significant predictors of intention change over time. Changes in intention (β = 0.217, p = 0.029, ES = 0.040) and action planning (β = 0.234, p = 0.068, ES = 0.068) predicted changes in MVPA. Overall, the model accounted for significant variance in intention (R2 = 0.380) and MVPA (R2 = 0.228) change. Conclusions Changes in intention and action planning were important correlates of MVPA change over 24 weeks. Further, changes in action self-efficacy and risk perceptions predicted changes in intention. Implications for cancer survivors: interventions that foster risk perceptions and self-efficacy, strengthen intentions, and promote action planning may be effective in promoting sustained PA change in cancer survivors.