Does the theory of planned behavior mediate the effects of an oncologist's recommendation to exercise in newly diagnosed breast cancer survivors? Results from a randomized controlled trial.

This randomized trial examined the effects of 2 oncologist-based exercise interventions--recommendation only (RO) and recommendation plus referral (RR)--versus usual care (UC) on social-cognitive constructs from the theory of planned behavior (TPB). The authors also examined whether the TPB mediated the significant effect of the RO intervention on exercise and explained the null effect of the RR intervention. Independent t tests revealed that both interventions had significant effects on TPB constructs; however, only the RO intervention impacted perceived behavioral control (PBC). Path analyses indicated that PBC was the only construct with a direct effect on exercise and that it mediated the effect of the RO intervention on exercise and explained the null effect of the RR intervention.     

Physical Activity and Social Cognitive Theory: A Test in a Population Sample of Adults with Type 1 or Type 2 Diabetes

The purpose of the study was to test the Social Cognitive Theory (SCT; Bandura, 2004 ) for explaining physical activity (PA) in a large population sample of adults with type 1 or type 2 diabetes. Study objectives: (1) test the fit of the SCT structure in the total sample, and the diabetes sub-types; (2) determine the SCT structural invariance between the type 1 and type 2 groups; and (3) report explained variance and compare strength of association for the SCT constructs in predicting PA for both type 1 and type 2 groups. In all, 2,311 individuals with type 1 or type 2 diabetes were assessed on their self-efficacy, outcome expectancies, impediments, social support, goals, and physical activity at baseline and 1,717 (74.5%) completed these assessments again at 6 months. Multi-group Structural Equation Modeling was conducted. The findings provide evidence for the utility of the SCT in the diabetes samples. The SCT fits individuals with type 1 and type 2 diabetes except for SCT impediments, which appear to be obstructing goal-setting in individuals with type 2 diabetes only. Promotion of health behavior should target self-efficacy to set goals and change behavior. Outcome expectancies and social support are also important factors for setting goals and behavior performance.