Integrating the theory of planned behavior with the processes and stages of change in the exercise domain

Objectives: The purpose of the present study was to examine a model of exercise behavior change that integrated the theory of planned behavior (TPB; Ajzen, I. (1991). The theory of planned behaviour. Organizational Behaviour and Human Decision Processes, 50, 179–211) with the processes and stages of change from the transtheoretical model (Prochaska, J. O. & Velicer, W. F. (1997). The transtheoretical model of health behavior change. American Journal of Health Promotion, 12(1), 38–48). The general hypothesis was that the relationships between the processes of change and the stages of change would be mediated by the social cognitive constructs contained within the TPB (i.e. attitude, subjective norm, perceived behavioral control, and intention). Design: Cross-sectional survey. Methods: Participants were 427 undergraduate students who completed a self-administered questionnaire in groups of 20 to 50. Mean age of the sample was 19.7 years (SD =4.0) and 73% were female. Results: Stepwise hierarchical regression analyses indicated that the TPB mediated eight of the 10 relationships between processes of change and stages of change. Moreover, perceived behavioral control was predicted exclusively by behavioral processes of change whereas attitude was predicted by both cognitive and behavioral processes. Finally, exploratory multivariate analysis revealed that each pair of adjacent stages was discriminated by different social cognitive constructs and different processes of change. Conclusions: It is concluded that the proposed integrated model produced important theoretical insights into how and why people successfully change their exercise behavior but that longitudinal and experimental studies are needed before any definitive conclusions can be drawn.