Potential mediators of change in a physical activity promotion course for university students: Project GRAD

purpose of the study is to evaluate the performance of theoretically-derive d mediators of health behavior change. Participants were university seniors (184 females; 154 males) randomly assigned to an intervention course desig ned to promote physical activity or to a control course. Five physical acti vity outcomes and nine psychosocial mediating variables were assessed at ba seline and the end of the 16-week course. For women, the intervention had s ignificant effects on five of the mediators, including self-efficacy for ma king time, self-efficacy for resisting relapse, social support from friends , and experiential and behavioral processes of change. Among men, the inter vention improved use of behavioral processes of change but also had the uni ntended effect of increasing perceived barriers to activity. For women, sig nificant contributors to regressions explaining physical activity change we re social support from friends (for total activity) and change in self-effi cacy for resisting relapse (for vigorous exercise). For men, significant ex planatory variables included change in enjoyment (for total activity), chan ge in self-efficacy for resisting relapse (for strength exercise), and chan ge in benefits (for moderate intensity activity). For both sexes, there wer e significant findings in the unexpected direction. Across the five physica l activity outcomes, hypothesized mediators were inconsistent and weak cont ributors to the models. Investigating mediators of behavior change has the potential to stimulate improvements in theories and interventions.