Physician-based activity counseling: Intervention effects on mediators of motivational readiness for physical activity

In theory-based interventions for behavior change, there is a need to exami ne the effects of interventions on the underlying theoretical constructs an d the mediating role of such constructs. These two questions ale addressed in the Physically Active for Life study, a randomized trial of physician-ba sed exercise counseling for older adults. Three hundred fifty-five patients participated (intervention n = 181, control n = 174; mean age = 65.6 years ). The underlying theories used were the Transtheoretical Model, Social Cog nitive Theory and the constructs of decisional balance (benefits and barrie rs), self-efficacy and behavioral and cognitive processes of change. Motiva tional readiness for physical activity and related constructs were assessed at baseline, 6 week, and 8 months. Linear or logistic mired effects models were used to examine intervention effects on the constructs, and logistic mixed effects models were used for mediator analyses. At 6 weeks, the inter vention had significant effects on decisional balance, self-efficacy, and b ehavioral processes, but these effects were not maintained at 8 months. At 6 weeks, only decisional balance and behavioral processes were identified a s mediators of motivational readiness outcomes. Results suggest that interv entions of greater intensity and duration may be needed for sustained chang es in mediators and motivational readiness for physical activity among olde r adults.