Testing physical activity mediators in an intervention for sedentary older adults

The aim of this study was to identify mediators of physical activity (PA) behavior change in a resistance training and lifestyle activity intervention for sedentary older adults. Participants (N = 44) were randomized to an intervention based on Social Cognitive Theory (SCT) or a control group. PA and SCT constructs (i.e., intention, barriers self-efficacy, task self-efficacy, outcome expectations, social support and behavioral strategies) were assessed using validated questionnaires. The intervention had a significant effect on PA (difference of 70 minutes of PA/week, p = 0.02). Changes in task self-efficacy represented 10% of the intervention effect, but none of the SCT variables were significant mediators of PA. This trial provided evidence for the utility of the intervention to improve fitness and physical activity, yet behavior change was not explained by the theoretical constructs measured. These results emphasize the need for theory development and integration that extend beyond traditional social cognitive models.