Exploring the construct validity of the transtheoretical model to structure physical activity interventions for individuals with serious mental illness.

OBJECTIVE Physical activity intervention research involving individuals with serious mental illness are often not based on any theoretical framework. This study examined the construct validity of the Transtheoretical Model (TTM) in individuals with serious mental illness to guide future physical activity interventions. METHODS Fifty-four individuals completed surveys that asked about their current stage of change for physical activity, self-efficacy, and perceived advantages and disadvantages of being more physically active. RESULTS Most individuals reported being in the preparation stage of the TTM. As individuals approached the action and maintenance stages, self-efficacy and perceived benefits of physical activity increased significantly. Although perceived disadvantages decreased with each successive stage, this change was not significant. CONCLUSIONS This study's findings support the TTM's application in this population to structure physical activity interventions given that self-efficacy, perceived benefits of and barriers to physical activity differed across stages and changes were in the direction predicted by theory.