Construct Validity of the Stages of Change of Exercise Adoption for Different Intensities of Physical Activity in Four Samples of Differing Age Groups

Purpose. To examine whether the stages of change of exercise adoption appropriately address strenuous, moderate, and mild intensities of physical activity.Design and Setting. Secondary analysis of four data sets investigating transtheoretical model (TTM) constructs for exercise adoption.Subjects. Four samples of differing age groups (adolescents, n = 400; college students, n = 240; adults, n = 346; seniors, n = 504).Measures. Stage of change algorithm for exercise adoption and self-reported physical activity.Results. Multivariate analysis of variance (MANOVA) results showed that stages of change were distinguished by strenuous and moderate but not mild exercise in the adolescent, college student, and adult sample. In the senior sample, stage differences were found in the frequency of exercising (equivalent for moderate to strenuous exercise) and the frequency of walking (equivalent for mild exercise). Bivariate correlation coefficients as well as sensitivity, specificity, and related quality indices decreased respectively from strenuous to moderate to mild exercise and from exercising to walking.Conclusions. Results provide additional support for the construct validity of the stages of change for strenuous and moderate intensities of physical activity. Development of a new stage assessment instrument for mild intensities of physical activity is recommended. Limitations include use of a different validation measure of exercise behavior in the senior sample.