The evaluation of a fourth-generation multi-theory model (MTM) based intervention to initiate and sustain physical activity.

Background: The United States Department of Health and Human Services (USDHHS)recommends that adults achieve 150 minutes per week of moderate-intensity aerobic activity.Most African American women do not meet these guidelines. The purpose of this study was to determine the efficacy of an intervention based on the fourth generation, multi-theory model (MTM) of health behavior change for initiating and sustaining physical activity among African American women when compared to a first generation, knowledge-based intervention. Methods: The randomized controlled trial (RCT) utilized a pre-test, post-test and 6-week followup evaluation with an experimental (n=25) group and a comparison group (n=23). Process evaluation for satisfaction and program fidelity was conducted along with impact evaluation for changes in MTM constructs, intent to initiate and sustain physical activity, minutes of physical activity, body mass index (BMI), waist circumference and blood pressure in hypertensives. Results:The MTM-based intervention proved significantly efficacious in increasing the minutes of physical activity from pre-test mean of 37 minutes to 172 minutes at follow-up (mean difference135.08 minutes, 95% CI: 106.04 to 164.13, P<0.0001), reducing waist circumference from pretest mean of 39 inches to 38 inches at follow-up (mean difference -1.12 inches, 95% CI: -1.70 to-0.545, P<0.001) and modifying the MTM construct of changes in physical environment from a mean of 7 units at pre-test to 9 units at follow-up (mean difference 2.08 units, 95% CI: 0.73 to 3.43, P<0.004) when compared to the knowledge-based intervention over time. Conclusion: There were directional improvements in the mean scores for most of the study variables over time for the MTM intervention group and statistically significant improvement in minutes of physical activity and waist circumference.