Vigorous Physical Activity Determines Magnitude of Cardiovascular Risk Factor Changes Following Physical Activity Interventions

Abstract

Physical activity (PA) is a significant determinant of good health yet it continues to decline in most countries. Interventions promoting PA are therefore important public health initiatives. PURPOSE: To measure the impact of 40-days intensive PA on CV and metabolic risk factors, and to follow subjects for 6 months to document both PA patterns and risk factor changes. METHODS: Two 40-day programs were designed to increase PA among insufficiently active adults randomly assigned to a: (1) pedometer-based (n=251), or (2) group-based intervention arm (n=187). An active control group was also followed (n=135). The pedometer subjects were advised about the 10,000-step goal and provided diaries and pedometers. Group subjects used heart rate monitors to record all daily sessions. Half the sessions were led while the others were performed individually. Sessions gradually progressed to vigorous levels of activity. Health risk factors including fitness parameters were measured pre- and post-intervention, and at 3 and 6 months follow-up. RESULTS: Adherence rates at post intervention, 3 and 6 months were 84, 69 and 61% for pedometer and 86, 76 and 71% for group subjects. Significant improvements occurred in cholesterol, BMI, VO2max, waist girth, and total and vigorous PA measures during both 40-day intervention arms. Repeated measures ANOVA showed significant group × intervention interactions for all these variables (group > pedometer, p<0.01). Regression analysis showed changes for cholesterol and VO2max, between each test over the study period, were significantly related to the corresponding changes in vigorous PA but not moderate PA (p<0.0001). BMI changes were related to both. Repeated measures ANOVA (using intention to treat analysis) showed significant improvements remained at 6 months for VO2max, BMI, and both total and vigorous minutes of PA for both intervention arms. Improvements remained for cholesterol at 3 months. CONCLUSION: Significant changes in risk factor profiles were found in both interventions over the 40-day program and most improvements remained at 6 months. Vigorous PA was significantly associated with the magnitude of risk factor changes. Supported by the South Australian Department of Health and Australian Research Council.