Eight Week Moderate Intensity Exercise Intervention Elicits Body Composition Change In Adolescents*

Abstract

Background and Purpose. Physical inactivity is a leading cause of obesity among adolescents in the United States. Childhood and adolescent obesity that continues into adulthood leads to an increased risk for cardiovascular disease. The purpose of this study was twofold: 1) to assess the variance in heart rate (HR) and rating of perceived exertion (RPE) during exercise at a specified ventilatory response index (VRI) level, 2) to determine whether 8 weeks of exercise at a specified VRI level can elicit beneficial changes in body composition. Subjects. Sixty one adolescents (45 females, 16 males) were selected from among volunteers from a local high school. Methods. An intervention group (n=39) exercised at a VRI level of 1 for 40 minutes, 4 times a week for 8 weeks, while a control group (n=22) participated in their regularly scheduled physical education classes. Each subject's body composition was assessed at baseline and after 8 weeks. Each experimental subjects' HR, VRI, and RPE was assessed twice per exercise session. Results. A 2-factor MANOVA showed a significant (p<0.05) interaction between gender and group on change in percent body fat and in body mass index (BMI). The comparisons of the cell means showed a significant change in percentage body fat in the experimental group females versus all other groups (control group females and male control and experimental groups). The 95% confidence interval for HR, percent heart rate maximum, and RPE at the selected VRI level was 137-141 bpm, 65-69%, and 12-14, respectively. Conclusion. Eight weeks of exercise at an intensity equal to VRI level one is sufficient to elicit statistically significant body composition changes in adolescents with only one instructional session. The subjects in this study had an accuracy rate of 82% for the self-determination of VRI.