The Effect Of Aerobic Training Intensity On Insulin Sensitivity

Abstract

It has been estimated that nearly 26% of the adult U.S. population has impaired glucose tolerance. There exists a strong correlation between moderate intensity aerobic exercise and increased insulin sensitivity (%S). The relationship between higher exercise intensities and increased insulin sensitivity remains unclear. PURPOSE: The purpose of this study was to evaluate the effect of various levels of aerobic intensity on %S in young adult males and females. METHODS: 45 healthy subjects (22.2 ± 3.9 years; 169 ± 9 cm; 74.5 ± 17.8 kg) were matched for age, gender and VO2max. Exercise intensity was calculated as percentage of heart rate reserve (HRR). Subjects were randomly assigned to either moderate-intensity (50% HRR), vigorous-intensity (75% HRR), maximal-intensity interval (95/50% HRR) or a non-exercising control group. The Homeostasis Mode (HOMA2) was used to assess %S. Subjects completed a 6-week training protocol on a stationary bicycle ergometer. Weekly duration and frequency of training varied to ensure equivalent energy expenditure across groups. Differences in training variables among groups were analyzed using a 2-way ANOVA with repeated measures on one factor (time). Correlations of VO2max and %S were assessed at pre- and post-test, as well as the change in VO2max vs. change in %S. RESULTS: Significant increases occurred following training in VO2max in the vigorous (15.4%) and maximal (14.2%) intensity groups (p < 0.001). However, there were no significant changes in %S in any exercising groups or the non-exercising control group. Although there was no effect of training on %S, a slight trend for a relationship between VO2max and %S was observed across all subjects in post-test data (p = 0.17) and for change of VO2max versus change in %S (p = 0.21). CONCLUSION: Training intensity did not significantly affect %S; it did, however, significantly affect VO2max.