Research Library
The effect of the volume and intensity of exercise training on insulin sensitivity.
Authors: Houmard JA, Tanner CJ, Slentz CA, Duscha BD, McCartney JS, Kraus WE.
Source: J Appl Physiol. 2003 Sep 12 [Epub ahead of print]
Physical activity enhances insulin action in obese/overweight individuals. However, the exercise prescription required for the optimal enhancement is not known. The purpose of this study was to test the hypothesis that exercise training consisting of vigorous-intensity activity would enhance insulin sensitivity more substantially than moderate-intensity activity. Sedentary, overweight/obese subjects (n=154) were randomly assigned to either Control or an exercise group for 6-months: 1) Low Volume/Moderate Intensity [~12 miles walking/wk at 40-55% VO2peak]; 2) Low Volume/High Intensity [~12 miles jogging/wk at 65-80% VO2peak], and 3) High Volume/High Intensity [~20 miles jogging/wk at 65-80% VO2peak]. Training volume (mi/wk) was achieved by exercising ~115 min/wk (Low Volume/High Intensity) or ~170 min/week (Low Volume/Moderate Intensity and High Volume/High Intensity). Insulin action was measured with an insulin sensitivity index (SI) from an intravenous glucose tolerance test. In the Control group there was a decrement (P < 0.05) in SI. In contrast, all the exercise groups significantly (P < 0.05) increased SI; the relative increment in the Low Volume/Moderate Intensity and High Volume/High Intensity groups (~85%) were greater than in the Low Volume/High Intensity group (~40%). In conclusion, physical activity encompassing a wide range of intensity and volume minimizes the insulin resistance that develops with a sedentary lifestyle. However, an exercise prescription that incorporated ~170 min of exercise/wk improved insulin sensitivity more substantially than a program utilizing ~115 min of exercise/wk, regardless of exercise intensity and volume. Total exercise duration should thus be considered when designing training programs with the intent of improving insulin action.