Effect of training intensity on insulin sensitivity as evaluated by insulin tolerance test

The purpose of this study was to evaluate the role of exercise intensity in the effect of physical training on insulin sensitivity. The insulin tolera nce test (ITT) was applied to quantify insulin sensitivity. Eighteen health y, young, untrained men and women participated in a 4-week, five times per week, 1-h per session bicycle-ergometer training program. Training consiste d of 3-min bouts of cycling interspersed with 2 min at a lower exercise int ensity. Intensities were 80 and 40% of pretraining maximal power output ((W ) over dot(max)) in the high-intensity (HI) and 40 and 20% (W) over dot(max ) in the low-intensity (LI) group. The insulin sensitivity index (ISindex) was similar in the HI and LI group before the training intervention [mean ( SD) -0.1898 (0.058) and -0.1892 (0.045), respectively]. After training, the ISindex was -0.2358 (0.051) (P = 0.005 vs pretraining) in the HI group and -0.2050 (0.035) (P = 0.099 against pretraining) in the LI group. We conclu de that improvements in insulin sensitivity are more pronounced with high-i ntensity training, when exercise frequency and duration are kept similar. W e further conclude that the ITT is suitable for use in intervention studies .