Effects of Exercise Training on Glucose Homeostasis: The HERITAGE Family Study
2005
Boulé, Normand G. | Weisnagel, S John | Lakka, Timo A. | Tremblay, Angelo | Bergman, R. N. | Rankinen, Tuomo | Leon, Arthur S. | Skinner, James S. | Wilmore, Jack H. | Rao, D.C. | Bouchard, Claude
OBJECTIVE:--To determine the effect of a 20-week endurance training program in healthy, previously sedentary participants on measures derived from an intravenous glucose tolerance test (IVGTT). RESEARCH DESIGN AND METHODS--An IVGTT was performed before and after a standardized training program in 316 women and 280 men (173 blacks and 423 whites). Participants exercised on cycle ergometers 3 days per week for 60 sessions. The exercise intensity was progressively increased from 55% VO[subscript 2max] for 30 min per session to 75% VO[subscript 2max] for 50 min per session. RESULTS:--Mean insulin sensitivity increased by 10% (P < 0.001) following the intervention, but the variability in the changes was high. Men had larger improvements than women (P = 0.02). Improvements in fasting insulin were transitory, disappearing 72 h after the last bout of exercise. There were also significant mean increases in the glucose disappearance index (3%, P = 0.02) and in glucose effectiveness (11%, P < 0.001), measures of glucose tolerance and of the capacity of glucose to mediate its own disposal, respectively. The acute insulin response to glucose, a measure of insulin secretion, increased by 7% in the quartile with the lowest baseline glucose tolerance and decreased by 14% in the quartile with the highest baseline glucose tolerance (P < 0.001). The glucose area below fasting levels during the IVGTT was reduced by 7% (P = 0.02). CONCLUSIONS:--Although the effects of structured regular exercise were highly variable, there were improvements in virtually all IVGTT-derived variables. In the absence of substantial weight loss, regular exercise is required for sustained improvements in glucose homeostasis.
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