Endurance exercise training reduces glucose-stimulated insulin levels in 60- to 70-year-old men and women

Background. Aging is frequently associated with development of insulin resistance and deterioration of glucose tolerance. Plasma glucose and insulin concentrations tend to be higher than in young people, even in those older individuals whose glucose tolerance is within the normal range. A sedentary life style could play a role in the development of insulin resistance and hyperinsulinemia with advancing age. Methods. We evaluated the effect of 9 mo of vigorous endurance exercise training (~80% of maximal heart rate) on the glucose-stimulated insulin response and glucose disposal rate, using the hyperglycemic clamp procedure, in 12 people aged 65 ± 1 yr (mean ± SE) with normal glucose tolerance. The post-training hyperglycemic clamps were performed ~16 h after a usual exercise session. Results. V̇O₂max increased ~23% in response to the exercise program. The plasma insulin concentration (I) during hyperglycemia (180 mg · dL^-1) was significantly lower (mean 36 ± 6 μU · mL^-1 before vs 26 ± 5 μU · mL^-1 after; p < .05) after the exercise program. Insulin action was improved by the exercise, as the glucose disposal rate (M) during hyperglycemia was unchanged despite the blunted insulin response, resulting in an increase in the M/I ratio from 24 ± 5 to 30 ± 5 (p < .05), a value similar to the M/I ratio of 33 ± 4 found in normally active young subjects. Conclusion. These results provide evidence that regular exercise is effective in reducing hyperinsulinemia and improving insulin action in 65-yr-olds to levels typical of young people.