ENDURANCE EXERCISE TRAINING REDUCES GLUCOSE-STIMULATED INSULIN LEVELSIN 60-YEAR-OLD 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 i n 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 trainin g (approximately 80% of maximal heart rate) on the glucose-stimulated insulin response and glucose disposal rate, using the hyperglycemic cl amp procedure, in 12 people aged 65 +/- 1 yr (mean +/- SE) with normal glucose tolerance. The post-training hyperglycemic clamps were perfor med approximately 16 h after a usual exercise session. Results. VO2max increased approximately 23% in response to the exercise program. The plasma insulin concentration (I) during hyperglycemia (180 mg.dL-1) wa s significantly lower (mean 36 +/- 6 muU.mL-1 before vs 26 +/- 5 muU.m L-1 after; p < .05) after the exercise program. Insulin action was imp roved by the exercise, as the glucose disposal Tate (M) during hypergl ycemia was unchanged despite the blunted insulin response, resulting i n 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 yo ung subjects. Conclusion. These results provide evidence that regular exercise is effective in reducing hyperinsulinemia and improving insul in action in 65-yr-olds to levels typical of young people.