Enhanced insulin sensitivity and lower waist-to-hip ratio in master athletes.

The effect of long-term aerobic exercise training on insulin action was determined in older individuals by comparing insulin sensitivity and maximal responsiveness in 11 master athletes [63.5 +/- 1.9 (SE) yr] and 10 age- and body fat-matched sedentary individuals. Maximal aerobic power was higher and the waist-to-hip ratio (WHR) was lower in the athletes, but there were no differences in body weight, percent body fat, or fat-free mass between groups. Fasting plasma glucose levels and glucose and insulin responses during oral glucose tolerance tests were lower in the athletes. The insulin concentration producing a half-maximal increase in glucose disposal (EC50) during a three-step hyperinsulinemic-euglycemic glucose clamp was 41% lower in the athletes than in controls (483 +/- 30 vs. 822 +/- 132 pmol/l, P < 0.05), whereas maximal responsiveness was comparable (81.0 +/- 4.4 vs. 85.5 +/- 8.3 mumol.kg fat-free mass-1.min-1, P = not significant). The EC50 correlated with maximal aerobic power (r = -0.62, P < 0.01) and WHR (r = 0.52, P < 0.05), but in multiple regression analyses WHR was the only variable independently related to EC50. These results indicate that long-term aerobic exercise training is associated with enhanced insulin sensitivity and a lower WHR in older individuals. This finding suggests that regular aerobic exercise may prevent the age-associated increase in abdominal obesity and insulin resistance.