Improved Insulin Sensitivity in Carbohydrate and Lipid Metabolism After Physical Training

Abstract

To estimate physical training effects quantitatively, the relationship between tissue sensitivity to exogenous insulin (glucose metabolism determined by euglycemic insulin-clamp technique) and maximal oxygen uptake (V̇O₂ max) was defined in 9 well-trained athletes and 14 untrained subjects with normal glucose tolerance.

Tissue sensitivity to exogenous insulin in the athletes was significantly higher than in the controls (P < 0.001). Seven untrained subjects continued the physical exercise program. After physical training for 1 month, glucose metabolism increased from 40.3±3.9 µmol/kg/min to 42.2±4.4 µmol/kg/min (p < 0.05) and V̇O₂ max also increased significantly (P < 0.05). During euglycemic hyperinsulinemia, both plasma FFA (P < 0.001) and glycerol (P < 0.05) decreased rapidly after physical training. Glucose metabolism directly correlated with V̇O₂ max (P < 0.001).

These results suggest that (1) the euglycemic insulin-clamp technique provides a reliable estimate of training effects, (2) tissue sensitivity to physiologic hyperinsulinemia is 46% higher in trained athletes, and (3) physical training improves insulin sensitivity not only in glucose metabolism but also in lipid metabolism.

Key words

training effects - insulin-clamp technique - insulin sensitivity - glucose metabolism - lipid metabolism