Improved Insulin Sensitivity in Carbohydrate and Lipid Metabolism After Physical Training

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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.