EFFECT OF TRAINING ON INTERACTION BETWEEN INSULIN AND EXERCISE IN HUMAN MUSCLE

Exercise adds to the effect of maximal insulin on whole body glucose uptake. Training increases contraction-induced glucose transport measured in vitro but not glucose utilization in human muscle exercising during normoinsulinemia. We studied whether exercise adds to the effect of maximal insulin in human muscle and whether trained (T) and untrained (UT) muscles differ. Six healthy men [23 +/- 0.4 (SE) yr] trained one leg for 10 wk, 6 days/wk, 30 min/day at 70% of one-legged maximal O-2 uptake while keeping the other leg sedentary. At 16 h after the last training bout, both femoral veins and a radial artery were catheterized and 150-min hyperinsulinemic (480 mU.min(-1).m(-2)) euglycemic clamp was performed. During the final 30 min, subjects performed two-legged bicycling at 76 +/- 0.3% of maximal heart rate. During exercise, blood flow (597 +/- 45 vs. 572 +/- 37 ml.min(-1).kg(-)1), O-2 uptake (74 +/- 6 vs. 68 +/- 6 ml O-2.min(-1).kg(-1)), and carbohydrate oxidation (88 +/- 10 vs. 81 +/- 7 mg.min(-1).kg(-1)) increased similarly (P > 0.05) in T and UT legs, respectively. Arteriovenous glucose difference decreased (P < 0.05) during exercise but tended to remain higher in T (0.47 +/- 0.04) than in UT (0.41 +/- 0.05 mol/l) (P < 0.1). Glucose uptake increased with exercise, the increase being higher in T than in UT (change: 28 +/- 5 vs. 23 +/- 5 mg.min(-1).kg(-1); P < 0.05). During exercise, lactate release (195 +/- 78 vs. 534 +/- 137 mu mol min-l kg(-1)) and indirectly determined glycogenolysis (57 +/- 13 vs. 87 +/- 15 mg min(-1) kg(-1)) were lower (P < 0.05) in T vs. UT. Partly by increasing blood flow, exercise adds to the effect of maximal insulin on glucose uptake in human muscle. Training increases this effect of acute exercise without influencing blood flow.