Glucose clearance in aged trained skeletal muscle during maximal insulin with superimposed exercise

Insulin and muscle contractions are major stimuli for glucose uptake in ske letal muscle and have in young healthy people been shown to be additive. We studied the effect of superimposed exercise during a maximal insulin stimu lus on glucose uptake and clearance in trained (T) (1-legged bicycle traini ng, 30 min/day, 6 days/wk for 10 wk at similar to 70% of maximal O-2 uptake ) and untrained (UT) legs of healthy men (H) [n = 6, age 60 +/- 2 (SE) yr] and patients with Type 2 diabetes mellitus (DM) (n = 4, age 56 +/- 3 yr) du ring a hyperinsulinemic (similar to 16,000 pmol/l), isoglycemic clamp with a final 30 min of superimposed two-legged exercise at 70% of individual max imal heart rate. With superimposed exercise, leg glucose extraction decreas ed (P < 0.05), and leg blood flow and leg glucose clearance increased (P < 0.05), compared with hyperinsulinemia alone. During exercise, leg blood flo w was similar in both groups of subjects and between T and UT legs, whereas glucose extraction was always higher (P < 0.05) in T compared with UT legs (15.8 +/- 1.2 vs. 14.6 +/- 1.8 and 11.9 +/- 0.8 vs. 8.8 +/- 1.8% for H and DM, respectively) and leg glucose clearance was higher in T (H: 73 +/- 8, DM: 70 +/- 10 ml.min(-1).kg leg(-1)) compared with UT (H: 63 +/- 8, DM: 45 +/- 7 ml.min(-1).kg leg(-1)) but not different between groups (P > 0.05). F rom these results it can be concluded that, in both diabetic and healthy ag ed muscle, exercise adds to a maximally insulin-stimulated glucose clearanc e and that glucose extraction and clearance are both enhanced by training.