Increased peripheral insulin sensitivity and muscle mitochondrial enzymes but unchanged blood glucose control in type I diabetics after physical training

Nine male, insulin-dependent diabetic patients participated in a 16-wk training program consisting of 1 h of jogging, running, ball games, and gymnastics, performed 2-3 times/wk. The training resulted in an 8% increase of maximal oxygen uptake (P < 0.01). Insulin sensitivity as determined by the insulin clamp technique increased 20% (P < 0.05). Glycosylated hemoglobin showed no change (10.4 ± 0.7% versus 11.3 ± 0.5%), 24-h urinary glucose excretion was not reduced, and home-monitored urine tests were unchanged. The frequency of hypoglycemic attacks did not change during the training period and body weight remained constant. There was a 14% fall in plasma cholesterol (P < 0.01) and a rise in the proportion of HDL-cholesterol from 24 ± 2% to 30 ± 3% (P < 0.01). Thigh muscle oxidative capacity increased, as indicated by a 24% increase in succinate dehydrogenase activity (P < 0.05). The number of capillaries/muscle fiber increased 15% (P < 0.01). However, as the mean muscle fiber cross-sectional area increased to a similar extent (11%, P < 0.05), capillary density (cap X mm^-2) was unchanged. In conclusion, this study demonstrates that physical training in insulin-dependent diabetics results in increased peripheral insulin sensitivity, a rise in muscle mitochondrial enzyme activities, decreased total plasma cholesterol levels, and unchanged blood glucose control. The findings suggest that in the absence of efforts to alter dietary regulation and insulin administration, physical training consisting of 2-3 weekly bouts of moderate exercise may not of itself improve blood glucose control in type I diabetes.