Comparison of the Acute and Long-Term Effects of Exercise on Glucose Control in Type I Diabetes

To determine the long-term effect of exercise training on glucose control, 13 subjects with type I diabetes and 7 control subjects performed 45 min of cycle exercise three times per wk for 12 wk. The acute blood glucose response, the long-term effect on glucose control (glycosylated hemoglobin and fasting plasma glucose), and changes in nutrient intake were assessed. Fitness as measured by VO₂ MAX increased in both control (33.8 ± 1.7 to 43.2 ± 3.5 ml/min/kg) and diabetic (38.7 ± 3.3 to 46.5 ± 3.6 ml/min/kg) (P < 0.05) subjects although body weight remained unchanged. In the diabetic subjects, an acute glucose-lowering effect occurred with each exercise session throughout the 12-wk training period (225.8 ± 16.1 to 148.5 ± 16.8 mg/dl, P < 0.001). However, fasting plasma glucose and glycosylated hemoglobin remained essentially unchanged (pretraining, 193.7 ± 27.5 mg/dl and 10.7 ± 0.3%; 6-wk training, 192.5 ± 27.1 mg/dl and 10.7 ± 0.03%; 12-wk training, 202 ± 30.1 mg/dl and 10.3 ± 0.8%). Total caloric intake as assessed by diet history increased significantly on exercising days (2569–2849 kcal, P < 0.05). Although plasma glucose decreases acutely with exercise, increased caloric intake on exercising days obviates a long-term effect of training on glucose control. More precise guidelines and recommendations as to exercise timing and nutrient intake, likely based on self-monitoring of blood glucose, are required to achieve a beneficial effect of exercise training on metabolic control in type I diabetes.