Muscular Exercise and Metabolism in Male Juvenile Diabetics I. Energy Metabolism during Exercise

Abstract

The purpose of the present study was to compare energy metabolism during exercise in diabetics with that of previously studied non-diabetic subjects. Each of eight, well-regulated, insulin-treated, juvenile diabetics participated in five separate experiments: one at rest and one each involving bicycle ergometer exercise at 20%, 50%, 70%, and 90% of each subject's Maximal Aerobic Power (Max V˙_O2). The subjects were fasting, and without insulin on the day of the experiment. Blood glucose concentration (BGC) showed changes similar to those found in non-diabetic subjects at similar work loads. Endurance was generally somewhat less in diabetics. Reasons for cessation of exercise were different for the two groups at exercise work loads higher then 50% max V˙_O2. For both groups at 50% max V˙_O2, the cause of work stop was a hypoglycemic BGC. At 70% max V˙_O2 this was also the cause in non-diabetics but seldom in diabetics. A high pre-exercise BGC was not a necessary criterion for endurance. Carbohydrates contributed a larger percentage of the energy metabolism at higher work loads in diabetics, as previously found in non-diabetics. Rates of fat utilization were found to be similar for the two groups. It was concluded that trained patients with a well-regulated diabetes have an exercise energy metabolism which is not different in principle from that of a similar group of trained non-diabetic subjects.

Key Words:

• Blood glucose concentration
• carbohydrate metabolism
• diabetes mellitus
• endurance
• energy metabolism
• exercise
• fat metabolism
• plasma free fatty acid levels
• rates of fat and carbohydrate metabolism