Metabolic responses to exercise. Effects of endurance training and implications for diabetes

In this study, some important metabolic responses to exercise will be discussed, and aspects of particular interest for patients with diabetes mellitus will be emphasized. Alterations in the metabolic responses to exercise induced by physical endurance training and consequences of training for metabolism of plasma lipids and lipoproteins will be discussed. Glucoregulation during exercise is not perfect in normal subjects and is less so in patients with diabetes mellitus. For instance, during intense exercise, large increases in the plasma glucose concentration occur and a state of insulin resistance exists for a few hours after intense exercise. Even so, increased sensitivity to insulin is found the day after intense exercise and also shortly after more moderate intensity exercise, both in healthy subjects and in patients with diabetes mellitus. Increased sensitivity to insulin is also found after endurance training, whereas insulin sensitivity is decreased after inactivity. Exercise training increases the ability of muscle to take up and oxidize free fatty acids during exercise and also increases the activity of the enzyme lipoprotein lipase in muscle. The activity of lipoprotein lipase in muscle correlates with muscle insulin sensitivity. This might explain why insulin resistance is often associated with hypercholesterolemia, hypertriglyceridemia, and low high-density lipoprotein cholesterol.