Building Competency in Diabetes Education THE ESSENTIALS

TREATMENT MODALITIES: LIFESTYLE| 5-43

GLUCOSE METABOLISM AND EXERCISE

During exercise, energy demands on the body, especially in the working muscles, can increase substantially. To meet these energy demands, skeletal muscle uses the following sources of energy at a greatly increased rate: its own stores of glycogen and triglycerides, free fatty acids (FFAs) derived from the breakdown of adipose tissue, and triglycerides and glucose released from the liver (191). For the person without diabetes, BG levels are remarkably well maintained during exercise in order to preserve central nervous system function, but those metabolic adjustments that preserve normoglycemia during exercise are essentially lost in people with type 1 diabetes. As a consequence, when people with diabetes have insufficient insulin in circulation, an excessive release of counterregulatory hormones during exercise may increase already high levels of glucose and ketone bodies and can lead to diabetic ketoacidosis. Conversely, the presence of high circulating levels of exogenous insulin can attenuate or even prevent the increased mobilization of glucose and other substrates induced by exercise, resulting in hypoglycemia. Exercise can increase insulin sensitivity for up to 48 hours or more after the activity (192). People with type 2 diabetes who take insulin or insulin secretagogues may have similar risks, but in general, hypoglycemia in this population tends to be less of a problem. Although most types of activities tend to cause BG to decline due to increased glucose disposal and insulin sensitivity, intense exercise may cause a rise in BG. An increase in glucose production that exceeds the increase in glucose disposal may result during and especially after brief, very intense exercise (e.g. intense resistance training, hockey, basketball and competitive track and field) (193).