Exercise and Glycemic

Exercise is not metabolically uniform. During aerobic activity, contracting skeletal muscle can take up glucose through insulin-independent pathways, so glucose disposal rises even when circulating insulin is not high. For a person with diabetes, this usually lowers blood glucose. The risk increases when insulin from a recent dose is still active or when an insulin secretagogue, such as a sulfonylurea, is stimulating insulin release. Muscle glucose uptake can then exceed hepatic glucose output. The result is hypoglycemia during activity or shortly afterward. Glucose may continue to fall after exercise ends. Muscles replenish glycogen and remain more insulin-sensitive, which can lower glucose for as long as 48 hours. A patient who exercises in the afternoon may therefore develop delayed or nocturnal hypoglycemia despite an acceptable immediate postexercise value. Short, intense, or anaerobic activity can produce the opposite pattern. Catecholamines stimulate hepatic glucose release, causing a temporary rise in glucose. A brief postexercise elevation after sprinting or heavy lifting does not automatically mean that extra correction insulin is needed; the nurse must consider activity type, active insulin, glucose trend, and ketone status.