Overview
Why Activity Alters Glucose
Working muscle takes up glucose to make energy. During aerobic activity such as brisk walking, cycling, or swimming, muscle contraction moves glucose transporters to the cell su...
Working muscle takes up glucose to make energy. During aerobic activity such as brisk walking, cycling, or swimming, muscle contraction moves glucose transporters to the cell surface even when insulin levels are low. Glucose may therefore fall during activity without any change in the prescribed insulin dose. For a person using insulin or an insulin secretagogue, the problem is that circulating insulin cannot rapidly decrease when exercise begins. Muscle glucose uptake rises while insulin continues to drive glucose into cells. The result can be hypoglycemia during activity or soon afterward. The risk does not end when the exercise session ends. Muscles replenish glycogen stores and insulin sensitivity remains higher after activity, so glucose can continue to decline for as long as 48 hours. Delayed hypoglycemia is particularly likely after prolonged or unfamiliar activity, especially when insulin or a secretagogue is active. Not every form of exercise lowers glucose immediately. Intense resistance exercise or short bursts of maximal activity can trigger catecholamine release and hepatic glucose output, causing a transient glucose rise. A post-exercise elevation does not automatically mean that extra...