Impaired glucose tolerance (IGT) is a transitory state between normoglycemia and frank diabetes. One in three individuals with IGT will develop type 2 diabetes within 10 years if left untreated. A strong rationale exists for the implementation of strategies designed to reverse or stabilize the deterioration in glucose homeostasis in individuals with IGT. Recent physical activity guidelines from the Centers for Disease Control and Prevention and the American College of Sports Medicine have suggested that intermittent moderate-intensity exercise is beneficial and can improve the health status of these individuals. Specifically, the guidelines recommend that every American should accumulate 30 min of moderate- intensity physical activity per day. The current guidelines are based predominantly on epidemiological data, and very little clinical evidence exists that this level of physical activity can significantly improve glycemic status. More intense exercise prescriptions would appear to be needed to improve glucose tolerance and insulin action. Although higher exercise intensity is a key determinant for improvements in glucose homeostasis, it may produce mechanical and oxidative damage that can result in transitory impairments in insulin action and glucose tolerance. Therefore, the optimal exercise inten-sity for an individual with IGT appears to lie between these two extremes.