Exercise and insulin sensitivity: A review

Physical activity has a beneficial effect on insulin sensitivity in normal as well as insulin resistant populations. A distinction should be made betw een the acute effects of exercise and genuine training effects. Up to two h ours after exercise, glucose uptake is in part elevated due to insulin inde pendent mechanisms, probably involving a contraction-induced increase in th e amount of GLUT4 associated with the plasma membrane and T-tubules. Howeve r, a single bout of exercise can increase insulin sensitivity for at least 16 h post exercise in healthy as well as NIDDM subjects. Recent studies hav e accordingly shown that acute exercise also enhances insulin stimulated GL UT4 translocation. Increases in muscle GLUT4 protein content contribute to this effect, and in adddition it has been hypothesized that the depletion o f muscle glycogen stores with exercise plays a role herein. Physical traini ng potentiates the effect of exercise on insulin sensitivity through multip le adaptations in glucose transport and metabolism. in addition, training m ay elicit favourable changes in lipid metabolism and can bring about improv ements in the regulation of hepatic glucose output, which is especially rel evant to NIDDM. It is concluded that physical training can be considered to play an important, if not essential role in the treatment and prevention o f insulin insensitivity.