Glucocorticoid-induced muscle atrophy. The role of exercise in treatment and prevention.

Glucocorticoids have catabolic effects on skeletal muscle. These effects demonstrate fiber type specificity: Type IIB fibers are most susceptible and type I fibers least susceptible to the atrophy effects of glucocorticoids. Exercise training has been used frequently to counteract glucocorticoid-induced muscle atrophy. Studies have demonstrated that both resistance exercise and endurance exercise are effective in attenuating this atrophy. The cellular mechanisms mediating the attenuating effect of exercise on glucocorticoid-induced atrophy are not completely understood. More research is needed to further elucidate the details of these mechanisms and to determine the most efficacious exercise protocols for deterring glucocorticoid-induced muscle atrophy. Exercise evaluation of patients with glucocorticoid-induced myopathy and subsequent exercise prescription must be individualized and based on the patient's initial muscle function and medical status.