One of the most important complaints due to respiratory diseases is progressive exercise intolerance. COPD is the most prevalent and disabling chronic respiratory disease. Improvement of patients function and survival are along with reduction of utilization of health care resources among the most important goals in the management of COPD patients. There are few effective therapies. Pulmonary rehabilitation aims to improve patients’ function but cannot reverse pulmonary abnormalities. It is now recognized that peripheral muscle dysfunction adversely affects clinical outcomes in COPD. Most reports of attempts to improve muscle function in COPD have focused on exercise training. However, abnormalities in the level of circulating and other substances have been described. This suggests that supplementation therapies may be rational for these patients