Mechanisms of Adaptation to Exercise in Health and Chronic Obstructive Pulmonary Disease (COPD); Oxidative Stress Links Aging, Activity and Mobility

Oxidative stress, defined as an imbalance between pro and antioxidant molecular species in favor of the former, has recently been recognized as a potential mechanism in the peripheral muscle dysfunction associated with COPD. a series of studies are proposed to better understand the role and source of oxidative stress in the skeletal muscle of patients with COPD. Specifically, three main aims will address the following questions regarding COPD, skeletal muscle, and oxidative stress: where is oxidative stress most prevalent, why does oxidative stress occur, and what are the consequences of oxidative stress in COPD? the overall hypothesis to be tested is that COPD results in a shift toward greater intramuscular oxidative stress and this is, at least in part, responsible for the diminished mechanical efficiency and greater peripheral muscle fatiguability during muscular work often associated with this disease. The vascular consequence of this augmented free radical load is altered vascular function and a disruption of the local matching of perfusion and metabolism in skeletal muscle during exercise. These crucial changes result in a cascade of factors such as local hypoxia and elevated vascular shear stress, entering a vicious cycle that leads to the generation of more free radicals, especially during physical work. It is proposed that this imbalance between pro and antioxidant potential, toward oxidative stress, plays a significant role in the attenuated exercise capacity and reduced muscle fatigue resistance associated with COPD.