Rationale for Training the Skeletal Muscles in Chronic Obstructive Pulmonary Disease

Skeletal muscle function is frequently impaired in patients with chronic obstructive pulmonary disease (COPD),1 even in those persons affected by mild disease.2 Whether the abnormalities are mainly due to deconditioning are more related to a systemic effect of the disease, or, indeed, result from its treatment with corticosteroids is still a matter for discussion. The main abnormalities that are described are skeletal muscle weakness, atrophy, muscle damage, excessive cell death by apoptosis, and myopathy. This topic is discussed in more detail elsewhere in this book (see Chapter 49, “Peripheral Muscle Dysfunction in Chronic Obstructive Pulmonary Disease”). Muscle weakness is associated with significant disability and can affect the overall prognosis. First, muscle weakness contributes to exercise intolerance in COPD.3,4 Second, patients with frequent hospital admissions show a greater degree of impairment of muscle strength than do patients who make less use of health care resources.5 Finally, patients with steroid-induced myopathy have a reduced survival rate.6 Recently, Marquis and colleagues7 have shown that reduced muscle bulk, as measured by midthigh crosssectional area, is an important contributor to survival, even in patients with moderate COPD. These observations suggest that reversing skeletal muscle weakness should be a target of therapy for COPD. In this chapter, the extent to which muscle dysfunction can be improved, and the strategies by which to do so, are discussed.