Effect of rehabilitative exercise training on peripheral muscle remodelling in patients with COPD: targeting beyond the lungs

Locomotor muscle dysfunction and weakness are frequently observed in patients with Chronic Obstructive Pulmonary Disease (COPD). In addition to intolerable sensations of dyspnoea which importantly contribute to exercise limitation, intrinsic muscle abnormalities have also been implicated in inducing leg muscle fatigue/discomfort during exercise in these patients. It is, however, uncertain whether these intrinsic muscle abnormalities are linked to a specific 'myopathy' or they constitute a consequence of the disease. Besides muscle disuse, other factors which may contribute to peripheral muscle dysfunction include systemic inflammation, oxidative and nitrosative stress, chronic hypoxia, corticosteroid use and malnutrition. There is clear evidence that rehabilitative exercise training induces significant skeletal muscle fibre remodelling and improvements in functionality in the absence of changes in lung function. The ultimate purpose of this review is to identify and summarize the results of studies implementing diverse types of exercise training on peripheral muscle fibre phenotypic and genotypic modifications in patients with COPD.