Physical performance and muscular characteristics in different stages of COPD

Abstract

This study has examined exercise capacity and muscle morphology in patients with different severities of chronic obstructive pulmonary disease (COPD). Twenty-three patients and 12 healthy matched controls were recruited. Based on the severity of airflow obstruction, patients were divided into two subgroups. Exercise capacity was determined using a 6-min walk test. Muscle fiber composition, fiber area and number of satellite cells/muscle fiber were determined in muscle biopsies using immunohistochemistry. A progressive decline in exercise capacity was noted with ascending disease severity. Furthermore, a correlation between reduction in exercise capacity and changes in muscle fiber composition was observed in COPD. The group with severe and very severe COPD had a lower proportion of type I and a higher proportion of type IIa fibers compared with the other groups. In severe and very severe COPD, a reduction in fiber area of type IIa fibers was also seen. The number of satellite cells/muscle fiber did not differ between the groups. In conclusion, a decline in exercise capacity occurs already in mild and moderate COPD, indicating that the 6-min walk test is a reliable indicator of disease severity. Furthermore, changes in skeletal muscle morphology are associated with disease severity while muscle regenerative capacity is not altered.

Factors Limiting Exercise Tolerance in Chronic Lung Diseases

“…Thus, it appears that the pathophysiological changes seen in mild COPD contribute to activity related dyspnea. On the other hand the notion that peripheral muscle dysfunction does not seem to be a main contributor to exercise limitation in patients with GOLD stages I and II despite that leg discomfort is a frequent symptom terminating exercise, comes from recent findings (84) demonstrating that peripheral muscle fiber-composition and fiber size area are unaffected in mild and moderate COPD. On the contrary, in GOLD stages III and IV there are alterations in fiber size and typology that are indicative of muscle wasting and of a shift toward a more glycolytic metabolic profile (84).…”

“…On the other hand the notion that peripheral muscle dysfunction does not seem to be a main contributor to exercise limitation in patients with GOLD stages I and II despite that leg discomfort is a frequent symptom terminating exercise, comes from recent findings (84) demonstrating that peripheral muscle fiber-composition and fiber size area are unaffected in mild and moderate COPD. On the contrary, in GOLD stages III and IV there are alterations in fiber size and typology that are indicative of muscle wasting and of a shift toward a more glycolytic metabolic profile (84). In other words, it appears that a decline in systemic and peripheral muscle oxygen delivery (321) to the peripheral muscles is rather an important factor causing premature lactic acidosis that accelerates peripheral muscle fatigue and discomfort in less severe patients with COPD (GOLD stages I and II).…”

An Official American Thoracic Society/European Respiratory Society Statement: Update on Limb Muscle Dysfunction in Chronic Obstructive Pulmonary Disease

“…The regenerative capacity of muscle tissue is also involved in this equation (101)(102)(103). At the molecular level, cachexia is characterized by an increased muscle proteolysis with the activation of the ubiquitin proteasome (UbP) pathway (104).…”

Practical recommendations for exercise training in patients with COPD

“…Such factors may include gas exchange abnormalities, dynamic lung hyperinflation, insufficient energy supply to the peripheral and respiratory muscles, morphological alterations in leg and diaphragm muscle fibres and reduced functional metabolic capacities [4,5]. Exercise performance will be limited by the weakest component(s) of this physiological chain.…”