Skeletal muscle weakness is associated with wasting of extremity fat-free mass but not with airflow obstruction in patients with chronic obstructive pulmonary disease.

Skeletal muscle weakness is a prominent problem in many patients with chronic obstructive pulmonary disease (COPD).The aim of the study was to determine the relation between skeletal muscle function, body composition, and lung function in COPD (emphysema and chronic bronchitis) patients and healthy volunteers.In 50 patients with chronic bronchitis, 49 patients with emphysema, and 28 healthy volunteers, skeletal muscle function was assessed by handgrip and linear isokinetic dynamometry. Whole-body and subregional fat-free mass (FFM) were assessed by dual-energy X-ray absorptiometry.Whole-body and extremity FFM were significantly lower in patients with emphysema (P <0.001) and chronic bronchitis (P <0.05) than in healthy volunteers, but trunk FFM was significantly lower only in patients with emphysema (P <0.001). Extremity FFM was not significantly different between the COPD subtype groups, despite significantly lower values for whole-body and trunk FFM (P <0.05) in patients with emphysema. Absolute skeletal muscle function (P <0. 001) and muscle function per kilogram of whole-body FFM were significantly lower in both COPD subtype groups than in healthy volunteers (P <0.05), but no significant difference was found between patients with chronic bronchitis and those with emphysema. Muscle function per kilogram of extremity FFM was not significantly different between the 3 groups and was not associated with forced expiratory volume in 1 s.Skeletal muscle weakness is associated with wasting of extremity FFM in COPD patients, independent of airflow obstruction and COPD subtype.