Deficits in muscle strength, mass, quality, and mobility in people with chronic obstructive pulmonary disease

Purpose—Mid-thigh intramuscular fat (IF), a feature of reduced muscle quality, is an important predictor of self-reported mobility loss in the elderly. This study compared measures of muscle strength, mass, IF, and mobility in people with COPD and healthy subjects. Associations between measures of muscle strength, mass, IF and mobility were explored. Methods—Knee extensors muscle strength was assessed with an isokinetic dynamometer. Crosssectional area (CSA) and IF of the thigh muscles were measured with computerized tomography. Mobility was assessed with the Repetitive Sit-To-Stand (RSTS), Self-Selected Gait Speed (SSGS) and Six-Minute Walk Distance (6MWT) tests. Results—Twenty-one people of mean ± SD age 71.3 ± 8.1 years with COPD and a percentage predicted force expiratory volume in one second (FEV1) of 47.2 ± 12.9 and 21 healthy subjects matched for age (67.4 ± 8.6), gender and body mass participated in the study. People with COPD showed reduced average knee extensors strength (29%;p=0.016) CSA of the thigh muscles (17%;p=0.007) and mobility measures (~23%;p≤0.001). Knee extensors and flexors IF was twofold greater in people with COPD (p≤0.005). Measures of knee extensors muscle strength, mass and IF were not associated with mobility measures. Conclusions—Compared with healthy controls, people with moderate to severe COPD show marked deficits in muscle strength, mass, quality as well as mobility. More studies with larger sample size are required to elucidate whether any of these muscle deficits can explain mobility impairments in COPD.