Distribution of muscle mass and maximal exercise performance in patients with COPD.

Abstract

STUDY OBJECTIVE: To investigate the distribution of reduction in lean body mass (LBM) and whether LBM in legs (LBMlegs) can be a determinant of maximal exercise performance in COPD patients. METHODS: Thirty-eight male outpatients with COPD (mean +/- SD FEV1, 47.4 +/- 24.0% of predicted) who underwent complete pulmonary function testing were classified into two groups according to FEV1 expressed as a percentage of predicted value. Group A comprised 21 patients with mild-to-moderate airflow limitation (FEV(1) > or =35% predicted), and group B comprised 17 patients with severe airflow limitation (FEV1 < 35% predicted). LBM, which represents skeletal muscle mass, was measured by dual energy x-ray absorptiometry (DXA) and was assessed separately in arms, legs, and trunk. Maximal oxygen uptake VO2max was measured during maximal exercise on a cycle ergometer. RESULTS: LBM in each region was expressed as a percentage of ideal body weight (IBW). LBM in arms (LBMarms)/IBW, LBMlegs/IBW, and LBM in trunk (LBMtrunk)/IBW were significantly depleted in group B compared with group A (p < 0.01). LBMlegs expressed as a percentage of total LBM (LBMlegs/total LBM) was significantly lower in group B (p < 0.05), although there was no significant difference in LBMarms/total LBM and LBMtrunk/total LBM between the two groups. VO2max correlated significantly with LBMlegs/IBW in group A, but not in group B. By stepwise regression analysis, LBMlegs/IBW appeared to be a significant predictor of VO2max in group A, while not in group B. CONCLUSION: LBMlegs was a significant predictor of maximal exercise performance in patients with mild-to-moderate airflow limitation, but not in patients with severe airflow limitation who had disproportional reduction in LBMlegs.