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

Study objective: To investigate the distribution of reduction in lean body mass (LBM) and whether LBM in legs (LBMlegs) can be a determinant of maxima l exercise performance in COPD patients Methods: Thirty-eight male outpatients with COPD (mean +/- SD FEV1, 41.4 +/ - 24.0% of predicted) who underwent complete pulmonary function testing wer e classified into two groups according to FEV, expressed as a percentage of predicted value. Group A comprised 21 patients with mild-to-moderate airfl ow limitation (FEV1 greater than or equal to 35% predicted), and group B co mprised 17 patients with severe airflow limitation (FEV1 < 35% predicted). LBM, which represents skeletal muscle mass, nas measured by dual energy x-r ay absorptiometry (DXA) and was assessed separately in arms, legs, and trun k. Maximal oxygen uptake ((V) over dot o(2)max) was measured during maximal exercise on a cycle ergometer. Results: LBM in each region was expressed as a percentage of ideal body wei ght (IBW). LBM in arms (LBMarms)/IBW, LBMlegs/IBW, and LBM in trunk (LBMtru nk)/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) wa s significantly lower in group B (p < 0.05), although there was no signific ant difference in LBMarms/total LBM and LBMtrunk/total LBM between the two groups. (V) over dot o(2)max correlated significantly with LBMlegs/IBW in g roup A, but not in group B. By stepwise regression analysis, LBMlegs/IBW ap peared to be a significant predictor of (V) over dot o(2)max in group A, wh ile not in group B, Conclusion: LBMlegs was a significant predictor of maximal exercise perform ance in patients with mild-to-moderate airflow limitation, but not in patie nts with severe airflow limitation who had disproportional reduction in LBM legs.