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 (FEV1 ≥ 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
(V̇o2max) 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. V̇o2max 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 V̇o2max 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