Limb muscle dysfunction in COPD: effects of muscle wasting and exercise training

Lower-limb muscle weakness has often been reported in COPD, and contributes to exercise intolerance. Controversial information is available regarding upper-limb muscle adaptations and the influence of muscle wasting on muscle weakness. We investigated leg and arm muscle function in 59 stable COPD patients (GOLD stage III) with preserved fat-free mass (FFM) and in 28 patients with reduced FFM relative to age- and sex-matched healthy control subjects and studied the effects of 8 wk of whole-body exercise training.

FFM was measured with bioelectrical impedance analysis. Isokinetic quadriceps (F-leg) and biceps strength (F-arm), as well as quadriceps (E-leg) and biceps endurance (E-arm) were determined with a Biodex dynamometer. Exercise training consisted of cycle ergometry, treadmill walking, weight training, and gymnastics during 5 d.wk.

F-leg (76.2 +/- 3.6 vs 118.2 +/- 6.3 N.m, P < 0.001) and F-arm (25.6 +/- 1.3 vs 38.1 +/- 2.1 N.m, P < 0.001) were significantly and similarly reduced in the COPD patient group compared with controls. Also, E-leg (-2.13 +/- 0.12 vs -1.61 +/- 0.11, P < 0.01), but not E-arm (-2.72 +/- 0.11 and -2.47 +/- 0.13 NS), was decreased in patients. F-leg (62.4 +/- 4.3 vs 82.8 +/- 4.7 N.m, P < 0.01), but not F-arm or muscle endurance, was reduced in FFM-depleted compared with non-FFM-depleted patients. Whereas after training F-leg and E-leg significantly increased by 20% in the whole COPD group, biceps muscle function remained unchanged.

Lower- and upper-limb muscle dysfunction was observed in COPD patients, irrespective of the presence of FFM depletion. Generalized muscle weakness suggests systemic muscular involvement, although the preserved arm endurance and the poor response of arm performance to exercise training is indicative for intrinsic differences in muscular adaptations between leg and arm muscles.