Fat-free mass depletion is associated with poor exercise capacity irrespective of dynamic hyperinflation in COPD...

In patients with COPD, we investigated the effect of the fat-free mass (FFM) on maximal exercise capacity and the relationship with changes in operational lung volumes during exercise.

In a cross-sectional study 57 patients (16 females; age 65 ± 8 y) were consecutively assessed by resting lung function, symptom-limited cardiopulmonary exercise test, and body composition by means of bioelectrical impedance analysis to measure the FFM index (FFMI; in kilograms per square meter).

Patients were categorized as depleted (n = 14) or nondepleted (n = 43) according to FFMI. No significant difference in gender, age, and resting lung function was found between depleted and nondepleted patients. When compared with nondepleted COPD patients, the depleted COPD patients had a significantly lower O2 uptake at the peak of exercise and at anaerobic threshold as well as at peak oxygen pulse, oxygen uptake efficiency slope (OUES), and heart rate recovery (HRR) (P < .05 for all comparisons), but similar inspiratory capacity/total lung capacity at the peak of exercise. Moreover, they also reported significantly higher leg fatigue (P < .05), but not dyspnea on exertion. In all patients, significant correlations (P < .01) were found between FFMI and peak oxygen pulse, OUES, HRR, and leg fatigue.

This study shows that FFM depletion plays a part in the reduction of exercise capacity in COPD patients, regardless of dynamic hyperinflation, and is strictly associated with poor cardiovascular response to exercise and to leg fatigue, but not with dyspnea.