Exercise training decreases ventilatory requirements and exercise-induced hyperinflation at submaximal intensities in patients with COPD: Chest 2005;128:2025–34.

Abstract

Study objectives We hypothesized that endurance exercise training would reduce the degree of hyperinflation for a given level of exercise and thereby improve submaximal exercise endurance. Methods Twenty-four patients with COPD (mean FEV1, 36.4±8.5% of predicted [± sd ]) undertook a high-intensity cycle ergometer exercise training program for 45 min, three times a week for 7 weeks. Before and after training, the patients performed both an incremental exercise test to maximum and a constant work rate (CWR) test on a cycle ergometer at 75% of the peak work rate obtained in the pretraining incremental test. Ventilatory variables were measured breath-by-breath, and inspiratory capacity (IC) was measured every 2 min to assess changes in end-expiratory lung volume. Results After training, the increase in peak oxygen uptake was not statistically significant; however, the peak work rate increased by 12.9±10.3 W ( P 0.01 ). For the CWR test performed at the same work rate both before and after training, ventilation and breathing frequency (f) were lower after training (average, 1.97 L/min and 3.2 breaths/min, respectively; P 0.01 ) and IC was greater (by an average of 133 mL, P 0.05 ), signifying decreased hyperinflation. The increase in IC at the point of termination in the shortest CWR test for each individual (defined as isotime) correlated well with both the decreased f ( r = 0.63 , P = 0.001 ) and with the increase in CWR exercise endurance (average, 13.1 min, r = 0.46 , P = 0.023 ). Conclusions Exercise training in patients with severe COPD dramatically improves submaximal exercise endurance. Decreased dynamic hyperinflation may, in part, mediate the improvement in exercise endurance by delaying the attainment of a critically high inspiratory lung volume.