Background and objective: The endurance time has been reported to be the most sensitive measure of improved exercise capacity in response to a variety of interventions for COPD. The aim of the present study was to determine whether the improvements in quadriceps force and measures obtained from a symptom-limited maximal test contributed to the improvements in endurance time following pulmonary rehabilitation.
Methods: Fifty-seven consecutive COPD subjects completed a 10-week pulmonary rehabilitation program. The subjects completed a symptom-limited incremental cycle ergometry test and a constant work rate test before and after pulmonary rehabilitation. Peripheral and respiratory muscle strength was also measured. The relationships between the change in endurance time and the changes obtained from the incremental test and muscle strength test were investigated.
Results: The endurance time showed the greatest improvement among the exercise capacity indices. The changes in endurance time were significantly correlated to changes in quadriceps force, peak work rate, anaerobic threshold and work efficiency on the incremental load test. In the multiple stepwise regression analysis, changes in quadriceps force and work efficiency measured on the maximal exercise test were selected.
Conclusion: These findings suggest that the improvements in endurance time after pulmonary rehabilitation may be explained by increased quadriceps force and improvements in peak work rate and work efficiency.