Study objectives: The purpose of this study was to compare the effects of endurance training only to endurance plus strength (combined) training in a randomized trial of patients with COPD.
Methods: Twenty-four patients completed the study: 11 patients in the combined training group (FEV(1) 45 +/- 5% predicted), and 13 patients in the endurance training group (FEV(1) 40 +/- 4% predicted) [mean +/- SE]. Muscle strength, quality of life, exercise performance, and quadriceps fatigability were measured before and after rehabilitation.
Results: Combined training led to significant improvements in quadriceps (23.6%), hamstring (26.7), pectoralis major (17.5%), and latissimus dorsi (20%) muscle strength. Endurance training alone did not produce significant improvements in muscle strength: quadriceps (1.1% decrease), hamstring (12.2% increase), pectoralis major (7.8% increase), and latissimus dorsi (2.8% decrease). The increase in strength after training was significantly greater in the combined group compared to the endurance group for the quadriceps and latissimus dorsi muscles but not for the hamstring and pectoralis major muscles. Six-minute walk distance, endurance exercise time, and quality of life (as measured by the Chronic Respiratory Questionnaire) significantly increased in both groups after rehabilitation with no significant differences in the extent of improvement between groups. The extent of improvement in quadriceps fatigability after training (assessed by quadriceps twitch force before and after exercise) was not significantly different between groups.
Conclusion: Strength training can lead to significant improvement in muscle strength in elderly patients with COPD. However, this improvement in muscle strength does not translate into additional improvement in quality of life, exercise performance or quadriceps fatigability compared to that achieved by endurance exercise alone.