Chest. June 2004;125(6):2036-2045.

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 chronic obstructive pulmonary disease (COPD).

Methods

Twenty-four patients completed the study: 11 patients in the combined training group (FEV₁ 45% +/- 5% predicted), and 13 patients in the endurance training group (FEV₁ 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 muscle strength: quadriceps (23.6%), hamstring (26.7), pectoralis major (17.5%), and latissimus dorsi (20%). 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.

Commentary

Pulmonary rehabilitation (PR) is known to improve exercise capacity for patients with COPD. Many PR programs include a combination of endurance/aerobic fitness training and strength training of upper and lower extremity muscles. However, the optimal strategies for exercise prescription and for combining these training strategies remain uncertain. Mador and colleagues have conducted a randomized controlled trial comparing endurance training to endurance training combined with strength training in 24 patients with severe COPD. Consistent with the results of prior studies, the investigators found that strength training lead to greater improvements in muscle strength as compared with endurance training alone. However, there was no significant difference between groups in 6-minute walk distance, endurance exercise time, or quality of life as assessed by the Chronic Respiratory Questionnaire. Interestingly, the investigators also assessed the effect of combined modality training vs endurance training alone on quadriceps fatigability. Combined training did not lead to any appreciable incremental benefit, that is, reduction, in quadriceps fatigability as assessed by quadriceps twitch force pre- and post-exercise. Thus, based on studies conducted to date, the addition of strength training to endurance training for patients with COPD appears to lead to improvements in muscle strength and mass, but no definitive improvement in other measures of functional capacity. However, further studies are needed to determine whether combined modality training may lead to functional improvements perhaps not measured by the 6-minute walk test or lab-based measures of exercise endurance, such as performance of activities of daily living, eg, dressing, bathing, and performance of household chores.