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Effects of one-legged exercise training of patients with COPD.

BACKGROUND
Most patients with severe COPD are limited by dyspnea and are obliged to exercise at low intensity. Even those undergoing training do not usually have increased peak oxygen uptake (Vo2). One-legged exercise, at half the load of two-legged exercise, places the same metabolic demands on the targeted muscles but reduces the ventilatory load, enabling patients to increase work capacity. The purpose of this study was to determine whether one-legged exercise training would improve aerobic capacity compared with two-legged training in stable patients with COPD.


METHODS
Eighteen patients with COPD (mean FEV(1), 38 +/- 17% of predicted [+/- SD]) were randomized to two groups after completing an incremental exercise test. Both trained on a stationary cycle for 30 min, 3 d/wk, for 7 weeks. Two-legged trainers (n = 9) cycled continuously for 30 min, whereas one-legged trainers (n = 9) switched legs after 15 min. Intensity was set at the highest tolerated and increased with training.


RESULTS
Both groups increased their training intensity (p < 0.001) and total work (p < 0.001). After training, the change in peak Vo2 of the one-legged group (0.189 L/min; confidence interval [CI], 0.089 to 0.290 L/min; p < 0.001) was greater than that of the two-legged group (0.006 L/min; CI, - 0.095 to 0.106 L/min; p = 0.91). This was accompanied by greater peak ventilation (4.4 L/min; CI, 1.8 to 7.1 L/min; p < 0.01) and lower submaximal heart rate (p < 0.05) and ventilation (p < 0.05) in the one-legged trained group.


CONCLUSION
Reducing the total metabolic demand by using one-legged training improved aerobic capacity compared with conventional two-legged training in patients with stable COPD.