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Response to One-Legged Cycling in Patients With COPD^*

^* From the Department of Respiratory Diagnostic and Evaluation Services (Mr. Dolmage), West Park Healthcare Centre; and Department of Medicine (Dr. Goldstein), University of Toronto, Toronto, ON, Canada.

Correspondence to: Roger S. Goldstein, MD, West Park Healthcare Centre, 82 Buttonwood Ave, Toronto, ON, Canada M6M 2J5; e-mail: rgoldstein{at}westpark.org

Abstract

Background: In patients with COPD, exercise intensity is often limited by the ventilatory system. We hypothesized that by exercising with a smaller muscle mass, ventilatory-limited patients would perform more high-intensity, muscle-specific work. The study objectives were as follows: (1) to determine the limitations of exercising with a smaller muscle mass, compared with conventional two-legged exercise; and (2) to determine the endurance time, using the same muscle-specific intensity, during one-legged vs two-legged exercise.

Methods: Nine patients (mean ± SD FEV₁, 36 ± 13% of predicted) completed incremental exercise, and nine other patients (mean FEV₁, 42 ± 16% of predicted) completed constant-power exercise. Nine healthy subjects (FEV₁, 104 ± 14% of predicted) completed both tests. All subjects completed tests using two-legged and one-legged pedaling.

Results: Peak oxygen uptake (O₂peak) was similar during one-legged and two-legged incremental exercise among patients (difference, 0.03 L/min; 95% confidence interval [CI], – 0.10 to 0.16 L/min; p = 0.60), as were ventilation and dyspnea scores. O₂peak was lower during one-legged vs two-legged exercise (– 0.57 mL/min; 95% CI, – 0.81 to – 0.32 mL/min; p < 0.001) among healthy subjects with substantial ventilatory and heart rate reserve. Patients endured one-legged pedaling at a constant power longer than two-legged pedaling (16.97 min; 95% CI, 9.98 to 23.96 min; p < 0.001), resulting in greater work (12.48 kilojoules [kJ]; 95% CI, 2.58 to 22.39 kJ; p = 0.02). Healthy subjects completed similar work (– 4.02 kJ; 95% CI, – 18.59 to 10.55 kJ; p = 0.54) with one-legged vs two-legged pedaling.

Conclusion: These observations demonstrate the effectiveness of using one-legged exercise at the same muscle-specific intensity in extending the duration of exercise among patients with COPD. This has important implications for training approaches designed to enhance exercise function among ventilatory-limited patients.

Key Words: exercise tolerance • lung diseases, obstructive • muscle, skeletal • oxygen consumption

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