Higher skeletal muscular metabolic reserve capacity in COPD patients than healthy subjects

We investigated the interaction between skeletal muscle exercise capacity and central restrictions using exercise modalities, which recruit differing levels of muscle mass in eight patients chronic obstructive lung disease (COPD) (FEV1 % of predicted; 35 [SE 4%]) and eight healthy controls. Subjects performed conventional bicycling, two-leg knee extensor (2-KE) and single-leg knee extensor (1-KE) exercises. Maximal values for pulmonary circle dot O-2 (VO2max), power output, blood lactate, heart rate, blood pressure, and arterial oxygen saturation of hemoglobin were registered. VO2max in controls was 2453 (210), 1468 (124), and 976 (76) mL/min during bicycling, 2-KE and 1-KE, respectively. The COPD patients achieved 48% (P < 0.05), 62% (P < 0.05), and 81% (P=0.10) of the control values. The mass-specific VO2max (VO2max/exercising muscle mass) during 1-KE was 345 (25) and 263 (30) mL/kg/min (P < 0.05) in controls and COPD patients, respectively. During 2-KE the controls and COPD patients achieved 85% (4%) and 67% (5%) (P=0.06) of the mass-specific circle dot O-2 during 1-KE, while during bicycling they achieved 31% (2%) and 17% (1%) (P < 0.05), respectively. The COPD patients have central restrictions when exercising with a relatively small muscle mass (2-KE) and have a higher muscular metabolic reserve capacity than controls during whole body exercise.