Preserved metabolic reserve capacity in skeletal muscle of post-infarction heart failure patients

It has been proposed that exercise capacity during whole body exercise in post-infarction congestive heart failure (CHF) patients is limited by skeletal muscle function. We therefore investigated the balance between cardiopulmonary and muscular metabolic capacity. CHF patients (n=8) and healthy subjects (HS, n=12) were included. Patients with coronary artery disease (CAD, n=8) were included as a control for medication. All subjects performed a stepwise incremental load test during bicycling (similar to 24 kg muscle mass), two-legged knee extensor (2-KE) exercise (similar to 4 kg muscle mass) and one-legged knee extensor (1-KE) exercise (similar to 2 kg muscle mass). Peak power and peak pulmonary oxygen uptake (VO2peak) increased and muscle-specific VO2peak decreased with an increasing muscle mass involved in the exercise. Peak power and VO2peak were lower for CHF patients than HS, with values for CAD patients falling between CHF patients and HS. During bicycling, all groups utilized 2429% of the muscle-specific VO2peak as measured during 1-KE exercise, with no difference between the groups. Hence, the muscle metabolic reserve capacity during whole body exercise is not different between CHF patients and HS, indicating that appropriately medicated and stable post-infarction CHF patients are not more limited by intrinsic skeletal muscle properties during whole body exercise than HS.