Finally, a decrease in lactate degradation has also been reported to influence the increase in blood lactate during exercise .
Several factors may have contributed to the greater exercise-induced increase in blood lactate observed in COPD patients. However, several lines of evidence suggest that abnormal lactate kinetics in patients are related to poor skeletal muscle oxidative capacity. In a previous report, we found a significant inverse relationship between the increase in arterial lactate during exercise and aerobic enzyme activities in patients with COPD . A similar observation has been reported in chronic heart failure patients, a clinical condition where the oxidative capacity of the skeletal muscle is also reduced . Moreover, in 11 patients with COPD involved in a program of exercise training, we reported improvement in skeletal muscle oxidative capacity and reduction in exercise lactic acidosis for a given exercise level . Altogether, these studies reinforce the notion that altered skeletal muscle oxidative capacity plays a role in early lactic acid production .