In normal subjects, the amount of blood lactate that accumulates during exercise is related to the intensity of exercise achieved and is a marker of the degree of muscle activation attained . Several authors have reported that a significant increase in blood lactate also occurs during exercise in patients with chronic obstructive pulmonary disease (COPD) , while others have indicated that the onset of lactate increase may occur at relatively low exercise work rates in these individuals . Because of a lower exercise capacity, the peak lactate achieved in COPD patients is often less than that of normal subjects . As a result, the importance of exercise-induced lactic acidosis in exercise limitation in COPD may have been minimized .
Using serial lactate concentration measurements during exercise, previous studies have shown that the lactate kinetics are abnormal in COPD patients; for a given submaximal exercise level, the concentration of blood lactate is greater in patients than in normal subjects .