The anaerobic threshold measurement to evaluate exercise performance.

During exercise, the oxygen consumption above which aerobic energy production is supplemented by anaerobic mechanisms, and which results in a significant increase in lactate, is termed the anaerobic threshold (AT). This power output has important functional implications because it is a demarcation of the work rate above which metabolic acidosis accelerates the stimulation to breathing, and exercise endurance becomes reduced. The justification for relating lactate increase to tissue anaerobiosis during exercise is presented, and the gas exchange methods for measuring the AT are described. The form of work affects the AT, treadmill being about 10% greater than cycling in sedentary subjects. It is useful for predicting the ability of the subject to sustain a given work rate for a prolonged period and for determining the VO2 above which there is cardiovascular insufficiency in meeting tissue O2 requirements.