Evidence supporting the existence of an exercise anaerobic threshold.

In this paper, we provided evidence to support the concept that work above the anaerobic threshold, measured by the V-slope method, is, in fact, performed partially anaerobically. In contrast, work performed below the anaerobic threshold is totally aerobic (Figure 2, 4 and 5). The VO2 at the transition from aerobic to partial anaerobic metabolism must depend on cardiovascular performance since it regulates the capillary PO2 level needed for O2 diffusion transport into the mitochondria (Figure 1). At high work rates, the capillary PO2 needed for the oxygen requirement might not be met by the cardiovascular oxygen supply. This would result in the oxygen consumed being less than the oxygen required by the working tissue (Figure 2), with the oxygen equivalent difference necessarily coming from anaerobic metabolism. The consequences are increased lactate formation and metabolic acidosis, and the physiological and biochemical disturbances which result from the latter.