Theoretically, the gas exchange threshold (GET) and ventilatory threshold (VT) estimate the exercise intensity above which anaerobic adenosine triphosphate (ATP) production must support aerobic metabolism.2 Thus, in theory, exercise intensities below the GET and VT are nonfatiguing and are maintained from aerobic ATP production only, while those above these thresholds are fatiguing and utilize anaerobic plus aerobic ATP production. The GET and VT usually occur at approximately 50% to 60% of the maximal oxygen consumption rate (V

• O2 max) in untrained to moderately trained individuals,

but occur at 80% of V • O2 max or above in highly trained endurance athletes.