The ventilatory threshold is the intensity at which ventilation begins to rise in excess of VO2. It is best demonstrated by plotting V̇E/V̇O2 and V̇E/V̇CO2 on the same graph (as above). The ventilatory threshold is the point just before V̇E/V̇O2 begins to rise without a similar rise in V̇E/V̇CO2.
V̇E: volume of gas expired (L/min); V̇CO2: volume of carbon dioxide produced (L/min); V̇O2: volume of oxygen consumed (L/min).
