Ventilatory threshold
In kinesiology, the ventilatory threshold (VT1) refers to the point during exercise at which the volume of air breathed out (expiratory ventilation) starts to increase at an exponentially greater rate than VO2 (breath-by-breath volume of oxygen (O2)). VT1 is thought to reflect a person's anaerobic threshold — the point at which the oxygen supplied to the muscles no longer meets its oxygen requirements at a given work rate — and therefore lactate threshold — the point at which lactate begins to accumulate in the blood, because with ongoing dependence on anaerobic glycolysis, increasing amounts of CO2 need to be exhaled to accommodate its production during the conversion of lactic acid to lactate.