VT1 and VO2
A cursory search online will generate a lot of data on running performance, VO2max, lactate and ventilatory thresholds. The opinions from various sources can be overwhelming and leave you wondering – how does this help me or How do I use this info?
Let me try to simplify it a bit-
When you run, it can be imagined that the body is like an engine that burns fuel to generate power for the run. The bigger the engine the more fuel it burns and better the performance. Burning fuel requires oxygen. One way to know the size of the engine is to know the amount of Oxygen it is using. This is the idea behind measuring VO2- Volume of oxygen consumed. In a direct laboratory based measurement, the amount of Oxygen breathed in and out is measured with the difference having been utilised by the body-
Oxygen taken in – Oxygen breathed out = Amount of oxygen used by the body
This equation will give an idea about the size of the human engine. Now, you get better performance when you have a more powerful engine in a light weight car. Hence to express the performance the oxygen consumption is noted as oxygen consumed per kilo body weight in a minute- ml of O2/Kg/min
As the intensity of exercise increases, the oxygen consumption increases as your engine continues to work harder. At one point, despite an increase in exercise intensity, the oxygen consumption does not rise as your engine has reached its maximum output. This is VO2max.
Having a big engine capacity really helps in a long run. However you never run a long run at your maximum capacity. Therefore the engine output you can maintain for a long time becomes more significant. Its like saying your car can go at 200 kmph but it’s most efficient and gives the best mileage at 80 kmph.
This lower than maximum level that can be maintained is the Ventilatory Threshold 1 (VT1). In some laboratory tests instead of measuring oxygen, the waste product, Lactic acid is measured. Consider Lactic acid as the waste gases produced by the car when the engine is working. The harder the engine works, the more the exhaust. Lactic acid produced in the muscle, seeps into blood and can be checked to see how hard the engine is working. There is a lot of correlation between VT1 and the Lactate threshold 1.
In my experience Good amateur runners who run a full Marathon between 3:15 and 3:30 hover around the 48-50 ml/kg/min mark and their VT1 is 85% of the maximum limit. Which means that they can go hard for long resulting in great times.
Non Laboratory tests for VO2peak (not max since it’s an estimate) include the beep test, yoyo test and many others which are incremental exercise tests to exhaustion
Non Laboratory tests for VT1 include the talk test as described here-
Next time I will be discussing how these 2 levels change in regular marathon runners over a 6 month training period.