I often receive telephone calls from runners wanting to know if it would be possible to measure their VO2 max. My standard answer is something along the lines that it is, indeed, possible. However, I then go on to ask why they want to have their VO2 max measured? There is usually one of two replies. Firstly, I am told, by knowing his or her VO2 max the runner will know that esoteric time that he or she is ultimately capable of running for some particular race distance, and therefore their ultimate potential as a runner. Secondly, once their VO2 max is known it will be possible to prescribe the ultimate personalised training schedule. My response to both is that knowing the VO2 max of a runner does not answer either question.

It is widely believed that the VO2 max is genetically determined and unchanging and that an individual is born with either a high or low "max". Someone with a high value has muscles that are capable of utilising large amounts of oxygen and a cardiovascular system capable of delivering this volume of oxygen. The athlete is able to run at a maximum aerobic speed that this oxygen supply can sustain. In this paradigm it does not appear to matter whether the runner is unfit or superbly fit, the outcome of a VO2 max test remains the same. However, it is intuitively obvious that when fit the athlete can run much faster on the treadmill than when unfit. Thus, since VO2 max is genetically determined and does not change (in this model), VO2 max would be reached at a relatively slow running speed when a runner is unfit compared to when very fit, when a much higher speed can be reached on the treadmill. This means that in a totally unfit world-class runner we would measure a high VO2 max (say 75 ml/kg/min or higher) at a speed of maybe 17 km/hr on the treadmill. When very fit the same athlete will reach the same VO2 max at a speed of about 24 km/hr. The problem is that such a high VO2 max is never measured at a speed of just 17 km/hr. This would be almost impossibly inefficient. The theory of a genetically set and unchanging VO2 max therefore begins to appear a little shaky.

This concept of VO2 max evolved from misinterpretation of the data of early experimental work. It was believed that as an athlete ran faster and faster during a treadmill test, the muscles needed an increasing volume of oxygen, a process, which continued until the supply of oxygen, became limiting or the ability of the muscle to utilise oxygen was exceeded. At this point there would be no further increase in oxygen uptake. This plateau in oxygen utilisation was regarded as the VO2 max of the runner. If high, then the athlete had great genetic potential. However, in addition to the problem described in the previous paragraph, half of all runners tested in exercise laboratories never have a plateau in their oxygen uptake. Instead, the oxygen uptake is still increasing when the athlete cannot continue the test. The conventional view of VO2 max now appears to be even more suspect.

Consider a different scenario. A runner on a treadmill requires a certain amount of oxygen to run at a given speed. When the speed is increased, there is a corresponding increase in the volume of oxygen needed to run at the higher speed. The runner runs faster and faster, with corresponding increases in the oxygen required, until something other than oxygen supply to the muscle prevents any further increase in running speed. The volume of oxygen being used by the muscle when this occurs is at a maximum value, which is then termed the VO2 max. With this theory, oxygen requirement merely follows the increase in running speed, until a peak running speed and therefore peak oxygen requirement (VO2 max) is reached. It is easy to see why the VO2 max value will change as a runner gets fitter and can run faster. Within this framework, the genetically determined limit of VO2 max is determined by the highest running speed that can be reached, or in some instances a true limit in the supply and utilisation of oxygen by the muscle.

The inability to use the VO2 max test as a predictor of future performance in someone who can still improve his or her running by using a scientifically designed training programme becomes obvious. A great training-induced increase in running speed will result in a substantial change in VO2 max.

Knowing a VO2 max value is not going to assist in the construction of a training programme any more than will knowing current race times. There are, however, some potential uses of a VO2 max test. When constructing a training programme for someone who has not run any races and who therefore has no race times, a VO2 max test will help give an indication of the current ability of the athlete on which to base training schedules. Secondly, if done regularly, the test can provide information about the efficacy of a training programme. Finally, its fun to compare ones' own VO2 max value with that of elite runners, who have VO2 max values higher than 70 ml/kg/min. What is yours in comparison?