The Great VO2 max Myth
The Great VO2 max Myth by Doctor Andrew Bosch
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.
VO2 max measured
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?
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VO2max has been shown to change in response to fitness training in all levels of athletes and in cardiac rehab patients. Hence it is not genetically determined, but is modified by exercise training, or lack of activity. Anyone who claims to have reached their genetically determined VO2 max, may find that value change with different training or coaching.
Further- the oversimplicity of even saying something is genetically determined is an affront to our understanding of genes and environment as cooperating, not determinative or additive factors.
We may agree on this point.
The typical limiting factor of VO2 max is not utilization by the musculature, but rather ability of the cardiovascular system to deliver oxygen to the muscles, and return CO2 to the lungs. Hence it is more often used in cardiac rehab than in bodybuilding or weight training.
No doubt the limits of VO2 max may have some genetic basis, and developing or losing muscle mass can affect the VO2 max. But a host of scientific studies have demonstrated that for most individuals VO2 max is primarily a measure of cardiovascular fitness, and responds to cardiovascular training or inactivity.
While comparisons between individuals and groups are of interest, the primary valid use of VO2 max is to measure changes in individual performance. It is also used in combination with CO2 production, and sometimes urinalysis, to estimate the carbohydrate, fat, and protein contributions as energy sources in research subjects and training athletes. VO2 max may not be the gold standard in exercise physiology, but it is a darn useful measure.
Hi Dr Bosch,
I’m a second year ExPhys student and just getting my head around all of the technical aspects of fitness testing and VO2max in particular. As part of my research into VO2 I’ve come across an apparent ‘controversy’ in difference of opinion between Dr T. Noakes (modern model) and A.V.Hill (classical model), http://www.ncbi.nlm.nih.gov/pubmed/9140894.
I’m curious to know if your article here falls more on the Noakes or Hill side of the discussion?
Jason
PS Please feel free to visit my blog (http://skeptifit.wordpress.com/) and comment – I attempt to take a skeptical and scientific approach to popular fitness based topics.
Hi Jason
It falls more on the Noakes side. The plateau that Hill and many text books refer to is seldom seen in practice. I am well aware for instance that the textbook definition of VO2 max being reached is the plateau, or even a dip. But its very protocol dependent. We have a student doing some work at the moment where he is getting higher maxes in a “reverse” test. We start at a high workload, then as the person fatigues, we reduce the workload. That way a higher max is achieved than in any ramp protocol done on the same person! We haven’t got it all figured out yet, but I mention it cause it shows what a weird thing this max actually is!
Sincerely
Andrew
I appreciate your response Andrew, and apologies for my delayed response.
I’ve come to the realisation over the past months that it seems very odd to stop the test when one of several conditions are met (RER > 1.15, HRmax exceeded, LA > 8mmol, or VO2 plateau) without actually specifying which condition was the limiting factor in the final result. Just stating the fact that a person/athlete had a result of, for example, 75ml/kg/min for relative VO2max doesn’t seem to really tell us anything if we don’t go on to specify that the limiting factor for this athlete was RER, or blood lactate, or that we did indeed reach the “golden plateau”. Even comparing a subject/athlete’s current VO2 test results with his previous results seems like it might not be particularly valid if the two tests were stopped by the same limiting factor, except that it tells us that the limiting factors themselves have changed for some reason (perhaps an indicator of further improvement).
Cheers,
J