Andrew Hamilton looks at the science of open-water swimming, and explains how swimmers of all backgrounds could benefit –especially now that most swimming pools are closed due to the current lockdown restrictions MORE
Vo2max Defined: For years V02max has been referred to as a gold standard of aerobic fitness. It is simply a physiological index that can be measured while you are exercising.
The problem is that expensive equipment is needed to make the actual measurements, so the test is inaccessible to the public at large. During the test expired air is collected from the subject while he or she exercises and is then measured both for the volume and composition. These two factors combined can be used to calculate the actual amount of oxygen the body is able to extract from the air, transport around the body and utilise within the muscles to help produce energy.
When performing such a test, the subject will usually exercise for a short period at a number of different intensities. The entire test lasts about 15 minutes, starting at an easy intensity and gradually increasing until the subject can no longer keep with the pace, usually at the point of exhaustion. Measurements of oxygen consumption are usually taken throughout the test, because at submaximal levels they will also give an idea of what is known in the trade as ‘running economy’. Oxygen consumption will increase in a linear fashion with the rise in exercise intensity until near the point of exhaustion, where a plateau is often noticed. It is this point of plateau or exhaustion that is referred to as the V02max.
Running is not the only form of exercise that is used to determine the V02max. It makes sense for the subject to perform the type of exercise he or she is used to. This means that rowers will be tested on a rowing ergometer, runners on a treadmill, cyclists on a cycling ergometer. This is because values will vary according to your mode of exercise; values are often higher in sports where whole body activity is involved and the body mass is not supported. This is one reason why cross-country skiers often have stratospheric V02max values; not only is their activity one that uses both arms and legs but they also don’t have their weight supported as does, say a cyclist.
Naturally it makes sense that a highly trained endurance cyclist will be able to take in and use more oxygen than a sedentary counterpart, because of adaptations to the cardiorespiratory system as a result of training. Both central factors, such as heart and blood volumes, as well as peripheral factors, such as increased amounts of aerobic enzymes within the skeletal muscle, are enhanced with regular training. This is why V02max is often used as an index of endurance fitness. However, it is not the be all and end all of performance because other factors can come into play.
As readers of PP will know, V02max can certainly be raised and the untrained person is likely to enjoy the biggest gains at the start of an exercise programme. After some time, however, with years of continued training, the experienced athlete will approach a genetically determined ceiling beyond which there will be no increase in V02max, despite persistent effort. Further evidence of other factors being responsible can be seen when comparing V02max with race times. Although in the general population a good correlation exists between V02max and performance in, say, a three mile race, it is interesting to note that if you looked at a small sub-group of similarly trained athletes – for instance, the finalists in the Olympic 5OOOm – the same correlation would probably not exist between finishing position and V02max. At the sharp end of sport, other factors determine who wins and who loses, but that doesn’t mean that V02max is not important as a monitoring tool. In the sub-elite especially, it is a very effect means to monitor increases in endurance fitness.
As PP readers also know, V02max is commonly used in research. First, it can give an idea of how well trained the subjects are in a particular study. Untrained individuals might be able to use 30-40 millilitres of oxygen each minute per kilogram of body mass (a preferred method of expressing V02max is ml/Kg/min) when they are at exhaustion. A highly trained endurance athlete, at the top end of the scale, may use as much as 80ml/Kg/min, while a well-trained soccer player might pitch in at 60ml/Kg/min.
Second, if the subjects have to perform some kind of exercise trial, it is useful to express the intensity of exercise at which they are working. Although it is possible to express the intensity in terms of running speed, or the workload in watts for a rower, such absolute workloads might not require the same effort from all subjects. If a set percentage of an individual’s V02max is used, then the subjects will all be working at the same relative intensity, despite different running speeds or workloads. This will make such trials fairer, since the fitter person will be working just as hard as the less fit, even though the actual speed or workload is greater. A common intensity used in research studies is 70% of V02max because this level of effort can be maintained for a reasonable amount of time such as an hour.