VO2 max is defined as the maximal amount of oxygen the body is able to extract and use to support work performed by the body. It is therefore an indirect measure of the aerobic power of the body, which is controlled by complex interactions between neural (brain and nervous system), cardiovascular (heart and lungs) and skeletal muscle factors. The equation for VO2 max it is equal to the product of stroke volume (the maximum volume of blood the heart ejects in a contraction) and the arterio-venous difference (the difference between the saturation of the arterial blood and that of the venous blood). The aerobic power of the body will change constantly throughout a well-designed running program due to physiological changes and therefore its usefulness in designing a program and determining running capabilities is questionable. This article aims to explain the reason VO2 max is a better indicator of fitness levels than running potential and conditioning program design.

Many physiological adaptations occur as one becomes more fit, some of these include: an increased size and efficiency of the heart, increased blood volume, increased muscle capillarization (more capillaries developed) and increased mitochondria (small bodies in the muscle cell that use oxygen to burn fat and make energy) density. So it should be obvious then that if we increase the stroke volume or the a-v difference (or both), the VO2 max will increase. With a more muscular heart and an increased blood volume you may increase the stroke volume and with a greater extraction of oxygen from the blood at the muscle level (more mitochondria) you can increase the a-v difference, which equals a higher VO2 max. Thus, VO2 max is a good indicator of physical condition or fitness.

The question arises whether it is beneficial to know your VO2 max to develop an ideal training regimen or whether a high VO2 max automatically determines you as a great runner. From evidence accumulated by Prof. Tim Noakes and his colleagues at the Sports Science Institute of South Africa the answer is that knowing your VO2 max will not answer either question. Here