VO2 Max Explained
VO2 Max is often used as a measure of fitness. This metric refers to the amount of oxygen the body can use during exercise. For the muscles to create movement, like pedaling the bike, they need oxygen. The harder the workload, the more oxygen that's needed. During exercise respiration rate increases.
One of the reasons breathing becomes more rapid is to increase the amount of oxygen coming into the body. But not all oxygen that is inhaled is actually used, in fact much of it never reaches the muscles and its eventually exhaled.
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An athlete with a higher VO2 max can use more of that oxygen that they breathe in. They can do this because their bodies have adapted to exercise and training. Fitter or more trained athletes experience adaptations that allow the body to use more of the oxygen they breathe in. A few examples include:
More blood vessels to get oxygen to muscles
More red blood cells flowing through those vessels to carry more oxygen
A stronger heart that can pump out more blood in each beat
How is it measured?
There are a number of ways to find VO2 Max, some more accurate than others. Many fitness watches can give an estimate of VO2 max and many of these have been shown to hold up well when compared to lab based testing. Another method is to use exercise tests like a Cooper test which uses data from a 12 minute run. These tests also estimate VO2 max.
VO2 Max testing can also be done using a machine that measures the content of oxygen in exhaled air. This is done as a ramp test, which means that the athlete has to run or ride to exhaustion, the test keeps getting harder until they can't go any longer. During the test, exhaled oxygen is analyzed to see how much the body was able to use. The less oxygen in the expired air, the higher the VO2 max. The image above shows a VO2 Max test being administered.
How is it used?
For most people VO2 max is used as a way to measure progress. By using the same test throughout the season, it's possible to see how fitness is changing. The more reliable the test, the more useful the data will be.
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VO2 max can also be used by coaches to set workouts. It can been used as an alternative to power or heart rate zones.