What is VO2 max?
VO2 max is the maximum rate at which your body can take in and use oxygen during intense exercise. It is a strong marker of aerobic fitness and general health, and it improves with a combination of high-intensity intervals and large volumes of easy aerobic work.
What the number represents
It is usually expressed in millilitres of oxygen per kilogram of bodyweight per minute. It reflects the whole oxygen transport chain: How much blood the heart can pump, how well that blood carries oxygen, and how effectively the working muscle extracts and uses it. For most trained people, the heart's pumping capacity is the main limitation.
How it is measured
A laboratory test with a mask and a graded protocol is the accurate method. Field estimates from watches and fitness tests are convenient and useful for tracking change over time, but the absolute numbers should be treated loosely.
How to improve it
- Intervals near maximal aerobic effort: Three to five minutes hard with equal recovery, repeated four to six times, is a classic and effective format.
- Shorter, sharper intervals: 30 seconds hard with 30 seconds easy, repeated in blocks, also works well.
- High volumes of easy work: This builds the delivery machinery that the intervals then stress.
- Consistency: Meaningful change takes 8 to 12 weeks.
What limits it
Genetics set a large part of both the starting point and the ceiling. Training age, bodyweight, and current fitness all matter. Because the figure is expressed per kilogram, changes in bodyweight alter it without any change in cardiovascular function.
Why it is worth caring about
Beyond sport, cardiorespiratory fitness is consistently associated with better long-term health outcomes, and it is one of the more modifiable markers available. For athletes, a higher ceiling supports repeated efforts and faster recovery between them.
The underlying physiology is covered in Exercise Physiology and Energy Systems.
