| What it is | Max oxygen your body can use |
| Units | ml/kg/min |
| Represents | Aerobic 'engine size' |
| Improved by | Intervals (+ base & threshold work) |
VO2 max is the maximum rate at which your body can take in and use oxygen during intense exercise, measured in milliliters of oxygen per kilogram of body weight per minute. It represents your aerobic ‘engine size’ and is a key marker of endurance fitness. Influenced by genetics, it’s also improved through training — especially high-intensity intervals — alongside threshold and base work.
The aerobic engine
Built most directly by intervals; works with lactate threshold and a zone 2 base to drive endurance.
Frequently asked questions
What is VO2 max?
VO2 max is the maximum amount of oxygen your body can take in and use during all-out exercise, expressed relative to body weight (ml/kg/min). It reflects the capacity of your heart, lungs, blood, and muscles to deliver and use oxygen — essentially the size of your aerobic engine — and is a major component of endurance fitness.
How do you improve VO2 max?
High-intensity interval training near maximal aerobic effort is the most direct stimulus, but improvements also come from a strong aerobic base (easy and long runs), threshold work, and consistency over time. Beginners typically see larger gains; trained athletes improve more slowly, since genetics also sets a ceiling on VO2 max.
Is VO2 max the only thing that matters?
No — while it's an important marker of aerobic potential, endurance performance also depends heavily on lactate threshold (the fraction of VO2 max you can sustain) and running economy (how efficiently you use oxygen). Two runners with similar VO2 max can perform very differently based on threshold and economy, so training all three matters.
Sources
- VO2 max — American Council on Exercise
- Aerobic capacity — American Trail Running Association