VO2 Max Explained
VO2 max is the best single measure of aerobic fitness and one of the strongest predictors of long term health. Here is how to raise it.
Last updated: 1 July 2026
Overview
VO2 max is the maximum rate at which your body can take in and use oxygen during intense exercise, expressed in millilitres of oxygen per kilogram of bodyweight per minute.
It is the standard laboratory measure of aerobic fitness, and it is also one of the strongest single predictors of long term health outcomes, which is why it has moved from sports science into general health conversation.
Quick Answer
VO2 max is the maximum amount of oxygen your body can use per minute during intense exercise, measured in ml/kg/min. It reflects cardiorespiratory fitness and improves through a mix of high intensity intervals and sustained moderate aerobic training.
Key Points
- Measured in ml of oxygen per kg bodyweight per minute.
- Strongly associated with long term health, not just performance.
- Improves through both hard intervals and sustained easy volume.
- Watch estimates track trends better than they measure absolutes.
- Declines with age, but training slows the decline substantially.
Typical values
| Category | Men, ml/kg/min | Women, ml/kg/min |
|---|---|---|
| Poor, 30 to 39 | Under 35 | Under 30 |
| Average, 30 to 39 | 38 to 45 | 33 to 39 |
| Good, 30 to 39 | 46 to 53 | 40 to 46 |
| Excellent, 30 to 39 | 54 plus | 47 plus |
| Elite endurance athletes | 70 to 85 | 60 to 75 |
Values decline roughly 8 to 10 percent per decade in untrained people. In people who keep training, the decline is closer to half that.
Because the measure is per kilogram of bodyweight, losing fat raises VO2 max without any change in cardiovascular function. That is a real improvement in relative capacity, but it is worth knowing what moved.
How to improve it
Two ingredients, both necessary.
| Training type | Contribution | Prescription |
|---|---|---|
| High intensity intervals | Raises the ceiling | 3 to 5 min at near maximum, 4 to 6 reps, equal rest |
| Sustained moderate work | Builds the aerobic base | 30 to 60 min conversational pace |
| Easy volume | Supports both | Walking, easy cycling, daily movement |
The classic VO2 max interval session is four to six repetitions of three to five minutes at an effort you could sustain for roughly eight to twelve minutes, with equal recovery. It is deeply unpleasant and highly effective.
A practical week: one interval session, one to two longer easy sessions, and a general baseline of daily movement.
How accurate are watch estimates
Smartwatches estimate VO2 max from heart rate relative to pace or power. They are reasonable at tracking your own trend over time, and less reliable as absolute numbers.
| Use case | Reliability |
|---|---|
| Tracking your own change over months | Good |
| Comparing to another person | Poor |
| Comparing to lab values | Moderate, often off by several points |
Treat the number as a trend line for yourself, not a score to compare with someone else's watch.
Why it matters for health
Cardiorespiratory fitness is consistently associated with lower all-cause mortality, and the largest single jump in benefit comes from moving out of the lowest fitness category rather than from reaching elite levels.
In other words, the most valuable training in health terms is done by the least fit people, and it does not require intervals to start. Walking regularly moves someone from the bottom category upward.
Common Mistakes
| Mistake | Why it causes problems | Better approach |
|---|---|---|
| Only doing intervals | Neglects the aerobic base | Include easy volume |
| Only doing easy work | Ceiling stops rising | Add one interval session weekly |
| Chasing the watch number weekly | Estimation noise exceeds real change | Review monthly |
| Intervals too short | Does not stress the oxygen system enough | 3 to 5 minute efforts |
| Comparing across devices | Different algorithms entirely | Track your own trend |
Frequently Asked Questions
What is a good VO2 max?
For a 30 to 39 year old, above roughly 45 for men and 40 for women is good. Context of age and sex matters more than the raw number.
How quickly can I improve it?
Untrained people often see meaningful improvement within six to eight weeks. Trained individuals improve much more slowly.
Does lifting weights improve VO2 max?
Only marginally. Resistance training has many benefits, but raising aerobic capacity is not one of its strong points.
Is a smartwatch VO2 max accurate?
As an absolute value, not particularly. As a trend for the same person on the same device, it is reasonably useful.
Sources
American College of Sports Medicine - https://acsm.org/
NHS physical activity guidelines for adults - https://www.nhs.uk/live-well/exercise/exercise-guidelines/
WHO physical activity fact sheet - https://www.who.int/news-room/fact-sheets/detail/physical-activity