If you wear an Apple Watch, Garmin or Polar, your device has probably shown you a VO2 max score. It estimates how much oxygen your body can use per minute of hard exercise.
On its own the number means nothing. Set against the standard reference tables for your age and sex, it becomes one of the strongest predictors of long-term health science has produced.
The reference values most clinicians reach for come from the American College of Sports Medicine's Guidelines for Exercise Testing and Prescription, now in its 11th edition. The percentile bands are built on data from The Cooper Institute's Aerobics Center Longitudinal Study, which has tracked cardiorespiratory fitness in more than 80,000 US adults.
The reference range by age and sex
VO2 max is reported in milliliters of oxygen per kilogram of body weight per minute (ml/kg/min). Higher is better.
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The ACSM cutoffs place a man aged 20 to 29 in the excellent tier above 52 ml/kg/min. For a woman of the same age the threshold is 41.
Age | Men: average | Men: good Also read: This is what happens to your body if you eat late every night | Men: excellent | Women: average | Women: good | Women: excellent Also read: AI taking notes at your doctor's appointment may be getting your medications wrong |
|---|---|---|---|---|---|---|
20-29 | 37-41 | 46-52 | >52 Also read: Saven everyday foods that may be quietly ruining your sleep | 29-32 | 37-41 | >41 |
30-39 Also read: A robot can now draw your blood, and clinical data shows it may be better than a human | 35-39 | 44-50 | >50 | 27-30 | 35-39 | >39 |
40-49 | 33-36 | 41-47 | >47 | 25-28 | 33-37 | >37 |
50-59 | 29-33 | 38-44 | >44 | 22-25 | 30-34 | >34 |
60-69 | 26-30 | 35-41 | >41 | 19-22 | 27-31 | >31 |
70+ | 23-27 | 32-38 | >38 | 17-20 | 25-29 | >29 |
The tables slope downward with age for a reason. In the general population, VO2 max falls by roughly 10 percent per decade after 30.
That is why a score in the low 30s can be excellent for a 70-year-old woman and merely average for a woman of 40.
Why the number tracks with survival
Cardiorespiratory fitness is not just a training metric. An updated meta-analysis of 37 cohort studies with 2,258,029 participants, published in Mayo Clinic Proceedings in 2022, found that people in the top third of fitness had a 45 percent lower risk of dying from any cause than those in the bottom third.
For every one MET gain in fitness, roughly the difference between a slow walk and a brisk one, all-cause mortality risk fell by about 11 percent.
The link runs the other way too. A cohort of 6,836 middle-aged adults without prior heart disease found that each one MET drop in peak fitness raised the risk of a major cardiovascular event by 18 percent, and the risk of dying from any cause by 29 percent, over a median seven-year follow-up.
These figures line up with earlier work suggesting that cardiorespiratory fitness predicts survival more strongly than cholesterol or blood pressure.
None of this proves that raising your VO2 max saves your life. But the association is graded, holds across age and sex, and appears independent of the usual risk factors.
How wearables get it wrong
The score on your wrist is an estimate, not a measurement. Consumer watches do not have gas analyzers. They infer VO2 max from your heart rate response during walks and runs.
A validation study of Apple Watch Series 9 and Ultra 2, published in PLOS ONE in 2025, tested 30 adults against gold-standard indirect calorimetry. The watch underestimated VO2 max by a mean of 6.07 ml/kg/min.
The limits of agreement stretched from minus 6 to plus 18 ml/kg/min. The authors concluded the reading is fine for tracking your own trend over months, but not accurate enough for a clinical decision.
The two ways to raise it
Two training styles have been most studied for improving VO2 max. High-intensity interval training uses short hard efforts with recovery in between. Moderate-intensity continuous work, often called zone 2 training, is the pace at which you can still hold a sentence.
A randomized trial of 44 healthy men comparing the two approaches recorded within-group VO2 max gains of 3.5 ml/kg/min in the HIIT arm and 1.9 ml/kg/min in the continuous group. The difference between groups was not statistically significant, and moderate continuous training produced a larger drop in systolic blood pressure.
For most adults, the American Heart Association still recommends at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous activity per week. Anyone starting a new program with a chronic condition or a family history of heart disease should talk to their doctor first.
This article is made and published by Jesper Bengtson, who may have used AI in the preparation.