The number is meaningless without a reference group
VO2 max is the maximum rate at which the body can take up and use oxygen during intense exercise, expressed in millilitres of oxygen per kilogram of body weight per minute. A value of 40 ml/kg/min is unremarkable for a man of 25 and unusual for a man of 75, so every published classification bands results by age and sex before saying anything about them.
That is the first thing to check on any chart you are handed: which population it was built from, and how the labels were assigned. Two charts built from different cohorts, or from the same cohort cut a different way, will disagree about the same number — and both can be correctly labelled.
How ACSM's percentile classification works
ACSM's Guidelines for Exercise Testing and Prescription (12th edition, 2024) classify cardiorespiratory fitness by percentile within each age and sex group, using the updated reference standards from the FRIEND Registry — directly measured treadmill cardiopulmonary exercise tests, published by Kaminsky and colleagues in 2022.
Each listed percentile is the lower bound of its class. The scheme is the same for everyone; only the millilitre values behind it change with age and sex.
| Percentile | Class | Share of the reference population |
|---|---|---|
| 95th and above | Superior | Top 5% |
| 90th to 94th | Excellent | Next 5% |
| 80th to 89th | Good | Next 10% |
| 60th to 79th | Fair | Next 20% |
| 40th to 59th | Poor | Next 20% |
| Below the 40th | Very poor | Bottom 40% |
Why the median lands in Poor
Read the table again and the consequence is plain: the 50th percentile — the exact middle of the reference population — sits inside the Poor class. That surprises people, and it is worth being precise about what it does and does not say.
The label describes a position in a distribution, not a diagnosis. It says that half the reference group scored higher, and nothing more. The FRIEND reference population is made up of people who completed a maximal laboratory exercise test, which is not a random sample of the general public, so the distribution sits higher than a population average would.
This is also why comparing labels across charts is the single most common mistake. An older category table built from the Cooper Institute's 1997 manual places its bands one to two classes higher. A man of 25 measuring 48 ml/kg/min reads as good on that scale and as Poor on ACSM's — the number has not moved, only the ruler.
Worked example: the same value on two rulers
Take a man of 30 who estimates 43.9 ml/kg/min from a Rockport walk test. On ACSM's percentile classification for men aged 30 to 39, the 40th percentile is 37.0 and the 60th is 43.4, so 43.9 clears the 60th and lands in Fair.
On the older six-category Cooper table the same result reads as above average, and on the older five-category simplification it reads as good. Three labels, one measurement. Whenever a result is quoted with a word rather than a number, the word is only interpretable alongside the scale that produced it.
| Scale | Label for 43.9 ml/kg/min, man aged 30 |
|---|---|
| ACSM percentile classification (12th ed., FRIEND) | Fair |
| Cooper Institute six-category norms | Above average |
| Older five-category simplification | Good |
What the classification is useful for
Cardiorespiratory fitness is worth measuring. A 2016 American Heart Association scientific statement argued that it should be assessed routinely in clinical practice, on the grounds that it predicts outcomes independently of more familiar risk factors.
For that purpose, the practical value of a percentile is comparison over time against the same ruler. A field-test estimate carries meaningful measurement error, so a single reading places you in a broad band rather than at a precise point; the same test repeated under the same conditions some months later is far more informative than one reading compared against a chart from a different source.
- Record the test, not just the number — Cooper run, Rockport walk and laboratory tests are not interchangeable.
- Record which scale produced the label, and re-read old results against that same scale.
- Treat a class boundary as a soft edge: field estimates can move a few ml/kg/min between attempts.
- Compare yourself with your own previous result before comparing with anyone else's.
Frequently asked questions
Why is my VO2 max called poor when it is average?
Because ACSM's classes are percentiles of a reference population, and the Poor class spans the 40th to 59th percentile — which is where the median of that population falls. The label describes where a value sits in a distribution, not a clinical judgement. Older category charts assign kinder-sounding words to the same numbers, which is why the two disagree.
What is a good VO2 max for my age?
On ACSM's percentile classification the Good class begins at the 80th percentile for your age and sex. For a man in his twenties that is 54.5 ml/kg/min; for a woman of the same age it is 44.8. The thresholds fall steadily with age — for a man in his seventies, Good begins at 25.9 ml/kg/min.
Why do different VO2 max charts give different answers?
They come from different reference populations and assign category names differently. The Cooper Institute category norms and ACSM's percentile classification are both published and both legitimate, but they sit one to two classes apart for the same value. Always read a label against the scale that produced it rather than carrying a word from one chart to another.
Does a percentile class tell me whether I am healthy?
No. It places a measurement within a distribution of other people's measurements of the same age and sex. Cardiorespiratory fitness is associated with health outcomes at a population level, but a percentile is not a diagnosis and a field-test estimate is not a clinical measurement. Questions about your own health belong with a clinician.
How much can a field test estimate be out by?
Enough to move you across a class boundary. Field tests infer VO2 max from distance, time or heart rate rather than measuring oxygen uptake directly, and conditions such as wind, heat, terrain and pacing all shift the result. That is why a single reading is best treated as placing you in a broad band, and why repeat testing under matched conditions is more informative than one number.
References
- American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription, 12th edition. Wolters Kluwer, 2024 — cardiorespiratory-fitness classification built on the FRIEND Registry reference standards.
- Kaminsky LA, Arena R, Myers J, et al. Updated reference standards for cardiorespiratory fitness measured with cardiopulmonary exercise testing: data from the Fitness Registry and the Importance of Exercise National Database (FRIEND). Mayo Clinic Proceedings 2022; 97(2): 285–293.
- Ross R, Blair SN, Arena R, et al. Importance of assessing cardiorespiratory fitness in clinical practice: a case for fitness as a clinical vital sign. Circulation 2016; 134(24): e653–e699.
- Cooper KH. A means of assessing maximal oxygen intake: correlation between field and treadmill testing. JAMA 1968; 203(3): 201–204.
- The Cooper Institute. Physical Fitness Specialist Certification Manual, revised 1997, Dallas, TX — the source of the older category norms discussed above.