In the first US reference data built from direct treadmill testing, the typical 20-something man's aerobic fitness measured about 48 milliliters of oxygen per kilogram of body weight per minute — and the typical 70-something man's measured about 24, roughly half as much. Women showed the same pattern at lower absolute numbers: about 37.6 in their 20s, 18.3 in their 70s. Averaged across that 50-year span, aerobic fitness fell by about 10% per decade.
| Age group | Median VO2 max, men | Median VO2 max, women |
|---|---|---|
| 20 to 29 | 48.0 mL/kg/min | 37.6 mL/kg/min |
| 70 to 79 | 24.4 mL/kg/min | 18.3 mL/kg/min |
| Change across that span | About half | About half |
| Average rate of decline | Roughly 10% per decade | Roughly 10% per decade |
What is VO2 max, exactly?
VO2 max is the maximum rate at which your body can take in, transport and use oxygen during intense exercise, measured in milliliters of oxygen per kilogram of body weight per minute. It's the standard lab measure of cardiorespiratory fitness — how well your heart, lungs, blood and muscles work together to fuel sustained effort — and it's measured directly by having someone exercise to exhaustion on a treadmill or bike while breathing through a mask connected to gas-analysis equipment.
That direct measurement is the detail that makes the 2015 reference data notable. Researchers led by Leonard Kaminsky pooled 7,783 maximal treadmill tests — each one confirmed to have pushed the person to a true physiological limit — from eight US exercise-testing laboratories, contributed by men and women ages 20 to 79 who didn't have cardiovascular disease.¹ Earlier US fitness standards had mostly estimated VO2 max from how fast or how long someone walked or ran, a reasonable shortcut but not the same as measuring gas exchange directly. This was the first large US dataset to report measured values at this scale.
How much does VO2 max really decline with age?
By a lot, and fairly steadily. The 50th-percentile adult in the study's youngest group (ages 20 to 29) measured 48.0 mL/kg/min if male and 37.6 if female. By the oldest group (ages 70 to 79), those medians had fallen to 24.4 and 18.3 — each roughly half the starting value. Averaged across the five decades in between, the researchers reported the decline at approximately 10% per decade, a pace that held whether people were in their 30s or their 60s rather than accelerating sharply at any single age.
The men-versus-women gap is consistent too: at every age the study measured, the median woman's VO2 max ran noticeably below the median man's — a difference largely explained by differences in body composition and the amount of oxygen-carrying hemoglobin in the blood, not a difference in how hard either group was trying.
Is a lower VO2 max at 60 just normal, or a problem?
Both, in a sense — it's the expected pattern, and it's also the thing worth paying attention to. A decline across decades is what this reference data shows in the typical person, so a lower number at 60 than at 30 isn't itself a red flag. What the study doesn't tell you is where any one person falls relative to others their own age, or what that means for your individual health risk — it's a snapshot of what's typical, not a verdict on what's healthy for you specifically. Where you land within your age-and-sex group, and whether that's worth discussing with a clinician, is a different question than the one this dataset answers.
Can you actually find out your own VO2 max?
Only approximately, outside a lab. The measurement in this study required maximal exercise testing with gas-analysis equipment — the kind of setup found in exercise physiology labs, some cardiology clinics and sports performance centers, not in a typical gym or living room. Consumer wearables that display a "VO2 max" estimate are calculating it from your heart rate, pace and other data during ordinary workouts, not measuring your actual oxygen uptake at a true maximal effort — a useful trend to track over time, but a different thing from the number in this dataset.
What the research says
Kaminsky and colleagues pooled 7,783 maximal treadmill cardiopulmonary exercise tests from eight US laboratories, collected over just over a year, in men and women ages 20 to 79 without known cardiovascular disease, and reported the first US reference percentiles for VO2 max built from directly measured gas exchange rather than estimated from treadmill workload.¹ The 50th-percentile VO2 max fell from 48.0 mL/kg/min in men and 37.6 in women ages 20 to 29, to 24.4 and 18.3 respectively by ages 70 to 79 — a decline the authors characterized as roughly 10% per decade across that span.
Two limits apply. This is a reference dataset, not an outcomes study: it describes what's typical at each age and sex, and it doesn't, by itself, show what a given VO2 max predicts about any individual's future health (that's a separate body of research, covered in does being fit matter more than being thin?). And the people in it all passed a maximal exercise test at a clinical testing laboratory — a group that may differ in activity level or health status from the broader population, which is part of why the authors describe this as reference data for interpreting a measured test, not a population-representative survey.
What you can do this week
- If you've ever had a VO2 max measured in a lab or clinic, ask how it compares to your age-and-sex group — this dataset is built for exactly that kind of interpretation, which a wearable's estimate alone can't give you.
- Treat a wearable's VO2 max estimate as a trend line, not a lab result. Whether it's rising or falling over months matters more than the exact number on any given day.
- If fitness itself — not just VO2 max specifically — is the goal, regular aerobic activity is the lever that moves it, and the research on fitness and long-term health risk is a separate, well-studied question from the reference data above.
A VO2 max number on its own doesn't diagnose anything. What this reference data offers is context: a sense of where a measured value sits relative to thousands of others at the same age, which is the information a fitness or clinical measurement usually needs to actually mean something.
