Glossary
VO2max estimate
Your watch guessing your aerobic ceiling from pace and heart rate. Wearable estimates typically land within about 5 ml/kg/min of a lab measurement.
What it is
An estimate of how much oxygen you can use per kilogram per minute at full effort. A lab measures it with a mask. A watch infers it from how fast you run at a given heart rate.
A higher number means you go faster at the same heart rate. That is the whole signal.
| Runner | Typical estimate |
|---|---|
| new runner, 40s | 30-38 ml/kg/min |
| regular club runner | 45-55 ml/kg/min |
| 3-hour marathoner | 55-62 ml/kg/min |
| elite | 70-85 ml/kg/min |
What it is not
It is not a lab result. Passler and colleagues found wrist devices land within roughly 5 ml/kg/min of a proper test, which is enough to be wrong about your category.
It is also not a ranking of you as a runner. Two people with the same figure can race minutes apart, because running economy and endurance differ.
What moves it
- Training, slowly. Real change takes months.
- Heat. A hot run raises heart rate, so the estimate drops.
- Hills and wind. Both make you look slower at the same effort.
- A wrong maximum heart rate. Everything downstream inherits it.
When to ignore it
Ignore a fall after a hot week or an illness. The estimate is measuring conditions, not fitness.
Ignore it entirely in the first month with a new watch. It has not seen enough of you yet.
Sources
- Cooper KH. A means of assessing maximal oxygen intake. JAMA 203(3):201-204, 1968 primary
- Uth N et al. Estimation of VO2max from the ratio between HRmax and HRrest. Eur J Appl Physiol 91(1):111-115, 2004 primary
- Passler S et al. Validity of wrist-worn activity trackers for estimating VO2max. Int J Environ Res Public Health 16(17):3037, 2019 primary