How Polar Calculates Your VO2 Max (OwnIndex and Running Index)
Polar has two systems: a five-minute resting test that needs no exercise, and Running Index from every run. One of them is much more trustworthy.
Polar is the only major brand with two separate VO2 max systems, and they work in completely different ways. One asks you to lie down for five minutes. The other watches you run. Knowing which number you are looking at matters, because they are not equally trustworthy.
OwnIndex: a VO2 max estimate with no exercise
The Polar Fitness Test produces OwnIndex, a figure directly comparable to VO2 max, while you rest.
It combines your resting heart rate, heart rate variability, age, sex, height, weight and self-reported activity level. There is no exercise in it at all. The physiological reasoning is sound in outline: resting heart rate and HRV both track cardiovascular fitness, and the anthropometrics and activity level fill in the rest.
The appeal is obvious. No test, no suffering, a number in five minutes, and it works for people too unfit or too unwell to do a maximal test.
The catch is the accuracy. Non-exercise prediction models of this type land somewhere around 80 to 85% accuracy against laboratory treadmill testing in the general population, and they degrade at the edges. One study of masters basketball players found the OwnIndex test substantially overestimated VO2 max, with a mean error near 30% and poor agreement.
The self-reported activity level is part of why. You are grading your own homework, and the model takes your answer seriously.
Running Index: an estimate from every run
Running Index is not a test. It appears automatically after every run.
Polar takes your heart rate and speed during the run, together with your resting and maximum heart rates, estimates the maximal running speed you could hold on level ground, and converts that speed into a running VO2 max.
This is the same family of model as Garmin's Firstbeat engine, and it has the same strengths and the same weakness. It is based on what you actually did rather than what you said about yourself, which makes it the better of Polar's two numbers. But it rests on your maximum heart rate, and Polar still estimates that with 220 − age unless you have replaced it.
Geschatte VO2max
42.4ml/kg/min
uit de 12-minuten-Cooper-test
Ongeveer waar dat ligt
| Inactief, ongeveer 30 tot 40 | 30 tot 40 ml/kg/min |
| Recreatief actief, ongeveer 40 tot 50Aanbevolen | 40 tot 50 ml/kg/min |
| Goed getraind, ongeveer 50 tot 60 | 50 tot 60 ml/kg/min |
| Duuratleet, 60+ | 60+ ml/kg/min |
- Dit is een veldschatting. Een goed verdeelde loop op een vlak parcours komt binnen een paar punten van een labtest, maar tempo, terrein en weer verschuiven het getal allemaal.
- Een echte VO2max vereist een laboratoriumtest met gasanalyse. Submaximale opties zijn de Uth-Sorensen-hartslagmethode (VO2max is ongeveer 15,3 keer HRmax gedeeld door HRrest) en de Rockport-wandeltest over één mijl.
- Conditiecategorieën variëren met leeftijd en geslacht. Behandel de band als richtlijn, niet als harde grens, en vergelijk met je eigen eerdere tests in de tijd.
Een PDF met je resultaten, plus een QR-code om ze altijd opnieuw te openen.
Estimate yours from a race result and compare it against both Polar numbers. If OwnIndex is much higher than the other two, that is the expected direction of its error.
Which one to use
Use Running Index for tracking training. It moves with real efforts, it is grounded in performance data, and comparing it across similar runs gives you a usable trend.
Treat OwnIndex as a starting point. It is genuinely useful when someone cannot do a maximal test, and genuinely unreliable as a performance number for a trained athlete.
Fix your max heart rate first. Both systems use it. An estimate built on a formula guess inherits that guess.
FAQ
What is Polar OwnIndex? A VO2 max estimate from the Polar Fitness Test, calculated at rest from your resting heart rate, heart rate variability, age, sex, height, weight and self-reported activity level.
What is Polar Running Index? An automatic running VO2 max estimate produced after every run from your heart rate and speed, plus your resting and maximum heart rates.
Is Polar OwnIndex accurate? Non-exercise models of this kind run around 80 to 85% accuracy in general populations, and one study of masters athletes found it substantially overestimated VO2 max. Use it as an indicator, not a performance measure.
Why is my OwnIndex higher than my Running Index? Overestimation is the documented direction of OwnIndex's error, and the self-reported activity input pushes it the same way.
Which Polar number should I track? Running Index. It is based on what you actually ran rather than what you reported about yourself.
Other brands
- Garmin uses Firstbeat and short credible segments.
- Apple Watch has published independent validation.
- COROS uses a rolling six-week window.
- Fitbit also estimates from resting heart rate when you do not run with GPS.
Sources
- Polar on VO2max
- Polar on Running Index
- Polar Smart Coaching: Running Index
- How Polar calculates your max heart rate
Cover photo by Tristan Haskins, CC BY-SA 3.0, via Wikimedia Commons.
