Polar VO2 Max: The Fitness Test, OwnIndex, and How Accurate It Is
Run these workouts on your iPhone, or hands-free on Apple Watch. Get PEAKVO2 Polar estimates your VO2 max two ways. The Fitness Test produces a value called OwnIndex from a short at-rest measurement, no exercise required: you lie still while it reads your resting heart rate and heart rate variability and combines them with your age, sex, height, weight, and activity level. Running Index estimates your aerobic running performance from the heart-rate-to-pace relationship during runs. OwnIndex agrees with lab VO2 max around 80 to 85 percent of the time, so trust the trend over the exact number, and remember Polar tracks your fitness, it does not train it.
Polar has been estimating cardiovascular fitness longer than almost anyone, and it does it differently from every other brand: it can give you a VO2 max estimate while you lie on the couch. Here is how both of Polar's fitness numbers work, how far to trust them, how they compare to other devices, and what actually moves them. For what your score means at your age, see our VO2 max charts by age and sex.
Does Polar Measure VO2 Max?
Polar estimates it rather than measuring it directly. A true VO2 max reading needs a mask and a metabolic cart in a lab. What Polar does is model your maximal oxygen uptake from heart rate data, and uniquely among the major brands, its main estimate does not require a workout at all. That estimate is called OwnIndex, and it comes from the Polar Fitness Test.
Polar's Two VO2 Max Numbers
It helps to know that Polar gives you two related but separate numbers.
- OwnIndex, from the Fitness Test: an at-rest estimate of your VO2 max, taken lying down, no running needed.
- Running Index, from your runs: an estimate of your maximal aerobic running performance, which reflects both aerobic fitness and running economy.
They answer slightly different questions. OwnIndex is the closest thing Polar has to a lab VO2 max figure; Running Index tells you how that fitness translates into running.
How the Polar Fitness Test (OwnIndex) Works
The Fitness Test is the unusual one. You lie down, stay relaxed and still for about five minutes, and the device reads your resting heart rate and, crucially, your heart rate variability, the small beat-to-beat variations that reflect how well your cardiovascular and autonomic systems are working. It combines that signal with the profile data you entered, your age, sex, height, weight, and self-reported long-term activity level, and produces OwnIndex, a number comparable to VO2 max.
Two practical points:
- No exercise required. This is the whole appeal. A fitter heart shows a lower resting rate and richer variability, so Polar can estimate aerobic capacity at rest.
- A chest strap helps. The test depends on a clean beat-to-beat signal, which a Polar chest strap like the H10 captures better than a wrist optical sensor. Some watches such as the Vantage V2 offer a wrist-based version, but the strap is more reliable.
OwnIndex runs on a scale from roughly 25 for an unfit adult to about 95 for elite endurance athletes, the same territory as measured VO2 max.
What Is Running Index?
Running Index is calculated automatically during a run, with no separate test. Polar compares your heart rate to your speed, because the two are linearly related: run faster and your muscles demand more oxygen, so your heart rate climbs. From that relationship it estimates your maximal aerobic running performance. It needs a run of at least 12 minutes at a speed above 6 km/h to compute. A rising Running Index means you are running a given pace at a lower heart rate, or a faster pace at the same effort, which is exactly what improving fitness feels like.
How Accurate Is Polar's VO2 Max?
Treat both as good estimates, not lab numbers. Research on the resting-measurement approach behind the Fitness Test has found it predicts maximal aerobic capacity with roughly 80 to 85 percent accuracy against laboratory treadmill testing, which is solid for a test you can do without moving. A few things affect the reading:
- Signal quality. A clean heart rate variability reading matters most, which is why a chest strap beats wrist optical for the Fitness Test.
- Honest inputs. OwnIndex uses your self-reported activity level and profile, so an inaccurate entry shifts the result.
- State on the day. Because it reads your resting autonomic state, poor sleep, stress, caffeine, or illness can nudge a single Fitness Test result.
As with every wearable estimate, the trend is the signal. Take the Fitness Test under similar conditions, for example first thing in the morning, and watch the direction it moves over weeks rather than reading too much into one measurement.
Polar vs Garmin, Apple Watch, and Coros
Each brand estimates VO2 max its own way, which is why the numbers rarely match across devices.
| Device | How it estimates VO2 max | Needs | Best for |
|---|---|---|---|
| Polar | At-rest Fitness Test (OwnIndex) from resting HR and HRV, plus run-based Running Index | A 5-minute lying-down test, ideally with a chest strap | People who want a VO2 max estimate without a workout |
| Garmin | Firstbeat analytics, from runs and power-based rides | Outdoor runs or cycling with power | Multisport athletes training by data |
| Apple Watch | Automatic from outdoor walks and runs (Cardio Fitness) | Outdoor GPS workouts | Passive tracking with no test |
| Coros | EvoLab, from heart rate and pace on outdoor runs | A 25-minute outdoor run, one every 90 days | Runners who want a stable estimate |
For a fuller breakdown, see our best fitness trackers for VO2 max comparison.
How to Raise the VO2 Max Polar Shows You
Here is the key point: Polar shows you the number, it does not train it. Watching OwnIndex sit flat is frustrating without a plan to move it. VO2 max rises with high-intensity interval training, and the biggest gains come from time spent near your maximum heart rate (Helgerud et al., 2007). The reliable way to move it:
- Do two to three interval sessions a week. The Norwegian 4x4, four intervals of 4 minutes at 90 to 95 percent of max heart rate, is the most studied protocol.
- Build an easy aerobic base on the other days so the hard sessions are productive.
- Retest under the same conditions so the OwnIndex trend reflects fitness, not the state of the day, and expect a measurable change after 6 to 8 weeks.
Polar tracks the trend; a training app runs the sessions that create it. PEAKVO2 guides the Norwegian 4x4, 30/30, and other VO2 max protocols on iPhone and Apple Watch with heart rate zones and automatic phases, then you watch your Polar number climb. Follow the full 8-week VO2 max training plan to structure it.
Raise the number Polar shows you
PEAKVO2 runs the interval protocols that actually raise VO2 max, the Norwegian 4x4, Tabata, and 30/30, on iPhone and Apple Watch, with heart rate zones, spoken cues, and automatic phases. Three workouts free.
Get PEAKVO2 freeFrequently Asked Questions
Does Polar show VO2 max?
Yes. Polar estimates VO2 max as OwnIndex through its Fitness Test, an at-rest measurement that needs no exercise, and separately estimates your aerobic running performance as Running Index during runs. Both appear in the Polar Flow app and on compatible watches.
How does the Polar Fitness Test work?
You lie down and stay still and relaxed for about five minutes while the device reads your resting heart rate and heart rate variability. It combines that with your age, sex, height, weight, and self-reported activity level to produce OwnIndex, a number comparable to VO2 max. A chest strap gives a cleaner reading than wrist optical.
What is the difference between OwnIndex and Running Index?
OwnIndex comes from the at-rest Fitness Test and is Polar's closest equivalent to a lab VO2 max. Running Index is calculated during a run from the relationship between your heart rate and speed, and estimates your maximal aerobic running performance, which reflects both fitness and running economy.
How accurate is Polar's VO2 max?
The resting-measurement approach behind the Fitness Test predicts maximal aerobic capacity with roughly 80 to 85 percent accuracy against lab treadmill testing, which is strong for a no-exercise test. Use a chest strap, test under consistent conditions, and read the trend over weeks rather than a single result.
Do I need a chest strap for the Polar Fitness Test?
Not always, but it helps. The test relies on a clean beat-to-beat heart rate signal to read heart rate variability, and a Polar chest strap such as the H10 captures that more reliably than a wrist optical sensor. Some watches like the Vantage V2 support a wrist-based Fitness Test, but the strap is more accurate.
Can I improve the VO2 max Polar shows me?
Yes. VO2 max is highly trainable. Two to three high-intensity interval sessions a week, such as the Norwegian 4x4, typically raise it by 5 to 15 percent in 8 to 12 weeks. Retake the Fitness Test under the same conditions and the OwnIndex trend should climb.
Keep Reading
- Best Fitness Trackers for VO2 Max, Compared
- Garmin VO2 Max: How to Improve Your Estimate
- Coros VO2 Max: How EvoLab Estimates It and How Accurate It Is
- VO2 Max Training Plan: The Science of an 8-Week Program
- VO2 Max by Age: Chart of Normative Scores and What's Good
References
- Polar. The Polar Fitness Test and OwnIndex. Polar Support. support.polar.com
- Polar. The what and how of Running Index. Polar Support. support.polar.com
- Helgerud J, Høydal K, Wang E, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007;39(4):665-671. PubMed
- Mandsager K, Harb S, Cremer P, et al. Association of cardiorespiratory fitness with long-term mortality. JAMA Netw Open. 2018;1(6):e183605. PubMed