Apple Watch, readiness & HRV
VO2max on Apple Watch: where to find it, and how to raise it
VO2max is the most oxygen your body can use per minute, per kilogram of body weight. It is one of the best single markers of endurance fitness, and your Apple Watch estimates it for you under the name Cardio Fitness. Here is where to find it, when the watch records it, how far to trust it and which training actually moves it.
Short answer
Open the Health app, tap Browse (or Search on newer iOS versions), then Heart, then Cardio Fitness. Apple Watch Series 3 or later estimates it during outdoor walks, runs and hikes with GPS and heart rate, and shows values from 14 to 65 mL/kg/min with a level for your age and sex. Read it as a trend over months: a steady rise means your aerobic fitness is improving.
Where to find Cardio Fitness on iPhone
- Open the Health app.
- Tap Browse, or Search on newer iOS versions, and choose Heart.
- Tap Cardio Fitness. Choose W, M, 6M or Y for the trend.
- Tap Show All Cardio Fitness Levels to see how your value compares with others of your age and sex.
The levels (Low, Below Average, Above Average, High) are given for ages 20 and up. You can turn on a notification for a low level in the same screen.
When Apple Watch records VO2max
The watch needs an outdoor walk, run or hike recorded with the Workout app, on reasonably flat ground, with GPS and a steady heart rate. It relates your speed to your heart rate, so you don’t have to run all out. Without such workouts the value goes stale: someone who only cycles or swims may see few or no updates.
- Record outdoor runs or brisk walks of 20 minutes or more now and then.
- Keep your age, sex, height and weight current in the Health app. Weight matters, because VO2max is per kilogram.
- If you take medication that limits your heart rate, such as beta blockers, mark it in the Health details so the estimate accounts for it.
How accurate is it?
A lab test measures the oxygen you breathe while you run to exhaustion. A watch can only estimate it from speed and heart rate. Independent studies generally find that Apple Watch estimates sit close to lab results on average, with an individual error of a few points, often underestimating very fit people. For a single person, that means the absolute number may be off, while the direction of the trend is reliable as long as conditions are similar.
Hills, heat, wind, trail running and a poorly fitting band make single estimates noisier. Look at the trend over months, not at one workout.
Typical values
| Group | Rough VO2max (mL/kg/min) |
|---|---|
| Inactive adults | 25–35 |
| Recreationally active | 35–45 |
| Trained amateur runners and cyclists | 45–60 |
| Elite endurance athletes | 70 and above |
Rough guide only. Values fall with age and are generally lower in women than in men; the Health app shows the level for your own age and sex.
How to raise it
VO2max responds to consistent aerobic training plus a small dose of hard work:
- Volume first. Most improvement in untrained and moderately trained people comes from regular easy training, several times a week, for months. See Zone 2 training.
- Intervals once a week. Repeats of 3–5 minutes at a hard but controlled effort, with equal recovery, are a classic VO2max session.
- Lose a little weight, if you have it to lose. Because the value is per kilogram, the number rises even at the same aerobic capacity.
- Be patient. Changes of a few points take weeks to months.
A long-term VO2max trend with Keho
Keho reads the Cardio Fitness values from Apple Health and shows them as a long-term trend, next to your training volume and load, so you can see which months of training moved it. The VO2max trend is part of Keho’s Advanced Statistics, a one-time unlock that also comes with any other Keho purchase. Keho Coach uses your fitness to set your paces when there is no recent race to go by. Want a second opinion from a race result? Try the free VO2max calculator.
Questions
Why did my VO2max drop suddenly?
Often it is conditions: a hot day, a hilly route, a loose band or a run with many stops. A single low value means little. A drop that lasts weeks, after time off or illness, is real and usually comes back with training.
Does cycling count?
Not for Apple’s estimate, which comes from outdoor walks, runs and hikes. Cycling still raises your fitness; it just won’t update the number until your next qualifying walk or run.
Is a low Cardio Fitness level a health problem?
Low aerobic fitness is linked with higher health risks, and the Health app can warn you about it. If your level is low, or you are unsure whether training is safe for you, talk to a doctor before you start.