VO2 max

It is under Heart>Cardio Fitness

There is nothing shown on the watch for that.

You can see it in the health app on your iPhone

To accurately measure your VO2 max, you must wear a face mask. This is the only way to know for sure how much oxygen is going in and out of your lungs.

Since Apple Watch is worn on your wrist, not your face, this is out of the question. So instead, Apple Watch provides a “predicted VO2 max” metric. This is an estimate based on changes in your heart rate during exercise.

Are VO2 max predictions accurate?

The relationship between heart rate and VO2 max is not precise, and it varies from one individual to another. So Apple’s predicted VO2 max may not be very accurate. The estimate is also dependent upon your Apple Watch’s heart rate sensor. And while that’s pretty good, it is not infallible.

Why is there no VO2 max data in the Health app?

If you can’t find any VO2 max readings in the Health app, that is probably because you have not yet logged the right kind of workouts with your watch. Only three workout types can produce an estimated VO2 max on Apple Watch: Outdoor Walk,Outdoor Run and hiking.

VO2 max relates to maximal exertion. So you’ll need to log a pretty intensive workout to generate a reading. And you’ll need to sustain it for at least 20 minutes.

The data source gets added automatically once the watch has some recorded data that it can enter into the health app.