Apple Watch VO2max calculation

Walking,running or hiking heart rate;

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.

This forum is full of posts with the same issue as you,including me,it appears to be an algorithm problem judging by the amount of people on here reporting a drop in their Vo2max figure.