VO2 readings: same person and 2 different Apple watches provide very different readings

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Level 1

14 points

VO2 readings: same person and 2 different Apple watches provide very different readings

I wanted to do a test on the Apple Watch VO2 readings, so I started doing my usual walk using one day one of my Apple Watch and another day the other. The readings were profoundly different: 5+ points of difference which left me really puzzled about how seriously I should be taking the reading from the Apple Watch. To further the test I then put the watch on a friend's wrist (same walk, same length and everything) and the readings were exactly the same as if I had been wearing the watch/es. Why was this further disappointing? because I have a chronic lung issue and my friend does not. Are we kind of becoming 'dependent' on something whose accuracy is just BS? How much can we trust this tool?

Ah, like others on this thread, I also had an unjustified drop of my VO2 as I hit my 60th birthday, for no reason, as I train every day precisely to keep my lungs in shape...

Are we all wearing an expensive toy that promises a lot but gives us false readings and hopes?

Anyone else did a similar test?

Posted on Jul 24, 2025 06:04 AM

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Answer 1

Top-ranking reply

Ingo2711

Level 9

77,823 points

Jul 24, 2025 07:16 AM in response to napoleonessa

Which Apple Watches did you use?

If I'm in doubt of the VO2 estimate on my Ultra 2, I take the 1-Mile Test:

VO2Max: 1-Mile Walk – TrainerMetrics

The estimate of the Apple Watch is always 2-3 points lower.

About getting into a new age group in the VO2max calculation, you can guess the date of my 60th birthday by looking at the graph. 🙂

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Answer 2

LuxStar

Level 2

312 points

Jul 24, 2025 06:30 AM in response to napoleonessa

Hi.

Apple Watch VO2 max estimates can vary between devices and even the same device on different days. The watch uses heart rate and motion sensors to calculate it, which isn’t always precise.

It’s normal to see differences of several points and similar readings on different people because it’s not a clinical measurement.

Bottom line it’s an estimate with limits and not a fully reliable medical reading. Hope this helps clear things up!

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Answer 3

napoleonessa Author

Level 1

14 points

Jul 24, 2025 07:17 AM in response to LuxStar

Thanks LuxStar, the difference in many points was not with different people, it was with the same person, myself. This is why I then replicated the test with a different (healthy) person, exactly in the same path (time and length). The readings were exactly like the ones I would get.

Person 1 's readings

Apple Watch 1= X

Apple Watch 2= X+5

Person 2 's readings

Apple Watch 1= X

Apple Watch 2= X+5

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Answer 4

napoleonessa Author

Level 1

14 points

Jul 24, 2025 07:18 AM in response to Ingo2711

I used a 5 and a 2.

Indeed I can see your birthday :-P

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