After updating my Apple Watch and Phone to ios26 Vo2max dropped

[calliex]

After updating my Ultra II Apple Watch and Phone 15 to ios26 Vo2max dropped from 36 to 32.
It has steadily come up from 34 to 36 until today after a 3 mile run ended up at 32hm
I am 75 and have been working all summer to get to go up.
I am assuming a algoritm change.
Any one have other thoughts

 

[doogm]

You should talk to this guy: https://forums.macrumors.com/threads/change-in-vo2-max-since-upgrading-to-watchos-26.2466427/

Mine also continues to go down, from 54.7 before the update to 51.2 today. As it's still pretty high and I'm winding down a training plan for a half-marathon on Sunday, maybe? It could also be that my new watch is capturing more heart-rate data than my old Ultra was? Or, as you say, Apple has improved the computation with watchOS/iOS 26?

 

[calliex]

my VO2maxI have been steadily rising during this summer from 34 to 36.4. Day after the update I went a long 5 mile walk/jog and got the 32 reading. It is still good for my age and stays at 32 for my last couple of runs. Just disappoint.

 

[doogm]

You should talk to this guy: https://forums.macrumors.com/threads/change-in-vo2-max-since-upgrading-to-watchos-26.2466427/

Mine also continues to go down, from 54.7 before the update to 51.2 today. As it's still pretty high and I'm winding down a training plan for a half-marathon on Sunday, maybe? It could also be that my new watch is capturing more heart-rate data than my old Ultra was? Or, as you say, Apple has improved the computation with watchOS/iOS 26?

Down to 50.6 today. It goes down every day. As I said, it was 54.7 on the day I installed the OS 26 updates, just 17 days ago, and 54.5 the day before I got my Ultra 3.

 

[Jackbequickly]

I would say it has to be a change in the algorithm. My phone did a recalibration a week of so and it went up about 2 points. It did go down 4 points with the new phone and S11.

I don't pay much attention to the number, you want to watch the trend.