VO2max dropped since change from 735XT to Fenix 5

My guess is that the algorithm has been tweaked in the F5 and 935 to make it more accurate. I've had the 935 since just after release and it's still low compared to my 735, but the race predictors are closer to reality (though still optimistic!). Time will tell

CW

I haven't seen any differences in the VO2Max values/Race predictions ?

There aren't any differences in the correlation, it's just the 935 is showing a lower VO2Max for me than the 735

CW

On my Forerunner 235, if you run steep elevation, the watch thinks you lost fitness because all it registered was slow pace and high heart rate.

FYI only: I'm not sure if this is right in case of f5 but on the f3 the vo2max calculation was left out if you use "trail run" instead of "run". Then the vo2max is more accurate because the calculation takes only your "flat" runs into account....

Using a footpod for pace has also given me more accurate VO2max readings in the past. I've gotten ridiculously high readings in the past with just GPS.

Also not sure if the wrist OHR will be as accurate as the chest strap which uses (I believe) HR variability to better estimate how hard you're working.

Apart from Licensing issues with FirstBeat probably physiologic data considered "sensitive personal information" and with all that GDPR mumbo jumbo Garmin may have opt to avoid storing some info in the cloud. And in my opinion they should do do so since they never know when they are going to get Hacked. Imagine gigabytes of sensitive data to leak some day....

And in my opinion they should do do so since they never know when they are going to get Hacked. Imagine gigabytes of sensitive data to leak some day....

Of course there's a possibility of Firstbeat's data being hacked through Garmin’s web based system, but what do you consider sensitive data and what purpose would it provide anyone? Even shady insurance companies couldn't use the data against you because the data isn't official and doesn't provide any medical information on your health.