VO2Max seems... stuck?

it's very unlikely that I'm suddenly getting the exact same VO2Max after every activity.

Why do you think so? This is actually what is supposed to happen. Initially the watch learns, and the VO2max fluctuates. But after some time the estimate should stabilize, only changing when your fitness improves or decreases, and this does not happen rapidly. That's the theory. It's possible of course, that there's something wrong. Just to reassure you, my VO2max changed frequently for the first couple of weeks, but then stabilized at 54, and most of the time stays there, only occasionally droppping to 53.

I agree with the above, I presume from the post the score is updating on each run and so would be the correct estimate. Mine only decreases if I lay off training or get sick, it also decreases in hot weather sometimes.

As was said above, it's completely normal for your Vo2Max score to stay at a consistent level when your activity level is consistent.

Mine is normally around 50-51, will go up to 52-53 when I peak during a training cycle for a goal race, and then drop back down as I lose fitness when my activity level goes down after the event.

The VO2 number getting fixed over time makes some sense, however depending on the conditions on my activity I expect at least mild fluctuations. For example a few days ago I jogged in extremely hot/humid weather and I was miserable and slower than usual, and my heart was pumping faster. Yet at the end I received the same VO2Max value.

This is what the above posters are saying. It will take a little time and the watch will learn your VO2 Max. It won't, and shouldn't, change based on that 1 extreme weather run you had. If you had several consecutive runs in that type of weather, then the watch would recognize it as a change in your training and you'd see a change in your VO2 Max. Think of it like your RHR. If you average 46-47 over a couple of weeks but have one night where you tossed and turned and it was 55, your watch will still see you at a 46-47 average and not change it based on that 1 night.

Fair points - Thanks everyone for your replies

I wish I knew how to get my VO2 Max to do anything. I do 5 to 6 hour plus combo walking and running sessions per week and my VO2 never changes. I've run the self test, but it fails 6 to 7 min in to it. I've had to VA3 for a little over 2 months. Any suggestions would be greatly appreciated!

I talked to support about my VO2 reading because the self test was on running for about 6 min. They told me once you’ve run a test a few times it only takes a few min to get a proper reading because your watch has already built up a history of your VO2 max

Once the watch develops a solid Vo2Max score for your current fitness it won't change either up or down unless/until you change your routine to either increase or lose fitness. If you've been doing pretty much the same routine, either walking or running, at the same paces for awhile before getting your first device your score will go up and down for a week or two before settling in at a number to represent your current fitness. After that it will only go up if your fitness improves by adding either more volume or more intensity to your routine. Likewise it will go down if you're sick, injured, or life gets in the way long enough for your fitness to regress.

The caveat to that is that sometimes weather can affect the result because hotter or colder temps than usual can raise or lower your HR relative to pace. Like last week it was a cooler day than has been normal recently and I did a fast mile at a club track meet and my number went up to 52 from 51. This week we had a heat wave and my HR was 8-10bpm higher than normal for my easy pace runs and it dropped right back down to 51 although my fitness surely didn't change in 5 days.

I would say that this is a fairly constant value, the changes of which can be seen in months spent in other conditions or changes in the workload of training ... If you want to find out how this works, you can read it from the authors of the algorithm on the site https://www.firstbeat.com/en/consumer-feature/vo2max-fitness-level/