The first time I run with my watch, it told me my VO2 Max is 61 (which is pretty high but I'm also very young (17) and fit), but every time I completed a run, my VO2 max started decreasing.
I thought this was normal because it needed a few weeks to really calculate my VO2 max accurately so after a few weeks, it should give me a stable number but that didn't happen. It kept dropping to 58 and lower.
I bought a chest heart rate strap to get more accurate results, but it kept dropping.
It just completely drives me nuts that my watch says my VO2 max keeps decreasing after every single run since I bought the watch even though I can run faster than a few months ago while having a lower heart rate which proves I'm improving.
My VO2 max has only improved once and straight after that, it decreased again...
This is my VO2 max in Garmin Connect:
Here's my VO2 max trend line but down to the 0,01 (instead of the single-digit number Garmin Connect shows (I use a tool which can extract the VO2 max estimate from the .fit files which has your VO2 max estimate value down to 0,01)):
The weird thing is that I see a lot of people on the internet who are having the same issue and they're all using the Forerunner 245.
When I look at the VO2 max trend others are having (like with their Fenix 5, Vivoactive,...), I see their VO2 max sometimes increases with 3-4 (!) in just 4 weeks which means they really get an accurate result. My VO2 max keeps dropping with about 0,2-0,4 every single run so about every 20 days, my VO2 max drops with 1 in Garmin Connect.
I would really like to get an answer from Former Member or HermanB.
I've already contacted Firstbeat about this issue/problem but they can't explain why this is happening.
EDIT: maybe also something interesting to note: my VO2 max indication on the web version of Garmin Connect is just empty even though my watch measured my VO2 max yesterday and the mobile app does show my VO2 max.
When I click on it to see more info about my VO2 max, it shows me the number but doesn't have the visual indication it normally has (which shows you how "good" your VO2 max is):
EDIT 2: Here's my VO2 max trend from Runalyze which seems to be a lot more accurate since it's improving. I think my Garmin VO2 max will decrease until it's at the same of my Runalyze VO2 max and then it will be accurate:
Here are some more people on Reddit who are having the same issue:
