That's interesting.
In that same 5 week period I have done five weeks of progressive running mixing easy and harder sessions, working at keeping hr low on three out of four, steadily extending my longer session and doing an intervals session. At first Garmin was happy and promoted me one VO2 max in week 2 and then another in week 3. All seemed to match how I was training though I was cautious of praise thrown at me by the ToJ. And then for no apparent reason I am demoted a VO2 max point, relegated to serial couch potato (unproductive) and generally chided and scolded for making the effort. The thing is, I don't feel how it tells me I feel: I feel fitter, stronger, more powerful and more capable. During my latest intervals session I could sustain my tempo finish for longer and my 100m "sprints" are improving. It may only be an average of a second or so but I am improving.
And yet Garmin ...
Now, I am not in the top 5% or even 30% for my age but I knew that when I started my mission to get fit again. I am not even sure how that metric is derived because looking at the unfit hoardes in the town centre when I go shopping I must surely be in the top 10%. I can only assume that Garmin believes that the human population consists mainly of elite athletes and a few chronically ill people. 🤔
Anyway, I am genuinely pleased with my progress (and it is real progress) so Garmin can go shove it's algorithms up it's oximeter!