Garmin Connect has a Vo2 reading in performance stats. Not going to be scientifically accurate but it can provide a pattern or trend.
Mine is currently showing 56, which coincidentally is my age
.
It peaked a few weeks ago at 58 after a decent spell of H.I .T intervals, 2,4 and 8 mins .
Been back at work about a month and that's when the trend started falling,
Not sure I want to keep up with the intervals intensity plus working now
High end feels fairly well tuned but legs feel endurance is lacking and fatigue has been feeling high.
It's all a bit of a balancing game isn't it ?
I think I'll try and get some longer steadier rides and cut intensity for a bit .