[matsemann]

The absolute doesn't really matter (except for bragging rights), but the trend is definitely useful if it accurately follows your form.

Of course, a vo2max doesn't explain everything as an endurance athlete. As a cyclist it has a big correlation to FTP, but there are also different metrics to be good at. Short sprints, recovery after bursts, plain grit for multi-hour rides etc. are all different skills not shown in a single number.

[starfezzy]

The absolute value does matter for several reasons, but the obvious one that sticks out is in understanding the effectiveness of your training.

Example: if your real max is 60, but your watch says 50, you may be wondering why hard training isn’t increasing it.

Another example: if your real max is 35 but your watch says 45, you may misinterpret the signal when it jumps to 55 relatively quickly after a few weeks of hard-ish work.

Plus, if the value is significantly inaccurate then who knows what else is inaccurate about it? I appreciate that Apple have put effort into making it accurate.

[matsemann]

But my point was more that if it shows 45 (but real is 35), and then you work out a lot and it shows 55 (but real is now around 45), it's still useful even though the values are off. As long as the error/bias is the same.

[iamacyborg]

You’d probably be tracking FTP or lactate threshold (amongst other things) instead of vo2max, right?

[k1kingy]

100%. Every semi-serious cyclists would be running a power meter first and foremost (heck even average joes these days because most modern high-end road bikes come with one already). Far easier to do a 20min/ramp test every so often instead of trying to focus on VO2 max.

[matsemann]

Yup, but as I said, it's nice to not focus on a single number. FTP doesn't tell how well I can recover after a hill at 120% of ftp, so even though I work on increasing my ftp, it's nice to keep in mind other aspects as well. Both vo2max, but also just how I feel when doing it, how my heart rate is during comparative rides, or even how well I'm fueling.

[nsbk]

I just focus on the trend rather than the value. Last year, after being infected by two viruses in parallel my vo2max plummeted from ~55 to 40 in a month. It correlated with how I felt, like 15 years older. It took me six months to get back to 55, and then it stayed around that value quite consistently, viruses or not.

[formerly_proven]

Similar for me, but I've also not really seen my behavior influence it too much. I clearly have better and worse weeks / months, where I might walk at 10min/km and require a 90-95 HR to do that, and worse months where I'll only walk at 11min/km and end up in the 100-110 HR range, but it's not like my exercise levels or weight or nutrition or anything would differ much between the two, they are all very consistent. Likewise when I increase cardio training I don't see any correlated change in VO2max. That also makes sense, as VO2max is famously difficult to train.

I suspect for me and probably many others in the "acceptable fitness level" category the main factor influencing what ends up being reported as VO2max is stress, both physiological and psychological. That correlates real good. At least for me.

[nsbk]

In my experience, vo2max doesn't seem to correlate with stress. I've been stressed out for the last few weeks at $dayjob, and my vo2max has been consistent with more relaxed periods (high). How much of a variation do you perceive during stressful periods?