My apologies if I'm rambling in this post - I'm trying to make sense of the P.C. vs VO2max and the effect of trail runs vs flat runs on these metrics. I don't really have a specific main question here. Any comments to any of my statements/questions, or corrections of misconceptions, are welcome and hopefully some useful experiences could emerge.
I think I've understood the basics of the P.C. - it's a real-time assessment of my performance compared to my VO2max.
- As it's a real-time assessment, it would be normal that the PC is higher at the beginning of a run than it is at the end when fatigue starts to show. (This development is always true for me at least)
- I usually get my PC score after about 1 km of running. After about a year of running with this metric I've never once scored more than +4 or less than -4. I guess that could be an indication that the VO2max estimated by the FR945 is quite close to my real VO2max - or is it just an indication that the watch algorithms for PC and VO2max are aligned?
- Until the most recent FW update, my PC and VO2max scores have been based on Running activities only - which are mostly low intensity asphalt runs with the occasional hill. My current VO2max is 52 and my 1km PC score on these flat runs is almost always in the range from 0 to +3.
- However, I do most of my exercising using the Trail run activity, on trails with mostly uphill running. I've only done one such run after the FW update that enables Trail VO2max (a 7x2min zone 5) and my PC score was -1. It remains to see if the scores continue to be negative, and if so, I expect my VO2max to be adjusted down; in that case the PC should adjust as well giving me less negative scores on trail runs and very positive scores on flat runs?
I also use Runalyze to calculate effective VO2max for my runs. Runalyze always gives lower scores than Firstbeat/Garmin, but the trend is the same: Lower scores (32-38) on hilly trail runs and higher scores (42-46) on flat runs.
This huge difference in the scores from Runalyze vs Garmin makes me wonder which numbers are most correct. (Runalyze 6mo average is around 40 and Garmin estimate is 52) I do realise the VO2max is not an accurate measurement, more like an indication of my fitness in different types of exercises. But I had expected them to be more aligned than this. Anyone with similar experiences?
Looking at Garmin only and the difference in PC scores on flat vs uphill/trail runs, I also wonder how well Garmin's VO2max estimation represents my fitness. Just to give some rough numbers, on flat runs, I can stay within zone 2 for an hour of running at avg 6:00 min/km, while in my typical uphill/trail run I'll be in zone 3 from just a few minutes in, at avg 7:00 min/km. I guess it's hard to say without a laboratory test.