VO2 Max and FTP comparisons

Perusing the manual http://static.garmin.com/pumac/Forerunner935_OM_EN.pdf
then the VO2 Max and FTP tables are interesting.

On Zwift you are in the top category over 4 W/kg. Here that is only good enough for Excellent and Superior starts at 5.05 W/kg which I view as very "Superior"! Not many Zwift racers can manage that...

On the other hand for VO2 Max "Excellent" is only 51.1 and even Superior is still a relatively modest 55.4

My last FTP test put me a shade over 4 W/kg (293W, 71 kg) and yet my VO2 Max on the 935 for cycling is 59 and running is 60. VO2 Max values from the Firstbeat algorithms tend to be a little flattering but I am certainly well over 55 on race predictions for sure.

So perhaps a bit of a conflict here between these two tables? Either that or I need to be pushing out a good 50 more watts!!!

Very interesting question. I also wonder exactly how Garmin/FB assign those "labels".

According to the 935 manual, the VO2max assignment is based on percentiles of the population:
Superior 95 percentile
Excellent 80 percentile
Good 60 percentile
Fair 40 percentile
Poor 0-40 percentile

But when it comes to FTP, the same manual doesn't list any percentiles.

According to the same 935 manual, my age group's Superior 95 percentile is VO2max 52.5 (and above) but my V02max is 64 which is hugely inaccurate as my Marathon PB is only 2:58. And yes all my MaxHR, RHR, weight and age are set correctly on the watch and yes VO2max is just a prediction for a perfect race blah blah blah. But I wish the Garmin/FB could tell me *exactly* why the watch *thinks* I have VO2max of 64 when I clearly don't :-(

One thing I have done with my max HR is to keep it as low as possible by putting it a value I have achieved recently rather than say what have got to in the last few years. Once did that my VO2 Max came down from an also somewhat unrealistic 64 (using 165 max HR) or so to 59/60 (using 160) which is perhaps still a bit flattering but more like it. When I hit 162 the other day, I did then update to 162.

VO2 Max tests tend to be more like 3K/5K type efforts so I usually pay more attention to the 5K prediction and increasingly less as move up distance. I have found very few people are statistically "best" at the marathon anyway even if training for one. Only people I know who are runners like Steve Way who also does ultras to a very high level (well he is the British 100K record holder!)

And back to my original question - the FTP tables are absolute but logically a 50 year old duffer like me should have a lower FTP than say a 25 year old at the same quartile of ability.

Maybe the "problem" is that the two data tables appear to come from different sources.

Anyway hands up if you have a FTP over 5 W/kg. You probably were on the Garmin pro team!

I just thought I would add another factor which may only serve to confuse things further :-)
When estimating V02 max first beat takes into account heart rate variability HRV as well (I think, could be wrong). When your heart is under more stress your heart rate variability decreases. It's a year or two ago since I read about it but when you breathe in your heart rate speeds up slightly and as you breathe out again the heart rate decreases a little bit. That is what is used to create a HRV value.
So if you are running at a certain speed, and your heart rate is pretty constant too, firstbeat looks at your heart rate but also your HRV value, to try to establish how much exertion you are putting in to achieve the speed you are running at.
Now, finally, getting to the point I am thinking about ... optical measurement is not very good at measuring HRV I believe. So I wonder if a more accurate estimate of VO2 max will be achieved when using a chest strap?

Not sure on that point Steve as I nearly always wear a HR strap!
That said when I have used OCR with previous watches, the VO2 Max values that came out were what I expected.

Actually, now that I wrote that previous post, I'm not 100% sure that first beat really does use HRV values!
I will have to check it out... or maybe one of you already know.
In any case, it's interesting. Here is an interesting article about HRV:
http://www.myithlete.com/what-is-hrv/

Firstbeat white paper on VO2 estimation - https://assets.firstbeat.com/firstbeat/uploads/2015/10/white_paper_vo2_estimation.pdf

Firstbeat white paper on VO2 estimation - https://assets.firstbeat.com/firstbeat/uploads/2015/10/white_paper_vo2_estimation.pdf

No HRV there :-) But seems like an accurate max HR for sure plays a big role in getting good values out.

The changes in R-R interval = heart rate variability (HRV)

One thing I have done with my max HR is to keep it as low as possible by putting it a value I have achieved recently rather than say what have got to in the last few years. Once did that my VO2 Max came down from an also somewhat unrealistic 64 (using 165 max HR) or so to 59/60 (using 160) which is perhaps still a bit flattering but more like it. When I hit 162 the other day, I did then update to 162.

VO2 Max tests tend to be more like 3K/5K type efforts so I usually pay more attention to the 5K prediction and increasingly less as move up distance. I have found very few people are statistically "best" at the marathon anyway even if training for one. Only people I know who are runners like Steve Way who also does ultras to a very high level (well he is the British 100K record holder!)

Thanks TIMGROSE. I have read in various posts that indeed MaxHR affects the VO2max scores a lot but although I am 40 (about to turn 41) my HRM-Run gave me MaxHR of 189bpm only 3 months ago (during a hard interval session) and I tend to hit 185-187 pretty regularly (almost once a week on hard intervals). My RHR can go down to mid-30s although Garmin reports it to low 40s.

So should I artificially reduce my MaxHR further, is my HRM-Run broken or is the algo to blame? As a bit of a background, I have been a lifelong athlete starting with swimming at the age of 5 switching to cycling around college/grad school and finally long distance running today.