GARMIN please tune the VO2max calculation and race predictor

I have a garmin fenix6X Pro Solar for almost a 10 months now (I had a garmin fenix5 en before that a FR935, FR745 and a 920XT).

Since I have the Fenix6 the race predictor and VO2Max are far to low.

On the previous watches I had the VO2max was pretty good (it was similar on a VO2max test in a health clinic), the race progronose was a bit height on those watches.

Here a example off last weekend, I ran a 5K (not on the road but on dirt and it was hot and there was wind), this was my result on sunday (yesterday):

This is the race predictor:

VO2max:

The difference on the 5K between the race predictor (17:57) and what I ran is almost a minute (and on a road race I can also run faster now (I think about at least 20 sec faster).

The last time I tested my VO2max it was 68 (it is a bit lower now I think, around the 65 I think).

Is there a way that the first beat (I think that's used for this data) can be tuned? It is way off at this moment.

Top Replies

subra over 4 years ago +2 verified

Yes, it's obviously a well known issue. But for me the race predictor times aren't to slow, rather they are much to fast.

The algorithmn doesn't use your running times or PB directly. Rather it…

All Replies

0 kompressor over 4 years ago

Mine is very accurate... Strange but true. Did a half marathon on sat and the predition was 1:33'00'' (ish) and because aof the wind and rain finish on 1:35'40''.

+1 subra over 4 years ago

Yes, it's obviously a well known issue. But for me the race predictor times aren't to slow, rather they are much to fast.

The algorithmn doesn't use your running times or PB directly. Rather it uses VO2max for prediction of the race times.

Here is an iteresting article about this

hetgeheimvanhardlopen.nl/.../

0 goosjuh over 4 years ago in reply to subra

Hello Subra, thanks for your answer :-)
There is difference between the fenix6 and older watches, on the fenix6 it is far to slow on the older watches a bit to fast.

I read the article you attached, when I look at table in that article I should have a prediction of 16:47 on a 5K with a VO2max off 61 and not 17:57.

The strange thing is, garmin has made changes to determine VO2max and the predictor times in the Fenix6

0 subra over 4 years ago in reply to goosjuh

goosjuh said:
There is difference between the fenix6 and older watches, on the fenix6 it is far to slow on the older watches a bit to fast.

It's strange that different watches calculate different predicted race times. Then also the Garmin Physio TrueUp function shows wrong values.

By definition VO2max is the maximum oxygen consumption and this can only exactly be measured by a spiro-ergonomic lab test. This analyses the inhaleted and exhaleted O2 at max workout.

Garmin/Firstbeat instead use a submax workout and extrapolates the speed to HRmax, as described in figure 2 of this paper.

https://assets.firstbeat.com/firstbeat/uploads/2017/06/white_paper_VO2max_30.6.2017.pdf

I wouldn't call this VO2max, since there is no measurement of O2. It's simply a rough approximation. For the race time predictions tables from elite athletes are used. But usually also elite athletes that run at the same pace have different VO2max.

From my POV Garmin measures something like Jack Daniels VDOT, which takes also into account the running economy. But VO2max isn't equal VDOT and if you look at table 4 there is a VDOT table from Jack Daniels, which is denoted "Race time prediction based on VO2max", which is clearly wrong.

goosjuh said:
I read the article you attached, when I look at table in that article I should have a prediction of 16:47 on a 5K with a VO2max off 61 and not 17:57.

5k in 16:47 gives a VDOT = 61.1 as you can see here

http://www.fu-mathe-team.de/daniels.yaws?fvals=g2gCZAAEdmRvdEZATf2u6vyg5g%3D%3D&raced=5000&racet=16%3A47&vdotrace=berechnen

Since VDOT is always smaller than VO2max Garmin has something interchanged. This may be reason for the differences.

0 subra over 4 years ago in reply to subra

And using Coopers formula for VO2max

https://en.wikipedia.org/wiki/VO2_max#Cooper_test

5k in 16:47 corresponds to 5000m/1007s*720s=3575m in 12min

VO2max =(distance in 12min - 504.9)/44.73=(3575m-504,9)/44.73=68.6

goosjuh said:
The last time I tested my VO2max it was 68 (it is a bit lower now I think, around the 65 I think).

Note the difference

VDOT = 61.1

VO2max = 68.6