Cycling VO2 max on 19.20

That's real good to know, thanks for mentioning this!

I don't  think so. Powermeter is always a requirement in order to get VO2 from Cycling. How else should Garmin determine how much effort you put into at a current pace? 

I would be curious to understand the algorithm that can work out VO2max without a power meter. There are too many variables to determine from just speed.

MTB, road bike, TT bike, fully loaded touring bike, solo or drafting in a pack, surface rolling resistance, gradient, wind, in the drops vs hands on top, lycra vs cargo pants and a winter rain jacket, single speed vs optimum gearing etc.etc.

How can Garmin possibly know enough to determine VO2max without a power meter? In the past, when these mysterious numbers have been reported, I'm sure they've been dismissed as a glitch.

for me, it never updated VO2 max for cycling, because i had no power meter.

I ask the same question, how it's possible to estimate VO2max for cycling, where there are so many factors to consider.  Is this a bug?

Maybe it took the VO2Max from running and used it for cycling as well? I never run, but I get running VO2Max based listed in CGM as well.

Believe or not...

my fenix 6 pro calculates VO2max on an irregular basis since April only by (mountain-.) biking.
I don't run or walk since February.
I think Garmin tested this feature on selected profiles.

eezytiger said:

How can Garmin possibly know enough to determine VO2max without a power meter? In the past, when these mysterious numbers have been reported, I'm sure they've been dismissed as a glitch.

I use a PowerCal PowerTap heart rate-based power estimator because it's the only 'power meter' I could get, that works for a footbike. I'm aware that it produces 'just numbers' and not accurate power data, but it is very useful for me to compare (segments of) rides. I suppose Garmin could do a similar thing as the PowerCal does, based on heart rate data. 

It probably is a glitch, who knows… anyway I still remind myself that all VO2 max figures were use for running are just algorithms as the watch/HR strap cannot take our gas exchange readings and we don’t question that, and all the variables you suggest are at play for running too - Garmin managed to create an algorithm for trail running which was considered near impossible due to such variables, and there are bike power meters out there that determine accurate power from a wind speed meter fixed to the handlebars… it’s all just math at the end of the day.. I’m sure someone will nail it soon

With cycling the speed is much faster, which means that drag, and the power required to overcome it, are much more influential than when running. Plus, the equipment performance can vary far more greatly than "running shoes", unless people are recording their runs in Wellington boots.

For example, I tried some simple calculations on this website - http://bikecalculator.com/ - to see how changing the bike and bike position might change power inferred from speed. For the figures I used, 250W on a TT bike into a 16 kph headwind would require 488W on an MTB to match the speed, before you consider the influence of clothing or surface type.

I really don't think Garmin is in a position to make a sensible guess about power from speed when cycling, without a lot more data that is simply not available. With running, unless you choose trail running, track running etc, it is probably safe to assume that you are on a hard surface, wearing "running shoes", light clothing and running upright. Most also won't be running at 30-40 kph for long, especially into a 16 kph headwind.

FWIW I used to use an MTB as a road bike for a very long time, so I would record "cycling" whilst on an MTB. My guesstimated power/VO2max from such a setup would definitely sell me short, more so in my winter clothing. It really just isn't worth doing the maths when they could be so wrong.