A number of users have noticed that Vo2Max values on the Forerunner 255 and 955 fluctuate less than on other Garmin watches. Is this a bug or a new way of calculating the metric?
Vo2Max – what is it?
We’ve done a detailed article explaining Vo2Max. Put simply, this is a measurement of how well your body uses oxygen when you’re working out. It reflects your aerobic physical fitness. As your fitness level improves, your Vo2Max score should increase.
Most watches with built-in GPS have the ability to track Vo2Max. Some devices without satellite connectivity also estimate this metric, although with less reliability. For example, Garmin watches manufactured after April 2017 have the ability to spit out a Vo2Max score – just from all-day heart rate data.
More generally, Garmin needs you to record an activity via the Run Activity profile in order to spit out a Vo2Max score. This must be outdoors with GPS tracking and heart rate monitoring (either from the watch or a chest strap) enabled. The last requirement is that your heart rate must be elevated to at least 70% of your maximum heart rate for at least 10 minutes during the run.
In addition to estimating your Vo2Max from running, Garmin watches can also use walking, cycling, multi-sport and trail running for the metric. It all depends on which Garmin device you own. The company does not publish details on the algorithm used to arrive at the value. So we have to trust them with their calculations.
Garmin Forerunner 255 & 955 – a revised Vo2Max algorithm?
Your VO2 max score is dynamic, and it reacts to how you live and train. At least that’s the idea.
I’ve upgraded from the Forerunner 935 to the 955 a couple of months ago. And as happy as I am with the new device on my wrist, I’ve noticed that Vo2Max values hardly ever change. This is even though I’ve put a fair degree of effort into some of my runs, having set personal bests.
This is unlike my experience with the Forerunner 935. An excellent run might boost my Vo2Max by a point. Follow that with a very poor run a few days later and I might lose a point. This doesn’t occur on the 955.
In fact, I’ve noticed that Vo2Max on my new watch hardly ever changes. Watching this flatline is a bit annoying. At the outset I figured that the device needs more time to adjust and learn about my fitness. But this doesn’t seem to be the case.
Both on Garmin forums and Reddit, Forerunner 255 and 955 owners have reported a simliar experience. The Vo2Max status hardly ever changes! There’s definitely something going on.
And yes, everyone knows not to put too much stock into these types of calculations. They are not nearly as reliable as lab testing. But it would be nice to get a reward for efforts!
It is possible that this might be a bug. Some speculate that it is an issue that only appears for those that have upgraded to one of the new Forerunner watches from an older Garmin watch.
It is also likely that Garmin may have changed the way it calculates Vo2Max. After all, the 255 and 955 have newer firmware as compared to other watches. Perhaps Vo2Max is now a weighed average of activity performance over the past few weeks. That way one excellent or poor run will not effect the score very much.
It would make sense. When you think about, having your Vo2Max jump around is not very realistic. It should be months, not days or weeks, of training to increase your Vo2Max.
We will be keeping a close eye on future updates to the Fenix 7 line, Epix 2 and other Garmin watches on possible amendments to the way they calculate Vo2Max. That will provide the ultimate answer whether the company has changed its Vo2Max calculations.
Increase the number of decimal points in Vo2Max
If you are also annoyed by a flatline in your Vo2Max, there is something that you can do about it. Instead of watching a static score for months on end, increase the number of decimal points in the calculation.
This is most easily done by using the popular, free, online runners platform called Runalize. It can be set up to sync with your Garmin account.
Essential reading: Garmin Forerunner 955 vs 255 – what’s the difference?
By default, the platform uses its own calculations to estimate Vo2Max. But you can change this to display values from the Garmin Fit file.
It is done by clicking on configuration>dataset. Then untick Effective Vo2Max and tick the Vo2Max (by file) box.
From that point on the Vo2Max displayed next to each of your runs will be the Garmin estimate. And unlike the rounded value in Garmin Connect, it will have two decimal points.
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