VO2 max still broken, how to reset?

Well a full reset of the watch doesn't seem to reset these metrics. I guess it's pulling old data from Garmin Connect. Anyone know a way to do this?

I disagree, from the screenshot you sent, the FIT vo2 max seems to be going up and down. If it was broken, or "Stuck" as you say, I would expect that the same value be displayed every run from the FIT file but it isnt. You seem to keep doing better and then do worse. 60 is a very good score. Eventually we all hit a physical limitation, not that you have, this may be a training issue, this could be you running at different tims of the day, w and w/o caffeine, different surfaces, running on a full stomach, different paths taken (hilly vs flat) different temperatures, running with a sore muscle. etc.

If you want to increase based on the watch, you need to have similar variables from run to run. For instance I run every morning, fasted, before coffee. If it is very cold I put on some clothes as the extreme cold can increase your HR and decrease your VO2 score. I would say a track could give you the best surface as well. I do not track VO2 if I am hurt or am very sore and I do not trust the Trail VO2 max calculation as it would have increased my VO2 more than what I think is reality.

Seriously, it's broken. Look at this chart and how the variance and trends changed after I switched to the 955. It also bears no absolute relation to my fitness. At end of last year I was as fit as or more so than March to May...

It's not due the switch to 955.

I had Fenix 6 in the period march 2021-november 2022 and in july 2022 happened the same thing to my V02MAX.

So, it's something in the algorithm by Garmin in ALL watches

That's interesting, so maybe a coincidence.

Looking at my data pre- and post- July 2022, I'm going to guess at to what has happened. It looks like they introduced a bug whereby the estimated VO2max for an individual activity became a rolling average of the previous 2 weeks (or so) of activities, instead of just the headline watch reported value being an average of the previous 2-3 weeks of activities. By incorrectly applying the averaging process at the individual activity level, the VO2max then becomes stuck - as your watch average becomes a double rolling average, so basically stays the same.....that's my guess anyway.

Hi :) I’m no sports scientist, so please correct me if I’m off: but seeing massive differences in VO2 Max _per run_ doesn’t make sense from a physiological perspective, no? Your body’s ability to utilise oxygen doesn’t change from day to day, I would argue. So all awhile I can appreciate the bummer of having it stagnate, the less volatile VO2 Max makes sense, to me at least. 

My ditto has been declining for some time, which I would think is correct: I’ve been injured for a long time, and have only been running on a regular since December. Which then only have been slow runs (Z2). It’s not been until January, I started introducing some threshold runs, too. And now it looks like it’s gradually increasing again.

I do remember “back then” with 935 and 945, when I could increase three points from a very good run; but again, physiologically I don’t think that’s how it works? So rather, perhaps now it’s more likely to be “true”?

My girlfriend has the 255M, and she doesn’t know what a slow run is, thus she always gives it her all (and gets injured…. ) Her VO2 Max is increasing fine - albeit still steadily and not as volatile as before.

(Okay, getting to the buttom of this where I wanted to insert a photo of my graph from the watch, I can’t seem to find that option. But what I would have shown was my VO2 Max for the last four weeks slowly falling from 55 (started even before the last four weeks) to base 54 and is now on an upward trajectory again. There’s a graph in “Training Status” under VO2 Max.)

vinterben said:

but seeing massive differences in VO2 Max _per run_ doesn’t make sense from a physiological perspective, no? Your body’s ability to utilise oxygen doesn’t change from day to day, I would argue. So all awhile I can appreciate the bummer of having it stagnate, the less volatile VO2 Max makes sense, to me at least. 

Some would argue it's not really VO2 Max that's being estimated, but VDOT, the equivalent performance metric.

I've seen a few scenarios where my estimated VO2 Max / VDOT has varied wildly from the previous activity (one or two days ago):

- Sleep deprivation / illness / Injury (because I run slower for the same HR)

- Race (because we usually tend to run faster during races due to adrenaline from the crowd and other competitors)

Especially in the latter case, I often see a big difference in the runalyze VO2 Max and a much smaller (yet noticeable) difference in the Garmin VO2 Max (which again suggests to me that the latter is an average).

Estimated VO2 Max can also be affected by temperature, absolute elevation, elevation change (during a run), and terrain, although IIRC, newer watches do correct for elevation changes.

I think for some people, the VO2max metric is working OK. Not sure why for others (a minority perhaps?) this issue still persists. Garmin thought they had fixed it on a recent update, but it doesn't seem that way for my particular watch / account.

If anyone from Garmin sees my plot above, they will know that it is a bug - no sensible averaging is occurring there. If they had the raw data from my activities and applied the FirstBeat statistical model again, it shouldn't generate those numbers. I've had easily measurable differences in fitness since July (e.g. pace vs heart rate), and it's not reflecting those at all. Also means my predicted 5k time was pretty far off, whereas it had always been pretty decently estimate prior to July 2022.

Now I agree there is a judgment call to be made about "how" to average a series of activities and their associated VO2max to give a summary / headline VO2max which is helpful to the end user and gives them confidence in using the metric to trend their fitness. Previous to July 2022, this worked pretty well in my opinion. I think it was averaging around 7-10 days of activities and correlated nicely to my perceived fitness and time-trials.

Your point about whether a VO2max should change on a per run basis. Well, imagine you did a VO2max lab test every day, would you get the same number? Lots of reasons that could vary day to day too even if it's nominally closer to the action. Now the watch estimate will (I expect) simply be a linear statistical model with a bunch of predictors in it, those give rise to an estimate with a certain amount of precision. Measure that over 10-14 days, average it and you probably get an OK estimate really.

Because I am now obsessed, I plotted the Runalyze vs Garmin estimates for the last year. Although offset by a few units in absolute terms, they trend pretty well together (21 day moving average). Again, highlights where it all went wrong for my watch / account.