VO2Max and Training status not updating despite high load and significant training improvements

Not sure if it's related, but I get sudden drops in my VO2max. Although Garmin Connect only shows whole numbers, I've noticed that on the Epix you can see more granular increases/decreases on the week chart.

Typically, I'll see my VO2max creep upwards, perhaps approx 0.1 or 0.2 a week, but then suddenly one activity will see it drop by a whole digit and it's then back to slowly building it back up again. FWIW, I believe my current VO2max is about 51/52, but I'm struggling to get it any higher than 47 on my Epix right now. I was pushing on 48 (probably about 47.8) until about a week ago when it arbitrarily dropped it back down to 47 (46.6) again after a bike ride. The fact that over about 20 previous activities it had been pretty consistent including some expected increase makes me wonder what it takes to suddenly decide it was wrong and drop me right back down again on the basis of one single activity - I've never noticed massive jumps in the positive direction.

The Garmin support article includes a dead link: 

For additional tips, see the following article on the Garmin Blog: Why Isn’t My VO2 Max Increasing? Tips for Improving Faster.

Your link used has been fixed.

NeilJonesOnline said:

I believe my current VO2max is about 51/52, but I'm struggling to get it any higher than 47

How do you know the 51/52 estimate?

The Firsbeat algorithm is featuring a 5% mean absoluted percentage error (MAPE) difference with VO2Max in a lab. But then again, a VO2Max in a lab has the same MAPE.

The biggest and most common culprit is an innacurate HRMax (or age/weight). Make sure to disable HRMax auto-detection. If you know your HRMax from a very hard anaerobic or VO2Max workout, use that value. Otherwise, use 220-age.

Because the algorithm uses various techniques to scrub off outlying data points, correct for cardiac drift in low intensity, and leverages HRV to assess VO2max in high intensity workouts, it is better to have a balanced training load to populate the model adequately. Otherwise, the watch will have to extrapolate your VO2Max and your corresponding performance at that point using a general population model (age/sex/weight). This can yield to variations: if you do a lot of lower (sub-threshold) workouts, you might see the VO2 Max drift accordingly (higher or lower - higher for me typically). Similarly, if you suddenly go for a race or an intensive workout, the model will adjust (higher or lower - lower for me typically). But these will do small adjustments, the kind you see with performance condition updates.

Bigger VO2Max can occur when the device receives updates from another device with a different/older model, or when the running VO2Max is picked up over the biking one, or you change the way you measure your pace or power and that forces new performance values into the model, but this is rarer (although it happened to me yesterday!).

I am guessing the Epix2 model has changed to smooth out VO2max adjustments more gently than previous devices, from the look of the trends and small adjustments, but I don't know for sure.

Are you doing only bike activities or some running too?

ChMueller001 said:

But in my case the VO2Max is showing up and is calculated. But the calculated value in the beginning was far to high and now it’s decreasing very slowly.

Yes, I saw the same things after my injury. Biking VO2max decreased very slowly from 57, where it hang for 2 months of inactivity, then started decreasing very slowly as I picked up indoor biking slowly. It took 2 months to drop to 51, and a month to go back up to 52. It looks like Garmin has smoothed out changes in VO2Max on the Epix2 to avoid fluctuations due to daily model updates. This is conjecture.

Problem is that in my case the initial calculation was far  too high and so it’s no smoothing but a completely wrong value. There's no point in sugarcoating it.

I'm basing my 51-52 VO2max on correlation and - admittedly - a bit of guesswork. I've taken my lab-tested results from 4 years ago (which at the time correlated well with what Garmin/firstbeat said) and I've reduced by 1 for every year to account for ageing as my fitness load has been pretty steady (and balanced) over that time. That has seemed to be in line with Garmin's estimates up until this summer. I have my HRmax and resting HR set correctly and not to auto-update. I also ensure I use my known HRmax rather than theorised as I'm well outside the 220-age prediction (I'm 53 with an HRmax of 200).

I have been using the Epix alpha/beta firmware, and I have caught that messing with my HR zones (even though they were set as %LTHR and neither that nor my HRmax setting had changed), but if that was enough to drop my estimated VO2max by a whole point (without any smoothing), why doesn't this recover once settings are corrected? It's as if one outlier reading is enough to convince the firstbeat algorithm that all its recent previous estimates, whilst consistent, have been wrong.

It looks like you are on top of things to get a good estimate!

NeilJonesOnline said:

It's as if one outlier reading is enough to convince the firstbeat algorithm that all its recent previous estimates, whilst consistent, have been wrong.

I saw the same thing when I changed bikes and the difference in power meter bumped up my VO2Max "suddenly" by one point in one day. If you combine running and cycling, it is possible that the resulting "general" VO2Max moves around, depending on which activity gives you last the best VO2Max.

nope, but I did a factory reset a couple of weeks ago and my HRV trend is almost ready, so with my training load being consistent and my race predictions still improving I have good hope that training status will soon turn to green ! Let's wait and see ;)

I also have the feeling that the algorithm is set no to account for quick changes.... But I wonder at what level this may cause it not to dismiss good calculations. TBH I have no idea how complex the algorithm is.