Low Aerobic Shortage solved but VO2Max decreasing

To have the most accurate VO2Max estimate you need 2 things:

- an accurate HRMax, weight and age in your user profile. HRMax is very important. Turn the auto-detection off and use 220-age as a starting point. I know this is an average, but it will get you started.

- a balanced training focus. The VO2Max calculation takes your most relevant and best VO2 (aka HR+HRV) and performance (aka pace) pairs, across all range of efforts to give you an estimate. Endurance, tempo, threshold, VO2Max, Sprint, Anaerobic efforts, all feed the model.

Thanks a lot for the articulate answer.

I agree, and indeed I always keep an eye to what the auto HR-max detection does since I know my one is around 185 (measured during an intense run some time ago), so if I see tha auto-detection skewing it more than 2-3 points, I correct it. I've left it on just to see how it behaves, if it consistently suggests it's a bit lower, I might want to re-test it and see if it has indeed lowered.

As for the different efforts that feed the model, that's exactly my doubt: when I was always running at high aerobic and anaerobic range the VO2max kept high. I now know that running that way was wrong, but now that most of the runs are in low aerobic and just one is high aerobic at most (I try to stick in the middle of HR3 indeed) it seems that the model is thinking I just can't do better. So I feel like trapped: either I balance the load focus OR I improve the VO2max, because if I tend to prefer the latter the load focus will go astray and start signalling again I am in low aerobic shortage.

Hi, just go for max effort like max distance over 30 minutes once in a two weeks, that should give the algo enough data to correctly estimate your VO2MAX.

Thanks ApoC for this. So one of the takeaways of this answer is that one has actually to run at Anaerobic level for sometime not too rarely to keep the model updated?

Is there anywhere one could find even a summary description of how the model factors in the various efforts ?

For example, would running 2 lento and a 15' HIgh Aerobic + 15' Anaerobic session every week do the same as doing the 30' Anaerobic every other week as suggested ? I know this also enters the space of how to properly train beyond merely scoring a metric on the watch, but that's also my way of trying to engineer a proper training plan (or pehaps I should say fitness plan, though only made of runs).

I found some time ago an article how the VO2MAX is estimated, could be little bit different now, but the main takeaway was correlation between HR and the pace. So basically running faster produced better VO2MAX values :)

Sorry thats really bad advice , 220-age is a mass quantified metric just like BMI if you take a large selection sample it will be roughly right.... BUT on an individual basis it will be wrong 99% of the time and seriously wrong at that. Given most people will have massively higher VO2max than 220-age it will cause the watch to give massively inflated V02 figure, Whilst this may make you happy for bragging rights it will not reflect your true fitness level. Garmins 'auto' in their latest series watches is considerably more accurate than 220-age for the majority of uses , If your going to switch it off then you should use a proper V02 max test run (google one that you fancy doing) or even better switch to Lactate threshold running. Your second point is valid though and also lead to lower injury risk if followed. 

or running slower with relatively lower HR, it a ratio of pace/HR vs lookup table. that is why you can get VO2 max increases from walking.

Read the article ApoC, interesting. So, in my effort to try to keep as less injury-prone as possible, I might try with a progressive attempt as above: insert a 15' HR3 + 15' HR4 run (maybe increasing the minutes a bit as time goes by) within the 2 lentos in a training week and see if the VO2max starts to get increase again. If not I guess I should try the 30' HR4 as per your suggestion.

There all relative to your fitness/athletic ability vs lookup table. so for me being an Old git I struggle to run consistently anaerobically which effects my ability to hit high V02 figures But conversely my ability to run long/fast regularly give me Higher than average V02 max figures though the watch regularly  complain im unproductive . With the latest fenix 7 I leave it on Auto for HR though tend to run to Lactate threshold . Im 59 My Garmin estimated v02 max varies 52-55 My lab tested V02max is 54. My Fenix 5 using manual HR Max (tested not guessed) varied 49-53 so the Fenix 7 on auto is estimating more accurately that the fenix 5 

Hi Andy W, thanks for your contribution as well. So all-in-all, what's your suggestion to modify my lentos, medium or fast runs in the 3 run-per-week plan to both get increasing my VO2max while at the same time keeping the load focus balanced? Currently the watch auto HR max detection is some points below my once-seen 185, but I've run consistently slower than I used to do in the past severak weeks so I don't know whether that's enough to fool the watch thinking I can't get higher than what it thinks.