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Vo2Max and other metrics going down

Nico
10 months ago

I'm very confused about my watch's recent behaviour. Let me describe a series of events in order:

1) I started an ultra-marathon training. At that point my watch indicates I have a Vo2Max of 47. I use the optical sensor of the watch to track my HR. 

2) A month into the training I buy a polar chest strap to monitor my heart. My Vo2Max drops to 46 by that time, when I should be stronger already.  

3) Shortly after, I decided to go for a lab Vo2Max test. The test reveals my Vo2Max is actually 58.4 and I'm blown away at the disparity but Training status and other metrics remain reasonable. 

4) After the Vo2Max test and running every session with the Polar HRM, I keep getting noticeably stronger every week but my watch keeps downgrading: Unproductive Training status and a Vo2 Max now sitting at a meager 42 ,when I suspect I should be above 60.  

So, aside from the massive initial disparity before using the Polar HRM,  Vo2Max 47 (watch) vs  58.4 (lab test), it is like everything regarding the metrics went downhill the moment I started wearing the Polar. 

Is Garmin actually "punishing" me for using another HRM brand?  This is rendering most of the watch's metric useless to me. I'm extremely disappointed with the brand if they do this. If only they designed a proper chest HRM with a detachable piece from the actual strap I would've stayed within the ecosystem, but that design is absolutely stupid. 

Any thoughts? 

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  • 0 10 months ago

    I am using both an HRM pro plus and a Polar H10. I see no impact of using one versus the other on the metrics or on the built-in tests.

    So, IMO, no reason to be suspicious of the Polar support.

    WRT to your VO2 max, there is something going on.

    A couple of possible explanations:

    - first and foremost, your reference HR data is off. Check your Max HR on the watch. Also, make sure your rest HR is correct (wearing the watch 24/24 is the best way to get a current average Rest HR. Check also your age and weight.

    - there is a bias in your training data. As you train for an ultra, long easy runs may be dominating your training data. The absence a high aerobic and maximal effort intervals may introduce a bias that makes it harder for the watch to predict your ventilation/HR/HRV/pace relationship in the higher ranges.

    - less likely, there is a bias in your pace data. This shouldn’t be an issue with GPS, but could be with tread-mill running, and/or using a pod that is not well calibrated,

    - during the first few mn of your runs, there are issues with the quality of your strap HR data. You would see a poor performance condition and that will take your VO2 Max estimates down.

  • 0 10 months ago in reply to Etupes25

    Thanks a lot for your detailed explanation. I think you hit the spot with the second point, which I did suspect. My training is indeed focused on mostly long easy runs, complemented by short high-intensity stretches. Ratio probably at the usual 80-20.  Before starting the program, I was running but I was all over the place, without structure and at way higher intensity overall.

    I did set all the Heart Zones manually adjusted to the results of my Vo2Max test and also my maximum heart rate at 196 but like I said, all metrics kept going down consistently. Also, I'm 46 and my test results put me in the 1% percentile. I'm not saying this to brag but maybe the algorithm finds it harder to reach a more accurate outcome.

    Should I deduct from this that the watch isn't able to track data properly when following this kind of training? 

    Thank you again :) 

  • 0 10 months ago in reply to Nico
    Nico said:
    Should I deduct from this that the watch isn't able to track data properly when following this kind of training?

    Not quite yet. The VO2 Max model has an excellent average standard error of 5% or less if your HR Max is right.

    https://assets.firstbeat.com/firstbeat/uploads/2017/06/white_paper_VO2max_30.6.2017.pdf

    That said, 5% is the average error. Some people could see a much larger error, maybe as high as 20% on an older Fenix 5

    http://www.muscleoxygentraining.com/2019/05/firstbeat-vo2-estimation-valid-or-voodoo.html

    So, it is possible, but unlikely, that you are very unlucky with an error of 19.5% on your VO2 Max.

    Nico said:
    My training is indeed focused on mostly long easy runs,

    The accuracy increases as HR data closer to HR Max is available See curve # 3 below

    Microsoft Word - VO2_white_paper_Revised_B.doc (firstbeat.com)

     So, it is possible and likely that the combination of having used the wrist HR and a focus on slower runs in the past have biased the data.

    To address the potential bias, I recommend the following steps that I followed mysefl after having observed dubious VO2 Max changes:

    - perform a backup of the watch,

    - reset the watch to factory settings, but do not connect it to the phone or to Garmin Express,

    - using a wet chest strap on a cool day when you are in prime shape, go for a easy to moderate run. Run for at least 10-20mn. You will get a new VO2 max estimate. In theory, this is your minimal VO2 max.

    - if you still get a much lower VO2 max, then the reset didn't help you as it did me. Then you can restore your watch using the backup and skip the next step

    - if you get a better estimate, run for a couple of weeks across a range of efforts at steady maximal pace for the following interval to test the various energy systems (I took inspiration from the WKO5 software individualized zones table here):

    * sprints: all out for 15s, rest 2mn, repeat 8 times

    * anaerobic capacity: max steady pace for 40s, rest 2mn, repeat 8 times

    * max aerobic: max steady pave for 3mn, rest 3mn, repeat 6 times

    * threshold: max steady pace for 12mn, rest 3mn, repeat 3 times

    - avoid hills, as they will skew your metrics, while you reinitialize the data.

    After a couple of weeks, if you stress too much about not being connected, you don't want to reset all the settings or you cannot live without your HRV baseline, you can connect the watch. Reconnecting shouldn't pertubate your newly establish VO2 Max data (it didn't in my case).

  • 0 10 months ago in reply to Etupes25

    Wow, thank you sooo much for spending the time in such detailed response. I will wait until my official 13 weeks program is finished and if all data is still off I will follow all this procedure. This was fantastic. Thank you!