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is there HRM-PRO-PLUS bug/beta forum? significant v8.90 problem: low heartrate with high HRV doubles reported HR because sampling window is too short

rinserepeat
8 months ago

I've been going crazy since I've gotten the HRM-Pro-Plus this year trying to understand a problem and today I think I figured out some significant insight why.

There is a serious problem with its sampling window to determine realtime HR

For weeks I could not understand why the feature on the Fenix to download HR and HRV after an activity would produce significantly different loads and HR zone distribution.

I thought then the Fenix firmware itself was buggy. But you know what, it turns out that because the Fenix recalculates the HR from the HRV data, it is much more sensitive and uses a much larger sampling window to determine the post-realtime downloaded HR and is far more accurate than the realtime HR !!!

(if you are curious you can read my bug report on the Fenix here but don't be distracted, I understand the problem far more clearly now 

What made me realize what is going on is that I've been freaking out some mornings now after I put on the HRM-Pro-Plus before a run and double-check on the Fenix and it will report very high heartrate, like for example today was 93

(93 idle HR made me panic because it's typically a sign you are about to be sick, covid, etc.)

When I used to have a HRM-TRI this sometimes would be from low battery or bad contact on the pads.

But even after cleaning/wetting the HRM-PRO pads and changing the battery (far easier now) it would still report 93.

Then it dawned on me to force the wrist optical monitor ON and force the HRM-PRO off.

Suddenly the Fenix reported the correct, proper resting idle HR of 46.

Switched back to the HRM-Pro and back to 93 HR

I also have a six-lead Kardia Mobile EKG device so I then took a sample with that because it is extremely accurate and not optical.

Sure enough it detected 46 HR

But with the Kardia I was also able to see the graph and how spread out and variable the pulses were.

And then I realized: the optical on the Fenix must use a long sampling window so it averages the wide HR far better!

But the HRM-Pro must be using a small sample window and incorrect assuming when it sees two pulses too far together that for a a minute average that much be twice the rate.

So Garmin developers I humbly suggest to please solve this via one of the following:

1. either make the sampling window larger 

2. or make a dynamic window that learns or figures from a pre-set low resting heartrate for the user (ie. 50) to use a larger window than the default

3. or give the user an option to force a larger sampling window as some kind of advanced feature (I mean it is the flagship HRM so it should have options?)

I happily give Garmin permission to download any of my activities on Garmin Connect to help debug this problem, anything in 2024 should be with the HRM-Pro-Plus

I almost always download the HRV data after the activity on the Fenix. Actually that might be a problem since it displaces the realtime HR data.

I've privately uploaded before/after downloaded FIT files for that other beta ticket so that might be specifically useful, I can upload again if desired.

I am also more than happy to run any alpha/beta firmware to help debug this problem, I am an advanced experienced user (and also a coder in other environment)

  • 0 8 months ago

    Contact Garmin Support directly. 

  • 0 8 months ago

    Another factor on my wishlist for HRM-PRO would be user-settable wave peak voltage.

    Because after thinking about this another day or two, it's not just the sampling window.

    I believe the HRM-PRO firmware is actually too sensitive and is detecting PVC waves that other sensors like optical ignore

    But they are properly ignored by optical by accident because they don't have that sensitivity.

    Not holding my breath for such an advanced feature since we can't even get the current battery voltage displayed in the ANT sensor display and only the useless "ok" (which it is not, if the battery is 2.86 volts, it's about to fail/dropout and you can only see the voltage if you decode the FIT file yourself and look at it)

    BTW other straps are capable of EKG readings with just the two pads, HRV is only one dimension of the waveform (the timing) but if Garmin broadcasted the actual intensity voltage of the wave detected, you would have EKG function. That feature won't happen until all Garmin competitors have it (like apple watch)

  • 0 7 months ago

    Oh this is absolutely fascinating.

    Apparently ANT+ only can sample at 2hz which means HRV data over 120bpm is likely lost

    This would explain why downloading afterwards is so much more accurate.

    I should try bluetooth.

    But alternately, can the HRM-Pro-Plus support the new 100hz sampling rate that is in the Fenix betas?

    Very interesting reading:

    https://the5krunner.com/2024/02/19/why-i-moved-from-garmin-to-polar-h10-alphahrv/

    "HRV is not always transmitted correctly by Garmin over ANT+.

    Garmin transmits each RR beat separately over ANT+,

    however, Garmin only sends data at 2Hz,

    so beats can be missed when HR exceeds 120bpm.

    Whereas Bluetooth can have up to 6 beats sent at a time

    and alphaHRV sends 4 hence giving accuracy to 250bpm.

    Bluetooth 5.X should also include Forward Error Correction (FEC)

    although that won’t have much of an effect, if any.

    Note: I am 99.9% happy with the regular HR I get from my Garmin HRM-PRO PLUS

    it’s only in the case of sporting levels of HRV where Garmin appears

    to have historically cut corners to boost battery life on its HRMs"