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Fenix 7X oHR very "passive" during indoor cycling

LiviuNastasa
over 2 years ago

It's not the first time it happens, but since I noticed it every time during the indoor cycling, I have a question regarding the balance Garmin decided between battery life and oHR accuracy. If I use my Tacx connected to my H10 strap and my computer Tax Training app during an indoor cycling session without starting explicitly a workout on my Fenix 7X, the values captured by the watch are so much different from reality .. like the F7X is displaying (and storing for later reference in Connect) values of 50-65bpm whereas the H10 registers (the realistic) values of 130-150 bpm. This is not a limitation of the oHR sensor, as it is capable of measuring accurately the values if you access the HR glance putting the read function in a "more active" state - but for battery conservation reasons (I presume) Garmin decided that if you don't move that much (which is the case with indoor cycling) the sensor won't use "full power" readings .. leading to such low values as you could say that you're sleeping.

At the same time, if I wear my Polar Vantage V2, also not with an activity started .. in it's "default" daily use, the sensor displays values identical or close to the HR strap - which says that Polar is not "throttling" the sensor during the daily reads regardless of your movements. 

This behaviour is more obvious during indoor cycling since this activity doesn't involve too much moving your arm, "leading" the Garmin to think that you're not active and therefore throttling the oHR readings - but that leads to other questions: how reliable are all the other functions that depend on your daily regular HR values? Like for example, if the readings are not "real" all the time, but depend on how much you move your arm to suggest some kind of activity, how reliable are the High HR or Low HR alerts? Or energy expenditure? 

This is what Garmin displays in the Connect for the period I've performed the indoor cycling session - almost resting. This image shows 2 problems:

1/ the fact that oHR "overwrites" the information from the activity - if you have the activity (synced), why would you consider more "important" the oHR?

2/ the max values - it doesn't matter if the H10 strap registered 160bpm during the activity, the max in Connect (both mobile and web) is the oHR value - 108 bpm. 

At the same time, Garmin Connect also displays the activity registered and synced from Tacx, with the real HR values.

Polar, even if it doesn't have an explicit activity during the same period, at least notices the high HR and is very close to what the H10 registered.

So - even if I understand (somehow) Garmin's logic to favor the battery optimisation by throttling the oHR readings, in such cases like this you can't help but wonder how far the optimisation should go? It could create a trust issue and may transform your device from a daily wear into just a specialised sport watch (a very capable one nonetheless).

  • 0 over 2 years ago

    I really don't get these tests. Without sport profile there is no need for the watch to get the best HR possible, because there is little to no change. If you want to compare hr start an activity on the watch 

  • 0 over 2 years ago in reply to EnormoDerClown

    My point was not to test Garmin vs Polar or Apple in any way .. it was just a discovery of presumably a corner case when Garmin traded accuracy for battery conservation, nothing else.

    Does that discovery make a lot of difference? Not really, although it may cast a shadow of doubt regarding the accuracy of Garmin day-to-day use as a HR tracker. How many other (corner) cases are there, when battery life is favoured over accuracy? You say that, if you want accurate readings start an activity on the watch or even better add a chest strap for accuracy - and I agree that's what I do when I measure my workouts. In Garmin's defence, if I'm using my Edge computer connected to the HR strap during an outdoor cycling workout, the oHR readings are not as bad (low) as when doing the same indoor - a sign that Garmin takes into account the fact that you're moving (active) and the oHR readings are better, maybe not workout level better, but still.

    Garmin may decide to share with the users (community) that in certain cases (like indoor cycling) if you're not moving (at all, or very little) and the accelerators are not detecting activity, the oHR sensor is using a low-power reading mode which may not read high values of your heart rate. You could ask yourself how would Garmin detect  a high HR value, if you are laid down for a while ... would your watch trigger an abnormal high rate alert if you're reading in bed, but your heart rate goes to 150bpm? With the indoor cycling experience, I'm very much tempted to say NO, it won't.

  • 0 over 2 years ago

    Same in Epix 2 case. I thought it may be for the reason that I hold the handlebars tightly, thus my muscles are tight. But anyway now I just put the watch on the shelf for the indoor cycling and record the hr with edge connected to hrm. (if epix is off my arm 24hr is recorded from the hrm-pro, but if epix is on, then it overrides what HRM)

  • 0 over 2 years ago in reply to wojtek_b

    Good to know, then I'll put my Fenix on the shelf when doing the indoor cycling and registering everything on my Tacx with the H10.

  • 0 over 2 years ago

    Just to confirm same issue with Epix II. Actually loads of people with Garmins have this issue, its NOT a watch or software version issue. this is how these garmins seem to work; a low power/high power mode for OHR. Not that Garmin seem to admit to it..(though please point me to where Garmin clearly state how this works - would genuinely like to be proved wrong on this).

    As others have found, you need to kick the watch into high power mode, so start an activity, or broadcast HR etc. Forget about waving your arms around (particuly on the turbo, not a solution!) then at the end of the activity, once your HR calms down, stop and delete the watch activity. that avoids any conflict with your e.g. Zwift activity, which will be sync'ed, plus your activity minutes etc (which are only watch HR based, far as I can tell) also get recorded this way.

    Debate elsewhere whether this is a bug or a feature. its absolutely a feature, one garmin don't seem to be terribly proud of. if you only care about recording well defined activities, its totally fine. if you want 24/7 accurate health tracking, I'd not be so confident.