Strange behaviour with Garmin HRM

Mff73

@false
Nice tests

marcrie

@false I’ve had a similar issue with a polar h9 strap. I connect it to the polar app and recognised that the battery is empty. Then I switched the battery and the hr values in the app were ok. Then I trained with the watch (s9pp) and the belt and got unplausible values after 10 min of running. Then I decide to change the soft strap. Within the next run I’ve got the same issues, bad hr readings.

Then I recognised the problem. When I connect the h9 belt with the polar app, the s9pp lost the connection to the belt. A reconnect of the s9pp with the hr strap solved my problem and would have done it, before I changed the soft strap.

Francesco Pagano

@marcrie So are you saying that the issue for you seems to be caused by the chest strap being connected to the Polar app and then to the watch?
I am quite sure that after my last experience with incorrect measurements I had just reconnected the strap to the watch, but I can try something more accurate

Francesco Pagano

@Swaddy61 It’s an interesting guess, but I wore the watch on my jacket sleeve so I imagine there really couldn’t be any HR reading from the wrist

cosme.costa

@Francesco-Pagano @Swaddy61 I do not know with Garmin HR straps but experience with polar H10 is that when you have strange values (on the watch or on a Garmin 530) is most of the times because of the strap, you can washmachine it and will see some improvements. In my experience when the battery is empty or very low it stops working.

What I can tell you for sure Is that Suunto doesn’t switch between HR monitors automatically, If the activity starts with the chest strap won’t switch to the watch OHR automatically, the same the other way around. You can test it starting the activity with the chest strap, remove it and you will see it.

Swaddy61

@cosme-costa You are right! Someone else on the forum had suggested it might switch back to the watch if the belt stopped, and as my Coros did that, it seemed quite likely. But I have tested, and you are right - it just stops!

So @Francesco-Pagano as the Garmin belt doesn’t appear to have a removable sensor unit we can rule out a ‘connector’, so that leaves 2 things to try - (i) wash the belt (check Garmin instructions!), and (ii) re-pair the belt.

Oh, and a third thing you could try - use some electrogel to ensure a good connection between the belt pads and your skin. I use Gadget Planet ABGYMNIC Conductive Gel - about €7 a bottle, and a bottle lasts many months using 3 times per week on the belt (you don’t need much). I used to get intermittent results before using the gel - so much more effective than just wetting the pads!

false

Oh, and a third thing you could try - use some electrogel to ensure a good connection between the belt pads and your skin.

From my experience - if hr belt is fine it works nicely even when it’s dry

false

@Mff73 I did my best

Francesco Pagano

I ran a new test today and something interesting came up.
I had the HRM chest strap connected to both my S9PP and to an old Garmin Vivofit watch so I could see my current HR on both. I started an easy run and at some point the Suunto watch again spiked from a reasonable ~150 bpm to over 170 whilst the other watch was displaying the expected HR, which corresponded to what S9PP on the pause screen.
This suggests me that Suunto watch is displaying a different value than what the chest strap is sending.
The funny thing is that this pretty much always happens at the same point, when I run a very short hill down and my pace and cadence increase for a few seconds. Today and previously it seemed that my “fake” HR corresponded to my cadence, so could this be a case of cadence lock?
In other cases when the displayed HR was way too low I can’t see any relation instead.

A Former User

@Francesco-Pagano I’ve not heard of cadence lock with HRM pro…

isazi

@Francesco-Pagano while cadence lock is something that can happen with optical HR (because hitting the ground can create artifacts for an optical reader), I cannot imagine how this could happen with an electrode. Unfortunately I have not used a Garmin HR chest strap since 2019 so I do not know what is transmitted, if heart beats or inter-beat time (although I guess the latter).

Mff73

@Francesco-Pagano
Are you sure that your S9PP locked on the belt HR before starting the activity?
If yes, your tests may lead to think that your watch is using wrist HR despite what you think. But how to prove this

TonyG

@Francesco-Pagano

I had these issues all the time with 9 peak & suunto 9 baro, and did loads of experiments to try and work out what was happening but more importantly how to resolve or stop the issue happening in the first place.

https://forum.suunto.com/post/114542

ODo67

Hello!
I’ve had two Hrms. Neither lasted more than 6000 km (1 year and a half for me ️). I don’t think they’re designed to last any longer, especially with the non-replaceable strap. Since I switched to Suunto for my watch, I’ve bought a belt that costs half as much and has a replaceable strap!

false

Does anyone know here how it works under the hood? I mean the belt transmits ready to use value of HR or the watch does some calculations before showing the data on the screen?

Francesco Pagano

@Mff73 Yes I only use the belt and I would know if I am starting an activity using OHR instead. As I wrote previously, am I even wearing the watch on my jacket sleeve so I wouldn’t expect HR readings from my wrist.

Francesco Pagano

@TonyG Thanks for the advice, I’ll try the strap position you suggested there. Today it happened again but luckily the HR went back to normal in a few seconds after I paused and restarted the activity.

isazi

@false I can only answer for the Suunto sensor, although I believe most chest straps work the same: the sensor sends IBI to the watch (the time in milliseconds between two beats) and the watch uses that to compute heart rate (watches may use different algorithms, especially on the filter side, to do that)

Francesco Pagano

After some time I am more and more convinced that this problem is related with wearing a jacket.
When running with just a synthetic t-shirt on warm days I haven’t experienced it. Yesterday I ran again with t-shirt plus jacket and the HR values were all over the place. I did some research, and it seems to be a known issue.
It’s just strange that the HRM is sending correct values, as displayed both on the Garmin step counter and on the S9PP on the pause screen, whilst the wrong values are displayed (and recorded) on S9PP during the activity.

Mff73

@Francesco-Pagano
maybe a data filter process difference between activity pause and activity recording ? Only Suunto expert in FW could say. It would not be logic, but who knows.