Optical HRM still totally wrong with 21.19 - In fact, worse than ever

I experienced this problem in about 1 in 3 activities - initially the recorded heart rate would be far too low, then suddenly jump to a plausible value after 5-20 minutes. For the last couple of weeks, I have taken the watch off my wrist and put it back on when starting an activity, on the screen where GPS is acquired, and I have not seen the problem.

My theory is that this causes the sensor to re-acquire your heart rate after it puts the sensor into high-power mode at the start of an activity.

The problem is not related to degradation of the sensor, as my 955 is new (and I also saw the problem on my Venu 2, which has the same sensor type).

Thanks for your input.
I will give that a try.

Still does not explain WHY the sensor struggles so much to find the right range with latest firmware, but to force it to start from zero and find an initial value sounds logical.

So some updates from wintersports...

this weekend i did some crosscountry skiing (skating)

OHR was a total disaster  but of course you your arms and wrist is constantly in movement here. So this is a real challenge for the sensor.

And backcountry skiing was a bit better but also had some problems locking the real HF. (the line in the middle was a break)

Next time i will try taking off the watch at the start.

5767025 said:

I have taken the watch off my wrist and put it back on when starting an activity, on the screen where GPS is acquired, and I have not seen the problem.

So I tried this yesterday with walking and it looks quite good:

The pulse starts off quite low (which is realistic as I stood there some time waiting), moves quickly up to a realistic range for this activity (85-100). It is not perfect, still some "rough edges", but overall there are nearly none of the really big jumps and drops and I think the range is correct.
Garmin-Sierra Would that not be something for the developers? It seems, that it really makes a difference to "force the OHR to start from zero". Why not just integrate that by software switch at the start of an activity?

To compare, two days ago:

Before this walk, I did NOT take off the watch and we see the problems I had quite often: Range is too low in my opinion and the pulse goes down at the end for no visible reason (usually, the longer you go with steady effort, your pulse will rise at least a little...). Also more of the sudden jumps and drops of 10 or 15 beats.

I went out for a walk today und I saw the behaviour Grumpy from dawn till dusk describes. For comparison the measurement of the HRM Pro.

(straight line in the middle was due to a pause during the activity)

I also took the watch off as recomended by 5767025 but it did not change anything in my case.

OHR did not manage to lock on the right heart frequency. I wore the watch under a fleece and a down jacket

My FR955 was previously able to get quite good OHR readings under all of the 'normal' conditions (inside/outside, hot/cold, etc.).  Since summer 2024-ish, OHR is too low and unresponsive to changes in HR (interval, for example, generates no/little change in OHR) and this occurs for an extended period at the start of the run activity (like 5-7 minutes).  Then, without an obvious trigger, the HR rises to the correct value and responds to intervals, etc. as anticipated.  Super disappointing.

giorgitd Yes, it started at some point (see the links at the beginning of the thread).
Would be nice if you also participate and post examples for the behaviour and describe what is the problem - the more input we give, the better!

Garmin-Sierra is in contact with me and they are investigating the issue - but it is important that we give them input also with every new firmware version, else the developers might be like "should be fixed", while it isn't.
For sure I will also start a new thread for 22.xx if it is still an issue then (and I fear it will be).

To add some more data:

This was a threshold run yesterday. Same problem as always. Wrist HR only becomes accurate after 15 minutes or more.

What is your question related to excatly?

I assume that the measurements of the chest strap are correct since the method is much more robust then the optical method.

So strap: correct, OHR wrong (either the sensor is not able to generate a correlating signal or the algorithm fails in picking the right signal)