Absurdly high wrist-based HR AFTER activities since update 19.18

i guess its a bug in the firmware, i see this happening randomly since 18.XX firmwares, try to make a backup and then a factory reset to default in the watch, and test then

I've seen no evidence that factory reset can help in such a case. It's a bug that Garmin implement since early 17.xx FW. and the manufacturer does not consider it necessary to repair it. Have the same behavior, but it comes very rare to me. And that destroys your training load completely. 

Thank you both for your thoughts. I did a reset ("Reset Default Settings"), but with little luck, as global_local suspected. Today's post-exercise spike was only slightly less pronounced:

As global_local says, this is annoying because it screws up all sorts of metrics, the daily maximal HR being only the beginning. And again, it seems strange that this issue would pop up out of nowhere and then be so persistent.

Don't know if this might be useful for someone familiar with the watch's inner workings: I have the HR-gauge on the watch face (always have), where I observe these spikes in real time. Today, it seemed to me that HR dropped somewhat whenever I opened the HR-glance instead. These were the three drops in the above graph.

Same problem here, but inbetween of a longer bike trip.

...another day, another absurd HR-reading: after an easy 145bpm run, my HR increases to ridiculous 240 (literally off charts for connect.garmin.com), and stays there for quite a while.

And yes, I've made sure to follow the "Optical Heart Rate Accuracy Tips", no tattoos involved, etc.

Garmin-Sierra, might you have any thoughts on this? Is this really something that we would just be expected to live with?

Thank you for sharing, Dennis! I have a few questions.

1. Does the same HR spike occur if you perform an activity without using your chest strap? 
2. If you perform another activity using your chest strap, finish and save the activity and then manually remove the strap from your watch's sensor list- does the spike still occur?
3. After you complete an activity, what do you do with the chest strap?  Where do you put it/how do you store it?

1. Yes.

2. /

3. /

Thank you for looking into this, Garmin-Sierra, I appreciate your help!

I've spent the last three days collecting data on your questions, but no clear answers, it seems.

Run 1, chest strap removed from sensor list after saving activity: no spike, plausible data.

Run 2, w/o using chest strap: no spike, plausible data.

Run 3, chest strap removed from sensor list after saving activity: I again got a pronounced post-workout spike, see graph below. The HR initially fell while measuring recovery HR, but started to ramp up right after saving, and before i was able to remove the strap from the sensor list, but it further developed into a full blown spike after removal, and continued for many minutes, even as I placed the chest strap well out of broadcasting range.

As regards what I do with the HRM-Pro Plus after activities: I usually keep wearing it for a few minutes (while walking home/stretching), and spikes seems to begin while still wearing it. This is also where I have tried selecting the run activity, after which the watch says "Ext. HR connected" and I have seen the HR drop to plausible levels (until I deselct the activity and HR again shoots up). Spikes continue for several minutes after I take off the chest strap. I usually hang the strap up to dry on a towel rack in the bathroom next door. It might still be in broadcasting range then (barely), although during today's spike I made sure that this is not the case.

Does this help or would you like me to collect yet more data?

Feel free to email me.