Hi,
During a running activity I took off my Garmin and hold it in my hand by folding from the strap and not touching its back (still running). I had thin black gloves anyway. The way i held was something like this: https://www.dcrainmaker.com/2019/09/garmins-vivoactive-4-series-everything-you-need-to-know.html
The weird thing is, the HR kept on working, changing the numbers from time to time! Normally i was running around 160-165 bpm, when I took off the watch it dropped a bit around 155 but that is it. The run is here, i took the watch off between time 1:01 and 1:05. Anyone tried something like this? The run is here: connect.garmin.com/.../4321106369
It just gives the impression that, the number we see is not the sensor reading but just some sort of algorithm output.