I was doing some tests with my HRM-PRO (8.80), trying some way to use running dynamics stuff for paddling sports. So I attached the strap around my kayak paddle, using a piece of floating foam around the paddle and under the strap for better fit.
Also the sensors were in contact with the foam. My first doubt was: how am I going to make the HRM turn itself on, since it only turns on when wearied in the body.
I thought that making the foam wet would close contact between the sensors and turn the strap on. It worked! This was confirmed by the strap showing connection with phone GC app and watch (Fenix 7).
So now the strap is on let's do some paddling using the trail running on the watch to see if it will measure some stuff like cadence, vertical oscillation, etc. It didn't work. Ok, didn't hurt to try.
But my big surprise was: the HRM was reading heart rate frequency all the time! Even submerged!
We all know optical HR sensor can "read" heart rate from anywhere, from walls to toiled paper rolls, since it's just light reflection that can get confused for the sensor, so the sensor is always trying to normalize it and apply it's algorithms to find some approximate HR frequency.
But until now I believed HR straps were much more serious stuff, reading heart electric pulses. I used to feel confident that if any HR reading was coming from my strap, it meant it was properly contacting with skin and reading heart signals.
Now I know that HRM Pro readings are also not reliable. Now I know that if it can't get a proper reading from the heart, it will just apply some dumb algorithm and try yo guess any HR frequency!
Shame on you Garmin!
HR straps were supposed to be serious stuff. If it can't get a proper reading, it should just send zero HR to the watch, so the user would know when to better adjust the strap, tighten it, wet the sensors or whatever.
Instead it just keeps sending virtual fake readings to fool the user!