I was under the impression, from my own experience and the reports of others, that the wrist HRM on the Fenix 5x wasn't very good.
Personally I had seen the reading fluctuating very badly at times, showing 90 or so when I was walking (when I knew it would barely be 70 because I was testing it by counting my pulses in a minute) and regularly hitting 170 when I was pushing just a little on an uphill and would only expect 150 at most. Shaking my wrist was usually enough to make the reading jump around a lot.
However, I did a run some time ago where I was using the wrist HRM to try to keep a lid on my exertions during an endurance run. I wanted to keep the HR below 140.
I found that the watch was surprisingly consistent during that run, registering about 138 unless I was on an uphill or downhill where it might jump up to 160 when I was pushing and down to 120 when I was taking it easy.
Just recently I decided to test the Fenix 5x wrist HRM against a chest strap linked to a Garmin Forerunner. So with an armful of watches and the strap digging into my sternum, I set off (after rubbing a bit of spit onto the strap sensor pads, as you do...)
Initially I was elated. The two methods appeared to be exactly the same. Which made me suspicious so after checking the Fenix and turning off the wireless connection it had inadvertently made to the chest strap, I started again.
This time I was disappointed but not surprised to see that the Fenix wrist HRM was badly different from the fairly steady and expected results I got from the chest strap on the Forerunner.
Annoyed, I tightened the strap on the Fenix to the point that it was almost painful, and started running again. (Garmin says it should be tight but comfortable. Yeah, right...)
WOW! A completely different story with the strap done up tight. The Fenix using the wrist HRM more or less stayed rock-steady at 137, in almost complete agreement with the chest strap. (but different enough so that although I checked once again to make sure it wasn't connected to the chest strap, I was sure that it wouldn't be and it wasn't)
Now, just a caveat here. Initially I also used one of those silicone 'bumper' covers when I wear the Fenix, to protect my wrist-bone from getting bruised by the watch. Perhaps this had something to do with the watch 'sticking' better to my wrist (once I had done the strap up enough) Also it lifts the Fenix about 0.5 mm as the silicone goes slightly under the watch, though not enough to cover the sensor of course. I shall test again without it. (I have now tested 'bare metal' and it works much the same. i.e. the rubber buffer doesn't affect the wrist HRM and if the strap is tight enough for the HRM then the watch doesn't jiggle much and bash my wristbone anymore.
Anyway, now if I need the wrist HRM I do the strap up tight. Then I sit and watch the HR to see if it registers my normal 50-ish at rest. Then I shake my wrist around madly and see if the reading jumps around a lot or not. If it stays steady, I'm good to go. I'm sure I'll get used to that strange tingling sensation in my fingers eventually...
BTW, I don't use the chest strap when running because the last two times I did I ended up with scars on my chest from the bottom edge of it (not the sensor pads but just under the electronics pod). I've tried bandaids on the strap. Maybe I should try bandaids on me.
Would love to hear if anyone else has any experiences with the wrist HRM.
