Fenix 6 Pro: Increased Heart Rate Inaccuracy (too high for running activities) Since Beta 11.75 and Now 12.20 Release

Agree with others who feel that some of this is software related (understanding that a chest strap will always be more accurate thn optical). Just tried an experiment after learning that my 6X was showing a heart rate well above a chest strap at my cardio rehab while using the "cardio" profile.  ( over 20 BPM too high) . Jumped on the treadmill at home and started a treadmill activity. My 6X is within 2 beats of my chest strap which transmits to the treadmill. If I stop my activity on the watch and switch to the "cardio" profile, while continuing to keep my chest strap displayed rate unchanged, my watch steadily increases the heart rate to well over the chest strap rate.  I then cancelled the activity and started another treadmill activity. The displayed rate steadily came back down, and was once again within 2 beats of the chest strap. 6X sapphire running 12.77 beta

Same problem. My heart rate when jogging goes alarmingly high according to Fenix 6 pro wrist. Up to 170!. Bought HRM dual strap and went for and easy run today monitoring wrist on watch and strap using Wahoo.  Heart rate on strap never went above 135, 170 on watch.  Then I experimented. I walked  slowly until heart rates recorded the same, at about 98. Then I ran vey hard for 500m. Heart rates were recording the same and peaked at 144. Conclusion. Wrist heart rate must be being influenced by the vibration/bounce of jogging Vs hard running. Rubbish. It needs sorting Garmin.

Same problem here!  It’s driving me crazy, since the previous 8 months of use had been spot-on accurate. 

I have been experiencing the exact same issue: the initial phase of a run has reasonably accurate rate readings, but then it jumps +30-50 bpm and doesn’t decline until I’ve completely stopped and been at rest for many minutes. 

As a point of reference, I’m an ultrarunner and prior to this latest set of updates I had been extremely impressed with the accuracy of the wrist HRM of the Fenix 6...

I had a 90 bpm HR and the optical sensor was measuring 160 bpm HR - it's an expensive piece nevertheless. I bought so far the 5 and the 6 (all top specs) but will never buy a Garmin again in my life!

I changed my 5+ to 6X Pro and my aversge rest beat while sleep rose from 46-50 to 60-64. I was without s watch about a month..got more than just a bit worried, that what is goin on... Today I checked my pulse eith proper equipment and had 6X at the same time and saw the difference..wtf Garmin??!

Using my 6x Pro Solar, I was running with a Garmon strap and noticed that my bpm was about 40 bpm higher than normal. So I took it off. Same problem with the wrist measurement. Everytime I run now at my zone 2 pace, normally 130bpm ish, my heart rate shows as 170plus. Crazy that is 10bpm above my mac and I've run for an hour like that!

• So for me it doesn't matter wist or strap......My Garmin is as useful as a chocolate fireguard

I just want to add that over the past 1-2 months, I've had the issue where my running heart rate often just jumps to a level that is impossible for me (160-180) or it starts out seeming to work and then jumps up.   Sometimes, the jump is after I take a water break and restart the run.    Every so often, it works properly.  

I've had the Fenix 6 for 8 months and this was not a significant problem until recently.   Very aggravating because VO2Max and other performance stats are heavily driven off heart rate.

You make a good point here.  I have noticed that when I run hard, the watch heart rate often will "reset" (ie, come down) to what seems like a more accurate level than the extremely high (and impossible for someone of my age) readings before.   It could be the jogging has more bounce.   Totally unacceptable, of course, but at least it's an explanation. 

Thanks.