Very poor HR accuracy

Noting new, you are telling to us...
HR-Monitor

I noticed the same thing this morning - cycling with an HR of about 80 bpm. Not likely!

Seems to me that there are enough "gripes" and issues with the device for it to be regarded as not fit for purpose.

This thread reinforces this view: https://forums.garmin.com/forum/into-sports/health-fitness/vivoactive-3-aa/1350551-vivoactive3-what-a-piece-of-junk

I see that Garmin have recognised the issues and have promised a fix but that promise was made months ago. How long can they just make false promises for?

I was out on the bike and the HR recorded seems right for the effort. When on the turbo I set the HR to broadcast. Perhaps that's the issue?

I've noticed that I need to really tighten the strap more than I thought necessary to get accurate readings on the bike, otherwise it doesn't go over 100bpm even when I'm maxed out, in guessing that being shook about on the bike causes it.

It seems unrealistic to expect a consistent heart rate reading from this device when on a bike.... at least we have the option to link a strap.

As far as I know it is widely recognized that wrist based heart rate monitors don't work well while cycling. Something to do with the angle of the wrist and light escaping. This is not a Garmin thing: all competitors struggle with the same. DC Rainmaker has noted this time and time again in reviews. For biking there are roughly 3 options:
-a regular heart rate strap
-an arm based optical heart rate band (Scosche Rhythm+, I've got it, works just fine)
-strapping your watch high up on your arm

Hope this helps.

A counterpoint is - in my experience - it's only the VA3's broadcast HR mode that is a trainwreck of dropouts and implausibly-low readings, even on a stationary bike.

The same device in the same position on the same wrist running on-board GPS and HR is 'fine' (even pounding around out on MTB trails). Perhaps a few bpm off one way or another relative to some other method of measuring HR, but still plausibly accurate...

In my experience only VA3's broadcast mode exhibits the abject failure to produce usable readings, these are on the scale of ~50% wrong or more (90~100bpm shown when I stop and manually count ~140ish or know given my experience, training and effort my HR should be well over 160bpm) or straight-up failure to read that the broadcast mode suffers. This is all well outside the variance one would expect between wrist vs chest-strap readings. I've tried for six months to get this thing to work; band tightness, position on wrist, arm, being covered by sleeves all appear to have no bearing on how unstable and inaccurate the broadcast HR data is...

In short, with the latest updates to VA3, iOS app, and Edge 520, broadcast HR is still unusably broken.

A counterpoint is - in my experience - it's only the VA3's broadcast HR mode that is a trainwreck of dropouts and implausibly-low readings, even on a stationary bike.

The same device in the same position on the same wrist running on-board GPS and HR is 'fine' (even pounding around out on MTB trails). Perhaps a few bpm off one way or another relative to some other method of measuring HR, but still plausibly accurate...

In my experience only VA3's broadcast mode exhibits the abject failure to produce usable readings, these are on the scale of ~50% wrong or more (90~100bpm shown when I stop and manually count ~140ish or know given my experience, training and effort my HR should be well over 160bpm) or straight-up failure to read that the broadcast mode suffers. This is all well outside the variance one would expect between wrist vs chest-strap readings. I've tried for six months to get this thing to work; band tightness, position on wrist, arm, being covered by sleeves all appear to have no bearing on how unstable and inaccurate the broadcast HR data is...

In short, with the latest updates to VA3, iOS app, and Edge 520, broadcast HR is still unusably broken.

Totally agree. The latest firmware update has helped and I now regularly show a HR of 120+ when I know from experience that it should be 150+. But it closer than the 90 I was getting previously when broadcasting HR. I agree that the issue is NOT fit around the wrist. I have recorded rides on the Vivoactive3 both on the bike outside and on the turbo. There were no issues with HR levels, they reflected what I expected. The issues cam when I turned on broadcast. I tend to ride outside with my wrist at a more angled position compared to a turbo when my wrist is straighter.

I have now given up with using the wrist HR for exercise (not sure why I bought the phone then!!) and have reverted to a (new) chest strap. I've bought the Wahoo in silent protest to the $hitty Garmin products and attitude to fixing this.

I will be due a new bike computer in the next couple of years and guess what that won't be Garmin either.

I am noticing that the HR accuracy has decreased on my watch. I've just done a Trainer Road session where is was at 90% of FTP for some intervals over a 45min period. According to my watch I didn't get over 90BPM and I recovered to almost average RHR in 2 minutes.

Pretty poor TBH. I'm going back to the HR strap.

I Also noticed that the HR is catastrophic
usually i'm using HR strap but i did a test with a stepper : the HR struggled to 70/90 BPM during the 15 minutes session,
when i swiched to a workout the HR went to 120 BPM.... I'm wondering if the type of activity choosen has an influence on thé HR quality