Reduced heart rate readings during activities

I just received my Venue 3 watch and noticed that when I do my Kettlebell swing exercise it only goes as high as 100 ( i know/feel is really low) compared to where my samsung watch 5 pro would reach 160. Very disappointed as I was under the impression Garmin had the best health tracking. 

When an activity is being performed (not wearing a chest strap), all the 6 LEDs on your watch are turned on for better accuracy. During all other non-activity periods, only 2 LEDs are turned on. This is done deliberately to save battery life and also it is not required to have such accuracy 24x7. However, if you want to sample a more accurate reading during the rest period, navigate to the HR widget from the watch face, once inside the HR widget, all 6 LEDs are turned on and you should be getting a more accurate reading. 

PRK91 said:

However, if you want to sample a more accurate reading during the rest period, navigate to the HR widget from the watch face, once inside the HR widget, all 6 LEDs are turned on and you should be getting a more accurate reading.

Indeed, I observe described behavior. Thanks for this tip! Come to think of it, enabling HR broadcasting seems to do the same trick.

I will do a few rides to see if such approach solves the issue.

You're welcome

I have not tried the HR broadcasting, but it should probably work. Great :) 

I noticed something similar but when I record an activity.  Recording a walking activity outside and sometimes the HR reading goes as low as 60-70 while there is no way that this being accurate at all. It can read low for a minute or so and then boum back to 120 ish where the reading makes more sense. Or I shake my wrist a bit and the reading slowly increases. I was thinking that is because of cold temperature outside but I am not sure.  I don't know if my Venu 3 is defective or this is software related but indeed there is something wrong with the HR monitor. I did not notice anything similar on resting periods.  The HR monitor (v4) on my wife's Vívoactive 5 looks more accurate.  Where can we report this to Garmin?

You're experiencing phenomenon described here in "False Heart Rate Detection" chapter. I've had this happen many times during outdoor bike rides (with Venu 2 anyway) and indeed cold temperature can be the cause. As an idea, try wearing sweat wrist band over the watch (idea being you're protecting that wrist area from cold air) and see if that helps...

The issue I'm bringing up here is different, though. It's not that sensor occasionally misreads heart rate, instead it fails to recognize heart rate is increasing and it should switch into appropriate accuracy mode...

Broadcasting HR seems to be good workaround for the issue I'm observing.

I'm not positive opening HR widget keeps HR sensor in higher accuracy mode indefinitely until user closes the widget. HR broadcast, however, keeps all sensor lights on until you turn broadcasting off.

Guess I'll be enabling it from now on to have accurate data 

Once again, thanks for nudging me into this idea!

Would be ideal, though, if Garmin improved HR change detection and toggled accuracy modes accordingly 

Welcome to Garmin world!

Unfortunately your experience mimics mine perfectly. The sad truth of the matter is that in order to get HR readings that are anywhere near the actual values your Venu 3 needs to have started an activity (or at least start the HR monitor app). When I cycle without an activity started the venus readings starts off sort of okay only to get completely off after about 20-30 minutes of cycling. For me it normally stabilizes around 80-100bpm when the actual heartrate is 145-165 so it´s not just a little off, it´s off by a country mile and then some. 

I have brought this up with Garmin support and after initially supplying them with some videos of the phenomenon (the first line support agreed with me that this couldn´t possibly be normal) I was eventually told that no, this is actually by design. I was also told the usual gibberish about the extra sensors and all and saving battery and that there´s no way they can change this and they actually seem to believe this is not even an issue. I would agree if we were talking 5-10 bpm off the real HR but it´s about 50% off which makes it borderline useless even for casual daily HR monitoring (for calorie counting and such)...

I have thought about trying to make an app that would try to autodetect cycling and indoor cycling activities and start activities when needed so that the watch isn´t actually a burden when training (one more device to fiddle with and turn on) but haven´t gotten around to it yet. 

If it makes you feel any better the watch completely ignores cycling VO2max and the FTP is fixed at 200W anyway so it doesn´t really affect those metrics :)

Funny, yet the watch is perfectly capable of reading HR within like 1-2bpm compared to HRM-Dual HR meter strap, when the watch is forced into "high accuracy" reading state.

It's definitely not the accuracy issue, but recognition that HR is increasing and switching to appropriate accuracy level to continue reading correct values. And it very much sounds like something firmware/software would take care of, which I'd assume Garmin is developing.

"Saving battery" argument is also fun one. If I'm down to trade battery charge to have more accurate numbers - let me do it. Just like you let us choose between GNSS modes (GPS only, GPS+Galileo and other options), which affects battery life, why not let us do that with HR sensor...