Venu 2 heart rate BPM way too low during intensive exercise.

Each activity profile is designed specifically to be the most accurate during the activities that are most similar to them. Always use an activity profile on the watch that most closely matches the activity you are performing. For example, using the Elliptical app while running outdoors could result in incorrect heart rate being recorded. Using the correct profile will help with heart rate accuracy during the activity and for all day tracking, as heart rate is calculated differently for each activity type.

I have this problem too. I don't normally set my watch to record an activity, normally because I'm recording said activity on zwift or my bike computer for example), I expect it to pick up my heart rate regardless.

I noticed today that while my heart rate strap had my bpm at 145 my Venu said 90bpm. when I turned on broadcast heart rate mode on my watch it instantly shot up to match that of my strap (145bpm) 

when I turned off broadcast it dropped back to 90 odd again. 

this feels like a bug tbh, if my watch is going to track my heart rate then it shouldn't need me to start an activity to display an accurate reading

Thanks for your input, I agree that we shouldn't need to start an activity on the watch to accurately monitor the HR, I never needed to do this on the Fitbit I used for years and the Garmin Venu 2 is a much better smart watch so. It's disappointing and I agree it feels like a bug to me.

This appears to be a recurring issue for me, it's been fine previously, I do remember an older version of the firmware had a similar problem and I've only noticed again recently.