Heart rate too low during activity

You will find many discussions on the forum about issues with OHR for Instinct and all Garmin devices. I suspect you'll find the same for almost all OHR devices (Apple watches seem to have an edge with OHR - but it varies a great deal by individual).   If you want accurate HR measurement during most strenuous activities, you should use a chest strap.  You MIGHT get better results by sliding the watch a little further up your arm and tightening the band during the activity.

had same problem with my Fenix 5. Garmin said it was problem with the device. got a new Fenix 5 from them works much better. 

Hr strap is only a little more accurate for me

Same here. Negative 50-60 beats compared to my heart rate strap. I’ve been wearing both during my cycling activities. I’d expect some sort error given it’s a wrist wearable but I think that kind of error is really bad for a Garmin product. 

Yes. I had same problem. I stoped wearing Garmin instinct. Now I have Samsung active 2, always showing me hr. There is problem with hr senzor in garmin.

This article explains quite well why we are not going to get accurate heart rate measurement from wrist worn monitors.

valencell.com/.../

I have an Instinct solar.... over a year now and have found the pulse monitor to be accurate.  Resting HR mud 50s and climbs appropriately with activities and exercise.

However just 3 days ago I had a low HR alarm although I didn't have any symptoms or issues.

Connect app reported 35 BPM which I guess was a temporary false reading from watch position changing.

So far so good since but that was weird.

69 year old male BTW. 

For about 10 years before I got my instinct I ran with  Forerunner 305 with a a chest strap heart rate monitor which is far more accurate than the optical on the Instinct. Comparing with the 305 the Intinct reads accurate at rest and walking but is 30 bpm high for running and 15 or 20 bpm low for strength training.

interesting results you are getting.  I appreciate the article linked previously. Very thorough coverage of the topic.

I also have the same problem on Garmin Mach 1. Sometimes works acceptably but sometimes showing too low HBR and nothing can improve it. I try drying my wrist and the watch but it seems that this is not the problem.  

I had never had this problem with medium range smart watch of Fitbit..