Having said that, over the past 15 days, RHR has exceeded minimum heart rate (MHR) by an average of 15% ranging from 0% to 31%. Six of the 15 reading pairs had a difference greater than 20%. Five were between 10 and 20% leaving only four daily data pairs in the expected single digit range. And I am comfortable that 24/7 works well enough for me not to have any concerns about it's accuracy and reliability. YMMV in which case contact Garmin Support and help them make it work better for you. PS. I don't work for Garmin. I'm actually unemployed while I finish my PhD thesis. Yay! Two weeks to submission Heart rate zones are based on percentage, not BPM. The only BPM measurements you need are max heart rate, lactate threshold, and resting heart rate to do heart rate training. You can do a little math and adjust your zone percentages accordingly. williamwchuang. • 1 yr. ago. The HRM Pro and HRM Pro Plus have two major benefits over other heart rate straps: (1) running dynamics, and (2) memory to record events while not connected to the phone. If neither of those interests you, then a cheap HRM strap that costs $40-60 would be more than enough. 2. You could consider a full reset as well to see if that helps. Generally though the wrist based heart rate is not that accurate (at least not on the vivoactive) and I decided to buy a Fitcent heart rate strap to measure it electronically. That removes the dependency on the watch for heart rate but you still get the goodies during activities. Select Settings > User Profile > Heart Rate Zones. Select Based On, and select an option. You Now How Three Potential Options: Select BPM to view and edit the zones in beats per minute. Select %Max. HR to view and edit the zones as a percentage of your maximum heart rate. Select %HRR to view and edit the zones as a percentage of your heart rate As you can see on the left side the swimming activity statistics show the wrong HR data. Also the Graph of it is completely flat at 80 bpm. But training load and effect seem to work well. On the rigth however, the heart rate is shown. (I manually changed the activity of swimming to something similar to be able to set the correct swimming distance. Garmin Fenix 5: 165/164: 78/79: 122/121: 1: Garmin Forerunner 35: 166/165: 77/79: How Heart Rate Sensors Work. The optical heart-rate sensor found in most fitness trackers and smartwatches jkl9Gnq.