I have tried searching the forum, but most discussions about optical HR sensors seem to be 4 years old. I am using a fenix 5 and try to run 3 times a week: 5-7km, 10-12km, and one interval run each week. In the winter I run on my Livestrong LS 13.0 treadmill which has a Polar chest strap. I've noticed that the HR is pretty similar between the fenix optical and the Polar chest strap for my standard runs, but that there is a significant variance when running intervals. The optical appears to lag behind the Polar response, so that if my HR increases from 130 to 160 during a sprint, the fenix will only read at 140 when the Polar is a 160, then they might align again at 150; the fenix never reaches the same max HR.
Would the Garmin HRM-Run chest strap correct this lag? I've seen several recommendations for the Polar OH1 chest strap - but this is also an optical HR sensor - will it be better than the fenix' wrist sensor?
Follow up question for those who upgraded from the fenix 5 to the fenix 6 - do you notice any improvements in HR accuracy?