Just start using the Frontier X2 for 5 weeks, my HRV typically ranging 30-40, but last 4 days it jumped up to 116, 113, 184 and 181mS. HR is relatively the same, first thing each morning within 30 min of wake up, no abnormal alcohol and stress.

I run 60-80 miles a week, no weight issues, I routinely push my HR to 180 on speed work outs days ..…Read More