Every time I'm going for an easy run, my HR is under 150 for the first half and then it always finish over 180. I know it should be at 75% on easy runs but it never stabilize. Like instead of being constantly at the same bpm, it continues going up without increasing the pace. I'm running easy and relax but my HR is going higher and higher. I can't hold 75% for all of my run. Is it possible to have a max HR of 240 ?? Because i'm running easy at 185...
An other weird thing is that yesterday, I did a fast 20min run on treadmill (hard, faster than tempo effort) and my HR got to 209 for a few min (at around 12-14 min) and then, it went down at 170 for the end of the run. How can my HR go below my easy run HR on an High intensity run?