-
I have zero physiology / anatomy knowledge to back this up, but isn't there a literal pumping effect from running?
My highest HR (which must have been 8 / 9 years ago) was 195, running fast down a very steep hill at a very high cadence.
At the time, my highest was usually 185ish, in the back of speed sessions and hill sprints.
Nowadays I have no idea, as I can't hit max effort without aggravating injuries.
I thought I knew my max hr from cycling, until I started joining in a parkrun that ends on a racetrack