The common definition of HIT as submaximal efforts (80-95% of maximum heart rate) is not very helpful.

“nevertheless, hits are typically defined as submaximal efforts so uh sub maximal would be generally 80 to 95% of a person's maximum heart rate but I will just tell you right now out of the gate I think that definition is not that helpful because for example when I do my zone 2 I'm doing it at 80% of my max heart rate not because I'm targeting that but because that's the heart rate I end up being at when I'm in zone two well that's clearly far from submaximal um and conversely 95% of Max heart rate is truly uh a huge effort”