I can tell when I&#x27;m crossing 162bpm (I think it&#x27;s my personal aerobic threshold). If my HR below that I&#x27;m recovering; above that - fatigue starts to build up. Also I can tell when it&#x27;s above 171 - itchy feeling from lactate start to build up much faster.
I did VO2 max test once and went as high as 220. It feels absolutely horrible after 190 (long-time exposure to HR at that level most likely will do permanent damage to heart).