Originally Posted by PeteHski

It was the part about not being able to get above 145 on a hard, long climb that made me wonder.

I know we are all different, but I find my HR is quite dynamic in response to really hard efforts. For example yesterday I did a long simulated climb on my trainer, which had a steady 5-6% slope for the first 8 km and then kicked up to an average 10% over the last km, with a few ramps over 15%. I took it fairly steady on the shallow part and my HR stabilised at around 150 (all day level for me). But then I went full gas up the last km and went over the top at 190 (very close to max). My average HR for the last couple of mins was 184. So ignoring the absolute numbers, which I know vary widely across individuals, my delta was still around 40 bpm between comfortable Z2 and a sustained effort well above FTP. When I recovered over the top of the climb my HR quickly dropped back into Z2 as I was still reasonably fresh.

I don’t know much about you diesels to know what is a “normal” HR response to a sudden major effort. For me HR ramps up fairly quickly at VO2 max power level to within 5-10 beats of my max and after 5 mins I an bouncing off my limiter!