This reminds me of a question posted hear years ago - "What happens if I go over my max HR"?
Stop trying to define "Max HR" in some absolute terms. It is simply the highest HR you have achieved when you're completely burying yourself. This usually comes at the climax of huge effort, e.g. at the end of a sprint.
When I was in my 40s, I saw 183 several times. I may have seen 184 once... maybe. I counted 183 as my max. Those were painful efforts. I once saw sparkles at the edges of my vision. I remember tasting copper. I'm 51 now. Last month, I saw 180 for the first time in a while. So, that's my max now.
I know from lots of racing (mtn bikes) and years of road riding, that I can average 92% of my max for up to 2 hours. So, when it was 183, I'd shoot for a 168 bpm for races. Now, I want to see 165 or so. (mountain bike races are essentially time trials - once you're free of the crowd, you just go as hard as you can 'til you see a big inflatable finish line)
I also know that, even if the climb is "only" 30 min., I can't hold much over that 92% - I'll blow up. I can go up to 175 for a very short period - like a steep section - but, I've got to "repay" that with some recovery under 160... that 92% avg is magical... at least for me.
Last edited by Zaskar; 09-10-19 at 02:35 PM.