Do you have a "point of no return" heart rate?

Did Spencer +2 last night (6x3min @120%, anyone doing SSBMV2 will be familiar with the exquisite torture).

Something I noticed was that in the second-to-last interval, my HR hit 169, or about 97% of max. Then in the final interval, I got to about 93% before grinding to a halt 90 seconds in.

It got me thinking, is there a percentage of maxHR that you can only reach once in a session? If I reached 97% max in a ramp test or TT, I’d be able to go on a little bit further and push it up to 99+% before reaching exhaustion. But if I reach 97% and take a rest, it’s like my body won’t let me get it that high again.

I looked through some old workouts which definitely seems to back up that phenomenon. I’ve hit 96-97% a few times, but only ever once per session. Is this true for anyone or everyone else?

It has to depend on the amount of rest, right? Surely if you did a VO2max interval that pulled you up to your “no return” heart rate, then stayed on the bike in Z1 for an hour, you should be able to do a second such interval.

Anyway, heart rate doesn’t work for me and sprints – I can hit basically my max HR in a sprint, get some rest, and do it again.

Yes I suppose that should be a caveat. But I feel that if you do Z1 for an hour, it’s barely the same session if you start up the intervals again.

Would like to know this so that I know how hard to go at the start of a CX race.

If you get up to 97%, that sounds like a pretty hard start!

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IME - hard enough to not blow up, but also hard enough pending my call-up; to avoid the shit show at the first bottleneck/feature/run-up. I try to not lose any spots on the first lap. I’m usually around 180-190 off the start sometimes give or take a few beats and then settle in. My max heart is around 205-210. My average HR for a cx or even a crit is around 185. Everyone is different though.