Originally Posted by burnthesheep

Lookup the concept of critical power if you're interested in this. I think that might fit with your question. I still don't completely understand it, but feel it's close to what you're discussing.

As for your first set versus second, that does kind of sound like the result of an all out one time effort for 8 followed by a flop. But 340 to 250 is drastic. I would have thought maybe a drop to upper 200's like 280, 290, or even 300 for the next set.

I don't know the term for when this is the case, but there's a word for when a person cannot repeat or recover well from strong single aerobic efforts. This sounds like it.

If you can do 340 for 8 once, the next set 300 would be tough but entirely doable.

Also caution on the percentages. Folks who aren't as "deep", those percentages should lag a bit. So instead of 95% of 20min many folks should do more like 92%. Shoot, some maybe even 90%. Then same thing for guessing at short intervals to long.

I ride with plenty of folks that can do 300 for probably 20min. Or 320 or so for 8min. But the number that could do an actual 280 or 285 for an hour, or 260 for 2 hours is much much slimmer.