Originally Posted by
furiousferret
The 20 minute formula is wrong because it is variable for every person, and not just slightly variable. Some riders crack at 35 minutes (Time to Exhaustion, TTE), others can go 80 minutes at relatively the same pace. Those with shorter TTE tend to have more fast twitch so they can go faster for shorter periods of time. People do shorter tests because an hour all out is not only hard physically, its hard mentally and logistically as well. Its also a selling point. The Trainerroad test is laughably bad as it doesn't even test FTP, more your FRC or what you can do over FTP.
FTP was what you can hold until TTE, but for the most part people just adopted the hour model.
So its probably going to be somewhere in the range of .88 to .96
Hmm. Taking us back to the KJ conversation, I spose you could just measure absolute training load with KJs, and base your intensity for work on previous bests. For example, Z2 isn't that hard to figure out, in the same way that Z5+ isn't either. This would work pretty well with polarized, because you'd either just go easy or go hard, and you wouldn't have to worry about toeing the line on sweet spot or threshold work.