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
I think it is pretty accurate for elite cyclists and pros. For others, it is useless. My peak power is 20% less what it was 30 years ago. My 20 min is depressing. My hour is tourist level.
To be clear I'm here to post about my kid and those I know, not about me. But sure, I can hit 1,500W any time I want at near 60.
I still remember doing these tests in my 20s and sometimes in the sauna (longer story). The 20 min thing applies for a certain age and certain fitness.