Originally Posted by
jfmckenna
My understanding is that the math formula used to get your FTP from a 20 minute test is supposed to be representative of what you should be able to do over an hour. But It doesn't seem right to me. The last FTP test I did on Zwift, on rollers with a power tap hub I averaged 330 watts for 20 minutes. But there is no way I could hold 300 for an hour. I've done a few A races on Zwift and I'm like dying at 3.5kg/w and I'm looking at everyone else around me at 4.5 and 5kg/w and then just watch them ride away in the virtual distance.
Perhaps doing a 20 minute test on the road would be more realistic IDK.
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