As a follow up to my last post, I do think that FTP can be broken when your testing is out of date, or just due to all the factors that have been mentioned in this thread; it's very subjective. The issue with training by KJs is that it's going to use your average watts over a whole ride. Would there be an "easy" way to get a minute by minute measure that would take into account more variable workouts, or does the average already do that?