Originally Posted by procrit

Even during 20' intervals some portion of your power is going to be produced anaerobically. Maybe only a 5%, but that 5% is most likely what is causing your legs to "fail". Improving vo2 and efficiency is going to allow more of that power to be produced purely aerobically, increase the time to failure and increase your 20-60' power. Improving lactate clearance will allow you to use more of the anaerobic glycolytic system, while being able to keep blood lactate levels lower. Some of the 'efficiency' can be gained with low cadence / high muscle tension work, so you need less muscle fibers recruited to generate the same power. You might also do some 5-10' intervals as well to work on lactate clearance and possibly bump up vo2. Doing long endurance rides will also help improve stroke volume, not just at the beginning of a ride, but allow you to keep the higher stroke volume during longer rides. Lots of people don't understand that the reason the pros have the same FTP at the beginning of the race as at the end of the race is because of that. Lot of text book stuff, this isn't anything I came up with on my own. Hopefully it helps.

That's a lot of power too man, I'm jealous lol.