I have used my googlefu now but I don't come up with any good research articles.
I read that a lot of elite riders train mostly on low intensity, is this the case and why? To increase fet oxidtion, and endurance muscle fibers and decrease the risk of injury?
This article says that it is not good (in isolation) in higher levels: http://en.wikipedia.org/wiki/Long_slow_distance
I also read something about 85/15 rule of race pace (85% of youre training should be lower then race speed and 15 % of the time at faster speed).