It's a subject that gets done to death on cycling forums and just ends up as pages of trying to prove/disprove various theory's on the subject, if you wanted to explore it theirs reams of stuff available on line, far more than someone like me could hope to cover in a couple of posts. It's like all training that supplements a sport, you don't know if it works until you try it, but unfortunately you also don't know where you would be at if you had not done it either.