[dude]

This last slide, I hope, will also help you understand why a guy who runs a 2:10 marathon trains a little differently than how books recommend that YOU train for a 3:20 marathon. As far as his body is concerned, he is running a shorter race than you are and is running much closer to his lactate threshold than you will be. Hence, he places a little more emphasis on faster training. Likewise, Mark Allen or Chris McCormick will place more emhasis or threshold and track workouts for their sub 3 hour IM runs than you should for your 5 hour run/walk.

As a side note, I'm fairly confident with the 2, 11, and 60 minute mark (as backed by literature). The 3, 4, and 5 hour marks are based on a little bit of conjecture on my part. I can't say for certain that a 5 hour IM runner should do ONLY endurance running, but they certainly should make it a very very large focus of their training.