Read the first part of the answer, Greg's training for the marathon is based off of high miles and long tempos. Nick did none of that...
How was your training leading up to Houston different from your Chicago marathon build-up?
NA: The main thing was the mileage. I wasn’t doing the long-long runs, I wasn’t doing the long tempos. I probably was hitting between 100 and 110 [miles] a week leading up to Houston. The goal was to go in there and pace Brett (Gotcher) and be ready to run a fast half-marathon and be able to do that comfortably with him. Going into Chicago, we had the idea where we’re just going to run a fast marathon, so heavy mileage of 130 to 150 per week easily, and hitting a lot of 15- to 18-mile tempo runs and longer threshold-type workouts. Those were the main differences.
Other than that, I was doing the shorter tempo runs and shorter track turnover-type workouts before to get myself sharp and ready to make a 1:04 half-marathon feel a little more comfortable