PHal Higdon: Marathon: Intermediate 2: What's the difference between the Intermediate 1 and the Intermediate 2 Marathon Training Programs? A little bit of mileage, that's all. Runners who choose the latter run three 20-milers toward the end of the program instead of two. And there's a bit more mileage leading up to those 20-milers. Otherwise, the programs are basically the same. You would choose one or the other depending on how many marathons you have run and how your training has progressed. A logical progression would be to start with one of the Novice programs (1 or 2), move to Intermediate 1 for your next marathon and Intermediate 2 for the one after that. Or you may want to stay longer at each level before moving up. And you can even move backwards. The choice is yours. Each day, if you sign up for this program, I will send you emails telling you what to run and offering training tips. For more information and directions, visit the marathon screens on my website: halhigdon.com.