You can read the details here.
What really caught my eye was his summary:
That still leaves us a proven path to faster marathons: Train long, recover appropriately, run some workouts at your goal pace. When you do this, your body naturally makes all the right biochemistry decisions and adjustments for you. It optimizes your utilization of lactic acid and calcium ions, and you can run longer and faster.Train long (that is the distance day), recover appropriately (that could be interpreted as running every other day), and run some workouts at your goal pace. Gee, doesn't all that sound like the FIRST Plan?