1. Allow Enough Time
In almost anything worthwhile, and especially ultrarunning, rushing to achieve success is a big mistake. Our culture has conditioned us to reflexively expect quick success. But quick success is the artificial, largely illusory, lure of an unsustainable civilization. Most people need eight to twelve months of regular running, averaging thirty to forty miles or more per week, to build the basic
cardiovascular capacity and endurance needed to run an ultra. Most will already have completed a marathon, or at least have substantial long-distance-running experience.
Genetically, all humans are built for running, but culture has separated us from nature and it takes time to readapt. While 30-40 miles per week is a minimum, you’ll probably be better off gradually working up to 60-80 mpw. If you are young and have good biomechanics and big dreams, you may be headed for 100 mpw or beyond. But remember, more is not always better. And getting to your maximum mpw as quickly as possible is almost always a mistake.
--From the appendix "Notes for an Aspiring Ultrarunner,"
in my forthcoming book The Longest Race (coming in October)