The 10 Percent Rule

Increase weekly training mileage by no more than 10 percent per week. Joe Henderson, the first editor of Runners World, and Joan Ullyot, M.D., author of three womens running books, first popularized the 10 percent prescription in the 1980s. I noticed that runners who increased their training load too quickly were incurring injuries, says Dr. Ullyot. The Exception If youre starting at single digit weekly mileage after a layoff, you can add more than 10 percent per week until youre close to your normal training load.