This 14-week plan is designed for advanced runners who have averaged 35 miles per week or more for at least six months and who want to develop speed over a longer distance. Each week features one day of rest and six days of running. That includes tempo runs, speedwork, and long runs, which start at 10 miles and peak at 15 miles. Not the right plan for you? Check out Runner's World's training plans for beginners and intermediate runners.