How to train for the 2 most popular race distances, the 5K and 10K or 3.1 and 6.2 miles. Holt uses training phases to get you strong and then gently to get you as fast as your body will allow you to go by exercising at the ideal intensity (speed and heartrate). 5 phases last from 2 to 10 weeks depending upon your weakness and fitness level. Programs at 20, 30, 40, 50 and 60 or more miles per week and at modest, moderate and high intensity.