During the base building phase for 5K to 20K race goals, you must train your body to walk farther than your selected race distance. By dedicating a long training day each week to adapting your body to long walks, you gain physical, mental, and emotional benefits. The longer distances teach your body to burn fat as a source of energy, increase your capillaries’ capacity, and promote those other physiological benefits to which I alluded previously. Walking farther than your targeted race distance allows you to feel comfortable focusing on race pace instead of race length.
With all of this said, the base building phase is the easiest to understand. The hardest part involves determining at what pace to train. Easy miles must be walked at an easy pace. Make sure you can talk comfortably and maintain good race walking technique at this pace for many miles. Do not start out fast and then slow down. If anything, do just the opposite. Start slow, and if you feel good, pick it up a little later. However, do not sprint the end of the workout.
If you maintain a fairly steady pace, the distance makes the workout harder. In the base building phase, the workout really starts only after you walk half the day’s distance. Time on your feet, not pace, determines the effort of the workout. Therefore, the first few miles should always seem exceptionally easy.