With the Olympic distances set at 20 kilometers (12.4 miles) and 50 kilometers (31 miles,) 5k races and shorter are thought of by racewalkers as sprint events. By this reasoning, 10k- and 10-mile races are the “middle distances”—not exactly sprints, but not marathons either.
As the summer heat abates a bit, the early fall is a great time for 5k walkers to think about moving up in distance. Middle-distance races can also be a great marathon-training tool, as walking at the relatively fast sustained pace of a 10-kilometer or 10-mile race not only improves fitness, it makes marathon pace seem that much easier.
The New Albany 10K in New Albany, Ohio in September and the Crim 10-Miler in Flint, Michigan in August are two great opportunities to give the 10s a try. These 12-week schedules (links are to pdfs) for beginning, intermediate and advanced walkers can be used to train for these, or other, 10k races.