Remember, running a race is something you have to build up to, and it takes a lot of stamina. While you're training, don't be afraid to alternate between running and walking. Though it's less strenuous than running, walking still keeps your muscles engaged. It's particularly important for novice runners who are working on getting in shape. When you've run until you're out of breath, slow to a walk until you recover, and then try another burst of running. The further along you go in your training, the less walking you'll need to do.