Proper footwear is essential not only to running fast, but taking care of your feet. There are three classifications of foot behavior when you're running: Pronation, Overpronation, and Underpronation. Regular pronation is when you run, heel to toe, this only has a slight inward roll and will create no problems. Overpronation is when your foot rolls inward at an excessive degree, and can cause problems in your ankles, knees and hips. Underpronation is where there is no roll, and can also cause problems in the ankles, hips and knees because there is no diffusion of force from the impact. For regular pronation, a cushioned shoe is recommended. People who overpronate should use motion-control shoes. Finally, people who underpronate, and stability shoe should be worn. I am a regular pronator so I bought cushioned shoes (above).