A running shoe is designed to cradle the foot, and not just protect it from the pounding, but to optimize a runner's gait in such a way that a person can run longer and faster without worrying about injury. At its most basic, a running shoe is made up of an outsole, midsole and upper. The outsole is the bottom of the shoe, that durable slab of rubber providing traction throughout the gait cycle. The midsole rests atop the outsole, and provides cushioning and stability. The upper is generally made of mesh, synthetic fabrics or leather, and cocoons the foot.
Just as every run is unique, so every running shoe is designed for a specific type of runner. When selecting a running shoe, take into account the frequency of your training and your performance level. A shoe should fit comfortably and snug, but should not be so tight that your toes press against the front of the shoe or the top of your foot aches from the laces being too tight. If you run a great deal, it might be a good idea to look for a shoe that features the GEL® Cushioning System in the heel and forefoot.
Also, be aware of your gait. The three broad categories that define running shoes -- Cushioning, Structured Cushioning, and Maximum Support -- enhance gait by working with the natural movement of your foot, providing a more efficient stride. How you pronate plays a great part in a shoe's ability to enhance your running experience. Pronation is a normal, natural rolling motion that helps to attenuate shock. Some runners find that their foot does not roll all the way in, making the foot work harder to push off properly. This is known as underpronation (or supination). Conversely, a foot that rolls inward too much in known as overpronation. Runners who underpronate (or, supinate) would feel more comfortable with a Cushioning shoe. Overpronators do better with Maximum Support, and those with a more neutral stride would do well with Structured Cushioning.