Why Wear Running Shoes?
Running shoes work for running because they are designed and manufactured to meet the demands of bearing three to four times the body’s weight on impact, are designed for the biomechanics of running, and are biomechanically (and, to a lesser extent, terrain) specific.
Running shoes are designed on lasts, or forms that are models of the human foot. These lasts have shapes ranging from curved to straight with variations on the degrees of the curve, which make the shoes appropriate for the various foot shapes of runners. The term last also applies to the methodology of construction. A combination-lasted shoe stitches the upper fabric underneath a cardboard heel to provide stability. A slip-lasted shoe stitches the upper directly to the midsole, ensuring flexibility. A full-board-last (cardboard from heel to toe) shoe is the most stable lasting technique but currently is almost nonexistent in shoe manufacturing.
Theoretically, curved slip-lasted shoes are designed for higher-arched, rigid feet, whereas straight combination-lasted shoes are designed for flatter, more flexible feet. Because flat feet tend to pronate (the inward rolling of the rear foot, controlled by the subtalar joint) more than high-arched feet, straight-lasted shoes, with the aid of stability devices embedded in the midsole, help limit the rate and amount of pronation. Conversely, runners who underpronate should wear curved to slightly curved slip-lasted shoes, which allow the foot to generate as much pronation as possible to help aid in shock absorption.
Many runners err in choosing shoes because they do not know what foot type they have. If an underpronator trains in stability shoes, predictable injuries like calf pain, Achilles tendinitis, and iliotibial band syndrome will occur. If an overpronator trains in a cushioning-only shoe, stress injuries (including fractures) to the foot, tibia, and the medial knee likely will occur. For most runners, a qualified employee at a running specialty store can evaluate foot biomechanics, possibly by using a treadmill and a video camera, and successfully recommend multiple shoe models that, in theory, will prevent injury and provide a pleasurable ride. Occasionally, evaluating the foot becomes tricky due to motion not seen clearly by the naked eye, and a slow-motion camera may be needed to ascertain true foot movement. This is rare and usually not found in recreational runners due to lower training volume and velocity. Understand that biomechanics can change; what was once corrected may no longer be a problem, and new problems can arise.
This is an excerpt from Running Anatomy.