When buying running shoes to maximize your workout and prevent injuries, arch support is the first order of priority. Each person has a unique foot type, just like a fingerprint. This type is defined by the shape of the main arch on the foot, along with the extent of pronation, or inward rolling of the foot upon impact with the ground. The best way to prevent fatigue and hyperextension, then, is to relieve some of the pressure supported by the main arch of the foot. Pronation is the extent to which the main arch on the inside of the foot, while in stride, collapses inward upon impact. The best way to measure it is by seeing how worn the bottoms of the shoes are along the inner and outer curves. A neutral stride means that the arch collapses just enough for proper flexibility of the foot. Running shoes are much less of a hassle to choose once the buyer notices a neutral stride. However, there are many shoes that solve the problems of overpronation and underpronation of the arch. Overpronation is the complete collapse of the arch, and thus a complete rolling of the foot inward upon impact. This can cause hyperextension in the ligaments and tendons of the foot. Running shoes with high arch support solve this problem by limiting the arch collapse. Underpronation is the lack of sufficient collapse, which can lead to fatigue of the arch and pain in the hip or lateral side of the knee. Those who underpronate need neutral-cushioned shoes with little arch support to allow for the natural pronation motion. It may seem intuitive that underpronation goes "hand in hand" with high arches, but this is not always the case. Those with high arches can experience underpronation, a neutral stride, or even overpronation. Similarly, those with low or medium arches can also experience any of the three movements. Many people purchase running shoes by finding out their arch type through the "wet test. " This popular but faulty test tells only part of the story. It shows the wet imprint on paper of the bottom of the foot when not in motion. Since the shape of the arch doesn't indicate the extent of pronation, the "wet test" cannot determine foot type heel cups. Also, the test doesn't take into account bone structure of the leg, which can affect pronation. The extent of pronation is not necessarily the cause of all running-related injuries. Running shoes with little cushioning don't absorb the shock of each impact, and thus transfer the pressure to the arch insoles. To prevent damage to the arch, shoes can be complemented with "insoles," which absorb some of the shock. Insoles are not to be confused with external arch supports, a plastic shell that can be inserted in a shoe to restore foot structure and position during stride. When looking for running shoes, one must know their own foot type, composed of the shape of the arch and extent of pronation. It is important to remember that pronation and arch shape are independent of each other, and that a shoe's arch support affects the extent of pronation. Overpronation and underpronation can cause many injuries in the foot, but the arch can also suffer damage from a lack of shock absorption. The best way to choose running shoes is to know what your feet need to prevent injuries while still ensuring the maximum workout.