When you go for a run, your feet are supposed to rotate at the ankle to distribute your body weight and absorb the impact from the ground. Some people have problems with this rotation, however. If your foot doesn't rotate correctly, you either over- or underpronate.
Underpronation is when your foot doesn't rotate far enough inward when it makes contact with the ground. Because your foot doesn't rotate to its proper position, the weight of your body isn't distributed evenly across your foot. This can make it harder for you to keep your balance while you run and may cause you to lose speed or tire more quickly as well. Running with underpronated feet also makes the soles of your shoes wear out unevenly, resulting in you needing to replace your shoes faster than people who pronate normally.
Potential for Injury
Underpronation places a lot of stress on your ankles and the outer edges of your feet because your weight isn't evenly distributed. When you run with an underpronated gait, you are much more likely to twist your ankle on uneven surfaces than if your feet turned properly. The excess pressure placed on the outer edge of your foot and your smallest toes can also lead to blisters, stress fractures and other painful foot injuries.
One of the easiest ways to identify underpronation is to look at the wear on the sole of your shoes. Underpronation causes the outside edge of your sole to wear away faster than the rest of the sole; the difference is very obvious when compared to the inner edge, which may show little or no wear at all. When placed on a flat surface such as a table, your shoes will lean noticeably in the direction of the outside edge.
You can usually correct underpronation by choosing the right shoes. Running shoes designed to assist underpronation provide additional support along the outer edge of your foot, encouraging it to rotate to a more balanced position and preventing the rapid wear that might occur with other shoes. A podiatrist or other foot care professional may also give you shoe inserts that perform the same function, providing extra support to encourage a natural gait and correct your underpronation.
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