An underpronater or supinator rolls the foot outward as a runner or a walker. This does not usually happen in most runners but occurs in some.
Underpronators tend to land on the outer side of the heel and strike the exterior of their foot. They stress the exterior of the foot. The outside of the shoe wears down quicker. Because this type of walking does not absorb much shock, underpronators are prone to getting stress fractures or IT band syndrome. It becomes necessary to wear the correct footwear—cushioning, neutral shoes that absorb shock.
