Overpronation running creates an inward roll of your foot as you land. It frequently happens with runners whose feet have a flatter arch, but it can happen to higher-arch runners as well. As the heel lands and the foot progresses through the gait, the pressure falls on the inside of the foot, from the inner heel to the big toe, rather than spreading evenly across the foot. Historically, overpronation running shoes have countered this with a medial post. More modern stability shoes do away with that midfoot bar and focus on advanced cushioning to support the stride.