How is it possible to determine if a runner over pronates or under pronates?

The individual level of pronation, whether under, over or normal, can be determined by measuring the arch of the foot, which can be done by a professional foot expert or podiatrist or, alternatively, a simpler test can be performed at home. To perform the test at home, water is poured into a shallow pan, the foot is dipped evenly into the water and then the foot is pressed against a thick piece of paper or cardboard — it is best for the experimenter to stand naturally on the paper. The shape of the resulting footprint can then be compared to examples of feet that exhibit under-pronation, over-pronation or normal pronation.

• Normal pronated feet tend to have normal arches. The foot initially hits the ground along the outside edge of the heel and rotates inward toward all five toes at about a 15-degree angle. This technique spreads impact evenly over the foot.
• Over-pronated feet tend to have very low arches. The runner who has over-pronated feet initially hits the ground with the outside of the foot, much like with normal pronated feet. However, the runner then over-rotates the foot more than the normal 15 degrees, resulting in excess pressure on the inner two toes.
• Under-pronated feet tend to have very high arches. As a result, the runner initially hits the ground with the outside of the heel but does not rotate the foot inward at the normal 15 degrees. This results in less shock absorption during running, which can result in pain.