What is Pronation / Supination?
There are three types of pronation in the human foot; normal pronation, overpronation, and underpronation or supination.
Over pronation is when the foot rolls in at more than 15% causing the big toe to do most of the push off. People with flat feet tend to be over pronators.
The video below describes over pronation.
Under Pronation or Supination
Under pronating or supination is when the foot rolls in at less than 15% leaving most of the stress on the outside of the foot. If you have high arches chances are you under pronate.
See the video below to learn more about supination or underpronation.