Based on evolutionary theory and the principles of 'biological design', the structure and 'form' of the human foot should reflect the mechanical and energetic requirements placed upon it. I.e A functional foot has to be shaped like a foot!

The ability to perform an unassisted bodyweight squat is considered a 'fundamental' movement skill and is a prerequisite for maintaining the strength and range of movement required for basic postural and locomotive tasks, such as lifting, walking and running.

A compromised foot structure is a major contributing factor in movement-related pain and postural instability. A Functional foot should provide maximal ground contact and stability in all directions, thus providing a stable base for all other joints to move in connection with.