Biomechanics is the study of the body in motion. Foot biomechanics studies the relationship of the foot to the lower leg. During walking and running the musculoskeletal system generates forces to propel the body forward. The foot serves two main functions. It acts as a mobile adaptor to adjust to varying terrain, and as a rigid lever for forward propulsion in locomotion. The two functions are time specific in that when the foot spends too much time being a mobile adaptor it is not spending enough time being a rigid lever and vice versa. Biomechanics of the foot analyzes how the various structures of the foot, work together to perform specific functions (timing being of utmost importance.) Excessive or prolonged motion or lack of motion will cause various deformities and pathologies discussed in the next section. Proper biomechanics allow human beings to walk, run, jump, and move freely without pain or dysfunction.