Foot 

The foot is the most complex structure in the lower body. It is made up of many bones that interact with each other, unlike the rest of the structures of the lower body, in which only two or three bones interact.

The main function of the foot is to soak up the shock of the body's weight landing on it. The foot supports up to four times your body weight when you are running fast and it must bear up under at least 1,800 foot strikes for every mile you walk or run. Nearly all overuse injuries of the lower extremities are due to an abnormality in the way the foot hits the ground.