The foot has a longitudinal and transverse arch. The foot arches are held in place by cross bracing of muscles and held upright by tendons. Hence, the body weight is mainly carried by the three points of the heel, the first and the fifth metatarsophalangeal joints.
Bracing of the transverse arch:
musculus tibialis posterior
musculus peronaeus profundus
Together they 'wrap around' the middle foot like a stirrup from the inside and outside and hold the arch up.
Function of the foot arch:
The foot provides the first contact between human and the ground. In a healthy foot in normal position, the transverse- and longitudinal foot arches perform an important dampening role. The entire body weight needs to be carried by the foot when walking, while also reducing the load peaks on joints such as knees, hips, and spine. To do this, the foot arches subside upon ground contact of every step due to the load experienced, and the muscle tension builds them up again.
Biomechanics and cycling:
On subsidence of the foot arches the foot fatigues and the direct force transmitted to the pedals is reduced. Too much movement of the foot in the cycling shoe can lead to nerve and blood vessel constrictions which result in paraesthesia or numbness.