The evidence suggests that the principle function of the rear part of the foot (the heels) is to dissipate energy during the impact phase of the stride. It would be hard to single out one structure but we know the soft tissue structures, interposed articulations and the digital venous plexuses play a major role in absorbing the energy of impact. The major reason for maintaining healthy heels in the foot.
NO heels no effective foot, no foot no horse!!!!