This function of the ankle is essential in running both at the initial contact with the ground and to propel the weight of the body forwards by pushing off the ground. As the foot is a complex structure consisting of 26 bones and 33 articulating joints, movements can occur in several ways simultaneously. For example, ankle dorsiflexion is a part of pronation and plantar flexion a part of supination when the foot is weight bearing (Dungan et al., 2005).
Pronation and supination movements are essential for shock absorption, and propulsion of the foot off the ground at the end of stance phase. In pronation, the joints in the foot decouple and the ankle splays out medially (internally). During supination, the arch lifts and the foot becomes a rigid lever in preparation for propulsion. With this, both movements are essential for correct function during gait.
Most of the muscle work in running involves eccentric contractions to shock absorb and stabilise during the pronation/dorsiflexion phase. During supination/plantar flexion, muscles work concentrically in propulsion to move the body forwards.
If the ankle joint motion is restricted, soft tissues around the joint and neighbouring joints consequently have to work harder to attenuate impact shock and create stability about the lower leg joints. Consequently, this can increase the risk of injuries.