Foot orthoses are commonly used in the management of overuse conditions in the lower limb. Mechanically, foot orthoses have been shown to result in only small lower-limb kinematic effects. However, it is conceivable that they act with the shoe as a cushioning interface between the ground and the foot, absorbing energy at impact. Energy absorption at the foot is primarily contributed by active resistance to subtalar joint (STJ) pronation (frontal plane) and compression of the medial longitudinal arch (sagittal plane). We have shown that much of the energy absorbed at the STJ is achieved through stretch of the m. tibialis posterior (TP) tendon [3], however it is feasible that orthotics might alter such energy absorption and potentially change the contribution of the TP muscle and/or tendon and thereby reduce the required muscle activation.