Effect of three-hour ankle joint immobilization with an ankle foot orthosis on corticospinal excitability and ankle joint angle excursion during gait

[Purpose] Ankle foot orthosis (AFO) is widely used to regain gait function after injuries and/or stroke; however, limited information is currently available on their effects. We herein examined the effects of three-hour immobilization with AFO on corticospinal excitability and ankle joint movement during gait in healthy volunteers. [Participants and Methods] The participants comprised of seven healthy volunteers. Corticospinal excitability and ankle joint excursions were evaluated before and after three hours of immobilization with left limb AFO. We measured motor evoked potentials in the tibialis anterior (TA) and gastrocnemius (Ga) muscles induced by transcranial magnetic stimulation. In a kinematic analysis, we focused on transition points, such as the timing from dorsiflexion to plantarflexion of the ankle joint and/or vice versa, during gait. [Results] Corticospinal excitability in TA and Ga both significantly decreased. During the normalized gait cycle (GC), ankle angles showed less dorsiflexion at 0% GC and 100% GC, and during loading response and mid-swing and terminal swing phases. Furthermore, less plantarflexion was observed during the initial swing phase. [Conclusion] This study showed that short-term ankle joint immobilization with AFO induces a significant decrease in corticospinal excitability and has an effect on ankle joint excursion during gait. Further studies are needed on the effects of long-term immobilization by AFO.