Going with the gear ratcheting mechanism, we’re thinking of using a spring-loaded lever and solenoid actuation system to trigger engaging and disengaging with the gear teeth.

drawing

This method only requires the actuator (solenoid) to be active upon ankle inversion trigger events. In engaged mode, spring-loading ensures that the lever engages with the gear without the need for the actuator to bear any counter forces. In disengaged mode, the spring-loading ensures that the lever is pulled away from the gear.