In one embodiment, a selectable-rate spring comprises a flexure bar connected to a rotatable shaft, the flexure bar having at least one arched portion. The selectable-rate spring also includes at least one rotational contactor connectable to a link member, wherein the rotational contactor rotates about an axis while maintaining contact with the arched portion of the flexure bar. As the rotational contactor rotates, it changes the connection stiffness between the rotatable shaft and the link member.