An adjustable negative stiffness mechanism, comprising: a central shaft; an outer annular member extending around the central shaft; at least two negative stiffness elements extending between the central shaft and the outer annular member, each of the at least two negative stiffness elements having an inner end coupled to the central shaft and an outer end engaging the outer annular member; and an actuator coupled to the at least two negative stiffness elements, wherein the actuator is configured to compress and expand the at least two negative stiffness elements to adjust a negative stiffness mechanical response exhibited by the at least two negative stiffness elements, characterized in that the actuator comprises: an inner cam surface on the annular member configured to engage the outer ends of the at least two negative stiffness elements, the inner cam surface comprising at least one peak and at least one recess, and a motor operatively coupled to the annular member to rotate the annular member around the central shaft, and wherein rotation of the annular member around the central shaft alternately aligns the at least one peak on the cam surface with the negative stiffness elements to compress the negative stiffness elements and aligns the at least one recess on the cam surface to expand the negative stiffness elements. a central shaft; an outer annular member extending around the central shaft; at least two negative stiffness elements extending between the central shaft and the outer annular member, each of the at least two negative stiffness elements having an inner end coupled to the central shaft and an outer end engaging the outer annular member; and an actuator coupled to the at least two negative stiffness elements, wherein the actuator is configured to compress and expand the at least two negative stiffness elements to adjust a negative stiffness mechanical response exhibited by the at least two negative stiffness elements, characterized in that the actuator comprises: an inner cam surface on the annular member configured to engage the outer ends of the at least two negative stiffness elements, the inner cam surface comprising at least one peak and at least one recess, and a motor operatively coupled to the annular member to rotate the annular member around the central shaft, and wherein rotation of the annular member around the central shaft alternately aligns the at least one peak on the cam surface with the negative stiffness elements to compress the negative stiffness elements and aligns the at least one recess on the cam surface to expand the negative stiffness elements. an inner cam surface on the annular member configured to engage the outer ends of the at least two negative stiffness elements, the inner cam surface comprising at least one peak and at least one recess, and a motor operatively coupled to the annular member to rotate the annular member around the central shaft, and wherein rotation of the annular member around the central shaft alternately aligns the at least one peak on the cam surface with the negative stiffness elements to compress the negative stiffness elements and aligns the at least one recess on the cam surface to expand the negative stiffness elements.