A shaft for a surgical instrument comprises an outer tube having a proximal end and a distal end, a central lumen extending through the outer tube, and a plurality of stiffening rods positioned around the central lumen. The plurality of stiffening rods may comprise a nonconductive material. The shaft may form part of an electrosurgical instrument. In another embodiment, a surgical instrument may comprise an end effector and a shaft having an outer tube having a proximal end and a distal end, a drive rod, and at least four stiffening rods positioned around the drive rod, each stiffening rod being positioned substantially immediately adjacent to the drive rod. The axial stiffness of the shaft increases incrementally during actuation of the end effector.