Xiborg nu is a competition prosthesis particularly designed for sprints. Based on the biomechanics of athletes, the stiffness and thickness of the spring have been optimised to the effect that any elements unnecessary for running have been eliminated. In addition, the sprinting prosthesis has a completely new shape as compared to other models. The large curve facilitates push-off in the contact phase, while the proximal centre of gravity supports forward movement in the swing phase.