The design process of a powered robotic ankle prosthesis presents many obstacles that must be overcome. To be practically implemented, such a mechanism must not only run on batteries, but sustain a long running time between recharging. Using springs to passively and actively store and supply energy to the robotic ankle, small DC motors can be optimized to perform high peak power tasks without sacrificing efficiency and net energy usage. Additional techniques are explored with the potential of substantially reducing the energy requirements as well as the size and weight of the prosthesis. The benefits of adding a unidirectional parallel spring with a Robotic Tendon are weighed and the possibility of actively varying the lever arm at which the spring force is applied is analyzed. The different actuation methods are compared to determine which methods work best in different gait regimes.