The objective of this project is to enhance heel-to-toe running by increasing energy efficiency and speed. This is achieved by using a spring to absorb otherwise wasted energy when the heel strikes the ground and release it in the step off, as well as a curved bottom to facilitate heel-to-toe motion. Human feet are designed for standing and walking, but are very inefficient for running. I wanted to create an attachment to the leg that would make running fun by increasing one's speed and endurance. The spring below the heel absorbs the energy when the foot hits the ground, which reduces stress on the shin which would otherwise absorb this energy. After the heel hits the ground, the curved bottom rolls the foot into position for the push off, being in a more efficient shape for heel-to-toe motion. Once weight moves from the heel, the spring expands and pushes the bottom from the foot, aiding the user in pushing off the ground.