This is the ultimate harness for developing leg power for both jumping and sprinting. It helps teach proper running mechanics, faster leg cycling, force production into the ground, and overall lower body explosiveness. The harness works by adding overspeed to the flexion of the hip and knee, and resistance to the extension of the hip and knee. This harness stimulates quicker and higher knee drive and more force production per step or jump. The Hammer Smith harness can be combined with our Ankle Shackle, Power Punch Belt, and speed cords for custom training variations.