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    Body Parts, New and Improved

    Amputee athletes are getting faster and stronger.
    August 15, 2007
    So he went to work in the machine shop, building new legs with rubber grips to grab rock, narrow stubs to wedge into fissures, and spiked feet for climbing ice.
    Two decades later, Herr, now director of the biomechatronics group at the MIT Media Lab, is still tinkering, building sophisticated prostheses that can match–and may soon outperform–biological limbs. His latest invention? The world’s first powered robotic ankle. Unlike other prostheses, the ankle captures energy generated when the foot hits the ground, using it to propel the wearer forward. Herr says that once the device is optimized, it will make the wearer’s gait more efficient than a biological foot would.

    Video: The robotic ankle in action.
    Calibrating the robotic ankle.
    Herr puts on the ankle.
    Rudy Garcia-Tolson
    At five years old, after a series of operations had failed to repair his deformed legs, Rudy ­Garcia-Tolson chose to have them amputated rather than spend the rest of his life in a wheelchair. Now 19, Garcia-­Tolson has set paralympic world records in swimming, and he competed in a half ­Ironman triathlon last year. For walking, he wears the Rheo Knee, an innovative prosthesis designed by Hugh Herr that adapts to the wearer. An embedded computer chip ­constantly modifies the resistance of the artificial joint according to its position and load, allowing it to adjust to changes in terrain and speed.
    Garcia-­Tolson uses a pair of lightweight knees for biking and special sprinting knees for running.

    Video: Rudy Garcia-Tolson demonstrates the rheo knee.
    Marlon Shirley
    In 2000, Marlon Shirley became the fastest amputee on earth with the aid of a ­carbon-fiber prosthesis designed especially for sprinting. Rather than mimicking the human foot, the Flex-Foot Cheetah, made by Ossur, an Icelandic prosthesis maker, takes its inspiration from the hind leg of the world’s fastest land animal.
    Shirley broke his own world record in the 100-meter dash in June at the U.S. Paralympic Track and Field National Championships.

    Video: Marlon Shirley, the Fastest Amputee on Earth.

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