THE POWER OF HUGH HERR’S LEGS
SHOCK ABSORBERS:
Originally, walking caused discomfort to the area below Herr’s knees, where his legs had been amputated and afterward attached to artificial rigs. “His prosthetic guy, inspired by shock absorbers he had seen in Vietnam, put in cushions for added comfort,” said Piore. “They’re made out of soft, flexible polyurethane membranes.”
RACECAR TECHNOLOGY:
Carbon-fiber tops made from the same lightweight material as Formula 1 race-car chassis connect Herr to the socket of his prosthetic leg. “It is like slipping [your hand] inside a mitten,” said Dr. Charles Carignan, CEO of BionX, the company founded by Herr, which produces his legs. “A pin clicks into the socket that holds it [onto the leg].”
WALKING TALL:
One advantage of being a double-amputee: no limit to your height. As Herr told a TED Talk audience, “I can be as short as 5 feet or as tall as I like.” Piore said that Herr analyzed horses’ gaits “to see how they . . . [gallop] in the air and keep from breaking their legs on the way down.” This influenced the degrees of stiffness in his own legs and the naturalness of the stride.
TAKE CHARGE:
Plastic-andmetal ankles hold the hightech guts of the prosthesis, plus the lithium battery that must be recharged after eight or so hours of walking.
MISSILE-GRADE CONTROL:
Sensors in the ankle continually analyze Herr’s walk. “They’re the same kinds of micro-processors used in guided missiles,” said Piore. Carignan added, “The sensors measure forceof-heel strike, torque and angle of step [to] determine how much power needs to be delivered from a motor that drives the propulsion.”
A FOOT FOR EVERY NEED:
The carbon fiber “feet” Herr wears day to day have treaded rubber bottoms, like on an athletic sandal. For this photo, said Carignan, “he added a rubber cosmesis which looks like a molded foot with toes. It . . . allows shoes to fit properly.” Herr opts for very small feet that fit into tiny crevices when rock-climbing; for scaling icy surfaces, he switches to spiked bottoms.