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Hugh Herr: Back on Top


A Harvard Ph.D., an assistant professorship at Harvard Medical School, numerous patents, and a faculty position with the Harvard-MIT Division of Health Sciences and Technology. A lot of gifted academics might fit these roles. But how many are the subject of a National Geographic movie, an autobiography (written by a man only in his late 30s), and a Discovery Channel feature story? The list narrows to one gifted researcher and inventor, the Massachusetts Institute of Technology and Harvard's Hugh Herr.

But speaking with Herr in his Cambridge, Massachusetts, office you just might forget how all this got started. Hugh Herr is a classically understated, yet obviously determined, researcher and inventor whose work in novel prostheses and orthotics design and human motion study appears boundless.

Avid Climber, Poor Student

At age 17, Hugh Herr lost his legs below the knee following a climbing accident on Mount Washington in New Hampshire; hence his book ( Second Ascent) and the movie ( Ascent: The Story of Hugh Herr), which premiered in 2002. Despite these injuries, the man who describes his former self as a "terrible" high school student--who earned C's and D's with only "occasional signs of intelligence," and who was only interested in sport and rock climbing--is still climbing rocks. "I have so little time now," says a slightly frustrated--but smiling--Herr while gazing at a computer image of his 5-month-old daughter. "Priorities, you know." In this, the 50th year since the first ascent of Mt. Everest, Herr's well-honed priorities are making a huge contribution to the world of assisted human movement.

After taking a few years off following his accident, Herr earned his undergraduate degree in physics, then a MIT master's degree in mechanical engineering. He followed that up with a Ph.D. degree in biophysics at Harvard. "I've bounced back and forth between fundamental science and engineering," says Herr. His postdoctoral program in bioengineering was done in the lab where Herr now spends most of his time directing both the Leg Lab and Biomechatronics Group within MIT's Artificial Intelligence Laboratory.

"It really is true that my accident, in part anyway, led me to my interests now," explains Herr. "I was not satisfied with my prosthetic limbs because they did not seem to move like my biological legs once moved, even for normal daily activities." Still, he acknowledges that without discovering his love of math, science, and engineering while at Harvard and MIT, he would not have achieved the engineering accomplishments he has.

Amplify and Rehabilitate

"I'm interested in human amplification and rehabilitation systems," says Herr, "technologies that interact with human limbs--typically legs--that amplify function or rehabilitate." Herr and members of his research team study motion science and the biomechanics of human movement and balance. "We have to study novel ways of actuation, sensing, and control," explains Herr.

Herr gets excited both by doing fundamental science and "by developing devices that help people." One example, developed in collaboration with Professor Gill Pratt of Olin College in Needham, Massachusetts, is a leg prosthesis with a computer-controlled knee. Watching a video, in Herr's office, of a tearfully enthusiastic woman walking up and down stairs virtually normally provides a glimpse of what Herr is trying to do. "This woman is walking up stairs foot over foot for the first time in her life," explains Herr. The computer in her prosthetic varies knee resistance as a person walks. The result is a more stable gait, with fewer falls, hence the woman's--and Herr's--enthusiasm.

A more recent and ongoing project is a "fully actuated" ankle brace designed to improve the mobility of individuals suffering from stroke, cerebral palsy, and multiple sclerosis. These people often suffer from drop-foot, a condition where, while walking, the forefoot falls uncontrollably toward the ground after the heel strikes it. "With this device we apply a biologically inspired control, which outputs what a healthy ankle does," says Herr. Another video shows the previously limping man walking at a quick gait with good symmetry between his left and right side. "The brace has a motor system designed to simulate a normal muscle response," says Herr. "In the future more and more disabilities will be treated with injectable stimulators that take over the activation of the muscles."

"Just for ankle pathologies alone there are so many different devices that will be required to rehabilitate people," says Herr. Good thing, then, that he is a chronic problem-solver. "I think about problems 24/7 and usually have about 15 different projects that I dance around at the same time." It's not too surprising that rock climbing gets squeezed.

"Most of the things I design I cannot use," says Herr. A quick glance around his office provides evidence in support of this assertion: a pair of running shoes designed to help one run with less energy, for example. Other projects include studies with artificial and real muscle. "One application is to build a muscle-like motor or actuator for prostheses," he says. Because natural muscle has very good properties compared to synthetic motors in terms of weight, efficiency, and contractile function, he wants to use biological tissue or a synthetic muscle actuator as a source of movement in novel prostheses. "We also study how to control living muscle tissue by electrical stimulation of the cell," he says. Possible applications are in orthoses for paralyzed limbs. "In some sense the spinal cord is decoupled from the muscles so we're injecting a muscle stimulator to take over what the spinal cord once did."

"We are also looking into building humanoid control systems grounded in biomechanical principles of movement," he says. Translation: Herr is developing human-looking robotic appendages designed to move as humans move, with the stabilizing benefits of real legs.

New Ideas

Herr's laboratory varies in size from between five and 10 people. Everyone is involved in the study of motion control, biomechanics, actuation, and mechanism design. "It is creatively taxing to manage so many projects simultaneously but it is fun to be pushed creatively," he says. The people in his laboratory choose to work with him because "they know what I do and are turned on by this field," he explains.

But Herr's personal experience as an amputee sharpens his appreciation for prosthetic and orthotic design. "If there is a mistake in an engineering design it can negatively affect a person's life and lead to human suffering," he says soberly. "But a proper and functional design can be of enormous benefit and affect the world in a positive way."

Passion and Focus

Herr has designed his own climbing prostheses that allow him to continue enjoying his passion for rock climbing. But when asked if he is the person everyone in the sporting world seeks for prosthetic design, he shakes his head. "I would like to be that person but there is finite time and limited resources," he says. "I hope I get around to building fast limbs--the Porsches of artificial legs--but I'm not sure I will." His explanation: "I think it's more important to improve the lives of stroke patients than to get young kids to run even faster."

"For me, everything is about focus and passion. If I don't care about a project it will not be successful," he says, adding, with a laugh and emphasis, "I guarantee it."