Zac Vawter thinks big. A software engineer and former competitive long-distance runner, Vawter’s blog is a list of his not-so-modest aspirations, things like winning a marathon or writing a new large-scale search engine. After the motorcycle accident that took his right leg, Vawter kept running and quickly volunteered as a test subject for experimental new therapies. Now the Rehabilitation Institute of Chicago is using that tenacity to help debut its new, thought-controlled prosthetic leg in a grueling 103-floor stair-climb of Chicago’s Willis Tower. And Vawter is determined to do it in under an hour.

Unlike many other thought-controlled prosthetics, Vawter’s experimental leg requires no electrodes be implanted in or on the brain, and instead takes its cues entirely from the nerves and muscles in Vawter’s upper leg. Researchers used a procedure called “targeted muscle reinnervation” to re-wire nerves previously bound for below the knee to the remaining hamstring muscle. Years of careful study then allowed them to read and interpret the signals meant for Vawter’s lost lower leg.

Lead researcher Levi Hargrove told the Chicago Tribune that Vawter “thinks about doing those movements and the signals travel down the nerves and are redirected onto hamstring muscle. The body doesn’t know that the ankle is not contracting.” Vawter himself calls previous leg replacements his “dumb” legs, since they are incapable of responding to his unconscious impulses. The 31-year-old will have to return the leg after the climb, however, and get by on the simple limbs until the technology is approved for commercial sale.

The targeted reinnervation approach, which was pioneered at the Rehabilitation Institute, has a number of advantages over traditional methods — if anything about such cutting-edge research can be called “traditional”. Intracranial implants that read motor cortex activity tend to degrade over time, and the immune response increasingly rejects their presence, while noninvasive brain scanning lags behind in accuracy and convenience. This implant-free solution requires only that the amputating surgeon preserve a section of unused muscle and rewire the shortened nerve clusters to it. This is admittedly a specialized procedure, but one the Rehabilitation Institute hopes will become increasingly commonplace in hospitals.

This is the first public demonstration of the Institute’s cutting-edge technology, which just two years ago was too clunky to safely wear outside of the lab. The stair-climb is thus an important hurdle for any prosthetic leg, since a fall down stairs is probably the biggest danger of a mechanical lower limb. Hargrove points out that prosthetic arms and hands have seen much more research precisely this reason, despite the fact that lower-body amputations are more common than upper-body ones. This is particularly important as military veterans are increasingly afflicted with nonlethal lower body injuries.

Vawter is approaching this new challenge with all his usual verve. The time he’s set himself for Sunday’s run is longer than he would have taken before the accident, but much quicker than he could achieve with any other prosthetic. Whether he meets it or not, his feat is sure to impress the world.

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[Image credit: Wikimedia Commons]