When Zac Vawter lost his right leg in a motorbike accident, he thought he'd never walk properly again. Now, he's managed to use a bionic limb, hardwired into his nervous system, to climb 103 flights of stairs in the annual SkyRise Chicago skyscraper climbing contest.

Vawter's prosthetic leg is worth £5 million, weighs 4.5kg and uses two motors to power the knee and ankle separately. Amazingly, the limb uses targeted muscle reinnervation (TMR) to connect nerves severed during Vawter's accident to viable muscles. In fact, nerves that would usually control his lower leg are rerouted to his hamstring: when he thinks about moving his lower leg, electrical impulses are fired to that muscle, and they're then converted into control signals in the bionic limb.

The result? He can climb 103 floors of freakin' stairs, in a time most of us would be proud of. He finished the climb in just 53 minutes 9 seconds, reports AP, and looked pretty relaxed throughout.

While Vawter is heading back home, the limb will remain in Chicago. The researchers behind it, from the Rehabilitation Institute of Chicago, Vanderbilt University and MIT amongst others, still aren't happy with it. They hope to improve its performance yet further — but say that it will still be years before the limb hits market.

Regardless, it's damned impressive that a limb can respond to a human's thoughts — and then power him up 103 flights of stairs. Well done, Zac. [AP]

Image by AP