Dr. Herr, a biophysicist, designs computerized prostheses and artificial body parts as director of the biomechatronics research group at the M.I.T. Media Lab. He is also the founder of iWalk, which manufactures bionic limbs and joints.

Also, rock climber.

I’ve been accused of cheating. I loved the accusation because the day before, I was a cripple, and they were tapping me on top of my head — “Oh, you’re just so courageous.” That’s so demeaning. Then the moment a person with an unusual mind or body becomes competitive, it goes from “Aren’t you courageous?” to “You’re cheating!” The difference is performance.