A treadmill that trips you... for science

As part of research on how to make better prosthetic legs, Vanderbilt University engineers put people on a treadmill and made them stumble. Over and over. By better understanding peoples' stumble reflex, they hope to improve the computer-controlled stumble response in prosthetics. But to learn how people catch themselves, they had to trip them first. And that required building a stumble device into a treadmill. From Vanderbilt University:

Andrés Martínez strode briskly on the treadmill, staring straight ahead and counting backwards by seven from 898, a trick to keep his brain from anticipating the literal stumbling block heading his way: a compact 35 pounds of steel specifically designed to make him fall.

Special goggles kept him from looking down. Arrows on an eye-level screen kept him from walking off the sides. A harness attached to a ceiling beam kept him safe. Sure enough, when a computer program released the steel block, it glided onto the treadmill, and the Vanderbilt University PhD student struggled to stay on his feet...

“Not only did our treadmill device have to trip them, it had to trip them at specific points in their gait,” said Shane King, a PhD student and lead author on the paper. “People stumble differently depending on when their foot hits a barrier. The device also had to overcome their fear of falling, so they couldn’t see or feel when the block was coming.”

"A novel system for introducing precisely-controlled, unanticipated gait perturbations for the study of stumble recovery" (Journal of NeuroEngineering and Rehabilitation)