Photo: David McDermott/Flickr

Actually, it’s something more like efficiency than laziness, but whether we’re walking or running all comes down to energy conservation.

Researchers at the Movement Lab at Ohio State University have been watching how people walk, run, and transition between on treadmills. When the speed was increased from two to three meters per second, people broke into a run. They unconsciously sensed that changing gaits would save more energy than simply walking faster, so their bodies took action.

But the way you walk on a treadmill isn’t always the way you walk on solid ground. Researchers took this into consideration too, and gave the subjects a certain amount of time to cross 250 meters. They measured at which points people started running and how fast they were traveling. The result was the same: Between two and three meters per second.

So where does this research actually come in handy? Mostly in medical science. Prosthetics are reaching levels of sophistication that we would have only believed in science fiction films a few years ago. A paraplegic woman was able to move a robotic arm and feed herself a candy bar just by thinking about it. If scientists can engineer prosthetic legs to work with energy efficiency as the top priority, they might be able to better mimic natural human movement.