Marc Silver explains:
You have to get to a bus stop to catch the once-an-hour express … or to a restaurant to meet a friend … or to a doctor’s office. You’ve got maybe a half a mile to cover and you’re worried you’ll be late. You run, then you stop and walk, then run some more.
But wait. Wouldn’t it be better to run the whole way?
Not necessarily.
A new study by an assistant professor of mechanical engineering at Ohio State University tests the theory that people subconsciously mix walking and running so they get where they need to. The idea is that “people move in a manner that minimizes energy consumption,” said the professor, Manoj Srinivasan.
Srinivasan asked 36 subjects to cover 400 feet (122 meters), a bit more than the length of a football field. He gave them a time to arrive at the finish line and a stopwatch. If the deadline was supertight, they ran. If they had two minutes, they walked. And if the deadline was neither too short nor too far off, they toggled between walking and running.
More at National Geographic.