SSS 2010-02-12（在线收听）

It’s good to keep on your toes. Metaphorically, that is. Not when you’re actually out for a stroll. Because a new study suggests that it takes nearly twice as much energy to walk on your toes than it does to land on your heel.

Humans are among a small handful of animals that tend to strut heel-to-toe. Chimps and other apes do it, as do bears. But most critters bounce on the balls of their feet—think cats and dogs—while others trot on their toes, like horses and deer.

To find out whether our gait gives us any advantages, scientists asked 27 volunteers to walk on a treadmill all three ways: heel-first, ball-of-the-foot first, or up on tippy toes. The participants also wore face masks that enabled the researchers to measure their oxygen consumption. The results: the subjects walking on the balls of their feet, in addition to looking ridiculous, expended 50 percent more energy. The ones prancing on their toes needed 83 percent more energy. The study is in the Journal of Experimental Biology.

The bottom line: landing on our heels provides more leverage and limits energy losses to the ground. And does not look like a tribute to classic Monty Python.