Field of Science


Are You an Efficient Walker?

I apologize. If you are one of those people who's most comfortable walking down the exact center of the sidewalk with your earbuds in, or a random left-and-right weaver, or a reckless swinger of pointy umbrellas, or someone who likes to walk your terrier tripwire-style, you may have heard me scuffing my feet behind you and making frustrated little noises. If you're simply slow, I may have alarmed you by zooming around your left shoulder like a maniac. I can't help it. I'm a speed walker.

Even if you're a more relaxed stroller than I am, though, maybe you've wondered why people walk the way they do. Is a super-slow walker conserving energy? Do little kids really tire out that quickly from walking, or are they just lazy? If I walk the 4.2-mile round trip to Bobtail for a cone of Cubby Crunch ice cream, is my expedition calorie-neutral?

Researchers in Texas addressed these questions by putting 48 people of assorted sizes onto treadmills. They observed people's strides, measured their oxygen use and carbon dioxide output, and calculated their metabolic rates. (None of the subjects were wearing Shape-Ups.) The subjects ranged from age 5 to 23. They had to walk at various speeds, from a very slow 0.4 meters per second (0.9 mph) to a brisk 1.9 meters per second (4.3 mph). A few of the young kids never figured out how to walk on the treadmill, footage of which I assume would be YouTube gold.

The researchers found that shorter people are less efficient walkers than taller people. That is, they use more energy to walk the same distance. And the reason is simple: since taller people have longer legs, they need to take fewer steps.

The findings were remarkably consistent. Thin people, obese people, and even little kids walk with essentially the same mechanics across a wide range of paces. The researchers infer that "humans establish mature walking patterns sometime before they reach six years of age."

You might view this as another advantage to being short (more exercise over the same distance!) or a point for tall people (we're so efficient!). Either way, if you care to know how many calories you're burning, the authors' rule of thumb is as follows:

At a comfortable pace, it takes about 1 calorie per kilogram of body weight to move forward a distance equal to your height. So if you know your weight in kilograms and the distance of your trip in, um, inches, you can calculate whether you burned off that ice cream cone. Or not.


ADDENDUM: Those would have to be calories with a little c, which are one 1,000th of what we usually call a "calorie." So you should divide by a thousand.

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