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A leg up on efficiency

That leggy friend who looks better than you in shorts also burns fuel more efficiently while walking or running, a researcher has found.

Herman Pontzer, a biological anthropologist at Washington University in St. Louis, made this discovery while testing a mathematical model for calculating energy costs for locomotion. He found that a tall person walking the same distance as a short person of identical weight and gait burns fewer calories, because longer legs are more efficient.

For his study, published in the February issue of the Journal of Experimental Biology, Pontzer recruited 10 people, four dogs and four Pygmy goats, then collected energy expenditure data as the two- and four-legged subjects moved on a treadmill.

The goats and the dogs — ranging in size from a Chihuahua mix to a German shepherd — were trained to move along the treadmill while outfitted in customized masks that were functionally similar to those used by humans in calorie studies. The animals were used to test Pontzer's mathematical model of the myriad variables involved in walking.

Moving on to humans, Pontzer found that long-legged people expended slightly fewer calories during locomotion: about 8 calories per mile for a 6-foot person versus a 5-foot person of equal weight. "For people standing around the water cooler, having long or short legs isn't an excuse that your diet's not working," he says. "It's not a big enough effect."