How many calories do you burn while walking? That depends on your height and weight. And now researchers have devised a new mathematical formula to find out precisely how much energy you expend when walking.

Researchers hope their new formula will be applied to new, improved pedometers to calculate more accurate data in terms of calories burned when walking. Militaries may also find the equation handy, possibly using it to measure how many calories soldiers burn while carrying different loads, and thus how many calories they will need, said study researcher Peter Weyand, of Southern Methodist University in Dallas, Texas.

Scientists have known that shorter people, including children, use up more energy per kilo when walking, but they didn't know why. To find out, the researchers had 48 subjects, ages 5 to 32, walk on a treadmill at varying speeds. The researchers measured their metabolic rate and examined details about the way the subjects walked, such as their stride length.

The results showed that everyone, regardless of age, used about the same amount of energy for each stride they took. But because people with shorter legs take more steps to cover the same ground as those with longer legs, shorter people used more energy over a given distance.

Taller people are more economical walkers because they can take bigger steps and thereby burn fewers calories on a per-kilo basis. At the same time, tall people tend to burn more calories overall because they are generally supporting a greater mass against gravity, which requires more energy, said Weyand. Hence, a complicated mathematical formula that you can access here.

Findings were published November 12 in the science periodical Journal of Experimental Biology.

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