How to burn more calories while you walk

Walking is a great way to burn extra calories, but new research suggests you might gain even more benefit if you vary your speed as you stroll.

The new research, from Ohio State University, found that changing your pace could burn up to 20 percent more calories than maintaining a steady stride.

"Most of the existing literature has been on constant-speed walking. This study is a big missing piece," study co-author Manoj Srinivasan, a professor of mechanical and aerospace engineering, said in a university news release.

"Measuring the metabolic cost of changing speeds is very important, because people don't live their lives on treadmills and do not walk at constant speeds. We found that changing speeds can increase the [caloric] cost of walking substantially," Srinivasan explained.

People may also be underestimating the number of calories they burn while walking in daily life or playing sports, the study authors said. The researchers estimated that starting and stopping may account for up to 8 percent of the energy used during normal daily walking. This caloric cost is often not included in calorie-burning estimations, Srinivasan's group said.

Study lead author Nidhi Seethapathi, added that "walking at any speed costs some energy, but when you're changing the speed, you're pressing the gas pedal, so to speak. Changing the kinetic energy of the person requires more work from the legs and that process certainly burns more energy." Seethapathi is a doctoral fellow in mechanical engineering at the university.

For the study, the researchers measured the metabolic cost, or the number of calories people burned, when they changed their walking speeds. In order to do this they had volunteers change their pace while walking on a treadmill. Although the treadmill remained at a constant speed, the participants alternated between quick steps -- to stay at the front of the treadmill belt -- and slower steps, which kept them at the back.

The study also showed that people tend to walk more slowly when covering short distances, but they increase their pace if they have to walk farther. The researchers said this could be useful information for physical therapists, because they often measure their patients' progress by the amount of time it takes them to walk a certain distance.

"What we've shown is the distance over which you make them walk matters," said Seethapathi. "You'll get different walking speeds for different distances. Some people have been measuring these speeds with relatively short distances, which our results suggest, might be systematically underestimating progress."

The bottom line, according to the researchers: If you want a bigger calorie burn, walk in a way that feels unnatural to you.

"Just do weird things," said Srinivasan, who also leads the Movement Lab at Ohio State. "Walk with a backpack, walk with weights on your legs. Walk for a while, then stop and repeat that. Walk in a curve as opposed to a straight line."

The findings were published in the September issue of the journal Biology Letters.