Running in Reverse - NYTimes.com This column appears in the Dec. 9 issue of The New York Times Magazine. Backward running, also known as reverse or retro running, is not as celebrated as barefoot running and will never be mistaken for the natural way to run. But a small body of science suggests that backward running enables people to avoid or recover from common injuries, burn extra calories, sharpen balance and, not least, mix up their daily routine. The technique is simple enough. Most of us have done it, at least in a modified, abbreviated form, and probably recently, perhaps hopping back from a curb as a bus went by or pushing away from the oven with a roasting pan in both hands. But training with backward running is different. Biomechanically, it is forward motion's doppelgänger. In a study published last year, biomechanics researchers at the University of Milan in Italy had a group of runners stride forward and backward at a steady pace along a track equipped with force sensors and cameras. They found that, as expected, the runners struck the ground near the back of their feet when going forward and rolled onto the front of their feet for takeoff. When they went backward though, they landed near the front of their feet and took off from the heels. They tended to lean slightly forward even when running backward. As a result, their muscles fired differently. In forward running, the muscles and tendons were pulled taut during landing and responded by coiling, a process that creates elastic energy (think rubber bands) that is then released during toe-off. When running backward, muscles and tendons were coiled during landing and stretched at takeoff. The backward runners' legs didn't benefit from stored elastic energy. In fact, the researchers found, running backward required nearly 30 percent more energy than running forward at the same speed. But backward running also produced far less hard pounding. What all of this means, says Giovanni Cavagna, a professor at the University of Milan who led the study, is that reverse running can potentially "improve forward running by allowing greater and safer training." It is a particularly attractive option for runners with bad knees. A 2012 study found that backward running causes far less impact to the front of the knees. It also burns more calories at a given pace. In a recent study, active female college students who replaced their exercise with jogging backward for 15 to 45 minutes three times a week for six weeks lost almost 2.5 percent of their body fat. And it aids in balance training - backward slow walking is sometimes used as a therapy for people with Parkinson's and is potentially useful for older people, whose balance has grown shaky. But it has drawbacks, Cavagna says - chiefly that you can't see where you're going. "It should be done on a track," he says, "or by a couple of runners, side by side," one facing forward. It should be implemented slowly too, because its unfamiliar motion can cause muscle fatigue. Intersperse a few minutes periodically during your regular routine, Cavagna says. Increase the time you spend backward as it feels comfortable. The good news for serious runners is that backward does not necessarily mean slow. The best recorded backward five-kilometer race time is 19:31, faster than most of us can hit the finish line with our best foot forward.