Runners have long debated treadmill versus street training. Purists often prefer the outdoors to air conditioned gyms, deeming treadmill running as inferior, while leisurely joggers enjoy Keeping Up with the Kardashians during their daily cardio. A new European study supports those who pound the pavement, showing that you would need to run 15 percent faster on the treadmill to get the same effect as you would outside.

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In the very small study, 15 college-aged males ran at a set speed for 30 seconds before taking a 30-second break. This was performed for 15 rounds and done outside, on a treadmill set at 1 percent incline, and a treadmill set at 1 percent incline plus a 15 percent increase in speed. The 1 percent incline was used to account for wind velocity as a previous study indicated this tweak made treadmill jogging comparable to outdoor running for speeds between 6.7 and 11.1 miles per hour, reports Real Clear Science.

Running outdoors has many benefits, including delivering your daily dose of vitamin D. Pixabay

“The present study demonstrates that an 15 percent increase in running velocity during a high intermittent intensity treadmill training session is the optimal solution to reach the same physiological responses than an outdoor training session,” the study authors write in the paper, showing that you need to run 15 percent faster on the treadmill to get the same effect.

Runner’s World says there are several reasons that treadmill running is less strenuous. The belt on the machine actually offers assistance by propelling you forward, which makes you move faster, so chances are your pace won’t match your road speed. The belt also tends to "give" more than hard cement or concrete, so your muscles, tendons and ligaments don’t endure as much conditioning. Plus, elements like hills and wind speed add resistance to your training.

Because training outside is more challenging, it’s ideal for those looking to drop a few pounds. "Outdoors, you are changing surfaces constantly, fighting the wind, and making quick and sudden starts and stops, which all lead to increased caloric burn," says physical therapist Michael Silverman, director of rehabilitation and wellness at Northern Westchester Hospital, in Shape magazine.

While some may prefer to avoid running on hard surfaces as it is tough on joints, Dr. Irene Davis, professor of physical medicine and rehabilitation at Harvard Medical School, tells Time that using the same running motion repeatedly (as is often performed on a treadmill) can actually cause injuries.

“Most running injuries are overloading injuries that involve muscle, cartilage, bone or tendons wearing down over time,” Davis says. She theorizes the more your patterns change, like when turning the corner or huffing it up hills, the less you’ll overburden the same muscles and tendons, reducing injuries.

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Running obviously comes with risks, but the best way to prevent injuries is by warming up with a quick walk, not attempting to go from couch potato to marathoner overnight and landing on the middle of your foot.

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