Answered by on Monday, June 1, 2009
Just because you're not blowing by scenery doesn't mean you're working less despite what those outdoor running snobs say. "At a one percent incline, you'll expend the same amount of energy on a treadmill that you would on the ground," says Jay T. Kearney, Ph.D., senior sports physiologist at the U.S. Olympic Training Center in Colorado Springs, Colorado. Only when you add in a change of terrain or a strong wind, do you tip the scales in favor of running al fresco. "If the surface is uneven, if you're hopping over obstacles like rocks or running against a strong wind, you're increasing your energy expenditure," explains Elsworth Buskirk, Ph.D., a physiology professor at Penn State University. (Wind resistance really only becomes a factor if you are running at 10 miles per hour or faster.) "But with nothing to impede the running, the caloric results inside and out are just about equal."