From the NEW YORK TIMES
The Claim: Running Outdoors Burns More Calories
By ANAHAD O’CONNOR
Published: May 6, 2008
Pavement or Treadmill? Most avid runners have a strong preference for one or the other, but how do the two differ in producing results?
According to several studies, the answer is not so simple. Researchers have found in general that while outdoor running tends to promote a more intense exercise, running on a treadmill helps reduce the likelihood of injury, and thus may allow some people to run longer and farther.