Source: http://greatist.com/move/long-slow-jog-or-short-fast-run?utm_source=rss&utm_medium=rss&utm_campaign=feed_http–greatistcom-
Sunny days (yes, even when it’s cold) call for outdoor workouts. And hitting the road for a run is one of our favorite ways to do our body some good while taking in some fresh air.
But whether you’re looking to maintain your fitness, build stamina, or simply enjoy the gorgeous weather, the question arises: Is it better for your body to take a leisurely, long jog, or is there a need for speed (even if that means cutting back on mileage)?
We went to the experts to find out which we should choose: a long, slow jog (i.e., five or six miles at a 10-minute-mile pace) or a shorter, faster run (i.e., two or three miles at a 7-minute-mile pace).
The Short Story 
While it does depend on what exactly your fitness goals are, we can all agree that getting more done is less time is generally better. In that way, the shorter, faster run wins out. (One caveat: If you’re new to running, don’t go all out. Start by alternating walking and running until you build up your pace and mileage.)
The important thing to remember here: You’ve got to push yourself to run at an actually high intensity. Experts dub running at a “comfortably hard pace,” or around the max speed you could run 10K, a tempo run. For tempo runs, aim to work at 85 to 90…