Running isn't really good for your body; it's really hard on your joints, especially if you run on concrete or asphalt (which just about everything in a metro area is covered with these days).
The big problem with running is the lousy shoes that all but force you to use a heel strike. It's the heel strike that trashes your knees and hips, and leads to fatigue very quickly. Take the shoes off and run barefoot, landing flat-footed or on the balls of your feet. At first you'll discover muscles you haven't been using, then you'll find yourself wondering why you wasted all that money on expensive running shoes.