I was doing some reading on the HOME page here and found this...all of you probably know this already...but I didn't and was very happy to see that WALKING is better for your metabolism.
Walking vs. Running. According to Dr. Dean Ornish, "All things being equal, you will burn more calories by running an hour than walking an hour. It is true that walking a mile will burn more calories than running a mile -- although it takes longer to do so. When you run a mile, you're burning mostly sugar, or carbohydrates, which is how your body gives you fast energy in bursts. When you walk a mile, it gives your metabolism time to switch from burning carbohydrates to burning fat. The risk of injury -- whether shin splints or knee injuries or back pain -- is directly proportional to the intensity of exercise. So is the risk of sudden cardiac death. Walking gives you most of the health benefits of more intensive exercise while minimizing these risks. More is better, but only if you do it consistently. So, if you want to burn the maximum amount of calories, then run for an hour rather than walking for an hour. But do it consistently; otherwise, you're better off walking. "