Running is a trendy, economical and high-calorie-burning activity. But it's also one with a high injury rate and one that's not easy on the body. So is there any way for people with bad knees, high arches, osteoporosis, obesity or myriad other health issues to lace up and head out for a run? Seasoned exercisers who like brisk walks might enjoy adding a few running intervals to their workout. It's a great way to burn more calories while getting in a "test run." Try a half-hour workout, warming up with a brisk walk for 5 minutes, jogging 30 seconds, then walking until you feel recovered enough to pick up the pace again. Jog another 30 seconds and walk again. Do this until you reach the 25-minute mark, then cool down with walking only.