WORKOUT MATRIX A key to success is picking an activity you like that will fit into your schedule. If you can be adaptable and mix several exercises so much the better. Below, an array of choices that vary in calories burned and benefits, including weight-bearing (you carry your own weight, thereby strengthening bones) and resistance (you push or pull against weights, increasing muscle and bone strength). They're in order of most calories burned to least. Whatever your choice, you'll get more bang for your buck if you raise the intensity--run faster, for example, or lift weight. Note that any of these activities beats watching TV (45 calories per half-hour) or sleeping (41). Activity Calories Per 30 Minutes Benefits   Running 6 mph 318 455 •   •   • Stair climber 286 409 • • •   • Step aerobics 270 386 • • •   • Outdoor biking 254 364 • •     • Tennis (singles) 254 364 •   • • • Swimming (laps) 254 364 • •   • • Rowing machine 223 318 • •   • • Stationary bike 223 318 • •     • Hiking, no pack 191 273 •   •   • Jazzercise 191 273 • • • • • Golf (walking, carrying clubs) 143 205 •   • • • Walking 3.5 mph 121 173 •   •   • Walking 2.5 mph 95 136 •   •   • Weight lifting 95 136   • • • • Yoga 80 114   •   • •