PUMP UP THE INCLINE LIKE JENNIFER ANISTON

Always-in-shape Jennifer Aniston doesn't stay slim by thinking about fitness — she works for it. A source told Us Weekly, "She's obsessed with staying fit and young." The 41-year-old has been shooting her latest movie Just Go With It, and in order to feel confident wearing a bikini on the set, she hits the Four Seasons gym every day for at least an hour, and sometimes more. A guest at the hotel said, "I saw her on the treadmill, and it was angled all the way up."

Jen knows how to maximize her time on the treadmill. Cranking the incline helps you burn more calories than if you keep the machine set to a zero grade. After a 30-minute workout at a 10-minute-per-mile pace, you'll burn 270 calories with no incline, 363 with a five percent incline, 420 with a 10 percent incline, and 482 with a 15 percent incline (crazy steep, I know). Not only will you burn an extra 100 calories or more, but the steep slope also helps tone your tush, thighs, and calves, problem areas for many women. It'll also build strength and endurance, so when you run outside on flatter surfaces, you'll move faster and with more ease. The next time you're hitting the treadmill, add a little uphill action to your walking or running workout. Not a fan of the gym? Then opt for hills outside or go hiking.