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She has one of showbiz's most famous backsides -- so how does Beyoncé Knowles do it? If you ask her, it's a combination of a couple of things: Good genes, and lots of stairs. The 27-year-old singer recently told FemaleFirst that climbing her way up (literally) is how she tones her tush -- "After New Year I do stairs - they are the best thing for butt cheeks."

She might be on to something. According to Reader's Digest, climbing stairs for two minutes a day, five days a week, gives you the equivalent of a 20-minute walk in terms of how many calories you'll burn (100 to 140 to be precise). OK, that doesn't seem like much when it's stretched over a week, but it goes to show that a little bit every day can really add up. What about if you have more than two minutes to work out in a day? Try the stair climber at your gym -- 20 minutes of moderate climbing will burn around 200 calories. And if toning up isn't enough motivation, consider this -- recent studies found that climbing the stairs on a regular basis can actually save your life. Those who regularly elected to walk up rather than take the elevator were shown to have lower blood pressure, cholesterol and body fat.

Stairs not your thing? Don't worry -- there are plenty of other exercises that will give you a good derriere. But if you're looking for an easy, free way to burn a few extra calories, look no further than the door next to the elevator.