Stairs are a powerful, practical and completely free way to shape up and slim down.

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As we told you last week, bootylicious superstar Beyonce uses the stairs to slim down, and we think you should too! Spending just two minutes climbing the stairs at work on weekdays will add up to the equivalent of taking a 20-minute walk each week, and while that's not going to get you in good enough shape to run a triathlon or anything, it's still a pretty good start. What's more, just a short bout of stair-climbing is enough to give you a much-needed energy boost once the 3 p.m. drowsiness sets in.

Already taking the stairs? Go faster, or try taking them two at a time. You could also try using the Stairmaster at your gym -- 20 minutes at a moderate pace will burn 200 calories.