Try This!: Sit-ups that use momentum and get heart rate racing

Bob Harper of 'The Biggest Loser' suggests new sit-ups that use momentum to get your heart rate up

Take everything you learned about the traditional sit-up and toss it out the window. Bob Harper, best known for his work on NBC's "The Biggest Loser," would like to introduce you to a new way of doing sit-ups that uses momentum to get the job done. It will also send your heart rate soaring.

What it does

This movement tightens the core and flattens the abs, especially the lower abs, but takes the legs and hip flexors out of the way, literally, so you are forced to use your abs to get you off the ground. The move also tones the lower back and inner thighs. Many of us have been taught to avoid using momentum, as it can rob an exercise of its value. Not in this case. Use momentum all you want, Harper says. There's nothing that can make this exercise any easier. And, in fact, the momentum just helps add to the calorie burn.

What to do

Sit on the floor, the soles of your feet together, knees out to the sides. Lie down and reach your hands over your head. Begin the movement by engaging your abs and reaching up and forward. Ideally, your shoulders will come past your knees, hands past your feet (or as far as your flexibility allows.) Reverse the movement. If you're like most of us, you'll struggle and wobble, and your feet may come apart. No matter. Collect yourself and resume.

How much

Harper favors Tabata training, which he calls the hardest workout you can do in the least amount of time. It looks like this: 20 seconds of movement followed by 10 seconds of rest, for eight rounds. So: As many sit-ups as you can do for 20 seconds, rest for 10 and then get back to it, for eight rounds in all.

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