Bonus: it especially hits the core.
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Regardless of which team you root for on The Voice, there's one thing we can all agree on: We'd turn our chairs around to glimpse Shakira's smokin' hot body.

One move that helps keep the 37-year-old mom (and host of seasons 4 and 6) in stage-ready shape is the Jackknife with a Twist. "It challenges the body from every angle and especially hits the core," says Anna Kaiser, founder of AKT inMotion in New York City, who trains the pop star.

Here's how to do it: Start in a plank position (palms under shoulders, back flat, and legs extended behind you) with your shins on top of a stability ball (A). Press down on the ball with your shins as you lift your hips toward ceiling, then bend your knees and bring them in toward your left shoulder while twisting your midsection (B). Extend your legs and return to a plank. Do 30 reps, alternating sides. Do 3 sets 3 to 5 times a week.