ab exercises that aren't crunches

Photo: Courtesy of Michele Olson

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Plank with Arm and Leg Raise
Why do it: This advanced version of the classic "bird dog" is another terrific move for those deep abdominal muscles, which, Olson says, are practically neglected by crunches. And because this move strengthens the support muscles for your back, it can help improve your posture.

Starting position: On all fours, align your knees under your hips and your wrists under your shoulders.

How to do it: Raise your left arm in front of you to shoulder height and, at the same time, extend your right leg out behind you. Hold for 2 counts, then lower your left arm and right leg to the ground. Alternating sides, complete 15 to 20 reps total.