We all want a toned, flat stomach. No surprise there. But since many women are still relying on crunches to get it, we want to make one thing clear: Crunching is not the most effective abs workout. "Crunches work only the muscles on the front and sides of your abdomen, but it's important to target all the muscles of the core to get more defined abs—including lower back, hips, and upper thighs," says Lou Schuler, co-author of The New Rules of Lifting for Abs.

To lose belly fat and uncover amazing abs, Schuler recommends a series of core stabilization exercises based on a training program devised by co-author and personal trainer Alwyn Cosgrove. "Core exercises like the plank help train muscles to stabilize the spine and pelvis so you can avoid back pain and improve posture, Schuler says. "They also burn more calories than crunches because they work more muscles."

The Best Abs Exercises: Side Plank

Why it works: This abs exercise is more challenging than a traditional plank because you're supporting your entire body weight on two points of contact instead of four. As a result, you must work your core harder to stay stabilized.

How to do it:
A. Lie on your left side with your elbow directly beneath your shoulder and legs stacked. Place your right hand on your left shoulder or on your right hip.

B. Brace your abs and lift your hips off the floor until you're balancing on your forearm and feet so that your body forms a diagonal line. Hold for 30 to 45 seconds. If you can’t hold that long, stay up as long as you can and then repeat until you’ve held for 30 seconds total. Switch sides and repeat.

More great stabilization moves: The standard plank and the anti-rotation hold.