This move comes from Ken Weichert, master fitness trainer for the U.S. Army and creator of an exclusive boot camp class for Crunch Fitness clubs nationwide. If you're sick of the same old crunches, this move is a great way to switch it up and target the obliques--the muscles on the sides of your abdomen.
How to do it: Begin by lying on your back on a mat with your legs and arms straight. Keep your legs together, and lift your heels toward the ceiling until your feet are directly above your hips. Tighten the abs, and reach over outside the right thigh with both the left and right arms. Make sure your arms stay off the ground and return to center. Next, reach over outside the left thigh with both arms; repeating the move.
Aim to do as many reps as you can in 30 seconds. To continue working on your abs, you can transition into another of Ken's moves, the flutter kick.