The crunch is a favorite movement of mine. It reminds me of the Physical Fitness Test of my Marine Corps days, during which we were required to perform 100 crunches in two minutes to establish a perfect score. I’m going to hold you to the same standard as a United States Marine and expect the same level of performance. The crunch will engage your abdominal muscles and prepare them for the more advanced double crunches in today’s workout. Lie with your back flat on the ground, knees bent. Fold your arms over your chest, grab your biceps, and sit up, bringing your chest and arms to your thighs.