Well the American Council of Exercise says that the crunch is the best way to go. In a study performed by the University of Wisconsin, La Crosse researchers placed electrodes on exerciser's abs and found that crunches activated both the rectus abdominis and external obliques-better than the front and side plank. The crunch also activated more muscles than the stability ball crunch, decline bench curl up or bicycle crunch….and put equipment like the Ab Roller and Perfect Sit Up to shame. Health experts say that strengthening your internal ab muscles are just as important---so be sure to work in a variety of abdominal exercises. The muscles work to form a corset to protect your spine and back from injury. Your abdominal muscles transfer energy between your upper and lower extremities to increase power and performance. So you better get to crunching!