Abdominal crunches primarily work on abdominal muscles and it is widely used as general body workout and abdominal muscles strengthening. How to Do Abdominal Crunches? 1. Lie down on the floor on your back and bend your knees, placing your hands behind your head or across your chest. Some people find that crossing the arms over the chest helps them avoid pulling on the neck. 2. If you are putting your hands behind your head, your fingers should gently cradle your head. The idea is to support your neck without taking away from the work of your abs. 3. Pull your belly button towards your spine in preparation for the movement. 4. Slowly contract your abdominals, bringing your shoulder blades about one or two inches off the floor. 5. Exhale as you come up and keep your neck straight, chin up. Imagine you're holding a tennis ball under your chin. That's about the angle you want to keep the chin the entire time. 6. Slowly lower back down. 7. Repetatio...