The Crunch is one of the most common abdominal exercises. It primarily works the rectus abdominis, which extends up the middle of your abdomen.
  1. Lie on your back.
  2. Place your hands behind or beside your head.
  3. Keeping your feet flat on the ground, bend your knees at a 90-degree angle.
  4. Using your abdominal muscles, pull your upper body up until your shoulder blades are a few inches from the ground.
  5. Slowly return to your original position.