You can do this exercise either at the gym or at home. If you prefer to do them at home, you may be more comfortable performing this exercise on a yoga mat, towel or any other soft surface you can put between you and the floor. You'll also need a water bottle, weight or medicine ball to use while you do this exercise.c 

This exercise works your rectus abdominis muscles, which are the major muscle group in your core and the muscles responsible for the six-pack look.c 

1. Start in a seated position then lean back slightly and lift your feet. You should be balancing on your hip bones.
2. Grabbing your water bottle, weight or medicine ball with both hands, start on the right side and transfer your chosen object through your legs from side to side.
3. Make sure that your back stays relatively straight throughout the whole exercise. The only movement should come from the slight raising and lowering of your legs and your arms passing the weight through.
4. Keep a space between your chin and chest. If you don't feel the burn in your ab muscles right away, adjust the angle your leaning at until you do.