7. Fitball Advanced Reverse Crunch (not for those with back injuries)
Starting Position:
Lie on the ball with your upper back supported by the ball and hands above your head, holding onto a solid support, such as the support for a cable machine in the gym or the footboard of your bed at home. Bring your legs up until your hips and knees are each at a 90-degree angle. Movement:
Contracting the abdominals, curl your legs up toward your body. Slowly return to the starting position.
Key Points:
Exhale while lifting your legs. Inhale while returning to the starting position. Lower your legs only as far as you can while maintaining control. 
8. Lying Bent Knee Leg Lift (care needed for those with back injuries)
Starting Position:
Lie on your back with your feet on the floor and knees slightly bent. Place your hands under your head for comfort, not support. Movement:
Contracting your lower abdominal muscles, draw your knees toward your chest until they form a 90-degree angle with the floor. Slowly return to the starting position, stopping just short of the feet touching the floor.
Key Points:
Exhale while lifting your legs. Inhale while returning to the starting position. Your back should remain comfortably against the floor during the entire motion. Avoid this exercise if you have any back conditions. Eliminate this exercise if you experience any discomfort.
