Grasp a secure object behind you to steady yourself while supporting your upper back on a stability ball.  Leg raises, knee raises and reverse crunches can be done this way.
Having to balance on a stability ball forces the abs to work very hard to stabilize the body during all movements. A dumbbell bands or a cable pulley attachment can be used to add resistance.

Roman Chair Situps

Securely place your feet so that in a straight-legged position, your waist extends past the pad.  While maintaining a pelvic tilt, extend your body back until you are in a horizontal position. Return to an upright position by curling your body up.  Do not extend past a horizontal position as this may place undesired stress on the back.  Weight can be held or bands used to increase the resistance.  Also, holding the extended position for up to 10 sec. can also increase the intensity.

Barbell Ab Rollout

This exercise can be done with a barbell or ab wheel. The elbows are to be locked and kept in a vertical line with the shoulders.  Many ab wheel commercials show the user with their arms extended out but it is felt that this puts unnecessary stress on the
shoulders and lower back. Keep the body locked in a straight position with no back “sag” when in the bottom position. All movement in this exercise is initiated by the hips, not the arms/lats. The emphasis should be on raising the butt as high as possible in a “piking” motion.

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