To be most effective, abdominal exercises should include focus on working the following muscles:
Pelvic Tilt—Lie on floor with knees bent, feet parallel and arms to the side
Trunk Curl—Lie on floor with knees bent and arms crossed on the chest
To be effective, motion should raise the chest, rather than the head or neck, and only be only a slight lift. Rising too far, to a sitting position, works leg muscles not the abdominals.
Water Exercise/Leg Lifts—Stand in the pool next to the side wall with one hand on the edge
Exercise Ball/Sit-ups—Sit on the exercise ball with back in neutral position, feet flat on floor and arms straight overhead