Adjust seat so pad rests comfortably on chest. Sit in good body alignment (abs tight, chest up, back straight). Grip bars or place arms at side. Lock feet under foot pads. In a controlled motion, keeping neck straight, curl upper body forward and down. Contract abdominals fully without compromising form. While maintaining the controlled motion, return to starting position. Do not allow muscle to relax before next repetition.
Here are a few suggested alternative exercises:Ab CrunchAb Crunch ObliquesBall CrunchDouble CrunchDumbbell Side BendsKneeling Cable CrunchKneeling Oblique TwistLateral Bend with Barbell