Lie face up on slant board, knees bent with feet under pads. Cross arms over chest. In a controlled motion, keeping neck straight, curl upper body up, moving diagonally to the left or right. Contract obliques 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 Crunch ObliquesBall Crunch TraditionalDumbbell Side BendsLateral Bend with Barbell