Sit with your buttocks at the top angle of the decline bench (angled at 15-30 degrees) and position your feet under the ankle rolls. Slowly lower your torso backwards onto the bench. Put your hands either at your ears or behind your head. This is the starting position.
Commence the movement by contracting your abdominals and crunching across to the left side of your body. Touch your left elbow on your right knee as you squeeze the abs and exhale.
When you feel that real squeeze across your abs, reverse the movement by straightening your torso and lowering it back to to the starting position, inhaling as you do.
Perform the same movement on the opposite side and then continue to alternate.