Chasing Stronger, Defined Abs?

ABS - Knee Raises

Take position on the parallel bars of a dip machine. Your back is against the pad and your body hangs down freely. This is the starting position.
Commence the movement by contracting your abdominals and breathing out as you lift your legs from their straightened position up toward the torso. You may either bend the legs at the knee or keep the legs relatively straight as you pull them up to a point where they are parallel to the floor.
At the top of the movement, squeeze the abs hard before slowly lowering the legs back to the starting position, inhaling as you do.