Sit on a decline bench and hook your legs securely under the pads.
Lean your body back at roughly a 45 degree angle and extend your arms directly out in front of you perpendicular to your torso, clasping your hands together.
While keeping your core tight, twist your torso to one side until your arms are parallel to the floor, and then rotate back to the opposite side in the same way, repeating for desired number of reps.