Hook your feet under the pads of a decline bench and lie back with your knees bent. Curl your shoulders and upper back off the bench, reaching your ribs toward your hips, then lower back down under control. The decline angle stretches your abs further at the bottom than a flat crunch does, so you'll feel more of the movement on the way down. Keep your chin off your chest and your lower back relaxed into the bench rather than yanking your neck to start the curl. Your hip flexors will want to take over on a steep angle — focus on shortening the distance between your ribs and pelvis rather than folding at the hips.