This exercise is used to build strength in your abs.
Begin by lying down on a decline bench with your legs securely set in the pads at the top of the bench. Lay back and firmly press your lower back into the bench. Next, place your hands either across your chest or place them on either side of your head. Begin the exercise by lifting your shoulders off of the bench using your abs. Continue to pull your body up until your torso is straight up or perpendicular to the floor. Next, slowly lower your body back to the bench. Repeat this movement until you have completed your set.
If you place your hands by your head, do not lock your fingers together and do not pull on your neck with your arms. This could cause a strained neck muscle; make sure to keep your abdominal muscles contracted throughout the entire range of motion.
You can hold a weight plate on your chest to increase the resistance on your abs; this will make the movement much more difficult.