The reverse crunch is used to target the lower portion of the abdominal region. This is a focus of many people that exercise.
Begin by lying flat on the floor with your arms extended to your sides; your palms should be flat on the floor. Press your lower back into the floor constantly throughout this exercise to keep the tension on your abs. Next, bring your knees to your torso until your legs form a 90 degree angle (your lower leg should be parallel to the floor). To begin the exercise, squeeze your abs and curl your hips off the floor; try to move your legs straight up. Squeeze your abs and hold your hips off the ground for a second. Then slowly lower your hips back to the floor and repeat until you have completed your set.
This exercise uses a very short range of motion so it is important to squeeze your abs the entire time and hold the contracted position at the top of this movement. Do not swing your legs, because you will not effectively train your abs.