Lie on the floor and position your legs over a flat bench at a 90 degree angle. Place your hands behind your head and keep your lower back rounded and flat against the floor. Curl yourself up and rotate your body until your elbow is touching the opposite knee. Pause briefly at the top and then lower yourself back to the starting position. Repeat the same motion using the other elbow and alternate back and forth until you have completed your set.
Do not pull on the back of your head with your hands as you perform this movement. Also make sure to not lift your entire body off of the floor but instead focus on working only your abs and obliques. You should aim to keep the tension on your mid section the entire time by not resting at any point throughout the exercise.