Crossed Abs

To do crossed abs you have to lie on the ground (use a towel or another fluffy thing to put under your back) with your legs doing two 90º angles (one between your upper part of the legs and the lower part of the legs and another one between your upper part of the legs and your upper body), and then you have to raise your back, your head and your elbows in a single movement, and they are called crossed abs because when you rise your body, your right elbow has to touch your left knee and your left elbow has to touch your right knee alternately.

Details: Always keep the 90º angles. Do the most repetitions you can. Always raise your head more than your hands to be a more effective exercise.