This is an exercise, which trains the abs the way they are naturally used in every day life- as a stabilizing muscle.
Step 1: Like the Butt-up start in the push up position but with your elbow on the floor, supporting your weight on your forearms, keep your back straight and slightly above the hips, do not shrug your shoulders or arch your back.
Step 2: Hold this position for as long as you can.
Beginners: You should try to hold the position for at-least 45 seconds and increase the time gradually.
Experienced readers:Aim for a few minutes at a time, you can lift up one leg off the floor behind you with the knee straight to make it more challenging.