Myostatic Crunch is one of the best exercises for your abs. You can perform this exercise even if you are complete beginner.
The reason that regular crunches don’t work is because in regular crunches you are not using Full Range Of Motion ( ROM ). The balance ball provides you with the room to stretch allowing you to move through the full ROM.
Lay down on the balance ball with your feet wide apart and firmly on the ground. Bend your body backwards and your hands overhead, almost touching the floor.
Using your abs slowly come up as if you were doing a crunch, but keep your back straight.
Now you will twist your body to one side. This counts as one rep. Return to starting position and do the same thing on the other side.
Perform 3 sets of 10 if you are a beginner. If you are more advanced, do 3 sets of 20.