You must keep the sunken stomach 10 to 15 seconds, then breathe gently and continue sinking stomach.
After breathe a little, you should not relax the stomach, breathing the need to keep another 10 to 15 seconds and again you must sink the stomach.
Stomach muscles should always tense. If you were hard to keep breathing, you can take short inhalations.
Exhale, relax the stomach and breathe normally.Then you must again release the air from the lungs and you should sink much as you can stomach.
Stretching the muscles of the stomach and not breathing push the stomach up.
This practice will achieve strengthen stomach muscles in just three weeks and you also get to reduce the size of your waist.
After this exercise, you managed to get a better look and stomach much flatter.