Uddiyana Bandha

Technique

Stand with your back against a wall and your feet a few inches away from the wall, hip-width apart. Curl your torso so that your back is curved (as it is in Cat Pose) and bend your knees so that you can rest your hands on the tops of your thighs for support. Your tailbone is still touching the wall.
In this position, take a deep inhale through your nose and exhale quickly and powerfully. Exhale all the way until the very end of your breath—this stretches your diagram to its most expanded position.
At the end of your exhale, pull your belly in as if you are trying to bring your navel to touch your spine. Once you have pulled in as much as you can, begin to pull up like you are trying to keep your navel as far back as possible while also pulling it up into your rib cage.
Keep your belly like this while taking no further breaths—this is called breath retention.
When you can no longer hold your breath, bring your belly back down and out to its natural, relaxed position, gently and with control. Only after doing this should you inhale—again, do this gently and with control, trying not to gasp.

Strengthens the abdominal muscles and diaphragm
Massages abdominal viscera, the solar plexus, and the heart and lungs
Increases gastric fire; improves digestion, assimilation, and elimination; and purifies the digestive tract of toxins
Stimulates blood circulation in the abdomen and blood flow to the brain
Stimulates and lifts the energy of the lower belly (apana vayu), to unite it with the energies localized in the navel (samana vayu) and heart (prana vayu)^[1]