Uddiyana bandha is the abdominal lock, one of the three internal locks or bandha

Bandha

Bandha is a Sanskrit term for "binding, bond, arrest, capturing, putting together" etc.It may refer to:*a technical term in Hatha Yoga, see Bandha *one of the tattvas in Jainism, see Bandha -See also:...

s described and employed in hatha yoga

Hatha yoga

Hatha yoga , also called hatha vidya , is a system of yoga introduced by Yogi Swatmarama, a Hindu sage of 15th century India, and compiler of the Hatha Yoga Pradipika....

. It involves, after having exhale all the air out, pulling the abdomen in and up under the rib cage by means of taking a false inhale while holding the breath (performing the same action of an inhale without actually pulling any air into the body) and then release the abdomen after a pause. Then, the whole cycle of false inhale, pause and release is repeated many times before letting the air into the lungs, resuming normal breath.
http://www.ilsestotibetano.it

Uddiyana Bandha by Dr.