The Two Uddiyanas
It is important to distinguish Bettina’s Uddiyana, which lifts the respiratory diaphragm way up into the ribcage, from the other Uddiyana, which is a miniature version of Bettina’s.
Bettina’s Uddiyana is sometimes referred to as Uddiyana Bandha Kriya. It is one of the six kriyas, and involves retracting the entire abdomen (lower and upper belly) while on an exhale retention. We do not do this Uddiyana with asana.
The mini version takes place entirely below the navel during the motion of inhaling and does not lift the diaphragm. More specifically, after exhaling and toning the pelvic floor, you inhale while slightly drawing back your abdomen just in front of the sacrum, immediately above the pelvic floor. Mini Uddiyana, which you would normally call into action with Mula Bandha, causes the psoas muscles to relax. (Mini Uddiyana is what we want during asana.)