TVA (transverse abdominal) engagement can be abstract and tricky. Practicing TVA disengagement (let the contents of your abdomen fall towards the ground, as in the bottom picture) can sometimes help confused students identify its function, as they feel their organs and their spine lose this vital support, and then, having identified this heaviness, they're better able to find the gentle "drawing-up-the-belly-button" feeling that supports these organs (top pic). We just all have to be careful not to make the motion spinal, but keep it purely muscular. You'll feel it! Bonus points: initiate from pelvic floor.