Why can you not do a stomach vacuum? Mistake number one: You try to suck in your belly and engage your abs. With tight rectus abdominis (your sixpack abs) it’s nearly impossible to do the stomach vacuum. Instead, you need to relax these muscles. Lay on the ground and release the abs, you can even massage them a bit. Then you gently exhale, and open the ribcage without air, without pulling the belly in. Do you want to learn it correctly now, free to lift your pelvic floor, reduce incontinence and