Tag, to describe the events associated with muscle tension when pushing an object out of the lower body. may be accompanied by “anal_tugging” or “vaginal_tugging”.

not to be confused with “anal_wink”, which is the opposite of the tag “pelvic_muscles_push”.

with anal-wink, the muscles contract to accompany the closing of the opening.
With pelvic-muscles-push, the muscles work to push out, creating exactly the opposite effect

the perfect example is https://e621.net/posts/5130532?q