All but one are true regarding levator ani musle
The origin of levator muscle is fixed because muscle arises anteriorly from bone (pubis) and is inserted into anococcygeal raphe or coccyx, both of which are moveable.
Levator ani muscles constitute pelvic diaphragm
Contraction of levator pulls rectum and vagina towards symphysis pubis
Insertion of the muscle is fixed
Internal rotation of presenting part during delivery is assisted by levator muscles