Vaginismus, sometimes called vaginism, is the physical or psychological condition that affects a woman's ability to engage in any form of vaginal penetration, including sexual intercourse, manual penetration, insertion of tampons or menstrual cups, and the penetration involved in gynecological examinations (pap tests). This is presumed to be the result of an involuntary vaginal muscle spasm, which makes any kind of vaginal penetration painful or impossible. While there is a lack of evidence to definitively identify which muscle is responsible for the spasm, the pubococcygeus muscle, sometimes referred to as the "PC muscle", is most often suggested. Other muscles such as the levator ani, bulbocavernosus, circumvaginal, and perivaginal muscles have also been suggested.