Image by the amazing Gemma Correll.

This blog post of an exclusive excerpt from my new book, The Physiology of Yoga.

There is widespread belief among yoga teachers and practitioners that inversions including Shoulder Stand (Salamba Sarvangasana) and Headstand (Sirsasana) should not be practiced during menstruation. On an energetic level, menstruation is intrinsically linked with apana (the contracting, downward moving force), and therefore it is believed that inverting the body will reverse the direction of this force. Another part of the reasoning comes from the retrograde menstruation theory, which was promoted by Doctor John Sampson. In 1927, Sampson suggested that menstrual tissue can flow backward through the fallopian tubes and deposit on the pelvic organs, causing endometriosis (the abnormal growth of endometrial cells outside the uterus). However, there is little evidence that endometrial cells behave in this way. More recently, researchers have found that up to 90 percent of women have retrograde flow anyway (Sasson and Taylor 2008), but since only 10 percent of women of reproductive age develop endometriosis (Olive and Schwartz 1993), it has been concluded that the cause of endometriosis is much more complicated than this. Sampson’s theory has also been disputed because it cannot explain the occasional occurrence of endometriosis in prepubertal girls, newborns, women who have had a hysterectomy (surgical removal of the uterus), and men who have received long-term hormonal treatment. Writing about female astronauts in space, Wotring (2012) reported that the myth that zero gravity would cause retrograde menstrual flow, causing blood to accumulate in the abdomen and cause infections, has been shown to be baseless. It is understood that uterine contractions, rather than one’s orientation to the ground, are responsible for the flow of menstrual blood (Bulletti et al. 2000).

It is also important to recognise that the uterus is inverted many times throughout a typical yoga practice—for example, in Standing Forward Fold (Uttanasana), Downward Facing Dog (Adho Mukha Svanasana), Bridge Pose (Setu Bandha Sarvangasana), and others—yet these poses are rarely classed as inversions. Thus, there is little logic to the idea that inverting the uterus in these poses is appropriate but not appropriate during a Shoulder Stand. 

There is rarely, if ever, a single directive that works for every student. It is important for yoga teachers to give options and permission to students to tune into to what feels right for them in each moment.

References:

Bulletti, C., D. de Ziegler, V. Polli, L. Diotallevi, E. Del Ferro, and C. Flamigni. 2000. “Uterine Contractility During the Menstrual Cycle.” Human Reproduction 15 (S1): 81-89.

Olive, D., and L. Schwartz. 1993. “Endometriosis.” New England Journal of Medicine 328:1759-1769.

Sampson, J. 1927. “Peritoneal Endometriosis Due to the Menstrual Dissemination of Endometrial Tissue Into the Peritoneal Cavity.” American Journal of Obstetrics and Gynecology 14:422-469.

Sasson, I., and H. Taylor. 2008. “Stem Cells and the Pathogenesis of Endometriosis.” Annals of the New York Academy of Sciences 1127:106-115.

Wotring, V. 2012. Space Pharmacology. New York: Springer-Verlag.

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