I remember back in high school gym class when girls sometimes sat out of virgorous activity, and definitely out of swimming, because it was “that time of the month.” I can already feel the feminist sense of affront rising as I think back on it. The very idea of relegating girls to the side lines because they were menstruating. Please.

Through my teens and twenties, taking a time-out because of my period made absolutely no sense to me. Though I did suffer from body ache, tiredness, and unpredictable moods prior to my period each month (yes, I believe in PMS and you can’t convince me otherwise), the minute I started to menstruate I enjoyed a surge of energy (and optimism) that stayed with me through the duration of my period and on into the better part of the month!

So I experienced much resistance, annoyance, and feminist skepticism when, upon attending my first class of Iyengar yoga in January 2000, the instructor said that women should let her know if ever we were menstruating because there was a “special practice” we should follow. The practice involves mostly restorative poses and completely avoids inversions (such as headstand, shoulder stand, elbow balance, or full- arm balance) and vigorous standing poses. I’ve also been told that twists are to be avoided.

Geeta Iyengar, daughter BKS Iyengar (founder of the Iyengar method), writes: “During menstruation, if one does inversions the blood flow will be arrested. Those who tried to do it out of enthusiasm or callousness will have noticed that the flow stops abruptly. This is certainly not good for health since it may lead to fibroids, cysts, endemetriosis, and cancer, damaging the system.”

Apparently, it’s not clear that these medical risks of “arresting the blood flow” are borne out by the research. Dr. Timothy McCall, writing for The Yoga Journal, says that “One study, however, found that retrograde menstruation naturally occurs in 90 percent of women, most of whom never develop endemetriosis. So we do not know for sure if inversions increase retrograde flow or whether the backward flow increases the risk of endemetriosis.”

And of course, yoga comes out of a tradition that pre-dates the modern medical model. It is not surprising, therefore, that some detractors of any special practices around menstruation believe they are more linked to beliefs about women’s impurity at that time of their cycle. Many religious traditions hold to the view that women ought to be segregated while menstruating–e.g. the red tent. Assuming most feminists reject the view that menstruating women are impure, this reason for practicing alone instead of with the class won’t go over particularly well with them.

In addition to giving medical explanations, Geeta appeals to the ayurvedic medical model, maintaining that menstrual blood is like any bodily waste–urine, feces, phlegm, mucus–and that all wastes ought to be excreted. The process ought not be hindered because these forms of waste, if retained, “invite diseases.”

Iyengar yoga has special practices for all sorts of things from stress and depression to head aches, back pain, and respiratory issues. Circulation issues? There are multiple sequences of asanas for that. Lower backache? They’ve got it covered. Stress, depression, headaches, mental fatigue, insomnia? That is one of the things I really admire and respect about this form of yoga. The teachers are well-trained enough to be able to modify poses to respond to the special needs of students.

Of course, the ayurvedic tradition is not the same as the Western medical model. The medical explanations for some of the recommendations might seem foreign to those of us raised in the Western medical tradition. But the sequences of asanas do offer some relief for acute issues and, practiced over time, can alleviate (if not cure) some more chronic conditions.

But back to the monthly. For every one of us who breeze through it, there’s another who suffers with major cramps and heavy flow, headaches, back aches, what have you.

And it doesn’t always stay the same from that first shocking experience to menopause. From my easy time of it for the first twenty-some years, things started to change for the worse in my mid-thirties. I felt more tired. On occasion, I might experience cramps. And just generally, life can get stressful. And that’s around the time I first began to practice yoga.

While I remain skeptical about the medical explanation for refraining from inversions, I have actually come to enjoy the sequence of poses contained in the menstrual practice. The practice is inward and restful yet energizing at the same time. Some of the poses do wonders for the particular kind of lower back pain I get with my period. And I kind of like that at the studio we are comfortable enough with ourselves and our bodies to say when we need the special practice.

In our class, lots of us opt for this “red tent” when we have our period. I also know that on occasion some of the men, feeling especially tired or exhausted sometimes, have expressed the wish that they could do “the menstrual practice.” I agree that they should have the option of doing it or something like it.

We all have energy cycles. Not everyone is always up for a vigorous class of standing poses and 5-minutes each of headstand and shoulder stand. Sometimes a quieter, supported sequence is the right choice.

And it’s not the right choice for everyone. My younger self, with her increased energy and light flow, would have balked at the idea of taking a time-out for something as inconsequential as menstruation. And regardless of what Geeta says, I do think she should be permitted to make that choice without risk of being called “callous.”

As an experienced student, I could stay home those days and do the practice there. But I usually will attend class anyway for a few reasons. First, the energy of the rest of the class, even if I’m not doing what they are doing, feels good. Second, depending on what’s being taught, sometimes it’s possible to do what the rest of the class is doing, with minor modifications (such as substituting other postures for the inversions). Third, the studio has more equipment, making it easier because all the props are on hand. And finally, if I do have a question about one of the asanas in the sequence, my instructor can help me out. I have learned a lot from my teacher over years of doing the special practice in class from time to time.

In my case, I no longer feel offended at practicing off to the side when I am menstruating. It’s not the same as being side-lined from gym class and forced to do homework. We are given a full alternative practice to do instead. It feels good. It’s a good option and I take it. But it does need to be optional, not mandatory.