The Question

How do periods affect strength training? Or birth control? I see a lot of people online referencing it online in an offhand way, but I’m not sure how seriously to take them. Then there are woo-woo people who say you should base all of your training AROUND your period, and yet more people who seem to be reacting to those people, almost overcorrecting, and say periods are nothing to worry about.

The last group of people seems the most up on the science, but I have to say, I do feel like I notice more tiredness when my period is coming. Is this real? Is this something I should do anything about? What about my birth control, should I change it? (I am on the pill). —Kathryne

The Answer

There I will be, peacefully warming up for my bench, the wind in my hair and specifically the song “Return of the Mack (Mark Morrison vs. Bad Royale)” in my heart. I come to my last warm-up single before I start my working sets, and it feels conspicuously difficult. I don’t think much of it, and load up the working weight I was set to attempt for five reps. I’ll do one, two, three reps, and the fourth becomes surprisingly grindy, with my elbows wandering every which way, but I get it all the way up. Convinced I’m just not staying tight enough, I lower the bar one more time to my chest, reverse it for inch or two, and then it drops to my chest. Lying there pinned under all of 110 pounds, I wonder to myself: Period? 

Human bodies are notoriously difficult to study. They are difficult to study even at rest, before we try to do anything with them. It becomes a layer more difficult when you want to study a particular effect on those bodies, like strength training. This is because everyone has different genetic abilities, and maybe more importantly, training backgrounds. 

It becomes another layer more difficult when you want to study that effect during a nonstandard, cyclical effect, like the way strength training is affected when hormones go up and down and around over the course of a month in many—but not all! and not all in the same way!—women's bodies. (It does not further help that until recently, scientists relied on self-reporting cycle start and cycle length to guess at people’s hormone levels and ovulation timing, which we now know is not as closely related to hormone levels as we previously thought. This makes a lot of older research not quite useless, but at least kind of questionable.1)

We would probably have way, way more science on this if not for the general subjugation of women, but!—it really is a difficult thing to tease out scientifically. While I think many women I know who lift would anecdotally report ranging period effects, studies frequently find nothing. Or at minimum, they conclude that training should not altered in response to menstruation cycles.

So in here, I will lay out what we know, sort of know, and don’t really know about periods, birth control, and strength training. This is a science based-summary, but given that dealing with periods can be a highly individual experience, I’m going to intersperse it with observations about my own cycle and how I respond to it in terms of training, if ever. And this might even be hard to believe, but non-period-havers might want to stick around, because the advice at the end will work for you too.