Is menstrual cycle training bogus?

Mar 5

“Women can use their monthly cycle to their advantage in sport.”

That’s a direct quote from a YouTube fitness guru with tens of thousands of followers. Their approach, in a nutshell: During one phase of the menstrual cycle, females should go heavy in the weight room. During another phase, they should take a more recovery-based approach.

Menstrual cycle-based training is no longer a fringe concept. Entire companies have popped up to help female athletes periodize with their periods.

The theory goes something like this…

Natural hormonal fluctuations—such as the rise and fall of estrogen and progesterone during a typical menstrual cycle—may also affect muscle growth, sometimes for the better and other times for the worse.
Females can optimize their resistance training gains by adapting their workouts based on the hormonal fluctuations of estrogen and progesterone across their menstrual cycle.

When I learned about this, I had to wonder: Should I pick up an extra certification around the topic? After all, seventy percent of my client base is female.

According to a paper published in the American College of Sports Medicine’s Exercise and Sport Sciences Reviews, you might want to save your money, at least for now. (Spoiler: The paper is titled “Hormones, Hypertrophy, and Hype.”1)

But first, a primer on hormones during the menstrual cycle.

Before we cover what the paper found, let’s briefly review the menstrual cycle:

▶ Day one of a cycle is marked by the first day of bleeding. Typically, estrogen is at its lowest point.

▶ Then, the hypothalamus, a region in the brain, releases gonadotropin-releasing hormone (GnRH), which tells the pituitary gland to make follicle-stimulating hormone (FSH). This stimulates aromatase—an enzyme in the ovaries—to convert androstenedione into testosterone and eventually into estrogen.

(Note: The female body also makes testosterone outside of the ovaries.)

▶ As estrogen levels rise, follicles (fluid-filled egg sacs) start to mature. Eventually, around day seven, estrogen levels peak, which triggers the brain to stop producing FSH. Instead, luteinizing hormone (LH) rises, peaking around day 13 of the cycle, triggering ovulation. Around this point of the cycle, testosterone and growth hormone levels are at their peak.2,3

▶ After ovulation, estrogen levels fall, and progesterone levels rise, which prepares the uterus for implantation (at least in theory).

If the above feels “too much,” the chart below offers highlights that will help you understand the study.

What the study found

A trio of scientists from McMaster University—including research-heavyweight Stuart M. Phillips, PhD—gathered available evidence about the interplay between hormones—testosterone, growth hormone, estrogen, and progesterone—and muscle growth. Their review included 61 studies.1

(The scientists also looked at hypertrophy differences between males and females.)

According to folks who promote periodized menstrual-cycle-based training, the middle of the cycle—when estrogen, growth hormone, and testosterone levels peak—is the best time for someone to push at the gym. That’s because estrogen, like testosterone and growth hormone, is anabolic or growth-promoting.

However, according to the McMaster researchers, rigid menstrual cycle training protocols generally fail.

That’s partly because menstrual cycles can be unpredictable.

Typically, a menstrual cycle lasts 28 days, with ovulation around the halfway mark. However, in some females, the cycle is shorter, or longer. Even in the same person, cycle length may vary from one month to another. Hormonal contraceptives, stressors, overtraining, undereating, and other factors can also affect one’s cycle.

These variations have muddied the results of much of the available research, as many studies didn’t use calendar tracking, ovulation testing, or blood draws to confirm the actual menstrual cycle phase of study participants.

In addition, while research has linked long-term declines in female hormones with muscle loss, it has yet to show that short-term fluctuations have an effect.

For example, testosterone and growth hormone both rise after a strength training session. However, numerous studies indicate that this short term boost isn’t robust enough to significantly affect muscle protein synthesis.

The same is likely true of short-term hormone shifts during the menstrual cycle, where fluctuations of estrogen, testosterone, growth hormone, and progesterone last mere days—not months or years.

Say the researchers, “Given the current state of the literature and the hype surrounding phase-based training, it is premature and even misguided for females to plan and periodize their [resistance training] regimen based on hormonally-mediated advantages or disadvantages in certain phases of their menstrual cycle.”

As a result, they concluded:

No strong evidence supports adjusting resistance training based on the phase of someone’s menstrual cycle.
While coaches can and should adapt training for female athletes who are experiencing cramps, pain, and other menstrual symptoms, there’s no reason to adapt training for athletes without symptoms.
Encouraging clients to exercise based on their cycle could do more harm than good by limiting autonomy and causing clients to go easy when they otherwise would benefit from going harder—and vice versa.

Takeaways

1. There’s still a lot we don’t know.

The researchers stopped far short of calling menstrual cycle training “bogus.” Perhaps one day science will uncover more support for this method.

However, at the moment, the hype in support of menstrual cycle training has far outpaced the actual science, say the researchers.

As study author Stuart Phillips explained in a social media post, “We call for more rigorous research methodologies, particularly when studying the menstrual cycle's impact on exercise, to advance the understanding of how internal biological factors interact with external training variables in driving muscle hypertrophy.”

2. Menstrual symptoms still matter.

Depending on the phase of their cycle, some females experience bloating, muscle aches, joint pain, headaches, abdominal cramping, fatigue, and gastrointestinal upset.

Those factors can, of course, interfere with someone’s ability to bang out 10 to 15 strenuous reps.

The McMaster review doesn’t question these very real experiences and outcomes. On the contrary, the researchers emphasized that coaches should adapt someone’s training based on how they feel that day. After all, that’s what individualized training—or what we call “client-centered coaching”—looks like.

However, not all females experience bothersome menstrual symptoms. Or they might have worse symptoms some months and not others.

__When in doubt, trust what your client tells you about how she feels over and above how you think your client should feel. __

3. I don’t ask women about their cycles.

A lot of my clients don’t welcome such personal questions.

Instead, I ask them the same question I ask my male clients: How are you feeling today?

Their answers give me all I need to know to adapt someone’s training program. If a client tells me she’s feeling “blah” and that her usual load feels weirdly “too heavy,” we consider adapting. We then go lighter and work more on technique—or, if symptoms are significant, I advise them to skip the weights and do a light active recovery session instead.

On the other hand, if someone tells me she feels like she could hoist a car over her head, it’s likely a great time to increase the training volume or load.

Closing Thoughts

The idea of menstrual cycle-based training has captured attention in the fitness world, and it’s easy to see why. It promises a new level of personalization and optimization, a way to work smarter, not harder. However, as the research currently stands, the science hasn’t caught up with the hype. While it’s true that hormonal fluctuations occur throughout the menstrual cycle, there’s no strong evidence to suggest these shifts meaningfully impact muscle growth or resistance training outcomes.

What matters most is how someone feels on any given day. By focusing on individual readiness and adapting training to your own feedback—rather than rigidly adhering to a hormonal calendar—we can support better outcomes while fostering autonomy and trust. Training should empower you, not constrain you to rules that may not serve your unique physiology.

The takeaway? Science evolves, and this area of research might someday provide clearer answers. But for now, the best approach is to listen to your body, work with what feels right, and remember that consistency and effort over time are the true keys to progress.

Michael Beiter

Personal Trainer

Nutrition, Sleep, Stress Management, and Recovery Coach