The Complex Relationship Between Hormones & Strength, From Experts

I switched from Pilates to weightlifting about a year ago and quickly realized how much my physical strength varies throughout my cycle. One week I can run through bicep curls with 15-pound dumbbells, no problem. The next? I'm struggling to reach half the reps using the very same weights. 

Knowing how the menstrual cycle's fluctuating hormones can affect mood and energy, I started to wonder if they do the same for muscle strength and performance. Unsurprisingly given the gender gap in medical research, I hadn't heard much about this topic before.

Given the complexity of a woman's hormone cycle and the significant research gender gap, it's not surprising that the answer to this question is multifaceted and still in the early stages of understanding.

Nevertheless, we can take a magnifying glass to the peaks and valleys of hormones like testosterone, estrogen, and progesterone and gain valuable insight into the ebbs and flows of strength too.

When your period begins, your energy-giving hormones are at a low, explains functional medicine gynecologist Wendie Trubow, M.D. So from a hormonal standpoint, that time, unsurprisingly, may be more of a struggle in the gym.

Fitness trainer at Centr Ingrid Clay shares a similar anecdote, stating that many of the women she trains experience a dip in their athletic performance on the days they are having their period. This looks different for each person but could mean completing fewer reps, lifting less weight, tolerating shorter workouts, or just feeling less charged during exercise.

Given the variability of period symptoms, your hunger for a challenging workout may change from month to month. If you don't experience cramps or mood swings, for example, you may not feel that dip in strength after all. 

After your period ends, your hormones will quickly rise in the lead-up to ovulation. As estrogen, progesterone, and testosterone go up, they can impact your muscles.

"Testosterone, known as the male sex hormone, plays a crucial role in muscle growth and maintenance for women1," says Anate Brauer, M.D., board-certified OB/GYN and reproductive endocrinologist at RMA New York. 

You're also getting more energy from the estrogen spike to lift heavier weights, do more reps, or exercise more often than you otherwise do during this time.

A rise in progesterone and testosterone can also stimulate increased appetite2, which will help you fuel your body for those ambitious workouts. Simultaneously, progesterone rising will help your sleep quality3, supporting optimal recovery too. 

In short, your body is primed to step up your workout regimen during this post-period follicular stage, which typically lasts about a week (or longer if you have shorter periods).

According to Clay, she's spotted a "huge difference" in strength performance during the follicular phase in many women she trains. "Their endurance is better and they're able to lift heavier for a lot longer," she adds. 

This doesn't mean you're set up for failure during the other stages of your cycle, but rather the follicular phase is rich with opportunities to excel. 

Entering the luteal phase right after ovulation comes with a quick dip in progesterone, estrogen, and testosterone, which can cause PMS symptoms like anxiety and mood swings, appetite changes, and sleep struggles. For some, this is true for the entire two weeks of the luteal phase, but for others, it's more present in the second half of the luteal phase, which precedes your period.

Luckily, there is another rise of estrogen and progesterone in the luteal phase, which may offer some relief to split up the two-week phase.

When estrogen rises, adding a second peak around day 21 of your cycle, you may feel more energized, though likely still less than during the follicular phase.

Significantly higher levels of progesterone in the luteal phase can, however, lead to increased body temperature4, which may add night sweats to the list of PMS symptoms for some folks—this higher body temperature can also impact athletic performance, especially during cardio-based workouts5.

In addition, your caloric needs may rise in the luteal phase due to a slight increase in your metabolic rate6, says registered dietitian and women's nutrition expert Lauren Manaker, RDN. So even if you aren't working out as intensely as you would during the follicular phase, you may feel more hungry and should certainly follow those appetite cues (more nutrition tips in a bit).

The luteal phase holds peaks and valleys for your progesterone and estrogen levels, so you may begin to feel a bit more lively during the high points (around day 21, as you can see on the chart). During the stark dips, the opposite could be true.

According to Brauer, women on combination birth control pills with both estrogen and progesterone may feel relatively stable energy levels throughout the month. Those on tri-phasic pills that vary in hormone levels to mimic a natural cycle may resonate more with the traditional fluctuations covered above.