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Women's Performance

Dr. Stacy Sims Answers Members’ Questions on Training and Menstruation

December 29, 2021

Stacy Sims answers WHOOP members’ questions about menstrual cycles and training.

By Casey Meserve

Dr. Stacy Sims, an expert in female physiology, answered questions during an AMA with WHOOP members. She discussed the menstrual cycle’s effect on sleep and workouts, menopause and strain, and whether the best time of the month to push yourself really is during your period.


Training and the Menstrual Cycle

Q. Can you elaborate on cycle-syncing workouts and nutrition?

Dr. Stacy Sims: In the low-hormone phase our bodies are resilient to stress. This is the time to do high-intensity workouts, heavy resistance training, and recover well. Around ovulation, estrogen is anabolic by itself, thus with the estrogen surge, another high-intensity, heavy resistance training session is the way to go.

After ovulation, with metabolic shifts and the increasing levels of progesterone and estrogen, it is time to dial it back a bit into more steady state/aerobic type work, and moderate resistance training. In the last few days leading into your next period, this is the time to recover — absorb the hard training from the previous 3ish weeks, and look to do more technique, mobility, and functional strength work (not take the days off, unless you want to).

Nutritionally, in the low hormone phase, we can access carbohydrates pretty well, so in recovery, think about increasing carbohydrate intake to help restore glycogen in the muscle and liver. After ovulation, there is a metabolic shift where your body relies more on blood glucose and cannot access liver and muscle glycogen (estrogen and progesterone reduce the ability of the body to release it).

Progesterone’s job is to break down protein, carbohydrates, and fats to provide building blocks for the uterine lining that is being built. So, your body is in a constant breakdown state. In this state, you want to increase your daily intake of carbohydrates across all meals to “level the hormone playing field” to have carbs available for training and general movement. It’s very important to boost your protein intake to hit around 30g per meal, and 30g post exercise, to stop that continuous breakdown state.

Q. What is your advice for planning training on bleeding days?

Sims: Physiologically, your body is primed to hit it hard, but psychologically our own lived experiences can impact how we feel about training/exercising on bleeding days. If you are experiencing heavy cramping and bleeding, just move–movement helps reduce the inflammation causing the cramping.

If you are hesitant to hit it hard, due to experiences or the prevailing thought that women should not train hard during their periods, try a few short bursts (sprint interval training). Something like 5-8x 20 seconds all out, 2 minutes cruise between, then call it. The super-intense work will increase post-exercise anti-inflammatory responses, release endorphins, and because it is short it is not as taxing mentally or physically as doing a full structured workout.

Q. Is caffeine helpful with cramps like it can be for headaches, or not so much?

Sims: Not so much. The cramping associated with menses are super strong uterine (muscular) contractions to expel the dying tissue. It is not like a headache that is more due to blood vessel constriction.


Recovery and the Menstrual Cycle

Q. I would love to know the science behind why recoveries are significantly better during your period.

Sims: In the low-hormone phase, there is less hormone-driven sympathetic drive, thus our bodies are more resilient to stress. After ovulation, with the rise in progesterone, there is a sympathetic dominance, reducing the ability to get into a parasympathetic state. Training during your period is one of the best ways to use your hormones to your advantage! Women can access carbohydrates well and hit high intensities and recover from that training stimulus quickly because of the resilience to stress.

Our immune systems are also more resilient before ovulation—all of this is the biological “eye” of getting the body to the best possible condition to support a fertilized egg. Don’t let the myths perpetuated by the historic marginalization of women get to you! If you feel like hitting it hard, go for it! Your body can handle it and your training potential will thank you.

Q. I would like to find out more about how the different phases of the menstrual cycle affects HRV and sleep. And whether there is anything we can do to mitigate the effects?

Sims: In the low hormone (follicular) phase HRV is highest, REM and SWS are easy to attain, and sleep efficiency is great. But after ovulation, as progesterone rises, there is a change. Progesterone stimulates the sympathetic nervous system, thus increasing resting heart rate, respiratory rate, reducing HRV, and reducing the ability to get into the parasympathetic state needed for REM and SWS.

Estrogen also comes into play during the luteal phase, by working with progesterone to suppress REM and increase wakeful episodes. To help in the luteal phase, especially the late luteal phase, good sleep hygiene practices are essential.

With regards to HRV, menstrual cycle phase training is something to consider, where you look to do more mobility, functional strength, and recovery work in the late luteal phase (4-5 days before your period starts).

Q. Can you recommend anything to help me balance my recoveries during the 7-10 days before my period, so that practice isn’t as difficult, and I feel less tired?

Sims: The recovery metrics in the late luteal phase will always be in the yellow or red as it is compared to the follicular phase. There is a change in the autonomic nervous system (ANS), which affects HRV, showing reduced recovery in the luteal phase. To help counter the symptoms, however, we need to address the systemic inflammation that comes with the peak then drop of hormones right before your bleed starts.

In this we look at using 1g omega 3 fatty acids (which helps counter prostaglandin E2, the inflammatory cytokine turned “up” by estrogen). Magnesium and zinc are used heavily in the building of, and shedding of, the uterine lining. If you have no adverse responses to aspirin, one 80mg (baby) aspirin counters the inflammatory receptor sites (Cox-1 and Cox-2) and is irreversible (thus keeps those receptor sites muted).

Q. I would like to understand the science behind losing my period during training seasons and how to get it back!

Sims: When you lose your period in hard training it is a sign of a misstep between energy intake and expenditure. Basically, you are not eating to support normal existence (think laying on the couch watching Netflix) and layering on training. You may be eating enough calories, but the timing in and around training might not be there.

If you do not fuel for what you are doing, your body stays in a breakdown (catabolic) state, this signals the hypothalamus that there is not enough nutrition to support life function and training stress; thus there is signaling to stop gonadotropin-releasing hormone (GnRH), stopping the luteinizing pulse and surge, which reduces ovulation, and thus estrogen and progesterone production.

This is called functional hypothalamic amenorrhea (from low energy availability). The first step to getting it back is to see your GP for a referral to an endocrinologist. You need to find out how low your hormones are. In conjunction, fuel for what you are doing! Eat! Especially after all training!

Q. What metrics on WHOOP might be important for someone struggling with amenorrhea?

Sims: What we know from looking at women with amenorrhea vs those who do not, is that there are more sleep disruptions and wake up times due to hypoglycemic episodes; and we see dysfunction in HRV. Meaning that there is significant variability from day to day, not phase to phase.


Advice to Male Coaches

Q. What’s the best advice you could give male coaches to help them support their female clients better?

Sims: One of the biggest elephants is actually broaching the topic of menstrual cycle status as a male coach. To help with this, we know including simple questions in general wellness check-in is successful. It comes across as a simple health question. Understanding if your female athlete is naturally cycling (and what are the patterns), on any birth control (hormonal or not), perimenopausal, or post-menopausal can enhance the coach’s ability to dial in training loads and improve the performance potential at any life stage.

But, it has to begin with an open conversation to understand where your athlete is. And taking the angle of health = performance is the best means of breaking down the taboo.


Birth Control and Training

Q. Do you have any advice for how to train and support your body as you come off birth control and start having a natural cycle?

Sims: Track!! It usually takes around 3-4 months for your body to find its natural cycle rhythm again after coming off oral contraceptives. Tracking how you feel with HRV, and other recovery metrics will help you find a good pattern to dial in days to hit it hard and days to dial it back.

Read about the WHOOP Health Monitor and how WHOOP tracks your recovery.

Q. I recently switched to a low progesterone/low estrogen birth control pill (from Nexplanon), and I noticed that my HRV numbers have tanked, but they are also more consistent. Is this expected?

Sims: First to note, when you are using the pill (any dose), you are not having a natural period, but a withdrawal bleed. The hormones in the pill downregulate your own hormones through ovarian suppression, and these hormones also have a systemic effect, which is what we found in the recent article we published on the differences between natural, oral contraceptive, and progestin-only birth control.

As the synthetic hormones build up (e.g., each week of the active pills), there is a greater impact on the ANS, increasing sympathetic activating, and reducing parasympathetic control. This is what you are seeing with your HRV change. There is less parasympathetic activation, thus a baseline increase in your resting heart rate, respiratory rate, and a decrease in the variability between heart rate (hence decreased HRV); but it is more stable, because you have a stable hormone profile with the oral contraceptive.

The implant is a slow release of progestin, with an initial suppression of follicular development and estrogen production. After about 6-8 months, this suppression reduces, thus ovulation can occur–evident in the difference between the oral contraceptive HRV and the Nexplanon HRV (more variability of the ANS).


Perimenopause, Menopause, and Training

Q: Is there any way to predict hormonal changes during perimenopause or is this just a few years of rollercoasting?

Sims: This is, unfortunately, the offshoot of the changing ratios of estrogen to progesterone in perimenopause. Some cycles there is ovulation, others there is not. This creates times of estrogen dominance, and others of a more balanced hormone profile.

What I usually recommend for women in perimenopause is to track symptoms, sleep, how they are feeling and to change more to 2 weeks “on” with maximum 6 HITT sessions, filling in the other days with heavy resistance training (3-4 per week) and recovery modalities. Then one week “off” where the focus is fully on super slow, low-intensity aerobic work and mobility, functional strength.

Q. I am past having a cycle. Is there still anything I should consider regarding hormones, training, and nutrition?

Sims: If you are now in the post-menopausal phase of life, now is the time to drop the long slow distance and to focus on SIT, HIIT, and heavy resistance training. These training protocols help do what the hormones used to do with regards to blood sugar control, anabolic signaling for lean mass development, and overall blood vessel compliance.

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Casey Meserve

Casey Meserve is a writer at WHOOP. Prior to joining WHOOP, they were an SEO Strategist at TechTarget, an editor at, and a reporter for the Old Colony Memorial in Plymouth, Mass. Casey graduated from Bridgewater State University with a master’s degree in English Literature and from Massachusetts College of Liberal Arts where they studied Journalism and played rugby. Casey lives in the woods of Rhode Island and enjoys growing vegetables and flowers for the deer to eat, running (slowly) and watching the Boston Bruins.