Illustration by Emma Günther
Unpacking the role of your menstrual cycle in fitness and strength training
There’s a lot of buzz about cycle-syncing workouts–but what does the science actually say?
Top things to know:
The connection between exercise and the menstrual cycle looks different for everyone
Track your menstrual cycle experiences to develop your personal exercise plan
Exercise can alleviate period symptoms like pain and PMS
Hormones, and the different phases of the menstrual cycle, play an essential role in fitness and strength (1). Yet, people with cycles have been largely underrepresented in performance-based research (1,2).
Remarkably few existing studies focus on female athletes, let alone consider the menstrual cycle's role in athletic performance (1). Between 2014 and 2020, only 6% of the scientific papers published in six sports and exercise journals focused solely on female athletes (3). This may be due to the limited opportunities for women to take on leadership roles in sports research, the historical gender bias in sports, and the lack of prioritization and funding for women-focused research (2,4).
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Competitive athletes have been the lone voices calling attention to the everyday links between their cycles and physical performance. In 2022, the UK’s West Bromwich Albion women’s football team traded their white shorts for navy due to worries that the chance of visibly leaking period blood was impacting their focus (5). The Wimbledon Tennis Championship has been called to review their ‘strict all-white dress code’, and Serena Williams has openly shared her struggles with debilitating menstrual migraines (6,7). Similarly, runner Dina Asher-Smith could not complete a race at the 2022 European Championships due to period pain (8). Stories like these highlight a crucial shift towards more open and honest discussions about menstruation and physical activity. And it’s not just about athletes; understanding the links between energy, activity levels, and menstrual cycles applies to all people with cycles. Let’s unpack the basics and how we can use research (and cycle tracking) to inform our choices when it comes to working out.
What happens during the menstrual cycle?
The menstrual cycle is an important indicator of your body's functions because to have a period, many parts of your body have to work together, including your brain, pituitary gland, ovaries, and the uterus (9). Your cycle can be affected by your diet, activity level, health conditions, and stress, among other things (10). It can provide you with important feedback about your body.
The menstrual cycle has two broad phases: the follicular phase (when your period starts until ovulation) and the luteal phase (ovulation until your next period starts). Progesterone and estrogen, the primary hormones that guide the ovarian cycle, influence the changes in the uterus, such as menstruation volume and flow (9).
There isn't really a "typical" menstrual cycle. Everyone is unique, and your body is not a clock. The menstrual cycle is variable, meaning it does not always come at the exact predicted time (11). Even in people with fairly predictable periods, ovulation doesn't happen on the exact same day for every cycle (11).
Scientific estimations of the length of menstrual cycle phases are based on statistical models that calculate averages of when these changes commonly occur (12). Tracking your period and the different experiences you notice throughout your cycle is the best way to understand how your body reacts to hormonal fluctuations.
What happens to my body during exercise?
A lot is going on in your body when you exercise. Your heart beats quicker to increase blood flow to your organs, your breathing becomes faster and deeper so the lungs can pull in more oxygen, and your muscles contract to pump more back to the heart (13). Additionally, various hormones are released that enhance libido, regulate glucose levels, and promote the growth of bones and tissues (13). One group of hormones released are endorphins. These hormones alleviate pain, anxiety, and depression while boosting mood (14). Thanks to these qualities, exercise-induced endorphins can help with PMS and period pain (15).
Should I rest or train during particular phases of my menstrual cycle?
Possibly. The existing research suggests some potential links between the cycle and physical performance. For example, one study on elite female athletes suggests that being in the mid-luteal phase could affect how quickly your breathing returns to normal after high-intensity exercise (16). Yet still, there is a clear lack of evidence to influence any systematic changes to how women or people with cycles should be training (1).
Since there is so much variability in cycles and hormones, and we're only beginning to scratch the surface of the science, an individualized approach that feels best for your body is recommended (14). Tracking your cycle, energy level, and exercise in the Clue app is the best way to understand what type(s) of exercise works best for your body throughout the month.
What factors influence training during different phases of the menstrual cycle?
Research on how different phases of the menstrual cycle affect exercise performance is limited, indicating a clear need for more studies. One study shows that exercise performance might be slightly reduced in the early follicular phase (first days of your period) compared to all other menstrual cycle phases (16). While slight changes in strength or speed may be meaningful for elite or competitive athletes, they are unlikely to be noticed by people who exercise routinely for their health and well-being (17). As science explores the connections between hormones and exercise, we learn more about how estrogen and progesterone influence muscles and energy levels (17).
Estrogen may play a unique role, as it can influence the body's ability to use stored energy, activate parts of the brain responsible for decreasing inhibition, and provide some anti-inflammatory protection to muscles (17). Evidence indicates that high estrogen and low progesterone levels, which usually happen the week after your period (late follicular phase) and during ovulation (ovulatory phase) can positively influence various aspects of fitness during exercise (17). The phases of your cycle with lower estrogen levels may result in reduced energy levels and performance, but again, the current evidence is limited (17).
Researchers have found that muscles may be more vulnerable to injury or strain when estrogen is low, offering less protection against inflammation (17). As estrogen levels dip at the end of the luteal phase (before your period starts), some people may experience premenstrual symptoms (PMS), such as fluid retention, mood changes, and pain that can impact overall energy and physical outputs (18,19).
One study suggested that running might cause more inflammation after exercise during the luteal phase. This could be because high progesterone levels during this phase might counteract certain anti-inflammatory effects of estrogen (20).
It is recommended to listen to your body and adjust your exercise plan based on how you feel during different phases of your menstrual cycle (17). Rest days are essential in any training program. They may be best taken during the early follicular phase while also building in some pre- and post-workout stretching into your routine.
Can menopause or hormonal contraceptives impact strength training and exercise performance?
After menopause (when your period ends), there are lower levels of sex hormones in your body (21). Lower levels of the sex hormones (estrogen and progesterone) could result in decreased strength and slower muscle building (especially in your lower body) (21).
Hormonal oral contraceptive pills (OCPs) can also play a role in muscle building and strength because they reduce your ovaries’ hormone levels by blocking the signals from the pituitary gland that signal ovulation (22). This could result in a possible (and slight) decrease in exercise performance (22). Still, the difference is insignificant and should not influence decisions on contraceptive use (22). There is some evidence that OCPs could offer protection against some athletic injuries by stabilizing and reducing hormonal fluctuations (23).
Can the menstrual cycle affect dehydration?
Studies have shown that even as low as 2% of dehydration, meaning losing 2% of your body weight from dehydration, can affect your flexibility, speed, and endurance while exercising (24). Research indicates that you are more prone to dehydration in different phases of the menstrual cycle (25). Some research has proposed that high levels of estrogen and progesterone in the luteal phase may change your body's fluid balance, leading to dehydration (25). It’s still unclear if this indicates that you should drink more water during the luteal phase, but it’s a good idea to stay hydrated when you exercise.
Keep track of changes over time
Tracking is an important way to develop an understanding of your unique patterns. A clear picture of your baseline and changes gives clues into the relationship between your cycle and physical activity. You can track over 200 cycle-related experiences from your exercise routine to the amount of spotting with Clue.
Sex hormones vary during your lifetime from puberty to menopause, and this causes changes to your anatomy and physiology (25). Hormonal medications such as contraceptives or gender-affirming hormone therapy also include sex hormones. Shifts throughout your reproductive life stages may guide changes to your fitness plan over time. You may see that certain phases in your cycle feel better for barre or yoga, while others feel better for running and weight lifting. Remember, giving yourself permission to rest and recover is always okay.
It is important to discuss changes to your menstrual cycle that concern you, with your healthcare provider. Some sports medicine providers may be able to provide you with an individualized training plan that is safe for your body. Don’t attempt to self-medicate or self-treat with “hormones” purchased on the internet or from non-healthcare practitioners as they could cause dangerous long-term side effects.
FAQs
What is the best type of exercise to do on your period?
Research has shown that light and core strengthening exercises are great exercises during your period (27,28). Therefore activities such as yoga, swimming, or pilates might be the right option for you. There is no research indicating which exercises should be avoided during menstruation, so if you enjoy weightlifting or high-intensity workouts, feel free to continue your routine as long as you feel up to it.
Is it better to rest or work out during your period?
Studies indicate that exercising during your period can reduce symptoms of period pain and PMS (15). One study even found that those who did not exercise during menstruation reported longer periods, heavier menstrual flow, and more fatigue (29). This doesn’t mean you should force yourself to the gym if you’re feeling low on energy. Everyone experiences their period differently, so it’s crucial to listen to your body and rest if needed.
Can exercise reduce period pains?
Yes. Aerobic exercises like running and swimming, along with core-strengthening workouts, release endorphins which can act as natural painkillers (14). Studies show that exercise can sometimes alleviate period pain (15).
