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).
Competitive athletes have been the lone voices calling attention to the everyday links between their cycles and physical performance. The UK’s West Brom women’s football team recently traded their white shorts for navy due to worries that the chance of visibly leaking period blood was impacting their focus (4). 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 (5,6). Similarly, runner Dina Asher-Smith could not complete a race at the 2022 European Championships due to period pain (7). Stories like these represent a much-needed new era for more open and honest conversations about menstruation and physical activity.
And it’s not just about athletes. Understanding the links between energy, activity levels, and menstrual cycles applies to you, me, and 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.
It starts with understanding your own 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 (8). Your cycle can be affected by your diet, activity level, health conditions, and stress, among other things (9). It can provide you with important feedback about your body.
The menstrual cycle has two broad phases: the follicular stage (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 period volume and flow (8).
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 (10). Even in people with fairly predictable periods, ovulation doesn't happen on the exact same day for every cycle (10).
Scientific estimations of the length of menstrual cycle phases are based on statistical models that calculate averages of when these changes commonly occur (11). Tracking your period and the different experiences you notice throughout your cycle is the best way to understand how your body is unique.
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. 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 (12). Tracking your cycle, energy level, and exercise in the Clue App is the best way to understand what type(s) of exercise work best for your body throughout the month.
So what could play a role in your training during the different phases of the menstrual cycle based on what we know so far?
Current research suggests that exercise performance might be slightly reduced in the early follicular phase (when your period starts) compared to all other menstrual cycle phases (12). 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 (12). As science explores the connections between hormones and exercise, we learn more about how estrogen and progesterone influence muscles and energy levels (12).
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 (12). There is some evidence that the late follicular phase (the week after your period)and the mid-luteal phase (the week after ovulation) may positively influence aspects of fitness, mainly because of the presence of higher estrogen levels (12). The phases of your cycle with lower estrogen levels may result in reduced energy and performance, but again, the current evidence is limited (12).
Researchers have also found that muscles may be more vulnerable to injury or strain when estrogen is low, offering less protection against inflammation (12). 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 (13,14).
It is recommended to listen to your body during all phases of your cycle to develop an individualized routine for physical activity. 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. That doesn't mean you should entirely skip training in this phase; you just might want to consider lighter activity and more recovery time during the first week of your period.
Can menopause or hormonal contraceptives impact strength training and exercise performance?
People with cycles spend one-third of their lives in a lower sex hormone state, known as menopause (when cycles end) (8). Lower levels of the sex hormones (estrogen and progesterone) could result in decreased strength and slower muscle building (especially in your lower body), which is why it is so important to stay physically active as you age to maintain your strength and balance (15).
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 that signal ovulation (16). This could result in a possible (and slight) decrease in exercise performance (16). Still, the difference is insignificant and should not influence decisions on contraceptive use (16). There is some evidence that OCPs could offer protection against some athletic injuries by stabilizing and reducing hormonal fluctuations (17).
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. The latest Clue app update includes 10 exercise tracking options, with new options for walking, pilates, strength training, stretching, Kegels, and rest days.
Sex hormones vary from puberty to menopause (and if you use hormonal medications like contraceptives or gender-affirming hormone therapy). 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 menstrual cycle changes and concerns with your healthcare provider. There are some sports medicine providers that 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.