Cycle tracking is having a ‘moment’ among female athletes, due in part to the recent success of the U.S. women’s soccer team and their public acknowledgement of the role that this tactic played for them. The general idea is that there are predictable fluctuations in mood and behavior across the menstrual cycle, which may impact individual physical performance and/or team communication. People like Gabrielle Lichterman (the brains behind Hormonology), Stacy Sims (author of Roar), and Georgie Bruinvels (developer of the FitrWoman app), are leading the charge, encouraging women to become more familiar with their cycles as well as with a few basic ‘hacks’ for optimizing performance (in athletics and in life) across the various phases.
Most people are relatively familiar with the concept of a ‘period’, but a menstrual cycle constitutes a lot more than just those few days of bleeding each month. A woman’s full cycle can vary in length (28 days is a common standard, but anything from 21 to 35 days is considered normal) and involves multiple hormonal shifts happening every single day. Every woman is different (and really, every month can be different!), but while some will experience more hormonal impact than others, certain phenomena will also be common among the majority.
Particularly relevant for female athletes is the fact that there are chemical changes in exercise metabolism across the phases of the menstrual cycle. The simplified version is that we’re better at using carbohydrates for fuel during cycle weeks 1 and 2 (follicular phase, pre-ovulation), then comparatively better at burning fat in weeks 3 and 4 (luteal phase, post-ovulation). The more scientific explanation is that estrogen promotes glucose availability, while progesterone is both glucose-suppressing and more catabolic to muscle tissue. While this isn’t necessarily ‘convenient’ for 21st-century athletes, it does make complete sense from an evolutionary perspective: the ability to shift to a different effort mechanism in response to hormone levels would serve to chemically protect a (theoretical) pregnancy. Really, from a bird’s-eye view, it’s one of the coolest abilities of women’s bodies!
There’s some debate as to whether female athletic training schedules should be actively adjusted to account for these metabolic shifts, versus whether it’s simply one more factor to be aware of when analyzing performance. Recent science seems to indicate that the effect is probably more likely to be secondary than primary. In other words, it isn’t that we suddenly ‘aren’t strong enough’ to lift a given weight or sprint a given pace in the second half of our cycle; our raw physical abilities don’t change that quickly. Rather, it’s that our capacity to execute a given task is chemically influenced — both due to the aforementioned metabolic changes and their ripple effects (for example, a lot of us suffer from disrupted sleep in the luteal phase, which impacts our recoverability). Another crucial piece of this is that our mental game is also significantly impacted by hormones (scientifically: lower estrogen leads to lower serotonin) — and it’s no secret how very much that matters.
A general week-by-week breakdown is as follows. (Caveat that this only applies to women who are not using the birth control pill/patch/ring; in those situations, ovulation is not taking place – their ‘period’ is not a period; it’s an estrogen withdrawal bleed induced by the medication – and therefore, their hormone levels remain steady from day to day.)
Week One: the period, traditionally considered the ‘first’ week of the menstrual cycle. Estrogen and progesterone are at their lowest, which means they’re causing a minimum of interference, and our (comparatively small) amount of testosterone can dominate a little more. (Ironically, we are hormonally ‘most like men’ when we’re bleeding!) This means that, contrary to popular belief, this week has the potential to be a great time of month for athletic performance. The perception that we can’t perform well while on our period is largely driven by potential secondary factors (namely cramps, anemia, and prostaglandin-induced digestive issues), rather than by the hormones themselves.
Key takeaway: iron levels. It’s not essential to understand every detail of the pathophysiology behind athletic anemia, but it is useful to know that there are additional factors at play for athletes beyond just nutrition and menstrual blood loss. (In short, strenuous training leads to higher cortisol, which in turn leads to higher levels of hepcidin, which is a liver-derived hormone that inhibits iron absorption.) A female athlete may benefit from iron supplementation, especially during the week of her period.
Week Two: a.k.a. “Superwoman Week.” Estrogen — the more ‘energizing’ of the two hormones — is steadily rising, but we haven’t ovulated yet, so there’s no progesterone to counter it. For most of us, this is our favorite week, whether we consciously realize it or not; it’s a time when we tend to feel sassy, social, optimistic, and physically strong. It’s usually our leanest week in terms of body composition, and from an athletic perspective, we’re often better-coordinated, feel more quickly recovered after hard efforts, and usually feel highly motivated to train. (Ironically, it’s worth noting that multiple studies have also demonstrated increased risk of injury – specifically ACL tears – during this cycle phase, thought to be due to increased ligamentous laxity.)
Key takeaway: this is often a good week to go for a PR. Regardless of what exactly drives the phenomenon (whether the factors at play are primarily physical vs. mental), the reality is that we tend to be able to execute better during this week.
Week Three: is a roller coaster. From a physical standpoint, ovulation marks the first appearance of progesterone, which is a ‘slowing’ hormone that makes us feel more quiet, tired, and hungry. Further, significant from a mental standpoint is that estrogen also plunges post-ovulation. Low estrogen is closely linked to depression and negativity (because of its effects on serotonin), and this drop is the most abrupt change of the whole cycle — which can feel all the more catastrophic because of how unstoppable we felt just a couple of days prior!
A good explanation for this phase is that it’s the week when “your body assumes that you could be pregnant” — because ovulation occurred, and so, from an evolutionary standpoint, the smart response is to briefly “assume” that there could be an embryo to protect. All the changes that happen during this week — increased appetite, slower digestive system, increased fatigue, water retention, metabolic shift toward increased fat-burning — are intended to nourish an early pregnancy.
Key takeaways: SLEEP and FOOD – we need lots of both. We’ve established that, scientifically, the physical impact on athletic capacity is minimal enough that it’s probably not worth proactively adjusting training around cycle — however, our nutrition and sleep requirements change noticeably during this week, so on a secondary level, our performance will inevitably be impacted if we don’t respond appropriately. Our basal metabolic rate increases slightly during this cycle phase (most estimates say we need about 150 more calories per day in weeks 3-4 than we did in weeks 1-2), and we also become more sensitive to drops in blood sugar, which means proper fueling becomes even more important than usual. Further, we’re less efficient at cooling our body temperature during this cycle phase, which means that for prolonged endurance work, such as that of marathoners or triathletes, we’re significantly more prone to heat injury and electrolyte disturbances (Stacy Sims’ book Roar contains a lot of superb information about the fueling and hydration strategies that will best counter this). However, it’s worth mentioning that, depending on the sport, cycle weeks 3 and 4 also have the potential to be really good performance weeks; being a little more inclined towards fat-burning means steady-state work can often feel significantly easier.
Week Four: is when our bodies finally get the memo that we are not in fact pregnant, and thus start getting ready for our next period. Contrary to cultural expectation, this week actually has the potential to feel a lot better than week 3 — first, because both female hormones are trending down (causing progressively less interference), and also because the changes are more gradual (compared to the peaks and valleys of week 3). There are still challenges to contend with, especially for the first half of the week — falling estrogen leads to irritability; falling progesterone messes with sleep — however, as athletes, clearing those hormones out often actually feels good in terms of our physical performance, and many women report that they feel stronger during their ‘PMS phase’ than they did at other parts of the week.
Key takeaway: sleep. (Yes, again.) The fact that both hormones are now trending down means a double whammy in terms of the potential sleep impact. One supplement that can be helpful (in athletes of any gender!) is magnesium, which helps with muscle relaxation and recovery as well as with sleep. Nutrition also plays a role; a common phenomenon among hard-training female athletes is ‘sleep maintenance insomnia’ (where we go to sleep fine, then wake up in the wee hours). This can become more prominent during cycle weeks 3-4, the most common reason for which is a calorie deficit (intentional or otherwise); the stressor of the deficit means cortisol doesn’t drop appropriately overnight. Adding 30-40g of slow-release carbs (like oats) to the bedtime meal can often help with this.
The first step is simply paying attention. Knowledge is power. Tuning into our bodies’ patterns can’t do any harm. If the only thing we gain from tracking our cycles is that we find it easier to forgive ourselves when we have a bad training day during our luteal phase — well, that’s a pretty valuable benefit right there, isn’t it?
The bottom line here is that a menstrual cycle isn’t an ‘excuse’. It’s a stimulus to keep learning about ourselves, as women and as athletes. The state of our hormones on a given day is just one more impetus to learn how to adapt and work within fluctuating circumstances. We already do this with plenty of other physical realities — ‘uncontrollable’ ones like injury or pregnancy or weather conditions, but also voluntary ones: the choice to swing a heavier kettlebell on a given day, or to set a more aggressive pace goal this week, or to lift from a deficit instead of from the floor. We’re broadening our self-awareness — and, therefore, our capacity — every time we push the limits of what’s ‘comfortable’. Our hormonal cycle is a challenge of a slightly different nature, but that doesn’t mean we aren’t made better — and stronger — for it.
- The chemical shifts during a cycle are real, just because we can’t ‘see them’ doesn’t mean they don’t exist
- Tracking your cycle is a way to keep learning about yourself, as a woman and an athlete.