For a long time, female athletes were told the same thing as men when it came to training. That basically went like this: be consistent, progressively overload, recover, repeat. If something felt off, the solution was usually to push through. What rarely entered the conversation was the menstrual cycle.
The reason is partly historical. For decades, women were underrepresented in sports science research. Hormonal fluctuations were considered “too variable” to control for, so many studies focused on male participants instead. The result is that much of the training culture endurance athletes inherited was built around relatively stable male hormone profiles.
But female physiology is not static. It is cyclical. And that has implications for performance, recovery, and adaptation.
The important question isn’t whether women are capable of training at the same intensity as men; we know that they are. The question is how cyclical hormonal changes influence the experience of training across the month, and how athletes can respond intelligently.
Understanding the role of hormones
A typical menstrual cycle is divided into two main phases: the follicular phase (from menstruation to ovulation) and the luteal phase (from ovulation to the start of the next period). These phases are defined primarily by fluctuations in estrogen and progesterone.
In the early to mid-follicular phase, estrogen begins to rise while progesterone remains low. After ovulation, progesterone levels increase significantly during the luteal phase, alongside moderate estrogen levels.
So, what does this all mean for training? Estrogen has been associated with improved insulin sensitivity, enhanced glycogen storage, and a potential protective effect on muscle damage. Progesterone, on the other hand, is linked to increased core temperature, altered ventilation, and shifts in substrate metabolism.
Research suggests that women may rely slightly more on fat oxidation during the luteal phase and more on carbohydrate metabolism during the follicular phase. While the magnitude of these differences varies between individuals, they can influence how certain efforts feel, particularly high-intensity work that depends heavily on carbohydrate availability.
Core body temperature typically rises by about 0.3–0.5°C after ovulation. That might sound minor, but even small changes in thermoregulation can affect perceived exertion, especially in hot conditions. Some studies have also shown slightly elevated resting heart rate and ventilation during the luteal phase, which may contribute to the sensation that efforts are harder at the same workload.
Performance across the cycle: What the evidence shows
That said, the idea that women are automatically stronger in one phase and weaker in another is an oversimplification. Systematic reviews examining strength and endurance performance across the menstrual cycle show mixed results.
Some research indicates that maximal strength and power output may be slightly higher in the late follicular phase, when estrogen peaks and progesterone is still relatively low. Other studies find minimal differences across phases. Endurance performance data are similarly inconsistent, with some athletes demonstrating stable output across the month.
The most consistent finding in the literature is variability. Between-woman differences are often greater than within-woman differences across the cycle.
In practical terms, this means that while hormonal fluctuations can indeed influence performance, they do not necessarily dictate it. An athlete can still set a personal best in the luteal phase. She can still struggle in the follicular phase. Hormones are one variable within a complex system that includes sleep, fueling, stress, and training load.
Estrogen appears to have a protective effect on muscle tissue and connective tissue, potentially reducing exercise-induced muscle damage in certain phases. Some evidence suggests that ligament laxity may vary across the cycle, though findings are inconsistent and do not justify broad conclusions about injury risk.
What is becoming increasingly clear is that ignoring the menstrual cycle entirely is not evidence-based either.
Energy availability and RED-S
One area where the data are strong is energy availability.
Research on low energy availability, the state that occurs when energy intake is insufficient relative to energy expended, shows that it can disrupt normal hormonal function, impair bone health, and increase injury risk in physically active women. In particular, chronic low energy availability is linked to menstrual disturbances (because the body suppresses reproductive hormone signalling to conserve energy), reduced bone mineral density and strength, and a higher incidence of bone stress injuries, all of which negatively affect overall health and athletic performance. Endurance athletes are particularly vulnerable, especially in sports that emphasise leanness.
The menstrual cycle itself can influence energy needs. Some research suggests that resting energy expenditure may increase slightly during the luteal phase, along with carbohydrate requirements. If intake does not rise accordingly, athletes may feel disproportionately fatigued in the days leading up to menstruation.
When women report that the “week before their period” feels harder, the explanation is often multifactorial: hormonal shifts, changes in sleep quality, altered thermoregulation, and, in some cases, subtle underfueling. Nevertheless, upping the carb intake may very well end up being more impactful than modifying training volume.
The role of sleep and recovery
If you’re a woman, you already know that sleep quality can fluctuate across the menstrual cycle. Even if you stick to your routine like clockwork, the rise in progesterone after ovulation is associated with a small increase in core body temperature and may reduce deep sleep in some individuals. Even minor changes in sleep architecture can affect reaction time, mood, and high-intensity performance.
This is where things can get tricky. Essentially, perceived performance drops are not always directly hormonal; they can also be driven by inadequate recovery.
When athletes begin tracking their cycle, sleep, and training data together, patterns often emerge. A slightly elevated heart rate, heavier legs, and reduced sleep in the late luteal phase can create a perfect storm for tough interval sessions. Recognising that pattern allows for strategic flexibility rather than self-criticism.
Individual tracking over generic prescriptions
This lack of clarity and easy-to-implement guidance can feel frustrating, but it’s also empowering. Thankfully, the current direction of research in female sports science is moving toward individualised monitoring rather than rigid phase-based programming.
Large-scale reviews emphasise that while group-level trends exist, they are not strong enough to justify universal training prescriptions based solely on cycle phase. Instead, experts recommend that athletes track their own responses over several months.
By noting cycle phase, subjective effort, heart rate, power output, mood, and sleep, athletes can identify personal patterns. Some may discover that their highest-intensity sessions consistently feel best in the early follicular phase. Others may find no meaningful fluctuation at all.
Moving toward informed training
For years, women were expected to fit into models that did not account for that system. The current shift in sports science is about refining best practices that account for women’s bodies. Tracking the menstrual cycle, prioritising adequate fueling, protecting sleep, and allowing minor adjustments in training intensity are all offering useful applications of data.
Training as a woman is all about working within your unique rhythm. And when that rhythm is understood rather than ignored, performance becomes more sustainable, more predictable, and ultimately, a lot more fun.
