Many women notice that their moods, energy levels, and overall feelings change throughout the month.
These changes are linked to the natural rise and fall of two key hormones: estrogen and progesterone.
Because hormones affect many systems in the body, including metabolism and energy use, scientists have long wondered whether these monthly shifts also change a woman’s ability to exercise at high intensity.
A new study from the University of Oregon provides important answers. The research, published in the Journal of Applied Physiology, found that hormone changes across the menstrual cycle do not reduce a woman’s physical ability to exercise hard.
However, they can change how hard that exercise feels.
The study was led by Mira Schoeberlein, a doctoral candidate in the Oregon Performance Research Lab. She explained that women have historically been understudied in exercise science. Many earlier studies either focused mainly on men or only examined women during a short part of their menstrual cycle.
Most of those studies tested women during the early follicular phase, which is the time from the start of menstruation until ovulation. During that phase, estrogen and progesterone levels are low and more similar to the hormone levels seen in men.
Because of this narrow focus, scientists did not fully understand how rising and falling hormone levels across the entire cycle might influence exercise performance.
Schoeberlein and her team wanted to study something called the maximal metabolic steady state. This is the highest level of exercise intensity that a person can maintain for a long period without quickly becoming exhausted.
It represents the boundary between exercise that can be sustained and exercise that cannot. For athletes, this boundary is very important. For example, elite marathon runners often compete just below this threshold so they can maintain speed without burning out too early.
The researchers recruited 15 women and 15 men from the Eugene, Oregon area. For four weeks, participants visited the lab once a week and completed cycling tests on a stationary bike. Each session gradually increased in difficulty so the researchers could find each person’s highest sustainable intensity.
Before every session, blood samples were taken to measure hormone levels. During the workouts, the researchers tracked heart rate, oxygen use, and carbon dioxide production. Afterward, participants rated how difficult the workout felt.
The results were clear. A woman’s ability to maintain intense exercise at her maximal steady state did not change across different phases of her menstrual cycle.
In other words, her physical capacity remained stable whether estrogen and progesterone levels were low or high. When differences in muscle mass were taken into account, men and women were able to sustain similar levels of work.
However, the study found something interesting about perception. Women reported that their workouts felt harder during the luteal phase of the cycle, which occurs after ovulation. This is the time when progesterone levels are higher. Even though their measurable performance did not decrease, their sense of effort increased.
This finding highlights an important difference between actual physical ability and personal experience. Athletes may feel that exercise is more challenging at certain times of the month, even if their performance capacity remains unchanged.
The study is also notable because it included participants using different types of birth control, such as intrauterine devices and oral contraceptives, making the findings more relevant to a wider group of women.
In reviewing these findings, it is important to recognize both the strengths and limitations of the research. The study carefully measured hormone levels and included both objective performance data and subjective reports of effort.
This provides a more complete understanding of how the menstrual cycle interacts with exercise. However, the sample size was relatively small, with 30 participants in total. Future research with larger groups and different types of athletes could provide even stronger evidence.
Overall, the study offers an empowering message. It shows that women’s bodies are capable of maintaining high performance throughout the menstrual cycle. At the same time, it acknowledges that feelings of effort and fatigue are real and meaningful.
Athletes and coaches may use this information to adjust training plans based on how an athlete feels, without assuming that performance must decline.
The research challenges outdated ideas that hormonal changes automatically limit women’s athletic ability. Instead, it suggests a more balanced view.
Physical capacity stays steady, but awareness of how exercise feels can help athletes train smarter. Listening to the body while understanding its true capabilities may be the key to maintaining and even improving performance.
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