For athletes, the phrase “listen to your body” is not foreign. However, many might overlook how listening to oneself connects to the menstrual cycle and its impacts. At SPECS, we acknowledge that not everyone who menstruates identifies as female, and many who identify as female don’t menstruate. Therefore, it is important to consider inclusive terminology when recognizing athletes who menstruate. Terms that we use include, but are not limited to: those who menstruate, people with uteruses, and those who are assigned female at birth (AFAB).
The menstrual cycle consists of four distinct stages spanning approximately 28 days, although this varies from body to body. Menstruation occurs between days one and five, and is characterized by the shedding of the uterine lining; this is what many know as a period. Simultaneously, hormone levels in the body decline. Such hormones include estrogen and progesterone, which have impacts on muscle strength and physical performance. Estrogen and progesterone play essential roles in an athlete's function, as estrogen increases nervous system activity, leading to better endurance, strength, speed, and coordination. Progesterone does the opposite, essentially acting as an inhibitor.
Following the menstruation phase, the body transitions into the follicular phase. This phase occurs between days six and 13. During the follicular phase, estrogen levels rise while progesterone levels fall, leading to increases in the body’s strength and power. Strength and power increase continuously throughout the follicular phase, as estrogen levels continue to rise and peak in the late follicular phase. In addition to greater strength and power as a result of an increase in estrogen levels, the probability of soft tissue injuries is also lower because estrogen reduces muscle stiffness.
In summary, the body’s strength and, thus, athletic performance, peak when estrogen levels are highest and progesterone levels are lowest. Estrogen levels peak around day 14 (depending on the individual), when the body transitions from the late follicular phase into the ovulatory phase. Ovulation is when the egg is released from the ovary, and the body is most fertile. This phase is also characterized by an increase in vaginal discharge.
After this increase in strength and power leading up to the day of ovulation, there is a subsequent decline, and the body returns to its “starting point.” This “decline” is characterized by the production of progesterone, the hormone that inhibits strength and power abilities. As the luteal phase progresses, progesterone levels continue to climb. In fact, the luteal phase is sometimes characterized by feelings of weakness. While this can vary from person to person, there is evidence that the luteal phase’s increase in progesterone can inhibit muscle building and recovery, contributing to feelings of weakness.
While the correlation between the menstrual cycle and athletic performance isn’t frequently discussed, one challenge in athletes who menstruate is commonly talked about: amenorrhea. Amenorrhea is the absence of a period for longer than three months in someone who previously had a period. It can occur when an athlete’s calorie intake does not match their output during high-intensity training. Although common and oftentimes overlooked, this is not normal. Amenorrhea can have long-term effects, such as a decrease in bone density, which can lead to stress fractures, an increase in musculoskeletal injuries, and various mental health challenges.
While many believe amenorrhea is a result of not eating enough, this isn’t necessarily the case; oftentimes, athletes who menstruate lack intake of specific nutrients to support their bodies. Micronutrient deficiencies are common in AFAB athletes; therefore, consuming a diverse diet and supplementing can better support training loads. Iron, Vitamin D, and Calcium are important nutrients to focus on when considering nutritional intake.
For college students, it can be challenging to maintain a balanced diet when one’s options are limited to what’s available in the dining halls. So, here is a list of Iron, Vitamin D, and Calcium rich foods you can find in Middlebury dining halls: Animal sources of Iron include: Lean red meat (beef, lamb, pork), poultry (chicken, turkey), seafood and eggs. Plant sources include: Dark green vegetables (spinach), nuts and seeds, and dried fruit. Animal sources of Vitamin D include: Salmon, tuna, cheese, and milk, while plant sources include: Mushrooms, plant-based milk (soy, almond) and orange juice. Calcium can be found in dairy products like milk, cheese, yogurt, and ice cream! Non-dairy Calcium sources include: tofu, almonds, sesame seeds, chia seeds, kale and spinach.
Because of the limited studies on AFAB bodies, knowledge in these fields is inadequate and continued research is necessary. Despite this, we can leverage existing information to better support athletes. If you think you may be struggling with amenorrhea, it is important to consult a medical provider and talk about your symptoms. The primary reason for the underreporting of amenorrhea is its normalization among AFAB athletes; therefore, it is critical to foster ongoing conversation about the menstrual cycle. While much remains to be researched and understood about the menstrual cycle and its effects, it is key to take advantage of the knowledge that is currently available to support athletes.
If you are interested in learning more, below is a brief list of researchers with online platforms who educate about menstruation and sports: Dr. Alyssa Olenick, PhD (@doclyssfitness), Dr. Stacy Sims, PhD (@drstacysims), Dr. Emily Kraus, MD (@emilykrausmd), and Female Athlete Science and Translational Research Program, a cohort of PhD researchers from Stanford University (@stanfordfastr).
