Introduction
One of the main differences between males and females is the difference in dominant sex hormones: estrogen and progesterone for females, and testosterone for males. In females, these hormones are responsible for maintaining a healthy menstrual cycle and contributing to bone health, ultimately influencing athletic performance.
More than half of elite female athletes report that hormonal fluctuations during their menstrual cycle negatively affect their exercise training and performance capacity (Bruinvels et al., 2016). However, it has also been reported that many Olympic gold medals have been won during all phases of the menstrual cycle (Fleck & Kraemer, 1990).
The Menstrual Cycle
The menstrual cycle starts with the first day of bleeding (menses), where the uterine lining is shed. Menses is the start of the follicular phase, or "low hormone" phase, characterized by low luteinizing hormone (LH), follicle stimulating hormone (FSH), progesterone, and slowly increasing levels of estrogen. Estrogen starts to increase around day 5-6 and surges around day 14-16, along with LH. The follicular phase lasts for the first 14 days of the menstrual cycle (assuming a 28-day cycle).
On day 14, an egg is released, and estrogen then drops for several days. This is known as ovulation. The luteal phase starts on day 15 and lasts through day 28, where the uterus prepares for a potential pregnancy. Progesterone (and estrogen) start to rise, peaking 5 days prior to the onset of bleeding. Premenstrual syndrome (PMS) symptoms start to occur when progesterone levels rise. If a fertilized egg isn't implanted, progesterone and estrogen levels fall, causing the uterine lining to shed, bringing you back to day 1 of the menstrual cycle (Sims & Yeager, 2016).
The Female Sex Hormones
Hormones are chemical messengers produced by the endocrine glands and released into the bloodstream. The women's menstrual cycle has fluctuations in various hormones:
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Estrogen: Primarily produced by the ovaries, plays an important role in reproductive and sexual development once a female reaches puberty.
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Progesterone: Produced by the ovaries, adrenal glands, and placenta, plays an important role in preparing the uterus for pregnancy (luteal phase of menstrual cycle) and maintaining pregnancy.
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FSH: Produced by the pituitary gland, initiates the formation of follicles in the ovary and follicle cells to produce estrogen.
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LH: Produced by the pituitary gland, triggers ovulation at the end of the follicular phase.
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Testosterone: Women also produce testosterone, though at lower levels than men (normal male testosterone: 250-900 ng/dL; normal female testosterone: 15-70 ng/dL).
Menopause and Perimenopause
Menopause is the last menstrual period, defining the end of a woman's reproductive years as her ovaries run out of eggs. The cells in the ovary produce less and less hormones, and menstruation eventually stops.
Perimenopause is the period of time preceding and just after the menopause itself, lasting on average one to four years. The median age of onset of perimenopause in industrialized countries is 47.5 years, but this is highly variable. Menopause itself occurs on average at age 51, but can occur between ages 45 to 55 (Sims & Yeager, 2016).
Perimenopause Symptoms
The changes in hormone levels during perimenopause can lead to a varied set of physical and emotional symptoms, including:
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Progesterone Deficiency Symptoms: Irregular bleeding, short cycles, heavier flow, premenstrual spotting, PMS (moodiness, hot flushes, depression, poor concentration, irritability, anxiety, headaches)
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Estrogen Excess Symptoms: Excessive, prolonged, or frequent bleeding, breast tenderness, bloating, headaches, weight gain, vaginal discharge
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Estrogen Deficiency Symptoms: Hot flushes, night sweats, heat intolerance, insomnia, fatigue, headaches
Not all women will experience all of these symptoms, and the severity can vary greatly (Sims & Yeager, 2016).
Hormonal Changes During Menopause
As estrogen levels drop during menopause, a woman may experience changes in mood and irritability, decreased melatonin production leading to sleep disruption, hot flashes, loss of skin elasticity and thinning, loss of menstruation and ovulation, decreased bone density, body fat redistribution, decreased muscle mass, and impaired glucose metabolism (Franklin et al., 2009; Greendale et al., 2019; Barros et al., 2006).
Hormonal Replacement Therapy (HRT)
Hormone replacement therapy is used during perimenopause and menopause to help alleviate the symptoms of decreased estrogen, such as hot flashes and vaginal dryness. There are two types: estrogen-only (topical, pill, patch, vaginal) and estrogen plus progestin (pill). HRT is recommended to be used for the shortest amount of time possible (ACOG, n.d.).
HRT can provide benefits for perimenopausal women beyond preventing pregnancy, including more regular menstrual cycles, reduced menstrual bleeding, decreased uterine pain, decreased risk of ovarian and uterine cancer, reduced hot flashes, and maintenance of bone strength. However, HRT use by perimenopausal women has also been associated with an increased risk of blood clots, heart attack, stroke, and breast cancer (Senanayake & Potts, 2008).
Managing Periods with Contraceptives
Hormonal contraceptives (HCs) suppress the natural endogenous production of estrogen and progestin to prevent ovulation, putting females using HCs in a "low-hormone phase" regarding the natural ovarian hormones. A recent study showed that 50% of female athletes use some kind of HC that affects their menstrual cycle, with the oral contraceptive pill being the most popular type, used by almost 80% of the sample (Prevalence and Perceived Side Effects of Hormonal Contraceptive Use and the Menstrual Cycle in Elite Athletes, 2020).
While HCs can have negative side effects that may affect performance, such as weight gain, irregular periods, and poor skin, 13% of contraceptive users reported that they liked the regularity of the pill and knowing when they would experience their withdrawal bleed. There is some evidence that HCs do not affect training-induced changes in performance, but more research in this area is needed (Myllyaho et al., 2018; Burrows & Peters, 2007).
The Menstrual Cycle and Health
Having a natural menstrual cycle with phases of high estrogen concentration is associated with good bone health and better fertility outcomes. However, disturbances to the menstrual cycle, such as irregular periods or amenorrhea, can be a sign of low energy availability, leading to the Female Athlete Triad (Relative Energy Deficiency in Sport - RED-S) (De Souza et al., 2017; Mountjoy et al., 2014). This can have substantial health consequences, including psychological, gastrointestinal, bone health, endocrine, hematological, immune, cardiovascular, and menstrual dysfunction issues.
Missed periods are a red flag that there is an imbalance in the hormonal axis and likely an underlying energy deficiency (RED-S) (Sims & Yeager, 2016).
How the Menstrual Cycle May Affect Female Athletic Training and Performance
Approximately 75% of athletes experience negative side effects due to menses, including cramps, back pain, headaches, and bloating (Bruinvels et al., 2016). Fluctuations in strength, metabolism, inflammation, body temperature, and fluid balance coincide with hormonal fluctuations throughout the cycle (Oosthuyse & Bosch, 2010).
The potential effects of hormonal fluctuations during the menstrual cycle are as follows:
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Follicular Phase: Higher pain tolerance and perceived energy levels, especially early in the phase, priming the body for high-intensity workouts. Carbohydrate loading may be important for endurance athletes due to the rise in estrogen in the late follicular phase. Strength training may be more effective when estrogen levels are higher (Sarwar et al., 1996; Wikstrom-Frisen et al., 2017).
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Ovulation: Potential time to achieve strength gains, as a significant increase in quadriceps strength has been reported during ovulation (Sarwar et al., 1996).
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Luteal Phase: The body is not primed for high-intensity training. PMS may interfere with training and performance, and body mass might be higher due to fluid retention. Increased breathing and body temperature may make it harder to run in the heat, although recent studies indicate this does not affect performance (Lebrun, 1993; Sarwar et al., 1996).
Training with One's Natural Cycle
The follicular phase is considered the "low hormone" phase, with the menstrual cycle being most similar to a male's hormonal profile. This is the best time for high-intensity training, such as VO2 work, 1 rep max and heavy lifting, tempo intervals, and double training sessions (Sims & Yeager, 2016).
The luteal phase is considered the "high hormone" phase, with progesterone being the dominant hormone. This is the best time for effort-based training sessions, as progesterone is catabolic and impairs glycogen utilization, requiring increased carbohydrate intake and BCAA/protein during recovery (Sims & Yeager, 2016).
Training with Hormonal Contraception
Oral contraceptive pills (OCPs) typically have a 3-week cycle of combined estrogen and progestin, followed by a 1-week placebo pill with withdrawal bleeding. Some OCPs have a continuous cycle of estrogen and progesterone, with no ovulation or follicular/luteal phases.
Bleeding while on OCPs is withdrawal bleeding, not a true period. It is recommended to take the pill 8-12 hours before a workout to minimize the effects of high progesterone (Sims & Yeager, 2016).
Intrauterine devices (IUDs) may also affect menstrual cycles, with copper IUDs not affecting ovulation and hormonal IUDs exerting local effects on the uterus, with many women not experiencing monthly periods.
Training in Perimenopause and Menopause
In perimenopause, training intensity may need to be decreased if recovery is impaired due to menopausal symptoms, such as sleep disruption.
During menopause, it is recommended to focus on heavy resistance training to stimulate satellite cells and preserve muscle mass, as well as high-intensity interval training (HIIT) to improve insulin sensitivity and decrease central obesity (Aboarrage Junior et al., 2018; Dupuit et al., 2020; Mandrup et al., 2018).
Mitigating PMS Symptoms
Ways to mitigate PMS symptoms for athletes include:
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Cramping: Magnesium glycinate, aspirin, zinc, fish oil
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Bloating: Simethicone (Gas-X)
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Headache and cramping: Acetaminophen (preferred over NSAIDs during training/racing due to rhabdomyolysis risk)
In conclusion, the menstrual cycle and associated hormonal fluctuations can significantly impact female athletic performance and training. Understanding these cycles and appropriately adjusting training and recovery can help female athletes optimize their performance and overall health.