The Female Athlete – Why We Need To Start Talking About Periods
You have most likely heard of the body’s 24-hr biological rhythm, called the circadian rhythm, but have you heard of the female-only, 28 day, infradian rhythm?
WHAT IS THE INFRADIAN RHYTHM?
The infradian rhythm is a chrono-biological rhythm that governs a woman’s life during her reproductive years. It relates closely to a woman’s menstrual cycle, in particular the phases of her cycle and how these relate to changes in her body’s bio-chemistry. Throughout the cycle there are significant changes in levels of particular hormones that play a major role in preparing a woman’s body for reproduction, however also have a significant impact on the function of the brain, energy levels, mood and metabolism. Just like across the 24-hr circadian rhythm, where hormones such as cortisol is released to wake us up in the morning, and melatonin is released to wind us down at night, the monthly infradian rhythm and subsequent hormone fluctuations can have a significant impact on a woman’s energy and brain function.
WHY IS THIS IMPORTANT FOR ATHLETES?
In the sports performance world, where an athlete’s sole aim is to reach the pinnacle in their sport, managing the impact the menstrual cycle has on sports performance should be a crucial consideration for coaches who are designing training plans for female athletes. Acknowledging that females and males are different and that women menstruate and often get tired and emotional is not enough. Females’ are not just small men and should not be treated thus. Therefore, grasping the impact the menstrual cycle and consequently the infradian rhythm has on a female across a month, is very important for coaches who are trying to get the best out of their athletes.
The following blog aims to provide insight into the menstrual cycle and the impacts certain phases of the cycle may have on female athletes’ physiology and performance. As well as offering ways in which coaches may track their athlete’s cycles, with examples of what has been implemented by some elite sports teams. Lastly, it brings to light the importance of bringing the topic of menstruation out of the shadows and into mainstream conversation. This will help to remove the current stigma around bleeding and periods and help to raise awareness around the unique infradian rhythm that only females experience and the issues this presents for training optimisation.
THE MENSTRUAL CYCLE
The menstrual cycle varies for each individual, however is typically a 28-day cycle, which can be broken into four distinct phases (the menstrual phase, the follicular phase, the ovulation phase and the luteal phase). Day 1 of the cycle is when the menstrual bleeding starts and typically on day 14 ovulation occurs, however this is different depending on each individual’s cycle length. There are two main hormones involved, estrogen and progesterone. At about day 5 or 6, estrogen (produced in the ovaries) rises slightly. Around day 12 there is a surge in estrogen coupled with a luteinizing hormone (LH) surge, which causes the egg to be released during ovulation. Estrogen levels decrease somewhat after this but will soon rise again.
Upon ovulation, progesterone levels increase to prepare the lining of the uterus for egg implantation. This is the luteal phase and is when both estrogen and progesterone reach their highest levels (usually 5 days before bleeding begins). This is often the time in the cycle where women may have premenstrual symptoms (PMS), which can include mood swings, cramps, body aches, food cravings, breakouts and fatigue. If there is no egg implanted, progesterone levels fall and signal the lining to shed, which marks the start of menstruation and day 1 of the next cycle.
*Taken from website helloclue.com
HOW THE MENSTRUAL CYCLE MAY AFFECT PERFORMANCE
The fluctuations in the hormones estrogen and progesterone across the menstrual cycle have known bio-chemical effects on a woman’s metabolism, plasma volume levels and thermoregulation. These changes can have a marked impact on sports performance, however could be mitigated if managed correctly. Therefore, for both athletes and coaches, understanding and tracking the menstrual cycle is important so that training and nutrition may be adjusted if necessary.
METABOLISM
Estrogen is known to reduce carbohydrate oxidation and increase free fatty acid availability. This means when estrogen levels are high, women tend to conserve glycogen stores and utilize more fat as fuel. Therefore, in the luteal phase of a female’s cycle carbohydrate supplementation may be an important implementation, especially for higher intensity training or competition.
Progesterone promotes protein catabolism, which could have a negative affect on muscle recovery and adaptation. Therefore, during the luteal phase of a female’s cycle, protein supplementation is another important nutritional consideration for athletes both pre and post training or competition.
THERMOREGUALATION
Estrogen and progesterone also play an important role in plasma volume regulation. Plasma volume is the volume of fluid in the blood and for athletes in particular, the relationship of fluid volume to sodium and potassium in the blood is important. In the luteal phase, high estrogen and progesterone levels cause a drop in plasma volume by about 8% (ie. thick blood). This may have an impact on endurance performance, as improved endurance performance relates to higher plasma volumes. Therefore, it is important to focus on adequate hydration in this phase as well as sodium intake, which is depleted by progesterone.
In addition, the luteal phase coincides with an increased basal body temperature, mainly due to the higher levels of progesterone. This may have an impact on the ability to tolerate heat, as thresholds to initiate vasodilation (ie. sweating) are altered. Therefore, a consideration for coaches to mitigate this issue is to acclimatise the athlete to hot conditions and provide adequate fluid intake during training and competition.
In light of the aforementioned impacts on metabolism and thermoregulation it could be concluded that during the luteal phase of the menstrual cycle, when estrogen and progesterone are at their highest, endurance performance particularly if under hot conditions, may be compromised. A 2017 study on nine sub elite soccer players confirmed this, finding that during the mid luteal phase 7 out of 9 of the player’s performance on the yo-yo intermittent test (a test of aerobic endurance) was considerably lower as compared to during the mid follicular phase.
INJURY RISK
The fluctuations in hormones across a cycle has also been associated with injury risk. There is a higher incidence of ACL injuries in females than men and this has been related to several risk factors including increased joint laxity amongst females. Estradiol is a hormone that is believed to be linked to increased joint laxity. Estradiol levels fluctuate across the menstrual cycle and reach its peak concentration around the time of ovulation (days 12-14), with a second lower rise in the luteal phase (days 20-24). ACLs exposed to increased estradiol in cell culture show decreased fibroblast proliferation and alterations in collagen synthesis.
As this area in research is only a decade old, the data is inconclusive and more research needs to be conducted to give clarity around the exact role hormones play in injury risk. A meta-analyis conducted in 2017 showed six of 12 studies on ACL laxity provided quantitative data for meta-analysis, finding significantly increased laxity during the ovulatory phase compared with the follicular phase. Despite the fact more quality research is needed in this area, if the knowledge thus far points to an increased joint laxity/ injury risk during the mid phases (ovulation & luteal) of the menstrual cycle, how does this implicate coaching decisions made around training and competition?
*Adapted from Speroff and Fritz.
ORAL CONTRACEPTIVES
The contraceptive pill puts the body in a high progesterone state across the entire menstrual cycle. This presents extra challenges for athletes exercising in hot conditions as thermoregulation is compromised. The effect of the contraceptive pill on a woman’s performance has not been researched until more recent years. With the influx of more professional and semi-professional female athletes, particularly in team sports such as cricket, AFL, rugby and soccer, and the growing number of these women using the pill, research into its impact on the body compared to a natural menstrual cycle has become warranted. The contraceptive pill consists of synthetic hormones, which aligns the body to a 28 day cycle, where menstruation becomes optional, depending on whether the “sugar pill” is taken or not.
Research by Griffith University professor Claire Minahan and her team compared the impact training in hot conditions has on perceived effort, body temperature and skin blood flow, for athletes taking the pill versus those on a natural menstrual cycle. The results of this study found that those taking the pill had a prolonged skin blood flow response and elevated perceived effort, depicting a reduction in heat tolerance by this group. This study reflects the impact that the pill may have on an athlete’s ability to thermoregulate in hot conditions and the resultant impact this may have on hydration needs.
The use of the contraceptive pill amongst the elite athlete population needs more research to ascertain it’s affects on the body in comparison to the effects of a normal menstrual cycle. If a coach is looking at managing the impacts the menstrual cycle has on performance, they should not overlook the potential difference between a natural menstrual cycle and one that is synthetically influenced.
MONITORING THE MENSTRUAL CYCLE
Elite coaches of female athletes are recognizing the significance of the female iradian rhythm and have started to track their athlete’s menstrual cycles. Leading into winning the world cup championships, the U.S.A women’s soccer team used a menstrual tracking app FitrWoman, headed by sport scientist Dr. Georgie Bruinvels, to track player’s monthly cycles. This helped the coach understand where the player’s were at in their cycles and also helped the players understand their bodies and hormonal fluctuations better. The app has been designed especially for athletes and includes insights and advice on nutrition, recovery and training guidelines to help optimize performance across each phase of the cycle.
Closer to home, Brisbane’s AFLW high performance manager Matt Green implemented menstrual cycle tracking earlier this year for his players. The main phase of interest was menstruation and if the associated bleeding was heavy and if there was cramping or other symptoms that may affect their training or performance.
Tracking menstruation is the most simple and practical phase to measure for most females, with the accuracy of measuring other phases of the cycle limited to less appealing tracking tools, such as taking daily basal body temperature or monitoring cervical mucous. The other limitation in monitoring is that many women need to be educated about their cycles and may not completely understand the menstrual cycle phases and how they impact their bodies. This is in part due to the stigma around menstruation. Many women are embarrassed about their periods and it is a bit of a taboo topic, so most women don’t talk about it. This is crazy when you can see just how much of an affect it can have on the body and potentially impact performance. Opening up conversations around menstruation amongst teammates and coaches is an important stepping-stone in helping female athletes become more in tune with their bodies.
In addition, monitoring the menstrual cycle adds an extra element to the wellness tracking that most elite clubs are already administering. These wellness surveys are designed to assess energy levels, sleep, muscle soreness and stress levels to help coaches ascertain if an athlete may need extra support or adjustments in training load. Menstrual cycle tracking is an additional wellness measure a coach should take in order to have a holistic understanding of the myriad of circumstances an athlete may be facing.
FEMALE WELLBEING
The health and wellbeing of the female athlete is an underpinning factor to performance and therefore it would be remiss to not discuss this further here. So far we have discussed the “normal” menstrual cycle of a generally healthy female, however what happens if the female’s cycle is not functioning as it should?
There are a significant number of female athletes suffering from menstrual cycle dysfunctions such as amenorrhea, which is the absence of a period or luteal phase dysfunction, which causes the female to miss the ovulation phase. Both of these issues affect 20-25% of elite female athletes and may relate to low energy availability, low body fat percentage and high training loads. This can have a significant impact on the long-term health of the female and may affect bone mineral density and fertility. The Female Athlete Triad, which has recently been changed to Relative Energy Deficiency Syndrome (REDS) is the clinical term associated with these problems and is an alarmingly common syndrome amongst younger athletes, particularly endurance athletes.
A multidisciplinary approach should be taken for an athlete suffering from REDS for example consulting a GP for testing, discussing these issues with their coach, consulting a sports dietician or naturopath for optimal energy availability strategies and becoming more in sync with their bodies by tracking symptoms across a cycle.
To learn more about the topic of menstruation and the female athlete, this is a fantastic podcast with associate professor, PHD, Clare Minahan who is a prolific researcher in this area.
