The female athlete: It's not all about performance
Elite athletes train for 365 days a year, only resting when necessary. Each season they will target their major championship, which may last only a month. Their performances are continuously judged and will influence their funding and sponsorship. For the spectators watching at home, they are presented as being at the pinnacle of health and earning a living doing what they love. But some athletes will push their bodies a little too much, resulting in disastrous long-term effects on the body and its systems.
Currently the number of females competing in sport, at all levels, is on the rise, (1) with the nation being pushed to be as healthy as it can be. All too often there is a new regime to follow that is deemed to be the ‘healthiest’ by some form of social media, a certain food to eat or not to eat, the best exercise to do or avoid. However most of these regimes posted have very little background and no valid research to back up their claims. They also tend not to highlight the potential ill effects that this restricted lifestyle could lead to.
Female athletes at an elite level tend to follow strict rules when it comes to their diet and lifestyle. They have rigid routines to ensure they meet their daily training and recovery goals to allow them to continually train for months on end. They have set foods that ensure they get the right amount of fuel needed for their training and replenish their muscles after working out. Sometimes an athlete can become so strict and set on their training goals that they lose touch with the social and emotional interactions that make us human!
There is a very fine line for the elite sportsman or woman between training, competition, and recovery (2). Elite athletes are faced with this challenge on a daily basis. For female athletes, they have an extra balance to take into consideration: the menstrual cycle.
The monthly cycles
The menstrual cycle is a natural process for females, occurring monthly, and is essential to maintain bone health and fertility. It can start from the age of 12 and continues until the onset of menopause around the age of 49-52 (3). The cycle occurs over a period of 28 days. The first 14 days are known as the follicular phase. During this phase, around day 10, the hormones oestrogen, LH (luteinizing hormone) and FSH (follicular stimulating hormone) rise, reaching their peak around day 14. LH reaches a level double that of both oestrogen and FSH. After day 14 LH levels rapidly drop off while oestrogen and FSH fall off more slowly, over a 5 day period. The second 14 days are known as the luteal phase and there is a gradual increase in another hormone, progesterone, which reaches a peak around day 22 and returns to base levels at day 28.
The cycle then repeats and continues into the next 28 day cycle. Body temperature also fluctuates during the cycle and rises by around 1-1.5 degrees Celsius during the luteal phase. LH is also linked with appetite and so the rise and fall can cause the female to feel hungrier during this time period. Oestrogen is a key regulator of bone resorption, without oestrogen there would be an excess of bone being broken down over new bone being formed , making the menstrual cycle an essential tool in maintaining bone structure.
Bone stability and structure
Bone remains in a state of constant turnover by two types of bone cells; osteoblasts and osteoclasts. (Fig 1). Osteoblasts are involved in bone formation, whereas osteoclasts are involved in bone resorption. The balance between these two types of cells is vital to maintain a steady state of bone health. Bone resorption occurs at a much higher rate than formation; bone resorption takes just 30 days whereas the bone remodelling cycle takes 4 months. Therefore, a slight imbalance can lead to a bone fracture very quickly (4).
Bone also responds to physical activity and impact. The mechanostat theory (5) describes how the mechanical strain on the bone, caused by muscle forces during contraction, activates the surface osteoblasts which begin the process of forming new bone. Continued activity causes an increase in bone mass, size, and strength, while reduced mechanical deformation causes a decrease. During puberty, bone is most responsive to physical activity so this period of life is ‘the window of opportunity’ to increase bone cross-sectional area and density. There is evidence to show that the bone mineral content of people who were active during childhood is around 8-10% greater than those that were not, even if they are both active later on in life (6).
More is not always better..
Elite female athletes, particularly those involved in sports that usually adopt a leaner physique with low body fat, are at a greater risk of disordered eating; they are more likely to disturb the balance between optimal health and recovery by reducing energy intake. Some population studies of high level female athletes have shown up to 50% of the athletes demonstrate one or more disordered eating behaviours (7). The reasons for this disordered eating could be external pressures from teams, coaches and sponsors, or the athletes themselves having the belief that the leaner and lighter they are, the quicker they will be. These pressures may also cause the athlete to push their body to further extremes. By making it difficult to match energy expenditure with energy intake, they unintentionally end up with an energy deficit. Once the athlete reaches a level of negative energy balance, detrimental effects begin to take place.
The reduced intake will not only cause weight loss but, with a lack of energy, the liver will begin to release more ketone bodies. Ketone bodies are water soluble molecules that ae released from the break-down of fatty acids, which are used as the main energy source when there is a low energy availability. A build-up of these ketones can cause the blood pH to reduce to dangerously acidic levels, a process known as ketoacidosis. Muscles will become weaker as the body starts to preserve the small amount of energy it has been given, heightening risk of injury. Without the necessary energy intake, the menstrual cycle will most likely become irregular and eventually cease, which is known as amenorrhea. Amenorrhea is as prevalent as 65% in distance runners and 69% in professional ballet dancers (7). Without a regular menstrual cycle the levels of oestrogen are significantly reduced, which causes a disproportionate level of osteoblasts and osteoclasts, leaving a higher rate of bone resorption than formation. This may ultimately lead to bone injuries, osteopenia, or even osteoporosis at a very young age, making any further career achievements even more difficult.
These three symptoms (disordered eating, amenorrhea and osteoporosis) became more prevalent in the 1990s and were termed ‘The Female Athlete Triad’ in 1997 by the American College of Sports Medicine (Fig 2). Athletes may only present with one or two of the components but this does not mean they cannot be diagnosed with the triad. It has been estimated that only 50% of trained physicians are knowledgeable about the female athlete triad and are comfortable diagnosing and treating the condition (8). More recently the triad has been renamed as RED-S (Relative energy deficient syndrome). This re-naming is due to an increased number of patients presenting with various other symptoms (chronic fatigue, irritability, depression, long-term fertility issues, reduced immunity and reduced metabolic rate). RED-S is deemed to result from continual disordered eating. Being in a state of energy deficit for a long duration can disrupt numerous physiological systems, such as, but not limited to, cardiovascular, gastrointestinal, endocrine and renal systems. Redefining the RED-S also allows male athletes who present with similar issues to be included (9).
Current research has looked at the differing effects of the components of the triad on injuries, bone health, muscle health and the different nutritional patterns. At Manchester Metropolitan University, we have carried out our own research on some of the UK’s most renowned female endurance runners, investigating the effects of altered menstrual cycle on bone health. Athletes with amenorrhea presented with a greater endocortical circumference (the outer circumference of the cortical bone) in the tibia and radius than controls. Only the eumenorrheic athletes (those with regular menstrual cycles) had a greater cortical area, in the tibia and radius, compared to controls. The athletes with amenorrhea had an expansion in bone size but not density, meaning they had wider but thinner bones.
More research is being conducted to better understand the issues, and accurate diagnosis will hopefully become more frequent. But what we really need is education at a young age, as most athletes become familiar with the triad only once they have been diagnosed with a bone injury. Prior to this, they may have never known why their menstrual cycle stopped, as it can be seen as a ‘normal’ thing to some when training at such a high level. If athletes are made aware of the symptoms and issues around the triad before they occur, then nutrition and menstrual cycles can be more closely monitored as they progress through their athletic careers. The increasing number of elite female athletes having children during their competitive careers offers hope to all younger athletes, and may even encourage them to take care of their bodies in a more informed way.
In general, female athletes do lead a healthy lifestyle and are able to balance their training needs whilst keeping their body healthy and menstrual cycle regular. When training becomes too much or a form of disordered eating is introduced, the risk for loss of menses and resulting reduced bone health becomes apparent. More research needs to be conducted to better understand the condition and allow physicians to be more confident in treating and diagnosing the condition. Ultimately, to eradicate the problem education needs to be introduced at the very start of a female athlete’s career.
Balgrove, R., Brunivels, G., Read P. (2017) Early Sport Specialization and Intensive Training in Adolescent Female Athletes: Risks and Recommendations. Strength and conditioning journal.
Barnett, A (2006). Using recovery modalities between training sessions in elite athletes does it help? Sports Med (36), 781-96
Gold E B, Bromberger J, Crawford S, Samuels S, Greendal G A, Harlow S D, Shurnick J (2001). Factors associated with age at Natural Menopause in a multiethnic sample of midlife women. American Journal of Epidemiology. (153). Pages 865-874
Agerbaek, M. O., Eriksen, E. F., Kragstrup, J., Mosekilde, L. and Melsen, F. (1991) A reconstruction of the remodelling cycle in normal human cortical iliac bone. Bone Miner, 12 (2), pp. 101-12.
Frost, H. M. (1987) 'Bone "mass" and the "mechanostat": a proposal', Anat Rec, 219(1), pp.1-9
Baxter-Jones ADG, Kontulainen SA, Faulkner RA, Bailey DA (2008) A longitudinal study of the relationship of physical activity to bone mineral accrual from adolescence to young adulthood. Bone. 43(6):1101–1107
Mountjoy, M., Sundgot-Borgen, J., Burke, L., Carter, S., Constantini, N., Lebrun, C., Meyer, N., Sherman, R., Steffen, K., Budgett, R., Ljunggvist, A. (2014). The IOC Consensus statement: beyond the female athlete triad- Relative energy deficiency in Sport (RED-S). Br J Sports Med. 48 (7): 491-7.
Curry, E, Logan, C, Ackerman, K, McInnia K, Matzkin, E (2015) Female athlete triad awareness among multispecialty Physicians. Sports Med Open. 1:38.
Tenforde, AS, Parziale, A, Popp, K, Ackerman, K. (2017) Low Bone mineral density in male athletes is associated with bone stress injuries at anatomic sites with greater trabecular composition. Am J Sports Med. DOI: 10.1177/0363546517730584
Figure 1: An adaption to show the balance between osteoblasts and osteoclasts to maintain bone health
Figure 2: An adaption to show the links between components of the female athlete triad.