Stress Fractures in the Female Athlete

I've seen my fair share of athletes who have worked through stress fractures, typically distance runners. Often in men and women alike, there was some clear precipitating factor that could explain it: typically a mad rush to cram in lost training miles. And on the periphery are the female athletes who describe a constant battle with stress fractures. These cases tend to have a less clear narrative, an inevitably more frustrating situation. Often they've been told that their low body weight was to blame. Is this true?

For female non-athletes, the message is pretty clear: you exercise to stay thin, to 'lose weight.' That's the perceived message we all get in high school, at the local gym, on TV shows like The Biggest Loser: exercise as damage control. In high school and collegiate athletics, exercise plays a different role, serving a specific training purpose, in attempts to perform stronger or faster. Unfortunately, the pervasive messages that exercise should equal weight loss or thinness puts pressure on women, even those who are athletes, to fulfill that expectation. 

Healthcare practitioners and fitness professionals alike spend a great deal of time with individuals who are less than fit, regularly exposed to people whose low levels of fitness take a toll on their quality of life. This is a problem far beyond issues of low self-esteem. In light of this, PTs advocate for physical activity for all of the 'right' reasons, but are secretly willing to accept almost any motivating factor that will get someone to the gym. What's more motivating: lowering your cholesterol or being able to wear that pair of pants?

Often, none of 'right' reasons are very sexy or compelling until pain or dysfunction comes into the picture.  Typically we joke that any motivation for getting to the gym is a good one, but sadly this is not always true: thinness and wellness are not synonymous. Concerns arise when athletes begin to prioritize their body image over their athletic performance. Is there a connection between an obsession with thinness and stress fractures in female athletes?  

My name is Dr. Allan Buccola, Owner and Physical Therapist at Impetus PT in Greensboro, NC. I've been wanting to dive into this topic for quite some time now. As a running specialist, one who focuses heavily on preventative medicine, the prevalence of stress fractures in runners remains a focal point in educating my clients and patients.

If you've ever had a stress fracture, you've likely considered shoe choice, technique, training errors, or merely bad luck...but are you missing what could perhaps be the biggest precipitating factor of them all? Let's take a look at the current available research on recurrent stress fractures in female athletes. 

What is the Female Athlete Triad? 

As frequently described in the research literature, the Female Athlete Triad is a collection of three interrelated health problems: malnutrition, changes in menstruation, and dysfunctional bone metabolism. If you are already familiar with this disorder, you may have noticed that I have avoided using other terms typically utilized to describe these three health problems: "eating disorders" and "osteoporosis." I've done this intentionally, as these terms often have stigma that frequently leads to misguided treatment or poor understanding of the problem...more of that below. 

This trio of problems can commonly be found among girls or young women that are physically active. Because each of these three problems takes place on it's own timeline, adequate screening can easily catch those at risk when only 1 or 2 of the problems are in process. Although typically associated with athletes, this condition can also extend into non athletic populations. Additionally, there is a growing body of evidence that describes a similar syndrome in males, but that is beyond the scope of this post.  

Populations At Risk

The Female Athlete Triad likely became a phenomenon as researchers began to ask why female runners have a higher incidence of stress fractures. The early research found associations with low body mass index or BMI (a crude measure of bodily thinness) and higher instances of these injuries. Immediately female runners were identified as at-risk, but this quickly extended to dancers, gymnasts, and figure skaters: athletes participating in sports with a heavy emphasis on lean physique. 

Because the Triad has strong ties to youth sports, some research has recommended that all female athletes small in stature be considered at risk. This assumption that thinness is the precipitating factor may actually provide a relatively good starting place as a first order in a multi-tiered screening process, but it has limitations.

Additional findings from my reading would indicate that females who participate in high-volumes of vigorous exercise, demonstrate caloric restrictive behaviors, or have late onset menses should also be considered strong risk factors: especially when combined with an individual who is thin.

Caloric restriction behavior, or as I mentioned above 'malnutrition,' is not the same thing as a medically diagnosed eating disorder, hence this stigma may interfere with a helpful screening process in identifying those at risk. To many who suffer from the Female Athlete Triad, there is a very large gray area between "dieting" and "anorexia." There is adequate research that shows that education with athletes and coaches alike can help make that gray area a bit smaller.

With this in mind, an eating disorder like anorexia nervosa can, in its most extreme form, provoke this same set of health problems whether the person is athletic or not. Hence, to only consider those at risk who demonstrate peculiar eating habits could be a mistake. This is often the most difficult area in which to observe risk factors in athletes, aside from immediate family, teammates, or friends. 

Trends in Treatment Strategy

Despite a strong presence in the literature, treatment strategies are often disjointed and not evidence based. I personally have organized this failure to launch for a number of big reasons. 

Reason No. 1: too heavy a reliance on the phenomenon of stress fracture rates as the problem. This is a complex disorder with wherein each of the problems have equally problematic consequences to health. The Keep Them Injury-Free movement has led campaigns of solutions based on dietary supplements, orthotics, footwear, and many other bullet dodgers, but really misses the opportunity to address this sequelae as a whole. 

Reason No. 2: Similar to the athletic angle, there is the biomedical angle wherein research has tried to identify body weight recommendations, hormonal supplements, blood tests to address, and vitamin deficiencies. Another angle seeks to identify more formalized eating disorders and utilize a dietary counseling approach solely to solve the problem.

All of these approaches offer potential solutions, but I find are more often misguided. Not all female athletic stress fractures are part of this syndrome. There is evidence to support divergent treatment methodologies for stress fractures of two different etiologies. 

Many of the popular medical treatments seek to address isolated effects of the syndrome, but have little to no evidence as a supportive treatment. A survey of physicians on this topic revealed that two of the most common treatment approaches had no supportive evidence: hormonal supplementation and calcium supplementation. 

Blind recommendations for calcium supplementation may not be the answer. Calcium supplementation was recently found to correlate strongly with an increased risk in heart disease.Additionally, another study found that women with exercise related amenonrrhea, demonstrated pathological changes to their arteries. The study also found that low BMD correlated with higher levels of calcified arterial plaques. 

Who Shall Take the Reigns?

There is no clearly designated singular profession that is fully suited to identify and treat athletes experiencing the Triad. Adequate care will require a community approach. I believe that physical therapists, athletic trainers, and coaches are uniquely positioned to address this issue through the use of awareness and education. There is research that shows moderate success in decreasing dysfunctional food behaviors via community education programs about self image and nutrition. There have also been peer-to-peer team-based mentorship programs, leading to higher rates of collegiate athletes reaching out for help.

Regardless, all healthcare practitioners from family practice physicians to registered dietitians to counselors must maintain an awareness of this disorder, but must also be well networked with other disciplines to provide multi-faceted, interdisciplinary solutions. Coaches and trainers must maintain an awareness of the Female Athlete Triad and provide consistent coaching practices that support healthy strength and conditioning ideals and body image mentality. 

Amenorrhea

The body of research on the Female Athlete Triad describes two types of menstrual changes. Oligomenorrhea is described as menstrual periods between 35-45 days apart. Amenorrhea is described as the absence of (or spotting only) menstruation for a period of 3 consecutive menstrual cycles. Both of these phenomena have been linked to significantly higher instances of stress fractures in athletes. 

The first research to emerge on this topic asserted that a simple number such as BMI could determine who was at risk for disturbance of normal menses. In other words, it was assumed that low body weight alone was perhaps a culprit. Many studies have since moved away from this idea, understanding that how thinness related to this problem was more complex.

Since then, researchers have shown that thinness is not the best indicator of stress fracture risk. There was a great study that followed around 50 collegiate track and field athletes through a season. At the end of the season, these athletes were split into two groups: those who had sustained a stress fracture and those who had not. 

The statistical analysis revealed no difference in BMI or body fat percentage between the two groups. More importantly, athletes in this study who experienced oligomenorrhea were six-times more likely to have sustained a stress fracture. The data also revealed that athletes who started menstruating at a later age were also more likely to sustain a stress fracture. This brings into question the long-term effects of menstrual dysfunction on bone health.

The widespread use of oral contraceptives in women further complicates matters. Most of these 'birth control' pills could be characterized as low-dose estrogen. According to the survey of physicians I mentioned previously, of 192 responding physicians, estrogen replacement was endorsed by 92% despite a paucity of evidence to support it. Additional studies have shown estrogen replacement to have no effect on the preservation of bone density, however the effects on the menstrual cycle were not clearly described. 

My gut tells me that as athletes move into a harder training cycle for their sport, getting on the scale may not be the best way to determine if it's time to add in some additional calories. I think some familiarity of the signs of hypoestrogenism, as well as making note of any decrease in menstruation could be the first clues that the scales have tipped. One study I came across demonstrated that the simple addition of a post workout snack of 600 calories was sufficient to maintain normal menstruation quality for the majority of participants. 

Inadequate Nutrition 

Research has revealed that in cases where caloric restriction is a prime practice, significant disturbances to the hormonal system occur. This decrease in calories can be from dieting alone, or from a sharp increase in exercise/activity without taking in additional calories. Regardless, this has been shown to increase the hormone ghrelin, which is responsible for making you feel hungry.

As ghrelin remains chronically elevated, it sends signals to the brain to decrease LH and FSH, two of the major hormones that regulate the cycle of menstruation. Estrogen decreases as well, and this state of hypoestrogenism is related to increased headaches, decreased bone mineral density, and decreased libido.

The primary concern for young girls is that the adolescent years are crucially important for the development of peak bone mineral density. For women and men alike, BMD peaks around the age of 21 and then begins to decline after the age of 30. Young women who spend their teenage and twenty something years under the shadow of the Female Athlete Triad will live their entire lives with a significantly lower bone density, leading to higher risk for osteoporosis in the postmenopausal years. 

The collegiate track athlete study aforementioned found that wherein BMI and body fat percentage were equal between those with fractures and those without, athletes who demonstrated close weight monitoring behaviors were 8x more likely to have sustained a stress fracture. There is now a growing body of research describing this complex physiological cascade of changes that take place during, what researchers now refer to as a "relative energy deficiency" in athletes.

BMI differences aside, relative energy (caloric) deficiency in athletes has been shown to be associated strongly with decreased immunity, decreased protein synthesis, lower metabolic rates at rest, decline in cardiovascular health, chronic fatigue, and depression. Another study details a sudden drop in the hormone IGF-1, a hormone produced in the liver that has a growth promoting effect on almost every tissue in the body. The authors conclude that this alone could be enough to put bones at risk for stress fracture. 

Middle to long distance runners remain at the top of the list, perhaps because of the high volume of training. One study found a strong relationship between weekly mileage and decreases in bone density at the femoral neck. Not surprisingly, this same study also found that caloric consumption was a poor predictor of training volume. 

More recently, an abundance of findings regarding the effects of relative energy deficiency on total body metabolism have motivated researchers to advocate the overlying complexities of this disorder. Some scientists are concerned that limiting the discussion to an oversimplified triad of factors does not go far enough to describe the full potential risks, nor the similarities between females and males. They stress data that show lower levels of cortisol, insulin, growth hormone, glucose, free fatty acids, and ketone bodies: an essential coup d'etat in the metabolic system. 

Somewhere between disordered eating and eating disorders

In reading through this research, it's difficult to characterize these athletes as having eating disorders. Studies focusing on the psychosocial aspects of the Triad reveal a broad continuum, ranging from good-intentioned, misinformed athletes to clinically diagnosed anorexia nervosa, bulimia, and binge-eating disorder. Without surprise, such a continuum of cases requires a variety of solutions. 

On the less extreme end stand athletes with a poor understanding of how to modify diet during vigorous training periods. With these athletes, a simple first-line solution may lie in education on the importance and determinance of adequate nutrition. Helping athletes understand the full scope of stresses on the body during peak training can help them prioritize maintenance and recovery as their body responds to conditioning. 

Exercise has been shown to be a strong appetite suppressant, so it may simply require breaking out the calculator for those who spend a great deal of time in training. I came across one study that showed that female athletes who were experiencing the Triad first-hand were only taking in 70% of their caloric expenditure. The numbers must be balanced to a degree.  

At the more extreme end stand athletes with impaired body image and a tortuous relationship with food. Help from doctors, counselors, dietitians, and perhaps others will be needed. Parents, coaches, and peers must be prepared to support athletes who are demonstrating at-risk food behaviors.

A detailed discussion about the complexities of clinical eating disorders is beyond the scope of this post, however, anyone in contact with athletes regularly in a training capacity should be able to make recommendations for clinical care and have a relationship with local professionals appropriate for treating eating disorders

Altered Bone Metabolism

If you've read this far, you have probably begun to put together the pieces of this puzzle. It has been simply impossible to have not mentioned changes to bone metabolism in relation to the malnutrition and dysmenorrhea (atypical changes to menstruation) discussed up until this point. As previously mentioned, I purposefully avoid using the term 'osteoporosis' in this context for couple of reasons.

Whereas in terms of imaging studies, and comparison of bone mineral density, and other factors, the changes to bone metabolism in the Female Athlete Triad and traditional osteoporosis that accompanies hormonal changes in postmenopausal women appear comparable. Unfortunately, the etiology and physiological processes are simply not the same. 

I bring this up for two reasons. The first is that there are female athletes that will sustain a stress fracture unrelated to the Female Athlete Triad that warrants a different set of investigative questions. In these women it makes more sense to address vitamin D or calcium deficiency, training errors, leg length discrepancy, or many others. These women will require a slightly different intervention. 

The second reason is simply that many of the studies that have attempted to address the Female Athlete Triad with these typical approaches have limited success. Several military studies have found moderate success in reduction of stress fractures with high level supplementation of vitamin D3 and calcium, but these studies did not account for caloric data, hence the findings make future application challenging.

Another 2003 study followed distance runners over a two year period with supplementation of either vitamin K or estrogen. The findings reveal a surprising decrease in BMD in all participants regardless of supplementation, with the smallest decrease found in the runners with normal menstruation status.

Vitamin D deficiency is a hot topic in the medical community right now. There is good evidence to support the need for vitamin D supplementation in typical non-athletic stress fractures. In conflict with these findings is a separate study that assessed the year-round vitamin D status in runners in the South East US, that shows that runners have adequate levels to begin with, coming back to the idea that the underlying etiology is quite different. 

The biggest reason I avoid use of the word osteoporosis is this: bone density is often assessed as normal among this at-risk population. Athletes presenting with normal bone density have been shown to still be at risk for this disorder when energy deficits have been identified. 

Spread the Word, Keep Athletes Healthy and Strong

As I am doing in writing this blog post, I encourage you to get the word out. This is an area where education is a critical preventative tool. Whether you are a coach, a parent, a teacher, or an athlete; you can make a difference. Whether you are a doctor, an athletic trainer, a dietitian, or a health enthusiast; your ability to identify this specific set of disorders is critical in finding the best, interdisciplinary treatment plan. 

Recommendations Based on Current Research

1. Be sure to take in additional calories when training ramps up. Especially after high-volume or high intensity workouts.

2. Pay close attention to frequency and consistency of menstrual patterns, and discuss them with your women's health provider if you start to notice a sudden change with an increase in activity.

3. If you have had frequent stress fractures or fluctuations in menstruation, I encourage you to take a self assessment about food behaviors. Even though this survey cannot directly diagnose an eating disorder, high scores have been validated to predict high risk for stress fractures in female athletes. It is a good place to start, and possibly an excellent way to determine if getting professional help with your food or diet would be of benefit. 

4. If you have a goal to lose weight, make it a goal to lose it slowly with regular physical activity. Avoid starvation diets and/or sudden increases vigorous workouts for the sake of accelerated weight loss. For athletes, it would seem more prudent to keep weight loss goals a focus for the off-season. During the season when training is hard on the body, prioritizing nutrition for recovery should be of prime concern. 

5. If you are a high level endurance athlete, I strongly recommend consulting with a dietitian to dial in your nutrition. I did this years ago as I began running longer distance events as a vegan, and I found it to be quite useful.

Thanks for reading this post. I hope you found it to be helpful and going forward will be able to continue to shed light on this commonly misunderstood topic. All the content in this post is strictly for the purposes of education and discussion. Having not evaluated you personally, I cannot in good conscience make blind recommendations that are safe.

If you identify as having trouble with any of the aforementioned problems, please contact a qualified healthcare provider, or contact me if you need a referral. 

Until next time, don't stop moving!

-Allan 

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