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Address risk factors to prevent bone stress injuries in male and female athletes
  1. Elizabeth Anne Joy
  1. Correspondence to Dr Elizabeth Anne Joy, Community Health, Intermountain Healthcare, Salt Lake City UT 84111, USA; eajslc{at}aol.com, liz.joy{at}imail.org

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Every year in the USA, 8 million athletes participate in high school sports and 460 000 participate in intercollegiate sports.1 Sport participation is an important vehicle for many adolescents and young adults to achieve recommended levels of physical activity. High school and college athletes are more likely to meet nationally recommended levels of physical activity in comparison to non-athlete peers,2 3 and sports participation confers many health benefits not discussed here.

However, sports participation also can be a risk factor for unhealthy behaviours, high training loads and metabolic disturbances in a subset of vulnerable athletes. As the level of competition increases from high school to college, the duration and intensity of an athlete’s training typically increases. For running sports such as cross country and track and field, the transition from high school to collegiate training may result in a substantial increase in weekly running mileage. Along with this increase in training load, college athletes are exposed to changes in their dietary intake (eg, cooking for themselves or eating in a residence hall), sleep patterns (eg, staying up late studying) and even their activities of daily living (eg, walking around a larger campus compared with walking around high school)—all of which impact overall health and in particular energy availability (EA).

EA and bone health

The female athlete triad (Triad) defines the spectrums and inter-relationships of EA, menstrual status and bone mineral density (BMD).4 The Triad is more prevalent in athletes participating in sports where leanness confers a competitive advantage, such as long-distance running, and in aesthetic sports such as gymnastics and diving.5 Low EA is the underlying cause of the Triad, and it may occur with or without disordered eating or an eating disorder. Recently, a similar constellation of signs and symptoms have been observed in male athletes; consisting of low EA, low body mass index (BMI), low BMD and a higher observed rate of bone stress injuries (BSIs).6 However, in female athletes, it is often the loss of menstruation that serves as a sign that EA is insufficient. Absent a physical sign such as amenorrhoea, the diagnosis of low EA in male athletes can be more challenging.

New study informs risk assessment in male athletes

In this AMMSM issue of BJSM, Stanford University’s Emily Kraus and colleagues, studied two cohorts of male middle and long-distance runners to determine whether risk factors for BSIs previously observed in female athletes (low BMI, low EA, low BMD and prior BSI) would predict risk in male athletes. Additionally, the authors hypothesised that the risk factors would be cumulative as observed in female athletes. Overall, 42 of 156 runners (27%) sustained a BSI. Although absolute risk was low (6.4% for low EA, 5.1% with low BMI), for each 1-point increase in the cumulative risk assessment, there was a 27%–37% increased risk for BSI. This study did not assess for hormonal perturbations in males which is a finding in females who have low EA. The authors concluded that screening for low BMI, low EA, prior BSI and evaluating BMD when appropriate, can help quantify risk of future BSI. This should be done as part of the preparticipation physical evaluation. Future research is needed to determine whether hormonal abnormalities confer additional risk.

The relationship between hormonal perturbations, especially low circulating oestrogen and low BMD, is well established in postmenopausal women, females with anorexia nervosa and athletes affected by the Triad4 7 Additionally, studies have demonstrated a positive effect of oestrogen replacement on BMD.7 Considering that low EA is the underlying cause of cascading Triad conditions (menstrual dysfunction, low BMD and BSI), treatment recommendations have favoured restoration of EA over hormone replacement therapy as a primary intervention.8 However, increasing dietary energy intake, increasing BMI, and at times decreasing exercise energy expenditure in an affected athlete can be challenging due to individual resistance associated with disordered eating and eating disorders.

Innovative study tests transdermal oestrogen replacement in oligomenorrheic athletes

Recognising this challenge, Boston endocrinologist Kate Ackerman and colleagues sought to determine whether hormonal replacement in normal weight oligomenorrheic endurance athletes would impact BMD. Specifically, the authors compared the effect of physiological transdermal oestrogen replacement (and cyclic oral progesterone withdrawal) with a combined contraceptive pill/oral contraceptives. Dual-energy X-ray absorptiometry scans were performed at 6 and 12 months. The study primary endpoint was a change in BMD Z-score at the lumbar spine, comparing patch versus pill. At 12 months, patch users experienced a 2.7% increase in spine BMD, compared with only a 0.4% increase in combined contraceptive pill/oral contraceptives users and a 0.1% decrease in spine BMD among those receiving no treatment. Additional analysis found that users of the combined contraceptive pill/oral contraceptives had lower serum oestradiol levels at 6 and 12 months, confirming previous observations in athlete populations.

These two studies highlight the importance of early identification and intervention to prevent serious health consequences. Low BMD is an epidemic—more than 10 million older adults in the USA have osteoporosis (10.3% of the population of adults over age 50).9 Underlying causes for this at a population level are many, and weight-bearing exercise is protective, but as sports medicine professionals, we must be attuned to the risks that athletes face, especially those at heightened risk of low EA.

References

Footnotes

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent Not required.

  • Provenance and peer review Commissioned; internally peer reviewed.

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