Relation between bone turnover, oestradiol, and energy balance in women distance runners

Impact of Low Energy Availability on Skeletal Health in Physically Active Adults

For decades researchers reported that pre-menopausal women who engage in extensive endurance exercise and have menstrual dysfunction can develop low bone mineral density (BMD) or osteoporosis. More recently, low energy availability has been recognized as the initiating factor for low BMD in these women. Furthermore, the relationship between low energy availability and poor skeletal health is not exclusive to women engaging in endurance exercise. Rather, both males and females commonly experience endocrine dysfunction resulting from low energy availability and high exercise levels that degrades skeletal health. Consequences to skeletal health can range from short-term changes in bone metabolism and increased risk of bone stress injuries to long-term consequences of low BMD, such as osteoporosis and related fragility fractures. The degree to which low energy availability degrades skeletal health may be dependent on the length and extent of the energy deficit. However, the complex relationships between under-fueling, short- and long-term skeletal consequences and the factors that mediate these relationships are not well described. In this review, we discuss the consequences of low energy availability on sex hormones and skeletal health in two highly-active populations-athletes and military trainees-and provide a summary of existing knowledge gaps for future study.

A Life History Perspective on Athletes with Low Energy Availability

The energy costs of athletic training can be substantial, and deficits arising from costs unmet by adequate energy intake, leading to a state of low energy availability, may adversely impact athlete health and performance. Life history theory is a branch of evolutionary theory that recognizes that the way the body uses energy-and responds to low energy availability-is an evolved trait. Energy is a finite resource that must be distributed throughout the body to simultaneously fuel all biological processes. When energy availability is low, insufficient energy may be available to equally support all processes. As energy used for one function cannot be used for others, energetic "trade-offs" will arise. Biological processes offering the greatest immediate survival value will be protected, even if this results in energy being diverted away from others, potentially leading to their downregulation. Athletes with low energy availability provide a useful model for anthropologists investigating the biological trade-offs that occur when energy is scarce, while the broader conceptual framework provided by life history theory may be useful to sport and exercise researchers who investigate the influence of low energy availability on athlete health and performance. The goals of this review are: (1) to describe the core tenets of life history theory; (2) consider trade-offs that might occur in athletes with low energy availability in the context of four broad biological areas: reproduction, somatic maintenance, growth, and immunity; and (3) use this evolutionary perspective to consider potential directions for future research.

Recommendations and Nutritional Considerations for Female Athletes: Health and Performance

Optimal nutrition is an important aspect of an athlete’s preparation to achieve optimal health and performance. While general concepts about micro- and macronutrients and timing of food and fluids are addressed in sports science, rarely are the specific effects of women’s physiology on energy and fluid needs highly considered in research or clinical practice. Women differ from men not only in size, but in body composition and hormonal milieu, and also differ from one another. Their monthly hormonal cycles, with fluctuations in estrogen and progesterone, have varying effects on metabolism and fluid retention. Such cycles can change from month to month, can be suppressed with exogenous hormones, and may even be manipulated to capitalize on ideal timing for performance. But before such physiology can be manipulated, its relationship with nutrition and performance must be understood. This review will address general concepts regarding substrate metabolism in women versus men, common menstrual patterns of female athletes, nutrient and hydration needs during different phases of the menstrual cycle, and health and performance issues related to menstrual cycle disruption. We will discuss up-to-date recommendations for fueling female athletes, describe areas that require further exploration, and address methodological considerations to inform future work in this important area.

The Bone Metabolic Response to Exercise and Nutrition

Bone (re)modeling markers can help determine how the bone responds to different types, intensities, and durations of exercise. They also might help predict those at risk of bone injury. We synthesized evidence on the acute and chronic bone metabolic responses to exercise, along with how nutritional factors can moderate this response. Recommendations to optimize future research efforts are made.

Using physical activity levels to estimate energy requirements of female athletes

[Purpose]

The goal of this study was to review data on physical activity level (PAL), a crucial index for determining estimated energy requirement (EER), calculated as total energy expenditure (TEE, assessed with doubly labeled water [DLW]) divided by resting metabolic rate (RMR, PAL = TEE/RMR) in female athletes and to understand the methods of assessing athletes’ EERs in the field.

[Methods]

For the PAL data review among female athletes, we conducted a PubMed search of the available literature related to the DLW method. DLW studies measuring TEE and RMR were included for the present review.

[Results]

Briefly, the mean PAL was 1.71 for collegiate swimmers with moderate training, which was relatively low, but the mean PAL was 3.0 for elite swimmers during summer training camp. This shows that PAL can largely vary even within the same sport depending on the amount of training, and the differences in PAL were remarkable depending on the sport. Aside from the DLW method, there is currently no research tool related to athletes’ EERs that can be used in the field.

[Conclusion]

Briefly, the mean PAL was 1.71 for collegiate swimmers with moderate training, which was relatively low, but the mean PAL was 3.0 for elite swimmers during summer training camp. This shows that PAL can largely vary even within the same sport depending on the amount of training, and the differences in PAL were remarkable depending on the sport. Aside from the DLW method, there is currently no research tool related to athletes’ EERs that can be used in the field.

Risk factors of stress fractures due to the female athlete triad: Differences in teens and twenties

BACKGROUND

The female athlete triad (Triad), defined by the American College of Sports Medicine as low energy availability (LEA) with or without disordered eating, menstrual dysfunction, and low bone mineral density (BMD), is associated with stress fractures and athletes aged 16-17 years are most susceptible.

PURPOSE

To examine whether the Triad increases the risk of stress fractures, athletes were assigned to a "teenage" group and a "20s" group.

METHODS

This prospective study enrolled 390 elite female athletes and was conducted from 2012 to 2016 at Japan Institute of Sports Sciences. Blood concentrations of various hormones were examined, and BMD was measured at the lumbar spine and throughout the whole body using dual-energy X-ray absorptiometry. LEA was defined as body weight ≤85% of the ideal body weight for teenage athletes, or BMI ≤17.5 for athletes in their 20s. Low BMD was defined as a BMD Z-score of <-1.0 in the lumbar spine and the whole body.

RESULTS

Among 390 athletes enrolled, 36 developed new stress fractures within 3 months of registration. The risk for stress fractures due to the Triad in teenage athletes was higher than for athletes in their 20s. In teenage female athletes, secondary amenorrhea, low BMD for the whole body, and a low ratio of actual body weight to ideal body weight increased the risk for stress fractures by 12.9 times, 4.5 times, and 1.1 times, respectively.

CONCLUSION

To prevent stress fractures in female athletes with the Triad, age of athletes should be taken into consideration.

Reduced energy availability: implications for bone health in physically active populations

Purpose

The present review critically evaluates existing literature on the effects of short- and long-term low energy availability (EA) on bone metabolism and health in physically active individuals.

Methods

We reviewed the literature on the short-term effects of low EA on markers of bone metabolism and the long-term effects of low EA on outcomes relating to bone health (bone mass, microarchitecture and strength, bone metabolic markers and stress fracture injury risk) in physically active individuals.

Results

Available evidence indicates that short-term low EA may increase markers of bone resorption and decrease markers of bone formation in physically active women. Bone metabolic marker responses to low EA are less well known in physically active men. Cross-sectional studies investigating the effects of long-term low EA suggest that physically active individuals who have low EA present with lower bone mass, altered bone metabolism (favouring bone resorption), reduced bone strength and increased risk for stress fracture injuries.

Conclusions

Reduced EA has a negative influence on bone in both the short- and long-term, and every effort should be made to reduce its occurrence in physically active individuals. Future interventions are needed to explore the effects of long-term reduced EA on bone health outcomes, while short-term low EA studies are also required to give insight into the pathophysiology of bone alterations.

Low bone density risk is higher in exercising women with multiple triad risk factors

The cumulative effect of the female athlete triad (Triad) risk factors on the likelihood of low bone mineral density (BMD) in exercising women is unclear.

PURPOSE

This study aimed to determine the risk of low BMD in exercising women with multiple Triad risk factors.

METHODS

We retrospectively examined cross-sectional data from 437 exercising women (mean ± SD age of 18.0 ± 3.5 yr, weighed 57.5 ± 7.1 kg with 24.5% ± 6.1% body fat) obtained at baseline from 4 prospective cohort studies examining Triad risk factors. Questionnaires were completed to obtain information on demographic characteristics, self-reported eating attitudes/behaviors, menstrual function, sport/activity participation, and medication use. Height and body weight were measured. BMD was measured using dual energy x-ray absorptiometry. Low BMD was defined as z-scores of <-1 and ≤-2. Chi-square tests were performed to determine the percentage of women with low BMD who met the criteria for individual (current oligo/amenorrhea, late menarche, low body mass index (BMI), elevated dietary restraint, lean sport/activity participation) or multiple (2, 3, 4, or 5) Triad risk factors.

RESULTS

Late menarche and low BMI were associated with the highest percentage of low BMD (z-score < -1), 55% and 54%, respectively, and low BMD (z-score ≤-2), 14% and 16%, respectively. The percentage of participants with low BMD (z-score < -1 and ≤-2) increased from 10% to 62% and from 2% to 18%, respectively, as women met the criteria for an increasing number of Triad risk factors.

CONCLUSIONS

A cumulative number of Triad risk factors were associated with an increased risk of low BMD, suggesting a dose-response association between the number of Triad risk factors and BMD in exercising women. Further research should be conducted to develop a user-friendly algorithm integrating these indicators of risk for low BMD in exercising women (particularly factors associated with low BMI/body weight, menstrual dysfunction, lean sport/activity participation, and elevated dietary restraint).

Dietary intervention restored menses in female athletes with exercise-associated menstrual dysfunction with limited impact on bone and muscle health

Exercise-related menstrual dysfunction (ExMD) is associated with low energy availability (EA), decreased bone mineral density (BMD), and increased risk of musculoskeletal injury. We investigated whether a 6-month carbohydrate-protein (CHO-PRO) supplement (360 kcal/day, 54 g CHO/day, 20 g PRO/day) intervention would improve energy status and musculoskeletal health and restore menses in female athletes (n = 8) with ExMD. At pre/post-intervention, reproductive and thyroid hormones, bone health (BMD, bone mineral content, bone markers), muscle strength/power and protein metabolism markers, profile of mood state (POMS), and energy intake (EI)/energy expenditure (7 day food/activity records) were measured. Eumenorrheic athlete controls with normal menses (Eumen); n = 10) were measured at baseline. Multiple linear regressions were used to evaluate differences between groups and pre/post-intervention blocking on participants. Improvements in EI (+382 kcal/day; p = 0.12), EA (+417 kcal/day; p = 0.17) and energy balance (EB; +466 kcal/day; p = 0.14) were observed with the intervention but were not statistically significant. ExMD resumed menses (2.6 ± 2.2-months to first menses; 3.5 ± 1.9 cycles); one remaining anovulatory with menses. Female athletes with ExMD for >8 months took longer to resume menses/ovulation and had lower BMD (low spine (ExMD = 3; Eumen = 1); low hip (ExMD = 2)) than those with ExMD for <8 months; for 2 ExMD the intervention improved spinal BMD. POMS fatigue scores were 15% lower in ExMD vs. Eumen (p = 0.17); POMS depression scores improved by 8% in ExMD (p = 0.12). EI, EA, and EB were similar between groups, but the intervention (+360 kcal/day) improved energy status enough to reverse ExMD despite no statistically significant changes in EI. Similar baseline EA and EB between groups suggests that some ExMD athletes are more sensitive to EA and EB fluctuations.

Bone mineral density, rib pain and other features of the female athlete triad in elite lightweight rowers

OBJECTIVE

To determine bone mineral density (BMD) and the associations among BMD, menstrual history, disordered eating (DE), training history, intentional weight loss (IWL) and rib pain for the first time in female lightweight rowers.

SETTING

9 lightweight rowing clubs, UK.

PARTICIPANTS

29 Caucasian female lightweight rowers volunteered. 21 (12 active, 9 retired) completed the study.

INCLUSION CRITERIA

female lightweight rowers aged over 18 years.

EXCLUSION CRITERIA

participants with a history of bone disease, used medications known to influence BMD or if they were pregnant, lactating or postmenopausal.

MAIN OUTCOME MEASURES

Dual-energy X-ray absorptiometry measured total body (TB) composition and BMD at the spine, femoral neck (FN), radius and TB. DE, oligomenorrhoea/amenorrhoea years; rib pain and training history.

RESULTS

DE was reported in six of the rowers. The active with DE started rowing younger (p<0.05) than those without, and their amount of IWL was associated with Eating Attitudes Test-26 score (p<0.05). Some participants reported a history of oligomenorrhoea/amenorrhoea 17 (76%) and/or rib pain 7 (32%) with those with rib pain having lower spine and TB Z-scores (p<0.05) than those without. Those with oligomenorrhoea/amenorrhoea had lower spine Z-scores (p<0.01) than those without. Twelve participants had low BMD; three at spine; one at FN; and eight at radius. Thirteen per cent of mean total training hours (18.6±9.1 h/week) were spent strength training (2.4±2.2 h/week).

CONCLUSIONS

Upper body exercises incorporating multidimensional high peak bone strain were not reported and may need to be considered in their strength training to improve radial BMD. Results suggest IWL and high-level training at a young age increases the likelihood of DE and there may be a lack of quality nutritional support for these athletes. Thus, multidisciplinary sport science support should be offered at a young age and perhaps also to consider changing the weight rules to prevent the development of the Triad.

Body composition and reproductive function exert unique influences on indices of bone health in exercising women

Reproductive function, metabolic hormones, and lean mass have been observed to influence bone metabolism and bone mass. It is unclear, however, if reproductive, metabolic and body composition factors play unique roles in the clinical measures of areal bone mineral density (aBMD) and bone geometry in exercising women. This study compares lumbar spine bone mineral apparent density (BMAD) and estimates of femoral neck cross-sectional moment of inertia (CSMI) and cross-sectional area (CSA) between exercising ovulatory (Ov) and amenorrheic (Amen) women. It also explores the respective roles of reproductive function, metabolic status, and body composition on aBMD, lumbar spine BMAD and femoral neck CSMI and CSA, which are surrogate measures of bone strength. Among exercising women aged 18-30 years, body composition, aBMD, and estimates of femoral neck CSMI and CSA were assessed by dual-energy x-ray absorptiometry. Lumbar spine BMAD was calculated from bone mineral content and area. Estrone-1-glucuronide (E1G) and pregnanediol glucuronide were measured in daily urine samples collected for one cycle or monitoring period. Fasting blood samples were collected for measurement of leptin and total triiodothyronine. Ov (n = 37) and Amen (n = 45) women aged 22.3 ± 0.5 years did not differ in body mass, body mass index, and lean mass; however, Ov women had significantly higher percent body fat than Amen women. Lumbar spine aBMD and BMAD were significantly lower in Amen women compared to Ov women (p < 0.001); however, femoral neck CSA and CSMI were not different between groups. E1G cycle mean and age of menarche were the strongest predictors of lumbar spine aBMD and BMAD, together explaining 25.5% and 22.7% of the variance, respectively. Lean mass was the strongest predictor of total hip and femoral neck aBMD as well as femoral neck CSMI and CSA, explaining 8.5-34.8% of the variance. Upon consideration of several potential osteogenic stimuli, reproductive function appears to play a key role in bone mass at a site composed of primarily trabecular bone. However, lean mass is one of the most influential predictors of bone mass and bone geometry at weight-bearing sites, such as the hip.

Female Athlete Triad

The passage of Title IX in 1972 resulted in a tremendous increase in the number of females participating in high school and collegiate athletics. This rise in female athletes sparked new focus areas of research in sports medicine related to woman with an important area emerging in 1980, the female athlete triad. This triad consisting of low energy availability, menstrual irregularities, and bone health disruption spans a spectrum of severity and has evolved both in diagnosis and in management throughout the years. Many health questions arise for female athletes and their health care providers, often concerning the most effective management and treatment strategies for this triad. This review examines the research and latest advancements in recognizing and understanding the female athlete triad and explores the most current recommendations for treatment and prevention.

The effects of delayed puberty on the growth plate

BACKGROUND

Many athletes are beginning intense training before puberty, a time of increased bone accrual when up to 25% of total bone mineral accrual occurs. Female athletes experiencing late or delayed pubertal onset may have open epiphyseal plates that are vulnerable to injury. This investigation's purpose was to determine whether a delay in puberty (primary amenorrhea) affects the growth plate immediately postpuberty and at maturity.

METHODS

Forty-eight female Sprague-Dawley rats (23 d old) were randomly assigned to 4 groups (n=12); short-term control (C-ST), long-term control (C-LT), short-term GnRH antagonist (G-ST), and long-term GnRH antagonist (G-LT). At 25 days of age, daily gonadotropin-releasing hormone antagonist (GnRH-a) injections were administered delaying pubertal onset. Left tibias were analyzed. Stained frontal slices of proximal tibia (5 µm thick) were analyzed in hypertrophic, proliferative, and reserve zones for total height, zone height, and cell/column counts. All procedures were approved by Institutional Animal Care and Use Committee at Brooklyn College.

RESULTS

Growth plate height was 19.7% wider in delayed puberty (G-ST) group and at maturity was 27.9% greater in G-LT group compared with control (C-LT) (P<0.05). No significant differences were found in short-term or long-term growth plate zone heights or cell/column counts between groups (P>0.05). Growth plate zone height normalized to total height resulted in 28.7% larger reserve zone in the short-term GnRH-a group but the proliferative zone was 8.5% larger in the long-term group compared with the control group (P<0.05). Normalized to growth plate height a significant decrease was found in column counts in proliferative zones of the short-term and long-term GnRH-a groups.

CONCLUSIONS

Current data illustrate that delayed puberty using GnRH-a injections results in significant growth plate height and decreases proliferative column counts and zone height, thus potentially contributing to decreases in bone mass at maturity.

CLINICAL RELEVANCE

Growth plate height increases indicate increased potential for growth and bone accrual. However, previous models report decreased bone volume following delayed puberty via GnRH-a injections that may have detrimental effects in the long term.

Obstacles in the optimization of bone health outcomes in the female athlete triad

Maintaining low body weight for the sake of performance and aesthetic purposes is a common feature among young girls and women who exercise on a regular basis, including elite, college and high-school athletes, members of fitness centres, and recreational exercisers. High energy expenditure without adequate compensation in energy intake leads to an energy deficiency, which may ultimately affect reproductive function and bone health. The combination of low energy availability, menstrual disturbances and low bone mineral density is referred to as the 'female athlete triad'. Not all athletes seek medical assistance in response to the absence of menstruation for 3 or more months as some believe that long-term amenorrhoea is not harmful. Indeed, many women may not seek medical attention until they sustain a stress fracture. This review investigates current issues, controversies and strategies in the clinical management of bone health concerns related to the female athlete triad. Current recommendations focus on either increasing energy intake or decreasing energy expenditure, as this approach remains the most efficient strategy to prevent further bone health complications. However, convincing the athlete to increase energy availability can be extremely challenging. Oral contraceptive therapy seems to be a common strategy chosen by many physicians to address bone health issues in young women with amenorrhoea, although there is little evidence that this strategy improves bone mineral density in this population. Assessment of bone health itself is difficult due to the limitations of dual-energy X-ray absorptiometry (DXA) to estimate bone strength. Understanding how bone strength is affected by low energy availability, weight gain and resumption of menses requires further investigations using 3-dimensional bone imaging techniques in order to improve the clinical management of the female athlete triad.

Different effects on bone strength and cell differentiation in pre pubertal caloric restriction versus hypothalamic suppression

Hypothalamic amenorrhea and energy restriction during puberty affect peak bone mass accrual. One hypothesis suggests energy restriction alters hypothalamic function resulting in suppressed estradiol levels leading to bone loss. However, both positive and negative results have been reported regarding energy restriction and bone strength. Therefore, the purpose of this study was to investigate energy restriction and hypothalamic suppression during pubertal onset on bone mechanical strength and the osteogenic capacity of bone marrow-derived cells in two models: female rats treated with gonadotropin releasing hormone antagonists (GnRH-a) or 30% energy restriction. At 23 days of age, female Sprague Dawley rats were assigned to three groups: control group (C, n=10), GnRH-a group (n=10), and Energy Restriction (ER, n=12) group. GnRH-a animals received daily injections for 27 days. The animals in the ER group received 70% of the control animals' intake. After sacrifice (50 days of age), body weight, uterine and muscle weights were measured. Bone marrow-derived stromal cells were cultured and assayed for proliferation and differentiation into osteoblasts. Outcome measures included bone strength, bone histomorphometry and architecture, serum IGF-1 and osteocalcin. GnRH-a suppressed uterine weight, decreased osteoblast proliferation, bone strength, trabecular bone volume and architecture compared to control. Elevated serum IGF-1 and osteocalcin levels and body weight were found. The ER model had an increase in osteoblast proliferation compared to the GnRH-a group, similar bone strength relative to body weight and increased trabecular bone volume in the lumbar spine compared to control. The ER animals were smaller but had developed bone strength sufficient for their size. In contrast, suppressed estradiol via hypothalamic suppression resulted in bone strength deficits and trabecular bone volume loss. In summary, our results support the hypothesis that during periods of nutritional stress the increased vertebral bone volume may be an adaptive mechanism to store mineral which differs from suppressed estradiol resulting from hypothalamic suppression.

Bone Metabolism Markers in Sportswomen with Menstrual Cycle Dysfunctions

It is a well known fact that sportswomen with irregular menstrual cycle are exposed to the risk of diminished bone mineral density, and consequentially osteoporosis may appear. Monitoring of the levels of biochemical markers of bone metabolism enables understanding of the dynamic changes during the bone remodeling process. The objectives of the conducted research were to determine the prevalence of menstrual dysfunctions in a sports-women sample and a control group, and also to determine the levels of bone metabolism markers in groups of women with menstrual dysfunctions. The women (n=117) were separated into two groups, the experimental group (S) (n=84) comprised of three subgroups of sports women (34 women who play ball game sports, 27 athletes and 23 sport dancers) and the control group (C) (n=34). To establish the menstrual profile and dysfunction of the menstrual cycle, we used a very detailed questionnaire. The level of mid-fragment osteocalcin (N-MID osteocalcin) as a marker of bone formation was deter mined, as well as β-Cross Laps (β-CTx-bone resorption marker) via the electro luminescent immunochemistry method on an Elecsys 1010 automated machine. Primary amenorrhea was found in 7 (8.33%) and oligomenorrhea in 11 (13.09%) sportswomen, which was statistically a much higher incidence (p<0.05) than in the control group (0/34). Values of bone metabolism markers showed a statistically significant difference in the level of the bone resorption marker β-CrossLaps between the groups of amenorrheic and oligomenorrheic sportswomen in comparison to the eumenorrheic women, both sportswomen and those in the control group. Accelerated resorption was accompanied with accelerated bone formation. Menstrual dysfunctions were statistically more present in the sports-women group than in the control group and were accompanied with accelerated bone metabolism from the point of view of the increase of bone metabolism markers level.

Physiologic and behavioral indicators of energy deficiency in female adolescent runners with elevated bone turnover

BACKGROUND

Female adolescent runners have an elevated prevalence of low bone mass for agemdashan outcome that may be partially due to inadequate energy intake.

OBJECTIVE

The objective was to evaluate diet, menstrual history, serum hormone concentrations, and bone mass in female adolescent runners with normal or abnormal bone turnover.

DESIGN

Thirty-nine cross-country runners (age: 15.7 plusmn 0.2 y) participated in the study, which included a 7-d dietary assessment with the use of a food record and daily 24-h dietary recalls; serum measures of insulin-like growth factor I, estradiol, leptin, parathyroid hormone, progesterone, triiodothyronine, 25-hydroxycholecalciferol, bone-specific alkaline phosphatase (BAP), and cross-linked C-telopeptides of type I collagen (CTX); an evaluation of height, weight, bone mass, and body composition with the use of dual-energy X-ray absorptiometry; and a questionnaire to assess menses and sports participation. Age- and sex-specific BAP and CTX concentrations of at least the 97th percentile and no greater than the third percentile, respectively, were considered abnormal.

RESULTS

All abnormal BAP and CTX concentrations fell within the elevated ( ge 97%) range. Runners with an elevated bone turnover (EBT) (n = 13) had a lower body mass, fewer menstrual cycles in the past year, lower estradiol and 25-hydroxycholecalciferol concentrations, and a higher prevalence of body mass index lt 10% for age, vitamin D insufficiency, amenorrhea, and low bone mass. Girls with EBT consumed less than the recommended amounts of energy and had a higher prevalence of consuming lt 1300 mg Ca than did those with normal bone turnover.

CONCLUSIONS

Runners with EBT had a profile consistent with energy deficiency. Nutritional support to increase energy, calcium intake, and 25-hydroxycholecalciferol concentrations may improve bone mineral accrual in young runners with EBT. This trial was registered at clinicaltrials.gov as NCT01059968.

Cross-sectional evidence of suppressed bone mineral accrual among female adolescent runners

We aimed to evaluate patterns of bone mineral accrual among a cross-sectional sample of female adolescent runners and girls participating in a nonendurance running sport. One-hundred and eighty-three interscholastic competitive female athletes (age 16.0 +/- 0.1 years), 93 endurance runners and 90 nonrunners, completed a menstrual and sports history questionnaire, had their height and weight measured, and underwent a dual-energy X-ray absorptiometry scan for the measurements of body composition and bone mass. For the majority of analyses, the girls were separated into four groups according to their age (13 to 14 years, 15 years, 16 years, and 17 to 18 years). Runners' height, weight, body mass index (BMI), percent body fat, lean tissue mass, number of menstrual cycles in the past year, and months of participation in a non-lean-build/variable-impact-loading sport were significantly lower than mean values for nonrunners. Although bone mass rose at all sites in the nonrunners between the ages of 13 to 14 years and 17 to 18 years, no such increase was noted in the runners. Runners compared with nonrunners exhibited significantly lower body weight and height-adjusted total body and lumbar spine bone mineral content (BMC) values and lower bone mineral density (BMD) Z-score values among the older (16 years and/or 17 to 18 years) but not younger (13 to 14 years and/or 15 years) age groups. These findings suggest that the runners, in contrast to the nonrunners, exhibited a suppressed bone mineral accrual pattern, which supports the notion that female adolescent endurance runners may be at risk for inadequate bone mass gains and thus a low peak BMD.

Anorexia, bulimia, and the female athlete triad: evaluation and management

The female athlete triad is an increasingly prevalent condition involving disordered eating, amenorrhea, and osteoporosis. An athlete can suffer from all 3 components of the triad, or just 1 or 2 of the individual conditions. The main element underlying all the aspects of the triad is an adaptation to a negative caloric balance. Screening for these disorders should be an important component of an athlete's care. Prevention and treatment should involve a team approach, including a physician, a nutritionist, and a mental health provider.

The female athlete triad: components, nutrition issues, and health consequences

This paper, which was part of the International Association of Athletics Federations (IAAF) 2007 Nutritional Consensus Conference, briefly reviews the components of the female athlete triad (Triad): energy availability, menstrual status, and bone health. Each component of the Triad spans a continuum from health to disease, and female athletes can have symptoms related to each component of the Triad to different degrees. Low energy availability is the primary factor that impairs menstrual dysfunction and bone health in the Triad. We discuss nutritional issues associated with the Triad, focusing on intakes of macronutrients needed for good health, and stress fractures, the most common injury associated with the Triad. Finally, we briefly discuss screening and treatment for the Triad and the occurrence of the Triad in men.

Exercise-induced amenorrhea and bone health in the adolescent athlete

Female participation in high school athletics has increased 800% in the last 30 years. The problem of exercise-induced amenorrhea was initially thought to be analogous to hypoestrogenism, but recent studies suggest that nutritional issues underlie most of the pathophysiology and that the mechanism is different from that seen in the primary hypogonadal state. Exercise-induced amenorrhea can be an indicator of an energy drain, and the presence of the other components of the female athlete triad-bone density loss and eating disorders-must be determined as well. Addressing skeletal problems related to nutritional and hormonal deficiencies in this population is of very high priority.

Recovery of bone mineral density and fertility in a former amenorrheic athlete

Inadequate dietary intake and prolonged amenorrhea in women athletes can lead to bone loss, particularly at the spine, which may be irreversible. This report presents the case of a woman endurance runner, followed prospectively over 6 years after presenting with the female athlete triad. Bone mineral density (BMD) and body composition were assessed by dual-energy X-ray absorptiometry. At baseline, lumbar spine (LS), total hip and total body (TB) BMD Z-scores were -2.2, -0.5 and -0.3 respectively. At 6 years, following a recovery plan of cognitive behavioural therapy (CBT), weight gain, improved dietary intake and reduced training load, the athlete regained menstrual function and BMD. LS, TB and hip BMD Z-scores improved to -0.6, -0.1 and 0.1 respectively. Restoration of fertility was indicated by pregnancy, following only 4 months of regular menstruation. This case report suggests that bone density and fertility may not be completely jeopardised in formerly amenorrheic and osteopenic athletes, providing recovery through diet, weight gain, and return of menstruation is achieved within the third decade. Longitudinal studies tracking bone changes in women with amenorrhea and low BMD are required and would have important implications for the treatment of the female athlete triad. Key pointsPeak bone mass and fertility may not be completely jeopardised in women athletes providing recovery is attained in the third decade.Recovery from the Female Athlete Triad in this case involved weight gain, improved diet and a return of menstruation, and appeared to be encouraged by cognitive behavioural therapy (CBT).Further longitudinal studies are warranted to inform on prognosis and to aid in the identification of strategies for recovery from the Triad.

The presence of both an energy deficiency and estrogen deficiency exacerbate alterations of bone metabolism in exercising women

BACKGROUND

Bone loss in amenorrheic athletes has been attributed to energy deficiency-related suppression of bone formation, but not increased resorption despite hypoestrogenism.

OBJECTIVE

To assess the independent and combined effects of energy deficiency and estrogen deficiency on bone turnover markers in exercising women.

DESIGN

PINP, osteocalcin, U-CTX-I, TT3, leptin, and ghrelin were measured repeatedly, and bone mineral density (BMD) was measured once in 44 exercising women. Resting energy expenditure (REE) was used to determine energy status (deficient or replete) and was corroborated with measures of metabolic hormones. Daily levels of urinary estrone and pregnanediol glucuronides (E1G, PdG), were assessed to determine menstrual and estrogen status. Volunteers were then retrospectively categorized into 4 groups: 1) Energy Replete+Estrogen Replete (EnR+E2R), (n=22), 2) Energy Replete+Estrogen Deficient (EnR+E2D), (n=7), 3) Energy Deficient+Estrogen Replete (EnD+E2R), (n=7), and 4) Energy Deficient+Estrogen Deficient (EnD+E2D), (n=8).

RESULTS

The groups were similar (p>0.05) with respect to age (24.05+/-1.75 yrs), weight (57.7+/-2.2 kg), and BMI (21.05+/-0.7 kg/m2). By design, REE/FFM (p=0.028) and REE:pREE (p<0.001) were lower in the EnD vs. EnR group, and the E2D group had a lower REE:pREE (p=0.005) compared to the E2R group. The EnD+E2D group had suppressed PINP (p=0.034), and elevated U-CTX-I (p=0.052) and ghrelin (p=0.028) levels compared to the other groups. These same women also had convincing evidence of energy conservation, including TT3 levels that were 29% lower (p=0.057) and ghrelin levels that were 44% higher (p=0.028) than that observed in the other groups. Energy deficiency was associated with suppressed osteocalcin, and TT3 (p<0.05), whereas estrogen deficiency was associated with decreased E1G (p<0.02), and lower L2-L4 BMD (p=0.033). Leptin was significant in predicting markers of bone formation, but not markers of bone resorption.

CONCLUSIONS

When the energy status of exercising women was adequate (replete), there were no apparent perturbations of bone formation or resorption, regardless of estrogen status. Estrogen deficiency in exercising women, in the presence of an energy deficiency, was associated with bone loss and involved suppressed bone formation and increased bone resorption. These findings underscore the importance of avoiding energy deficiency, which is associated with hypoestrogenism, to avoid bone health problems.

Bone density and young athletic women. An update

High-school girls and collegiate women have tremendous opportunities to participate in athletic teams. Young girls are also playing in club and select teams at an early age and often, year-round. There are many benefits for participating in sport and physical activity on both the physical and mental health of girls and women. Decreased risk for heart disease and diabetes mellitus, along with improved self-esteem and body-image, were among the first reported benefits of regular physical activity. In addition, sport participation and physical activity is also associated with bone health. Athletes have a greater bone mineral density compared with non-active and physically active females. The increase in bone mass should reduce the risk of fragility fractures in later life. There appears to be a window of opportunity during the development of peak bone mass in which the bone is especially responsive to weight-bearing physical activity. Impact loading sports such as gymnastics, rugby or volleyball tend to produce a better overall osteogenic response than sports without impact loading such as cycling, rowing and swimming. Relatively little is known about the impact of retiring from athletics on bone density. It appears that former athletes continue to have a higher bone density than non-athletes; however, the rate of bone loss appears to be similar in the femoral neck. The positive impact of sports participation on bone mass can be tempered by nutritional and hormonal status. It is not known whether female athletes need additional calcium compared with the general female population. Due to the increased energy expenditure of exercise and/or the pressure to obtain an optimal training bodyweight, some female athletes may develop low energy availability or an eating disorder and subsequently amenorrhoea and a loss of bone mineral density. The three inter-related clinical disorders are referred to as the 'female athlete triad'. This article presents a review of the relationship between sports training and bone health, specifically bone mineral density, in young athletic women.

Independent and combined effect of nutrition and exercise on bone mass development

Food intake provides the necessary components for adequate metabolic functions in bone. Calcium, phosphorus, vitamin D, magnesium, proteins, and fluoride are some of the most important nutrients in this regard. These have different effects on bone mass. Additionally, exercise has been shown to elicit osteogenic responses in bone development; indeed, it seems to potentiate, for example, the effect of calcium supplementation on bone mass. However, the nutrition-exercise-bone mass relationship is complex and needs further in-depth investigation. As a first step, therefore, we reviewed current knowledge about the role of nutrition on the development of bone tissue and how physical activity affects the nutrient-bone relationship.

Risk factors for stress fracture among young female cross-country runners

PURPOSE

To identify risk factors for stress fracture among young female distance runners.

METHODS

Participants were 127 competitive female distance runners, aged 18-26, who provided at least some follow-up data in a randomized trial among 150 runners of the effects of oral contraceptives on bone health. After completing a baseline questionnaire and undergoing bone densitometry, they were followed an average of 1.85 yr.

RESULTS

Eighteen participants had at least one stress fracture during follow-up. Baseline characteristics associated (P<0.10) in multivariate analysis with stress fracture occurrence were one or more previous stress fractures (rate ratio [RR] [95% confidence interval]=6.42 (1.80-22.87), lower whole-body bone mineral content (RR=2.70 [1.26-5.88] per 1-SD [293.2 g] decrease), younger chronologic age (RR=1.42 [1.05-1.92] per 1-yr decrease), lower dietary calcium intake (RR=1.11 [0.98-1.25] per 100-mg decrease), and younger age at menarche (RR=1.92 [1.15-3.23] per 1-yr decrease). Although not statistically significant, a history of irregular menstrual periods was also associated with increased risk (RR=3.41 [0.69-16.91]). Training-related factors did not affect risk.

CONCLUSION

The results of this and other studies indicate that risk factors for stress fracture among young female runners include previous stress fractures, lower bone mass, and, although not statistically significant in this study, menstrual irregularity. More study is needed of the associations between stress fracture and age, calcium intake, and age at menarche. Given the importance of stress fractures to runners, identifying preventive measures is of high priority.

The Female Athlete Triad

The female athlete triad (Triad) refers to the interrelationships among energy availability, menstrual function, and bone mineral density, which may have clinical manifestations including eating disorders, functional hypothalamic amenorrhea, and osteoporosis. With proper nutrition, these same relationships promote robust health. Athletes are distributed along a spectrum between health and disease, and those at the pathological end may not exhibit all these clinical conditions simultaneously. Energy availability is defined as dietary energy intake minus exercise energy expenditure. Low energy availability appears to be the factor that impairs reproductive and skeletal health in the Triad, and it may be inadvertent, intentional, or psychopathological. Most effects appear to occur below an energy availability of 30 kcal.kg(-1) of fat-free mass per day. Restrictive eating behaviors practiced by girls and women in sports or physical activities that emphasize leanness are of special concern. For prevention and early intervention, education of athletes, parents, coaches, trainers, judges, and administrators is a priority. Athletes should be assessed for the Triad at the preparticipation physical and/or annual health screening exam, and whenever an athlete presents with any of the Triad's clinical conditions. Sport administrators should also consider rule changes to discourage unhealthy weight loss practices. A multidisciplinary treatment team should include a physician or other health-care professional, a registered dietitian, and, for athletes with eating disorders, a mental health practitioner. Additional valuable team members may include a certified athletic trainer, an exercise physiologist, and the athlete's coach, parents and other family members. The first aim of treatment for any Triad component is to increase energy availability by increasing energy intake and/or reducing exercise energy expenditure. Nutrition counseling and monitoring are sufficient interventions for many athletes, but eating disorders warrant psychotherapy. Athletes with eating disorders should be required to meet established criteria to continue exercising, and their training and competition may need to be modified. No pharmacological agent adequately restores bone loss or corrects metabolic abnormalities that impair health and performance in athletes with functional hypothalamic amenorrhea.

Factors associated with menstrual dysfunction and self-reported bone stress injuries in female runners in the ultra- and half-marathons of the Two Oceans

OBJECTIVE

To investigate factors associated with menstrual dysfunction, self-reported bone stress injuries and energy balance in women runners.

METHODS

613 runners were randomly sampled during the registration period for an endurance event. Demographic information, including self-reported height and weight, training and injury history and menstrual history, was collected by questionnaire.

RESULTS

Ultra-marathon (ULTRA) participants (n = 276) were significantly older (mean (SD) 39 (8.2) vs 34 (10.5) years; p<0.001), lighter (58.2 (6.6) vs 59.6 (8.3) kg; p<0.05) and reported a higher training volume (p<0.001) than half-marathon (HALF) participants (n = 337). Significantly more ULTRA subjects than HALF subjects reported a previous bone stress injury (21% vs 14%; p<0.05). There was no difference between the groups for menstrual status, but age at menarche was later (p<0.01) in the ULTRA group. Data were combined according to the absence (REG; n = 368/602 (61%)) or presence (IRREG; n = 234/602 (39%)) of a history of menstrual irregularity. Subject morphology was similar between groups, but the IRREG group had a higher self-reported measure on the self-loathing subscale (SLSS; p<0.01). The whole group was then classified according to current menstrual status, with 165 women being classified as currently irregular. (OLIGO/AMEN; 11.6%) and 445 women as currently regular (EUMEN; 88.4%). There were no morphological differences between the groups, however the OLIGO/AMEN group had a later age of menarche (p<0.01) than the EUMEN group. Further, women who reported a previous bone stress injury had higher SLSS scores than those who did not (2.91 (0.98) vs 2.68 (0.84); p<0.05).

CONCLUSIONS

There may be two independent mechanisms associated with energy balance, which are related to bone stress injuries, but may not necessarily be related to menstrual dysfunction.

Low lumbar spine bone mineral density in both male and female endurance runners

There have been many reports of low bone mineral density (BMD) in female endurance runners. Although there have been several reports of low BMD in male runners, it is unclear how comparable the problem is to that in females. We compared BMD between male and female endurance runners and with a reference population. One hundred and nine endurance runners (65 females, 44 males) aged 19-50 years participated and had been training regularly for at least 3 years (32-187.2 km week(-1)) in events from 3 km to the marathon. BMD was measured at the lumbar spine (L2-L4) and hip by DXA. A questionnaire assessed training and menstrual status. Lumbar spine T scores were similar in male and female runners (-0.8 (0.8) versus -0.8 (0.7); f = 0.015; P = 0.904) as were total hip T scores (0.6 (7.9) versus 0.5 (9.2); f = 0.192; P = 0.662). The proportion of male runners with low lumbar spine BMD (<-1.0) (n = 16 from 44) compared to that of females (n = 27 from 65) (P = 0.675). Males had lower spine T scores than eumenorrhoeic females (-0.8 (0.7) versus -0.4 (0.7); f = 5.169; P = 0.03). There were moderate negative correlations between weekly running distance and lumbar spine BMD in males and females (r(2) = 0.267; 0.189; P < 0.001), independent of menstrual status in females (r(2) = 0.192; P < 0.001). Lumbar spine but not hip T scores were greater in runners who participated in resistance training at least twice-a-week (male: -0.4 versus -1.1; female: -0.5 versus -1.1; P < 0.01). Using multiple regression, running distance (-) and BMI (+) together best predicted lumbar spine T scores (r(2) = 0.402; P < 0.01) in females. Although weak, BMI (+) best predicted hip T scores (r(2) = 0.167; P < 0.05). In males, running distance and training years (-) together best predicted lumbar spine T scores (r(2) = 0.400; P < 0.01). Training years (-) best predicted hip T scores (r(2) = 0.361; P < 0.01). To conclude, our findings suggest that male runners face the same bone threat at the spine, as female runners. Further research in male athletes is required. Incorporation of regular resistance training into an athlete's training programme may be a useful preventative strategy.

The pathophysiology of stress fractures

Stress fractures can occur in any active individual, from the weekend warrior to the elite athlete. As these injuries occur, it is important to understand how bones respond to the stresses placed on them. The understanding of potential intrinsic and extrinsic causes is important in treatment of these injuries. The proper identification and prevention of these stress injuries allows for athletes to return to activity expeditiously.

The female athlete triad exists in both elite athletes and controls

PURPOSE

To examine the prevalence of the female athlete triad (the Triad) in Norwegian elite athletes and controls.

METHODS

This study was conducted in three phases: (part I) screening by means of a detailed questionnaire, (part II) measurement of bone mineral density (BMD), and (part III) clinical interview. In part I, all female elite athletes representing the national teams at junior or senior level, aged 13-39 yr (N = 938) and an age group-matched randomly selected population-based control group (N = 900) were invited to participate. The questionnaire was completed by 88% of the athletes and 70% of the controls. Based on data from part I, a stratified random sample of athletes (N = 300) and controls (N = 300) was selected and invited to participate in parts II and III of the study. 186 athletes (62%) and 145 controls (48%) participated in all parts of the study.

RESULTS

Eight athletes (4.3%) and five controls (3.4%) met all the criteria for the Triad (disordered eating/eating disorder, menstrual dysfunction, and low BMD). Six of the athletes who met all the Triad criteria competed in leanness sports, and two in nonleanness sports. When evaluating the presence of two of the components of the Triad, prevalence ranged from 5.4 to 26.9% in the athletes and from 12.4 to 15.2% in the controls.

CONCLUSION

Our results support the assumption that a significant proportion of female athletes suffer from the components of the Triad. In addition, we found that the Triad is also present in normal active females. Therefore, prevention of one or more of the Triad components should be geared towards all physically active girls and young women.

Physical activity in the prevention and amelioration of osteoporosis in women : interaction of mechanical, hormonal and dietary factors

Osteoporosis is a serious health problem that diminishes quality of life and levies a financial burden on those who fear and experience bone fractures. Physical activity as a way to prevent osteoporosis is based on evidence that it can regulate bone maintenance and stimulate bone formation including the accumulation of mineral, in addition to strengthening muscles, improving balance, and thus reducing the overall risk of falls and fractures. Currently, our understanding of how to use exercise effectively in the prevention of osteoporosis is incomplete. It is uncertain whether exercise will help accumulate more overall peak bone mass during childhood, adolescence and young adulthood. Also, the consistent effectiveness of exercise to increase bone mass, or at least arrest the loss of bone mass after menopause, is also in question. Within this framework, section 1 introduces mechanical characteristics of bones to assist the reader in understanding their responses to physical activity. Section 2 reviews hormonal, nutritional and mechanical factors necessary for the growth of bones in length, width and mineral content that produce peak bone mass in the course of childhood and adolescence using a large sample of healthy Caucasian girls and female adolescents for reference. Effectiveness of exercise is evaluated throughout using absolute changes in bone with the underlying assumption that useful exercise should produce changes that approximate or exceed the absolute magnitude of bone parameters in a healthy reference population. Physical activity increases growth in width and mineral content of bones in girls and adolescent females, particularly when it is initiated before puberty, carried out in volumes and at intensities seen in athletes, and accompanied by adequate caloric and calcium intakes. Similar increases are seen in young women following the termination of statural growth in response to athletic training, but not to more limited levels of physical activity characteristic of longitudinal training studies. After 9-12 months of regular exercise, young adult women often show very small benefits to bone health, possibly because of large subject attrition rates, inadequate exercise intensity, duration or frequency, or because at this stage of life accumulation of bone mass may be at its natural peak. The important influence of hormones as well as dietary and specific nutrient abundance on bone growth and health are emphasised, and premature bone loss associated with dietary restriction and estradiol withdrawal in exercise-induced amenorrhoea is described. In section 3, the same assessment is applied to the effects of physical activity in postmenopausal women. Studies of postmenopausal women are presented from the perspective of limitations of the capacity of the skeleton to adapt to mechanical stress of exercise due to altered hormonal status and inadequate intake of specific nutrients. After menopause, effectiveness of exercise to increase bone mineral depends heavily on adequate availability of dietary calcium. Relatively infrequent evidence that physical activity prevents bone loss or increases bone mineral after menopause may be a consequence of inadequate calcium availability or low intensity of exercise in training studies. Several studies with postmenopausal women show modest increases in bone mineral toward the norm seen in a healthy population in response to high-intensity training. Physical activities continue to stimulate increases in bone diameter throughout the lifespan. These exercise-stimulated increases in bone diameter diminish the risk of fractures by mechanically counteracting the thinning of bones and increases in bone porosity. Seven principles of bone adaptation to mechanical stress are reviewed in section 4 to suggest how exercise by human subjects could be made more effective. They posit that exercise should: (i) be dynamic, not static; (ii) exceed a threshold intensity; (iii) exceed a threshold strain frequency; (iv) be relatively brief but intermittent; (v) impose an unusual loading pattern on the bones; (vi) be supported by unlimited nutrient energy; and (vii) include adequate calcium and cholecalciferol (vitamin D3) availability.

Stress Fractures and Knee Injuries in Runners

Running often can cause injuries to the knee as a result of kinetic chain dysfunctions. Addressing these dysfunctions in rehabilitation can prevent future injury. Stress fractures often occur in runners who engage in training errors. Female runners are particularly susceptible to stress fractures, especially in the setting of the female athlete triad. Proper identification and prevention of these injuries allows for athletes to return to running expeditiously.

Low bone mineral density is two to three times more prevalent in non-athletic premenopausal women than in elite athletes: a comprehensive controlled study

OBJECTIVE

To compare bone mineral density (BMD), investigate factors associated with BMD, and examine the prevalence of low BMD in athletes and non-athletic controls.

METHODS

The study included a questionnaire (part I), measurement of BMD (part II), and a clinical interview (part III). All Norwegian female athletes on national teams (n = 938) and an aged matched random sample of non-athletic controls (n = 900) were invited to participate. The questionnaire was completed by 88% of athletes and 70% of controls. A random sample of these athletes (n = 300) and controls (n = 300) was invited to participate in parts II and III. All parts were completed by 186 athletes (62%) and 145 controls (48%).

RESULTS

Mean (standard deviation) total body (TB) BMD was higher (p<0.001) in athletes (1.21 (0.09) g/cm2) than in controls (1.18 (0.08) g/cm2), and higher (p<0.001) in high impact (HI) sports athletes than in medium impact (MI) and low impact (LI) sports athletes. In athletes, body weight and impact loading sports were positively associated, and percent body fat and eating disorders were negatively associated with TB BMD. Body weight and weight bearing activities were positively associated and menstrual dysfunction was negatively associated with TB BMD in controls. A higher percentage of controls (28.3%) than athletes (10.7%) had low BMD (p<0.001).

CONCLUSION

Female elite athletes have 3-20% higher BMD than non-athletic controls and HI sports athletes have 3-22% higher BMD compared with MI and LI sports athletes. Low BMD is two to three times more common in non-athletic premenopausal women than in elite athletes.

Nutritional and exercise-related determinants of bone density in elite female runners

Although the female athletic triad is widely recognized clinically, there have been few studies quantitating the effect of disordered eating on bone mineral density. The purpose of this study was to explore the mechanisms through which disordered eating might influence the skeleton in nationally or internationally competitive runners. Fifty British national or higher standard middle and long-distance female runners aged under 36 years were recruited; 24 had amenorrhea (AM), nine had oligomenorrhea (OL) and the others were eumenorrheic (EU). Bone mineral density (BMD g.cm(-2)) of the proximal femur (femoral neck and trochanter) and lumbar spine (L2-L4) was measured by dual energy X-ray absorptiometry (DXA) and compared with population-based European reference data. Dietary eating patterns were assessed with the Eating Attitudes Test (EAT26) and Bulimia Investigatory Test Edinburgh (BITE) questionnaires. High eating disorder scores were common; the EAT26 score predicted menstrual disorders (P=0.014) and correlated with body mass index (BMI). BMD was generally low in the AM group, but was raised in the proximal femur in the EU group. In the AM group, younger age at start of training was associated with higher trochanteric BMD. In addition, years of eumenorrhea were positively associated with spine BMD. Although a high EAT26 score was associated with lower BMD in the proximal femur, this could be explained by the intermediary effect of menstrual disorders. Osteocalcin, a marker of bone formation, was reduced in the AM group and was also reduced by high VO2max and high BITE score, consistent with a central (hypothalamic) pathway for suppressing osteoblastic bone formation. Eumenorrheic runners had increased femoral BMD compared with European controls, consistent with a positive effect of increased mechanical loading. The effect of disordered eating to reduce BMD could be explained by its association with menstrual dysfunction. Lumbar spine BMD was reduced most in those athletes who menstruated for the shortest time in adolescence.

Energy Balance, Bone Turnover, and Skeletal Health in Physically Active Individuals

Over the past 20 years, there have been a growing number of reports of low bone mineral density (BMD) or premature bone loss in individuals with a high physical activity level. These skeletal problems have been documented mainly in underweight women with amenorrhea and have often been linked to a sex hormone deficiency. However, sex hormone treatment has been shown to have limited efficacy for the prevention or treatment of low BMD in such women. Studies of bone turnover in women with sustained exercise-associated amenorrhea using metabolic markers of osteoblast activities and collagen synthesis have demonstrated an apparent reduction of bone formation that is associated with a low body mass index (BMI) and with endocrine disturbances that are characteristic of energy deficit. Comparable metabolic and endocrine disturbances have been observed in anorexic women that reverse with weight gain. Furthermore, increases of BMD accompany weight gain in both groups of women, even without a return of menses. Collectively, these observations suggest an important link between energy balance and the balance of bone turnover in women with exercise and/or diet-associated amenorrhea. Although there have been few studies that have explored relations between bone turnover, BMD, and energy balance in physically active men, there is evidence for a link between reduced bone formation and an abrupt, short-term energy deficit. Interestingly, the presence of low BMD in physically active men has not been associated with a sex hormone deficiency. This review evaluates the evidence that underlies the hypothesis that an energy deficit is instrumental in the disturbance of bone turnover that has been observed in physically active individuals.

The assessment of bone metabolism in female elite endurance athletes by biochemical bone markers

Purpose: Premature osteoporosis is a frequent problem in female athletes. Current concepts suggest that a disruption of the hypothalamic-pituitary axis leads to hypoestrogenism, which then causes amenorrhea and osteoporosis. However, the underlying mechanisms have been insufficiently investigated. Osteoprotegerin (OPG) and soluble TNF-α receptor antagonist ligand (sRANKL) regulate the balance of osteoblasts and osteoclasts. Their role in the pathogenesis of osteoporosis in female athletes has not been studied yet.

Methods: We measured OPG and sRANKL in relation to biochemical bone markers [osteocalcin (OC), bone alkaline phosphatase (BAP), serum β-crosslaps (CTx)] and female sex hormones [estradiol (E2) and luteinizing hormone (LH)] in fastening blood samples from 25 female elite endurance athletes and 25 matched controls.

Results: Athletes exhibited significantly higher levels of the bone resorption marker CTx than controls (0.61±0.26 vs. 0.44±0.15ng/ml). OPG and sRANKL were not changed. Subgroup analysis revealed that athletes using oral contraceptives [A-OCC(−)] had significantly higher levels of CTx (0.82±0.20 vs. 0.50±0.14ng/ml), BAP [37.3 (23.2–54.4) U/l vs. 25.2 (20.3–35.6) U/l] and OPG (3.4±0.8 vs. 2.7±0.8ng/ml) than controls who did not use oral contraceptives [C-OCC(−)]. While the difference for CTx exceeded the least significant change in this marker by approximately 30%, the differences for the bone formation markers OC and BAP were close to the least significant change. In athletes using oral contraceptives [A-OCC(+)] we found no differences compared to controls.

Conclusions: A-OCC(−) athletes have increased bone turnover with a particular stimulation of bone resorption. The increased bone resorption is not accompanied by a shift of the OPG/sRANKL relationship towards an osteoclastogenic constellation. Since increased bone resorption was not detectable in A-OCC(+) athletes, it can be suggested that OCC use might protect bone health in female athletes.

Effects of a triphasic combination oral contraceptive containing norgestimate/ethinyl estradiol on biochemical markers of bone metabolism in young women with osteopenia secondary to hypothalamic amenorrhea

This multicenter, double-blind, placebo-controlled, randomized study of 45 patients evaluated the short-term effects of an oral contraceptive [Ortho Tri-Cyclen, 180-250 micro g of norgestimate (NGM) and 35 microg of ethinyl estradiol (EE)] on biochemical markers of bone resorption, formation, and osteoprotegerin in young women (mean age +/- SD, 26.5 +/- 6.3 yr) with hypothalamic amenorrhea and osteopenia. Body fat, endocrine, and cognitive function were evaluated as secondary endpoints. Biomarkers of bone metabolism were measured at baseline and after three cycles of NGM/EE or placebo. There were significant decreases in mean values of N-telopeptide [mean (SD), -13.4 (13.4) vs. 1.2 (23.8) nmol bone collagen equivalents (BCE)/mmol creatinine (Cr); P = 0.001] and deoxypyridinoline [-1.2 (2.9) vs. -0.5 (1.5) nmol deoxypyridinoline/mmol Cr; P = 0.021] as well as significant decreases in bone specific alkaline phosphatase [-5.1 (3.5) vs. 0.4 (3.1) ng/ml; P < 0.001], osteocalcin [-5.9 (3.6) vs. -2.9 (3.7); P = 0.016], and procollagen of type I propeptide [-35.2 (44.6) vs. -0.2 (30.0) ng/ml; P = 0.025], but not osteoprotegerin [0.39 (1.46) vs. -0.2 (0.49) pmol/liter; P = 0.397] in the NGM/EE vs. placebo group. There were no significant differences between groups with respect to changes in cognitive function, mood, body weight, body mass index, body fat, percentage of body fat, and all endocrine levels except FSH, [-3.7 (3.8) vs. -0.6 (2.1) IU/liter; P < 0.001, NGM/EE vs. placebo]. No serious adverse events were reported in either group. These results suggest that NGM/EE decreases bone turnover in osteopenic premenopausal women with hypothalamic amenorrhea. Further studies are needed to determine whether estrogen will increase bone density in this population.

Disordered eating, menstrual irregularity, and bone mineral density in female runners

PURPOSE

To examine the relationships between disordered eating, menstrual irregularity, and low bone mineral density (BMD) in young female runners.

METHODS

Subjects were 91 competitive female distance runners aged 18-26 yr. Disordered eating was measured by the Eating Disorder Inventory (EDI). Menstrual irregularity was defined as oligo/amenorrhea (0-9 menses per year). BMD was measured by dual x-ray absorptiometry.

RESULTS

An elevated score on the EDI (highest quartile) was associated with oligo/amenorrhea, after adjusting for percent body fat, age, miles run per week, age at menarche, and dietary fat, (OR [95% CI]: 4.6 [1.1-18.6]). Oligo/amenorrheic runners had lower BMD than eumenorrheic runners at the spine (-5%), hip (-6%), and whole body (-3%), even after accounting for weight, percent body fat, EDI score, and age at menarche. Eumenorrheic runners with elevated EDI scores had lower BMD than eumenorrheic runners with normal EDI scores at the spine (-11%), with trends at the hip (-5%), and whole body (-5%), after adjusting for differences in weight and percent body fat. Runners with both an elevated EDI score and oligo/amenorrhea had no further reduction in BMD than runners with only one of these risk factors.

CONCLUSION

In young competitive female distance runners, (i) disordered eating is strongly related to menstrual irregularity, (ii) menstrual irregularity is associated with low BMD, and (iii) disordered eating is associated with low BMD in the absence of menstrual irregularity.

Aetiology of rib stress fractures in rowers

Rib stress fractures are a common and significant problem in the rowing population. They occur in approximately 6.1 to 12% of rowers and account for the most time lost from on-water training and competition. This review discusses possible causative factors for rib stress fractures in rowers. Central to the establishment of causative factors is the identification that each rib forms part of a closed ring of bone that is completed anteriorly by the sternum and posteriorly by the thoracic vertebrae. Because of the shared sternum anteriorly each ring of bone is mechanically connected. Subsequently, during rowing individual ribs are not loaded in isolation, rather the rib cage is loaded as a complete unit. Incorporating this functioning as a complete unit a possible mechanism by which different factors contribute to rib stress fracture can be developed. In rowing, muscle factors generate loading of the rib cage. The characteristics of this loading stimulus are influenced by equipment, technique and joint factors. Rib-cage loading generates bone strain in individual ribs with the response of each rib depending upon site-specific skeletal factors. Depending on the characteristics of the bone strain in terms of the magnitude and rate of strain, microdamage may develop. The bone response to this microdamage is reparative remodelling. Whether this response is capable of repairing the damage to prevent progression to a stress fracture is dependent upon training and gender factors. Identification of these factors will generate a better understanding of the aetiology of this injury, which is required for improved prevention and treatment strategies.

Physiological factors associated with low bone mineral density in female endurance runners

OBJECTIVE

To explore potential factors that could be associated with low bone mineral density (BMD) in female endurance runners.

METHODS

Fifty two female endurance runners (1,500 m to marathon), aged 18-44 years, took part. Body fat percentage, lumbar spine BMD, and femoral neck BMD were measured using the Hologic QDR 4,500w bone densitometer. Data on training, menstrual cycle status, osteoporosis, and health related factors were obtained by questionnaire. Dietary variables were assessed from a prospective seven day dietary record of macronutrients and micronutrients.

RESULTS

The mean (SD) lumbar spine and femoral neck BMD were 1.11 (0.11) and 0.89 (0.12) g/cm(2) respectively. A backward elimination regression analysis showed that age, body mass, body fat, distance run, magnesium, and zinc intake were the variables significantly associated with BMD. Lumbar spine BMD (g/cm(2)) = -1.90 + (0.0486 x age (years)) + (0.342 x log mass (kg)) - (0.000861 x age(2) (years)) - (0.00128 x distance (km/week)), with an R(2) = 30.1% (SEE = 0.089 (95% confidence interval (CI) 0.05 to 0.23); p<0.001). Femoral neck BMD (g/cm(2)) = -2.51 - (0.00989 x age (years)) + (0.720 x log mass (kg)) + (0.000951 x magnesium (mg/day)) -(0.0289 x zinc (mg/day)) - (0.00821 x body fat (%)) - (0.00226 x distance (km/week)), with an R(2) = 50.2% (SEE = 0.100 (95% CI 0.06 to 0.22); p<0.001). The negative association between skeletal BMD and distance run suggested that participants who ran longer distances had a lower BMD of the lumbar spine and femoral neck. Further, the results indicated a positive association between body mass and BMD, and a negative association between body fat and BMD.

CONCLUSIONS

The results suggest a negative association between endurance running distance and lumbar spine and femoral neck BMD, with a positive association between body mass and femoral neck and lumbar spine BMD. However, longitudinal studies are required to assess directly the effect of endurance running and body mass on BMD, and to see if the addition of alternative exercise that would increase lean body mass would have a positive effect on BMD and therefore help to prevent osteoporosis.

Female athlete triad

OBJECTIVE

To describe the components of female athlete triad, the proposed mechanisms that may relate to its causation, and some screening and treatment options that may be used by the clinician who encounters this clinical entity in patients.

DATA SOURCES

A qualitative review of the literature was performed.

RESULTS

This article provides the clinician with current information relevant to understanding and recognizing female athlete triad in at-risk patients. The components of the triad-amenorrhea, disordered eating, and osteoporosis-are interrelated in multifactorial etiology, pathogenesis, and consequences. Proposed causal factors include inadequate nutrition, menstrual status, training intensity and frequency, body size and composition, and psychological and physiological stress. There should be a high index of suspicion in all females athletes for the presence of and/or increased risk for female athlete triad. An increased awareness of the existence of the problem and its presenting signs and symptoms is the key to screening for this syndrome. The most efficacious treatment lies in its prevention.

CONCLUSIONS

Female athlete triad is an interrelated, multifactorial syndrome comprised of disordered eating, amenorrhea, and osteoporosis. It is a common entity among female athletes. Prevention, early detection, and early treatment are absolutely essential to maintain the athletes health into maturity and to prevent the serious consequences of this triad. The long-term effects of some triad components are still unknown.

Bone density and amenorrhea in ballet dancers are related to a decreased resting metabolic rate and lower leptin levels

Osteopenia, which is correlated with amenorrhea and poor nutritional habits, has been well documented in elite ballet dancers. Estrogen replacement therapy and recovery from amenorrhea have not been associated with normalization of bone density. Thus, the osteopenia may be related to changes brought about by chronic dieting or other factors, such as a hypometabolic state induced by poor nutrition. The purpose of this study was to investigate the relationship of chronic dieting and resting metabolic rate (RMR) to amenorrhea and bone density. RMR, bone density, eating disorder assessments, leptin levels, and complete menstrual and medical histories were determined in 21 elite ballet dancers and in 27 nondancers (age, 20-30 yr). No significant correlations were found between high EAT26 scores, a measure of disordered eating, and RMR, bone densities, body weight, body fat, or fat-free mass. However, when RMR was adjusted for fat-free mass (FFM), a significant positive correlation was found between RMR/FFM and bone density in both the arms (P < 0.001) and spine (P < 0.05) in ballet dancers, but not in the normal controls. The dancers also demonstrated significantly higher EAT scores (22.9 +/- 10.3 vs. 4.1 +/- 2.4; P < 0.001) and lower RMR/FFM ratios (30.0 +/- 2.2 vs. 32.05 +/- 2.8; P < 0.01). The only variable to predict lower RMR/FFM in the entire sample was ever having had amenorrhea; this group had significantly higher EAT scores (18.0 +/- 13.5 vs. 10.3 +/- 10.2; P < 0.05), lower leptin levels (4.03 +/- 0.625 vs. 7.10 +/- 4.052; P < 0.05), and lower bone mineral density in the spine (0.984 +/- 0.11 vs. 1.10 +/- 0.13; P < 0.05) and arm (0.773 +/- 0.99 vs. 0.818 +/- 0.01; P < 0.05). We hypothesize that the correlation between low RMR and lower leptin levels and bone density may be more strongly related to nutritional habits in ballet dancers, causing significant depression of RMR, particularly for those with a history of amenorrhea.

Identifying college athletes at risk for pathogenic eating

OBJECTIVES

To evaluate the effectiveness of a discriminant function that predicts risk of pathogenic eating in comparison with a standard self report measure (EAT) and a clinical interview. In addition, to determine the effectiveness of this discriminant function using a variety of collegiate athletes.

METHODS

A total of 319 participants were asked to complete a series of self report measures that assessed dietary practices. In addition, anthropometric measures were obtained, and a random sample of 15% participated in a structured clinical interview.

RESULTS

Correlational analyses indicated that the discriminant function categorisation of risk was significantly related to both the clinical interview and EAT (p < or =0.05). The discriminant function was accurate in predicting risk category in this diverse group of athletes, particularly with respect to those at low risk (83.1%) and those at high risk (72.7%).

CONCLUSION

This information may be helpful in the development of a simple, accessible tool to identify athletes at risk of engaging in pathogenic eating behaviours.

Hypothalamic amenorrhea. The effects of environmental stresses on the reproductive system: a central effect of the central nervous system

Although the treatment of anovulation has become significantly more specialized and complex in the centuries since Hippocrates, a complete understanding of the causes and mechanisms of hypothalamic amenorrhea has not been achieved. Even the best research on hypothalamic amenorrhea is plagued by the lack of longitudinal studies, the use of different exercise models, the difficulty of controlling for caloric intake, and the fact that genetics may have a role in the disorder. Continuing research on metabolic rate, leptin, and other factors will ultimately answer many of the outstanding questions and will help to create better tools for treating this disorder.