Higher incidence of bone stress injuries with increasing female athlete triad-related risk factors: a prospective multisite study of exercising girls and women

Contemporary Issue: Health and Safety of Female Wrestlers

ABSTRACT

Female wrestling has grown exponentially over the past decade. Within the United States, 46 states now recognize female high school wrestling, and 153 colleges have programs. It is on track to become an NCAA championship-level sport in 2026. A primary health and safety risk among this cohort pertains to rapid weight loss strategies. These can lead to intentional caloric restriction and decreased body fatness, with the perceived goal of attaining a competitive advantage. Low energy availability and low body fatness are associated with a number of health concerns including menstrual dysfunction and loss of bone mineral density in girls and women. The current recommendation of 12% as a minimum for percentage body fat is very likely too low, opening the door for health perturbations among this population. The minimum threshold might more appropriately fall within the range of 18% to 20%. Body fat assessment methods, primarily skinfold measures that are used to guide weight class selection, have not been adequately validated among this population and therefore should be an area of research focus, while also exploring alternative assessment techniques. Further, we recommend that weight cycling, restrictive energy intake, and intentional dehydration be avoided. Research should assess the effects of frequent weight cycling (to "make weight") and prolonged periods of low body fat on the reproductive and bone health of these athletes. Finally, research and clinical evaluations on female wrestlers are limited, and we offer a list of research priorities for future investigation into this contemporary issue.

The Role of Musculoskeletal Training During Return to Performance Following Relative Energy Deficiency in Sport

BACKGROUND

Relative energy deficiency in sport (REDs) is a condition that is associated with negative health and performance outcomes in athletes. Insufficient energy intake relative to exercise energy expenditure, resulting in low energy availability, is the underlying cause, which triggers numerous adverse physiological consequences including several associated with musculoskeletal (MSK) health and neuromuscular performance.

PURPOSE

This commentary aims to (1) discuss the health and performance implications of REDs on the skeletal and neuromuscular systems and (2) examine the role that MSK training (ie, strength and plyometric training) during treatment and return to performance following REDs might have on health and performance in athletes, with practical guidelines provided.

CONCLUSIONS

REDs is associated with decreases in markers of bone health, lean body mass, maximal and explosive strength, and muscle work capacity. Restoration of optimal energy availability, mainly through an increase in energy intake, is the primary goal during the initial treatment of REDs with a return to performance managed by a multidisciplinary team of specialists. MSK training is an effective nonpharmacological component of treatment for REDs, which offers multiple long-term health and performance benefits, assuming the energy needs of athletes are met as part of their recovery. Supervised, prescribed, and gradually progressive MSK training should include a combination of resistance training and high-impact plyometric-based exercise to promote MSK adaptations, with an initial focus on achieving movement competency. Progressing MSK training exercises to higher intensities will have the greatest effects on bone health and strength performance in the long term.

An Opinion on the Interpretation of Bone Turnover Markers Following Acute Exercise or Nutrition Intervention and Considerations for Applied Research

It is important for athlete and public health that we continue to develop our understanding of the effects of exercise and nutrition on bone health. Bone turnover markers (BTMs) offer an opportunity to accelerate the progression of bone research by revealing a bone response to exercise and nutrition stimuli far more rapidly than current bone imaging techniques. However, the association between short-term change in the concentration of BTMs and long-term bone health remains ambiguous. Several other limitations also complicate the translation of acute BTM data to applied practice. Importantly, several incongruencies exist between the effects of exercise and nutrition stimuli on short-term change in BTM concentration compared with long-term bone structural outcomes to similar stimuli. There are many potential explanations for these inconsistencies, including that short-term study designs fail to encompass a full remodeling cycle. The current article presents the opinion that data from relatively acute studies measuring BTMs may not be able to reliably inform applied practice aiming to optimize bone health. There are important factors to consider when interpreting or translating BTM data and these are discussed.

[Dance-specific eligibility of vocational ballet students - examinations at a governmental training institution for classical ballet]

BACKGROUND

During their training, pre-professional ballet students are confronted with physical stresses comparable to those of competitive sports. In competitive sports, there are mandatory and binding aptitude tests to ensure that the growing athlete meets the requirements. In ballet, there are no such mandatory examinations preceding the start of training. For adult professional dancers, musculoskeletal ideals could be isolated from the dance medicine literature. However, only a few studies describe musculoskeletal characteristics of pre-professional ballet students. It is neither known at what age a student should meet the ideal measurements for an adult nor what deviations from the ideal can be considered normal. This study aims to describe sociodemographic and musculoskeletal characteristics of pre-professional ballet students and discusses to what extent they already meet or deviate from dance-specific eligibility criteria for adult professional ballet dancers.

MATERIAL AND METHODS

In this study, n = 414 female and n = 192 male students of John Cranko School (JCS) were seen by an experienced orthopaedist and dance physician. Mean age was 13.9 years (SD 3.5, range 5-22 years). Their medical history was taken (age; nationality; start of ballet/training) and a physical examination was performed (height/weight; symmetry of shoulder girdle, spine, waist triangles; pelvic tilt; tibial torsion; range of motion of base of index finger joint, spine, hips, ankle and base of great toe joint). Subsequently, the results of this study were compared with suitability criteria for adult professional ballet dancers that had been isolated from the dance medicine literature for a previous article.

RESULTS

Examinees were from 49 different nations. 34.6% of the female subjects (≥16 years) were between 165 and 170 cm and 33.3% of the male subjects (≥18 years) were between 178 and 185 cm tall. 45.0% of those examined showed low body weight (<10th percentile, BMI <18.5 kg/m²). The trunk of 61.0-84.8% of those examined was erect and symmetrical. 25.2% had scoliosis. Half (53.5%) were found to have a bilateral external rotation of the hips of at least 60°, and 68.7% had a bilateral internal rotation between 20 and 50°. 87.3% exhibited a bilateral tibial torsion between 15 and 40°. A bilateral en dehors of 90° was calculated for 25.0%. In 9.1% of those examined, the upper ankle joints presented a dorsiflexion of at least 25°, and in 70.2%, a plantarflexion of at least 70° was seen. In 88.0%, the metatarsophalangeal joint of the great toe was 90° (f) and 80° (m) on both sides.

CONCLUSION

The results of this study showed that pre-professional ballet students fulfil many characteristics of adult professional ballet dancers. High values already among young age groups suggest a ballet-specific selection. Nevertheless, not all students fulfil the theoretical "ideal measurements" for professional classical ballet. These anatomical limits should be considered individually in training to protect the growing pre-professional ballet dancer. The high ballet-specific anatomical demands, but especially the large number of students with a low body weight, underline the necessity of mandatory aptitude tests at the beginning and regular check-ups in the course of training to avert compensatory mechanisms and their consequential damage and to screen for eating disorders and disorders of eating behaviour.

Changes in the concentration of bone turnover markers in men after maximum intensity exercise

Background

Physical activity is an important factor in modelling the remodelling and metabolism of bone tissue. The aim of the study was to evaluate the changes in indices demonstrating bone turnover in men under the influence of maximum-intensity exercise.

Methods

The study involved 33 men aged 20-25, divided into two groups: experimental (n = 15) and control (n = 18). People training medium- and long-distance running were assigned to the experimental group, and non-training individuals to the control. Selected somatic, physiological and biochemical indices were measured. The level of aerobic fitness was determined using a progressively increasing graded test (treadmill test for subjective fatigue). Blood samples for determinations were taken before the test and 60 minutes after its completion. The concentration of selected bone turnover markers was assessed: bone fraction of alkaline phosphatase (b-ALP), osteoclacin (OC), N-terminal cross-linked telopeptide of the alpha chain of type I collagen (NTx1), N-terminal propeptide of type I progolagen (PINP), osteoprotegerin (OPG). In addition, the concentration of 25(OH)D3 prior to the stress test was determined. Additionally, pre and post exercise, the concentration of lactates in the capillary blood was determined.

Results

When comparing the two groups, significant statistical differences were found for the mean level of: 25(OH)D3 (p = 0.025), b-ALP (p < 0.001), OC (p = 0.004) and PINP (p = 0.029) prior to the test. On the other hand, within individual groups, between the values pre and post the stress test, there were statistically significant differences for the average level of: b-ALP (p < 0.001), NTx1 (p < 0.001), OPG (p = 0.001) and PINP (p = 0.002).

Conclusion

A single-session maximum physical effort can become an effective tool to initiate positive changes in bone turnover markers.

Factors Associated With High-Risk and Low-Risk Bone Stress Injury in Female Runners: Implications for Risk Factor Stratification and Management

Background

Bone stress injury (BSI) is a common overuse injury in active women. BSIs can be classified as high-risk (pelvis, sacrum, and femoral neck) or low-risk (tibia, fibula, and metatarsals). Risk factors for BSI include low energy availability, menstrual dysfunction, and poor bone health. Higher vertical load rates during running have been observed in women with a history of BSI.

Purpose/Hypothesis

The purpose of this study was to characterize factors associated with BSI in a population of premenopausal women, comparing those with a history of high-risk or low-risk BSI with those with no history of BSI. It was hypothesized that women with a history of high-risk BSI would be more likely to exhibit lower bone mineral density (BMD) and related factors and less favorable bone microarchitecture compared with women with a history of low-risk BSI. In contrast, women with a history of low-risk BSI would have higher load rates.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Enrolled were 15 women with a history of high-risk BSI, 15 with a history of low-risk BSI, and 15 with no history of BSI. BMD for the whole body, hip, and spine was standardized using z scores on dual-energy x-ray absorptiometry. High-resolution peripheral quantitative computed tomography was used to quantify bone microarchitecture at the radius and distal tibia. Participants completed surveys characterizing factors that influence bone health-including sleep, menstrual history, and eating behaviors-utilizing the Eating Disorder Examination Questionnaire (EDE-Q). Each participant completed a biomechanical assessment using an instrumented treadmill to measure load rates before and after a run to exertion.

Results

Women with a history of high-risk BSI had lower spine z scores than those with low-risk BSI (-1.04 ± 0.76 vs -0.01 ± 1.15; P < .05). Women with a history of high-risk BSI, compared with low-risk BSI and no BSI, had the highest EDE-Q subscores for Shape Concern (1.46 ± 1.28 vs 0.76 ± 0.78 and 0.43 ± 0.43) and Eating Concern (0.55 ± 0.75 vs 0.16 ± 0.38 and 0.11 ± 0.21), as well as the greatest difference between minimum and maximum weight at current height (11.3 ± 5.4 vs 7.7 ± 2.9 and 7.6 ± 3.3 kg) (P < .05 for all). Women with a history of high-risk BSI were more likely than those with no history of BSI to sleep <7 hours on average per night during the week (80% vs 33.3%; P < .05). The mean and instantaneous vertical load rates were not different between groups.

Conclusion

Women with a history of high-risk BSI were more likely to exhibit risk factors for poor bone health, including lower BMD, while load rates did not distinguish women with a history of BSI.

Direct and indirect impact of low energy availability on sports performance

Low energy availability (LEA) occurs inadvertently and purposefully in many athletes across numerous sports; and well planned, supervised periods with moderate LEA can improve body composition and power to weight ratio possibly enhancing performance in some sports. LEA however has the potential to have negative effects on a multitude of physiological and psychological systems in female and male athletes. Systems such as the endocrine, cardiovascular, metabolism, reproductive, immune, mental perception, and motivation as well as behaviors can all be impacted by severe (serious and/or prolonged or chronic) LEA. Such widely diverse effects can influence the health status, training adaptation, and performance outcomes of athletes leading to both direct changes (e.g., decreased strength and endurance) as well as indirect changes (e.g., reduced training response, increased risk of injury) in performance. To date, performance implications have not been well examined relative to LEA. Therefore, the intent of this narrative review is to characterize the effects of short-, medium-, and long-term exposure to LEA on direct and indirect sports performance outcomes. In doing so we have focused both on laboratory settings as well as descriptive athletic case-study-type experiential evidence.

Dietary Intake and Menstrual Health among Acrobatics and Tumbling NCAA Division I Student-Athletes

OBJECTIVE

Acrobatics & Tumbling (A&T) is an emerging sport in the National Collegiate Athletic Association that lacks research regarding the dietary intake and health of A&T student-athletes (A&Tsa). This study assessed the dietary intake adequacy, estimated energy availability (EA), self-reported menstrual health, and body composition of A&Tsa.

METHODS

Twenty-four female A&Tsa participated during week 8 of the preseason (11 top: Age= 20.1 ± 0.9 years; BMI= 22.1 ± 1.7 kg/m2; 13 base: Age= 19.5 ± 1.3 years; BMI= 26.2 ± 2.7 kg/m2). Total energy intake (TEI) and macronutrient intakes were assessed via a paper-based 3-day dietary recall. Resting Metabolic Rate [RMR = 500 + 22 * fat-free mass (FFM)] and energy availability [EA = (TEI - exercise energy expenditure)/FFM)] were estimated; and LEAF-Q assessed menstrual health. Body composition was measured using Dual-Energy X-Ray Absorptiometry. Macronutrient intakes and EA were compared to sports nutrition recommendations (carbohydrate: 6-10 g/kg; protein: 1.2-2.0 g/kg) and the Acceptable Macronutrient Distribution Range (carbohydrate: 45-65%; protein: 10-35%; fat: 20-35%).

RESULTS

TEI was 1753 ± 467 kcal (top) and 1980 ± 473.8 kcal (base). A total of 20.8% of A&Tsa failed to meet RMR with TEI, with a higher prevalence in the top (-266 ± 219.2 kcal, n = 3) vs. base (-414.3 ± 534.4 kcal, n = 2) A&Tsa. Top and base A&Tsa had both low EA (28.8 ± 13.4 kcals·FFM-1; 23.8 ± 9.5 kcals·FFM-1) and inadequate carbohydrate intake averages (4.2 ± 1.3 g/kg; 3.5 ± 1.1 g/kg, p < 0.001), respectively. A total of 17% of A&Tsa reported secondary amenorrhea, with a higher prevalence in the top (27.3%, n = 3) vs. the base (7.7%, n = 1).

CONCLUSION

TEI and carbohydrate intake of the majority of A&Tsa were below recommendations. Sports dietitians should encourage and educate A&Tsa about following an adequate diet that meets energy and sports-specific macronutrient needs.

Differences of Bone Mineral Density by Characteristics of Sports in Amenorrheic Athletes

Hypothalamic amenorrhea leads to a hypoestrogenic state, causing decreased bone mineral density (BMD), while strong impact loading on bone has been shown to increase BMD. The purpose of this study is to compare BMD in female athletes based on menstrual status and their sports/events by impact loading characteristics. BMD at the lumbar spine was measured by dual-energy X-ray absorptiometry and hormone level. The subjects were classified into four groups and BMD and hormone levels were compared among the four groups, which were divided into amenorrheic athletes (AAs) and eumenorrheic athletes (EAs). This study recruited 410 female athletes (164 in the AAs and 246 in the EAs), 55 athletes in non-impact sports, 123 in low-impact sports, 141 in multidirectional sports, and 91 in high-impact sports. In the AAs group, BMD Z-score was lowest in low-impact sports (Z-score: -1.53 [-1.76, -1.30]), and was highest in high-impact sports (Z-score: 0.02 [-0.34, 0.38]). In multidirectional and high-impact sports, BMD Z-score in the AAs group did not show results lower than the average for non-athletes. When screening female athletes for low BMD, it is important to evaluate the risk of low BMD based on the impact loading characteristics of their sports/events, in addition to the menstrual state.

Prevalence of low energy availability in 25 New Zealand elite female rowers - A cross sectional study

OBJECTIVES

To quantify energy availability (EA) in elite female rowers, determine its association with bone mineral density (BMD), and examine the ability of the low energy availability in females-questionnaire (LEAF-Q) and brief eating disorder in athletes-questionnaire (BEDA-Q) to distinguish between low and normal EA.

DESIGN

Observational cross-sectional study.

METHODS

Twenty-five elite female rowers participated in the study. EA was calculated by means of a 4-day food intake diary and analysis of training load. Low energy availability (LEA) was defined as EA <30 kCal * kg-1 * FFM-1 * day-1. Dual-energy X-ray absorptiometry (DXA) was used to assess fat free mass (FFM) and BMD Z-scores. LEA risk was assessed using the LEAF-Q and BEDA-Q.

RESULTS

The mean EA was 23.2 ± 12.2 kCal * kg-1 * FFM-1 * day-1. Prevalence of LEA was 64 %. The mean BMD Z-score was 1.6 ± 0.6 (range: 0.7 to 2.9). Athletes with LEA had a significantly higher BEDA-Q score than the group with normal EA (mean 0.30 ± 0.17 vs. 0.09 ± 0.11, P < 0.05), but LEAF-Q score was not different between groups (mean 10.4 ± 4.6, 8.2 ± 4.5, P = 0.29).

CONCLUSION

Low energy availability is common amongst elite female rowers in New Zealand and is positively correlated with higher scores on the BEDA-Q. Bone mineral density was normal irrespective of EA status.

Higher Triad Risk Scores Are Associated With Increased Risk for Trabecular-Rich Bone Stress Injuries in Female Runners

OBJECTIVE

Bone stress injuries (BSIs) in trabecular-rich bone are associated with greater biological risk factors compared with cortical-rich bone. We hypothesized that female runners with high Female Athlete Triad (Triad)-related risk would be at greater risk for trabecular-rich BSIs than runners with low Triad-related risk.

DESIGN

Prospective cohort study.

SETTING

Two NCAA institutions.

PARTICIPANTS

Female runners were followed prospectively for up to 5 years.

INTERVENTION

The intervention consisted of team nutrition presentations focused on optimizing energy availability plus individualized nutrition sessions. Triad Cumulative Risk Assessment (CRA) categories were assigned yearly based on low-energy availability, menstrual status, age of menarche, low body mass index, low bone mineral density, and prior BSI.

MAIN OUTCOME MEASURES

The outcome was the annual incidence of trabecular- and cortical-rich BSI. Generalized Estimating Equations (GEE, to account for the correlated nature of the observations) with a Poisson distribution and log link were used for statistical modeling.

RESULTS

Cortical-rich BSI rates were higher than trabecular-rich BSI rates (0.32 vs 0.13 events per person-year). Female runners with high Triad-related risk had a significantly higher incidence rate ratio of trabecular-rich BSI (RR: 4.40, P = 0.025) and cortical-rich BSI (RR: 2.87, P = 0.025) than women with low Triad-related risk. Each 1-point increase in Triad CRA score was associated with a significant 26% increased risk of trabecular-rich BSI ( P = 0.0007) and a nonsignificant 14% increased risk of cortical-rich BSI ( P = 0.054).

CONCLUSIONS

Increased Triad CRA scores were strongly associated with increased risk for trabecular-rich BSI. Incorporating Triad CRA scores in clinical care could guide BSI prevention.

Considerations of Low Carbohydrate Availability (LCA) to Relative Energy Deficiency in Sport (RED-S) in Female Endurance Athletes: A Narrative Review

The purpose of this narrative review is to identify health and performance consequences associated with LCA in female endurance athletes. The intake of carbohydrates (CHO) before, during, and after exercise has been demonstrated to support sport performance, especially endurance activities which rely extensively on CHO as a fuel source. However, low energy availability (LEA) and low carbohydrate availability (LCA) are common in female athletes. LEA occurs when energy intake is insufficient compared to exercise energy expenditure, and LEA-related conditions (e.g., Female Athlete Triad (Triad) and Relative Energy Deficiency in Sport (RED-S)) are associated with a myriad of health and performance consequences. The RED-S model highlights 10 health consequences and 10 performance consequences related to LEA. The independent effect of LCA on health and performance has been under-researched, despite current CHO intake being commonly insufficient in athletes. It is proposed that LCA may not only contribute to LEA but also have independent health and performance consequences in athletes. Furthermore, this review highlights current recommendations for CHO intake, as well as recent data on LCA prevalence and menstrual cycle considerations. A literature review was conducted on PubMed, Science Direct, and ResearchGate using relevant search terms (i.e., "low carbohydrate/energy availability", "female distance runners"). Twenty-one articles were identified and twelve met the inclusion criteria. The total number of articles included in this review is 12, with 7 studies illustrating that LCA was associated with direct negative health and/or performance implications for endurance-based athletes. Several studies included assessed male athletes only, and no studies included a female-only study design. Overall, the cumulative data show that female athletes remain underrepresented in sports science research and that current CHO intake recommendations and strategies may fail to consider female-specific adaptations and hormone responses, such as monthly fluctuations in estrogen and progesterone throughout the menstrual cycle. Current CHO guidelines for female athletes and exercising women need to be audited and explored further in the literature to support female athlete health and performance.

Physical performance during energy deficiency in humans: An evolutionary perspective

Energy deficiency profoundly disrupts normal endocrinology, metabolism, and physiology, resulting in an orchestrated response for energy preservation. As such, despite energy deficit is typically thought as positive for weight-loss and treatment of cardiometabolic diseases during the current obesity pandemic, in the context of contemporary sports and exercise nutrition, chronic energy deficiency is associated to negative health and athletic performance consequences. However, the evidence of energy deficit negatively affecting physical capacity and sports performance is unclear. While severe energy deficiency can negatively affect physical capacity, humans can also improve aerobic fitness and strength while facing significant energy deficit. Many athletes, also, compete at an elite and world-class level despite showing clear signs of energy deficiency. Maintenance of high physical capacity despite the suppression of energetically demanding physiological traits seems paradoxical when an evolutionary viewpoint is not considered. Humans have evolved facing intermittent periods of food scarcity in their natural habitat and are able to thrive in it. In the current perspective it is argued that when facing limited energy availability, maintenance of locomotion and physical capacity are of high priority given that they are essential for food procurement for survival in the habitat where humans evolved. When energetic resources are limited, energy may be allocated to tasks essential for survival (e.g. locomotion) while minimising energy allocation to traits that are not (e.g. growth and reproduction). The current perspective provides a model of energy allocation during energy scarcity supported by observation of physiological and metabolic responses that are congruent with this paradigm.

The Prevalence of Menstrual Cycle Disorders and Menstrual Cycle-Related Symptoms in Female Athletes: A Systematic Literature Review

BACKGROUND

Menstrual cycle (MC) disorders and MC-related symptoms can have debilitating effects on the health and performance of female athletes. As the participation of women in sports continues to increase, understanding the prevalence of a range of MC disorders and MC-related symptoms may guide preventive strategies to protect the health and optimise the performance of female athletes.

OBJECTIVE

To examine the prevalence of MC disorders and MC-related symptoms among female athletes who are not using hormonal contraceptives and evaluate the assessment methods used to identify MC disorders and MC-related symptoms.

METHODS

This systematic review was performed in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA). Six databases were searched until September 2022 for all original research that reported the prevalence of MC disorders and/or MC-related symptoms in athletes not using hormonal contraceptives, which included the definitions of the MC disorders examined, and the assessment methods used. MC disorders included amenorrhoea, anovulation, dysmenorrhoea, heavy menstrual bleeding (HMB), luteal phase deficiency (LPD), oligomenorrhoea, premenstrual syndrome (PMS) and premenstrual dysphoric disorder (PMDD). MC-related symptoms included any affective and physical symptoms related to the MC that do not cause significant personal, interpersonal or functional impairment. The prevalence data across eligible studies were combined, and all studies were qualitatively synthesised to evaluate the assessment methods and tools used to identify MC disorders and MC-related symptoms. The methodological quality of studies was assessed using a modified Downs and Black checklist.

RESULTS

Sixty studies involving 6380 athletes were included. A wide range of prevalence was observed for all types of MC disorders, with a dearth of data on anovulation and LPD. Based on pooled data, dysmenorrhoea (32.3%; range 7.8-85.6%) was the most prevalent MC disorder. Studies reporting MC-related symptoms mostly examined the premenstrual and menstruation phases, where affective symptoms appeared more prevalent than physical symptoms. A larger proportion of athletes reported symptoms during the initial days of menstruation compared with the premenstrual phase. MC disorders and MC-related symptoms were retrospectively assessed using self-report methods in 90.0% of studies. Most studies (76.7%) in this review were graded as moderate quality.

DISCUSSION

MC disorders and MC-related symptoms are commonplace among female athletes, warranting further research examining their impact on performance and preventive/management strategies to optimise athlete health. To increase the quality of future studies, researchers should adopt standardised definitions of MC disorders and assessment methods such as a combination of calendar counting, urinary ovulation tests and a mid-luteal phase serum progesterone measurement when assessing menstrual function. Similarly, standardised diagnostic criteria should be used when examining MC disorders such as HMB, PMS and PMDD. Practically, implementing prospective cycle monitoring that includes ovulation testing, mid-luteal blood sampling (where feasible) and symptom logging throughout the MC could support athletes and practitioners to promptly identify and manage MC disorders and/or MC-related symptoms.

TRIAL REGISTRATION

This review has been registered in the PROSPERO database (CRD42021268757).

Review of the scientific rationale, development and validation of the International Olympic Committee Relative Energy Deficiency in Sport Clinical Assessment Tool: V.2 (IOC REDs CAT2)-by a subgroup of the IOC consensus on REDs

Relative Energy Deficiency in Sport (REDs) has various different risk factors, numerous signs and symptoms and is heavily influenced by one's environment. Accordingly, there is no singular validated diagnostic test. This 2023 International Olympic Committee's REDs Clinical Assessment Tool-V.2 (IOC REDs CAT2) implements a three-step process of: (1) initial screening; (2) severity/risk stratification based on any identified REDs signs/symptoms (primary and secondary indicators) and (3) a physician-led final diagnosis and treatment plan developed with the athlete, coach and their entire health and performance team. The CAT2 also introduces a more clinically nuanced four-level traffic-light (green, yellow, orange and red) severity/risk stratification with associated sport participation guidelines. Various REDs primary and secondary indicators have been identified and 'weighted' in terms of scientific support, clinical severity/risk and methodological validity and usability, allowing for objective scoring of athletes based on the presence or absence of each indicator. Early draft versions of the CAT2 were developed with associated athlete-testing, feedback and refinement, followed by REDs expert validation via voting statements (ie, online questionnaire to assess agreement on each indicator). Physician and practitioner validity and usability assessments were also implemented. The aim of the IOC REDs CAT2 is to assist qualified clinical professionals in the early and accurate diagnosis of REDs, with an appropriate clinical severity and risk assessment, in order to protect athlete health and prevent prolonged and irreversible outcomes of REDs.

Republication of "Stress Fractures of the Foot and Ankle in Athletes"

Stress fractures of the foot and ankle are common injuries in athletes. Management differs considerably based on fracture location and predisposing factors. Repetitive loading of the foot and ankle in athletes should result in physiologic bone remodeling in accordance with Wolff's law. However, when there is not sufficient time for complete healing to occur before additional loads are incurred, this process can instead lead to stress fracture. Assessment of the athlete's training regimen and overall bone health is paramount to both the discovery and treatment of these injuries, although diagnosis is often delayed in the setting of normal-appearing initial radiographs. While most stress fractures of the foot or ankle can usually be treated nonoperatively with a period of activity modification, fractures in certain locations are considered "high risk" due to poor intrinsic healing and may warrant more proactive operative management.

Tarsal Navicular Bone Stress Injuries: A Multicenter Case Series Investigating Clinical Presentation, Diagnostic Approach, Treatment, and Return to Sport in Adolescent Athletes

BACKGROUND

Tarsal navicular bone stress injuries (BSIs) are considered "high risk" because of prolonged healing times and higher rates of nonunion in adult populations but, to our knowledge, have not been comprehensively examined in adolescent athletes.

PURPOSE

To describe the characteristics of tarsal navicular BSIs in adolescents.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A retrospective analysis of patients aged 10 to 19 years with a radiographically diagnosed tarsal navicular BSI was performed at 8 academic centers over a 9-year study period. Age, sex, body mass index (BMI), primary sport, physical examination findings, imaging, treatment, surgical technique, return-to-sport time, and complications were analyzed.

RESULTS

Among 110 patients (mean age, 14.7 ± 2.7 years; 65% female), common primary sports were cross-country/track and field (29/92 [32%]) and gymnastics/dance (25/92 [27%]). Grade 4 BSIs were identified in 44% (48/110) of patients, with fracture lines present on radiography or magnetic resonance imaging. Nonoperative treatment (mean age, 14.4 ± 2.6 years), consisting of protected weightbearing and either a protective boot (69/88 [78%]) or a cast (19/88 [22%]), was trialed in all patients and was successful in 94 patients (85%). Operative treatment (mean age, 17.1 ± 1.4 years) was ultimately pursued for 16 patients (15%). Patients who required surgery had a higher BMI and a higher percentage of fracture lines present on imaging (nonoperative: 36/94 [38%]; operative: 14/16 [88%]). The median time to return to weightbearing, running, and full sport was significantly longer in duration for the operative group than the nonoperative group (P <.05). Complications associated with surgery included 1 case each of delayed union, nonunion, and painful implants, the latter of which required secondary surgery.

CONCLUSION

Adolescent tarsal navicular BSIs were identified most commonly in female patients in leanness sports. Adolescents who required surgery were more likely to be older, have higher BMIs, and have grade 4 BSIs, and they returned to sport within a median of 5 months after single- or double-screw fixation with a low risk of postoperative complications. A better understanding of the presenting signs and symptoms and appropriate diagnostic imaging of navicular BSIs may lead to an earlier diagnosis and improved outcomes.

Healthy Runner Project: a 7-year, multisite nutrition education intervention to reduce bone stress injury incidence in collegiate distance runners

Objectives

We evaluated the effect of a nutrition education intervention on bone stress injury (BSI) incidence among female distance runners at two NCAA Division I institutions.

Methods

Historical BSI rates were measured retrospectively (2010-2013); runners were then followed prospectively in pilot (2013-2016) and intervention (2016-2020) phases. The primary aim was to compare BSI rates in the historical and intervention phases. Pilot phase data are included only for descriptive purposes. The intervention comprised team nutrition presentations focused on optimising energy availability plus individualised nutrition sessions for runners with elevated Female Athlete Triad risk. Annual BSI rates were calculated using a generalised estimating equation Poisson regression model adjusted for age and institution. Post hoc analyses were stratified by institution and BSI type (trabecular-rich or cortical-rich).

Results

The historical phase included 56 runners and 90.2 person-years; the intervention phase included 78 runners and 137.3 person-years. Overall BSI rates were not reduced from the historical (0.52 events per person-year) to the intervention (0.43 events per person-year) phase. Post hoc analyses demonstrated trabecular-rich BSI rates dropped significantly from 0.18 to 0.10 events per person-year from the historical to intervention phase (p=0.047). There was a significant interaction between phase and institution (p=0.009). At Institution 1, the overall BSI rate dropped from 0.63 to 0.27 events per person-year from the historical to intervention phase (p=0.041), whereas no decline was observed at Institution 2.

Conclusion

Our findings suggest that a nutrition intervention emphasising energy availability may preferentially impact trabecular-rich BSI and depend on team environment, culture and resources.

Link Between the Female Athlete Triad and Gymnastics-Related Injury in Retired Collegiate Gymnasts

OBJECTIVES

To compare gymnastics-related injuries between former collegiate gymnasts who did and did not report components of the female athlete triad (Triad) during college, including disordered eating or menstrual irregularity. We hypothesized that athletes reporting these 2 triad symptoms would have higher rates of time loss injury and injuries requiring surgery.

DESIGN

Retrospective case-control.

SETTING

Online survey.

PATIENTS

Four hundred seventy former collegiate gymnasts.

INTERVENTIONS

Athletes completed online survey distributed through social media.

MAIN OUTCOME MEASURES

Participants were grouped based on self-reported menstrual irregularity and disordered eating during college. We compared time loss injuries, injuries resulting in surgery, and injury locations between the groups using χ2 analyses.

RESULTS

Seventy percent (n = 328) of participants in this study reported a time loss college injury without surgery, and 42% (n = 199) reported an injury during college that required surgical treatment. A significantly greater proportion of gymnasts with only disordered eating reported a time loss gymnastics injury (without surgery) compared with those who reported only menstrual irregularity during college (79% vs 64%; P =0 .03). A significantly greater proportion of the disordered eating-only group reported a spine injury compared with the menstrual irregularity-only group (P = 0.007) and the group who reported neither menstrual irregularity nor disordered eating (P = 0.006).

CONCLUSIONS

College gymnasts who experienced disordered eating were more likely to experience a nonsurgical time loss injury while in college, as well as spine injury compared with those with menstrual irregularity. Sports medicine providers should be aware of the association between injuries and individual components of Triad in gymnasts beyond bone stress injuries.

Support for inadvertent undereating in female adolescent athletes with clinical indicators of low energy availability

OBJECTIVES

This study evaluated pathways to low energy availability in a sample of female adolescent athletes (n = 464).

DESIGN

Cross-sectional.

METHODS

Participants (age 13-18 y) underwent assessments for height, weight, eating attitudes and behaviors, and menstrual function. Bone mineral density and body composition were evaluated by dual-energy x-ray absorptiometry in a subset of participants (n = 209). Athletes were classified with clinical indicators of low energy availability if they met criteria for 1) primary or secondary amenorrhea or 2) clinical underweight status (body mass index-for-age < 5th percentile). Disordered eating was assessed using the Eating Disorder Examination Questionnaire.

RESULTS

Thirty (6.5%) athletes exhibited clinical indicators of low energy availability, with higher estimates in leanness than non-leanness sports (10.9% vs. 2.1%, p < 0.005). Among athletes with clinical indicators of low energy availability, 80% (n = 24) did not meet criteria for disordered eating, eating disorder, or report the desire to lose weight. Athletes with (vs. without) clinical indicators of low energy availability exhibited lower lumbar spine (-1.30 ± 1.38 vs. -0.07 ± 1.21, p < 0.001) and total body (-0.30 ± 0.98 vs. 0.53 ± 0.97, p < 0.006) bone mineral density Z-scores.

CONCLUSIONS

A majority of female adolescent athletes with clinical indicators of low energy availability did not exhibit characteristics consistent with intentional dietary restriction, supporting the significance of the inadvertent pathway to low energy availability and need for increased nutrition education in this population.

Current risks factors and emerging biomarkers for bone stress injuries in military personnel

INTRODUCTION

Bone stress injuries (BSIs) have plagued the military for over 150 years; they afflict around 5 to 10% of military recruits, more so in women, and continue to place a medical and financial burden on defence. While the tibia generally adapts to the rigours of basic military training, the putative mechanisms for bone maladaptation are still unclear.

METHODS

This paper provides a review of the published literature on current risk factors and emerging biomarkers for BSIs in military personnel; the potential for biochemical markers of bone metabolism to monitor the response to military training; and, the association of novel biochemical 'exerkines' with bone health.

RESULTS

The primary risk factor for BSI in military (and athletic) populations is too much training, too soon. Appropriate physical preparation before training will likely be most protective, but routine biomarkers will not yet identify those at risk. Nutritional interventions will support a bone anabolic response to training, but exposure to stress, sleep loss, and medication is likely harmful to bone. Monitoring physiology using wearables-ovulation, sleep and stress-offer potential to inform prevention strategies.

CONCLUSIONS

The risk factors for BSIs are well described, but their aetiology is very complex particularly in the multi-stressor military environment. Our understanding of the skeletal responses to military training is improving as technology advances, and potential biomarkers are constantly emerging, but sophisticated and integrated approaches to prevention of BSI are warranted.

The Relationship Between Eating Disorders, Disordered Eating, and Injury in Athletes: A Critically Appraised Topic

CLINICAL SCENARIO

Eating disorders (EDs) and disordered eating (DE) result in numerous physical and psychological complications for female and male athletes. Besides bone-related injury, little research exists investigating what injuries EDs and/or DE contribute to.

CLINICAL QUESTION

Are EDs and/or DE a risk factor for injury incidence in athletes?

SUMMARY OF KEY FINDINGS

We searched for prospective studies assessing EDs or DE as a risk factor for injury in female or male athletes high school age and older. Our search returned 5 studies. One study found Eds, or DE were not a risk for any type of injury in female cross-country and track-and-field athletes. Two studies found a possible relationship between EDs or DE, as one contributing factor of others, in the incidence of bone stress injuries (BSIs) in female athletes who compete in various sports. One study found female, but not male, cross-country and track-and-field athletes with a history of EDs were more at risk for stress fractures than those without a history. One study found Eds, or DE were not a risk for BSI in female runners and triathletes.

CLINICAL BOTTOM LINE

Large and important gaps in the literature exist investigating injuries related to EDs or DE outside of BSIs. There is low-moderate evidence that EDs and/or DE are either a sole, or contributing, risk factor for BSIs in female athletes.

STRENGTH OF RECOMMENDATION

Grade B evidence exists to support the idea that EDs and/or DE are a risk factor for a specific type of injury (BSI) in female athletes only.

Sex-related differences in hip and groin injuries in adult runners: a systematic review

OBJECTIVES

Hip/groin running-related injuries (RRIs) are relatively uncommon. It is unclear if runners of either sex are disproportionately affected. Our objective was to systematically review differences in hip/groin RRIs between males and females.

DATA SOURCES

A structured and comprehensive search of four medical literature databases was performed (PubMed, Embase, Ovid Medline, and CINAHL). Terms searched were as follows: risk, epidemiology, hip injury, groin injury, overuse injury, running, sprinting, and track and field.

STUDY SELECTION

Studies reporting sex-specific data on hip/groin RRIs in adult runners were included. Data was extracted and reviewed independently by two authors.

STUDY APPRAISAL AND DATA SYNTHESIS

Sex-specific injury rates, risk factors, and return to sport (RTS) following hip/groin RRI were extracted. Risk of bias was assessed using the Joanna-Briggs Institute Critical Appraisal Tool.

RESULTS

Ten studies with 7,353 total runners were included: 2,315 (47%) males and 2,559 (53%) females. The mean age of the included runners was 37.3 ± 8.9 years and the mean weekly running distance was 10.4 ± 8.4 km. Hip/groin injuries comprised 10.1% (491/4,874) of total RRIs, including 6.3% of RRIs sustained by males and 11.0% by females. Three studies reported significantly higher rates of hip/groin RRIs in female runners. One study reported significantly higher rates of gluteus medius and adductor RRIs for females and males, respectively. One study identified female sex as an independent risk factor for hip/groin RRIs. Three studies reported on RTS after hip/groin RRIs: the pooled RTS rate was 81.4% (57/70) at 1 to 368 days after injury.

LIMITATIONS

Data was pooled when possible; however, there was considerable clinical, methodological, and statistical heterogeneity across studies.

CONCLUSIONS

Hip/groin RRIs comprise a greater percentage of total injuries among injured female runners relative to males. Females may be at a higher risk for sustaining hip/groin RRIs though more research on risk factors and RTS is needed.

Nutrition Education Curriculum Promotes Adolescent Runners' Self-Efficacy, Knowledge, and Intake of Nutrient-Rich Carbohydrate Foods

BACKGROUND

Endurance runners exhibit an elevated prevalence of low bone mass and characteristics consistent with undernourishment.

OBJECTIVE

This quasi-experimental, pretest-posttest design study evaluated the efficacy of a 4-week nutrition education curriculum to optimize nutrition knowledge, self-efficacy, and the intake of nutrient-rich carbohydrate foods.

METHODS

Forty-eight adolescent endurance runners, age 15.7 ± 1.2 y, from two high schools in Southern California were recruited to complete four, weekly lessons addressing the quantity, quality, and timing of carbohydrate intake. Differences in pre- compared to post-intervention nutrition knowledge and self-efficacy to consume nutrient-rich carbohydrate foods were evaluated using paired samples t-tests. Qualitative coding of open-response questions explored changes in food intake behaviors reported by runners during the intervention.

RESULTS

The percent of nutrition knowledge questions answered correctly increased after Lessons 1 and 2 (59.0% ± 20.0% pre- vs. 81.9% ± 22.8% post-Lesson 1; 44.7% ± 13.7% pre- vs. 74.5% ± 17.4% post-Lesson 2, P<.001) and the number of identified nutrient-rich carbohydrate foods (8.7 ± 2.7 vs. 12.4 ± 2.3, P < 0.001). Self-efficacy scores improved after all lessons (P<.001). After Lesson 2, 84% (n = 27/32) of runners increased the carbohydrate included in a snack or meal; after Lesson 4, 85% (n = 29/34) added a post-exercise snack. Frequent themes identified from questions addressing dietary changes included increasing quantity and quality of carbohydrates in snacks and meals and being more aware of food choices.Conclusions: Findings suggest that the curriculum enhanced nutrition knowledge, self-efficacy, and dietary behaviors related to intake of nutrient-dense carbohydrate foods in adolescent runners.

Medical and physiological complications of exercise for individuals with an eating disorder: A narrative review

Individuals with eating disorders (ED) experience prolonged malnutrition, binge episodes, and compensatory behaviours that affect every organ system. Psychological and physiological symptoms are worsened with comorbid dysfunctional exercise, seen in up to 80% of those with an ED. Although return to exercise is an important component of treatment and recovery, little is known about the contraindications and risks of exercise engagement specific to those with an ED. This paper provides a comprehensive narrative review of the medical and physiological complications of engaging in exercise during ED treatment and outlines when exercise may be contraindicated or used in modified or cautionary ways. We conducted a literature search on MEDLINE, PubMed, and PsychArticles to identify relevant articles, which yielded six categories of medical and physiological complications of ED that may be exacerbated by exercise: energy availability, cardiovascular health, electrolyte abnormalities, biomedical function markers, sex hormones, and body composition. We summarize the evidence for these complications for readers and offer an initial set of recommendations for incorporating exercise during ED treatment based on our findings. This review may serve as a resource for members of ED treatment teams to help evaluate more readily and confidently whether exercise is safe for individual patients and when modifications and caution may be warranted.

Dance-Related Foot and Ankle Injuries and Pathologies

Dancers are highly vulnerable to injuries due to high dynamic overload, extreme positions and motions, and excessive use. Increased load at the forefoot with jumping and high-impact lands can cause sesamoiditis and stress fractures of the metatarsals. Significant plantarflexion can lead to posterior joint impingement and flexor hallucis longus tendonitis, whereas forced dorsiflexion can cause anterior joint impingement. Most pathologies can be diagnosed on physical examination and various imaging modalities. Treatment should be tailored to the dancers' needs and should begin with a course of conservative therapy with immobilization, physical therapy, and activity cessation.

Stress Injuries in the Athlete

Stress fractures are a common injury that present in athletes because of the high intensity and repetitive nature of many sports. These injuries require a high index of suspicion in the treating clinician to allow for timely management. Though most low-risk fractures heal well with conservative management, high-risk stress fractures as well as any fracture in the elite athlete may warrant surgical intervention as well as an augmented treatment and rehabilitation regimen.

The Warburg effect in osteoporosis: Cellular signaling and epigenetic regulation of energy metabolic events to targeting the osteocalcin for phenotypic alteration

Osteoporosis is a silent disease of skeletal morphology that induces fragility and fracture risk in aged persons irrespective of gender. Juvenile secondary osteoporosis is rare and is influenced by familial genetic abnormalities. Despite the currently available therapeutic options, more-acute treatments are in need. Women suffer from osteoporosis after menopause, which is characterized by a decline in the secretion of sex hormones in the later phase of life. Several studies in the past two decades emphasized hormone-related pathways to combat osteoporosis. Some studies partially examined energy-related pathways, but achieving a more vivid picture of metabolism and bone remodeling in terms of the Warburg phenomenon is still warranted. Each cell requires sufficient energy for cellular propagation and growth; in particular, osteoporosis is an energy-dependent mechanism affected by a decreased cellular mass of the bone morphology. Energy utilization is the actual propagation of such diseases, and narrowing down these criteria will hopefully provide clues to formulate better therapeutic strategies. Oxidative glycolysis is a particular type of energy metabolic pathway in cancer cells that influences cellular proliferation. Therefore, the prospect of utilizing collective glucose metabolism by inducing the Warburg effect may improve cell propagation. The benefits of utilizing the energy from the Warburg effect may be a difficult task. However, it seems to improve their effectiveness in the osteoblast phenotype by connecting the selected pathways such as WNT, Notch, AKT, and Insulin signaling by targeting osteocalcin resulting in phenotypic alteration. Osteocalcin directs ATP utilization through the sclerostin SOST gene in the bone microenvironment. Thus, selective activation of ATP production involved in osteoblast maturation remains a prime strategy to fight osteoporosis.

Stress fractures

Stress fractures (SF) represent 10%-20% of all injuries in sport medicine. An SF occurs when abnormal and repetitive loading is applied on normal bone: The body cannot adapt quickly enough, leading to microdamage and fracture. The etiology is multifactorial with numerous risk factors involved. Diagnosis of SF can be achieved by identifying intrinsic and extrinsic factors, obtaining a good history, performing a physical exam, and ordering laboratory and imaging studies (magnetic resonance imaging is the current gold standard). Relative energy deficiency in sport (RED-S) is a known risk factor. In addition, for women, it is very important know the menstrual status to identify long periods of amenorrhea in the past and the present. Early detection is important to improve the chance of symptom resolution with conservative treatment. Common presentation involves complaints of localized pain, with or without swelling, and tenderness on palpation of bony structures that begins earlier in training and progressively worsens with activity over a 2- to 3-week period. Appropriate classification of SF based on type, location, grading, and low or high risk is critical in guiding treatment strategies and influencing the time to return to sport. Stress injuries at low-risk sites are typically managed conservatively. Studies have suggested that calcium and vitamin D supplementation might be helpful. Moreover, other treatment regimens are not well established. Understanding better the pathophysiology of SFs and the potential utility of current and future bone-active therapeutics may well yield approaches that could treat SFs more effectively.

Relationship of muscle power and bone mineral density with the α-actinin-3 R577X polymorphism in Japanese female athletes from different sport types: An observational study

The aim of this study was to clarify the relationships between muscle power and bone mineral density (BMD) and the α-actinin-3 (ACTN3) R577X polymorphism in Japanese female collegiate athletes participating in sports with various mechanical-load characteristics. This study included 260 female collegiate athletes involved in 10 competitive sports and 26 controls (mean ages, 19.2 ± 1.2 and 19.7 ± 1.3 years, respectively). The sports were classified into 3 categories (low-impact, multidirectional, and high-impact) based on the exercise load characteristics. Data on sports participation and competition experience were obtained through a questionnaire-type survey. The maximum anaerobic power (MAnP) test was performed to measure muscle power. The total body BMD was measured using dual-energy X-ray absorptiometry. The ACTN3 R577X polymorphism (rs1815739) was analyzed using a TaqMan® assay. The multidirectional sports participants with the RR genotype of the ACTN3 R577X polymorphism had a higher BMD than those with the RX and RX + XX genotypes (P = .018 and P = .003, respectively). The RR genotype was also associated with a higher MAnP than those with the RX + XX genotypes (P = .035). No other variables related to BMD and MAnP were significantly different. Our results suggests that the RR genotype may confer high trainability for BMD and muscle power in Japanese female collegiate athletes participating in multidirectional sport types. However, these associations were not found in the athletes participating in the low- and high-impact sport types.

Comparison of Ultrasonography to MRI in the Diagnosis of Lower Extremity Bone Stress Injuries: A Prospective Cohort Study

OBJECTIVE

To determine the sensitivity and specificity of ultrasound imaging (USI) compared to the reference-standard of MRI in the diagnosis of bone stress injury (BSI).

METHODS

A prospective blinded cohort study was conducted. Thirty seven patients who presented to an academic sports medicine clinic from 2016 to 2020 with suspected lower-extremity BSI on clinical exam underwent both magnetic resonance imaging (MRI) and USI. Participant characteristics were collected including age, gender and sport. Exclusion criteria included contraindication for dedicated MRI, traumatic fracture, or severe tendon or ligamentous injury. The primary outcome measure was BSI diagnosis by USI. An 8-point assessment system was utilized on USI for diagnosis of BSI, and the Fredericson and Nattiv²² criteria were applied to classify MRI findings.

RESULTS

Thirty seven participants who met study criteria were consented to participate. All participants completed baseline measures. Using MRI, there were 30 (81%) athletes with a positive and seven participants with a negative BSI diagnosis. The most common BSIs in the study were in the metatarsal (54%) and tibia (32%). Compared to MRI, USI demonstrated 0.80 sensitivity (95% confidence interval [CI], 0.61-0.92) and 0.71 specificity (95% CI, 0.29-0.96) in detecting BSI, with a positive predictive value of 0.92 (95% CI, 0.75-0.99) and negative predictive value of 0.45 (95% CI, 0.17-0.77).

CONCLUSIONS

USI is a potentially useful point-of-care tool for practicing sports medicine providers to combine with their clinical evaluation in the diagnosis of BSIs. Further research is ongoing to determine the role of USI in follow-up care and return-to-play protocols.

Impaired Bone Microarchitecture at Distal Radial and Tibial Reference Locations Is Not Related to Injury Site in Athletes With Bone Stress Injury

BACKGROUND

Bone stress injuries (BSIs) are common sports injuries that occur because of an imbalance between microdamage accumulation and removal through bone remodeling. The underlying bone phenotype has been assumed to be a contributing factor. However, the bone microarchitecture of athletes with BSI is not well characterized, and no study has investigated whether impaired bone microarchitecture is associated with bone composition or anatomic site of injury.

PURPOSE/HYPOTHESIS

This cross-sectional study characterizes the bone microarchitecture at distal radial and tibial reference locations in athletes with BSI. Based on previous dual-energy X-ray absorptiometry (DXA) findings, the aim was to compare anatomic injury sites, hypothesizing that athletes with BSIs in bones with greater trabecular composition show impaired bone microarchitecture parameters compared with those with BSIs in bones with greater cortical composition.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Athletes who had presented to our outpatient clinic because of a high-grade BSI (ie, stress fracture) were retrospectively included. Blood and urine samples were collected. Areal bone mineral density (aBMD) was assessed by DXA at the lumbar spine and both hips. Bone microarchitecture was analyzed by high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal radius and tibia. HR-pQCT parameters were expressed in relation to available sex-, age-, and device-adjusted reference values and compared with a cohort of 53 age- and sex-matched controls.

RESULTS

In total, 53 athletes had a BSI of the foot (n = 20), tibia/fibula (n = 18), pelvis (n = 9), femur (n = 5), or sternum (n = 1). Based on DXA measurements, a Z-score of -1.0 or lower was found in 32 of 53 (60.4%) of the athletes, of whom 16 of 53 (30.2%) had a Z score -2.0 or lower. While an impairment of cortical area (P = .034 and P = .001) and thickness (P = .029 and P < .001) was detected at the distal radius and tibia in the BSI cohort compared with controls, no differences in BMD or bone microarchitecture were observed between anatomic injury sites. Furthermore, no difference was revealed when BSIs were grouped into cortical- and trabecular-rich sites.

CONCLUSION

Reduced aBMD and impaired cortical bone microarchitecture were present in a considerable number of athletes with BSI. Neither aBMD nor bone microarchitecture was related to the injury site, highlighting the multifactorial etiology of BSI.

Female Athlete Triad Risk Factors Are More Strongly Associated With Trabecular-Rich Versus Cortical-Rich Bone Stress Injuries in Collegiate Athletes

Background:

Bone stress injuries (BSIs) are common in athletes. Risk factors for BSI may differ by skeletal anatomy and relative contribution of trabecular-rich and cortical-rich bone.

Hypothesis:

We hypothesized that Female Athlete Triad (Triad) risk factors would be more strongly associated with BSIs sustained at trabecular-rich versus cortical-rich skeletal sites.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

The study population comprised 321 female National Collegiate Athletic Association Division I athletes participating in 16 sports from 2008 to 2014. Triad risk factors and a Triad cumulative risk score were assessed using responses to preparticipation examination and dual energy x-ray absorptiometry to measure lumbar spine and whole-body bone mineral density (BMD). Sports-related BSIs were diagnosed by a physician and confirmed radiologically. Athletes were grouped into those sustaining a subsequent trabecular-rich BSI, a subsequent cortical-rich BSI, and those without a BSI. Data were analyzed with multinomial logistic regression adjusted for participation in cross-country running versus other sports.

Results:

A total of 19 participants sustained a cortical-rich BSI (6%) and 10 sustained a trabecular-rich BSI (3%) over the course of collegiate sports participation. The Triad cumulative risk score was significantly related to both trabecular-rich and cortical-rich BSI. However, lower BMD and weight were associated with significantly greater risk for trabecular-rich than cortical-rich BSIs. For every value lower than 1 SD, the odds ratios (95% CIs) for trabecular-rich versus cortical-rich BSI were 3.08 (1.25-7.56) for spine BMD; 2.38 (1.22-4.64) for whole-body BMD; and 5.26 (1.48-18.70) for weight. Taller height was a significantly better predictor of cortical-rich than trabecular-rich BSI.

Conclusion:

The Triad cumulative risk score was significantly associated with both trabecular-rich and cortical-rich BSI, but Triad-related risk factors appeared more strongly related to trabecular-rich BSI. In particular, low BMD and low weight were associated with significantly higher increases in the risk of trabecular-rich BSI than cortical-rich BSI. These findings suggest Triad risk factors are more common in athletes sustaining BSI in trabecular-rich than cortical-rich locations.

Prevalence and factors associated with bone stress injury in middle school runners

BACKGROUND

Bone stress injury (BSI) in youth runners is clinically important during times of skeletal growth and is not well studied.

OBJECTIVE

To evaluate the prevalence, anatomical distribution, and factors associated with running-related BSI in boy and girl middle school runners.

DESIGN

Retrospective cross-sectional study.

SETTING

Online survey distributed to middle school runners.

METHODS

Survey evaluated BSI history, age, grade, height, weight, eating behaviors, menstrual function, exercise training, and other health characteristics.

MAIN OUTCOME MEASUREMENTS

Prevalence and characteristics associated with history of BSI, stratified by cortical-rich (eg, tibia) and trabecular-rich (pelvis and femoral neck) locations.

PARTICIPANTS

2107 runners (n = 1250 boys, n = 857 girls), age 13.2 ± 0.9 years.

RESULTS

One hundred five (4.7%) runners reported a history of 132 BSIs, with higher prevalence in girls than boys (6.7% vs 3.8%, p = .004). The most common location was the tibia (n = 51). Most trabecular-rich BSIs (n = 16, 94% total) were sustained by girls (pelvis: n = 6; femoral neck: n = 6; sacrum: n = 4). In girls, consuming <3 daily meals (odds ratio [OR] = 18.5, 95% confidence interval [CI] = 7.3, 47.4), eating disorder (9.8, 95% CI = 2.0, 47.0), family history of osteoporosis (OR = 6.9, 95% CI = 2.6, 18.0), and age (OR = 1.6, 95% CI = 1.0, 2.6) were associated with BSI. In boys, family history of osteoporosis (OR = 3.2, 95% CI = 1.2, 8.4), prior non-BSI fracture (OR = 3.2, 95% CI = 1.6, 6.7), and running mileage (OR = 1.1, 95% CI = 1.0, 1.1) were associated with BSI. Participating in soccer or basketball ≥2 years was associated with lower odds of BSI for both sexes.

CONCLUSION

Whereas family history of osteoporosis and prior fracture (non-BSI) were most strongly related to BSI in the youth runners, behaviors contributing to an energy deficit, such as eating disorder and consuming <3 meals daily, also emerged as independent factors associated with BSI. Although cross-sectional design limits determining causality, our findings suggest promoting optimal skeletal health through nutrition and participation in other sports including soccer and basketball may address factors associated with BSI in this population.

Imaging-detected bone stress injuries at the Tokyo 2020 summer Olympics: epidemiology, injury onset, and competition withdrawal rate

Background

Prevention and early detection of injuries are essential in optimising sport participation and performance. The aim of this study is to investigate the epidemiology, athlete injury history, and competition withdrawal rate of imaging-detected bone stress injuries during the Tokyo 2020 Olympic Games.

Methods

We collected and analysed imaging and clinical information in athletes with bone stress injuries diagnosed in the Olympic Village polyclinic during the Games. Two physicians independently and retrospectively reviewed all imaging examinations of bone stress injuries.

Results

A total of 11,315 individual athletes from 206 National Olympic Committees competed at the Games, during which 567 MRIs and 352 X-rays were performed at the Olympic Village polyclinic. Radiology examinations revealed four stress fractures and 38 stress reactions in 29 athletes (median age 24 years, range 18–35 years). Of these, 72% of athletes (n = 21) had symptoms before entering the Olympic Village. Bone stress injuries were most common in women (55%), the lower extremities (66%), and track and field athletes (45%). Six athletes (21%) did not start or did not finish their competitions.

Conclusions

This study revealed 42 imaging-detected bone stress injuries in the polyclinic of the Tokyo 2020 Olympic Village. The high proportion of athletes with symptoms before entering the village and the high proportion of competition withdrawals suggests the usefulness of an early MRI examination.

Adiposity as a Risk Factor for Sport Injury in Youth: A Systematic Review

OBJECTIVE

To determine whether high or low adiposity is associated with youth sport-related injury.

DATA SOURCES

Ten electronic databases were searched to identify prospective studies examining the association between adiposity [body mass index (BMI) or body fat] and a future time-loss or medical attention sport-related musculoskeletal injury or concussion in youth aged 20 years and younger. Two independent raters assessed the quality (Downs and Black criteria) and risk of bias (Joanna Briggs Institute Critical Appraisal Tool). Random-effects meta-analyses were used to calculate pooled odds ratio [95% confidence interval (CI)] of injury.

MAIN RESULTS

Of 11 424 potentially relevant records, 38 articles were included with 17 eligible for meta-analyses. In qualitative synthesis, no clear association was identified between adiposity and any sport injury; however, 16/22 studies identified high adiposity as a significant risk factor for lower-extremity injury. Meta-analyses revealed higher BMI in youth with any sport-related injury and lower BMI in youth who developed a bone stress injury (BSI) compared with noninjured controls. The pooled OR (95% CI) examining the association of BMI and injury risk (excluding bone injury) was 1.18 (95% CI: 1.03-1.34). A major source of bias in included articles was inconsistent adjustment for age, sex, and physical activity participation.

CONCLUSIONS

Level 2b evidence suggests that high BMI is associated with greater risk of youth sport injury, particularly lower-extremity injury and excluding BSI or fracture. Although pooled mean differences were low, anthropometric risk of injury seems to be dependent on type and site of injury in youth sport.

Bone mineral density in response to increased energy intake in exercising women with oligomenorrhea/amenorrhea: the REFUEL randomized controlled trial

BACKGROUND

Energy deficiency can result in menstrual disturbances and compromised bone health in women, a condition known as the Female Athlete Triad.

OBJECTIVES

The REFUEL randomized controlled trial assessed the impact of increased energy intake on bone health and menstrual function in exercising women with menstrual disturbances.

METHODS

Exercising women with oligomenorrhea/amenorrhea (Oligo/Amen) were randomly assigned to an intervention group (Oligo/Amen + Cal, n = 40, mean ± SEM age: 21.3 ± 0.5 y; weight: 55.0 ± 1.0 kg; BMI: 20.4 ± 0.3 kg/m2) who increased energy intake 20%-40% above baseline energy needs for 12 mo or a control group (Oligo/Amen Control, n = 36; mean ± SEM age: 20.7 ± 0.5 y; weight: 59.1 ± 1.3 kg; BMI: 21.3 ± 0.4 kg/m2). Energy intake and expenditure, metabolic and reproductive hormones, body composition, and areal bone mineral density (aBMD) were assessed.

RESULTS

Oligo/Amen + Cal improved energy status [increased body mass (2.6 ± 0.4 kg), BMI (0.9 ± 0.2 kg/m2), fat mass (2.0 ± 0.3 kg), body fat percentage (2.7% ± 0.4%), and insulin-like growth factor 1 (37.4 ± 14.6 ng/mL)] compared with Oligo/Amen Control and experienced a greater likelihood of menses (P < 0.05). Total body and spine aBMD remained unchanged (P > 0.05). Both groups demonstrated decreased femoral neck aBMD at month 6 (-0.006 g/cm2; 95% CI: -0.011, -0.0002 g/cm2 ; time main effect P = 0.043) and month 12 (-0.011 g/cm2; 95% CI: -0.021, -0.001 g/cm2; time main effect P = 0.023). Both groups demonstrated a decrease in total hip aBMD at month 6 (-0.006 g/cm2; 95% CI: -0.011, -0.002 g/cm2; time main effect P = 0.004).

CONCLUSIONS

Although higher dietary energy intake increased weight, body fat, and menstrual frequency, bone mineral density was not improved, compared with the control group. The 12-mo intervention may have been too short and the increase in energy intake (∼352 kcal/d), although sufficient to increase menstrual frequency, was insufficient to increase estrogen or improve aBMD. Future research should refine the optimal nutritional and/or pharmacological interventions for the recovery of bone health in athletes and exercising women with Oligo/Amen.This trial was registered at clinicaltrials.gov as NCT00392873.

Medical and Biomechanical Risk Factors for Incident Bone Stress Injury in Collegiate Runners: Can Plantar Pressure Predict Injury?

Background:

Bone stress injury (BSI) is a common reason for missed practices and competitions in elite track and field runners.

Hypothesis:

It was hypothesized that, after accounting for medical risk factors, higher plantar loading during running, walking, and athletic movements would predict the risk of future BSI in elite collegiate runners.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 39 elite collegiate runners (24 male, 15 female) were evaluated during the 2014-2015 academic year to determine the degree to which plantar pressure data and medical history (including Female and Male Athlete Triad risk factors) could predict subsequent BSI. Runners completed athletic movements while plantar pressures and contact areas in 7 key areas of the foot were recorded, and the measurements were reported overall and by specific foot area. Regression models were constructed to determine factors related to incident BSI.

Results:

Twenty-one runners (12 male, 9 female) sustained ≥1 incident BSI during the study period. Four regression models incorporating both plantar pressure measurements and medical risk factors were able to predict the subsequent occurrence of (A) BSIs in female runners, (B) BSIs in male runners, (C) multiple BSIs in either male or female runners, and (D) foot BSIs in female runners. Model A used maximum mean pressure (MMP) under the first metatarsal during a jump takeoff and only misclassified 1 female with no BSI. Model B used increased impulses under the hindfoot and second through fifth distal metatarsals while walking, and under the lesser toes during a cutting task, correctly categorizing 83.3% of male runners. Model C used higher medial midfoot peak pressure during a shuttle run and triad cumulative risk scores and correctly categorized 93.3% of runners who did not incur multiple BSIs and 66.7% of those who did. Model D included lower hindfoot impulses in the shuttle run and higher first metatarsal MMP during treadmill walking to correctly predict the subsequent occurrence of a foot BSI for 75% of women and 100% without.

Conclusion:

The models collectively suggested that higher plantar pressure may contribute to risk for BSI.

Restrictive Eating and Prior Low-Energy Fractures Are Associated With History of Multiple Bone Stress Injuries

Bone stress injuries (BSIs) are common among athletes and have high rates of recurrence. However, risk factors for multiple or recurrent BSIs remain understudied. Thus, we aimed to explore whether energy availability, menstrual function, measures of bone health, and a modified Female Athlete Triad Cumulative Risk Assessment (CRA) tool are associated with a history of multiple BSIs. We enrolled 51 female runners (ages 18-36 years) with history of ≤1 BSI (controls; n = 31) or ≥3 BSIs (multiBSI; n = 20) in this cross-sectional study. We measured lumbar spine, total hip, and femoral neck areal bone mineral density by dual-energy X-ray absorptiometry, bone material strength index using impact microindentation, and volumetric bone mineral density, microarchitecture, and estimated strength by high-resolution peripheral quantitative computed tomography. Participants completed questionnaires regarding medical history, low-energy fracture history, and disordered eating attitudes. Compared with controls, multiBSI had greater incidence of prior low-energy fractures (55% vs. 16%, p = .005) and higher modified Triad CRA scores (2.90 ± 2.05 vs. 1.84 ± 1.59, p = .04). Those with multiBSI had higher Eating Disorder Examination Questionnaire (0.92 ± 1.03 vs. 0.46 ± 0.49, p = .04) scores and a greater percentage difference between lowest and highest body mass at their current height (15.5% ± 6.5% vs. 11.5% ± 4.9% p = .02). These preliminary findings indicate that women with a history of multiple BSIs suffered more prior low-energy fractures and have greater historical and current estimates of energy deficit compared with controls. Our results provide strong rationale for future studies to examine whether subclinical indicators of energy deficit contribute to risk for multiple BSIs in female runners.

The Influence of Low Energy Availability on Bone Mineral Density and Trabecular Bone Microarchitecture of Pubescent Female Athletes: A Preliminary Study

The influence of low energy availability (LEA) on bone mineral density (BMD) and trabecular bone microarchitecture in pubescent female athletes is unclear. This study aimed to investigate the influence of LEA on BMD and trabecular bone microarchitecture in 21 pubescent female athletes (age, 12−15 years; 11 track and field athletes, 10 gymnasts). We used two indices to assess LEA: energy availability and the percent of ideal body weight. Dual-energy X-ray absorptiometry was used to obtain total body less head, lumbar spine BMD Z-scores, and lumbar trabecular bone scores (TBS). Pearson’s or Spearman’s correlation coefficients were used to assess the relationship among EA, percent of ideal body weight, and bone parameters. The threshold for statistical significance was set at p < 0.05. The percent of ideal body weight was significantly correlated with the BMD Z-scores of the total body less head (r = 0.61; p < 0.01), lumbar spine (r = 0.55; p < 0.01), and lumbar TBS (r = 0.47; p = 0.03). However, energy availability was not correlated with bone parameters. These findings suggest that screening for low ideal body weight may be a useful predictor of low BMD and insufficient trabecular bone microarchitecture in pubescent female athletes.

Low energy availability surrogates associated with lower bone mineral density and bone stress injury site

BACKGROUND

Exercise is an osteogenic stimulus that should increase bone mineral density (BMD) and protect against injury. However, some female athletes have lower BMD and increased bone stress injury (BSI) risk. Impaired bone health seen in athletes may be explained by low energy availability as described by concepts of Relative Energy Deficiency in Sport (RED-S) and Female Athlete Triad (Triad).

OBJECTIVE

To elucidate the relationship between RED-S/Triad risk factors and BSI to high-risk (femoral neck, sacrum) and low-risk (other) bones.

DESIGN

Cross-sectional survey and retrospective chart review.

SETTING

Tertiary care academic center.

PATIENTS

Female athletes aged 15-30 years participating in ≥4 h/week of exercise presenting to sports medicine/orthopedics clinic who had a self-reported BSI and available dual-energy x-ray absorptiometry (DXA) measurement of BMD.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASUREMENTS

Location of BSI.

RESULTS

In 127 athletes, high-risk BSI was associated with surrogates of low energy availability (p = .032) and having a DXA Z-score < -1 (p = .035) but not a current/past history of menstrual dysfunction (p = .348). Accumulating RED-S/Triad risk factors increase the odds of incurring a high-risk BSI (p = .048).

CONCLUSIONS

Adolescent/young female athletes who sustain BSI at high-risk sites (femoral neck, sacrum) may have underlying risk factors (eg, low energy availability, poor overall bone health) that should prompt further workup and referral to optimize health in these athletes.

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.

Bone stress injuries

Bone stress injuries, including stress fractures, are overuse injuries that lead to substantial morbidity in active individuals. These injuries occur when excessive repetitive loads are introduced to a generally normal skeleton. Although the precise mechanisms for bone stress injuries are not completely understood, the prevailing theory is that an imbalance in bone metabolism favours microdamage accumulation over its removal and replacement with new bone via targeted remodelling. Diagnosis is achieved by a combination of patient history and physical examination, with imaging used for confirmation. Management of bone stress injuries is guided by their location and consequent risk of healing complications. Bone stress injuries at low-risk sites typically heal with activity modification followed by progressive loading and return to activity. Additional treatment approaches include non-weight-bearing immobilization, medications or surgery, but these approaches are usually limited to managing bone stress injuries that occur at high-risk sites. A comprehensive strategy that integrates anatomical, biomechanical and biological risk factors has the potential to improve the understanding of these injuries and aid in their prevention and management.

Age and Female Sex Are Important Risk Factors for Stress Fractures: A Nationwide Database Analysis

BACKGROUND

Stress fractures are caused by micro-trauma due to repetitive stress on bone, common in active individuals and athletes. Previous studies demonstrate that the weightbearing bones of the lower extremities incur stress fractures most often, especially in women and older adults.

HYPOTHESIS

Prior literature does not quantify the difference in frequency of stress fractures among different genders, age groups, or body mass indices (BMIs). We hypothesized that older female patients would have higher rates of lower extremity stress fractures than male patients.

STUDY DESIGN

Epidemiological research.

LEVEL OF EVIDENCE

Level 3.

METHODS

Records of female and male patients with lower extremity stress fractures from 2010 to 2018 were identified from the PearlDiver administrative claims database using the International Classification of Diseases (ICD)-9/ICD-10 codes. Stress fractures were classified by ICD-10 diagnosis codes to the tibial bone, proximal femur, phalanges, and other foot bones. Comorbidities were incorporated into a regression analysis.

RESULTS

Of 41,257 stress fractures identified, 30,555 (70.1%) were in women and 10,702 (25.9%) were in men. Our sample was older (>60 years old) (37.3%) and not obese (BMI <30 kg/m², 37.1%). A greater proportion of female patients with stress fracture were older (P < 0.001) and had foot stress fractures (P < 0.001), while a greater proportion of male patients with stress fracture were younger than 19 years (P < 0.001) and had metatarsal (P < 0.001), hip (P = 0.002), and tibia stress fractures (P < 0.001).

CONCLUSION

Stress fractures commonly occur in women and older adults with low BMIs. Metatarsal and tibia stress fractures were the most common, and a greater proportion of women had foot stress fractures.

CLINICAL RELEVANCE

Our study examined the large-scale prevalence of different lower extremity stress fractures among a wide patient population sample of varying ages and BMIs. These findings can help clinicians identify active populations at greater risk for stress fracture injuries.

Maternal Pre-Pregnancy Nutritional Status and Physical Activity Levels and a Sports Injury Reported in Children: A Seven-Year Follow-Up Study

Objective: Our aim was to analyze dose–response associations between maternal pre-pregnancy body mass index and physical activity levels with childhood sports injury rates. Methods: Participants included pre-pregnant mothers (n = 4811) and their children at the age of 7 years (n = 3311). Maternal anthropometry (height, weight, and body mass index), time spent in physical activity, and education level were recorded. All sports injuries were defined as injuries reported in the past year by the children at the age of 7 years. Results: Children whose mothers were overweight/obese in the pre-pregnancy period were 2.04 (OR = 2.04, 95% CI = 1.12–3.71) times more likely to report a sports injury at the age of 7 years. Underweight mothers exhibited a 74% decrease in the odds of their children reporting a sports injury at follow-up (OR = 0.26, 95% CI = 0.10–0.68). Finally, an increase in maternal physical activity across the last three quartiles was associated with a lower odds of sports injuries. Conclusions: The risk of reporting a sports injury was greater for children whose mothers were overweight/obese in the pre-pregnancy period. However, there was a lower risk with both maternal underweight status and increasing minutes of physical activity.

Tibial Bone Geometry Is Associated With Bone Stress Injury During Military Training in Men and Women

Bone stress injuries (BSI) are a common musculoskeletal condition among exercising and military populations and present a major burden to military readiness. The purpose of this investigation was to determine whether baseline measures of bone density, geometry, and strength, as assessed via peripheral quantitative computed tomography (pQCT), are predictive of tibial BSI during Marine Officer Candidates School training. Tibial pQCT scans were conducted prior to the start of physical training (n = 504; Male n = 382; Female n = 122) to measure volumetric bone mineral density (vBMD), geometry, robustness, and estimates of bone strength. Bone parameters were assessed at three tibial sites including the distal metaphysis (4% of tibial length measured from the distal endplate), mid-diaphysis (38% of tibial length measured from the distal endplate), and proximal diaphysis (66% of tibial length measured from the distal endplate). Injury surveillance data was collected throughout training. Four percent (n = 21) of the sample were diagnosed with a BSI at any anatomical site during training, 10 injuries were of the tibia. Baseline bone parameters were then tested for associations with the development of a tibial BSI during training and it was determined that cortical bone measures at diaphyseal (38 and 66%) sites were significant predictors of a prospective tibial BSI. At the mid-diaphysis (38% site), in a simple model and after adjusting for sex, age, and body size, total area [Odds Ratio (OR): 0.987, 0.983], endosteal circumference (OR: 0.853, 0.857), periosteal circumference (OR: 0.863, 0.824), and estimated bending strength (SSI; OR: 0.998, 0.997) were significant predictors of a BSI during training, respectively, such that lower values were associated with an increased likelihood of injury. Similarly, at the proximal diaphysis (66% site), total area (OR: 0.989, 0.985), endosteal circumference (OR: 0.855, 0.854), periosteal circumference (OR: 0.867, 0.823), robustness (OR: 0.007, 0.003), and SSI (OR: 0.998, 0.998) were also significant predictors of BSI in the simple and adjusted models, respectively, such that lower values were associated with an increased likelihood of injury. Results from this investigation support that narrower bones, with reduced circumference, lower total area, and lower estimated strength are associated with increased risk for tibial BSI during military training.

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.

Anthropometric Factors Associated With Bone Stress Injuries in Collegiate Distance Runners: New Risk Metrics and Screening Tools?

BACKGROUND

Lower limb bone stress injury (BSI) of the pelvis, femur, and tibia is prevalent in collegiate track and field distance runners. Bone mineral density (BMD), body composition (BComp), and anthropometric parameters before initial collegiate injury have not been compared between runners with BSI and their noninjured counterparts.

PURPOSE

To characterize bone health in relation to BComp and anthropometric measurements from total-body dual x-ray absorptiometry (DXA) scans in collegiate male and female distance runners before BSI and develop BMD prediction models.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Distance runners (N = 79) from a single university track and field team were retrospectively enrolled into this study. The runners completed a DXA scan during the fall season (August-November) and participated in sport activities before the scan. Three months after scanning, electronic medical records were reviewed for the occurrence of BSI. An independent-sample t test was used to compare BMD (total and regional [spine, pelvis, and legs]), BComp (% body fat, fat mass, and lean mass), and anthropometric measurements (shoulder width and leg, arm, and trunk length) between runners with versus without BSI (included subgroup analysis by sex). Multiple linear regression with stepwise removal was used to determine variables most predictive of BMD.

RESULTS

Of the 79 enrolled participants (42 male, 37 female), 18 runners (22.8%; 11 female, 7 male) sustained a lower limb BSI. Compared with the noninjured group, injured runners had lower total and regional BMD (P < .001 for all) and shorter leg and arm lengths (P < .05 for both), whereas injured male runners had lower fat mass and injured female runners had lower lean mass in the legs (P < .05 for both). Injured runners' age-matched total BMD Z score (-0.1 ± 0.6) was considered clinically normal. BComp and anthropometric measures were predictive of total and regional BMD (P < .05; R 2 = 0.64-0.80; percentage error = 3.8%-4.8%).

CONCLUSION

The DXA scans of injured runners prior to incidence indicated lower BMD compared with noninjured runners. Shorter limb lengths, lower fat mass (male), and lower leg lean mass (female) may also be indicative of risk. Certain BComp and anthropometric measures were predictive of BMD.

Trail running injury risk factors: a living systematic review

OBJECTIVE

To review and frequently update the available evidence on injury risk factors and epidemiology of injury in trail running.

DESIGN

Living systematic review. Updated searches will be done every 6 months for a minimum period of 5 years.

DATA SOURCES

Eight electronic databases were searched from inception to 18 March 2021.

ELIGIBILITY CRITERIA

Studies that investigated injury risk factors and/or reported the epidemiology of injury in trail running.

RESULTS

Nineteen eligible studies were included, of which 10 studies investigated injury risk factors among 2 785 participants. Significant intrinsic factors associated with injury are: more running experience, level A runner and higher total propensity to sports accident questionnaire (PAD-22) score. Previous history of cramping and postrace biomarkers of muscle damage is associated with cramping. Younger age and low skin phototypes are associated with sunburn. Significant extrinsic factors associated with injury are neglecting warm-up, no specialised running plan, training on asphalt, double training sessions per day and physical labour occupations. A slower race finishing time is associated with cramping, while more than 3 hours of training per day, shade as the primary mode of sun protection and being single are associated with sunburn. An injury incidence range 0.7-61.2 injuries/1000 hours of running and prevalence range 1.3% to 90% were reported. The lower limb was the most reported region of injury, specifically involving blisters of the foot/toe.

CONCLUSION

Limited studies investigated injury risk factors in trail running. Our review found eight intrinsic and nine extrinsic injury risk factors. This review highlighted areas for future research that may aid in designing injury risk management strategies for safer trail running participation.PROSPERO registration numberCRD42021240832.