Association between stress fracture incidence and predicted body fat in United States Army Basic Combat Training recruits

Incidence and Risk Factors for Bone Stress Injuries in United States Air Force Special Warfare Trainees

OBJECTIVES

To determine (1) the incidence rate of lower extremity (LE) bone stress injuries (BSIs) in United States Air Force Special Warfare (AFSPECWAR) trainees during the first 120 days of training, and (2) factors associated with sustaining a LE BSI.

DESIGN

Retrospective cohort study.

METHODS

AFSPECWAR Airmen (n = 2,290, mean age = 23.7 ± 3.6 years) entering an intensive 8-week preparatory course "SW-Prep" between October 2017 and May 2021. We compared anthropometric measurements, previous musculoskeletal injury (MSKI), fitness measures, and prior high-impact sports participation in those that did and did not suffer a BSI during the 120-day observation period using independent t-tests and chi-square tests. A multivariable binary logistic regression was used to determine factors associated with suffering a BSI.

RESULTS

A total of 124 AFSPECWAR trainees suffered a BSI during the surveillance period, yielding an incidence proportion of 5.41% and an incidence rate of 1.4 BSIs per 100 person-months. The multivariate logistic regression revealed that lower 2-minute sit-up scores, no prior history of participation in a high-impact high-school sport, and a history of prior LE MSKI were associated with suffering a BSI. A receiver operator characteristic curve analysis yielded an area under the curve (AUC) of 0.727.

CONCLUSION

BSI incidence proportion for our sample was similar to those seen in other military settings. Military trainees without a history of high-impact sports participation who achieve lower scores on sit-ups tests and have a history of LE MSKI have a higher risk for developing a LE BSI during the first 120 days of AFSPECWAR training.

Raising the U.S. Army Height-Weight (Body Mass Index) Standards: Quantifying Metabolic Risk

BACKGROUND & OBJECTIVES

The U.S. Army fell 25% short of its recruitment goal in 2022 and therefore, increasing the eligibility pool for potential recruits is of interest. Raising the body mass index (BMI) standards for eligibility presents a path to increase the recruitable population; however, there may be additional costs incurred due to attendant health risks that may be present in individuals with higher BMI.

METHODS

We filtered the 2017-2020 National Health and Nutrition Examination Survey by age (17-25 years) and BMI (up to 30 kg/m2). A k-means cluster analysis was performed on the filtered dataset for the variables used to determine metabolic syndrome. Metabolic syndrome Clusters were characterized through summary statistics and compared over clinical measurements and questionnaire responses.

RESULTS

Five distinct clusters were identified and mean BMI in two clusters (Clusters1 and 3) exceeded the current U.S. Army BMI thresholds. Of these two clusters, Cluster 1 members had metabolic syndrome. Cluster 3 members were at higher risk for metabolic syndrome compared to members of Clusters 2, 4, and 5. Mean waist circumference was slightly lower in Cluster 3 compared to Cluster 1. None of the clusters had significant differences in depression scores, poverty index, or frequency of dental visits.

CONCLUSIONS

Potential recruits from Cluster 1 have excessive health risk and may incur substantial cost to the U.S. Army if enlisted. However, potential recruits from Cluster 3 appear to add little risk and offer an opportunity to increase the pool for recruiting.

Relation of Vitamin D Level, BMI, and Location of Lower Extremity Stress Fractures in Military Trainees

INTRODUCTION

Military trainees are at an increased risk of stress fractures. Vitamin D availability is known to play an important role in both fracture prevention and healing. The purpose of this investigation was to assess 25-hydroxy vitamin D (25(OH)D) levels in soldiers with confirmed lower extremity stress fractures and assess the predictors of fracture location.

MATERIALS AND METHODS

Following Institutional Review Board approval, military trainees at a large training base presenting to the orthopedic clinic with a radiographically verified stress fracture were identified. Demographic data and 25(OH)D levels were collected. A descriptive analysis was performed in regard to patient age, body mass index (BMI), and 25(OH)D level. Interactions between variables were assessed using one-way analysis of variance for four fracture location groups (femoral neck, femoral shaft, tibial shaft, and foot and ankle). Bivariate correlations were examined between age, BMI, and vitamin D level.

RESULTS

A total of 155 lower extremity stress fractures were identified in 144 males and 11 females over 30 months. The mean age was 22.7 ± 4.85 years. The majority (60.7%) of fractures were located in the femoral neck. The average 25(OH)D level was 26.8 ± 8.37 ng/mL. Overall, 26% (N = 41) of enrolled patients had normal 25(OH)D levels, 48% (N = 74) had insufficient 25(OH)D levels, and 26% (N = 40) had deficient 25(OH)D levels. Patients with femoral neck fractures and tibial shaft fractures had significantly lower BMI than patients with foot and ankle fractures (23.3 vs. 27.7, P < .001 and 24.2 vs. 27.7, P = .003, respectively). Patients with foot and ankle fractures had significantly lower 25(OH)D levels than patients with femoral shaft fractures (21.1 vs. 30.1, P = .02). There were no significant findings regarding age and fracture location. Age correlated positively (but weakly) with BMI (0.338, P < .001). There was no correlation between age and vitamin D level or BMI and vitamin D level.

CONCLUSION

Overall, 74% of patients in military training with lower extremity stress fractures had insufficient or deficient levels of 25(OH)D, highlighting a persistent area of concern in this population. Patients with femoral neck and tibial shaft stress fractures had significantly lower BMI than patients with foot and ankle stress fractures. This suggests that in stress fracture-prone patients, BMI may play a role in predicting fracture location.

Military Body Composition Standards and Physical Performance: Historical Perspectives and Future Directions

ABSTRACT

Harty, PS, Friedl, KE, Nindl, BC, Harry, JR, Vellers, HL, and Tinsley, GM. Military body composition standards and physical performance: historical perspectives and future directions. J Strength Cond Res 36(12): 3551-3561, 2022-US military physique and body composition standards have been formally used for more than 100 years. These metrics promote appropriate physical fitness, trim appearance, and long-term health habits in soldiers, although many specific aspects of these standards have evolved as evidence-based changes have emerged. Body composition variables have been shown to be related to many physical performance outcomes including aerobic capacity, muscular endurance, strength and power production, and specialized occupational tasks involving heavy lifting and load carriage. Although all these attributes are relevant, individuals seeking to improve military performance should consider emphasizing strength, hypertrophy, and power production as primary training goals, as these traits appear vital to success in the new Army Combat Fitness Test introduced in 2020. This fundamental change in physical training may require an adjustment in body composition standards and methods of measurement as physique changes in modern male and female soldiers. Current research in the field of digital anthropometry (i.e., 3-D body scanning) has the potential to dramatically improve performance prediction algorithms and potentially could be used to inform training interventions. Similarly, height-adjusted body composition metrics such as fat-free mass index might serve to identify normal weight personnel with inadequate muscle mass, allowing for effective targeted nutritional and training interventions. This review provides an overview of the origin and evolution of current US military body composition standards in relation to military physical readiness, summarizes current evidence relating body composition parameters to aspects of physical performance, and discusses issues relevant to the emerging modern male and female warrior.

Risk factors for injuries in female soldiers: a systematic review

Background

Female soldiers form an integral part of any modern defence force. Previous reports have highlighted that female soldiers report injuries at higher rates than male personnel. One possible reason for this is an actual difference in underlying injury rates, purported to be due to several factors, including levels of fitness. The aim of this review was to determine risk factors for injuries in female soldiers.

Methods

A systematic search was conducted for studies which reported on risk factors for injuries in female soldiers. Databases searched included PUBMED, CINAHL and Medline through OVID. Eligible studies were rated for their methodological quality using the Critical Appraisal Skills Program (CASP) tools and data were extracted and synthesized using a critical narrative approach.

Results

A total of 18 articles were included in this review which reported on 18 risk factors for injury. Smoking, previous injury, no history of deployment, heavy occupational tasks, lower levels of aerobic fitness and lower number of push-up repetitions appear to be risk factors for injuries in female soldiers. Age, height, body fat, high or low BMI and body mass do not appear to be consistent risk factors for injury in female soldiers and there appears to be minimal evidence for current levels of activity, sit-up ability, and other assessments of strength, power, speed, or movement being associated with injury risk. Additionally, neither flexibility nor previous levels of activity appear to be associated with injury risk in female soldiers.

Conclusion

Strategies to improve aerobic fitness and upper limb endurance, reduce smoking, and optimise rehabilitation from injuries and risk management for heavy occupational tasks need to be developed for female soldiers. Such strategies are also likely to reduce risks for male soldiers.

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.

Non-Modifiable Risk Factors for Stress Fractures in Military Personnel Undergoing Training: A Systematic Review

A fracture, being an acquired rupture or break of the bone, is a significant and debilitating injury commonly seen among athletes and military personnel. Stress fractures, which have a repetitive stress aetiology, are highly prevalent among military populations, especially those undergoing training. The primary aim of this review is to identify non-modifiable risk factors for stress fractures in military personnel undergoing training. A systematic search was conducted of three major databases to identify studies that explored risk factors for stress fractures in military trainees. Critical appraisal, data extraction, and a narrative synthesis were conducted. Sixteen articles met the eligibility criteria for the study. Key non-modifiable risk factors identified were prior stress fracture and menstrual dysfunction, while advancing age and race other than black race may be a risk factor. To reduce the incidence of stress fractures in military trainees, mitigating modifiable risk factors among individuals with non-modifiable risk factors (e.g., optimising conditioning for older trainees) or better accommodating non-modifiable factors (for example, extending training periods and reducing intensity to facilitate recovery and adaptation) are suggested, with focus on groups at increased risk identified in this review.

Risk factors for musculoskeletal injuries in the military: a qualitative systematic review of the literature from the past two decades and a new prioritizing injury model

BACKGROUND

Musculoskeletal injuries (MSkIs) are a leading cause of health care utilization, as well as limited duty and disability in the US military and other armed forces. MSkIs affect members of the military during initial training, operational training, and deployment and have a direct negative impact on overall troop readiness. Currently, a systematic overview of all risk factors for MSkIs in the military is not available.

METHODS

A systematic literature search was carried out using the PubMed, Ovid/Medline, and Web of Science databases from January 1, 2000 to September 10, 2019. Additionally, a reference list scan was performed (using the "snowball method"). Thereafter, an international, multidisciplinary expert panel scored the level of evidence per risk factor, and a classification of modifiable/non-modifiable was made.

RESULTS

In total, 176 original papers and 3 meta-analyses were included in the review. A list of 57 reported potential risk factors was formed. For 21 risk factors, the level of evidence was considered moderate or strong. Based on this literature review and an in-depth analysis, the expert panel developed a model to display the most relevant risk factors identified, introducing the idea of the "order of importance" and including concepts that are modifiable/non-modifiable, as well as extrinsic/intrinsic risk factors.

CONCLUSIONS

This is the qualitative systematic review of studies on risk factors for MSkIs in the military that has attempted to be all-inclusive. A total of 57 different potential risk factors were identified, and a new, prioritizing injury model was developed. This model may help us to understand risk factors that can be addressed, and in which order they should be prioritized when planning intervention strategies within military groups.

Sex Differences in the Incidence and Risk of Ankle-Foot Complex Stress Fractures Among U.S. Military Personnel

Background: The objective of this study was to evaluate sex differences in the incidence and risk of ankle-foot complex (AFC) stress fractures among U.S. military personnel, which could assist in developing management strategies as females assume a greater role in U.S. military operations. Materials and Methods: The Defense Medical Epidemiology Database was used to identify all diagnosed AFC stress fractures in military personnel from 2006 to 2015. Cumulative incidence of AFC stress fractures was calculated and compared by year, service branch, and military rank. Sex differences in the risk of AFC stress fractures by occupation were examined, and integrated (i.e., male and female) occupations were compared with nonintegrated (i.e., male only) occupations. Results: A total of 43,990 AFC stress fractures were identified. The overall incidence rate was 2.76 per 1,000 person-years (p-y) for males and 5.78 per 1,000 p-y for females. Females consistently had higher incidence of AFC stress fractures across all subgroups, particularly among enlisted personnel. Female enlisted service members had the highest risk of AFC stress fractures in aviation (relative risk [RR] = 5.74; 95% confidence interval [CI]: 4.80-6.87) and artillery/gunnery (RR = 5.15; 95% CI: 4.62-5.75) occupations. Females in integrated occupations had significantly higher rates of AFC stress fractures than males in both integrated and nonintegrated occupations (i.e., special forces, infantry, and mechanized/armor). Conclusions: Females in the U.S. military have a higher risk of AFC stress fractures than males. As integration of females into previously sex-restricted occupations continues, focused prevention efforts may be needed to reduce injury burden and maximize medical readiness.

Musculoskeletal Injuries Among Females in the Military: A Scoping Review

INTRODUCTION

Musculoskeletal injuries (MSKi) are a common challenge for those in military careers. Compared to their male peers, reports indicate that female military members and recruits are at greater risk of suffering MSKi during training and deployment. The objectives of this study were to identify the types and causes of MSKi among female military personnel and to explore the various risk factors associated with MSKi.

MATERIALS AND METHODS

A scoping review was conducted over a 4-month time frame of English language, peer-reviewed studies published from 1946 to 2019. Search strategies for major biomedical databases (e.g., MEDLINE; Embase Classic + Embase; and the following EBM Reviews-Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects, Health Technology Assessment, and the NHS Economic Evaluation Database) were developed by a senior medical information specialist and included 2,891 titles/abstracts. Study selection and data collection were designed according to the Population, Concept, and Context framework. Studies were included if the study population provided stratified data for females in a military context.

RESULTS

From a total of 2,287 citations captured from the literature searches, 168 peer-reviewed publications (144 unique studies) were eligible for inclusion. Studies were identified from across 10 countries and published between 1977 and 2019. Study designs were primarily prospective and retrospective cohorts. Most studies assessed both prevalence/incidence and risk factors for MSKi (62.50%), with few studies assessing cause (13.69%). For MSKi of female recruits compared to active female members, the prevalence was higher (19.7%-58.3% vs. 5.5%-56.6%), but the incidence (0.02%-57.7% vs. 13.5%-71.9%) was lower. The incidence of stress fractures was found to be much higher in female recruits than in active members (1.6%-23.9% vs. 2.7%). For anthropometric risk factors, increased body fat was a predictor of MSKi, but not stress fractures. For physiological risk factors for both female military groups, being less physically fit, later menarche, and having no/irregular menses were predictors of MSKi and stress fractures. For biomechanical risk factors, among female recruits, longer tibial length and femoral neck diameter increased the risk of stress fractures, and low foot arch increased risk of an ankle sprain. For female active military members, differences in shoulder rotation and bone strength were associated with risk of MSKi. For biological sex, being female compared to male was associated with an increased risk of MSKi, stress fractures, and general injuries. The consequences of experiencing MSKi for active military included limited duties, time off, and discharge. For recruits, these included missed training days, limited duty days, and release.

CONCLUSIONS

This scoping review provides insight into the current state of the evidence regarding the types and causes of MSKi, as well as the factors that influence MSKi among females in the military. Future research endeavors should focus on randomized controlled trials examining training paradigms to see if women are more susceptible. The data presented in the scoping review could potentially be used to develop training strategies to mitigate some of the identified barriers that negatively impact women from pursuing careers in the military.

Experimental study protocol of the project "MOtor function and VItamin D: Toolkit for motor performance and risk Assessment (MOVIDA)"

Musculoskeletal injuries, a public health priority also in the military context, are ascribed to several risk factors, including: increased reaction forces; low/reduced muscle strength, endurance, body mass, Vitamin D level, and bone density; inadequate lifestyles and environment. The MOVIDA Project-funded by the Italian Ministry of Defence-aims at developing a transportable toolkit (assessment instrumentation, assessment protocols and reference/risk thresholds) which integrates motor function assessment with biological, environmental and behavioural factors to help characterizing the risk of stress fracture, stress injury or muscle fatigue due to mechanical overload. The MOVIDA study has been designed following the STROBE guidelines for observational cross-sectional studies addressing healthy adults, both militaries and civilians, with varying levels of physical fitness (sedentary people, recreational athletes, and competitive athletes). The protocol of the study has been designed and validated and is hereby reported. It allows to collect and analyse anamnestic, diagnostic and lifestyle-related data, environmental parameters, and functional parameters measured through portable and wearable instrumentation during adapted 6 minutes walking test. The t-test, one and two-way ANOVA with post-hoc corrections, and ANCOVA tests will be used to investigate relevant differences among the groups with respect to biomechanical parameters; non-parametric statistics will be rather used for non-normal continuous variables and for quantitative discrete variables. Generalized linear models will be used to account for risk and confounding factors.

Overuse-Related Injuries of the Musculoskeletal System: Systematic Review and Quantitative Synthesis of Injuries, Locations, Risk Factors and Assessment Techniques

Overuse-related musculoskeletal injuries mostly affect athletes, especially if involved in preseason conditioning, and military populations; they may also occur, however, when pathological or biological conditions render the musculoskeletal system inadequate to cope with a mechanical load, even if moderate. Within the MOVIDA (Motor function and Vitamin D: toolkit for risk Assessment and prediction) Project, funded by the Italian Ministry of Defence, a systematic review of the literature was conducted to support the development of a transportable toolkit (instrumentation, protocols and reference/risk thresholds) to help characterize the risk of overuse-related musculoskeletal injury. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) approach was used to analyze Review papers indexed in PubMed and published in the period 2010 to 2020. The search focused on stress (overuse) fracture or injuries, and muscle fatigue in the lower limbs in association with functional (biomechanical) or biological biomarkers. A total of 225 Review papers were retrieved: 115 were found eligible for full text analysis and led to another 141 research papers derived from a second-level search. A total of 183 papers were finally chosen for analysis: 74 were classified as introductory to the topics, 109 were analyzed in depth. Qualitative and, wherever possible, quantitative syntheses were carried out with respect to the literature review process and quality, injury epidemiology (type and location of injuries, and investigated populations), risk factors, assessment techniques and assessment protocols.

Effects of foam rolling for delayed onset muscle soreness on loaded military task performance and perceived recovery

Objective

The purpose of this investigation was to evaluate the effects of foam rolling (FR) and passive recovery (PR) on symptoms of delayed-onset muscle soreness (DOMS) and military-specific performance.

Methods

Twenty men and women (age: 23.6 ± 4.1 years, height: 176.4 ± 5.6 cm, and body mass: 84.7 ± 13.4 kg) completed a DOMS-inducing exercise protocol (DIP), followed by FR or PR. Four loaded military tasks (LMT) were performed 24 h later. Rating of perceived exertion (RPE) was measured during DIP and after each LMT. Rating of muscle pain (RMP) was measured prior to the LMTs and after the recovery protocols. A repeated measure analysis of variance and partial eta squared were used to compare LMT performance across baseline, FR and PR sessions. Friedman tests compared perceptual variables across baseline, FR, and PR. Wilcoxon matched-pairs signed-ranks test evaluated RPE during DIP, post-DIP, and post-recovery RMP between FR and PR.

Results

LMT performance times were significantly faster after FR compared to PR (stair climb: p = .038, cover position sprint: p = .011, simulated ammunition can carry: p = .003, Shuttle Run: p = .034). RPE measured during LMTs was similar across all data points. Post-recovery RMP for FR (3.0 (2.3, 4.0)) and PR (4.0 (3.0, 6.0)) were not significantly different.

Conclusion

FR reduced the impact of DOMS on three loaded tactical performance tasks without significant reduction in perceived soreness.

An investigation into the association of bone characteristics and body composition with stress fracture in athletes

BACKGROUND

The aim of the study was to establish the bone and body composition characteristics of high-level athletes with and without a history of stress fracture injury.

METHODS

Overall, 279 high-level athletes (212 men, 67 women) (age 28.0±9.2 years; body mass 75.0±17.4 kg; height 1.78±0.10 m) and 112 non-athletic controls (60 women, 52 men) 36.2±15.0 years; 70.9±12.9 kg; 1.71±0.10 m) were assessed by DXA to establish their bone mineral density and content, body fat and lean mass. Athletes completed a questionnaire detailing their stress fracture history.

RESULTS

There were no differences in whole-body bone mineral density (men 1.41±0.12 g/cm², women 1.19±0.09 g/cm²), bone mineral content (men 3709±626 g, women 2263±290 g), body fat (men 16.3±5.0%,women 23.0±4.6%) and lean mass (men 65.4±9.9 kg, women 38.7±3.6 kg) between athletes with a history of stress fracture (34 men, 16 women) and those without (176 men, 40 women).

CONCLUSIONS

DXA derived bone and body composition characteristics were not independent risk factors for stress fracture injury in high-level athletes. This study in a large cohort of high-level athletes provides normative bone and body composition values that can be used as a benchmark for researchers and applied practitioners.

Simultaneous bilateral posteromedial tibial epiphysis stress fractures in a healthy young man: A case report

We present a compelling case of simultaneous, bilateral tibial stress fractures occurring in a unique epiphyseal and posterior location, with unclear aetiology. An overweight, Caucasian male in his late 20s developed synchronous bilateral medial knee pain following an intense 10-day training regimen. His radiographies were normal, but MRI revealed almost identical bilateral stress fracture lines in the posteromedial tibial epiphyses. Bone mineral densitometry and a full metabolic and hormonal panel were performed to further investigate potential underlying metabolic bone disease. He was found to have normal bone mineral densitometry and low Vitamin D serum values. Symptomatology greatly improved with activity modification. There were no further complaints and complications at 12 months' follow-up. Diagnosis can be challenging and the treating physician should be acquainted with the basic science of stress fractures and main discriminating clinical, biochemical and radiological characteristics from insufficiency fractures, to avoid pitfalls in treatment decision.

A Comparative Analysis of Army Body Composition Standards for Women

The aim of this study was to compare body fat percentage (BF%) of women measured using the U.S. Army standard body composition assessment (ABC) and two common laboratory measures of body composition to evaluate the efficacy of ABC within this population. The BF% of 27 women (21.5 ± 1.8 years) was assessed using the 7-site skinfold, air plethysmography, and ABC measurements. The initial physical fitness test (IPFT) was used to determine if participants met the criteria required for admittance into basic combat training. A repeated measures ANOVA identified differences in BF% between the three assessment methods, (F (2, 52) = 22.83, p < .001, η2 p = .47). Pairwise comparisons revealed that mean BF% obtained using the ABC (29.3 ± 7.7 %) was significantly higher (p = .042) than BF% measured using air plethysmography (26.9 ± 8.4 %). ABC and air plethysmography measured BF% was significantly higher (both p < .001) than BF% obtained from skinfold assessment (22.2 ± 5.9 %). Of the 27 total participants, 4 (14.8%) passed IPFT but failed to meet the Army body composition standards using the ABC method. The primary findings of this study suggest that the overestimation of BF% by the ABC method could lead to an unnecessary delay in enlistment for women approaching the upper threshold of the Army's acceptable body composition standards. Alternative methods of assessing body composition in this population should be explored. However, skinfold assessment does not appear to be a suitable alternative to the ABC.

Diagnosis of Stress fractures in military trainees: a large-scale cohort

INTRODUCTION

The Israel Defense Forces (IDF) has strict protocols for the diagnosis and treatment of stress fractures wherein diagnosis is clinical with imaging used for persistent symptoms only. The purpose of this study was to examine the incidence of clinical and radiological stress fractures during IDF combat training.

METHODS

Medical records of all soldiers enlisted to combat training between 2014 and 2017 were scanned for the diagnosis of stress fractures. We examined the imaging tests ordered (plain radiographs and bone scans) and their results and the time between the clinical diagnosis to imaging tests.

RESULTS

During 4 years, 62 371 soldiers (10.1% women) had started combat training, and 3672 of them (5.9%) were diagnosed with clinical stress fractures. Radiographs were ordered for 53.5% of those diagnosed, of whom 29.7% also had a bone scan. Some 42% of radiographs were taken within 21 days. Radiographs were positive for stress fractures in 11.1% of tests. Bone scans showed evidence of stress fractures in 49.7%, of which 49.2% diagnosed stress fractures in multiple bones.

CONCLUSION

The high percentage of negative radiographs may indicate towards alternative causes for symptoms. Performing the radiograph before or after 21 days did not affect workup results diverting from current belief that later radiographs will be more sensitive. Multiple stress fractures are a common finding, indicating that the increased training load puts the whole musculoskeletal system at increased risk for injury. Research results may necessitate a revision of clinical guidelines for the diagnosis of stress fractures in military trainees.

Trauma Exposure and Functional Movement Characteristics of Male Tactical Athletes

CONTEXT

Tactical athletes commonly experience high levels of physical stress, which may increase their risk of musculoskeletal injury. It is critical to understand psychological predictors of functional movement (FM), which may help prevent musculoskeletal injury in this population.

OBJECTIVE

To determine the associations of combat and trauma exposure with FM characteristics of male tactical athletes. Secondary objectives were to explore confounding influences of age and physical injury history as well as the mediating role of bodily pain.

DESIGN

Cross-sectional study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Eighty-two healthy, male, active-duty US Navy Explosive Ordnance Disposal personnel (age = 34.0 ± 6.7 years).

MAIN OUTCOME MEASURE(S)

Participants completed measures of combat exposure, trauma exposure, physical injury history, and bodily pain. We assessed FM characteristics (ie, Functional Movement Screen [FMS], Y-Balance Test), from which we derived a composite functional status (CFS) measure. Hypotheses were tested using correlational and multiple regression (causal-steps) models.

RESULTS

In unadjusted models, trauma exposure was inversely associated with the FMS (P = .005) and CFS (P = .009) scores. In adjusted models, these relationships were robust to the confounding influences of age and physical injury history. Trauma exposure and bodily pain were substantive, independent predictors of FMS and CFS in causal-steps models (all P values < .05), implying additive rather than mediated effects (R²_adj = 0.18-0.20). Combat exposure did not predict FM characteristics.

CONCLUSIONS

To our knowledge, this is the first evidence of the influence of trauma exposure on the FM characteristics of male tactical athletes, independent of age, physical injury, and bodily pain. This program of research may help to advance the prevention and treatment of musculoskeletal injuries in the tactical environment.

The Association between Increased Body Mass Index and Overuse Injuries in Israel Defense Forces Conscripts

OBJECTIVES

To examine the association between body mass index (BMI) and overuse injuries (OI) among Israel Defense Forces soldiers, in different corps.

METHODS

Conscripts between 2003 and 2012, infantry, armored corps and intelligence corps (controls) were studied. OI data were taken from computerized patient records. The BMI was classified as underweight, low-normal (18.5-21.9), high-normal (22-24.9), overweight and obese. Multivariate analysis was performed using logistic regression.

RESULTS

There were 73,640 soldiers: 42,506 infantry, 20,781 armor and 10,353 intelligence. OI rates were 52.2, 51.6 and 27%, respectively. OI rate was directly proportional to BMI in all groups (relative risk compared to low-normal, underweight: 0.97, high-normal: 1.05, overweight: 1.11, obese: 1.19, p < 0.05 for all), increased height and younger age. By logistic regression, OI were significantly associated with training group, higher BMI, increased height, younger age, lower education, lower socioeconomic status and lower psychotechnical grading. Throughout the BMI range, each additional unit of BMI was associated with a 2% OI increase.

CONCLUSIONS

Higher BMI was associated with a higher rate of OI in all groups. Therefore there is no point in differentially assigning recruits based on BMI.

Relationship between individual payload weight and spondylolysis incidence in Turkish land forces

OBJECTIVEThe aim of this study was to investigate the relationship between lumbar spondylolysis and payload weight between different combat units of Turkish land forces (TLF).METHODThe authors reviewed clinical and radiological data of the military personnel with low-back pain (LBP) admitted to their clinic between July 2017 and July 2018. Age, BMI, average payload weight, and military service unit were recorded. CT scans were evaluated for pars interarticularis fractures and spondylolisthesis, whereas MRI studies were evaluated for spondylolisthesis, Modic-type endplate changes, or signal loss on T2-weighted images compatible with disc degeneration.RESULTFollowing exclusion, a total of 642 all-male military personnel were included. Of these personnel, 122 were commandos, 435 were infantry, and 85 were serving in the artillery units. Bilateral pars interarticularis fracture was noted in 42 commandos (34.42%) and 2 infantrymen (0.45%). There was no spondylolysis in the artillery units. There was no multiple-level spondylolysis and the most common level of spondylolysis was L5. Commandos had a significantly higher incidence of spondylolysis and more average payload weight (p < 0.001). Twelve patients (27.2%) with spondylolysis had accompanying MRI pathologies at the same level, whereas 32 patients (72.7%) had no accompanying MRI pathologies.CONCLUSIONSIncreased payload weight in military personnel is associated with spondylolysis, and commandos in the TLF have significantly heavier payloads, which causes an increased rate of spondylolysis compared to other units. Additionally, spondylolysis without adjacent-level changes on MRI could be undiagnosed. LBP in active military personnel who have a history of carrying heavy payloads should be evaluated extensively with both MRI and CT scans.

Nonsteroidal Anti-Inflammatory Drug Prescriptions Are Associated With Increased Stress Fracture Diagnosis in the US Army Population

Stress fractures are common in military personnel and endurance athletes, and nonsteroidal anti-inflammatory drug (NSAID) use is widespread in these populations. NSAIDs inhibit prostaglandin synthesis, which blunts the anabolic response of bone to physical activity and could therefore increase risk of stress fracture. The objective of this study was to determine whether prescribed NSAIDs were associated with stress fracture diagnoses among US Army soldiers. We also aimed to establish whether acetaminophen, an analgesic alternative to NSAIDs, was associated with stress fracture risk. A nested case-control study was conducted using data from the Total Army Injury and Health Outcomes Database from 2002 to 2011 (n = 1,260,168). We identified soldiers with a diagnosis of stress fracture (n = 24,146) and selected 4 controls per case matched on length of military service (n = 96,584). We identified NSAID and acetaminophen prescriptions 180 to 30 days before injury (or match date). We also identified soldiers who participated in basic combat training (BCT), a 10-week period of heightened physical activity at the onset of Army service. Among these individuals, we identified 9088 cases and 36,878 matched controls. Conditional logistic regression was used to calculate incident rate ratios (RR) for stress fracture with adjustment for sex. NSAID prescription was associated with a 2.9-fold increase (RR = 2.9, 95% confidence interval [CI] 2.8-2.9) and acetaminophen prescription with a 2.1-fold increase (RR = 2.1, 95% CI 2.0-2.2) in stress fracture risk within the total Army population. The risk was more than 5-fold greater in soldiers prescribed NSAIDs (RR = 5.3, 95% CI 4.9-5.7) and more than 4-fold greater in soldiers prescribed acetaminophen (RR = 4.4, 95% CI 3.9-4.9) during BCT. Our results reveal an association between NSAID and acetaminophen prescriptions and stress fracture risk, particularly during periods of heightened physical activity. Prospective observational studies and randomized controlled trials are needed to support these findings before clinical recommendations can be made. © 2018 American Society for Bone and Mineral Research.