Prunes preserve cortical density and estimated strength of the tibia in a 12-month randomized controlled trial in postmenopausal women: The Prune Study.

Non-pharmacological therapies, such as whole-food interventions, are gaining interest as potential approaches to prevent and/or treat low bone mineral density (BMD) in postmenopausal women. Previously, prune consumption preserved two-dimensional BMD at the total hip. Here we demonstrate that prune consumption preserved three-dimensional BMD and estimated strength at the tibia. PURPOSE: Dietary consumption of prunes has favorable impacts on areal bone mineral density (aBMD); however, more research is necessary to understand the influence on volumetric BMD (vBMD), bone geometry, and estimated bone strength. METHODS: This investigation was a single center, parallel arm 12-month randomized controlled trial (RCT; NCT02822378) to evaluate the effects of 50 g and 100 g of prunes vs. a Control group on vBMD, bone geometry, and estimated strength of the radius and tibia via peripheral quantitative computed tomography (pQCT) in postmenopausal women. Women (age 62.1 ± 5.0yrs) were randomized into Control (n = 78), 50 g Prune (n = 79), or 100 g Prune (n = 78) groups. General linear mixed effects (LME) modeling was used to assess changes over time and percent change from baseline was compared between groups. RESULTS: The most notable effects were observed at the 14% diaphyseal tibia in the Pooled (50 g + 100 g) Prune group, in which group × time interactions were observed for cortical vBMD (p = 0.012) and estimated bone strength (SSI; p = 0.024); all of which decreased in the Control vs. no change in the Pooled Prune group from baseline to 12 months/post. CONCLUSION: Prune consumption for 12 months preserved cortical bone structure and estimated bone strength at the weight-bearing tibia in postmenopausal women.

Effects of Prune (Dried Plum) Supplementation on Cardiometabolic Health in Postmenopausal Women: An Ancillary Analysis of a 12-Month Randomized Controlled Trial, The Prune Study.

BACKGROUND: Estrogen withdrawal during menopause is associated with an unfavorable cardiometabolic profile. Prunes (dried plums) represent an emerging functional food and have been previously demonstrated to improve bone health. However, our understanding of the effects of daily prune intake on cardiometabolic risk factors in postmenopausal women is limited. OBJECTIVES: We conducted an ancillary investigation of a randomized controlled trial (RCT), The Prune Study, to evaluate the effect of 12-mo prune supplementation on cardiometabolic health markers in postmenopausal women. METHODS: The Prune Study was a single-center, parallel-design, 12-mo RCT in which postmenopausal women were allocated to no-prune control, 50 g/d prune, or 100 g/d prune groups. Blood was collected at baseline, 6 mo, and 12 mo/post to measure markers of glycemic control and blood lipids. Body composition was assessed at baseline, 6 mo, and 12 mo/post using dual-energy X-ray absorptiometry. Linear mixed-effects models were used to evaluate the effect of time, treatment, and their interaction on cardiometabolic health markers, all quantified as exploratory outcomes. RESULTS: A total of 183 postmenopausal women (mean age, 62.1 ± 4.9 y) completed the entire 12-mo RCT: control (n = 70), 50 g/d prune (n = 67), and 100 g/d prune (n = 46). Prune supplementation at 50 g/d or 100 g/d did not alter markers of glycemic control and blood lipids after 12 mo compared with the control group (all P > 0.05). Furthermore, gynoid percent fat and visceral adipose tissue (VAT) indices did not significantly differ in women consuming 50 g/d or 100 g/d prunes compared with the control group after 12 mo of intervention. However, android total mass increased by 3.19% ± 5.5% from baseline in the control group, whereas the 100 g/d prune group experienced 0.02% ± 5.6% decrease in android total mass from baseline (P < 0.01). CONCLUSIONS: Prune supplementation at 50 g/d or 100 g/d for 12 mo does not improve glycemic control and may prevent adverse changes in central adiposity in postmenopausal women. This trial was registered at clinicaltrials.gov as NCT02822378.

Hormonal contraception and medical readiness for female service members.

Many female military service members choose to use hormonal contraception to prevent pregnancy and/or to control or suppress menses. Hormonal contraception, which comes in many different forms based on dose, estrogen/progestin type, and route of administration (oral, vaginal, transdermal, implant, intrauterine device, injectable), may cause side effects, some of which can influence military medical readiness, or the health status necessary to perform assigned missions. This expert review summarizes the evidence around common military-relevant side effects of hormonal contraception that could impact readiness, including effects on weight and body composition, bone health, psychological health, and physical performance, and serves as a tool for uniformed and civilian clinicians counseling female service members about hormonal contraception. Current evidence suggests some hormonal contraception can lead to weight and fat gain, may modulate susceptibility to mood or mental health disorders, and could impact bone mineral density and stress fracture risk; more research is needed on physical performance effects. Clinicians must be familiar with readiness considerations of each type of hormonal contraception to provide comprehensive patient education and allow for optimal shared decision-making about hormonal contraception use among female Service members. Considering the relative lack of data on the effects of nonoral hormonal contraception routes on readiness outcomes and the growing interest in long-acting reversible contraceptives among female service members, future research should continue to investigate effects of all hormonal contraception methods available to service members.

Micronutrient Status During Military Training and Associations With Musculoskeletal Health, Injury, and Readiness Outcomes.

OBJECTIVE: Micronutrient status, specifically vitamin D and iron, represent modifiable factors for optimizing military readiness. The primary purpose of this investigation was to determine associations between micronutrient deficiency (i.e., iron status and 25-hydroxy-vitamin D [25(OH)D]) and operationally relevant outcomes (i.e., skeletal health, musculoskeletal injury) at baseline and post-10 weeks of arduous military training. METHODS: A total of 227 (177 men, 50 women) Marine Officer Candidates School (OCS) candidates who completed OCS training with complete data sets were included in this analysis. Vitamin D and iron status indicators were collected at two timepoints, pre (baseline) and post OCS. Musculoskeletal outcomes at the mid- and proximal tibial diaphysis were assessed via peripheral quantitative computed tomography. RESULTS: Micronutrient status declined following OCS training in men and women and was associated with musculoskeletal outcomes including greater bone strength (strength strain index) at the mid-diaphysis site in those with optimal status (M = 38.26 mm3, SE = 15.59) versus those without (M = -8.03 mm3, SE = 17.27). In women (p = .037), endosteal circumference was greater in the deficient group (M = 53.26 mm, SE = 1.19) compared with the optimal group (M = 49.47 mm, SE = 1.31) at the proximal diaphysis. In men, greater baseline hepcidin concentrations were associated with an increased likelihood of suffering musculoskeletal injury during training. CONCLUSIONS: Vitamin D and iron status declined over the course of training, suggesting impaired micronutrient status. Differences in musculoskeletal outcomes by micronutrient group suggests optimal vitamin D and ferritin concentrations may exert beneficial effects on bone fatigability and fracture reduction during military training.

Randomised controlled trial of the effects of increased energy intake on menstrual recovery in exercising women with menstrual disturbances: the 'REFUEL' study.

STUDY QUESTION: Does increased daily energy intake lead to menstrual recovery in exercising women with oligomenorrhoea (Oligo) or amenorrhoea (Amen)? SUMMARY ANSWER: A modest increase in daily energy intake (330 ± 65 kcal/day; 18 ± 4%) is sufficient to induce menstrual recovery in exercising women with Oligo/Amen. WHAT IS KNOWN ALREADY: Optimal energy availability is critical for normal reproductive function, but the magnitude of increased energy intake necessary for menstrual recovery in exercising women, along with the associated metabolic changes, is not known. STUDY DESIGN, SIZE, DURATION: The REFUEL study (trial # NCT00392873) is the first randomised controlled trial to assess the effectiveness of 12 months of increased energy intake on menstrual function in 76 exercising women with menstrual disturbances. Participants were randomised (block method) to increase energy intake 20-40% above baseline energy needs (Oligo/Amen + Cal, n = 40) or maintain energy intake (Oligo/Amen Control, n = 36). The study was performed from 2006 to 2014. PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants were Amen and Oligo exercising women (age = 21.0 ± 0.3 years, BMI = 20.8 ± 0.2 kg/m2, body fat = 24.7 ± 0.6%) recruited from two universities. Detailed assessment of menstrual function was performed using logs and measures of daily urinary ovarian steroids. Body composition and metabolic outcomes were assessed every 3 months. MAIN RESULTS AND THE ROLE OF CHANCE: Using an intent-to-treat analysis, the Oligo/Amen + Cal group was more likely to experience menses during the intervention than the Oligo/Amen Control group (P = 0.002; hazard ratio [CI] = 1.91 [1.27, 2.89]). In the intent-to-treat analysis, the Oligo/Amen + Cal group demonstrated a greater increase in energy intake, body weight, percent body fat and total triiodothyronine (TT3) compared to the Oligo/Amen Control group (P < 0.05). In a subgroup analysis where n = 22 participants were excluded (ambiguous baseline menstrual cycle, insufficient time in intervention for menstrual recovery classification), 64% of the Oligo/Amen + Cal group exhibited improved menstrual function compared with 19% in the Oligo/Amen Control group (χ2, P = 0.001). LIMITATIONS, REASONS FOR CAUTION: While we had a greater than expected dropout rate for the 12-month intervention, it was comparable to other shorter interventions of 3-6 months in duration. Menstrual recovery defined herein does not account for quality of recovery. WIDER IMPLICATIONS OF THE FINDINGS: Expanding upon findings in shorter, non-randomised studies, a modest increase in daily energy intake (330 ± 65 kcal/day; 18 ± 4%) is sufficient to induce menstrual recovery in exercising women with Oligo/Amen. Improved metabolism, as demonstrated by a modest increase in body weight (4.9%), percent body fat (13%) and TT3 (16%), was associated with menstrual recovery. STUDY FUNDING/COMPETING INTEREST(S): This research was supported by the U.S. Department of Defense: U.S. Army Medical Research and Material Command (Grant PR054531). Additional research assistance provided by the Penn State Clinical Research Center was supported by the National Center for Advancing Translation Sciences, National Institutes of Health, through Grant UL1 TR002014. M.P.O. was supported in part by the Loretta Anne Rogers Chair in Eating Disorders at University of Toronto and University Health Network. All authors report no conflict of interest. TRIAL REGISTRATION NUMBER: NCT00392873. TRIAL REGISTRATION DATE: October 2006. DATE OF FIRST PATIENT'S ENROLMENT: September 2006.

The Male Athlete Triad-A Consensus Statement From the Female and Male Athlete Triad Coalition Part 1: Definition and Scientific Basis.

ABSTRACT: The Male Athlete Triad is a syndrome of 3 interrelated conditions most common in adolescent and young adult male endurance and weight-class athletes and includes the clinically relevant outcomes of (1) energy deficiency/low energy availability (EA) with or without disordered eating/eating disorders, (2) functional hypothalamic hypogonadism, and (3) osteoporosis or low bone mineral density with or without bone stress injury (BSI). The causal role of low EA in the modulation of reproductive function and skeletal health in the male athlete reinforces the notion that skeletal health and reproductive outcomes are the primary clinical concerns. At present, the specific intermediate subclinical outcomes are less clearly defined in male athletes than those in female athletes and are represented as subtle alterations in the hypothalamic-pituitary-gonadal axis and increased risk for BSI. The degree of energy deficiency/low EA associated with such alterations remains unclear. However, available data suggest a more severe energy deficiency/low EA state is needed to affect reproductive and skeletal health in the Male Athlete Triad than in the Female Athlete Triad. Additional research is needed to further clarify and quantify this association. The Female and Male Athlete Triad Coalition Consensus Statements include evidence statements developed after a roundtable of experts held in conjunction with the American College of Sports Medicine 64th Annual Meeting in Denver, Colorado, in 2017 and are in 2 parts-Part I: Definition and Scientific Basis and Part 2: The Male Athlete Triad: Diagnosis, Treatment, and Return-to-Play. In this first article, we discuss the scientific evidence to support the Male Athlete Triad model.

The Male Athlete Triad-A Consensus Statement From the Female and Male Athlete Triad Coalition Part II: Diagnosis, Treatment, and Return-To-Play.

ABSTRACT: The Male Athlete Triad is a medical syndrome most common in adolescent and young adult male athletes in sports that emphasize a lean physique, especially endurance and weight-class athletes. The 3 interrelated conditions of the Male Athlete Triad occur on spectrums of energy deficiency/low energy availability (EA), suppression of the hypothalamic-pituitary-gonadal axis, and impaired bone health, ranging from optimal health to clinically relevant outcomes of energy deficiency/low EA with or without disordered eating or eating disorder, functional hypogonadotropic hypogonadism, and osteoporosis or low bone mineral density with or without bone stress injury (BSI). Because of the importance of bone mass acquisition and health concerns in adolescence, screening is recommended during this time period in the at-risk male athlete. Diagnosis of the Male Athlete Triad is best accomplished by a multidisciplinary medical team. Clearance and return-to-play guidelines are recommended to optimize prevention and treatment. Evidence-based risk assessment protocols for the male athlete at risk for the Male Athlete Triad have been shown to be predictive for BSI and impaired bone health and should be encouraged. Improving energetic status through optimal fueling is the mainstay of treatment. A Roundtable on the Male Athlete Triad was convened by the Female and Male Athlete Triad Coalition in conjunction with the 64th Annual Meeting of the American College of Sports Medicine in Denver, Colorado, in May of 2017. In this second article, the latest clinical research to support current models of screening, diagnosis, and management for at-risk male athlete is reviewed with evidence-based recommendations.

Characterizing the resting metabolic rate ratio in ovulatory exercising women over 12 months.

PURPOSE: A reduced resting metabolic rate (RMR) ratio and suppressed total triiodothyronine (TT3 ) have been demonstrated to reflect metabolic compensation to chronic energy deficiency. However, it is unknown whether the relationship between RMR ratio and TT3 remains constant over time. OBJECTIVE: To examine the relationship between RMR ratio and TT3 in free-living exercising, ovulatory, weight-stable women (n = 14) for a 12-month observational period. METHODS: Dual-energy X-ray absorptiometry (DXA) and indirect calorimetry provided data on anthropometrics and energy expenditure. Harris-Benedict, DXA, and Cunningham (1980 and 1991) equations estimated RMR and RMR ratio (measured RMR/predicted RMR). Repeated measures analysis assessed changes over time (ANOVA and Friedman). Generalized linear modeling tested whether RMR ratio threshold predicted TT3  > 73.2 ng/dL or TT3  > 80 ng/dL over 12-months. RESULTS: Women were 25.9 ± 5.4 years, weighed 59.6 ± 5.2 kg with BMI 22.3 ± 1.4 kg/m2 at baseline, which remained constant throughout the study (weight: P = .523; BMI: P = .511). There was no significant effect of time for RMR (P = .886), TT3 (P = .890), energy availability (P = .212), and RMR ratio (Harris-Benedict: P = .852; DXA: P = .607; Cunningham1980 : P = .754; Cunningham1991 : P = .739). When TT3  > 73.2 ng/dL, each RMR ratio threshold (Harris-Benedict: P = .021; DXA: P = .019; Cunningham1980 : P = .019; Cunningham1991 : P = .016) significantly predicted participants as energy replete; however, when using a more lenient clinical TT3 threshold of >80 ng/dL, only the DXA ratio threshold yielded a significant prediction of TT3 (P < .001). CONCLUSIONS: The relationship between RMR ratio and TT3 remains significant and consistent over time in free-living exercising women, validating the use of RMR ratio for the longitudinal characterization of energetic status in this population (ie, prospective serial monitoring).

Indices of Resting Metabolic Rate Accurately Reflect Energy Deficiency in Exercising Women.

Energy deficiency in exercising women can lead to physiological consequences. No gold standard exists to accurately estimate energy deficiency, but measured-to-predicted resting metabolic rate (RMR) ratio has been used to categorize women as energy deficient. The purpose of the study was to (a) evaluate the accuracy of RMR prediction methods, (b) determine the relationships with physiological consequences of energy deficiency, and (c) evaluate ratio thresholds in a cross-sectional comparison of ovulatory, amenorrheic, or subclinical menstrual disturbances in exercising women (n = 217). Dual-energy X-ray absorptiometry (DXA) and indirect calorimetry provided data on anthropometrics and energy expenditure. Harris-Benedict, DXA, and Cunningham (1980 and 1991) equations were used to estimate RMR and RMR ratio. Group differences were assessed (analysis of variance and Kruskal-Wallis tests); logistic regression and Spearman correlations related ratios with consequences of energy deficiency (i.e., low total triiodothyronine; TT3). Sensitivity and specificity calculations evaluated ratio thresholds. Amenorrheic women had lower RMR (p < .05), DXA ratio (p < .01), Cunningham1980 (p < .05) and Cunningham1991 (p < .05) ratio, and TT3 (p < .01) compared with the ovulatory group. Each prediction equation overestimated measured RMR (p < .001), but predicted (p < .001) and positively correlated with TT3 (r = .329-.453). A 0.90 ratio threshold yielded highest sensitivity for Cunningham1980 (0.90) and Harris-Benedict (0.87) methods, but a higher ratio threshold was best for DXA (0.94) and Cunningham1991 (0.92) methods to yield a sensitivity of 0.80. In conclusion, each ratio predicted and correlated with TT3, supporting the use of RMR ratio as an alternative assessment of energetic status in exercising women. However, a 0.90 ratio cutoff is not universal across RMR estimation methods.

Female Athlete Triad and Relative Energy Deficiency in Sport: A Focus on Scientific Rigor.

We examine the scientific evidence supporting The Female Athlete Triad and Relative Energy Deficiency in Sport (RED-S) syndromes. More research is necessary to advance the understanding of both syndromes; however, it is premature to consider RED-S as an evidence-based syndrome. Future research should specifically define RED-S components, determine its clinical relevance, and establish the causality of relative energy deficiency on RED-S outcomes.

Comparison of Female Athlete Triad Coalition and RED-S risk assessment tools.

The Female Athlete Triad Coalition (Triad Coalition) and Relative Energy Deficiency in Sport (RED-S) consensus statements each include risk assessment tools to guide athlete eligibility decisions. This study examined how these tools categorized the same set of individuals to an overall risk factor score and qualitatively compared athlete eligibility decisions resulting from each tool. Exercising women (n = 166) with complete screening/baseline datasets from multiple previously conducted studies were assessed. Data used for risk assessment included: anthropometric measurements, dual-energy x-ray absorptiometry scans, exercise and health status surveys, and two disordered eating questionnaires (Three Factor Eating Questionnaire and Eating Disorder Inventory). Individuals were scored on each tool and subsequently categorized as either fully cleared, provisionally cleared, or restricted from play. Based on the Triad Coalition tool, 25.3% of subjects were classified as fully cleared, 62.0% as provisionally cleared, and 12.7% as restricted from play. Based on the RED-S tool, 71.7% of subjects were classified as fully cleared, 18.7% as provisionally cleared, and 9.6% as restricted from play. The Triad Coalition and RED-S tools resulted in different clearance decisions (p < 0.001), with the Triad Coalition tool recommending increased surveillance of a greater number of athletes.

Linking the Gut Microbiota to Bone Health in Anorexia Nervosa.

PURPOSE OF REVIEW: The purpose of this review is to examine the anorexia nervosa-microbiota-bone relationship, offering a compilation of the relevant human and animal studies that may contribute to a more comprehensive understanding of potential mechanisms involved. RECENT FINDINGS: Recent studies have implicated fermentation by-products of the gut microbiota in bone metabolism. Compromised bone health often accompanies anorexia nervosa due to energy deficiency and hypoestrogenism. The gut microbiome has been implicated as a link between these conditions and impaired bone growth phenotypes. Current research supports decrements in Firmicutes and short-chain fatty acids with increases in Methanobrevibacter smithii and Proteobacteria in anorexia nervosa. A potential mechanism for microbiome-regulated bone growth is through modulation of insulin-like growth factor-1. Future research should aim to examine short-chain fatty acids, probiotics, and prebiotics as alternative therapies to treat low bone density in anorexia nervosa.

Current Status of the Female Athlete Triad: Update and Future Directions.

PURPOSE OF REVIEW: This review provides an update on the primary clinical sequelae of the Female Athlete Triad. RECENT FINDINGS: Scientific advancements have contributed to improve understanding of Triad-related conditions, including leptin's role as a potential neuroendocrine link between energy status and reproductive function. Use of finite element analysis of HRpQCT imaging has provided a more accurate assessment of bone geometry and bone strength and may be clinically relevant. New perspectives aimed at developing and implementing a multi-disciplinary, personalized approach in the prevention and early treatment of triad-related symptoms are provided. The Female Athlete Triad is a multi-dimensional condition that affects active women across the lifespan. Energy availability impacts reproductive function and bone with implications for health and performance. Understanding the contributions of each individual component as well as their interconnected effects is necessary for progression and expansion of the Triad literature.

Inflammatory and Oxidant Responses to Arduous Military Training: Associations with Stress, Sleep, and Performance.

BACKGROUND: Arduous military training frequently consists of prolonged physical activity, sleep disturbance, and stress that increases musculoskeletal injury risk and performance decrements. Inflammatory and oxidative stress responses have been reported in response to arduous training, but with inconsistencies across markers and with under-representation of women. The purpose of the current report was to measure circulating inflammation and oxidative stress responses to military training and to correlate biomarkers with subjective measures of stress and sleep quality as well as military fitness test performance. METHODS: Candidates undergoing the 10-week Marine Corps Officer Candidate School (OCS; 101 men; 62 women) were monitored, with demographic and questionnaire data collected, and blood drawn before and after OCS. Blood was analyzed for six markers of inflammation and three markers of oxidative stress. Associations between biomarkers and questionnaire and fitness test performance were tested. RESULTS: All measured inflammatory markers as well as plasma antioxidant capacity were elevated following OCS. The inflammatory increase was higher in women for several markers. Sleep disturbance and stress perception were associated with IL-6, IL-10 and CRP concentrations, suggesting that low sleep disturbance and stress perception were associated with low inflammatory load. Additionally, those with the highest inflammation at each time point performed worse on fitness tests than those with low inflammation. CONCLUSIONS: Following arduous military training, the circulating environment in a significant portion of officer candidates resembled chronic low-grade inflammation. This circulating inflammatory environment appeared worse with poor sleep, high stress perception, and poor fitness test performance, with utility observed for CRP, IL-6, and IL-10 as biomarkers of these responses. Since inflammation may contribute to musculoskeletal injury and performance decrements, minimizing chronic inflammation during military training should be explored.

Effect of acute resistance exercise on bone turnover in young adults before and after concurrent resistance and interval training.

Weight-bearing physical activity can stimulate bone adaptation. This investigation explored the effect of an acute bout of resistance exercise before and after resistance+interval training on circulating biomarkers of bone metabolism and muscle-bone crosstalk. Healthy young male and female participants (n = 21 male, 28 ± 4 years; n = 17 female, 27 ± 5 years) performed a 6 × 10 squat test (75% 1RM) before and after a 12-week resistance+interval training program. Before and after completion of the training program, blood samples were collected at rest, immediately postexercise, and 2 h postexercise. Blood samples were analyzed for ßCTX, P1NP, sclerostin, osteocalcin, IGF-1, and irisin. Significant effects of acute exercise (main effect of time) were observed as increases in concentrations of IGF-1, irisin, osteocalcin, and P1NP from rest to postexercise. A sex*time interaction indicated a greater decline in ßCTX concentration from rest to 2 h postexercise and a greater increase in sclerostin concentration from rest to immediately postexercise in male compared with female participants. Sex differences (main effect of sex) were also observed for irisin and P1NP concentrations. In summary, changes in concentrations of biochemical markers of bone metabolism and muscle-bone crosstalk were observed in males and females after an acute bout of resistance exercise and following 12 weeks of resistance+interval training.

Skeletal muscle adaptations to high-intensity, low-volume concurrent resistance and interval training in recreationally active men and women.

This study compared the structural and cellular skeletal muscle factors underpinning adaptations in maximal strength, power, aerobic capacity, and lean body mass to a 12-week concurrent resistance and interval training program in men and women. Recreationally active women and men completed three training sessions per week consisting of high-intensity, low-volume resistance training followed by interval training performed using a variety upper and lower body exercises representative of military occupational tasks. Pre- and post-training vastus lateralis muscle biopsies were analyzed for changes in muscle fiber type, cross-sectional area, capillarization, and mitochondrial biogenesis marker content. Changes in maximal strength, aerobic capacity, and lean body mass (LBM) were also assessed. Training elicited hypertrophy of type I (12.9%; p = 0.016) and type IIa (12.7%; p = 0.007) muscle fibers in men only. In both sexes, training decreased type IIx fiber expression (1.9%; p = 0.046) and increased total PGC-1α (29.7%, p < 0.001) and citrate synthase (11.0%; p < 0.014) content, but had no effect on COX IV content or muscle capillarization. In both sexes, training increased maximal strength and LBM but not aerobic capacity. The concurrent training program was effective at increasing strength and LBM but not at improving aerobic capacity or skeletal muscle adaptations underpinning aerobic performance.

Allostatic Load Is Associated with Overuse Musculoskeletal Injury during US Marine Corps Officer Candidates School.

INTRODUCTION: Overuse musculoskeletal injuries (MSKIs) remain a significant medical challenge in military personnel undergoing military training courses; a further understanding of the biological process leading to overuse MSKI development and biological signatures for injury risk are warranted. The purpose of this study was to determine the association between overuse MSKI occurrence and physiological characteristics of allostatic load (AL) characterized as maladaptive biological responses to chronic stress measured by wearable devices in US Marine Corps officer candidates during a 10-week training course. METHODS: Devices recorded energy expenditure (EE), daytime heart rate (HR), sleeping HR, and sleep architecture (time and percent of deep, light, REM sleep, awake time, total sleep). Flux was calculated as the raw or absolute difference in the average value for that day or night and the day or night beforehand. Linear mixed-effect model analysis accounting for cardiorespiratory fitness assessed the association between overuse MSKI occurrence and device metrics (α = 0.05). RESULTS: Sixty-nine participants (23 females) were included. Twenty-one participants (eight females) sustained an overuse MSKI. Overuse MSKI occurrence in male participants was positively associated with daytime HR (ß = 5.316, p = 0.008), sleeping HR (ß = 2.708, p = 0.032), relative EE (ß = 8.968, p = 0.001), absolute flux in relative EE (ß = 2.994, p = 0.002), absolute EE (ß = 626.830, p = 0.001), and absolute flux in absolute EE (ß = 204.062, p = 0.004). Overuse MSKI occurrence in female participants was positively associated with relative EE (ß = 5.955, p = 0.026), deep sleep time (ß = 0.664, p < 0.001), %deep sleep (ß = 12.564, p < 0.001) and negatively associated with absolute flux in sleeping HR (ß = -0.660, p = 0.009). CONCLUSIONS: Overuse MSKI occurrences were associated with physiological characteristics of AL including chronically elevated HR and EE and greater time in restorative sleep stages, which may serve as biological signatures for overuse MSKI risk.