Saliva metabolomics can detect change over time in the metabolic response to physical stress including sustained military training. Whether saliva metabolomics can provide insight into the effects of acute stress, such as a brief hand-to-hand combat match, on metabolic function is not known. This study characterizes changes in saliva metabolome at rest, before, and immediately following a brief, but high-stress hand-to-hand combat event, among West Point Cadets. Cadets (N = 60, 21 ± 1 yr, 77 ± 14 kg, 16 females) provided saliva samples at the beginning of a hand-to-hand combat course under rested conditions (baseline), and after 3 mo of training immediately before (prefight) and after (postfight) the final, 3-min match of the course. Salivary samples were analyzed with global metabolomics profiling. MetaboAnalyst 6.0 was used to detect changes in metabolites between time points. Of the 406 analyzable metabolites detected, none significantly differed between baseline and prefight. At postfight, 81 metabolites increased and 2 decreased by greater than or equal to twofold compared with prefight. Changes in metabolites were primarily related to carbohydrate (19%), lipid (27%), and amino acid (34%) metabolism, specifically glutamate and histidine metabolism, suggesting a rapid increase in energy availability. Saliva metabolomics successfully identified significant changes in metabolism in response to a brief hand-to-hand combat match, demonstrating rapid increases in energy availability in response to an acute physical stress event.NEW & NOTEWORTHY Using salivary metabolomics, the present study captured rapid physiological changes in amino acid and lipid metabolites following a ≤3-min hand-to-hand combat event in military Cadets. Saliva metabolomics is a rapid, noninvasive method to capture metabolomic changes in brief athletic events and provides insight into substrate utilization of individuals in response to brief, acute physical stress.

Background:The Military Health and Nutrition Examination Study (MHANES) is modeled after the National Health and Nutrition Examination Survey (NHANES). NHANES does not enroll active-duty Service Members, who are exposed to unique and adverse occupational challenges compared with civilians. Therefore, NHANES data are not generalizable to Service Members. Objectives:The objective of MHANES is to fill this gap by assessing dietary intake, cardiometabolic health, body composition, biomarkers of nutritional status and health, mental well-being, injury prevalence, genetics, gut microbiome composition, and physical performance in a representative sample of Army Soldiers. Methods:MHANES recruited Soldiers (n = 648) from Army installations across the United States. Participants attended an in-person visit to complete a 24-h dietary recall and questionnaires regarding demographics, physical and mental health, physical activity and performance, and dietary supplement and medication use. Height, weight, blood pressure, resting heart rate variability, physical activity, sleep, resting metabolic rate, hemoglobin mass, and blood volume were measured. Body composition was assessed using bioelectrical impedance, 3-dimensional body imaging, dual-energy X-ray absorptiometry, and circumference measurements. Blood and urine samples were collected to measure biomarkers of nutritional status, health, and genetics. Stool samples were collected to assess microbial diversity and composition. A second 24-h dietary recall was administered 3 to 10 d after the in-person visit. Conclusions:Data collected will be used to determine disease risk and prevalence and to investigate relationships between dietary intake, nutritional status, and markers of health and disease in Army Soldiers. Findings will guide evidence-based screening, education, intervention strategies, and policy decisions to improve Army health. Although the current study is focused exclusively on United States Army Soldiers, a long-term goal is to expand this research to other service branches and include additional sampling cycles similar to NHANES.This trial was registered at clinicaltrials.gov as NCT06380322.

ABSTRACT There are limited opportunities to study physiological and psychological factors that predict success in real world high stress environments where individuals must engage in controlled aggressive behaviour. All cadets attending the United States Military Academy must take a combatives course where they are taught to compete in hand‐to‐hand combat with peers and graded on performance. This study assessed, in this highly competitive environment, the physiological, psychological, and academic predictors of success in the course's final exam, a final hand‐to‐hand combat match. Male ( n = 109) and female ( n = 23) cadets completed self‐report assessments of resilience (Connor–Davidson Resilience Scale; CD‐RISC), mental toughness (Mental Toughness Questionnaire; MTQ‐10), and aggression (Buss‐Perry Aggression Questionnaire; BPAQ) upon enrolment in Combatives. Immediately preceding the final match, cadets provided saliva samples and completed mood state (Profile of Mood States; POMS), self‐confidence and competitive state anxiety (Competitive State Anxiety Inventory; CSAI‐2) questionnaires. Cortisol, testosterone, and secretory immunoglobulin A (SIgA) in saliva were assessed. Instructors provided match outcome, win versus loss, and each cadet's grade point averages (GPA; academic, military, and physical). Logistic regression analyses determined if physiological, psychological, or academic variables predicted match outcome. Sex, time of day, prior combatives experience, and midterm combatives performance were included as covariates. Greater self‐confidence (OR [95% CI]; 1.13 [1.03, 1.25]) and a better physical GPA (4.51 [1.52, 13.42]) were associated with increased odds of winning the final match, with an overall classification accuracy of 68.9% and explained 31% of the variance in match outcome. Greater cognitive anxiety independently decreased the odds of winning (0.93 [0.87, 0.99]), but not when combined with self‐confidence and physical GPA. No other factors significantly impacted odds of winning. Self‐confidence and physical performance are key contributors to success in hand‐to‐hand combat and may mediate the influence of anxiety on performance.

A physical performance gap between sexes exists with females generally performing worse than men. However, physical performance has improved over time across sex, with the rate of improvement greater for females. Given recent efforts by the US military to facilitate sex-integration, this study examined the extent to which sex differences are present in elite military personnel. Graduates of the US Army Ranger Course (70 M; 12 F) were compared across measures of body composition (anthropometry and dual-energy X-ray absorptiometry), aerobic capacity, biomarkers of health, and survey assessments of nutritional supplement intake, psychological and lifestyle factors. Graduates had similar time in service, military experience, grit, resilience, sport participation, and outdoor hobbies. Females attained a higher level of education (P = 0.015) and rank (P = 0.023) than males. Females had lower bone mineral content (P = 0.049) and fat-free mass (P = 0.014) than males with similar fat mass (P = 0.487). Absolute and relative aerobic capacity differed by sex (P = 0.001). There were no differences overall in nutritional supplement use, but females reported greater vitamin and mineral supplement-use than males (P = 0.004). Females had lower albumin, ferritin, glucose, and higher hemoglobin A1C, potassium, and sodium than males (P < 0.05). Sport participation, psychological attributes (i.e., grit and resilience), biomarkers of health, and nutritional supplement use were similar between male and female elite military schools graduates, though fat-free mass and aerobic capacity differed by sex as expected. This study suggests that when elite, high performing male and female soldiers are compared, their mental state and physical performance are more similar than same sex civilian counterparts.NEW & NOTEWORTHY A physical performance gap exists between sex, however over time the rate of improvement has been greater for females. Unlike trends in civilian sport, comparative analysis among elite warfighters revealed fewer sex differences in body composition, psychological outcomes, and self-directed lifestyle choices, including history of sport participation, military experience, and nutritional supplement use. This initial comparison indicates males and females are similar individuals with many common defining traits and characteristics of elite warfighters.

This study investigated the effects of fermentable fiber and polyphenol supplementation on mood and cognition following rapid ascent to simulated 4300 m. Healthy adults (n = 13, 21 ± 3 years) participated in a randomized, placebo-controlled crossover study consisting of three, 2-week phases separated by ≥1 week. Food products containing the fiber and polyphenol supplement or placebo were consumed during each phase. During the final 2 days of each phase, participants resided in a hypobaric chamber for 36 h simulating low (500 m) or high (4300 m) altitude, creating three conditions: placebo-500 m, placebo-4300 m, and supplement-4300 m. A computerized cognitive test battery was administered each morning, evening, and ~36 h post-chamber residence to assess mood and cognition. Total mood disturbance, tension, fatigue, and depression were higher, and total risk-propensity score, energy, self-control, and invincibility were lower at 4300 m versus 500 m independent of supplementation. Relative to placebo-500 m, anger was higher during placebo-4300 m, but not supplement-4300 m, whereas confusion was greater during supplement-4300 m but not placebo-4300 m. More vigilance false alarms occurred during 500 m versus 4300 m independent of supplementation. Although short supplementation and washout periods may have limited observable effects, findings do not support favorable effects of this fiber and polyphenol supplement on cognition but suggest the supplement may attenuate hypobaric hypoxia-induced increases in anger.

Soldiers are challenged with interpreting information in unpredictable contexts, while maintaining high levels of job-specific performance. Virtual reality (VR) provides a controlled, immersive environment to evaluate military-relevant tasks under stress. This study determined psychological, physical, and cognitive associations with military-relevant VR task performance. Twenty-five male active-duty soldiers completed baseline psychological and cognitive assessments and then returned twice to complete VR-based Recognition Memory (RMT), Spatial Orienting (SOT), and Decision-Making (DMT) tasks under conditions of stress (active threat of torso electric shock) or no stress (torso vibration only). Baseline measures were categorized into 13 domains and standardized via z-scores. Generalized estimating equations were run with experimental condition (shock vs. vibrate) as the within-subject variable. Variables associated with correct object identification during the RMT include coping skills (e.g., acceptance), physical fitness (e.g., 2-mile run time), social intelligence, and personality traits (e.g., conscientiousness). Other coping skills (e.g., denial) decreased the odds of correct identification. Variables associated with accurate orienting on the SOT include coping skills (e.g., restraint), neurocognitive function (e.g., working memory), and prior video game experience. Additional measures of neurocognitive function (e.g., spatial orientation) reduced the odds of correct orientation. Variables associated with distinguishing targets during the DMT include coping skills (e.g., acceptance) and neurocognitive function (e.g., spatial orientation). Other coping skills (e.g., disengagement coping styles) reduced these odds. Coping skills, specifically higher acceptance, are associated with performance on military-relevant VR tasks and should be examined further to better understand how military performance could benefit from interventions targeting modifiable characteristics.

Extracellular vesicles (EVs) are small, membrane-bound vesicles that transfer biological content through the extracellular environment. The role of EVs in energy metabolism has primarily focused on EV proteins and microRNAs, with less attention on the metabolic content of EVs. This exploratory study assessed changes in the EV metabolome in response to an arduous, 16-day military training exercise. Forty male soldiers (21 ± 2 yr, 24.8 ± 2.7 kg/m2) provided blood from which circulating EVs were isolated and completed assessments of body composition and lower body power on days 1 (PRE) and 16 (POST) of a mountain training exercise (MTX). Total daily energy expenditure during the MTX was 4,187 ± 519 kcal·day-1. Fat mass (POST-PRE [95% confidence interval]: -0.9 [-1.3, -0.6] kg), lean body mass (-1.6 [-2.0, -1.2] kg), body fat percentage (-0.7 [-1.1, -0.3]%), and lower body power (-133 [-204, -63] W) decreased from PRE to POST (P < 0.05). Global metabolite profiling identified 81 metabolites from lipid (81%), energy (5%), cofactor and vitamin (5%), xenobiotic (4%), carbohydrate (2%), amino acid (1%), and nucleotide (1%) pathways in serum-derived EVs. After adjusting for EV concentration, 11 metabolites were different from PRE to POST (P < 0.05, Q < 0.20), with the largest increases in the oxidative stress-associated metabolites 5-oxoproline and benzoate. Changes in lean body mass were positively associated with changes in the energy metabolites citrate (ρ = 0.361, P = 0.022) and phosphate (ρ = 0.369, P = 0.019). Findings suggest that EV metabolites change in response to physiological stress and reflect increased oxidative stress, energy metabolism, and fatty acid metabolism, which may provide early indicators of stress adaptations relevant for optimizing training and sustaining military performance.NEW & NOTEWORTHY EV metabolites change in response to periods of increased metabolic demand, reflecting increased oxidative stress, energy metabolism, and fatty acid metabolism, and may be associated with changes in lean body mass. This exploratory study adds to the limited existing literature by highlighting the potential of EV-derived metabolites to provide insight into metabolic responses and their contribution to stress-induced metabolic adaptations.

BACKGROUND:Resistance training confers numerous health benefits that are mediated in part by circulating factors. Toward an enhanced molecular understanding, there is growing interest in a class of signaling biomarkers called extracellular vesicles (EV). EVs support physiological adaptations to exercise by transporting their cargo (e.g., microRNA (miRNA)) to target cells. Previous studies of changes in EV cargo have focused on aerobic exercise, with limited data examining the effects of resistance exercise. We examined the effect of acute resistance exercise on circulating EV miRNAs and their predicted target pathways. METHODS:Ten participants (5 men; age, 26.9 ± 5.5 yr; height, 173.4 ± 10.5 cm; body mass, 74.0 ± 11.1 kg; body fat, 25.7% ± 11.6%) completed an acute heavy resistance exercise test (AHRET) consisting of six sets of 10 repetitions of back squats using 75% one-repetition maximum. Pre-/post-AHRET, EVs were isolated from plasma using size exclusion chromatography, and RNA sequencing was performed. Differentially expressed miRNAs between pre- and post-AHRET EVs were analyzed using Ingenuity Pathway Analysis to predict target messenger RNAs and their target biological pathways. RESULTS:Overall, 34 miRNAs were altered by AHRET ( P < 0.05), targeting 4895 mRNAs, with enrichment of 175 canonical pathways ( P < 0.01), including 12 related to growth/metabolism (p53, IGF-I, STAT3, PPAR, JAK/STAT, growth hormone, WNT/β-catenin, ERK/MAPK, AMPK, mTOR, and PI3K/AKT) and 8 to inflammation signaling (TGF-β, IL-8, IL-7, IL-3, IL-6, IL-2, IL-17, IL-10). CONCLUSIONS:Acute resistance exercise alters EV miRNAs targeting pathways involved in growth, metabolism, and immune function. Circulating EVs may serve as significant adaptive signaling molecules influenced by exercise training.

Hand-to-hand combat training, known as combatives, instructs Soldiers in close-quarters combat techniques and how to cope with stress, understand controlled physical aggression, and develop self-confidence when engaged in such activities. Limited research in combat sports suggests men and women may respond to combatives stress differently. Given the increasing integration of women into close combat roles in the military, investigation of sex differences in the physiological and psychological response to combatives among military-trained personnel is warranted. PURPOSE: This study was designed to identify sex differences in stress and gonadal hormones, mucosal immunity, and mood states in a military combatives training course. METHODS: U.S. Military Academy Cadets (men = 144, women = 37) enrolled in a 2-month Combat Applications Course at West Point completed the Profile of Mood States and Competitive State Anxiety Inventory-2 and provided salivary samples at baseline prior to the course, and immediately prior to their midterm and final combat matches. Combat matches were gender- and weight-matched. Additional salivary samples were collected immediately following the first midterm and final matches. Salivary cortisol, testosterone, secretory immunoglobulin A (SIgA) and estradiol (women only) were measured via immunoassay. Men and women were compared over time with linear mixed effects models. RESULTS: In both men and women, confusion, tension, anger, cognitive anxiety, somatic anxiety, and self-confidence increased throughout the course whereas friendliness and SIgA secretion rate decreased (all p < 0.05). Compared to women, men had a greater acute increase in cortisol from pre- to post-match (p = 0.043). Prior to the final match, women displayed higher ratings of tension (20.5 +/- 9.3 vs. 16.0 +/- 8.6) and cortisol (0.6 +/- 0.3 vs. 0.4 +/- 0.3 g/dL) than men (all p < 0.05). After controlling for previous combative experience, ratings of tension did not differ by sex but remained elevated prior to midterm and final compared to baseline. CONCLUSION: Combatives training elicited significant psychological and physiological stress and decreased mucosal immunity in both men and women. Women exhibited higher tension at the final match, likely due to lack of previous combative experience. Self-confidence increased from baseline suggesting that the skills learned may help Cadets prepare for combatives and other activities that require controlled aggression.

ABSTRACT:Martin, BJ, Wright, M, Patel, V, Susmarski, A, Lovalekar, M, Forse, JN, Beckner, ME, Ledford, AK, and Nindl, BC. Physiological, physical, and psychological determinants of success during the naval special warfare screener selection course. J Strength Cond Res 39(2): e162-e170, 2025-The Naval Special Warfare (NSW) screener is an arduous, 24-h course conducted at the Naval Academy in Midshipmen aspiring to enter the Navy's Sea, Air, and Land program. The purpose was to assess and characterize the physiological stress imposed during the 24-hour screener and identify physical, physiological, and psychological differences between finishers and nonfinishers. Forty-eight male Midshipmen between the ages of 18 and 26 years (height = 177.5 ± 6.8 cm, mass = 77.0 ± 5.3 kg, percent body fat = 7.54 ± 2.7%) participated. Before 4-6 weeks of the screener, subjects performed a battery of physical measures, questionnaires, and a cold pressor test (CPT). Blood was collected at baseline, post-CPT, and pre- and postscreener to assess the effects of the screener and differences between finishers and nonfinishers. A total of 48 Midshipmen started the screener, 37 finishers and 11 nonfinishers. Logistic regression revealed that 4 measures significantly increased the likelihood of finishing. A higher likelihood of finishing the screener was observed with Midshipmen with greater height (∼5 cm, p = 0.036), higher anaerobic power (∼0.5 W·kg -1 , p = 0.036), greater low-back endurance (∼17 s, p = 0.039), and faster swim times (∼1 minute, p = 0.001). Dehydroepiandrosterone (DHEA) and serum cortisol were both lower after the CPT in finishers ( p = 0.042 and 0.004, respectively) but were not different in nonfinishers. Dehydroepiandrosterone and the DHEA:salivary cortisol ratio were lower postscreener in finishers vs. nonfinishers (-70% and -133%, p = 0.008 and 0.001, respectively). In conclusion, this study presents novel findings regarding differences between finishers and nonfinishers of the NSW screener and how a 24-h event of particularly intense stressors affects biomarkers in a select group of Naval Academy Midshipmen.

Changes in bone microarchitecture resulting from chronic physical stress such as that experienced during U.S. Army Basic Combat Training (BCT) underscore its adaptive potential. There is a need for noninvasive biomarkers of adaptive bone formation that can be obtained at scale in real-world settings. Differential mass spectrometry (dMS), a label-free quantitative proteomics technique, may provide useful information about bone adaptation based on the proteomic features of urine. Purpose: The purpose of this study is to optimize a dMS-based urinary proteomic technique and evaluate the relationship between urinary proteome content and adaptive changes in bone microarchitecture during BCT. Methods: Urinary proteomes were analyzed with an optimized dMS technique in two groups of 13 recruits (N = 26) at the beginning (Pre) and end (Post) of BCT. Matched by age (21 +/- 4 yr), sex (16 W), and baseline tibial trabecular bone volume fractions (Tb.BV/TV), these groups were distinguished by the most substantial (High) and minimal (Low) improvements in Tb.BV/TV. Differential protein expression was analyzed with mixed permutation ANOVA and false discovery proportion-based adjustment for multiple comparisons. Results: Tibial Tb.BV/TV increased from pre- to post-BCT in High (3.30 +/- 1.64%, P < 0.0001) but not Low (-0.35 +/- 1.25%, P = 0.4707). The optimized dMS technique identified 10,431 peptides from 1368 protein groups that represented 165 integrative biological processes. Seventy-four urinary proteins changed from pre- to post-BCT (P = 0.0019), and neutrophil-mediated immunity was the most prominent ontology. Two proteins (immunoglobulin heavy constant gamma 4 and C-type lectin domain family 4 member G) differed from pre- to post-BCT in High and Low (P = 0.0006). Conclusions: The dMS technique can identify more than 1000 urinary proteins. At least 74 proteins are responsive to BCT, and other principally immune system-related proteins show differential expression patterns that coincide with adaptive bone formation.