An observational objective job analysis of role related tasks undertaken by Royal Navy sailors.

BACKGROUND: The current in-service Royal Naval Fitness Test has two elements to test the aerobic endurance and muscular strength of Service Personnel through generic field-based tests and a short job task simulation. However, in 2017 the Royal Navy (RN) identified a requirement to update their in-service fitness test to align with international best practice. OBJECTIVE: The purpose of this study was to conduct an Objective Job Task Analysis on critical, physically demanding tasks that could be undertaken by RN sailors during sea deployments. METHODS: Twenty-one training exercises were observed across a range of contexts; Type 23 Frigates, Type 45 Destroyers and at shore-based training facilities. A total of 203 RN personnel (age 27.8±7.1 years) were observed undertaking 36 job related tasks (e.g., 'firefighting', 'damage control', 'abandon ship' and 'casualty handling'). Tasks were evaluated by cardiovascular response, primary functional movements and contextual factors to aid a Military Judgement Panel in task list down-selection. RESULTS: 14 Criterion Tasks (e.g., 'firefighting', 'two-person magazine stowage' and 'casualty handling') were selected to progress to the next stage of the process. Five tasks were selected based on cardiovascular responses and a further nine tasks selected based on task ergonomics and other factors. CONCLUSION: This research has identified and quantified the most physically demanding, critical roles undertaken by RN sailors on sea deployments and will inform the development of the RN Physical Employment Standard.

A job task analysis of the authorised firearms officer - counter terrorism (AFO-CT) national role profile.

BACKGROUND: The Ministry of Defence Police recognised the requirement to develop a Physical Employment Standard (PES) for the Authorised Firearms Officer -Counter Terrorism (AFO-CT) role profile. OBJECTIVE: The purpose of this study was to conduct a job task analysis to identify the most critical and physically demanding tasks performed by AFO-CT personnel. METHODS: A focus group and online survey were undertaken to identify a list of job tasks. The down-selected job tasks were objectively monitored during training events to determine the most physically demanding tasks. Tasks were ranked by physical demand and additional factors (e.g., operational load, primary physical actions). Down-selected tasks were then included in a Subject Matter Experts (SME) task scenario generation workshop. The physiological demands of the resulting standardised scenarios were determined. RESULTS: The focus group (n = 11) identified 13 physically demanding and critical role-related tasks. The subsequent survey (n = 907) down-selected eight tasks with a 'moderate' demand or greater. Thirty AFO-CT personnel completed the eight tasks as part of routine training events. From the observed tasks, four tasks were down-selected and combined into two operationally relevant, reasonable worst-case standardised scenarios during a SME workshop. The two scenarios, 'Conduct Armed Search in the Open for an Active Shooter' and 'Victim Focussed Emergency Search' were used in subsequent phases of the research to form the basis of the AFO-CT PES. CONCLUSION: This research elucidated the most physically demanding job tasks within the AFO-CT role profile to inform the development of a MOD armed policing PES.

Barriers and facilitators to implementation of musculoskeletal injury mitigation programmes for military service members around the world: a scoping review.

INTRODUCTION: Musculoskeletal injury (MSK-I) mitigation and prevention programmes (MSK-IMPPs) have been developed and implemented across militaries worldwide. Although programme efficacy is often reported, development and implementation details are often overlooked, limiting their scalability, sustainability and effectiveness. This scoping review aimed to identify the following in military populations: (1) barriers and facilitators to implementing and scaling MSK-IMPPs; (2) gaps in MSK-IMPP research and (3) future research priorities. METHODS: A scoping review assessed literature from inception to April 2022 that included studies on MSK-IMPP implementation and/or effectiveness in military populations. Barriers and facilitators to implementing these programmes were identified. RESULTS: From 132 articles, most were primary research studies (90; 68.2%); the remainder were review papers (42; 31.8%). Among primary studies, 3 (3.3%) investigated only women, 62 (69%) only men and 25 (27.8%) both. Barriers included limited resources, lack of stakeholder engagement, competing military priorities and equipment-related factors. Facilitators included strong stakeholder engagement, targeted programme design, involvement/proximity of MSK-I experts, providing MSK-I mitigation education, low burden on resources and emphasising end-user acceptability. Research gaps included variability in reported MSK-I outcomes and no consensus on relevant surveillance metrics and definitions. CONCLUSION: Despite a robust body of literature, there is a dearth of information about programme implementation; specifically, barriers or facilitators to success. Additionally, variability in outcomes and lack of consensus on MSK-I definitions may affect the development, implementation evaluation and comparison of MSK-IMPPs. There is a need for international consensus on definitions and optimal data reporting elements when conducting injury risk mitigation research in the military.

No protective benefits of low dose acute L-glutamine supplementation on small intestinal permeability, epithelial injury and bacterial translocation biomarkers in response to subclinical exertional-heat stress: A randomized cross-over trial.

Exertional heat stress disrupts gastrointestinal permeability and, through subsequent bacterial translocation, can result in potentially fatal exertional heat stroke. Glutamine supplementation is a potential countermeasure although previously validated doses are not universally well tolerated. Ten males completed two 80-minute subclinical exertional heat stress tests (EHSTs) following either glutamine (0.3 g kg FFM-1) or placebo supplementation. Small intestinal permeability was assessed using the lactulose/rhamnose dual sugar absorption test and small intestinal epithelial injury using Intestinal Fatty-Acid Binding Protein (I-FABP). Bacterial translocation was assessed using the total 16S bacterial DNA and Bacteroides/total 16S DNA ratio. The glutamine bolus was well tolerated, with no participants reporting symptoms of gastrointestinal intolerance. Small intestinal permeability was not influenced by glutamine supplementation (p = 0.06) although a medium effect size favoring the placebo trial was observed (d = 0.73). Both small intestinal epithelial injury (p < 0.01) and Bacteroides/total 16S DNA (p = 0.04) increased following exertional heat stress, but were uninfluenced by glutamine supplementation. Low-dose acute oral glutamine supplementation does not protect gastrointestinal injury, permeability, or bacterial translocation in response to subclinical exertional heat stress.

Acute L-glutamine supplementation does not improve gastrointestinal permeability, injury or microbial translocation in response to exhaustive high intensity exertional-heat stress.

Purpose: Exertional-heat stress adversely distrupts (GI) barrier integrity and, through subsequent microbial translocation (MT), can result in potentially fatal exertional-heat stroke. Acute glutamine (GLN) supplementation is a potential nutritional countermeasure, although the practical value of current supplementation regimens is questionable.Method: Ten males completed two high-intensity exertional-heat stress tests (EHST) involving running in the heat (40°C and 40% relative humidity) at lactate threshold to volitional exhaustion. Participants ingested GLN (0.3 g kg FFM-1) or a non-calorific placebo (PLA) one hour prior to the EHST. Venous blood was drawn pre-, post- and one-hour post-EHST. GI permeability was assessed using a serum dual-sugar absorption test (DSAT) and small intestinal epithelial injury using plasma Intestinal Fatty-Acid Binding Protein (I-FABP). MT was assessed using the Bacteroides/total 16S DNA ratio.Results: Volitional exhaustion occurred after 22:19 ± 2:22 (minutes: seconds) in both conditions, during which whole-body physiological responses and GI symptoms were not different (p > 0.05). GI permeability (serum DSAT) was greater following GLN (0.043 ± 0.020) than PLA (0.034 ± 0.019) (p = 0.02; d = 0.47), but small intestine epithelial injury (I-FABP) increased comparably (p = 0.22; ηp2 = 0.16) following the EHST in both trials (GLN Δ = 1.25 ± 0.63 ng ml-1; PLA Δ = 0.92 ± 0.44 ng ml-1). GI MT (Bacteroides/total 16S DNA ratio) was unchanged in either condition following the EHST (p = 0.43).Conclusion: Acute low-dose (0.3 g kg-1 fat free mass) GLN supplementation ingested one hour before high-intesity exertional-heat stress worsened GI permeability, but did not influence either small intestinal epithilial injury or microbial translocation.Abbreviations: ANOVA: Analysis of variance; CV: Coefficient of Variation; DSAT: Dual Sugar Absorption Test; EDTA: Ethylenediaminetetraacetic acid; EHST: Exertional Heat Stress Test; ELISA: Enzyme Linked Immunosorbent Assay; FFM: Fat Free Mass; GI: Gastrointestinal; GFR: Glomerular Filtration Rate; GLN: Glutamine; HPLC: High Performance Liquid Chromatography; HR: Heart Rate; I-FABP: Intestinal Fatty-Acid Binding Protein; ISAK: International Society for the Advancement of Anthropometric Kinanthropometry; L/R: Lactulose-to-Rhamnose; LT: Lactate Threshold; MT: Microbial Translocation; mVAS: Modified Visual Analogue Scale; PBS: Phosphate-Buffered Saline; PLA: Placebo; qPCR: Quantitative Polymerase Chain Reaction; RH: Relative Humidity; RPE: Rate of Perceived Exertion; SD: Standard Deviation; SEM: Sensor Electronics Module; Tcore: Core Body Temperature; Tbody: Mean Body Temperature; Tskin: Mean Skin Temperature; TS: Thermal Sensation; V̇O2max: Maximal Oxygen Uptake.Highlights The pathophysiology of exertional-heat stroke is widely hypothesised to be at least in part attributable to a systemic inflammatory response caused by the leak of gastrointestinal microbes into the circulating blood.Acute high-dose (0.9 g kg FFM-1) L-glutamine supplementation is widely promoted as a practical strategy to protect gastrointestinal barrier integrity during exertional-heat stress. However, previously validated doses are often poorly tolerated and cannot be recommended for widespread implementation.This study examined the efficacy of low-dose (0.30 g kg FFM-1; ∼20 grams) acute L-glutamine supplementation on small intestinal injury, permeability, and microbial translocation in response a high-intensity exertional-heat stress test to exhaustion (20-30 min). This type of exercise accounts for the majority of exertional-heat stroke cases in the military.Despite being universally well-tolerated across all participants, acute low-dose L-glutamine supplementation worsened gastrointestinal permeability, without influencing either small intestinal injury or microbial translocation. These findings do not support the application of low-dose L-glutamine supplementation to help prevent exertional-heat stroke.

Military nutrition research: Contemporary issues, state of the science and future directions.

The importance of diet and nutrition to military readiness and performance has been recognized for centuries as dietary nutrients sustain health, protect against illness, and promote resilience, performance and recovery. Contemporary military nutrition research is increasingly inter-disciplinary with emphasis often placed on the broad topics of (1) determining operational nutrition requirements in all environments, (2) characterizing nutritional practices of military personnel relative to the required (role/environment) standards, and (3) developing strategies for improving nutrient delivery and individual choices. This review discusses contemporary issues shared internationally by military nutrition research programmes, and highlights emerging topics likely to influence future military nutrition research and policy. Contemporary issues include improving the diet quality of military personnel, optimizing operational rations, and increasing understanding of biological factors influencing nutrient requirements. Emerging areas include the burgeoning field of precision nutrition and its technological enablers.

Staphylococcus argenteus transmission among healthy Royal Marines: A molecular epidemiology case-study.

Objectives During a prospective study of S. aureus carriage in Royal Marines recruits, six S. argenteus strains were identified in four recruits. As S. argenteus sepsis leads to mortality similar to S. aureus, we determined the potential for within same troop transmission, to evaluate future outbreak risk. Methods We used whole-genome sequencing to characterise S. argenteus and investigate phylogenetic relationships between isolates. Results S. argenteus strains (t5078, ST2250) were detected in 4/40 recruits in the same troop (training cohort) in weeks 1, 6 or 15 of training. No mec, tsst or LukPV genes were detected. We identified differences of 1-17 core SNPs between S. argenteus from different recruits. In two recruits, two S. argenteus strains were isolated; these could be distinguished by 2 and 15 core SNPs. Conclusions The identification of S. argenteus within a single troop from the total recruit population suggests a common source for transmission, though high number of SNPs were identified, both within-host and within-cluster. The high number of SNPs between some isolates may indicate a common source of diverse isolates or a high level of S. argenteus mutation in carriage. S. argenteus is newly recognized species; and understanding of the frequency of genetic changes during transmission and transition from asymptomatic carriage to disease is required.

Individual risk factors associated with exertional heat illness: A systematic review.

NEW FINDINGS: What is the topic of this review? Exertional heat illness (EHI) remains a persistent problem for athletes and individuals. This threat remains despite numerous athletic position statements and occupational guidance policies. This review explores primary evidence that demonstrates a direct association between 'known' risk factors and EHI. What advances does it highlight? Primary evidence to support 'known' risk factors associated with EHI is not comprehensive. Furthermore, it is not evident that single individual factors predispose individuals to greater risk. In fact, the evidence indicates that EHI can manifest in non-hostile compensable environments when a combination of risk factors is prevalent. ABSTRACT: Despite the widespread knowledge of exertional heat illness (EHI) and clear guidance for its prevention, the incidence of EHI remains high. We carried out a systematic review of available literature evaluating the scientific evidence underpinning the risk factors associated with EHI. Medline, PsycINFO, SportDiscus and Embase were searched from inception to January 2019 with no date limitation, with supplementary searches also being performed. Search terms included permutations of risk and heat illness, with only studies in English included. Study selection, data extraction and quality assessment, using the QUALSYST tool, were performed by two independent reviewers. Of 8898 articles identified by the searches, 42 were included in the systematic review as primary evidence demonstrating a link between a risk factor and EHI. The quality scores ranged from 57.50 to 100%, and studies were generally considered to be of strong quality. The majority of risks attributable to EHI were categorized as those associated with lifestyle factors. The findings from the systematic review suggest complex manifestation of EHI through multiple risk factors rather than any one factor in isolation. Further research is needed to explore the accumulation of risk factors to help in development of effective preventative measures.

Gastrointestinal Tolerance of Low, Medium and High Dose Acute Oral l-Glutamine Supplementation in Healthy Adults: A Pilot Study.

l-Glutamine (GLN) is a conditionally essential amino acid which supports gastrointestinal (GI) and immune function prior to catabolic stress (e.g., strenuous exercise). Despite potential dose-dependent benefits, GI tolerance of acute high dose oral GLN supplementation is poorly characterised. Fourteen healthy males (25 ± 5 years; 1.79 ± 0.07 cm; 77.7 ± 9.8 kg; 14.8 ± 4.6% body fat) ingested 0.3 (LOW), 0.6 (MED) or 0.9 (HIGH) g·kg·FFM-1 GLN beverages, in a randomised, double-blind, counter-balanced, cross-over trial. Individual and accumulated GI symptoms were recorded using a visual analogue scale at regular intervals up to 24-h post ingestion. GLN beverages were characterised by tonicity measurement and microscopic observations. 24-h accumulated upper- and lower- and total-GI symptoms were all greater in the HIGH, compared to LOW and MED trials (p < 0.05). Specific GI symptoms (discomfort, nausea, belching, upper GI pain) were all more pronounced on the HIGH versus LOW GLN trial (p < 0.05). Nevertheless, most symptoms were still rated as mild. In comparison, the remaining GI symptoms were either comparable (flatulence, urge to regurgitate, bloating, lower GI pain) or absent (heart burn, vomiting, urge to defecate, abnormal stools, stitch, dizziness) between trials (p > 0.05). All beverages were isotonic and contained a dose-dependent number of GLN crystals. Acute oral GLN ingestion in dosages up to 0.9 g·kg·FFM-1 are generally well-tolerated. However, the severity of mild GI symptoms appeared dose-dependent during the first two hours post prandial and may be due to high-concentrations of GLN crystals.

Influence of aerobic fitness on gastrointestinal barrier integrity and microbial translocation following a fixed-intensity military exertional heat stress test.

PURPOSE: Exertional-heat stress adversely disrupts gastrointestinal (GI) barrier integrity, whereby subsequent microbial translocation (MT) can result in potentially serious health consequences. To date, the influence of aerobic fitness on GI barrier integrity and MT following exertional-heat stress is poorly characterised. METHOD: Ten untrained (UT; VO2max = 45 ± 3 ml·kg-1·min-1) and ten highly trained (HT; VO2max = 64 ± 4 ml·kg-1·min-1) males completed an ecologically valid (military) 80-min fixed-intensity exertional-heat stress test (EHST). Venous blood was drawn immediately pre- and post-EHST. GI barrier integrity was assessed using the serum dual-sugar absorption test (DSAT) and plasma Intestinal Fatty-Acid Binding Protein (I-FABP). MT was assessed using plasma Bacteroides/total 16S DNA. RESULTS: UT experienced greater thermoregulatory, cardiovascular and perceptual strain (p < 0.05) than HT during the EHST. Serum DSAT responses were similar between the two groups (p = 0.59), although Δ I-FABP was greater (p = 0.04) in the UT (1.14 ± 1.36 ng·ml-1) versus HT (0.20 ± 0.29 ng·ml-1) group. Bacteroides/Total 16S DNA ratio was unchanged (Δ; -0.04 ± 0.18) following the EHST in the HT group, but increased (Δ; 0.19 ± 0.25) in the UT group (p = 0.05). Weekly aerobic training hours had a weak, negative correlation with Δ I-FABP and Bacteroides/total 16S DNA responses. CONCLUSION: When exercising at the same absolute workload, UT individuals are more susceptible to small intestinal epithelial injury and MT than HT individuals. These responses appear partially attributable to greater thermoregulatory, cardiovascular, and perceptual strain.

Estimated and measured core temperature responses to high-intensity warm weather military training: implications for exertional heat illness risk assessment.

OBJECTIVE: Humans avoid overheating through physiological and behavioral mechanisms. However, elite athletes, industrial workers, and military personnel, driven by the tasks at hand, may choose to continue working and face an increased risk of exertional heat illness (EHI). We wanted to examine the efficacy of a new core temperature (Tcr) estimation algorithm in assessing EHI risk. APPROACH: Physiological responses of 21 male Royal Marines recruits (age 21 ± 2 y, height 1.79 ± 0.05 m, weight 80.5 ± 7.2 kg) were collected during a physically-demanding criterion road march (14.5 km in 90 min with a 9.6 kg load; air temperature 16 °C, relative humidity ≥ 84%). Measured Tcr (thermometer pill) and estimated Tcr (ECTempTM Tcr-est) were compared. MAIN RESULTS: Measured Tcr either increased to an asymptote Tcr < 39.5 °C (WARM; n= 11), or progressively increased to Tcr > 40.0 °C (HOT; n= 10). In the HOT group, Tcr-est reflected measured Tcr up to Tcr = 40.0 °C (Bias = - 0.10 ± 0.37 °C, root mean square error = 0.37 ± 0.13 °C). In the WARM group, Tcr-est overestimated Tcr (Bias = 0.34 ± 0.40 °C) and was higher from mid-point to end. A logistic regression (Skin temperature approximate entropy and mean heart rate) was able to predict group membership (95% accuracy) at 20 min, allowing a WARM group ECTempTM correction factor (corrected Bias = 0.00 ± 0.29 °C). SIGNIFICANCE: The Tcr-est successfully tracked Tcr in the HOT group with high risk of exertional heat illness (EHI) (40% incidence). Skin temperature complexity shows promise as a non-invasive means of insight into the state of thermoregulatory control mechanisms.

Low serum 25-hydroxyvitamin D status in the pathogenesis of stress fractures in military personnel: An evidenced link to support injury risk management.

Stress fractures are common amongst healthy military recruits and athletes. Reduced vitamin D availability, measured by serum 25-hydroxyvitamin D (25OHD) status, has been associated with stress fracture risk during the 32-week Royal Marines (RM) training programme. A gene-environment interaction study was undertaken to explore this relationship to inform specific injury risk mitigation strategies. Fifty-one males who developed a stress fracture during RM training (n = 9 in weeks 1-15; n = 42 in weeks 16-32) and 141 uninjured controls were genotyped for the vitamin D receptor (VDR) FokI polymorphism. Serum 25OHD was measured at the start, middle and end (weeks 1, 15 and 32) of training. Serum 25OHD concentration increased in controls between weeks 1-15 (61.8±29.1 to 72.6±28.8 nmol/L, p = 0.01). Recruits who fractured did not show this rise and had lower week-15 25OHD concentration (p = 0.01). Higher week-15 25OHD concentration was associated with reduced stress fracture risk (adjusted OR 0.55[0.32-0.96] per 1SD increase, p = 0.04): the greater the increase in 25OHD, the greater the protective effect (p = 0.01). The f-allele was over-represented in fracture cases compared with controls (p<0.05). Baseline 25OHD status interacted with VDR genotype: a higher level was associated with reduced fracture risk in f-allele carriers (adjusted OR 0.39[0.17-0.91], p = 0.01). Improved 25OHD status between weeks 1-15 had a greater protective effect in FF genotype individuals (adjusted OR 0.31[0.12-0.81] vs. 1.78[0.90-3.49], p<0.01). Stress fracture risk in RM recruits is impacted by the interaction of VDR genotype with vitamin D status. This further supports the role of low serum vitamin D concentrations in causing stress fractures, and hence prophylactic vitamin D supplementation as an injury risk mitigation strategy.

Reliability of gastrointestinal barrier integrity and microbial translocation biomarkers at rest and following exertional heat stress.

PURPOSE: Exertional heat stress adversely distrupts (GI) barrier integrity and, through subsequent microbial translocation (MT), negativly impacts health. Despite widespread application, the temporal reliability of popular GI barrier integity and MT biomarkers is poorly characterised. METHOD: Fourteen males completed two 80-min exertional heat stress tests (EHST) separated by 7-14 days. Venous blood was drawn pre, immediately- and 1-hr post both EHSTs. GI barrier integrity was assessed using the serum Dual-Sugar Absorption Test (DSAT), Intestinal Fatty-Acid-Binding Protein (I-FABP) and Claudin-3 (CLDN-3). MT was assessed using plasma Lipopolysaccharide Binding Protein (LBP), total 16S bacterial DNA and Bacteroides DNA. RESULTS: No GI barrier integrity or MT biomarker, except absolute Bacteroides DNA, displayed systematic trial order bias (p ≥ .05). I-FABP (trial 1 = Δ 0.834 ± 0.445 ng ml-1 ; trial 2 = Δ 0.776 ± 0.489 ng ml-1 ) and CLDN-3 (trial 1 = Δ 0.317 ± 0.586 ng ml-1 ; trial 2 = Δ 0.371 ± 0.508 ng ml-1 ) were increased post-EHST (p ≤ .01). All MT biomarkers were unchanged post-EHST. Coefficient of variation and typical error of measurement post-EHST were: 11.5% and 0.004 (ratio) for the DSAT 90-min postprobe ingestion; 12.2% and 0.004 (ratio) at 150-min postprobe ingestion; 12.1% and 0.376 ng ml-1 for I-FABP; 4.9% and 0.342 ng ml-1 for CLDN-3; 9.2% and 0.420 µg ml-1 for LBP; 9.5% and 0.15 pg µl-1 for total 16S DNA; and 54.7% and 0.032 for Bacteroides/total 16S DNA ratio. CONCLUSION: Each GI barrier integrity and MT translocation biomarker, except Bacteroides/total 16S ratio, had acceptable reliability at rest and postexertional heat stress.

Prevention of Adrenal Crisis: Cortisol Responses to Major Stress Compared to Stress Dose Hydrocortisone Delivery.

CONTEXT: Patients with adrenal insufficiency require increased hydrocortisone cover during major stress to avoid a life-threatening adrenal crisis. However, current treatment recommendations are not evidence-based. OBJECTIVE: To identify the most appropriate mode of hydrocortisone delivery in patients with adrenal insufficiency who are exposed to major stress. DESIGN AND PARTICIPANTS: Cross-sectional study: 122 unstressed healthy subjects and 288 subjects exposed to different stressors (major trauma [N = 83], sepsis [N = 100], and combat stress [N = 105]). Longitudinal study: 22 patients with preserved adrenal function undergoing elective surgery. Pharmacokinetic study: 10 patients with primary adrenal insufficiency undergoing administration of 200 mg hydrocortisone over 24 hours in 4 different delivery modes (continuous intravenous infusion; 6-hourly oral, intramuscular or intravenous bolus administration). MAIN OUTCOME MEASURE: We measured total serum cortisol and cortisone, free serum cortisol, and urinary glucocorticoid metabolite excretion by mass spectrometry. Linear pharmacokinetic modeling was used to determine the most appropriate mode and dose of hydrocortisone administration in patients with adrenal insufficiency exposed to major stress. RESULTS: Serum cortisol was increased in all stress conditions, with the highest values observed in surgery and sepsis. Continuous intravenous hydrocortisone was the only administration mode persistently achieving median cortisol concentrations in the range observed during major stress. Linear pharmacokinetic modeling identified continuous intravenous infusion of 200 mg hydrocortisone over 24 hours, preceded by an initial bolus of 50-100 mg hydrocortisone, as best suited for maintaining cortisol concentrations in the required range. CONCLUSIONS: Continuous intravenous hydrocortisone infusion should be favored over intermittent bolus administration in the prevention and treatment of adrenal crisis during major stress.

The Gastrointestinal Exertional Heat Stroke Paradigm: Pathophysiology, Assessment, Severity, Aetiology and Nutritional Countermeasures.

Exertional heat stroke (EHS) is a life-threatening medical condition involving thermoregulatory failure and is the most severe condition along a continuum of heat-related illnesses. Current EHS policy guidance principally advocates a thermoregulatory management approach, despite growing recognition that gastrointestinal (GI) microbial translocation contributes to disease pathophysiology. Contemporary research has focused to understand the relevance of GI barrier integrity and strategies to maintain it during periods of exertional-heat stress. GI barrier integrity can be assessed non-invasively using a variety of in vivo techniques, including active inert mixed-weight molecular probe recovery tests and passive biomarkers indicative of GI structural integrity loss or microbial translocation. Strenuous exercise is strongly characterised to disrupt GI barrier integrity, and aspects of this response correlate with the corresponding magnitude of thermal strain. The aetiology of GI barrier integrity loss following exertional-heat stress is poorly understood, though may directly relate to localised hyperthermia, splanchnic hypoperfusion-mediated ischemic injury, and neuroendocrine-immune alterations. Nutritional countermeasures to maintain GI barrier integrity following exertional-heat stress provide a promising approach to mitigate EHS. The focus of this review is to evaluate: (1) the GI paradigm of exertional heat stroke; (2) techniques to assess GI barrier integrity; (3) typical GI barrier integrity responses to exertional-heat stress; (4) the aetiology of GI barrier integrity loss following exertional-heat stress; and (5) nutritional countermeasures to maintain GI barrier integrity in response to exertional-heat stress.

Mapping the Steroid Response to Major Trauma From Injury to Recovery: A Prospective Cohort Study.

CONTEXT: Survival rates after severe injury are improving, but complication rates and outcomes are variable. OBJECTIVE: This cohort study addressed the lack of longitudinal data on the steroid response to major trauma and during recovery. DESIGN: We undertook a prospective, observational cohort study from time of injury to 6 months postinjury at a major UK trauma centre and a military rehabilitation unit, studying patients within 24 hours of major trauma (estimated New Injury Severity Score (NISS) > 15). MAIN OUTCOME MEASURES: We measured adrenal and gonadal steroids in serum and 24-hour urine by mass spectrometry, assessed muscle loss by ultrasound and nitrogen excretion, and recorded clinical outcomes (ventilator days, length of hospital stay, opioid use, incidence of organ dysfunction, and sepsis); results were analyzed by generalized mixed-effect linear models. FINDINGS: We screened 996 multiple injured adults, approached 106, and recruited 95 eligible patients; 87 survived. We analyzed all male survivors <50 years not treated with steroids (N = 60; median age 27 [interquartile range 24-31] years; median NISS 34 [29-44]). Urinary nitrogen excretion and muscle loss peaked after 1 and 6 weeks, respectively. Serum testosterone, dehydroepiandrosterone, and dehydroepiandrosterone sulfate decreased immediately after trauma and took 2, 4, and more than 6 months, respectively, to recover; opioid treatment delayed dehydroepiandrosterone recovery in a dose-dependent fashion. Androgens and precursors correlated with SOFA score and probability of sepsis. CONCLUSION: The catabolic response to severe injury was accompanied by acute and sustained androgen suppression. Whether androgen supplementation improves health outcomes after major trauma requires further investigation.