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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.
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Personal Militar , Enfermedades Musculoesqueléticas , Masculino , Humanos , Femenino , Enfermedades Musculoesqueléticas/prevención & control , Evaluación de Programas y Proyectos de SaludRESUMEN
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.
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Trastornos de Estrés por Calor/epidemiología , Trastornos de Estrés por Calor/fisiopatología , Calor , Deportes/fisiología , Atletas , Humanos , Incidencia , Factores de RiesgoRESUMEN
OBJECTIVE: To determine the effect of prolonged exposure to a submarine environment on biomarkers of cardiometabolic risk in Royal Navy (RN) submariners. METHODS: Serum lipids (cholesterol (C), triglyceride (TG), low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL-C), non-HDL-C), glucose, insulin and anthropometrics were compared within three RN submarine crews before and after submerged patrols of 12 or 6 weeks, and with a crew that remained ashore (SUB-HOME). Dietary intake and activity patterns were self-reported during each patrol. Differences were assessed in crew characteristics using one-way analysis of variance and in serum lipids using paired t-tests. RESULTS: Postpatrol, the mean body weight of submerged crews decreased (-1.4±4.2 kg, p=0.0001), but increased in SUB-HOME (1.9±1.8 kg, p=0.0001). Modest improvements in serum lipids (mean individual change (mmol/L); C=-0.3±0.7, p=0.0001; TG=-0.3±0.7, p=0.0001; HDL-C=-0.1±0.3, p=0.0001; non-HDL-C=-0.2±0.6, p=0.012), glucose (-0.2±0.5, p=0.0001) and insulin (-1.5±4.6 mU/L, p=0.001) were observed in submerged crews. Changes in serum lipids were positively associated with changes in body weight within crews combined. Energy intake was maintained during submerged patrols but was lower compared with non-submerged (11 139±2792 vs. 9617±2466 kJ, p=0.001; 11 062±2775 vs. 9632±2682 kJ, p=0.003). CONCLUSIONS: The environment of a submerged submarine produced no adverse effects on serum biomarkers of cardiometabolic risk in crew. Conversely, modest improvements in these biomarkers were associated with a decrease in body weight.
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Biomarcadores/sangre , Peso Corporal/fisiología , Sistema Cardiovascular/metabolismo , Personal Militar/estadística & datos numéricos , Exposición Profesional/análisis , Adulto , Análisis de Varianza , Antropometría , Glucemia , HDL-Colesterol/sangre , LDL-Colesterol/sangre , Humanos , Insulina/sangre , Masculino , Persona de Mediana Edad , Medicina SubmarinaRESUMEN
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.
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Capacidad Cardiovascular , Microbioma Gastrointestinal , Trastornos de Estrés por Calor/fisiopatología , Absorción Intestinal , Adulto , Bacteroides/aislamiento & purificación , Bacteroides/patogenicidad , Ácidos Grasos/metabolismo , Trastornos de Estrés por Calor/metabolismo , Trastornos de Estrés por Calor/microbiología , Humanos , Mucosa Intestinal/metabolismo , Mucosa Intestinal/microbiología , Masculino , Esfuerzo Físico , Azúcares/metabolismoRESUMEN
Soldier operational performance is determined by their fitness, nutritional status, quality of rest/recovery, and remaining injury/illness free. Understanding large fluctuations in nutritional status during operations is critical to safeguarding health and well-being. There are limited data world-wide describing the effect of extreme climate change on nutrient profiles. This study investigated the effect of hot-dry deployments on vitamin D status (assessed from 25-hydroxyvitamin D (25(OH)D) concentration) of young, male, military volunteers. Two data sets are presented (pilot study, n 37; main study, n 98), examining serum 25(OH)D concentrations before and during 6-month summer operational deployments to Afghanistan (March to October/November). Body mass, percentage of body fat, dietary intake and serum 25(OH)D concentrations were measured. In addition, parathyroid hormone (PTH), adjusted Ca and albumin concentrations were measured in the main study to better understand 25(OH)D fluctuations. Body mass and fat mass (FM) losses were greater for early (pre- to mid-) deployment compared with late (mid- to post-) deployment (P<0·05). Dietary intake was well-maintained despite high rates of energy expenditure. A pronounced increase in 25(OH)D was observed between pre- (March) and mid-deployment (June) (pilot study: 51 (sd 20) v. 212 (sd 85) nmol/l, P<0·05; main study: 55 (sd 22) v. 167 (sd 71) nmol/l, P<0·05) and remained elevated post-deployment (October/November). In contrast, PTH was highest pre-deployment, decreasing thereafter (main study: 4·45 (sd 2·20) v. 3·79 (sd 1·50) pmol/l, P<0·05). The typical seasonal cycling of vitamin D appeared exaggerated in this active male population undertaking an arduous summer deployment. Further research is warranted, where such large seasonal vitamin D fluctuations may be detrimental to bone health in the longer-term.
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Personal Militar/estadística & datos numéricos , Vitamina D/análogos & derivados , Adulto , Afganistán , Humanos , Masculino , Estado Nutricional , Enfermedades Profesionales/sangre , Enfermedades Profesionales/etiología , Hormona Paratiroidea/sangre , Proyectos Piloto , Estaciones del Año , Factores de Tiempo , Estados Unidos , Vitamina D/sangre , Deficiencia de Vitamina D/sangre , Deficiencia de Vitamina D/etiologíaRESUMEN
OBJECTIVE: The present review evaluated the effectiveness of environmental-based interventions aimed at improving the dietary and physical activity behaviours and body composition indices of adults in institutions. DESIGN: A systematic review was conducted. Electronic databases (MEDLINE, Embase, PsycINFO, CINAHL, The Cochrane Library, Web of Science, ProQuest Dissertation and Theses, Scopus and Athena) were searched for relevant articles published between database inception and October 2017. Searching, selecting and reporting were undertaken according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. SETTING: Military establishments and maritime workplaces.ParticipantsAdults in institutions, aged 18-45 years. RESULTS: A total of 27842 articles were screened for eligibility, nine studies (reported in eleven articles) were included in the review. Five studies used multilevel strategies and four used environmental strategies only. Duration of follow-up ranged from 3 weeks to 10 years. Eight of the studies reported significant positive effects on dietary behaviours, but effect sizes varied. The study that targeted physical activity had no effect on activity levels but did have a significant positive effect on physical fitness. No evidence was identified that the studies resulted in improvements in body composition indices. CONCLUSIONS: The evidence base appears to be in favour of implementing environmental interventions in institutions to improve the dietary behaviours of adults. However, due to the small number of studies included in the review, and the variable methodological quality of the studies and intervention reporting, further well-designed evaluation studies are required.
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Dieta Saludable/psicología , Ambiente , Ejercicio Físico/psicología , Promoción de la Salud/métodos , Institucionalización , Adolescente , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Adulto JovenRESUMEN
PURPOSE: To prevent heat-related illnesses, guidelines recommend limiting core body temperature (T c) ≤ 38 °C during thermal stress. Copeptin, a surrogate for arginine vasopressin secretion, could provide useful information about fluid balance, thermal strain and health risks. It was hypothesised that plasma copeptin would rise with dehydration from occupational heat stress, concurrent with sympathoadrenal activation and reduced glomerular filtration, and that these changes would reflect T c responses. METHODS: Volunteers (n = 15) were recruited from a British Army unit deployed to East Africa. During a simulated combat assault (3.5 h, final ambient temperature 27 °C), T c was recorded by radiotelemetry to differentiate volunteers with maximum T c > 38 °C versus ≤ 38 °C. Blood was sampled beforehand and afterwards, for measurement of copeptin, cortisol, free normetanephrine, osmolality and creatinine. RESULTS: There was a significant (P < 0.05) rise in copeptin from pre- to post-assault (10.0 ± 6.3 vs. 16.7 ± 9.6 pmol L-1, P < 0.001). Although osmolality did not increase, copeptin correlated strongly with osmolality after the exposure (r = 0.70, P = 0.004). In volunteers with maximum T c > 38 °C (n = 8) vs ≤ 38 °C (n = 7) there were significantly greater elevations in copeptin (10.4 vs. 2.4 pmol L-1) and creatinine (10 vs. 2 µmol L-1), but no differences in cortisol, free normetanephrine or osmolality. CONCLUSIONS: Changes in copeptin reflected T c response more closely than sympathoadrenal markers or osmolality. Dynamic relationships with tonicity and kidney function may help to explain this finding. As a surrogate for integrated physiological strain during work in a field environment, copeptin assay could inform future measures to prevent heat-related illnesses.
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Glicopéptidos/sangre , Trastornos de Estrés por Calor/sangre , Adulto , Creatinina/sangre , Ejercicio Físico , Trastornos de Estrés por Calor/fisiopatología , Respuesta al Choque Térmico , Humanos , Hidrocortisona/sangre , Masculino , Personal Militar , Normetanefrina/sangre , Concentración OsmolarRESUMEN
The high stress fracture occurrence in military populations has been associated with frequent load carriage activities. This study aimed to assess the influence of load carriage and of completing a load carriage training activity on gait characteristics. Thirty-two Royal Marine recruits completed a 12.8-km load carriage activity as part of their military training. Data were collected during walking in military boots, pre and post-activity, with and without the additional load (35.5 kg). Ground contact time, lower limb sagittal plane kinematics and kinetics, and electromyographic variables were obtained for each condition. When carrying load, there was increased ground contact time, increased joint flexion and joint moments, and increased plantar flexor and knee extensor muscle activity. Post-activity, there were no changes to kinematic variables, knee extensor moments were reduced, and there was evidence of plantar flexor muscle fatigue. The observed gait changes may be associated with stress fracture development. Practitioner Summary: This study identified gait changes due to load carriage and after a military load carriage training activity. Such activities are associated with lower limb stress fractures. A pre-post study design was used. Gait mechanics changed to a greater extent when carrying load, than after completion of the activity when assessed without load.
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Marcha/fisiología , Elevación , Extremidad Inferior/fisiología , Personal Militar , Músculo Esquelético/fisiología , Adulto , Articulación del Tobillo/fisiología , Fenómenos Biomecánicos , Electromiografía , Humanos , Articulación de la Rodilla/fisiología , Masculino , Reino Unido , Soporte de Peso , Adulto JovenRESUMEN
BACKGROUND: Tibial stress fractures (TSFs) cause a significant burden to Royal Marines recruits. No prospective running gait analyses have previously been performed in military settings. AIM: We aimed to identify biomechanical gait factors and anthropometric variables associated with increased risk of TSF. METHODS: 1065 Royal Marines recruits were assessed in week 2 of training. Bilateral plantar pressure and three-dimensional lower limb kinematics were obtained for barefoot running at 3.6â m/s, providing dynamic arch index, peak heel pressure and lower limb joint angles. Age, bimalleolar breadth, calf girth, passive hip internal/external range of motion and body mass index (BMI) were also recorded. 10 recruits who sustained a TSF during training were compared with 120 recruits who completed training injury-free using a binary logistic regression model to identify injury risk factors. RESULTS: 4 variables significantly (p<0.05) predicted increased risk of TSF (ORs and 95% CI): smaller bimalleolar width (0.73, 0.58 to 0.93), lower BMI (0.56, 0.33 to 0.95), greater peak heel pressure (1.25, 1.07 to 1.46) and lower range of tibial rotation (0.78, 0.63 to 0.96). SUMMARY: Reduced impact attenuation and ability to withstand load were implicated in tibial stress fracture risk.
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Fracturas por Estrés/diagnóstico , Carrera/lesiones , Fracturas de la Tibia/diagnóstico , Adolescente , Antropometría , Fenómenos Biomecánicos , Marcha , Humanos , Modelos Logísticos , Masculino , Personal Militar , Presión , Estudios Prospectivos , Rango del Movimiento Articular , Factores de Riesgo , Soporte de Peso , Adulto JovenRESUMEN
Understanding the nutritional demands on serving military personnel is critical to inform training schedules and dietary provision. Troops deployed to Afghanistan face austere living and working environments. Observations from the military and those reported in the British and US media indicated possible physical degradation of personnel deployed to Afghanistan. Therefore, the present study aimed to investigate the changes in body composition and nutritional status of military personnel deployed to Afghanistan and how these were related to physical fitness. In a cohort of British Royal Marines (n 249) deployed to Afghanistan for 6 months, body size and body composition were estimated from body mass, height, girth and skinfold measurements. Energy intake (EI) was estimated from food diaries and energy expenditure measured using the doubly labelled water method in a representative subgroup. Strength and aerobic fitness were assessed. The mean body mass of volunteers decreased over the first half of the deployment ( - 4·6 (sd 3·7) %), predominately reflecting fat loss. Body mass partially recovered (mean +2·2 (sd 2·9) %) between the mid- and post-deployment periods (P< 0·05). Daily EI (mean 10 590 (sd 3339) kJ) was significantly lower than the estimated daily energy expenditure (mean 15 167 (sd 1883) kJ) measured in a subgroup of volunteers. However, despite the body mass loss, aerobic fitness and strength were well maintained. Nutritional provision for British military personnel in Afghanistan appeared sufficient to maintain physical capability and micronutrient status, but providing appropriate nutrition in harsh operational environments must remain a priority.
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Composición Corporal , Metabolismo Energético , Personal Militar , Estado Nutricional , Aptitud Física , Adulto , Afganistán , Estatura , Índice de Masa Corporal , Dieta , Registros de Dieta , Ingestión de Energía , Humanos , Masculino , Micronutrientes/sangre , Grosor de los Pliegues Cutáneos , Reino UnidoRESUMEN
Soldiers must achieve high-level mission-preparedness to endure extended periods of physical and cognitive activity, with unpredictable recovery, in all environments. Nutrition provides the foundation for health and performance. Militaries have not maximised the strategic and financial value that considering nutrition as a military capability could deliver. A whole system approach to military nutrition, based on the prepare-perform-recover human capability cycle phases, is presented. Trainee nutrition requirements, through to very-high-readiness forces undertaking arduous roles at reach, must be specifically addressed. Promoting military performance diets in the prepare phase, through practitioner-supported nutrition education and food provision, will ensure mission readiness and mitigate ill health. Delivering nutrition in field settings in the perform phase-through smaller/lighter, nutritionally optimised rations and smart packaging technologies-will improve utility and minimise waste. Strategic dietary supplement use can provide a mission performance-enhancing adjunct to a food-first philosophy. Impact value chain analysis of military nutrition capability investments could support cost-benefit measurement.
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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 (nâ=â11) identified 13 physically demanding and critical role-related tasks. The subsequent survey (nâ=â907) 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.
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Empleo , Análisis y Desempeño de Tareas , Humanos , Examen Físico , Policia , Tomografía Computarizada por Rayos X , Aptitud FísicaRESUMEN
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.
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Personal Militar , Humanos , Adulto Joven , Adulto , Aptitud Física , Análisis y Desempeño de Tareas , Fuerza Muscular , EmpleoRESUMEN
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.
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Personal Militar , Dieta , Humanos , Nutrientes , Necesidades Nutricionales , Estado NutricionalRESUMEN
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.
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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 (0.3â gâ kgâ 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 ± 0.63â ngâ ml-1; PLA Δ = 0.92 ± 0.44â ngâ ml-1). GI MT (Bacteroides/total 16S DNA ratio) was unchanged in either condition following the EHST (p = 0.43).Conclusion: Acute low-dose (0.3â gâ 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; VÌO2max: 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 (0.9â gâ kgâ 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 (0.30â gâ kgâ FFM-1; â¼20 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.
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Trastornos de Estrés por Calor , Golpe de Calor , Humanos , Masculino , Suplementos Dietéticos , Glutamina , Respuesta al Choque Térmico , Lactatos , Permeabilidad , Poliésteres , AzúcaresRESUMEN
Effects of a carbohydrate beverage on the physiological responses to load carriage were examined. Ten fit male participants (age: 28 ± 9 years, body mass: 81.5 ± 10.5 kg, VO(2max): 55.0 ± 5.5 mL kg(-1) min(-1)) completed two test conditions in random order, walking on a treadmill (6.5 km h(-1)) for 120 min, carrying a 25-kg backpack. At 0 and 60 min of exercise participants consumed 250 mL of a placebo (flavoured water) (PLA) or 6.4% carbohydrate (CHO) beverage. There were no differences in VO(2,) respiratory exchange ratio (RER), heart rate or EMG activity of m. rectus femoris, m. vastus lateralis, m. semitendinosus and m. biceps femoris between conditions at minute 5 of exercise. The increase in VO(2) between minutes 5 and 120 was less during CHO than PLA (8 ± 5 vs. 14 ± 6%, P = 0.036). RER decreased during PLA, from 0.96 ± 0.05 at minute 5 to 0.87 ± 0.04 at minute 120 (P < 0.001), but not during CHO (P = 0.056). Heart rate increased between minutes 5 and 120 during PLA (16 ± 10%, P < 0.001) and CHO (12 ± 6%, P < 0.001), with no difference between conditions (P = 0.251). EMG peak RMS did not change between minutes 7 and 107 during PLA or CHO for the leg muscles. However, individual responses in EMG were highly variable (i.e. both increases and decreases in RMS). It was concluded that carbohydrate intake during load carriage reduced the VO(2) drift, which could be partially attributed to higher carbohydrate oxidation rates. Despite muscle fatigue/damage previously being identified as a cause of VO(2) drift, it appears that carbohydrate had no effect on neuromuscular responses during load carriage.
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Bebidas , Carbohidratos de la Dieta/farmacología , Prueba de Esfuerzo/efectos de los fármacos , Ejercicio Físico/fisiología , Caminata/fisiología , Adulto , Prueba de Esfuerzo/métodos , Humanos , Masculino , Fatiga Muscular/efectos de los fármacos , Esfuerzo Físico/efectos de los fármacos , Placebos , Intercambio Gaseoso Pulmonar/efectos de los fármacos , Intercambio Gaseoso Pulmonar/fisiología , Factores de Tiempo , Soporte de Peso/fisiología , Adulto JovenRESUMEN
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.
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Personal Militar , Infecciones Estafilocócicas , Humanos , Epidemiología Molecular , Filogenia , Estudios Prospectivos , Infecciones Estafilocócicas/epidemiología , Staphylococcus , Staphylococcus aureus/genéticaRESUMEN
INTRODUCTION: Decrements in muscle function may reduce physical and skilled performance and have been shown to be greater following walking unloaded on negative gradients. We examined the effects of prolonged walking with load carriage at level and negative gradients on muscle function. METHODS: There were 10 male participants who completed two bouts of load carriage carrying a 25-kg backpack for 2 h at 6.5 km x h(-1) during level walking (LW) and downhill (-8% gradient) walking (DW). Force produced during voluntary and electrically stimulated contractions was measured before, 0, 24, 48, and 72 h post-exercise. RESULTS: Isometric knee extension force decreased immediately after LW (15 +/- 11%) and DW (16 +/- 17%) and recovered to baseline at 72 h. Voluntary activation decreased immediately after LW (95 +/- 5 to 91 +/- 10%) and DW (97 +/- 4 to 94 +/- 12%) and returned to baseline at 24 h. Electrically stimulated 20:50 Hz tetani decreased after LW and DW, with complete recovery by 24 h after DW only. LW and DW caused decreases immediately after exercise in isokinetic peak torque of knee extensors and flexors at 60 degrees x s(-1) and 180 degrees x s(-1), trunk extensors and flexors at 15 degrees x s(-1), and shoulder flexors at 60 degrees x s(-1), with complete recovery at different time points, but all by 72 h. CONCLUSIONS: Level and downhill treadmill walking with load carriage resulted in similar changes in muscle function of the lower and upper body muscles immediately after exercise and during recovery. The decrements in muscle function may increase the risk of musculoskeletal injury and is likely to impair performance during physical and skilled tasks following load carriage.
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Contracción Isométrica/fisiología , Fatiga Muscular/fisiología , Caminata/fisiología , Adulto , Fenómenos Biomecánicos/fisiología , Estudios Cruzados , Humanos , Rodilla/fisiología , Elevación , Masculino , Hombro/fisiología , Torque , Adulto JovenRESUMEN
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.