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Ogden HB, Rawcliffe AJ, Delves SK, Roberts A. Are young military personnel at a disproportional risk of heat illness? BMJ Mil Health 2023; 169:559-564. [PMID: 35241622 PMCID: PMC10715519 DOI: 10.1136/bmjmilitary-2021-002053] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 01/08/2022] [Indexed: 11/04/2022]
Abstract
Heat illnesses (HI) define a continuum of conditions where patients become incapacitated due to uncompensable heat stress. In the military, HI has a significant health, financial and operational burden that requires vigilant management. Military training and operations regularly expose personnel to known HI risk factors, meaning that prevalence remains high despite stringent attempts to reduce risk to as low as reasonably practicable. While prepubertal children and elderly adults are widely demonstrated to be at greater risk of classic HI than young adults due to impaired physiological and/or behavioural thermoregulation, in military personnel, it is young recruit-age individuals (16-19 years) who consistently experience the highest prevalence of exertional HI. Mechanistically, controlled laboratory studies have never directly compared thermoregulation between young recruit-age individuals and other groups of adults, though research highlighting impaired thermoregulation in prepubertal children potentially has some relevance to late-developing young recruit-age personnel. Aside from potential age-related differences in thermoregulation, a major consideration must also be given to the increased prevalence of organisational risk factors for HI in younger military personnel (eg, education, physical load, rank, job roles), which is likely to be the primary explanation behind age-related trends in HI prevalence, at least in the military. The aims of this article are to review: (i) the epidemiology of HI between young recruit-age individuals and older military personnel; (ii) the theoretical basis for age-associated differences in thermoregulatory function and (iii) pertinent areas for future research.
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Affiliation(s)
- Henry B Ogden
- Army Recruit Health and Performance Research, UK Ministry of Defence, Upavon, Wiltshire, UK
| | - A J Rawcliffe
- Army Recruit Health and Performance Research, UK Ministry of Defence, Upavon, Wiltshire, UK
| | - S K Delves
- Environmental Medicine and Science, Institute of Naval Medicine, Gosport, UK
| | - A Roberts
- Army Recruit Health and Performance Research, UK Ministry of Defence, Upavon, Wiltshire, UK
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Chang L, Gardner L, House C, Daly C, Allsopp A, Roiz de Sa D, Shaw MA, Hopkins PM. Comparison of Transcriptomic Changes in Survivors of Exertional Heat Illness with Malignant Hyperthermia Susceptible Patients. Int J Mol Sci 2023; 24:16124. [PMID: 38003313 PMCID: PMC10671540 DOI: 10.3390/ijms242216124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 11/02/2023] [Accepted: 11/07/2023] [Indexed: 11/26/2023] Open
Abstract
Exertional heat illness (EHI) is an occupational health hazard for athletes and military personnel-characterised by the inability to thermoregulate during exercise. The ability to thermoregulate can be studied using a standardised heat tolerance test (HTT) developed by The Institute of Naval Medicine. In this study, we investigated whole blood gene expression (at baseline, 2 h post-HTT and 24 h post-HTT) in male subjects with either a history of EHI or known susceptibility to malignant hyperthermia (MHS): a pharmacogenetic condition with similar clinical phenotype. Compared to healthy controls at baseline, 291 genes were differentially expressed in the EHI cohort, with functional enrichment in inflammatory response genes (up to a four-fold increase). In contrast, the MHS cohort featured 1019 differentially expressed genes with significant down-regulation of genes associated with oxidative phosphorylation (OXPHOS). A number of differentially expressed genes in the inflammation and OXPHOS pathways overlapped between the EHI and MHS subjects, indicating a common underlying pathophysiology. Transcriptome profiles between subjects who passed and failed the HTT (based on whether they achieved a plateau in core temperature or not, respectively) were not discernable at baseline, and HTT was shown to elevate inflammatory response gene expression across all clinical phenotypes.
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Affiliation(s)
- Leon Chang
- Leeds Institute of Medical Research at St James’s, University of Leeds, Leeds LS9 7TF, UK; (L.C.); (M.-A.S.)
| | - Lois Gardner
- Leeds Institute of Medical Research at St James’s, University of Leeds, Leeds LS9 7TF, UK; (L.C.); (M.-A.S.)
| | - Carol House
- Survival and Thermal Medicine Department, Institute of Naval Medicine, Alverstoke, Hampshire PO12 2DL, UK
| | - Catherine Daly
- Malignant Hyperthermia Unit, St James’s University Hospital, Leeds LS9 7TF, UK;
| | - Adrian Allsopp
- Survival and Thermal Medicine Department, Institute of Naval Medicine, Alverstoke, Hampshire PO12 2DL, UK
| | - Daniel Roiz de Sa
- Survival and Thermal Medicine Department, Institute of Naval Medicine, Alverstoke, Hampshire PO12 2DL, UK
| | - Marie-Anne Shaw
- Leeds Institute of Medical Research at St James’s, University of Leeds, Leeds LS9 7TF, UK; (L.C.); (M.-A.S.)
| | - Philip M. Hopkins
- Leeds Institute of Medical Research at St James’s, University of Leeds, Leeds LS9 7TF, UK; (L.C.); (M.-A.S.)
- Malignant Hyperthermia Unit, St James’s University Hospital, Leeds LS9 7TF, UK;
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House C, Stacey M, Woods D, Allsopp A, Roiz de Sa D. Procedure for assessing patients referred to the UK's military Heat Illness Clinic: a case series. BMJ Mil Health 2023; 169:310-315. [PMID: 34266969 DOI: 10.1136/bmjmilitary-2021-001875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 07/03/2021] [Indexed: 11/04/2022]
Abstract
INTRODUCTION The UK military operates a Heat Illness Clinic (HIC) to aid the return to exercise, training and occupational duty recommendations for individuals who have suffered exertional heat illness or heatstroke. This paper describes the process of assessment and reports representative data from n=22 patients referred to the HIC. METHOD The assessment included clinical consultation, and measurement of maximal oxygen consumption (V̇O2max) and a heat tolerance test (HTT) conducted on a treadmill in an environmental chamber with an air temperature of 34°C and 44% relative humidity. Patients began the HTT wearing military clothing, carrying a rucksack (mass 15 kg) and walking at 60% V̇O2max, at 30 min the rucksack and jacket were removed and the T-shirt at 45 min, individuals continued walking for 60-90 min. Patients were considered heat tolerant if rectal temperature achieved a plateau. RESULTS N=14 patients were heat tolerant on the first assessment and of the n=8 patients required to return for repeat assessment, five were heat tolerant on the second assessment and the remaining three on the third assessment. CONCLUSIONS In conjunction with patient history and clinical evaluation, the HTT provides a physiological basis to assist with decisions concerning patient management and return to duty following an episode of heat illness.
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Affiliation(s)
- Carol House
- Institute of Naval Medicine, Gosport, UK
- School of Health and Exercise Science, University of Portsmouth, Portsmouth, UK
| | - M Stacey
- Department of Surgery and Cancer, Imperial College, London, UK
- Research and Clinical Innovation, Royal Centre for Defence Medicine, Birmingham, UK
| | - D Woods
- Research and Clinical Innovation, Royal Centre for Defence Medicine, Birmingham, UK
- Institute for Sport, Physical Activity and Leisure, Carnegie School of Sport, Leeds Beckett University, Leeds, UK
- Northumbria NHS Foundation Trust, Newcastle-upon-Tyne, UK
| | - A Allsopp
- Institute of Naval Medicine, Gosport, UK
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Gifford RM, Taylor N, Stacey M, Woods DR. Sex, gender or occupational psychology: what matters most to preventing heat-related illnesses and improving outcomes for women in ground close combat? BMJ Mil Health 2023; 169:75-77. [PMID: 32345677 DOI: 10.1136/bmjmilitary-2020-001480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 04/05/2020] [Accepted: 04/06/2020] [Indexed: 01/27/2023]
Abstract
Since the advent of women in ground close combat (WGCC) roles, the impact on women of the attendant risk of heat stress and heat illness has been considered. Much emphasis has been placed on sex differences in thermal physiology. This article considers the application of evidence of sex-associated thermoregulatory variation to the occupational and environmental setting of WGCC, and weighs the relative importance of physiological differences arising from biological sex, and behaviour associated with gender normatives. Quantifying the risk of heat illness to WGCC should draw on data from their real-world occupational context.
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Affiliation(s)
- Robert M Gifford
- British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK.,Academic Department of Military Medicine, HQ Joint Medical Group, Birmingham, UK
| | - N Taylor
- Academic Department of Military Medicine, HQ Joint Medical Group, Birmingham, UK
| | - M Stacey
- Academic Department of Military Medicine, HQ Joint Medical Group, Birmingham, UK
| | - D R Woods
- Academic Department of Military Medicine, HQ Joint Medical Group, Birmingham, UK.,Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University Carnegie Faculty, Leeds, UK
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Hunt AP, Potter AW, Linnane DM, Xu X, Patterson MJ, Stewart IB. Heat Stress Management in the Military: Wet-Bulb Globe Temperature Offsets for Modern Body Armor Systems. HUMAN FACTORS 2022; 64:1306-1316. [PMID: 33861157 DOI: 10.1177/00187208211005220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
OBJECTIVE The aim of this study was to model the effect of body armor coverage on body core temperature elevation and wet-bulb globe temperature (WBGT) offset. BACKGROUND Heat stress is a critical factor influencing the health and safety of military populations. Work duration limits can be imposed to mitigate the risk of exertional heat illness and are derived based on the environmental conditions (WBGT). Traditionally a 3°C offset to WBGT is recommended when wearing body armor; however, modern body armor systems provide a range of coverage options, which may influence thermal strain imposed on the wearer. METHOD The biophysical properties of four military clothing ensembles of increasing ballistic protection coverage were measured on a heated sweating manikin in accordance with standard international criteria. Body core temperature elevation during light, moderate, and heavy work was modeled in environmental conditions from 16°C to 34°C WBGT using the heat strain decision aid. RESULTS Increasing ballistic protection resulted in shorter work durations to reach a critical core temperature limit of 38.5°C. Environmental conditions, armor coverage, and work intensity had a significant influence on WBGT offset. CONCLUSION Contrary to the traditional recommendation, the required WBGT offset was >3°C in temperate conditions (<27°C WBGT), particularly for moderate and heavy work. In contrast, a lower WBGT offset could be applied during light work and moderate work in low levels of coverage. APPLICATION Correct WBGT offsets are important for enabling adequate risk management strategies for mitigating risks of exertional heat illness.
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Affiliation(s)
- Andrew P Hunt
- 139261 Queensland University of Technology, Brisbane, Australia
- 111604 Defence Science and Technology Group, Melbourne, VIC, Australia
| | - Adam W Potter
- 20041 U.S. Army Research Institute of Environmental Medicine, Natick, MA, USA
| | - Denise M Linnane
- 111604 Defence Science and Technology Group, Melbourne, VIC, Australia
| | - Xiaojiang Xu
- 20041 U.S. Army Research Institute of Environmental Medicine, Natick, MA, USA
| | - Mark J Patterson
- 111604 Defence Science and Technology Group, Melbourne, VIC, Australia
| | - Ian B Stewart
- 139261 Queensland University of Technology, Brisbane, Australia
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Lewandowski SA, Kioumourtzoglou MA, Shaman JL. Heat stress illness outcomes and annual indices of outdoor heat at U.S. Army installations. PLoS One 2022; 17:e0263803. [PMID: 36417342 PMCID: PMC9683623 DOI: 10.1371/journal.pone.0263803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 10/24/2022] [Indexed: 11/24/2022] Open
Abstract
This study characterized associations between annually scaled thermal indices and annual heat stress illness (HSI) morbidity outcomes, including heat stroke and heat exhaustion, among active-duty soldiers at ten Continental U.S. (CONUS) Army installations from 1991 to 2018. We fit negative binomial models for 3 types of HSI morbidity outcomes and annual indices for temperature, heat index, and wet-bulb globe temperature (WBGT), adjusting for installation-level effects and long-term trends in the negative binomial regression models using block-bootstrap resampling. Ambulatory (out-patient) and reportable event HSI outcomes displayed predominately positive association patterns with the assessed annual indices of heat, whereas hospitalization associations were mostly null. For example, a one-degree Fahrenheit (°F) (or 0.55°C) increase in mean temperature between May and September was associated with a 1.16 (95% confidence interval [CI]: 1.11, 1.29) times greater rate of ambulatory encounters. The annual-scaled rate ratios and their uncertainties may be applied to climate projections for a wide range of thermal indices to estimate future military and civilian HSI burdens and impacts to medical resources.
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Affiliation(s)
- Stephen A. Lewandowski
- Department of Environmental Health Sciences, Columbia University Mailman School of Public Health, New York, New York, United States of America
- Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
- * E-mail:
| | - Marianthi-Anna Kioumourtzoglou
- Department of Environmental Health Sciences, Columbia University Mailman School of Public Health, New York, New York, United States of America
| | - Jeffrey L. Shaman
- Department of Environmental Health Sciences, Columbia University Mailman School of Public Health, New York, New York, United States of America
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Périard JD, DeGroot D, Jay O. Exertional heat stroke in sport and the military: epidemiology and mitigation. Exp Physiol 2022; 107:1111-1121. [PMID: 36039024 PMCID: PMC9826288 DOI: 10.1113/ep090686] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 08/12/2022] [Indexed: 01/11/2023]
Abstract
NEW FINDINGS What is the topic of this review? Exertional heat stroke epidemiology in sport and military settings, along with common risk factors and strategies and policies designed to mitigate its occurrence. What advances does it highlight? Individual susceptibility to exertional heat stroke risk is dependent on the interaction of intrinsic and extrinsic factors. Heat policies in sport should assess environmental conditions, as well as the characteristics of the athlete, clothing/equipment worn and activity level of the sport. Exertional heat stroke risk reduction in the military should account for factors specific to training and personnel. ABSTRACT Exertional heat illness occurs along a continuum, developing from the relatively mild condition of muscle cramps, to heat exhaustion, and in some cases to the life-threatening condition of heat stroke. The development of exertional heat stroke (EHS) is associated with an increase in core temperature stemming from inadequate heat dissipation to offset the rate of metabolically generated heat. Susceptibility to EHS is linked to the interaction of several factors including environmental conditions, individual characteristics, health conditions, medication and drug use, behavioural responses, and sport/organisational requirements. Two settings in which EHS is commonly observed are competitive sport and the military. In sport, the exact prevalence of EHS is unclear due to inconsistent exertional heat illness terminology, diagnostic criteria and data reporting. In contrast, exertional heat illness surveillance in the military is facilitated by standardised case definitions, a requirement to report all heat illness cases and a centralised medical record repository. To mitigate EHS risk, several strategies can be implemented by athletes and military personnel, including heat acclimation, ensuring adequate hydration, cold-water immersion and mandated work-to-rest ratios. Organisations may also consider developing sport or military task-specific heat stress policies that account for the evaporative heat loss requirement of participants, relative to the evaporative capacity of the environment. This review examines the epidemiology of EHS along with the strategies and policies designed to reduce its occurrence in sport and military settings. We highlight the nuances of identifying individuals at risk of EHS and summarise the benefits and shortcomings of various mitigation strategies.
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Affiliation(s)
- Julien D. Périard
- Research Institute for Sport and ExerciseUniversity of CanberraCanberraAustralia
| | - David DeGroot
- Army Heat CenterMartin Army Community HospitalFort BenningGAUSA
| | - Ollie Jay
- Thermal Ergonomics LaboratoryHeat and Health Research IncubatorFaculty of Medicine and HealthUniversity of SydneyCamperdownAustralia
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Lewandowski SA, Shaman JL. Heat stress morbidity among US military personnel: Daily exposure and lagged response (1998-2019). INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2022; 66:1199-1208. [PMID: 35292853 DOI: 10.1007/s00484-022-02269-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 03/03/2022] [Accepted: 03/04/2022] [Indexed: 06/14/2023]
Abstract
Heat stress illnesses represent a rising public health threat; however, associations between environmental heat and observed adverse health outcomes across populations and geographies remain insufficiently elucidated to evaluate risk and develop prevention strategies. In particular, military-relevant large-scale studies of daily heat stress morbidity responses among physically active, working-age adults to various indices of heat have been limited. We evaluated daily means, maximums, minimums, and early morning measures of temperature, heat index, and wet bulb globe temperature (WBGT) indices, assessing their association with 31,642 case-definition heat stroke and heat exhaustion encounters among active duty servicemembers diagnosed at 24 continental US installations from 1998 to 2019. We utilized anonymized encounter data consisting of hospitalizations, ambulatory (out-patient) visits, and reportable events to define heat stress illness cases and select the 24 installations with the highest case counts. We derived daily indices of heat from hourly-scale gridded climate data and applied a case-crossover study design incorporating distributed-lag, nonlinear models with 5 days of lag to estimate odds ratios at one-degree increments for each index of heat. All indices exhibited nonlinear odds ratios with short-term lag effects throughout observed temperature ranges. Responses were positive, monotonic, and exponential in nature, except for maximum daily WBGT, minimum daily temperature, temperature at 0600 h (local), and WBGT at 0600 h (local), which, while generally increasing, showed decreasing risk for the highest heat category days. The risk for a heat stress illness on a day with a maximum WBGT of 32.2 °C (90.0 °F) was 1.93 (95% CI, 1.82 - 2.05) times greater than on a day with a maximum WBGT of 28.6 °C (83.4 °F). The risk was 2.53 (2.36-2.71) times greater on days with a maximum heat index of 40.6 °C (105 °F) compared to 32.8 °C (91.0 °F). Our findings suggest that prevention efforts may benefit from including prior-day heat levels in risk assessments, from monitoring temperature and heat index in addition to WBGT, and by promoting control measures and awareness across all heat categories.
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Affiliation(s)
- Stephen A Lewandowski
- Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD, 20814, USA.
- Department of Environmental Health Sciences, Columbia University Mailman School of Public Health, 722 West 168th St., New York, NY, 10032, USA.
| | - Jeffrey L Shaman
- Department of Environmental Health Sciences, Columbia University Mailman School of Public Health, 722 West 168th St., New York, NY, 10032, USA
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Weiner CM, Kazman JB, Abraham PA, Deuster PA. Perceptual strain in a compensable hot environment: Accuracy and clinical correlates. J Therm Biol 2021; 100:102863. [PMID: 34503767 DOI: 10.1016/j.jtherbio.2021.102863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 01/19/2021] [Accepted: 01/22/2021] [Indexed: 10/22/2022]
Abstract
Heat strain monitoring indexes are important to prevent exertional heat illness (EHI) and uncover risk factors. Two indexes are the Physiological Strain Index (PSI) and a subjective PSI analogue, the Perceptual Strain Index (PeSI). The PeSI is a feasible alternative to PSI in field conditions, although the validity has been variable in previous research. However, the PeSI has been rarely examined at a low heat strain with compensable heat stress, such as during a heat tolerance test (HTT). This study evaluated the discrepancy between the maximal PeSI and maximal PSI achieved during a HTT and determined their association with EHI risk factors, including history of EHI, percent body fat (%BF), relative VO2max, fatigue and sleep status (n = 121; 47 without prior EHI, 74 with prior EHI). The PSI was calculated using the change in rectal temperature (Tre) and heart rate (HR) and PeSI was calculated based on the formula containing thermal sensation (TS), a Tre analogue, and rate of perceived exertion (RPE), a HR analogue. Significant associations were identified between PSI and PeSI and between PSIHR and PeSIHR in the total sample and between PSI and PeSI in the EHI group. Bland-Altman analyses indicated PeSI underestimated PSI in the total sample, PSIHR was greater than PeSIHR, and that PSIcore and PeSIcore were not significantly different, but values varied widely at different heat strains. This indicates the use of RPE underestimates HR and that the accuracy of TS to predict Tre may be subpar. This study also demonstrated that participants with higher %BF have a decreased perception of heat strain and that post-fatigue, sleep status and a prior EHI may increase the perception of heat strain. Overall, these results suggest that PeSI is a poor surrogate for PSI in a compensable heat stress environment at low heat strain.
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Affiliation(s)
- Cynthia M Weiner
- Consortium for Health and Military Performance, Department of Military & Emergency Medicine, F. Edward Hébert School of Medicine, Uniformed Services University, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, USA
| | - Josh B Kazman
- Consortium for Health and Military Performance, Department of Military & Emergency Medicine, F. Edward Hébert School of Medicine, Uniformed Services University, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, USA.
| | - Preetha A Abraham
- Consortium for Health and Military Performance, Department of Military & Emergency Medicine, F. Edward Hébert School of Medicine, Uniformed Services University, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, USA
| | - Patricia A Deuster
- Consortium for Health and Military Performance, Department of Military & Emergency Medicine, F. Edward Hébert School of Medicine, Uniformed Services University, USA
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Parsons IT, Gifford RM, Stacey MJ, Lamb LE, O'Shea MK, Woods DR. Does vitamin D supplementation prevent SARS-CoV-2 infection in military personnel? Review of the evidence. BMJ Mil Health 2021; 167:280-286. [PMID: 33504571 PMCID: PMC7843210 DOI: 10.1136/bmjmilitary-2020-001686] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 11/15/2020] [Accepted: 11/21/2020] [Indexed: 01/19/2023]
Abstract
For most individuals residing in Northwestern Europe, maintaining replete vitamin D status throughout the year is unlikely without vitamin D supplementation and deficiency remains common. Military studies have investigated the association with vitamin D status, and subsequent supplementation, with the risk of stress fractures particularly during recruit training. The expression of nuclear vitamin D receptors and vitamin D metabolic enzymes in immune cells additionally provides a rationale for the potential role of vitamin D in maintaining immune homeostasis. One particular area of interest has been in the prevention of acute respiratory tract infections (ARTIs). The aims of this review were to consider the evidence of vitamin D supplementation in military populations in the prevention of ARTIs, including SARS-CoV-2 infection and consequent COVID-19 illness. The occupational/organisational importance of reducing transmission of SARS-CoV-2, especially where infected young adults may be asymptomatic, presymptomatic or paucisymptomatic, is also discussed.
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Affiliation(s)
- Iain T Parsons
- Academic Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK
- School of Cardiovascular Medicine and Life Sciences, King's College London, London, UK
| | - R M Gifford
- Academic Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK
- British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, Midlothian, UK
| | - M J Stacey
- Academic Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK
| | - L E Lamb
- Academic Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK
| | - M K O'Shea
- Academic Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK
| | - D R Woods
- Academic Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK
- Carnegie School of Sport, Leeds Beckett University, Leeds, UK
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11
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Field validation of The Heat Strain Decision Aid during military load carriage. Comput Biol Med 2021; 134:104506. [PMID: 34090016 DOI: 10.1016/j.compbiomed.2021.104506] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 05/07/2021] [Accepted: 05/15/2021] [Indexed: 11/22/2022]
Abstract
OBJECTIVES We aimed to determine the agreement between actual and predicted core body temperature, using the Heat Strain Decision Aid (HSDA), in non-Ground Close Combat (GCC) personnel wearing multi terrain pattern clothing during two stages of load carriage in temperate conditions. DESIGN Cross-sectional. METHODS Sixty participants (men = 49, women = 11, age 31 ± 8 years; height 171.1 ± 9.0 cm; body mass 78.1 ± 11.5 kg) completed two stages of load carriage, of increasing metabolic rate, as part of the development of new British Army physical employment standards (PES). An ingestible gastrointestinal sensor was used to measure core temperature. Testing was completed in wet bulb globe temperature conditions; 1.2-12.6 °C. Predictive accuracy and precision were analysed using individual and group mean inputs. Assessments were evaluated by bias, limits of agreement (LoA), mean absolute error (MAE), and root mean square error (RMSE). Accuracy was evaluated using a prediction bias of ±0.27 °C and by comparing predictions to the standard deviation of the actual core temperature. RESULTS Modelling individual predictions provided an acceptable level of accuracy based on bias criterion; where the total of all trials bias ± LoA was 0.08 ± 0.82 °C. Predicted values were in close agreement with the actual data: MAE 0.37 °C and RMSE 0.46 °C for the collective data. Modelling using group mean inputs were less accurate than using individual inputs, but within the mean observed. CONCLUSION The HSDA acceptably predicts core temperature during load carriage to the new British Army non-GCC PES, in temperate conditions.
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12
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Ashworth ET, Cotter JD, Kilding AE. Methods for improving thermal tolerance in military personnel prior to deployment. Mil Med Res 2020; 7:58. [PMID: 33248459 PMCID: PMC7700709 DOI: 10.1186/s40779-020-00287-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 11/10/2020] [Indexed: 12/16/2022] Open
Abstract
Acute exposure to heat, such as that experienced by people arriving into a hotter or more humid environment, can compromise physical and cognitive performance as well as health. In military contexts heat stress is exacerbated by the combination of protective clothing, carried loads, and unique activity profiles, making them susceptible to heat illnesses. As the operational environment is dynamic and unpredictable, strategies to minimize the effects of heat should be planned and conducted prior to deployment. This review explores how heat acclimation (HA) prior to deployment may attenuate the effects of heat by initiating physiological and behavioural adaptations to more efficiently and effectively protect thermal homeostasis, thereby improving performance and reducing heat illness risk. HA usually requires access to heat chamber facilities and takes weeks to conduct, which can often make it impractical and infeasible, especially if there are other training requirements and expectations. Recent research in athletic populations has produced protocols that are more feasible and accessible by reducing the time taken to induce adaptations, as well as exploring new methods such as passive HA. These protocols use shorter HA periods or minimise additional training requirements respectively, while still invoking key physiological adaptations, such as lowered core temperature, reduced heart rate and increased sweat rate at a given intensity. For deployments of special units at short notice (< 1 day) it might be optimal to use heat re-acclimation to maintain an elevated baseline of heat tolerance for long periods in anticipation of such an event. Methods practical for military groups are yet to be fully understood, therefore further investigation into the effectiveness of HA methods is required to establish the most effective and feasible approach to implement them within military groups.
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Affiliation(s)
- Edward Tom Ashworth
- Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, 17 Antares Place, Rosedale, Auckland, 0632 New Zealand
| | - James David Cotter
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, Otago 9016 New Zealand
| | - Andrew Edward Kilding
- Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, 17 Antares Place, Rosedale, Auckland, 0632 New Zealand
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13
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Marlega J, Mickiewicz A, Fijalkowska J, Gruchala M, Fijalkowski M. Exertional heat stroke in an amateur runner – Challenges in diagnostics and the role of unhealthy competition. J Sports Sci 2020; 38:2597-2602. [DOI: 10.1080/02640414.2020.1794256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Joanna Marlega
- Department of Cardiology I, Medical University of Gdansk, Gdansk, Poland
| | | | | | - Marcin Gruchala
- Department of Cardiology I, Medical University of Gdansk, Gdansk, Poland
| | - Marcin Fijalkowski
- Department of Cardiology I, Medical University of Gdansk, Gdansk, Poland
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14
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Alele FO, Malau-Aduli BS, Malau-Aduli AEO, J. Crowe M. Epidemiology of Exertional Heat Illness in the Military: A Systematic Review of Observational Studies. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:E7037. [PMID: 32993024 PMCID: PMC7579124 DOI: 10.3390/ijerph17197037] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 09/22/2020] [Accepted: 09/23/2020] [Indexed: 12/13/2022]
Abstract
Exertional heat illness (EHI) is an occupational hazard among military personnel. This systematic review describes the incidence, risk factors, clinical manifestations, and biomarkers of EHI in the military. Six databases from inception to 28 May 2020 were systematically reviewed using the PRISMA guidelines. Forty-one articles met the inclusion criteria and the incidence of EHI ranged from 0.2 to 10.5 per 1000 person years, while the prevalence rates ranged from 0.3% to 9.3%. Intrinsic risk factors influencing EHI were gender, physical fitness, obesity, previous history of heat illness, and motivation, while the extrinsic factors included hot environmental conditions and service unit. Evidence suggests that loss of consciousness, absence of sweating and confusion were the common clinical features of exertional heat stroke (EHS). The mean core temperature ranged from 40 to 41.6 °C, while elevated levels of creatine phosphokinase, liver enzymes, and creatinine were common biochemical markers of EHS. The findings of the review suggest a variation in the incidence of EHI among military populations possibly due to the varying definitions used. Although some risk factors of EHI were identified, more analytical studies are needed to investigate the association between EHI and other important factors such as acclimatisation and occlusive clothing.
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Affiliation(s)
- Faith O. Alele
- College of Healthcare Sciences, James Cook University, Townsville QLD 4811, Australia
| | - Bunmi S. Malau-Aduli
- College of Medicine and Dentistry, James Cook University, Townsville QLD 4811, Australia;
| | - Aduli E. O. Malau-Aduli
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville QLD 4811, Australia;
| | - Melissa J. Crowe
- Division of Tropical Health and Medicine, James Cook University, Townsville QLD 4811, Australia;
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15
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Influence of aerobic fitness on gastrointestinal barrier integrity and microbial translocation following a fixed-intensity military exertional heat stress test. Eur J Appl Physiol 2020; 120:2325-2337. [PMID: 32794058 DOI: 10.1007/s00421-020-04455-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 07/30/2020] [Indexed: 02/06/2023]
Abstract
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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16
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Smith MB, White S. Command application of UK military climatic guidance on Exercise SAIF SAREEA 3. BMJ Mil Health 2020; 166:418-420. [PMID: 32474438 DOI: 10.1136/bmjmilitary-2019-001358] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 05/01/2020] [Accepted: 05/06/2020] [Indexed: 11/04/2022]
Abstract
Health and risk management of personnel in hot climates remains a Commander's responsibility, with Joint Service Publication 539 Heat Illness and Cold Injury: Prevention and Management (JSP 539) being the guiding document for the UK military. This policy can be challenging to interpret occasionally, needing medical professionals to provide ongoing advice to commanders. This is to achieve a shared understanding of scientific concepts and risks to allow a more informed decision-making by commanders. This then leads to the appropriate mitigation of risks to as low as reasonably practical. Exercise SAIF SAREEA 3 saw commanders and medical cooperation at all levels with a practical and pragmatic application of the principles articulated in joint policy. The elements which saw enhanced cooperation included pathophysiology, work rates and work:rest ratios, rest and sleep periods, uniform, acclimatisation, and hydration and electrolyte balance. This approach was exhibited throughout the planning, deployment and execution of Exercise SAIF SAREEA 3, which saw extremely low levels of heat injury throughout the exercise when compared with SAIF SAREEA 2 and related exercises. This personal view aims to describe the command and medical interaction on SAIF SAREEA 3 which the authors feel contributed to those successes against climatic effects.
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Affiliation(s)
- M B Smith
- 5 Armoured Medical Regiment, British Army, Catterick, UK
| | - S White
- Department of Military Medicine, Royal Centre for Defence Medicine, Queen Elizabeth Hospital Birmingham, Birmingham, UK
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17
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Taylor N, Stacey MJ, Smith M, Woods D. Exertional heat illness in the military: a voice from the past with lessons for the present. BMJ Mil Health 2020; 166:285-286. [PMID: 32409617 DOI: 10.1136/bmjmilitary-2020-001457] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/31/2020] [Indexed: 11/04/2022]
Affiliation(s)
- Natalie Taylor
- Academic Department of Military General Practice, Royal Centre for Defence Medicine, Birmingham, UK
| | - M J Stacey
- Academic Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK .,Department of Surgery and Cancer, Imperial College London, London, UK
| | - M Smith
- Academic Department of Military General Practice, Royal Centre for Defence Medicine, Birmingham, UK
| | - D Woods
- Academic Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK.,Carnegie Research Institute, Leeds Beckett University, Leeds, West Yorkshire, UK
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18
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Harper PN, Taylor N, Royal P, Smith MB. Role of the pre-hospital treatment team on the UK military exercise SAIF SAREEA 3. BMJ Mil Health 2020; 166:421-424. [DOI: 10.1136/bmjmilitary-2019-001366] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 04/02/2020] [Accepted: 04/02/2020] [Indexed: 11/04/2022]
Abstract
The prehospital treatment team (PHTT) involves a small team working under the clinical supervision of a clinical lead. The clinical lead can be a general duties medical officer (Post Foundation Years Doctor), military nurse practitioner or more senior clinician. The team is mounted in vehicles appropriate to the environment they expect to operate in. A PHTT is closely located to the front line reducing transportation timelines from the point of wounding to more definitive care. The PHTT can provide medical support on the move or when time is available; a more permanent fully erected treatment facility can be established. Either configuration can provide both trauma and primary care. The size of the team allows for multiple trauma subteams enabling care to casualties that arrive simultaneously. The PHTT can move independently which could leave the team vulnerable as there is no integral force protection within the current structure. In such a small team, the right balance of medical and soldiering skills among team members is essential to success. Exercise SAIF SAREEA 3 represented a large-scale battlegroup exercise to the Middle East in the austere desert of Oman. This provided an ideal environment for employing the PHTT concept is a large deployed force undertaking dynamic activity.
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19
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Ogden HB, Child RB, Fallowfield JL, Delves SK, Westwood CS, Layden JD. The Gastrointestinal Exertional Heat Stroke Paradigm: Pathophysiology, Assessment, Severity, Aetiology and Nutritional Countermeasures. Nutrients 2020; 12:E537. [PMID: 32093001 PMCID: PMC7071449 DOI: 10.3390/nu12020537] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Revised: 02/14/2020] [Accepted: 02/15/2020] [Indexed: 12/12/2022] Open
Abstract
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.
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Affiliation(s)
- Henry B. Ogden
- Faculty of Sport, Health and Wellbeing, Plymouth MARJON University, Derriford Rd, Plymouth PL6 8BH, UK; (C.S.W.); (J.D.L.)
| | - Robert B. Child
- School of Chemical Engineering, University of Birmingham, Birmingham B15 2QU, UK;
| | | | - Simon K. Delves
- Institute of Naval Medicine, Alverstoke PO12 2DW, UK; (J.L.F.); (S.K.D.)
| | - Caroline S. Westwood
- Faculty of Sport, Health and Wellbeing, Plymouth MARJON University, Derriford Rd, Plymouth PL6 8BH, UK; (C.S.W.); (J.D.L.)
| | - Joseph D. Layden
- Faculty of Sport, Health and Wellbeing, Plymouth MARJON University, Derriford Rd, Plymouth PL6 8BH, UK; (C.S.W.); (J.D.L.)
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20
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Gardner L, Miller DM, Daly C, Gupta PK, House C, Roiz de Sa D, Shaw MA, Hopkins PM. Investigating the genetic susceptibility to exertional heat illness. J Med Genet 2020; 57:531-541. [DOI: 10.1136/jmedgenet-2019-106461] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 11/25/2019] [Accepted: 12/21/2019] [Indexed: 12/16/2022]
Abstract
BackgroundWe aimed to identify rare (minor allele frequency ≤1%), potentially pathogenic non-synonymous variants in a well-characterised cohort with a clinical history of exertional heat illness (EHI) or exertional rhabdomyolysis (ER). The genetic link between malignant hyperthermia (MH) and EHI was investigated due to their phenotypic overlap.MethodsThe coding regions of 38 genes relating to skeletal muscle calcium homeostasis or exercise intolerance were sequenced in 64 patients (mostly military personnel) with a history of EHI, or ER and who were phenotyped using skeletal muscle in vitro contracture tests. We assessed the pathogenicity of variants using prevalence data, in silico analysis, phenotype and segregation evidence and by review of the literature.ResultsWe found 51 non-polymorphic, potentially pathogenic variants in 20 genes in 38 patients. Our data indicate that RYR1 p.T3711M (previously shown to be likely pathogenic for MH susceptibility) and RYR1 p.I3253T are likely pathogenic for EHI. PYGM p.A193S was found in 3 patients with EHI, which is significantly greater than the control prevalence (p=0.000025). We report the second case of EHI in which a missense variant at CACNA1S p.R498 has been found. Combinations of rare variants in the same or different genes are implicated in EHI.ConclusionWe confirm a role of RYR1 in the heritability of EHI as well as ER but highlight the likely genetic heterogeneity of these complex conditions. We propose defects, or combinations of defects, in skeletal muscle calcium homeostasis, oxidative metabolism and membrane excitability are associated with EHI.
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21
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Parsons IT, Stacey MJ, Woods DR. Heat Adaptation in Military Personnel: Mitigating Risk, Maximizing Performance. Front Physiol 2019; 10:1485. [PMID: 31920694 PMCID: PMC6928107 DOI: 10.3389/fphys.2019.01485] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 11/21/2019] [Indexed: 12/22/2022] Open
Abstract
The study of heat adaptation in military personnel offers generalizable insights into a variety of sporting, recreational and occupational populations. Conversely, certain characteristics of military employment have few parallels in civilian life, such as the imperative to achieve mission objectives during deployed operations, the opportunity to undergo training and selection for elite units or the requirement to fulfill essential duties under prolonged thermal stress. In such settings, achieving peak individual performance can be critical to organizational success. Short-notice deployment to a hot operational or training environment, exposure to high intensity exercise and undertaking ceremonial duties during extreme weather may challenge the ability to protect personnel from excessive thermal strain, especially where heat adaptation is incomplete. Graded and progressive acclimatization can reduce morbidity substantially and impact on mortality rates, yet individual variation in adaptation has the potential to undermine empirical approaches. Incapacity under heat stress can present the military with medical, occupational and logistic challenges requiring dynamic risk stratification during initial and subsequent heat stress. Using data from large studies of military personnel observing traditional and more contemporary acclimatization practices, this review article (1) characterizes the physical challenges that military training and deployed operations present (2) considers how heat adaptation has been used to augment military performance under thermal stress and (3) identifies potential solutions to optimize the risk-performance paradigm, including those with broader relevance to other populations exposed to heat stress.
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Affiliation(s)
- Iain T. Parsons
- Academic Department of Military Medicine, Research and Clinical Innovation, Royal Centre for Defence Medicine, Birmingham, United Kingdom
- School of Cardiovascular Medicine & Sciences, Faculty of Life Sciences & Medicine, King’s College London, London, United Kingdom
| | - Michael J. Stacey
- Academic Department of Military Medicine, Research and Clinical Innovation, Royal Centre for Defence Medicine, Birmingham, United Kingdom
- Department of Diabetes and Endocrinology, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - David R. Woods
- Academic Department of Military Medicine, Research and Clinical Innovation, Royal Centre for Defence Medicine, Birmingham, United Kingdom
- Department of Sport and Exercise Endocrinology, Carnegie Research Institute, Leeds Beckett University, Leeds, United Kingdom
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22
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Thermoregulation and markers of muscle breakdown in malignant hyperthermia susceptible volunteers during an acute heat tolerance test. J Sci Med Sport 2019; 22:586-590. [DOI: 10.1016/j.jsams.2018.11.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 10/03/2018] [Accepted: 11/06/2018] [Indexed: 01/24/2023]
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23
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Hosokawa Y, Casa DJ, Trtanj JM, Belval LN, Deuster PA, Giltz SM, Grundstein AJ, Hawkins MD, Huggins RA, Jacklitsch B, Jardine JF, Jones H, Kazman JB, Reynolds ME, Stearns RL, Vanos JK, Williams AL, Williams WJ. Activity modification in heat: critical assessment of guidelines across athletic, occupational, and military settings in the USA. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2019; 63:405-427. [PMID: 30710251 PMCID: PMC10041407 DOI: 10.1007/s00484-019-01673-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 01/13/2019] [Accepted: 01/15/2019] [Indexed: 05/04/2023]
Abstract
Exertional heat illness (EHI) risk is a serious concern among athletes, laborers, and warfighters. US Governing organizations have established various activity modification guidelines (AMGs) and other risk mitigation plans to help ensure the health and safety of their workers. The extent of metabolic heat production and heat gain that ensue from their work are the core reasons for EHI in the aforementioned population. Therefore, the major focus of AMGs in all settings is to modulate the work intensity and duration with additional modification in adjustable extrinsic risk factors (e.g., clothing, equipment) and intrinsic risk factors (e.g., heat acclimatization, fitness, hydration status). Future studies should continue to integrate more physiological (e.g., valid body fluid balance, internal body temperature) and biometeorological factors (e.g., cumulative heat stress) to the existing heat risk assessment models to reduce the assumptions and limitations in them. Future interagency collaboration to advance heat mitigation plans among physically active population is desired to maximize the existing resources and data to facilitate advancement in AMGs for environmental heat.
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Affiliation(s)
- Yuri Hosokawa
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA.
- College of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan.
| | - Douglas J Casa
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA
| | - Juli M Trtanj
- National Oceanic and Atmospheric Administration, Washington DC, USA
| | - Luke N Belval
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA
| | - Patricia A Deuster
- Consortium for Health and Military Performance, Department of Military and Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Sarah M Giltz
- National Oceanic and Atmospheric Administration, Washington DC, USA
- Louisiana Sea Grant, Louisiana State University, Baton Rouge, LA, USA
| | | | | | - Robert A Huggins
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA
| | - Brenda Jacklitsch
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
| | - John F Jardine
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA
| | - Hunter Jones
- National Oceanic and Atmospheric Administration, Washington DC, USA
- University Corporation for Atmospheric Research, Boulder, CO, USA
| | - Josh B Kazman
- Consortium for Health and Military Performance, Department of Military and Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Mark E Reynolds
- U.S. Army Public Health Center, Aberdeen Proving Ground, Aberdeen, MD, USA
| | - Rebecca L Stearns
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA
| | - Jennifer K Vanos
- Scripps Institution of Oceanography Department, University of California San Diego, La Jolla, CA, USA
| | - Alan L Williams
- Walter Reed National Military Medical Center, Bethesda, MD, USA
| | - W Jon Williams
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
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24
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Corbett J, White DK, Barwood MJ, Wagstaff CRD, Tipton MJ, McMorris T, Costello JT. The Effect of Head-to-Head Competition on Behavioural Thermoregulation, Thermophysiological Strain and Performance During Exercise in the Heat. Sports Med 2018; 48:1269-1279. [PMID: 29147922 PMCID: PMC5889783 DOI: 10.1007/s40279-017-0816-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Background It has been suggested that pacing is a thermoregulatory behaviour. We investigated the effect of competition on pacing, performance and thermophysiological strain during exercise in the heat and the psychological factors mediating competition effects. Method Eighteen males (maximum oxygen uptake [VO2max] 3.69 [0.44] L min−1) undertook a preliminary 20-km cool (wet-bulb globe temperature [WBGT] 12 °C) cycling time trial (TT) and three experimental 20-km trials (balanced order): (i) cool TT (CoolSolo); (ii) hot (WBGT 26 °C) TT (HotSolo); (iii) hot head-to-head competition (HotH2H). During TTs, an avatar of the participant’s performance was visible. During HotH2H, participants believed they were competing against another participant, but the competitor’s avatar replicated their own preliminary (cool) TT. Results TTs (min:sec [SD]) slowed with increased ambient temperature [CoolSolo 35:31 (2:11) versus HotSolo 36:10 (2:26); p = 0.011]. This effect was negated by competition; performances were not different between HotH2H [35:17 (1:52)] and CoolSolo (p = 0.160) and were quicker in HotH2H versus HotSolo (p = 0.001). End-exercise rectal temperature, mean body temperature and physiological strain index were (p < 0.05) higher in HotH2H than either solo condition. Despite faster performance and greater thermophysiological strain, rating of perceived exertion (RPE), thermal comfort and sensation, and perceptual strain index were not different between HotH2H and HotSolo. The difference in end-exercise rectal temperature between HotH2H and HotSolo was related to pre-exercise anticipatory heart rate response (r = 0.608, p = 0.010) and participants’ propensity for deliberate risk-taking (B = 0.12, p < 0.001), whereas self-reported resilience predicted change in performance times between HotH2H versus HotSolo (B = − 9.40, p = 0.010). Conclusion Competition changes the relationship between perceived and actual thermophysiological state, altering behavioural thermoregulation and increasing thermophysiological strain; this could increase heat-illness risk. Psychophysiological and psychological measures may identify susceptible individuals.
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Affiliation(s)
- Jo Corbett
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Spinnaker Building, Cambridge Road, Portsmouth, PO1 2ER, UK.
| | - Danny K White
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Spinnaker Building, Cambridge Road, Portsmouth, PO1 2ER, UK
| | - Martin J Barwood
- Department of Sport, Health and Nutrition, Leeds Trinity University, Brownberrie Lane, Horsforth, LS18 5HD, UK
| | - Christopher R D Wagstaff
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Spinnaker Building, Cambridge Road, Portsmouth, PO1 2ER, UK
| | - Michael J Tipton
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Spinnaker Building, Cambridge Road, Portsmouth, PO1 2ER, UK
| | - Terry McMorris
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Spinnaker Building, Cambridge Road, Portsmouth, PO1 2ER, UK.,Institute of Sport, University of Chichester, College Lane, Chichester, PO19 9PE, UK
| | - Joseph T Costello
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Spinnaker Building, Cambridge Road, Portsmouth, PO1 2ER, UK
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25
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Smith M, Withnall R, Boulter M. An exertional heat illness triage tool for a jungle training environment. J ROY ARMY MED CORPS 2017; 164:287-289. [PMID: 28883030 DOI: 10.1136/jramc-2017-000801] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 07/11/2017] [Accepted: 07/14/2017] [Indexed: 11/04/2022]
Abstract
This article introduces a practical triage tool designed to assist commanders, jungle training instructors (JTIs) and medical personnel to identify Defence Personnel (DP) with suspected exertional heat illness (EHI). The challenges of managing suspected EHI in a jungle training environment and the potential advantages to stratifying the urgency of evacuation are discussed. This tool has been designed to be an adjunct to the existing MOD mandated heat illness recognition and first aid training.
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Affiliation(s)
- Mike Smith
- Academic Department of Military General Practice (ADMGP), ICT Centre, Birmingham, UK
| | - R Withnall
- Academic Department of Military General Practice (ADMGP), ICT Centre, Birmingham, UK
| | - M Boulter
- Academic Department of Military General Practice (ADMGP), ICT Centre, Birmingham, UK
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26
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Timpmann S, Hackney AC, Tamm M, Kreegipuu K, Unt E, Ööpik V. Influence of Rhodiola rosea on the heat acclimation process in young healthy men. Appl Physiol Nutr Metab 2017; 43:63-70. [PMID: 28873320 DOI: 10.1139/apnm-2017-0372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The adaptogen Rhodiola rosea (RR) may mitigate stress responses and have beneficial effects on endurance capacity (EC) and mental performance. Heat acclimation (HA) improves EC in the heat, but the potential impact of RR on the HA process is unknown. Therefore, our intent was to determine if RR has a positive impact on HA. Twenty male subjects (age, 22.5 ± 3.0 years) completed 2 EC tests involving walking (6 km·h-1) until volitional exhaustion in a climate chamber (air temperature, 42 °C; relative humidity, 18%) before (H1) and after (H2) an 8-day HA period. One group (SHR; n = 10) ingested standardised extract SHR-5 of RR (a single daily dose of 432 mg), while a second group (PLC; n = 10) administered a placebo prior to each HA session. Efficacy of HA was evaluated on the basis of changes that occurred from H1 to H2 in the time to exhaustion (TTE), exercise heart rate (HR), core and skin temperatures (Tc, Tsk), stress hormones, ratings of perceived exertion (RPE) and fatigue (RPF), and thermal sensation (TS). HA significantly increased TTE (133.1 ± 44.1 min in H1; 233.4 ± 59.8 min in H2; p < 0.0001) and decreased (p < 0.0001) HR, Tc, Tsk, stress hormones as well as RPE, RPF, and TS. However, the magnitude of all these changes was similar (p > 0.05) in the SHR and PLC groups. These results suggest that the use of RR during HA has no beneficial performance, physiological, or perceptual effects in young healthy males.
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Affiliation(s)
- Saima Timpmann
- a Institute of Sport Sciences and Physiotherapy; Estonian Centre of Behavioral and Health Sciences, University of Tartu, 50090 Tartu, Estonia
| | - Anthony C Hackney
- b Department of Exercise and Sport Science; Department of Nutrition, School of Public Health, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Maria Tamm
- c Institute of Psychology; Estonian Centre of Behavioral and Health Sciences, University of Tartu, 50090 Tartu, Estonia
| | - Kairi Kreegipuu
- c Institute of Psychology; Estonian Centre of Behavioral and Health Sciences, University of Tartu, 50090 Tartu, Estonia
| | - Eve Unt
- d Department of Cardiology; Department of Sports Medicine and Rehabilitation, University of Tartu; Sports Medicine and Rehabilitation Clinic, Tartu University Hospital, 50406 Tartu, Estonia
| | - Vahur Ööpik
- a Institute of Sport Sciences and Physiotherapy; Estonian Centre of Behavioral and Health Sciences, University of Tartu, 50090 Tartu, Estonia
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