Exertional Heat Illness
Conditions
Brief summary
The arduous nature of military training and operations require personnel to encounter high heat load, e.g., during intense physical exertion, particularly in the heat. These conditions reduce operational effectiveness and expose personnel to a risk of incapacitation and death from exertional heat illness (EHI). The primary aim of this study is to compare putative 'chronic' EHI risk factors between a cohort who have suffered a history of EHI and a control cohort with no EHI history. The secondary aim is to examine the influence of these EHI risk factors on thermoregulation during a standard heat tolerance assessment.
Detailed description
Military training and operations present a risk of incapacitation and death from Exertional Heat Illness (EHI). However, widely accepted EHI risk factors are absent in almost half of all United Kingdom (UK) military EHI cases, indicating that a significant number of EHI cases in military personnel involve alternative risk factors. Risk factors for EHI can been classified along a spectrum ranging from acute (e.g. recent poor sleep) to chronic (e.g. low fitness), with the role of chronic risk factors supported by the observation that individuals who have suffered an EHI are at a substantially increased risk of subsequent EHI. The primary aim of this study is to compare putative 'chronic' EHI risk factors (e.g. composition of gastrointestinal (GI) microbiome, infection and inflammation, trait-like psychological factors) between a cohort who have suffered a history of EHI and a control cohort with no EHI history. The secondary aim is to examine the influence of these EHI risk factors on thermoregulation during a standard heat tolerance assessment.
Interventions
OTHERHeat Tolerance Assessment
60-90 minutes exercise in hot (34 °C; 45% R.H.) conditions at 60%VO2max
Sponsors
Liverpool John Moores University
Institute of Naval Medicine (UK)
Headquarters Army Recruiting and Initial Training Command (UK)
Public Health Wales
University of Portsmouth
Study design
Observational model
CASE_CONTROL
Time perspective
CROSS_SECTIONAL
Eligibility
Sex/Gender
ALL
Age
18 Years to 40 Years
Healthy volunteers
Yes
Inclusion criteria
Individuals with a history of EHI: * Previous EHI episode * Normal resting ECG * Male or female * 18 - 40 years Control participants: * No previous history of EHI * Normal resting ECG * Male or female * 18 - 40 years
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Resilience, measured by the Connor-Davidson resilience scale | Baseline -3 days | — |
| Core temperature | At 60 minutes (or test termination if earlier) of Heat Tolerance Assessment | Measured using a rectal thermistor. |
| Stress, measured by perceived stress scale | Baseline -3 days | — |
| Diversity of gastrointestinal microbiota | Baseline | Measured in stool sample. Assessed by alpha diversity score. |
| Abundance of gastrointestinal microbiota | Baseline | Measured in stool sample. Assessed at level of phylum. |
| Mental readiness | Baseline | Visual analogue scale (0-100). Higher scores indicate a lower state of mental readiness. |
| Detection of sexually transmitted pathogens | Baseline | Assessed from urine sample. Measured using cobas CT/NG assays. |
| Detection of respiratory pathogens | Baseline | Assessed from throat swab. Measured using Allplex assays. |
| Detection of gastrointestinal pathogens | Baseline | Assessed from stool swab. Measured using Allplex. |
| Circulating Interleukin 6 | Baseline | Measured using ELISA |
| Circulating C-Reactive Protein | Baseline | Measured using ELISA |
| Circulating Claudin 3 | Baseline | Measured using ELISA |
| Circulating Zonulin | Baseline | Measured using ELISA |
| Circulating lipopolysaccharide binding protein | Baseline | Measured using ELISA |
| Circulating intestinal fatty acid binding protein | Baseline | Measured using ELISA |
| Gastrointestinal illness symptomology questionnaire | Baseline | Visual analogue scale (0-10). Higher scores indicate worse symptomology |
| Respiratory illness symptomology, measured by Jackson common cold questionnaire | Baseline | Higher scores indicate worse symptomology |
| Sleep quality and quantity, measured by Pittsburgh Sleep Quality Index | Baseline -3 days | Higher scores indicate worse sleep |
| Motivation, measured by Motivation scale | Baseline -3 days | — |
| State-trait anxiety, measured by state-trait anxiety inventory form Y-2 | Baseline -3 days | — |
| Risk taking, measured by the risk-taking inventory | Baseline -3 days | — |
| Stress | Baseline | Visual analogue scale (0-100). Higher scores indicate a greater state of stress. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Sweat rate | During Heat Tolerance Assessment | Determined from change in nude body mass during the heat tolerance assessment |
| Skin Temperature | During Heat Tolerance Assessment | Weighted mean skin temperature |
| Heat rate | At 5 minute intervals during the Heat Tolerance Assessment | — |
| Thermal comfort | At 15 minute intervals during Heat Tolerance Assessment | Modified 9 point Gagge scale. Higher scores indicate worse comfort. |
| Thermal sensation | At 15 minute intervals during Heat Tolerance Assessment | Modified 9 point Gagge scale. Higher scores indicate hotter sensation |
| Rating of Perceived Exertion | At 15 minute intervals during Heat Tolerance Assessment | 6-20 Borg scale. Higher scores indicate higher perceived exertion |
Other
| Measure | Time frame | Description |
|---|---|---|
| Relative maximal aerobic fitness | Baseline | Highest value measured in ml.kg-1.min-1 during a treadmill graded exercise test. |
| Urine osmolality | Baseline | Measured using freezing point depression |
| Body mass | Baseline | — |
Countries
United Kingdom
Outcome results
None listed