Risk Factors for Exertional Heat Illness

Prospective Investigation of Risk Factors for Exertional Heat Illness

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 aim of this study is to examine traditional and novel risk factors that may increase thermal strain and EHI likelihood in military recruits undergoing strenuous physical exercise.

Study Overview

• Status: Active, not recruiting
• Conditions: Exertional Heat Illness
• Intervention / Treatment: Other: Core temperature monitoring; Behavioral: Questionnaires; Other: Heart rate monitoring; Other: Urine collection; Other: Sleep monitoring; Other: Blood collection; Other: Saliva collection; Other: Throat swab collection; Other: Stool collection

• Study Type: Observational
• Enrollment (Estimated): 783

Contacts and Locations

Study Locations

• United Kingdom
  • Devon
    • Lympstone, Devon, United Kingdom, EX8 5AR
      • Commando Training Centre Royal Marine

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 17 years to 35 years (Child, Adult)
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Participants who experience and participants who do not experience an atypical elevation in thermal strain or an EHI undergoing strenuous physical exercise.

Description

Inclusion Criteria:

• Men and women aged 17-35 years enrolled in military training

Exclusion Criteria:

• Self-report as pregnant

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Exertional heat illness; Participants who experience an atypical elevation in thermal strain or an EHI undergoing strenuous physical exercise.	Other: Core temperature monitoring; Core temperature will be monitored on the day of exercise; Behavioral: Questionnaires; Questionnaires will be completed at baseline and on the day of exercise; Other: Heart rate monitoring; Heart rate will be monitored on the day of exercise; Other: Urine collection; Urine samples will be collected at baseline and on the day of exercise; Other: Sleep monitoring; Sleep will be monitored at baseline and on the day of exercise; Other: Blood collection; Blood samples will be completed at baseline; Other: Saliva collection; Saliva samples will be collected at baseline and on the day of exercise; Other: Throat swab collection; Throat swab samples will be collected at baseline and on the day of exercise; Other: Stool collection; Stool samples will be collected at baseline and on the day of exercise
Control; Participants who do not experience an atypical elevation in thermal strain or an EHI undergoing strenuous physical exercise.	Other: Core temperature monitoring; Core temperature will be monitored on the day of exercise; Behavioral: Questionnaires; Questionnaires will be completed at baseline and on the day of exercise; Other: Heart rate monitoring; Heart rate will be monitored on the day of exercise; Other: Urine collection; Urine samples will be collected at baseline and on the day of exercise; Other: Sleep monitoring; Sleep will be monitored at baseline and on the day of exercise; Other: Blood collection; Blood samples will be completed at baseline; Other: Saliva collection; Saliva samples will be collected at baseline and on the day of exercise; Other: Throat swab collection; Throat swab samples will be collected at baseline and on the day of exercise; Other: Stool collection; Stool samples will be collected at baseline and on the day of exercise

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Body mass index in EHI and control group		Baseline
Fitness in EHI and control group - participants ranked by time to complete fitness test		Baseline
Core temperature in EHI and control group		1 Day
Heart rate in EHI and control group		2 Hours
Urine osmolality in EHI and control group		Baseline
Sleep quality and quantity, measured by Pittsburgh Sleep Quality Index, in EHI and control group	0-21 Scale. Higher score indicates worse outcome	Throughout study - up to 1 week
Sleep quality, measured by actigraphy, between EHI and control group		Throughout study - up to 1 week
Sleep quantity, measured by actigraphy, between EHI and control group		Throughout study - up to 1 week
Circulating Interleukin 6 in EHI and control group		Baseline
Circulating C-Reactive Protein in EHI and control group		Baseline
Circulating Creatine kinase in EHI and control group		Baseline
Circulating Aspartate Aminotransferase in EHI and control group		Baseline
Circulating Alanine Aminotransferase in EHI and control group		Baseline
Circulating Claudin 3 in EHI and control group		Baseline
Circulating Zonulin in EHI and control group		Baseline
Circulating Lipopolysaccharide binding protein in EHI and control group		Baseline
Circulating immunoglobulin E in EHI and control group		Baseline
Salivary cortisol in EHI and control group		Throughout study - up to 1 week
Detection of infectious pathogens in EHI and control groups		Throughout study - up to 1 week
Respiratory illness symptomology, measured by Jackson common cold questionnaire, in EHI and control group	0-24 Scale. Higher score indicates worse outcome	Throughout study - up to 1 week
Gastrointestinal illness symptomology, measured by gastrointestinal symptoms questionnaire, in EHI and control group	0-10 Scale per symptom. Higher score indicates worse outcome	Throughout study - up to 1 week
Abundance and diversity of gastrointestinal microbiota in EHI and control group		Baseline

Collaborators and Investigators

• Sponsor: Liverpool John Moores University
• Collaborators: Institute of Naval Medicine (UK); CTCRM Lympstone (UK); University of Portsmouth (UK); Public Health Wales (UK); Bangor University (UK); Headquarters Army Recruiting and Initial Training Command (UK); Defence Science and Technology (UK)

Study record dates

Study Major Dates

• Study Start (Actual): June 11, 2021
• Primary Completion (Actual): July 22, 2024
• Study Completion (Estimated): July 1, 2025

Study Registration Dates

• First Submitted: May 28, 2021
• First Submitted That Met QC Criteria: July 16, 2021
• First Posted (Actual): July 28, 2021

Study Record Updates

• Last Update Posted (Actual): March 25, 2025
• Last Update Submitted That Met QC Criteria: March 17, 2025
• Last Verified: October 1, 2024

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Wounds and Injuries; Heat Stress Disorders
• Other Study ID Numbers: 2029/MODREC/21

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No