Physiological Responses to Heat Stress During High-risk Events

Launched by UNITED STATES ARMY RESEARCH INSTITUTE OF ENVIRONMENTAL MEDICINE · Mar 31, 2025

Keywords

ClinConnect Summary

This is an observational study (no medicine or treatment being tested) looking at how soldiers’ bodies respond to heat during high‑risk training events, like hard marches or timed runs. Researchers want to learn which body signals (biomarkers) show how the body handles heat, recovers, and what helps a soldier safely return to duty after heat illness. About 150 adult soldiers are expected to take part. Eligible people are 18 or older, currently serving in the military and actively in training. Both men and women can join. Exclusion criteria include pregnancy, medical rules that prevent running or marching, certain digestive diseases, plans for an MRI soon after a core‑temp pill is used, skin adhesive allergies, or recent blood donation.

If you join, you’ll be observed during the training events. Core temperature will be monitored with a small temperature pill, and you’ll have blood tests about every 6 hours for up to 36 hours to check kidney and liver function, plus a heart rate check during the activity (about 4 hours). Urine samples will also be collected every 6 hours for up to 36 hours. Researchers will store the samples for analysis, but no DNA will be collected, and there’s no experimental treatment involved. The study is being conducted at U.S. Army research sites and is expected to run through 2026. The goal is to improve understanding of heat stress and help guide prevention, treatment, and decision-making about when it’s safe to return to duty.

Gender

ALL

Eligibility criteria

• Inclusion Criteria:
• • Individuals (to include cis- and transgender males and females and nonbinary) 18 years of age or greater
• • Current military service (active, Reserve, or National Guard)
• • Currently participating in training
• Exclusion Criteria:
• • Females who are pregnant
• • Any individual currently on a physical profile that restricts running or foot marching
• • History of obstructive disease of the gastrointestinal tract including (but not limited to) diverticulosis, diverticulitis and inflammatory bowel disease, peptic ulcer disease, Crohn's disease, ulcerative colitis.
• • Scheduled MRI within 2 weeks after core temp pill ingestion
• • Known allergies to skin adhesive
• • Blood donation in the past 8 weeks