Exertional Heat Stroke in Military Settings: What International Research Tells Us About Prevention and Treatment

In 2024, heat illness was among the top five most frequently reported medical events among US active duty service members. After several years of declining rates, heat stroke cases increased again. A comprehensive international review published in 2025 in Frontiers in Physiology, co-authored by researchers from the US Army, French military, and other armed forces, consolidates what military medicine has learned — and where critical gaps remain.

The scale of the problem in 2024

According to a surveillance report published by the Defense Centers of Public Health in the Medical Surveillance Monthly Report (2025), the crude incidence rate of heat stroke among US active duty service members in 2024 was 36.4 cases per 100,000 person-years. Heat exhaustion rates were worse: 183.9 per 100,000 person-years, increasing every year from 2020 through 2024.

As Epstein, Charkoudian, DeGroot, Malgoyre, O'Connor et al. noted in their 2025 international review published in Frontiers in Physiology: the US Army reported a 42% increase in the rate of heat exhaustion cases over the last three years. The populations at highest risk: service members under age 20, Marine Corps and Army personnel, and recruit trainees.

Why military personnel face elevated risk

Protective equipment and uniforms -- a full combat load can reduce the body's heat dissipation capacity by up to 50%. The thermal burden of protective gear is not offset by fitness level.

Sustained high-intensity effort without pace control -- tactical exercises and endurance marches do not allow adaptation to thermal sensation. Soldiers are trained to push through discomfort, which can mask the early neurological signs of EHS.

Cultural pressure to perform -- under-reporting is a known dynamic in military training. A soldier experiencing confusion or disorientation may not self-report.

High-heat operational environments -- deployment in subtropical or desert environments maintains an elevated external thermal load, independent of exertion level.

What every medic needs to recognize immediately

Exertional heat stroke requires two simultaneous criteria:

1. Core body temperature above 104°F (40°C), measured rectally
2. Neurological signs: confusion, disorientation, loss of consciousness, seizures, ataxia, irrational behavior

The field rule is absolute: any service member who collapses during or immediately after physical exertion must be treated as a presumptive EHS case. Rectal temperature is the reference standard. Ear thermometers and forehead devices are not reliable enough to confirm or rule out the diagnosis.

The treatment protocol: cool first, transport second

The US military's Clinical Practice Guideline for the Prevention, Diagnosis, and Management of Exertional Heat Illness (CHAMP/USUHS, June 2024) is unambiguous: the reference treatment for EHS is immediate whole-body cold water immersion.

The Defense Health Agency stated it directly in a June 2025 article on army.mil: "We now have evidence that immediately cooling a heat-stroke casualty by wrapping their body in ice sheets in the field before transporting for further medical treatment can save a life."

The protocol is cool first, transport second. Medical evacuation must not delay or interrupt active cooling. Target: below 102°F (38.9°C) rectal temperature.

Prevention: what the international research recommends

The Epstein et al. (2025) international review consolidates the evidence base:

• Heat acclimatization: 10-to-14-day progressive exposure before any hot-climate deployment or intensive summer training program
• WBGT monitoring: Wet Bulb Globe Temperature thresholds used to modulate training intensity — standard in US military guidelines, should be adopted broadly
• Leadership-level recognition training: unit leaders, not just medical staff, must know the protocol and be trained to recognize early signs

The logistics gap: equipment at the point of need

The international review is explicit: the principal remaining barrier to effective EHS treatment in military settings is not knowledge — it is equipment availability at the point of need. A cooling tub left in a medical depot cannot help a soldier who collapses on a training range.

Sources

• Epstein Y, Charkoudian N, DeGroot DW, Malgoyre A, O'Connor FG, et al., Exertional heat illness: international military-oriented lessons learned and best practices, Frontiers in Physiology, 2025 — pmc.ncbi.nlm.nih.gov
• Maule AL, et al., Heat Exhaustion and Heat Stroke Among Active Component Members of the U.S. Armed Forces, 2020-2024, 2025 — pmc.ncbi.nlm.nih.gov
• Defense Health Agency, Military Efforts Preventing Severe Heat Illness Cases, army.mil, June 2025 — army.mil
• CHAMP/USUHS, Clinical Practice Guideline: Exertional Heat Illness, June 2024 — champ.usuhs.edu

Kollder is the emergency cooling tub that deploys in under 30 seconds, anywhere.

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