Skip main navigation

Military Health System

Clear Your Browser Cache

This website has recently undergone changes. Users finding unexpected concerns may care to clear their browser's cache to ensure a seamless experience.

The Military Relevance of Heat Illnesses and Their Sequelae

Image of Cover1 5605133. Military recruits often endure hot and humid training conditions putting them in danger of heat illnesses and their sequelae.

This issue of the MSMR provides an annual update on adverse health consequences most often associated with training or operations in high heat environments. Military training and operation environments create a constellation of circumstances that make service members highly susceptible to heat illnesses and their associated morbidities of exertional hyponatremia and exertional rhabdomyolysis. Leaders and medical staff must be attuned to the inherent health risks for operations in a high heat environment, especially for service members who are deconditioned or pushed to the limits of their physical endurance.

The mantra “train as you fight” requires service members to be frequently exposed to harsh environmental conditions. During initial recruit training, large amounts of time are spent outdoors, often in high heat; training installations are generally located in the southern U.S. for perennial use. The environmental stresses of heat and humidity at these installations that are experienced by individuals encumbered with heavy gear, unconditioned for the duration and intensity of the physical activity required during training, combine to create the perfect conditions for heat illness.

The first topic of this MSMR issue, heat illnesses, focuses on heat exhaustion and heat stroke. These conditions present 2 different occasions when the body can no longer rid itself of heat, either generated through activity or absorbed from the environment. Internal body temperature begins to rise during the earlier stage, heat exhaustion, when affected individuals are generally still aware of their surroundings and can assist in their own care. Heat stroke represents a much more dangerous condition in which organs begin to fail from heat overload. Heat stroke is distinguished by alteration of consciousness, typically stupor, delirium, lethargy, or unconsciousness. Mortality is a serious risk with heat stroke, and immediate action to cool the body is required.

This issue’s second and third topics, exertional rhabdomyolysis and exertional hyponatremia, are both commonly associated with heat illness, but represent organ damage (rhabdomyolysis) or unintended side effects from over-aggressive rehydration (hyponatremia). Both of these conditions can result in rapid deterioration or death if not promptly recognized and treated. While both rhabdomyolysis and hyponatremia have many non-heat-related causes, this issue deals exclusively with cases associated with high levels of exertion.

These consequences can generally be mitigated, if not fully prevented, by careful environmental risk assessment and implementation of appropriate heat countermeasures. Leaders, as part of their risk assessments, must balance mitigation efforts against the requirements of their operations or trainings. The most effective countermeasures against heat illness include restricting activity to early morning or evening when environmental heat is lower; adherence to work and rest cycles based upon current heat conditions; removal or modification of gear to facilitate heat loss; maintenance of proper hydration levels; maximized physical fitness; and gradual acclimatization to a local heat environment.

You also may be interested in...

Topic
Jun 6, 2024

Medical Surveillance Monthly Report

The Medical Surveillance Monthly Report, a peer-reviewed journal launched in 1995, is the Armed Forces Health Surveillance Division's flagship publication. The MSMR provides monthly evidence-based estimates of the incidence, distribution, impact, and trends of health-related conditions among service members.

Report
May 1, 2024

MSMR Vol. 31 No. 5 - May 2024

.PDF | 3.55 MB

The May 2024 MSMR features a report on mortality surveillance of active duty U.S. soldiers from 2014 to 2019; followed by three related reports on respiratory investigations, surveillance and forecasting, on: an outbreak of influenza and SARS-CoV-2 at the Armed Forces of the Philippines Health Service Education and Training Center, September–October ...

Article
May 1, 2024

Outbreak of Influenza and SARS-CoV-2 at the Armed Forces of the Philippines Health Service Education and Training Center, September 25–October 10, 2023

This report describes an investigation of a respiratory outbreak at the Armed Forces of the Philippines Health Service Education and Training Center by the Walter Reed Army Institute of Research-Armed Forces Research Institute of Medical Sciences and Armed Forces of the Philippines Collaborative Molecular Laboratory, demonstrating a common source ...

Article
Apr 1, 2024

Reportable Medical Events at Military Health System Facilities Through Week 9, Ending March 2, 2024

This report provides a monthly updatea of Reportable Medical Events documented in the Disease Reporting System internet (DRSi) by health care providers and public health officials throughout the Military Health System. Reportable Medical Events are a critical tool for monitoring, controlling, and preventing the occurrence and spread of diseases of ...

Article
Mar 1, 2024

Coverage of HIV Pre-Exposure Prophylaxis Within the Active Duty U.S. Military, 2023

This study provides the first estimate of HIV pre-exposure prophylaxis coverage in the U.S. military, defined as the proportion of the persons taking HIV PrEP out of the estimated number of persons who had indications for it, that is also comparable to U.S. civilian estimates. The population with indications for HIV PrEP was obtained from the ...

Skip subpage navigation
Refine your search
Last Updated: July 11, 2023
Follow us on Instagram Follow us on LinkedIn Follow us on Facebook Follow us on X Follow us on YouTube Sign up on GovDelivery