What is EHS?

Exertional heat stroke (EHS), a severe form of heat-related illness, is a medical emergency that can result in organ damage or even death in some cases.1

How does it happen?

EHS can occur during a variety of situations involving strenuous exercise, work or recreational activities, in particularly hot temperature conditions.2 In EHS, core body temperature rises to a dangerous level (104oF or greater),*3 and can be associated with organ damage or death.1

In addition to a high core body temperature of 104oF or greater,* the signs and symptoms of EHS include:3

  • Fainting/dizziness
  • Vomiting
  • Confusion or disorientation
  • Unusual behavior (e.g., aggression)

Who is at risk?

EHS can occur in seemingly healthy people – it is more likely to occur in hot and humid environments, but people can be at risk in other environmental conditions.4,5,6

Firefighters, outdoor workers and military personnel operating in high temperatures are among those at high risk, as are athletes.2  In fact, EHS is considered the third leading cause of sudden death in high school athletes.4,7

How can you protect yourself and others?

Knowledge is key when it comes to EHS. It’s important to know the warning signs and symptoms. This easy acronym will help in identifying EHS:

Remember H.E.A.T. to help save a life.

H – High temperature
E – Exercise or activity
A – Acting confused
T – Time to call 911


Download and print The Heat Factor’s EHS awareness poster to hang up in your office, locker room or gym:

8×11 H.E.A.T. poster

11×17 H.E.A.T. poster

24×36 H.E.A.T. poster


* Measured rectally



1. Walter EJ, Carraretto M. The neurological and cognitive consequences of hyperthermia. Critical Care. 2016;20(199). doi:10.1186/s13054-016-1376-4.

2. Leon LR, Helwig BG. Heat stroke: role of the systemic inflammatory response. J Appl Physiol. 2010;109:1980-1988. doi:10.1152/japplphysiol.00301.2010.

3. Casa DJ, DeMartini JK, Bergeron MF, Csillan D, Eichner R, Lopez RM, Ferrara MS, Miller KC, O’Connor F, Sawka M, Yeargin SW. National athletic trainers’ association position statement: exertional heat illness. J Athl Train. 2015;50(9). http://natajournals.org/doi/pdf/10.4085/1062-6050-50.9.07?code=nata-site. Accessed May 9 2017. 

4. King MA, Leon LR, Mustico DL, Haines JM, Clanton TL. Biomarkers of multiorgan injury in a preclinical model of exertional heat stroke. J Appl Physiol. 2015;118:1207-1220. doi:10.1152/japplphysiol.01051.2014.

5. Becker JA, Stewart LK. Heat-related illness. Am Fam Physician. 2011;83(11):1325-1330

6. Epstein Y, Moran DS, Shapiro Y. Exertional heatstroke in the Israeli defence forces. In: Pandoff KB, Burr RE, eds. Medical Aspects of Harsh Environments. Volume 1. Office of the Surgeon General, United States Army. 2002;281-292.

7. Jardine DS. Heat illness and heat stroke. Pediatr Rev Am Acad Pediatric. 2007;28(7). doi:10.1542/pir.28-7-249.