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University of Connecticut College of Agriculture, Health and Natural Resources Korey Stringer Institute

Exertional Heat Illnesses

Exertional heat illnesses (EHI) are most likely to occur in hot and humid conditions, but can occur in more moderate environments when exercise intensity is high or heavy equipment is worn.  Body temperature rises during exercise which causes the body to produce sweat in an attempt to cool off.  When a lot of sweating occurs, the body becomes dehydrated and continues to rise in temperature.  Under these conditions, EHI such as heat syncope, heat cramps, heat exhaustion, and exertional heat stroke are most likely to occur.


See Arkansas' Department of Health Website for Additional Information


Preventing Heat Illness

  • Consider the Wet Bulb Globe Temperature (WBGT) if you are covering an event in the heat.

  • Talk to other available medical staff at the event such as athletic trainers and team physicians about their emergency action plan (EAP), location of relevant equipment, and treatment protocol for EHS.

  • Encourage proper hydration status by checking to see if there are water stations located around the event.

  • Have the appropriate size staff available for the event.

  • Have proper equipment or immediate access to proper equipment to treat EHS such as an immersion tub, rectal thermometer, access to ice and water, IV fluids, cool liquids, blood pressure cuff, heart rate monitor, etc.

  • Review diagnostic criteria for EHS and the associated signs and symptoms annually.

  • Avoid holding events during the middle of the day when it is hottest outside.

  • Ensure athletes have shaded areas to rest and rehydrate under.

  • During periods of rest, or at hydration stations, encourage drinking.

  • To aid in preventing EHS, proper hydration should be monitored and encouraged along with other preventive methods.

  • Consider cooling devices during rest periods such as ice packs, cool towels, misting fans, etc.

  • Maintain an ample supply of ice, water, towels and other emergency equipment necessary to prevent and treat EHS.

  • Be aware of the intrinsic factors (mostly in the athletes' control/items they can adjust) and extrinsic factors (mostly outside the athletes' control) that cause EHS.

  • Exercise extra caution if an athlete has any of these intrinsic factors or you are concerned regarding any of the extrinsic factors.
    • Intrinsic Factors
      • History of Exertional Heat Stroke
      • Inadequate heat acclimatization
      • Low fitness level
      • Overweight or obese
      • Inadequate hydration
      • Fever
      • Stomach illness
      • Highly motivated/ultra-competitive
      • Pre-pubescent
    • Extrinsic Factors
      • Intense or prolonged exercise with minimal breaks
      • High temperature/humidity/sun exposure as well as exposure to similar conditions the previous day
      • Inappropriate work/rest ratios based on intensity
      • Wet Bulb Globe Temperature (WBGT)
      • Clothing
      • Equipment
      • Fitness
      • Lack of education and awareness of heat illness among coaches, athletes, and medical staff
      • Absence of an emergency action plan, or failure of emergency action plan to include EHS
      • No or limited access to fluids or breaks during practice
      • Delay in recognition of signs and symptoms associated with EHS

See more tips here from Gatorade

Click here for an overview on preventing and surviving EHS

Myths About Exertional Heat Illness

There are numerous myths and misconceptions regarding exertional heat illness.  The following table explains some of the more common misconceptions.


Explaination of Misconception

The onset of exertional heat stroke (EHS) is random and unpredictable.

Numerous predisposing factors of EHS have been documented.  Some of these include:  environmental conditions (high temperature and/or high humidity), high intensity exercise, lack of acclimatization, low physical fitness level, equipment that prevents heat loss, sleep deprivation, dehydration, fever, etc.  With knowledge and recognition of these factors, high-risk individuals can be identified.

It’s possible to assess body temperature by external means.

No external temperature assessment devices currently available have ever been proven valid under the conditions of intense exercise in the heat and a significant degree of hyperthermia. External temperature devices, including oral, tympanic, temporal, forehead sticker, axillary devices, should never be used to diagnose exertional heat stroke. The only device that is valid under these conditions for the immediate detection of body temperature is the rectal thermistor.  The ingestible thermistor is a second viable measure.  However, ingestible thermistor devices must be taken at least six to eight hours before activity begins, therefore it cannot be used when an athlete is already suffering from an EHS.

The appearance of a lucid mental status means everything is okay.

One factor that may obscure or delay the diagnosis of EHS is the lucid interval that presents initially for many EHS patients.  This lucid interval often coincides with only minimal Central Nervous System (CNS) dysfunction and misleads the caregiver regarding the severity of the condition (i.e. EHS vs. heat exhaustion).  However, in the case of EHS, this lucid interval will be followed by severe CNS signs and symptoms.

Peripheral Vasoconstriction (PVC) delays cooling

While PVC may occur during cold water immersion (CWI) it is greatly overshadowed by the great conductive and convective thermal transfer which cools the body rapidly.  Furthermore, PVC certainly occurs when a normothermic individual is placed in a cold water bath. Although PVC may minutely increase core body temperature initially, even in a EHS victim, a rapid decrease in body temperature will immediately follow. 

Shivering delays cooling

Similar to PVC, shivering will certainly occur when a normothermic individual is placed in a cold water bath.  However, this is seldom the case with a hyperthermic individual.  Research shows that powerful rapid cooling will still occur in hyperthermic individuals with few occurrences of a shivering response.

Cold water immersion is uncomfortable for patient/staff

The physical comfort of the patient or staff should not be a primary concern during the acute treatment of EHS.  Comfort, although a consideration, should be secondary to delivery of optimal treatment.

It is difficult to apply supplemental treatments (AED, IV fluid, oxygen, etc.)

While certainly valid, this is an emergency condition in which the risks of EHS greatly outweigh the risks or inconveniences of foregoing supplemental treatments.

There is a risk of drowning with cold water immersion

Drowning should not be a primary concern if proper precautions are taken: supervise the athlete at all times, recruit teammates/colleagues to assist, and place a sheet under the armpits of the athlete to prohibit their head from falling under water.

Cold water immersion may be unsanitary

While unsanitary conditions may be present due to vomiting or diarrhea, an unsanitary tub is an acceptable tradeoff to a permanently disabled athlete.  In the case of unsanitary conditions, the tub should be properly cleaned after use to prevent subsequent problems.

Hypothermic afterdrop (continued cooling post-immersion) can occur

Hypothermic afterdrop may be a concern if the athlete is cooled too long.  However, with the use of a proper core body temperature assessment device -- rectal thermometer -- body temperature can be continuously monitored throughout cooling to prevent this afterdrop.

An athlete stops sweating during a case of EHS

Since EHS occurs during intense exercise in the heat, the athlete is almost always profusely sweating upon collapse of EHS.  This is perhaps the most widely misunderstood sign of EHS and may lead to mistreatment. 

An athlete must be severely dehydrated for EHS to occur

While dehydration may predispose an athlete to exertional heat illness and/or exacerbate an EHS, dehydration does not always have to be present.  EHS can occur in as little as 20 minutes after the beginning of exercise before severe fluid loss is prominent.  Exercise intensity and environmental conditions are the primary factors associated with EHS.