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

Exertional Heat Stroke (EHS)

While exertional heat illness (EHI) is not always a life-threatening condition, exertional heat stroke (EHS) can lead to fatality if not recognized and treated properly. As the word heat implies, these conditions most commonly occur during the hot summer months; however, EHS can happen at any time and in the absence of high environmental temperatures. Through proper education and awareness, EHS can be recognized, and treated correctly.  While not all EHS cases are preventable, schools and institutions should have the equipment and supplies ready and available to properly assess and treat a EHS case.  See the most recent data from the National Center for Catastrophic Sports Injury here.

 

How do you prevent heat stroke?

  • Ensure hydration
    • To ensure hydration, athletes can observe the color of your urine, which should be a straw yellow or the color of lemonade, or compare to a urine color chart. Your urine should be a color 3 or less.
    • Measure the athletes' weight before and after each practice to ensure they do not lose more than 2% of their pre-workout weight, assuming they started in a hydrated state. Use the equation: (Pre-exercise weight minus post-exercise weight divided by pre-exercise weight) x 100. By the time next practice begins, athletes should ingest fluids and weigh the original weight. This equation assumes that they do not eat, drink or go to the bathroom during practice.  
    • Encourage drinking throughout practice, in the shade if possible, and throughout the day, especially when having multiple practices.
    • As they become used to exercising in the heat they will sweat more and therefore need to replace a greater amount of fluids during the course of the workout.
    • Learn how to calculate your sweat rate here.
  • Wear loose-fitting, absorbent or moisture wicking clothing
    • During hot or humid conditions minimize the amount of equipment and clothing worn.
  • Minimize warm-up time, and practice in the shade when feasible.

  • Sleep at least 6–8 hours and eat a well-balanced diet.

  • Practice and perform conditioning drills at appropriate times during the day, avoiding the hottest part of the day (10am–5pm).

  • Work with coaches and administration to follow acclimation guidelines.

  • Slowly progress the amount of time and intensity of conditioning and practices throughout the season.

  • Ensure that proper medical coverage is provided and familiar with exertional heat illness (EHI) policies.

  • Include EHI questions on pre-participation exam to identify high-risk individuals.

  • Make sure your emergency action plan (EAP) is consistent with the most recent guidelines for preseason heat acclimatization; adapt individuals to heat gradually over 10–14 day period.

  • Educate other medical staff, athletes, coaches, emergency personnel, and parents about EHI and proper hydration.
  • Ensure proper body cooling methods are available, including a cold water immersion tub, ice towels, access to water, ice, etc. and that this equipment is prepared before practices begin.

  • Establish hydration policies: rest/work ratios, weigh-ins before and after activity, encourage drinking both water and fluids containing sodium.

  • Establish guidelines for hot, humid weather including; Wet Bulb Globe Temperature (WBGT) readings, time of activity, intensity/duration, equipment issues, rest/water breaks.

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

 

Click here for an overview on preventing and surviving EHS

 

What puts an individual at risk for heat cramps?

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 EHI

    • Inadequate heat acclimatization

    • Low fitness level

    • Overweight or obese

    • Inadequate hydration

    • Lack of sleep

    • 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

 

Look for these symptoms in athletes when heat cramps are suspected:

The two main criteria for diagnosing EHS are rectal temperature >104°F (40°C) immediately post collapse and central nervous system dysfunction (e.g. irrational behavior, irritability, emotional instability, altered consciousness, collapse, coma, dizziness etc)

  • When observing athletes, look for other signs and symptoms that may indicate they are suffering from exertional heat stroke:
  • Rectal temperature greater than 104°F (40°C).  Click here to learn to use a rectal thermistor
  • Irrational behavior, irritability, emotional instability
  • Altered consciousness, coma
  • Disorientation or dizziness
  • Headache
  • Confusion or just look "out of it"
  • Nausea or vomiting
  • Diarrhea
  • Muscle cramps, loss of muscle function/balance, inability to walk
  • Collapse, staggering or sluggish feeling
  • Profuse sweating
  • Decreasing performance or weakness
  • Dehydration, dry mouth, thirst
  • Rapid pulse, low blood pressure, quick breathing
  • Other outside factors may include:
    • They are out of shape or obese
    • It is a hot and humid day
    • Practice is near the start of the season, and near the end of practice
    • It is the first day in full pads and equipment

 

What else could this be?

  • Heat exhaustion
  • Exertional hyponatremia
  • Concussion
  • Cardiac arrest

 

How do you treat an individual with heat stroke?

Follow these steps to initiate emergency treatment:

  • Remove all equipment and excess clothing.

  • Cool the athlete as quickly as possible within 30 minutes via whole body ice water immersion (place them in a tub/stock tank with ice and water approximately 35–58°F); stir water and add ice throughout cooling process. (See KSI Cold Water Immersion handout for step by step guidelines)

  • If immersion is not possible (no tub or no water supply), take athlete into a cold shower or move to shaded, cool area and use rotating cold, wet towels to cover as much of the body surface as possible.

  • Maintain airway, breathing and circulation.

  • After cooling has been initiated, activate emergency medical system by calling 911.

  • Monitor vital signs such as rectal temperature, heart rate, respiratory rate, blood pressure, monitor CNS status.
    • If rectal temperature is not available, DO NOT USE AN ALTERNATE METHOD (oral, tympanic, axillary, forehead sticker, etc.).  These devices are not accurate and should never be used to assess an athlete exercising in the heat.
  • Cease cooling when rectal temperature reaches 101–102°F (38.3–38.9°C).

Exertional heat stroke has had a 100% survival rate when immediate cooling (via cold water immersion or aggressive whole body cold water dousing) was initiated within 10 minutes of collapse.

If a tub is not available, a body bag is another option to cool an EHS victim.  See more information here.

Click here to learn what equipment is necessary to treat an EHS victim

 

When can the individual return to activity?

After an EHS episode occurs, there may be physiological changes, such as heat tolerance, that are temporarily, and occasionally, permanently compromised. Long-term complications and morbidity are directly related to the time that the core body temperature remained above the critical threshold. To safely return an athlete to full participation following an EHS, a specific return-to-play (RTP) strategy should be implemented. The following guidelines are recommended for RTP:

  • Physician clearance prior to return to physical activity. The athlete must be asymptomatic and lab tests must be normal.
  • The length of recovery time is primarily dictated by the severity of the incident.
  • The athlete should avoid exercise for at least one (1) week after the incident.
  • The athlete should begin a gradual RTP protocol in which they are under the direct supervision of an appropriate health-care professional such as an athletic trainer or physician.
  • The type and length of the RTP program may vary among individuals, but a general program may include:
    • Easy-to-moderate exercise in a climate-controlled environment for several days, followed by strenuous exercise in a climate-controlled environment for several days
    • Easy-to-moderate exercise in the heat for several days, followed by strenuous exercise in the heat for several days
    • If applicable to the individuals sport: easy-to-moderate exercise in the heat with equipment for several days, followed by strenuous exercise in the heat with equipment for several days

Click here for a summary of how to respond to an EHS emergency

 

Recommended Equipment List

  • Wet Bulb Globe Temperature (WBGT) Device
  • Rectal thermometer
  • Lubricating gel
  • Tub or kiddy pool
  • Cooler with ice
  • Water source
  • 3-4 towels
  • Tent for shade

 

References

  1. Armstrong LE, Casa DJ, Millard-Stafford M, Moran DS, Pyne SW, Roberts WO. American College of Sports Medicine position stand: exertional heat illness during training and competition. Med Sci Sports Exerc. 2007;39:556–572.
  2. Binkley HM, Beckett J, Casa DJ, Kleiner DM, Plummer PE. National Athletic Trainers’ Association position statement: exertional heat illnesses. J Athl Train. 2002;37:329–343.
  3. Armstrong LE. Exertional Heat Illnesses. Human Kinetics; 2003.
  4. Casa DJ, Csillan D. Preseason heat-acclimatization guidelines for secondary school athletics. J Athl Train. 2009;44(3):332–333.
  5. Casa DJ, Armstrong LE, Hillman SK, Montain SJ, Beiff RV, Rich BSE, Roberts WO, Stone JA. National athletic trainers’ association position statement: Fluid replacement for athletes. J Athl Train. 2000;35:212–224.