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

Heat Exhaustion

Heat exhaustion is the most common heat-related condition observed in active populations. It is defined as the inability to continue exercise in the heat due to cardiovascular insufficiency and energy depletion that may or may not be associated with physical collapse.  Cardiovascular insufficiency refers to when the heart has difficulty providing enough oxygenated blood to all the working organs and muscles.


How do you prevent heat exhaustion?

  • Individuals should adapt to exercise in the heat gradually -- acclimatize -- over 10-14 days by progressively increasing duration and intensity of work
  • Be able to recognize heat exhaustion and exertional heat stroke
  • Use accurate equipment when diagnosing (rectal thermometer)
  • Know the most updated treatment methods
  • Being adequately hydrated before and during exercise can help prevent heat illnesses
  • Appropriate work to rest ratio for environmental conditions and acclimatization


What puts an individual at risk for heat exhaustion?

  • Exercising in hot and humid environment (air temp > 33°C)

  • Inadequate fluid intake (dehydration)
  • Inappropriate work to rest ratios
  • Body mass index > 27 kg/m


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

Fatigue Nausea Fainting
Weakness Vomiting Dizziness / Light-headedness
Pale Chills Diarrhea
Heavy Sweating Decreased Urine Output / Dehydration Irritability
Headache Sodium Loss Decreased Blood Pressure
Decreased Muscle Coordination Hyperventilation Core body temperature between 36-40°C (96.8-104°F)   


How do you treat an individual with heat exhaustion?

Individuals experiencing heat exhaustion should respond quickly to treatment.  If not, exertional heat stroke should be suspected.  In this case, obtain a rectal temperature and assess central nervous system function to rule out exertional heat stroke.  If the person is experiencing heat exhaustion, the rectal temperature should be < 40°C/104°F. To treat heat exhaustion:

  • Move the individual to a cool/shaded area and remove excess clothing
  • Elevate legs to promote venous return
  • Cool the individual with fans, rotating ice towels, or ice bags
  • Provide oral fluids for rehydration


When can the individual return to activity?

Returning to activity the same day of an episode is not prudent or advised. Individuals should wait at least 24-48 hrs before returning to activity and should gradually increase intensity and volume of exercise, and clothing and equipment.  Medical clearance is recommended to rule out other conditions.



  1. Armstrong LE. Exertional Heat Illnesses. Human Kinetics; 2003.
  2. 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.
  3. 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.