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Heat Illness Terms Defined

Sports medicine practitioners throw around a lot of different terms when it comes to heat illness.  Here's how the American Academy of Pediatrics,1 defines some of the commonly used terms:

  • Heat stress: High air temperature, humidity, and solar radiation that lead to perceived discomfort and physiologic strain when children and adolescents are exposed to such environmental conditions, especially during vigorous exercise and other physical activity.
  • Exertional heat illness: A spectrum of clinical conditions that range from muscle (heat) cramps, heat syncope (fainting), and heat exhaustion to life-threatening heat stroke incurred as a result of exercise or other physical activity in the heat.
  • Heat exhaustion: Moderate heat illness, characterized by an inability to maintain blood pressure and sustain adequate cardiac outpout, that results from strenuous exercise or other physical activity, environmental heat stres, acute dehydration, and energy depletion. Signs and symptoms include weakness, dizziness, nausea, syncope (fainting), and headache; core body temperature is <104CF (40°C).
  • Exertional heat stroke: Severe multi-system heat illness, characterized by central nervous system abnormalities such as delirium, convulsions, or coma, endotoxemia, circulatory failure, temperature-control dysregulation, and, potentially, organ and tissue damage, that results from an elevated core body temperature (>104°F [>40°C) that is induced by strenuous exercise or other physical activity and typically (not always) high environmental heat stress. 
  • Heat injury: Profound damage and dysfunction to the brain, heart, liver, kidneys, intestine, spleen, or muscle induced by excessive sustained core body temperature associated with incurring extertional heat stroke, especially for those victims in whom signs and/or symptoms are not promptly recognized and are not treatedly effectively (rapidly cooled) in a timely manner.


1. Bergeron MF, Rice SG, DiLaura Devore C & Council on Sports Medicine and Fitness and Council on School Health.  Policy Statement - Climactic Heat Stress and Exercising Children and Adolescents. Pediatrics 2011; 128(3) (published on line August 8, 2011).