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Exertional Heat Illnesses (EHI) can occur during exercise in the heat as well as normal conditions. EHIs are classified as exercise-associated muscle cramps, heat syncope, heat exhaustion, exertional heat injury or heat stroke.

EHI risk factors can be classified as either environmental or non-environmental. Environmental risk factors include temperature, humidity, wet-blub globe temperature (WBGT), athletic equipment that reduces evaporative heat loss, and participation in high WBGT the previous day. Non-environmental risk factors include lack of heat acclimatization, exercise intensity, poor physical condition, increased body mass, dehydration, illness, history of EHI, medications and electrolyte balance.

EHI prevention includes pre-participation screening, proper acclimatization, proper hydration, electrolyte balance, efficient recognition of EHI signs and symptoms by the medical and coaching staff, availability of a cold water immersion tub, modified activity in high-WBGT conditions, and closely monitoring at-risk individuals during activity.

Exercise-associated muscle cramps: Sudden, involuntary, painful contractions of skeletal muscles during or after activity.

Symptoms: Visible cramping in all or part of the muscle, localized pain, dehydration, thirst, sweating, and fatigue.

Treatment: Rest, passive static stretching of affected muscle, high sodium drinks or food.

Heat syncope: Dizziness that occurs in unfit or un-acclimatized athletes while they are in heat for prolonged periods of time.

Symptoms: Brief episode of fainting, dizziness, tunnel vision, pale/sweaty skin, decreased pulse rate, low rectal temperature <102.2 degrees.

Treatment: Move to shaded area, monitor vitals, elevate legs above the heart, cool the skin, rehydrate.

Heat exhaustion: Inability to effectively exercise in the heat with a core temperature below 105 degrees and absence of organ damage, or significant central nervous system (CNS) dysfunction.

Symptoms: Excessive fatigue, syncope, or collapse with minor cognitive change, weakness, dizziness, headache, vomiting, nausea, low blood pressure or impaired muscle coordination.

Treatment: Remove excess clothing/equipment, move to cool/shaded area, monitor vitals, elevate legs above heart, and fluid replacement (IV).

Exertional heat injury: Moderate to severe heat illness with organ and tissue injury due to sustained high body temperature but not higher than 105 degrees.

Symptoms: Lack of profound CNS dysfunction, very dark (cola-colored) urine, severe muscle pain and abnormal blood chemistry levels.

Exertional heat stroke: Neuropsychiatric impairment and a core body temperature above 105 degrees. The thermoregulatory system becomes overwhelmed due to excessive heat or inhibited heat loss. The most severe heat illness.

Symptoms: Core body temperature above 105 degrees and CNS dysfunction.

Treatment: Lower core body temperature below 102 degrees within 30 minutes of collapse, immerse athlete’s trunk and extremities in a tub of cold water, continuous monitoring of vitals and core temperature, remove excess clothing once immersed, fluid replacement (IV), and transport to hospital via EMS once core body temperature is reduced to 102 degrees.

For more information about athletic training, click here for the National Athletic Trainers’ Association website. Information provided by the NATA Position Statement: Exertional Heat Illnesses.

Travis Turner has been an assistant athletic trainer with the Houston Texans since 2015. Prior to that, he served as a seasonal athletic training intern with the Texans and Los Angeles Rams. He earned his BS from Texas Lutheran University and MS from West Virginia University.