Basic Heat Illness Information

Exertional Heat Stroke (EHS)

• Severe condition characterized by core temperature > 40°C (104°F), central nervous system (CNS) dysfunction, and multiple organ system failure induced by strenuous exercise, often occurring in the hot environments ^3-4

• EHS is a medical emergency and can be a fatal condition if the individual’s core body temperature remains above 40°C for an extended period of time without the proper treatment³

Signs and Symptoms

Core body temperature > 40°C, tachycardia (increased heart rate), hypotension, sweating, hyperventilation, altered mental status (disorientation/confusion), dizziness, irrational behavior, irritability, headache, inability to walk, loss of balance/muscle function, vomiting, diarrhea, collapse, seizures, and coma. ^1-4

 

It is recommended when performing temperature assessment, ONLY a rectal temperature should be used with a hyperthermic individual; it is the only method for an accurate and immediate temperature assessment if an ingestible thermometer was not used. Other temperature devices (tympanic, oral, skin, or axillary) may give false readings. ^{1-2, 4}

 

Predisposing Factors

Vigorous activity in hot-humid environment (usually lasting longer than 1 hour), lack of heat acclimatization, poor physical fitness, dehydration, sleep deprivation, fever or illness, warrior mentality, high pressure to perform and heavy equipment/uniform. ^1-2

 

Treatment

Rapid and aggressive whole-body cooling is the key to survival of exertional heat stroke

• The fastest way to decrease body temperature is to remove excess clothing and equipment and immerse the body into a pool or tub of cold water -- cold water immersion -- (35-59°F) ^3-4
• The individual should be immersed within 30 minutes for optimal results and submersed until rectal temperature is below 38.3-38.9°C (101-102°F) ^1-4
• After cooling, the individual should then be transported to a medical facility for monitoring of possible organ system damage ^2-4
• For more information please see KSI Cold Water Immersion Cooling Guidelines

Return-to-Play

Return to activity should be determined by a physician. Individuals should avoid exercise for a minimum of one (1) week after release from medical care. Individuals should start with a gradual return to activity under the supervision of a qualified health professional. ^1-2

 

Prevention

To prevent EHS, individuals should adapt to exercise in the heat gradually over 10-14 days (acclimatization) by progressively increasing duration and intensity of work, incorporate rest breaks, minimize amount of equipment/uniform worn in hot-humid weather, provide and encourage adequate fluid consumption. ^1-3

*IT IS IMPORTANT TO REALIZE THAT EHS IS DIFFERENT FROM CLASSICAL HEAT STROKE, WHICH USUALLY AFFECTS THE ELDERLY AND CHILDREN DURING PROLONGED ENVIRONMENTAL HEAT EXPOSURE

• View KSI Exertional Heat Stroke Survival Kit for further assistance.

Heat Exhaustion

• Most common heat-related condition observed in active populations ²

• Defined as the inability to continue exercise due to cardiovascular insufficiency and energy depletion that may or may not be associated with physical collapse ^1-4

Signs and Symptoms

Fatigue, weakness, heavy sweating, dehydration, sodium loss, fainting, dizziness, irritability, headache, hyperventilation, nausea, vomiting, decreased urine output and blood pressure, decreased muscle coordination, and core temperature between 36-40°C ^2-4

Obtain a rectal temperature and assess central nervous system function to rule out exertional heat stroke (< 40°C). ^{1, 3}

 

Predisposing Factors

Exercising in hot and humid environment (air temp > 33°C), inadequate fluid intake (dehydration), and body mass index > 27kg/m ²

 

Treatment

To treat exertional heat illness, move individual to cool/shaded area, remove excess clothing, elevate legs to promote venous return, cool with fans, rotating ice towels, or ice bags. Individual should respond quickly to treatment, if not heat stroke could be suspected. Provide oral fluids for rehydration. ^1-4

 

Return-to-Play

Returning to activity the same day of episode is not prudent or advised. Individuals should wait 24-48 before returning to activity and should gradually increase intensity and volume of exercise ^{1-2, 4}

 

Prevention

To prevent EHI, individuals should adapt to exercise in the heat gradually -- acclimatize -- over 10-14 days by progressively increasing duration and intensity of work ^{1, 3}

Heat Syncope

• Also known as orthostatic dizziness.

• Refers to a fainting episode that someone can experience in high environmental temperatures, usually during the initial days of heat exposure. ^{1, 3}

Signs and Symptoms

Dizziness (vertigo), weakness, tunnel vision, pale or sweaty skin, nausea, decreased pulse rate, and normal exercising rectal temperature. ^{1, 3}

 

Predisposing Factors

Standing for long periods of time, usually wearing a uniform, immediately after cessation of activity, or after rapidly standing from prolonged resting or sitting posture. ^{1, 3}

 

Treatment

• Move person to shaded/cool area, monitor vital signs, elevate legs to promote venous return, and rehydrate ³
• Individuals who experience heat syncope will recover relatively quickly, within 10-15 minutes. ³

Return-to-Play

An athlete may return to play once his/her symptoms have resolved and any other medical conditions have been ruled out.  Athletes should attempt to rehydrate as necessary.

 

Prevention

Heat syncope often occurs in individuals that are unacclimatized to the heat (the body is not used to increased environmental temperatures) therefore, individuals should adapt to exercise in the heat gradually acclimatize over 10-14 days by progressively increasing duration and intensity of work ^{1, 3}

Heat Cramps (Exercise-Associated Muscle Cramps)

• Defined as an acute, painful, involuntary muscle contraction usually occurring during or after intense exercise, often in the heat, lasting approximately 1-3 minutes ^1-4

• Often occurs in the muscles of the legs, arms, or abdomen ²

Signs and Symptoms

Dehydration, thirst, sweating, transient muscle cramps, and fatigue ^3-4

A precursor to the initial onset of cramps involves twitches or fasciculations ^1-2

 

Predisposing factors

Exercise-induced muscle fatigue, excessive body water loss and excessive sodium loss (sweating) ^{2, 4}

 

Treatment

To treat heat cramps: rest, stretch and massage with muscle in full length position, and provide fluids or food with salt content such as a sports drink ^1-4

 

Return-to-Play

Individuals can return to play usually during the same exercise session with rest and fluid replacement ^1-2

 

Prevention

To prevent heat cramps, individuals should maintain fluid and salt balance, especially when exercising in the heat and sweat losses are great.

Supplemental/extra sodium may be needed. ^1-2

Exertional Sickling

Sickle cell trait (SCT) is a genetic variation and usually benign. About 1 in 12 African Americans and about 1 in 2,000 to 1 in 10,000 Caucasians have SCT.  While not the same as sickle cell anemia, SCT can cause exertional sickling also termed explosive rhabdomyolysis, during intense exercise.  Exertional sickling occurs when the sickled red blood cells “log-jam” in the blood vessels, which can cause fatal ischemic/exertional rhabdomyolysis. ^{5, 6}

 

Signs and Symptoms

Usually occurs in the first few minutes of high intensity exercise

Reports of increasing pain and weakness in the muscles, especially in the lower extremity.  This might be perceived as “cramping” but is much more diffuse than heat cramps.  Heat cramps normally cause the athlete immediate acute pain that immobilizes them while exertional sickling is more of an strong ischemic pain. ^{5, 6}

Legs become weak and unstable, athletes normally collapse and most often are mistaken for a case of heat stroke, heat exhaustion or heat cramps. ^{5, 6}


Predisposing factors

Heat, dehydration, altitude, asthma, high intensity exercise with few rest intervals ^{5, 6}

 

Treatment

Give supplemental oxygen if possible ³

Cool the athlete, if needed

Call 911 and explain to doctors the urgent care needed to prevent explosive rhabdomyolysis ^{5, 6}


Return-to-Play

Blood samples must return to normal (specifically creatine kinase and liver/renal markers. ^{5, 6}

In mild and well-managed cases athletes may be able to return to play the next day, in severe cases, extended stay in a hospital may be warranted and return to play may take weeks, if at all. ⁵


Prevention

Sickle cell trait is genetic. Athletes with a family history of sickling should be tested.

Those with known SCT or a high probability of SCT should be treated as follows: ^{5, 6}

Allow a greater time for build up in training

Provide breaks as needed or longer “breathers” between intervals and allow SCT athletes to set their own pace

No all-out exertion lasting longer than 2 minutes

Have supplemental oxygen ready if at high altitudes

Be aware of the signs and symptoms and tell the athlete to report them immediately if they begin to experience these

Return to Top

 

References:

1. Armstrong, LE.  2003. Exertional Heat Illnesses.  In Exertional Heatstroke: A Medical Emergency, edited by Douglas J. Casa and Lawrence E. Armstrong, 29-56.  Illinois: Human Kinetics Publishers, Inc.
2. American College of Sports Medicine Position Stand; Exertional Heat Illness during Training and Competition. Medicine & Science in Sports & Exercise. 2007; 556-572
3. Binkley, H., Beckett, J., Casa, D.J., Kleiner, D.M., Plummer, P.E. 2002. National Athletic Trainers’ Association Position Statement: Exertional Heat Illnesses.  Journal of Athletic Training.37 (3):329-343.
4. Inter-Association Task Force on Exertional Heat Illness Consensus Statement
5. Eichner, RE.  Sickle Cell Trait.  J of Sport Rehab. 2007; 16: 197-203.
6. Inter Association Task Force Consensus Statement: Sickle Cell Trait and the Athlete. 2007
   

Return to Top