Be Aware of Heat Illnesses

Chris L. Wells, PhD, PT, CCS, ATC

Heat illnesses are commonly associated with athletic competition in hot, humid weather, but can fall upon a spectator as well. If the body’s ability to cool itself is insufficient or fails it leads to an increase in body temperature. Heat illnesses can be classified into three general categories: heat cramps, heat exhaustion and heat stroke. Risk factors for heat illnesses include: age (children and adults over 50), history of a chronic disease, poor acclimation, poor sleeping habits, intensity of exercise, recent illness, poor physical conditioning, and medications including diuretics, hypertensive medications, antihistamines, and antidepressants to name a few.

Under normal conditions the body generates heat during exertion and has an effective mechanism for cooling itself. The body’s core temperature is dependent upon the environmental climate and the internal metabolic rate or heat. Environmental factors include ambient temperature, humidity, and clothing (see Figure 1 for the risk related to the heat index). When temperature increases the body increases the rate of sweating and the blood flow to the skin to dissipate body heat.

Everyone should recognize the signs and symptoms of dehydration. These can include thirst, sweating, transient muscle cramps, fatigue, general discomfort, flushed skin, weariness, dizziness, nausea and vomiting, headache, and decrease in performance. The key things to do to prevent dehydration and reduce your risk of heat illnesses are to drink to replace fluids throughout the day, monitor the color of your urine (if it is getting darker than usual and there is a decrease in volume, you are likely dehydrated), and rest in a cool place between events.

Heat cramps are caused by either too little or too much fluid intake that leads to a decrease in the body’s sodium level. Athletes can make two mistakes: one the athlete can consume too much water while not replacing electrolytes like sodium, potassium, and magnesium through sports drinks and proper nutrition. Or the athlete does not consume enough fluids to replace what volume is lost in sweating, urine and stool production.
Signs and symptoms of cramps include the same signs and symptoms of dehydration as well as fatigue, transient muscle cramps, and sweating.

Treatment for cramps includes stopping the activity, replacing the fluids, which should be a water and sports drink mix. It is recommended to make a mixture of 1/2 to 2/3 water to 1/2 to 1/3 sports drink. Gentle massage and stretching will also decrease the muscle cramps.

Heat exhaustion is the inability to continue exercising in association with dehydration, excessive sweating, fatigue, and sodium loss. Exhaustion is related to either the depletion of water or the depletion of sodium. Exhaustion related to water depletion is commonly associated with advanced age and medications. Sodium depletion exhaustion is commonly related to poorly conditioned athletes and hyperhydration. Signs and symptoms include dehydration, body temperature less than 104° F, dizziness, GI distress, persistent muscle cramps, cool clammy skin, chills, weakness, change in mental status, and hyperventilation. Heat exhaustion can progress to heat syncope where there is a loss of blood pressure leading to the decrease of blood the heart can pump to the brain. Fainting commonly occurs as well.

Treatment for exhaustion begins with recognition of signs and symptoms. Ideally the athlete’s rectal temperature should be monitored. The activity should be stopped and the athlete should be removed from the heat, remove clothing to improve evaporation of the sweat, cool the athlete with fan or ice bag placed on back of the neck, axilla, and groin areas, and replace fluids. The athlete should be examined by a physician to determine if intravenous fluids are needed and to obtain clearance to return to competition.

Heat stroke is the most serious of the heat illnesses and is considered a medical emergency. The body’s ability to dissipate heat has failed and the body’s temperature is elevated (≥ 104° F). Signs and symptoms include what has been mentioned above for exhaustion and also include marked changes in mental status (delirium, hysteria or a loss of consciousness), hot and wet or dry skin, rapid heart rate and low blood pressure.

Treatment for heat stroke begins with a means to rapidly reduce the body’s temperature by either submerging the body in cold water, or removing clothing, placing ice bags over large blood vessels (neck, axilla and groin). Heart rate and blood pressure should be monitored closely. Finally, the medical emergency system (911) should be activated so the athlete can be transported to the hospital for more advanced care.


  1. Train for your sports, the higher your fitness level the less likely you will experience a heat illness. Spectators, increase your walking or other exercise interest.
  2. Talk to your transplant team about any fluid restriction you may need to follow. It is advised to begin to increase your fluid intake at least a couple of weeks before the sporting event to improve your body’s ability to utilize the fluid for heat dissipation.
  3. Slowly increase your training in the weather conditions in which you will be competing.
  4. Select loose fitting, light color clothing that wicks sweat away.
  5. Pre-hydrate (increase your fluids the day of your event). Avoid alcohol and caffeinated beverages. Once again it is recommended to drink a mixture of water (1/2 to 2/3) and a sports drink (1/2 to 1/3). Drinking too much sport drinks can lead to GI distress.
  6. Drink throughout the Games. If you become thirsty, you are already dehydrated and at increase risk of developing a heat illness.
  7. Eat well-rounded meals and increase your fluid intake at meals.
  8. Sleep well.
  9. Rest between events in the shade or out of the heat.
  10. Recognize the signs and symptoms of heat illnesses.

 Beyond caring for skin blisters and abrasions, the most common reason athletes and spectators will seek out medical attention will be due to a heat illness. So make sure to prepare yourself properly, learn the signs and symptoms to watch for, and seek medical attention early if you are not feeling well.

Figure 1: Risk of Heat Illness from Medicine Science and Sports Exercise: (1996) 28: i –vii.


Binkley, HM, et al. Journal of Athletic Training. (2002) 37:3; 329-343.
Wexler, RK. American Family Physician. (2002) 2307-2320.
Armstrong, LM. Medicine Science and Sports Exercise (2007): 556-573.
Glazer, JL. American Family Physician (2005) 2133-2142.

Chris L. Wells has spent 12 years helping athletes prepare for the Transplant Games and will attend his fifth Games this summer.

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©2014 National Kidney Foundation. All rights reserved. This material does not constitute medical advice. It is intended for informational purposes only. Please consult a physician for specific treatment recommendations.