Hydration and Heat Illness

Heat-related deaths and illness are preventable, yet annually many people are affected by heat related illness. According to the Centers for Disease Control, from 1979 to 1999, excessive heat exposure caused 8,015 deaths in the United States. During this period, more people in this country died from extreme heat than from hurricanes, lightning, tornadoes, floods, and earthquakes combined. In 2001, 300 deaths were caused by excessive heat exposure.

Athletes are at risk for heat-related illness when their bodies are unable to properly cool themselves during physical activity.  The risk of heat illness increases with rising temperatures and rising humidity.   The body normally cools itself by sweating. But under some conditions, sweating just isn't enough, causing an athletes body temperature to rise rapidly.

Several factors affect the body's ability to cool itself, such as:

  • Weather: when the humidity is high, sweat will not evaporate as quickly, preventing the body from releasing heat quickly.
  • Age: children have lower sweat rates, higher heat production, and require more time to acclimate to heat.
  • Larger athletes:  more mass means more energy production and body heat. Fewer sweat glands per surface area, along with additional fat, insulates the body and keep heat internalized.
  • Restrictive clothes and gear limits heat evaporation and increases insulation.
  • History of heat illness

Other conditions related to risk include obesity, fever, dehydration, heart disease, mental illness, poor circulation, sunburn, and prescription drug and alcohol use.

Because heat-related deaths are preventable, it is vital coaches are aware of who is at the greatest risk and what actions can be taken to prevent a heat-related illness or death.

Prevention Tips

  • Drink plenty of fluids.  Be sure your athletes increase their fluid intake, regardless of activity level during hot or humid weather.
  • Choose lightweight, light-colored, loose-fitting clothing. 
  • If you must be outdoors, try to limit your practices to morning and evening hours. Try to rest often in shady areas.
  • If your athletes are not accustomed to exercising in a hot environment, start slowly and pick up the pace gradually.
  • Allow your athletes to adjust to the environment.  An athlete’s tolerance for heat will improve over time, if you limit their physical activity until they become accustomed to the heat.
  • No or little acclimation to heat. High intensity training in hot humid environments without allowing the body a period of adjustment is a common cause of heat illness.

Hydration Tips for Coaches

  • Don't wait until they are thirsty to drink. During heavy exercise in a hot environment, it is recommended drinking two to four glasses (16-32 ounces) of cool fluids each hour.  Avoid liquids that contain alcohol, or large amounts of sugar—these actually cause you to lose more body fluid. Also avoid very cold drinks, because they can cause stomach cramps.
  • Record your athlete’s body weight before and after activity. Compare your athlete’s pre-activity body weight to his or her post-activity body weight.  If post-activity weight is less than pre-activity weight, your athlete is not drinking enough fluids while active. A loss of as little as 1 percent of body weight can cause a decrease in performance.  Because studies have proven that children replace less of their fluid losses when drinking water, you may want to offer a flavored sports drink to increase the amount of fluid your child consumes.  One pound of body weight equals 16 oz. of water.


Dehydration occurs when the body looses too much fluid.  Dehydration impairs athletic performance whenever body fluid level falls below 98% of normal. The primary cause of dehydration is sweat loss, an essential body process which facilitates the release of body heat into the environment. When athletes don’t replace what they lose in sweat, the physiological function of the body’s heat management system is compromised, placing both the athletes’ performance and physical well-being at risk.

Heat Exhaustion
This is a serious form of heat illness, but not as severe as heat stroke.

Heat Stroke
The most severe heat-related illness, heat stroke can permanently impair or kill an untreated athlete. Symptoms are similar to heat exhaustion, plus hyperthermia (high body temperature) whereby the core body temperature can be higher than
105.8 degrees. This can lead to conditions such as convulsions, heart attacks, coma, stroke, liver and kidney damage, or blood clots in the lung. If an athlete is not immediately immersed in ice water, he/she can die or suffer permanent physical damage.


Muscle Cramps
Loss of Performance   
Heat Exhaustion      
Rapid Pulse  
Cold, clammy skin  
Heat Stroke
* Medical Emergency  
Irrational Behavior 
Hot, dry skin   
Confused or disoriented 
Dangerously high temperature


Stop activity     

Heat Exhaustion      
Replace fluids (re-hydration is critical)

Rest in a cool, shaded area until all symptoms have passed.

If dizziness continues, lie the athlete down, elevate  their legs, and seek medical attention.

Heat Stroke
Get out of sun and seek immediate medial attention. This is an emergency, call 911.

Cool immediately using ice baths, ice bags, or whatever  is available for you to use.


* REMEMBER:  Athletes can still be experiencing heat stroke even if most symptoms are absent.  Seek medical attention immediately at the first sign of serious or unusual symptoms.