Heat-Related Illness and Hydration

As the summer season continues on, heat and humidity remain an issue of concern. With activity in inclement weather, heat cramps, dehydration, and impaired performance are all things you may have already experienced this summer. The purpose of this article is to highlight some key points about managing heat-related illness, rules for proper hydration, and recognizing unsafe environmental factors.

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Examples of Heat-Related Illness

  1. Heat Cramps: spasm or cramping of muscle that often occurs in unconditioned individuals or athletes not acclimated to participating in hot, humid environments.  Commonly caused by an imbalance between water and electrolytes, excessive sweating, sodium depletion, or a spinal neural mechanism.
  2. Heat Exhaustion: characterized by sudden, extreme fatigue as the over-exerted body attempts to supply blood to the brain, exercising muscles, and skin.  Common causes include: prolonged sweating, inadequate fluid and/or electrolyte replacement, diarrhea, or intestinal infection.  If improperly managed, heat exhaustion can progress to heat stroke.
  3. Exertional Heat Stroke: MEDICAL EMERGENCY that represents the failure and shutdown of the body's thermoregulatory system.  After this shutdown, the core temperature continues to rise placing internal organs, most importantly, the brain at risk.  If rapid cooling does not occur, all of the body's systems will begin to fail and death can occur within 20 minutes.

Management and Prevention of Heat-Related Illness

  • Wear clothing that allows heat loss and sweat evaporation
  • Reschedule exercise for a cooler time of day
  • Relocate exercise to a shady, breezy site or indoors with fans and/or air-conditioning
  • Reduce exercise intensity and add rest breaks to maintain the same target heart rate as normally prescribed


Maintaining proper hydration plays an integral role in preventing heat illness and performing at an optimal level. Even mild dehydration impairs the body’s ability to regulate core temperature and may compromise performance. This becomes even more important in hot and humid environments. Fluids should be readily accessible and athletes should be reminded to drink before, during, and after activity. Adequate hydration is the most effective way to decrease the risk of heat-related illness.

How to Stay Hydrated

Using thirst as a guideline of when to drink is not always sufficient for the athletic population. The National Athletic Trainers’ Association (NATA) believes that this advice is misleading for athletes; and, can increase the risk of dehydration and heat illnesses. Research shows that relying on thirst may cause athletes to underestimate fluid needs and replace on average only about 50% of the fluid lost in sweat. Therefore, the NATA recommends athletes drink on a schedule based on their individual sweat rate, regardless of thirst, to ensure that they are replacing sweat losses.

Environmental Factors

Along with proper hydration, recognizing unsafe environmental factors is key in preventing heat-related illness. The Heat Stress Index highlights that despite cooler temperatures, relative humidity can place athletes at increased risk for dehydration and subsequent heat illness.  Based on the combination of heat and humidity, coaches may need to alter practice time or location, increase water breaks, modify exercise intensity, and monitor all athletes for early signs of heat-related illness.


As you can see, exercising in the summer months can have serious medical implications.  However, adequate hydration, proper clothing, checking relative humidity in addition to temperature, and recognizing early signs and symptoms of heat illness are all ways to prevent dehydration and avoid serious health complications.

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About The Author

Julianne Peacock DPT, ATC is a Physical Therapist/Athletic Trainer at the IBJI Glenview facility.  Julianne received her Bachelor of Arts in Athletic Training from Purdue University and her Doctorate of Physical Therapy from Washington University in Saint Louis.  Julianne has a passion for sports and enjoys helping her patients progress back to their favorite sport or activity by incorporating sports-specific exercises into their rehabilitation programs.


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