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Heat Stress and Heat Stroke

With the crazy hot summer we've had so far, combined with the latest evidence showing that it is crucial to our health to be active, it seems prudent to discuss how to keep cool in this ridiculous ridiculous heat.

As an aside, most of the worlds scientists agree that the global temperature is continuing to rise, so our summers stand to continue getting hotter.  So this will become more and more important to know in the future.

Heat Exhaustion

Heat exhaustion is a heat-related illness that can occur after you've been exposed to high temperatures, often when combined with physical activity.  It is a combination of elevated body temperature and dehydration.  Heat exhaustion is not as severe as Heat stroke, and is characterized by the following symptoms:

  • exhaustion
  • dizziness
  • nausea
  • headache
  • excessive sweating
  • decreased urine output

If you have heat exhaustion, mild confusion is also a possibility.  Someone with Heat exhaustion should respond well, and reasonably quickly to interventions such as:

  • removing the person to a cooler area
  • drinking plenty of fluids (avoiding caffeine and alcohol)
  • removing excess clothing
  • other cooling methods such as a cool towel, or a fan

Heat Stroke

Heat stroke is different from Heat Exhaustion in that it is a life-threatening emergency.  It can be identified by a marked change in a persons mental status.  It is caused in the same way as Heat Exhaustion, and by not reacting appropriately to the signs and symptoms above, Heat stroke can develop.  At the onset of Heat stroke, we see the following symptoms:

  • increased heart rate
  • increased breathing rate
  • decreased sweating
  • decreased level of responsiveness

When someone has heat stroke, the body's normal mechanisms for shedding excess heat are overwhelmed.  The defining characteristic of heat stroke that differentiates it from heat exhaustion is a decreased level of responsiveness, a person may seem drunk or very confused.  If Heat stroke is left untreated, it can result in death.  If you are dealing with someone who you think is suffering from Heat stroke, emergency services should be activated immediately.  Treatments as for Heat exhaustion can be applied while you are waiting for help to arrive.


To maximize tolerance to hot environments, a program for heat acclimatization can be used.  If you are planning an outdoor, active trip to a hot environment, you can improve your heat acclimatization by exercising daily in the heat for limited periods of time (about an hour), for several days and preferably up to a week.

Of course, for day-to-day prevention, keep an eye on the weather, and exercise at times when it isn't quite so hot outside, such as early morning, or late evening.  You can also plan to exercise with a buddy, so you can help keep an eye on each other.  Make sure to prepare yourself by drinking plenty of water, and replacing your electrolytes.  You can also take a cold shower to cool off when you are all finished.


  1. Outdoor Emergency Care - 5th Ed by McNamara, Johe and Endly.
  2. Heat Exhaustion - WebMD -

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