by Mark Jenkins, M.D.

This article is a continuation of the "Performance Shop" column in the August 2001 issue of Runner Triathlete News. For more details on combatting the summer heat and humidity, please pick up a copy of the August 2001 edition of Runner Triathlete News.

There are three stages to heat illness -- heat cramps, heat exhaustion, and heat stroke (listed in order of increasing severity). Often the border between them is fuzzy.

Heat cramps are due to muscle spasms and often occur in the arms, legs, or abdomen. These are thought to be caused by dehydration and/or salt loss.

Heat exhaustion is due to more profound water (and salt) loss, which significantly impairs cooling. Heat exhaustion is characterized by generalized weakness, headache, dizziness, low blood pressure, elevated pulse, and elevated temperature, as high as 104 degrees F (40 degrees C). Moving out of the sun, drinking fluids, and eating salty food are useful treatments for both forms of heat illness, but medical care may be needed. If in doubt, get checked out.

Heatstroke is a life-threatening, medical emergency characterized by severe dehydration, high body temperature, and a complete shut-down of the cooling system. Affected individuals may be delirious or comatose, and approximately half have stopped sweating. The pulse is rapid and weak, blood pressure is low, and body temperature is greater than 105 F (40.6 C). Core temperature may reach as high as 110 F (43 C). (Note: oral temperature readings are notoriously inaccurate in these circumstances). Damage to vital organs (brain, heart, lungs, kidneys) is imminent. Sometimes despite the best medical care, death occurs.

Emergency roadside treatment of heatstroke

* Call 911

* Remove the patient from direct sunlight

* Remove the patient's clothing

* Wet the body surface and fan to promote air movement and evaporation

* Rub the skin with bags of ice