To You Health
Body temperature is raised by environmental conditions and
exercising muscle. Cooling is accomplished primarily by the
evaporation of sweat. The most important barrier against
effective cooling is humidity. Humidity is not your friend The
rate of sweating is higher in humid conditions but the cooling
is less. The reason is that because the air is already very
saturated with water, sweat can't evaporate. Sweat that beads up
and rolls off doesn't function in the cooling process. However,
this "futile sweat" does deplete the body of vital water and
salt.
As dehydration progresses cooling becomes more difficult.
Performance drops and heat injury becomes a real threat.
Deaths have occurred when the air temperature was less than 75
degrees F (24 degrees C) but the relative humidity was above 95%.
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 blurred into a
continuous spectrum.
Heat cramps are due to muscle spasms and often occur in the
arms, legs, or abdomen. They are thought to be caused by
dehydration and loss of salt and other electrolytes.
Heat exhaustion is due to more profound loss of water and
electrolytes. It is characterized by generalized weakness,
headache, dizziness, low blood pressure, elevated pulse, and
temperature elevation as high as 104 degrees F (40 degrees C).
Both can usually be treated by moving out of the sun, drinking
fluids, and eating salty food.
Heatstroke is a life threatening condition and represents
severe dehydration, high body temperature, and a shut-down of
the cooling mechanisms. The patient may be delirious or
comatose, and half of the victims have stopped sweating. The
pulse is rapid and weak, the blood pressure is low and body
temperature is greater than 105