IT'S AS CLOSE as most of us will ever come to getting cooked.
The air-conditioned office, mall or supermarket has left us a
bit chilly. We step outside into the peak of a quintessentially
hot, humid St. Louis summer day.
A wall of heat rushes forward, delivering a full-body blow. We
stagger to the car, open the door and stumble in.
An even more devastating wave of heat consumes us, like fire
snapping up a dry leaf. And the seat - after baking in the sun -
sizzles beneath us.
That sudden jolt of heat - a common occurrence this time of
year - is what scientists call "the supermarket syndrome."
"It feels like you're walking into a blast furnace," said
Frederick H. Rohles, emeritus professor of psychology at Kansas
State University. "Add to it the 120-degree temperature in the car,
and you'd think you were going to cook."
But that wilting feeling we get during the summer when we
constantly shift between air-conditioning inside and heat outside
is a temporary problem, say Rohles and other experts on how the
body adapts to heat.
We may feel a bit drained, or even dizzy. But the toll on the
body is minimal and there's little health risk for the normal,
healthy adult - unless we engage in strenuous activity in the heat.
"It's more impressionistic than physiological," said Thomas
Adams, a physiologist at Michigan State University. "A few minutes
after you step outside, you feel good again."
Blood, Sweat And Heat
Like a chameleon, the human body adjusts rapidly as it goes
from air-conditioning to outdoor heat, even though the temperature
can jump 50 degrees or more.
"It's not a major problem," said Rohles, who led studies of
such changes when he directed KSU's Institute for Environmental
Research. "Sure you're going to be uncomfortable - maybe for as
long as 10 minutes. But the human body has a fabulous adaptation
process that will adjust to whatever the environment is."
If everything's in working order, the body rarely varies more
than 2 degrees from its normal core temperature of 98.6 degrees.
Two of the most important tools it uses to get rid of excess heat
are blood and sweat.
The first line of defense in the battle against heat is blood,
the largest body of water in our bodies. The blood circulatory
system acts as a temperature-control duct, carrying heat away from
the brain and muscles and delivering it to the skin.
In the heat of summer, the body pumps up its blood supply to
better handle the heat. Until this adjustment, mowing the lawn and
shopping can be a strange experience early in the summer, Adams
said. Even though body temperature remains normal, the warm air
triggers a reflexive surge in blood flow to the skin. That, in
turn, causes a drop in blood pressure.
"This presents a special problem for humans because the brain
is at the highest point in the body and is the first to experience
the effects of decreased blood pressure," Adams said. The result
for some people: dizziness, fatigue, lightheadedness and sometimes
After the blood delivers heat to the skin, the heat is carried
away into the air by physical processes with names like convection,
conduction and radiation. But when the air temperature exceeds the
skin temperature, sweat glands take over.
Between 3 million and 5 million sweat glands cover the human
body. Their job: put moisture on the skin. As the sweat evaporates,
it takes energy away from the skin in the form of heat. That cools
Sweat glands are sturdy organs that function well throughout
life, said Michigan State's Adams, author of "Guidelines for
Surviving Heat and Cold."
These glands can unleash virtual torrents of water. A person
exercising on a hot day can generate 12 quarts of water in a
24-hour period, with bursts of sweating up to 3 quarts an hour. …