Dr. Gabe Mirkin's Fitness and Health E-Zine
May 22, 2011
Heat Stroke
The most likely cause of death during hot weather sports
is heat stroke, when the body temperature rises so high that it
cooks the brain (Medicine and Science in Sports and Exercise, July
2008). Nobody should ever die of heat stroke because your body
sends you warning signals as your temperature rises. Those most
likely to suffer heat stroke are those who have arteriosclerosis,
are overweight or are in poor shape. The treatment for a person
who collapses from heat stroke is immediate immersion in cold
water.
In 1965, I almost died from heat stroke in an unimportant
local race in Arlington, Virginia. I am still embarrassed by the
stupidity that I showed when I ignored all of the warning signs as
my temperature continued to climb.
SIGNS OF IMPENDING HEAT STROKE
First your muscles are affected, then your circulation
and then your brain. As your temperature starts to rise, your
muscles feel like a hot poker is pressing against them.
It is normal for intense exercise to make your muscles
burn, but hard exercise does not cause painful burning that feels
like fire. Furthermore, the burning of hard exercise is relieved
by slowing down. The muscle burning of impending heat stroke does
not go away when you slow down.
As your temperature rises further, the air that you
breathe feels like it's coming from a furnace and no matter how
rapidly and deeply you try to breathe, you can't take in enough
air. When you exercise intensely, you can become very short of
breath, but the air you breathe will not burn your lungs. Burning
in your lungs, not relieved by slowing down, signals impending
heat stroke.
When you feel that the air is so hot that it burns your
lungs, stop exercising. This sign means that your heart cannot
pump enough blood from your exercising muscles to your skin, so
heat is accumulating rapidly and your temperature is rising
rapidly. Your temperature is now over 104 and continuing to
exercise will raise your body temperature even further and it will
start to cook your brain.
Your head will start to hurt, you'll hear a ringing in
your ears, you may feel dizzy, you may have difficulty seeing and
then you will end up unconscious. Your temperature is now over 106
and your brain is being cooked just as the colorless portion of
an egg turns white when it hits the griddle.
WHEN DOES HEAT STROKE OCCUR?
Almost all cases of heat stroke occur when you suddenly
increase the intensity of your exercise, such as the finishing sprint
of a long distance running or cycling race, or an intense run down
the field in soccer.
HOW BODY TEMPERATURE CAN RISE UNCONTROLLABLY
An excessive rise in body temperature is caused either by
producing too much heat or by inability to dissipate the extra
heat. When you exercise, almost 80 percent of the energy that is
used to drive your muscles is lost as heat. That means that the
harder you exercise, the more heat you produce.
During exercise, more than 70 percent of the energy used
to drive your muscles is lost as heat, so you heart has to pump
extra blood from your hot muscles to your skin where you sweat.
Sweat evaporates and cools your skin to dissipate the heat. The
harder you exercise, the more heat your muscles produce. Everyone
who exercises, particularly in hot weather, has to sweat to keep
the body temperature from rising too high.
DRUGS CAN CAUSE HEAT STROKE
Heat stroke is more likely to be caused by inability to
get rid of heat than by producing too much heat. Stimulants such
as amphetamines or cocaine can kill athletes by preventing them
from getting rid of heat by blocking sweating and blood flow to
the skin. A single nasal dose of cocaine can block blood flow to
the skin and sweating, to prevent a person from cooling his own
body (Annals of Internal Medicine, June 4, 2002).
TREATMENT
When a person passes out from heatstroke, get medical
help immediately. Any delay in cooling can kill him. Carry the
victim rapidly into the shade and place him on his back with his
head down and feet up so blood can circulate to his brain. Cool
him by pouring on him any liquids you can find or spray him with a
hose. It doesn't make any difference what you pour on him: milk,
Coca Cola, beer, or anything else. Evaporation of any liquid
cools. As you cool him, he will then wake up and talk to you and
act like nothing has happened. While he's sitting or lying there,
his temperature can rise again and he can go into convulsions or
pass out again, so he must be watched for at least an hour.
An athlete or exerciser who passes out from overheating
should be immersed in cold water immediately to prevent brain and
multiple organ damage. However, a heart attack can also cause a
person to pass out and this should not be treated with cold water
immersion. Therefore always get medical help immediately when you
see a person pass out during exercise.
PREVENTION
Heat stroke is caused by continuing to exercise intensely
in spite of all the warning signals that the body presents.
Dehydration also increases your risk for heat stroke.
When you compete in sports, you need to drink before you feel
thirsty, because you slow down and lose power long before you have
any signals to tell you that you are dehydrated. In warm weather,
trail runners raced 12 km (7.2 miles) much faster when they took
fluids (Journal of Athletic Training, March-April 2010). With
fluids, they averaged 53.1 minutes compared to 55.7 minutes
without fluids. Immediately after the race, the dehydrated runners
had signs of greater body stress such as heart rates six beats per
minute faster and intestinal temperatures .22 degrees C higher.
THIRST IS A LATE SIGN OF DEHYDRATION
You won't feel thirsty during exercise until you have
lost between two and four pints, or two to four pounds. Thirst is
a very late sign of dehydration. You sweat during exercise, and
since sweat contains much less salt than your blood, you lose far
more water than salt during exercise. As blood salt levels rise
higher and higher, they trip off special osmoreceptors in your
brain to tell you that you are thirsty. Since it takes a long time
for blood salt levels to rise high enough to tell you that you are
thirsty, you will be severely dehydrated long before you feel
thirst.
YOU NEED MORE SUGAR IN HOT WEATHER
During long sports competitions, you need to take sugar
as well as fluid because running out of sugar stored in muscles
slows you down. The only mineral that you need to replace during
exercise is common table salt. Water or your favorite drink plus
food containing sugar and salt are just as effective as any sports
drink to maintain endurance and prevent heat exhaustion. The best
exercise drink is the one that tastes best to you, because that's
what you will drink the most (International Journal of Sport
Nutrition and Exercise Metabolism, January 2002).