*** Maintaining Body Heat ***

Wed Jan 10 09:49:59 1996
Letter  : 8576369    From: Bruce Bowler
Address : bruce_bowler@jhqmac.dot.state.ak.us

                     NOTHING CAN BEAT THE HEAT
      - WATCH BODY TEMPERATURE WHEN WORKING OUTDOORS

                     Opinion Column
                    By Craig Medred
               Daily News Outdoors Editor

Anyone who watched the National Football League playoff games over the
weekend should have learned three important facts about winter survival.
All were beautifully illustrated by the sideline television cameras that
caught the steam pouring off the heads and out the mouths of players coming
off the field.

FACT 1: Large amounts of heat are lost through the head.
"The uncovered head can lose up to one-half of the body's total heat
production at 39 degrees," writes Dr. William W.Forgey in "Hypothermia -
Death by Exposure."

The proportional heat loss from an uncovered head only increases as the
temperatures go down. Think of the head as the body's radiator. Those
football players you watched were trying to avoid overheating despite the
cold. Their radiator was working full force to keep them cool. That caused
all the heat steaming off their bald heads into the frigid air.

When you are working hard in the cold - say running or snowshoeing up a
mountain - you want your radiator to do this. But if you aren't working
hard enough to produce surplus heat, you want to block off the radiator to
save energy to warm the body.

In Interior Alaska, motorists often put a piece of cardboard in front of
their radiator in the winter to stop the flow of air across it and ensure
the car runs warm. The equivalent thing to do with your body is put on a
hat. Your body can take this heat that and shuttle it to other parts of
your body, just as your care heater takes heat from the engine and moves
it to the passenger compartment. Remember the cliche: "If your fingers are
cold put on a hat." Strange as it might sound, it's true.

FACT 2: Cold weather sucks moisture out of your body.
Cold air cannot hold much water. All the water condenses out as frost,
something you might have noticed many times this winter. In this way, cold
air becomes dry air. Dry air speeds the lost of moisture from the body.
Your skin and lips get cracked or chapped as they dry out. Sweat quickly
evaporates from your skin. And a lot moisture is simply blown away during
respiration.

How important is this lost moisture? Very.
"The chronic hypothermia victim is in a dehydrated state," writes Forgey.
"A factor predisposing an individual to dehydration is the dry relative
humidity under cold weather conditions. All air must be warmed to
approximately core temperature and the moisture content of this heated air
raised to nearly 100 percent humidity during respiration. ...
"It is essential to keep up with this (moisture) loss with frequent
replacement during the day on an hourly basis, if possible."

People exercising hard in the cold might want to replace water more often
than that. Skiers, snowshoers, mountain bikers and runners in the Idita
sport competition often set their watches to beep every 20 to 30 minutes
to remind them to drink. Water loss in that race is critical because
dehydration leads to a rapid downturn in physical performance, not to
mention some potentially deadly problems in regulating body temperature.

Scientists at the Natick Army Laboratories say 10 percent dehydration
accounts for a 30 to 40 percent decrease in the body's ability to regulate
heat. There were reasons those football players were sucking down all that
Gatorade.

FACT 3: Exercise keeps you warm.
Football players could pull off their helmets at temperatures of 5 degrees
or colder and stand around comfortably steaming because they had been
exercising strenuously. Their bodies didn't care about the cold because
they were still trying to dump the excess heat generated by hard physical
labor.

The average human at rest produces between 1 and 2 kilocalories of heat
per minute. Start walking at a steady 3 mph across a hard, level surface,
and you will more than double this heat production. Start running or turn
to hike up a steep hill, and you can push the heat production five or ten
times as high. Go up that hill on cross-country skis at top speed, and you
might be able to boost it by as much as 20 times, up to about 20 kilo-
calories per minute.

How much heat is this? Let's put it this way: I have remained comfortable
while skiing in nothing but a layer of polypropylene underwear and wind
garments at 50 degrees below zero. Of course, I was at the time laboring
under a heavy pack and breaking trail through the Alaska Range. Had I been
standing around similarly dressed in these conditions, I would have started
shivering like a wind chime in a hurricane within minutes. The exercise
kept me warm. But there's a catch.

"There are limitations to the amount of purposeful exercise an individual
can accomplish," writes Forgey. "Physical conditioning is the key, as
exhaustion - that is the body's in ability to continue muscular activity
- will readily result in hypothermia. ... Thus physical conditioning is
of utmost importance in preparing for cold stress."
You can produce heat through exercise only so long as you continue
exercising.

A warning is in order here, too. Heavy exercise can increase sweat
production, and heavy sweating can soak clothes, seriously undermining the
efficiency of insulation. These are all things Alaskans should understand,
because if you start to go hypothermic here it is unlikely you will be
able to retreat to the safety of a nice, warm shower in a nice, warm
locker room.

Craig Medred is the Daily News Outdoors Editor and an opinion columnist.

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