How
the human body works. Heat energy always
moves to cold, which is why a radiator works. The heat
energy from the engine is trying to warm up the air as
it travels past the radiator. The body works the same
way to a point. The body has four different ways that
it uses to cool itself: radiation, convection, evaporation
(due to perspiration) and conduction. All of these different
systems work very well to keep the body cool and running
well as long as the environment stays below body temperature,
roughly 95° F. However, when the temperature gets
above 95° the heat energy from the environment starts
flowing to the body because the body is cooler than the
environment. That is except for perspiration which allows
the body to cool despite the hot temperature because when
evaporation occurs, it cools the surface from which it
is evaporating. The body has four different ways to control
its temperature and when the temperature of the environment
gets above 90° to 95° three of those four ways
no longer work. Now add a driver suit and helmet to the
mix, sit behind an engine giving off even more heat and
it can affect even the fittest driver.
What
about just cooling the head? When the
ambient temperature is below 90° the body sends 96%
of the blood to the heart, brain and the other internal
organs and muscles. However, when it is hot the body responds
differently. The body sends almost 50% of the blood to
the skin surface to try to cool the blood through radiation
and to provide water for perspiration. Since the entire
body becomes a radiator you don’t want to cool just
the head, you want to cool as much skin surface as possible.
Severe heat stress is treated in the hospital by putting
the patient in a tub of ice and cover as much of the body’s
surface as possible. The problem with only cooling the
head is that the body’s thermostat is the Hypothalamus
Gland. This gland is found in the middle of the head.
If you only cool the head, the thermostat thinks the entire
body has cooled and shuts down the cooling system and
may try to start warming things up again. This is the
opposite of what you want.
Why
is hydration is so important? As you sweat,
the water is coming from the blood which then causes the
cells in the blood to become more dense and the blood
becomes thicker. As the blood becomes thicker, it is harder
to pump. Further, the heart is only working with 50% of
the blood it normally gets, which means fewer nutrients
and less oxygen. With reduced blood volume, the heart
works harder and beats faster to make up for that loss.
This is why heat stress can be so dangerous. The heart
keeps trying to catch up and the blood keeps getting thicker.
The end result could be a heart attack. So you must go
to the track well hydrated. Studies have shown that it
takes up to 24 hours to rehydrate the body, so drinking
some water while you are at the track starts the process,
but it will be the next day before you have fully rehydrated.
Remember, drinking fluids does not affect core body temperature,
but it does begin the process of replacing fluids that
are lost.
At
the same time that the heart is working with only half
the blood that it normally uses, the brain is struggling
with the same problem. What happens in the brain is that
more mistakes are made, productivity goes down, attention
and short term memory are impaired and most importantly
reaction times are decreased significantly.
How
can I tell when I am starting to get heat stressed? It
has been shown that when you lose two percent of your
body weight due to perspiration you are in heat stress.
If you weigh 200 lbs then two percent would only be four
lbs. It has further been shown that with a four percent
weight loss (eight lbs.) reaction time goes down by 23
percent. Have you ever noticed on a hot summer day after
everyone has been there all day long that you see more
red lights as you get into the late afternoon? Now you
know the reason why: drivers have sweated out a bunch
of water, their core temperature is up and they are now
in heat stress. Their reaction time and ability to concentrate
are gone. If you can keep your core temperature down during
the day, you will not have perspired as much and you may
maintain better focus over other racers.
More
information can be found in this abstract HERE.
While
attending the 2012 Performance Racing Industry
Show in Orlando, I was especially intrigued by
one company in particular,