Hypothermia and Frostbite
December 25, 2005
Hypothermia is a sudden drop in body temperature that
can kill you. If you dress properly and exercise vigorously
enough, it should never happen to you. Your body sends you
signals as your temperature starts to drop. With a one-degree
drop in temperature, your speech becomes slurred. This, in itself,
is not dangerous, and occurs when people stay out in
temperatures below 35 degrees, but it serves as a warning that
you are losing more heat than your body is producing. To protect
yourself, you can produce more heat by exercising harder or you
can conserve heat by adding more layers of clothes. With a drop
of three degrees, you'll find it difficult to coordinate your fingers.
Seek shelter immediately. When your temperature drops five
degrees, you won't be able to walk and you'll stumble and fall
and not be able to get up. Then you may not be able to get out of
the cold and your body temperature can continue to drop rapidly
and you can die. If your clothes are wet, your temperature will
drop even faster. Take the warning signals seriously; if you have
slurred speech or difficulty using your hands, take action or you
may not get another chance.
Frostbite means that your skin is frozen. You have plenty
of warning before that happens. Your normal skin temperature is
around 90 degrees. As your skin temperature starts to drop,
blood vessels close and your skin turns white. When the
temperature reaches 59 degrees, your body attempts to rewarm
your skin by opening the blood vessels, causing your skin to
tingle, itch, burn and turn red. When this happens, get out of the
cold. If you don't, the blood vessels in your skin will close down
again and your skin temperature can drop below 30 degrees and
start to freeze.
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Dear Dr. Mirkin: I’ve started to exercise, but so far I haven’t lost
any weight. What am I doing wrong?
When people start an exercise program, some lose a lot
of weight, while others lose nothing. An effective exercise
program for weight loss should be 1) continuous, 2) use all of
your major muscle groups, 3) include one intense workout a
week for each muscle group, and 4) be done on land, rather than
in the water. Stop-and-start exercises, such as lifting weights,
do not require that you use your muscles continuously enough to
burn a lot of calories. Those that use just one muscle group, such
as doing situps or pushups, won't help you to lose a lot of weight
because the stressed muscle groups tire quickly so you can't
exercise very long.
Exercising at a leisurely pace won't help you lose a lot of
weight either. You burn calories while you exercise and after you
finish exercising. Intense exercise raises body temperature which
continues to be elevated and burn more calories for several
hours after you finish exercising. This also explains why
swimming is not the best exercise for weight loss, because water
conducts heat away from your body so fast that your temperature
does not rise. When you exercise on land, air insulates your body
so your temperature rises.
Pick sports in which you can exercise intensely, but don't
exercise very hard in one sport more often than once a week.
Every time that you exercise, you muscles’ fibers are torn
slightly. You can tell this has happened to you when you muscles
feel sore on the day after you have exercised. If you exercise
intensely on days when your muscles feel sore, you are at
increased risk for injuring them. Instead, alternate two sports,
one that stresses your upper body and one that stresses your
lower body.
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Dear Dr. Mirkin: Will fasting before a big race improve my
endurance?
No. Fasting became popular because of a study that
showed rats can run further after fasting than after eating. But
rats are different from people. In rats, fasting increased the rate
that a rat's muscles use fat, to preserve stored muscle sugar. In
humans, fasting does not cause muscles to burn more fat. After
fasting, human muscles continue to burn primarily their own
sugar. Fasting for 24 hours uses up the same amount of muscle
sugar as running for 90 minutes.
How long you can exercise a muscle depends on how
much sugar, called glycogen, you can store and how long you
can keep glycogen in that muscle. When a muscle runs out of its
stored glycogen, it hurts and you will have difficulty coordinating
it. Every time that you move a muscle, some of the stored
glycogen is used up. Every time that you eat, some of the food
can be stored as glycogen in that muscle. When you go for a
long time without eating, you use up glycogen without replacing
it. If you fast before a race, you will start that race with reduced
stores of glycogen in your muscles and you will not be able to
compete at your best.
It is nonsensical to claim that fasting increases
endurance by causing muscles to burn more fat and less
glycogen so that muscles can retain their stored glycogen longer.
When you start with less glycogen, you still use it up faster and
run out of fuel earlier. You can increase your endurance by
markedly cutting back on exercise four days before your
competition and eating as much or more than usual. If the
competition lasts more than two hours, you should also eat and
drink during the event.
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Last Minute Recipe
Make up a plate of my favorite holiday confection:
Fruity Pebbles
List of Diana's Healthful Recipes