The biggest concern for exercising in the cold is
hypothermia, or too much heat loss. When you exercise in a cold
environment you must consider one primary factor: how much heat
will your body lose during exercise?
Heat loss is controlled in two ways:
1. Insulation, consisting of body fat plus clothing; and 2.
Environmental factors, including temperature, wind and whether
you're exercising in the air or in the water. Each of these
factors plays a role in the body's ability to maintain a
comfortable temperature during exercise.
Insulation
Although many people aspire to have a lean figure, people with a
little more body fat are better insulated and will lose less
heat. Clothing adds to the insulation barrier and is clearly the
most important element in performance and comfort while
exercising in the cold. One study showed that heat loss from the
head alone was about 50 percent at the freezing mark, and by
simply wearing a helmet, subjects were able to stay outside
indefinitely.
Clothing is generally a good insulator because it has the
ability to trap air, a poor conductor of heat. If the air
trapped by the clothing cannot conduct the heat away from the
body, temperature will be maintained. Unlike air, however, water
is a rapid conductor of heat and even in the coldest of
temperatures, people will sweat and risk significant heat loss.
With this in mind, you want to choose clothing that can trap air
but allow sweat to pass through, away from the body.
By wearing clothing in layers, you have the ability to change
the amount of insulation that is needed while many new products
can provide such a layered barrier, it is important to avoid
heavy cotton sweats or tightly woven material that will absorb
and retain water. Because these materials cannot provide a layer
of dry air near the skin, they can increase the amount of heat
your body loses as you exercise.
Keeping the hands and feet warm is a common concern when
exercising in the cold. Lower temperatures cause blood to be
shunted away from the hands and feet to the center of the body
to keep the internal organs warm and protected. Superficial
warming of the hands will return blood flow to prevent tissue
damage. Blood flow will not return to the feet unless the
temperature of the torso is normal or slightly higher (.5-1.0
degree Fahrenheit (F) above normal). So, to keep your feet warm
you must also keep the rest of your body warm at all times.
Check With The Weatherman
Always check the air temperature and wind chill factor before
exercising in the cold. Data from the National Safety Council
suggest little danger to individuals with properly clothed skin
exposed at 20° F, even with a 30 mph wind. A danger does exist
for individuals with exposed skin when the wind chill factor
(combined effect of temperature and wind) balls below minus 20°
F. That can be achieved by any combination of temperatures below
20° F with a wind of 40 mph and temperatures below minus 20° F
with no wind. If you are exercising near the danger zone for
skin exposure, it also is advisable to warm the air being
inhaled by wearing a scarf or mask over your nose and mouth to
warm the air being inhaled.
Rules For Exercising In The Cold
Check the temperature and wind conditions before you go out and
do not exercise if conditions are dangerous. Keep your head,
hands and feet warm. Dress in layers that can provide a trapped
layer of dry air near the skin (avoid cotton sweats and other
similar materials). Warm the air you are breathing if
temperatures are below your comfort level (usually around 0° F).
