As a trainer and firefighter in New York City for
the past nine-teen years, I've experienced many
frigid, New York City winters. I've learned how
important it is to protect yourself against the
elements, whether battling a tenement fire at 3 AM,
when the outside air temperature is hovering at zero
degrees, or just jogging over the piles of snow in
Central Park, you've got to take measures to protect
yourself.
Hypothermia, or the general cooling of the human
body, is the technical term for what we refer to as
freezing. Mild hypothermia can occur when your
core body temperature is between 96° and 99° F,
and you'll begin to shiver. Intense shivering
(shivering increases body heat producton by four to
five times) will set in from about 91° to 95°, and
will become less intense at temperatures below 90°.
Beware, at the point when shivering begins to
diminish, you're headed into severe hypothermia, a
possibly life threatening condition.
Severe Hypothermia
a.. Shivering becomes less intense
b.. Muscular rigidity sets in
c.. Unclear thinking, irrational behavior
d.. Possible amnesia
e.. Move to a warmer atmosphere
f.. Seek medical attention immediately
Exercise and Hypothermia
As long as core body temperature is maintained,
and sufficient insulative clothing is worn, it is
rarely too cold to exercise. By the time inhaled cold
air reaches the lungs it's already warmed up to a
safe temperature. However, if you suffer from
asthma be advised that breathing cold air can
trigger an attack.
Luckily the body is able to produce enough heat to
maintain core body temperatures under relatively
severe cold conditions. Aerobic exercise actually
makes this job easier. Three quarters of the energy
produced by the body during exercise is converted
to heat. Aerobic capacity seems to be unaffected by
cold when core body temperatures are maintained.
If core (and muscle temperatures) do drop,
cardiovascular endurance is similarly reduced. The
colder temps in the muscles themselves seem to set
off a greater anaerobic metabolism, producing more
lactic acid and associated muscle burn. This results
in an overall reduction in strength and power that
can produced in muscle tissue in severely cold
weather.
Wind Chill Index
When headed outdoors for a workout we need to
pay attention to the Wind Chill Index instead of just
consulting outside air temperatures. Wind increases
the rate at which insulating air surrounding the
body is whisked away, replaced with colder outside
air. Consult a Wind Chill Index (WCI) before
excerising outdoors in cold weather. As a general
rule, use caution when headed out with WCI of less
than minus 20° F. Anything under minus 70° F is
considered too dangerous to exercise.
Proper Clothing
Use up to four layers with a ventilation layer next
to the skin. One or two layers of insulation under a
protective outer shell works best. Be sure to wear
gloves and a hat. Large amounts of heat is lost
through the top of the head. Keep the neck and
throat area covered with a scarf or turtleneck.
Other Options
Cold weather is no reason to skip your workout, but
if you feel it's too cold to head outside, bring the
workout indoors. Consider a treadmill or other
piece of exercise equipment. Circuit training in the
gym, or at home using dumbbells, is another great
way to get an aerobic workout without having to
step foot outside.
Resources: Brady Emergency Care, 6th edition, Prentice Hall
ACE Certified News (jan.02), Taking the Chill Out of Winter Workouts, Bryant
