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EXERCISE IN THE COLD
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COLD STRESS
An environmental condition that causes a
loss of body heat that could affecthomeostasis.
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MAJOR COLD STRESSORS
air
water
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Also known as the hypothalamus
the body has a set point of 37 celsius or 99fahrenheit
Any decrease will activate mechanisms thatconserve body heat and increase heatproduction.
Thermo-regulatory center
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Heating mechanisms of the
body
1.) Shiveringis uncontrolled muscular contractions thatcauses an increases in the body's resting rate of
heat production.
2.) Non-shivering thermogenesis
is the stimulation of metabolism by thesympathetic nervous system that increases theamount of internal heat production.
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Heating mechanisms of the
body
3.) Peripheral vasoconstriction
sympathetic simulation of the smoothmuscle surrounding the arterioles in theskin.
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FACTORS THAT AFFECT
BODY HEAT LOSS
1.)Body size and composition
Rate of heat loss is affected by the ratio ofbody surface area to body mass.
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Body's insulative shell
Gender differences can also be a factor in coldtolerance.
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b.) Underlying muscle
A vasoconstricted inactive muscle that can
provide 85% of the body's total insulation
during exposure to extreme cold.
Body's insulative shell
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2.) Wind Chill
the increasing rate of heat loss throughconvection and conduction.
The larger the difference between thetemperature of the skin and the cold
environment the greater the heat loss.
FACTORS THAT AFFECT BODY
HEAT LOSS
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HEAT LOSS IN COLD WATER
Heat loss in water is 26 times faster than in
air.
This is due to the transfer of heat during
immersion in water or conduction.
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HEAT LOSS IN COLD WATER
Prolonged immersion in water at about 15
degrees or 59 fahrenheit can lead to extreme
hypothermia and death
The rate of heat loss is increased if the cold
water is moving around the individual.
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If metabolic rate is low even a moderately
cool water could lead to hypothermia
Heat loss is accelerated when swimming at
high speeds but the swimmers increased rate
of metabolic production compensates for it.
HEAT LOSS IN COLD WATER
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PHYSIOLOGICALRESPONSES OF TRAINING IN
THE COLD
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METABOLIC RESPONSES
Higher glycogen consumption Shivering
High levels of epinephrine resulting in fasterglycogen breakdown
Faster heat production
Fatigue
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Higher FAT consumption
Glycogen depletion
Less Blood flow to skin
Preferential blood circulation
METABOLIC RESPONSES
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MUSCLE FUNCTION
Researchers suggests muscles become weaker
when it is cooled due to the altered recruitmentpatterns of the muscle fiber.
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CARDIOVASCULAR FUNCTION
Higher Blood pressure and heart rate.
Blood vessels constrict to conserve heat.
Blood concentrates on internal organs.
Reduces blood flow in skin.
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RESPIRATORY FUNCTION
Air passages narrow to warm the air that goes
in the lungs.
Exercise-induced bronchospasm may occur
People with asthma experience more
difficulty breathing.
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RISKS DURING EXERCISE IN A
COLD WEATHER
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caused by extremely lowbody temperature.
Lethal lower limit is 23-25degrees celsius or 72.4- 77
degrees fahrentheit.
HYPOTHERMIA
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HYPOTHERMIA
if the body temp. falls below 34.5 degrees
celsius the hypothalamus begins to loss its
ability to regulate body temp.
loss of function decreases metabolic reactions.
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HYPOTHERMIA
can cause injury to peripheral tissues andcardiovascular and respiratory systems.
the most important effect of hypothermia is onthe heart
cooling the heart influences the sinoatrial node
that can cause cardiac arrest.
decreases respiratory rate and volume.
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TREATMENT FORHYPOTHERMIA
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Mild hypothermia
treat by removing the person from the cold
environment and placing him/her at a room
temperature place.
provide dry clothing and warm beverages.
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Severe hypothermia
Requires immediate medical attention to
avoid cardiac arrythmia.
Need hospital facilities to revive the victim.
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FROSTBITE
Tissue damage due to
prolonged cold exposure atabout -29 degrees celsiusor -20 degrees fahrenheit
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occurs due to thedecreased circulation to theskin in an attempt to retain
body heat to the point thatthe tissue receivesinsufficient oxygen andnutrients.
FROSTBITE
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TREATMENT FOR FROSTBITE
Immediate hospitalization is required.
It should be left untreated until the can bethawed.
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Precautions for cold weather
training
Use adequate layers of clothing, but do not
overdress
Proper hydration
Knowing the wind direction
Planning of training
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COLD ACCLIMATIZATION
Studies have shown that chronic daily exposure to coldwater increases subcutaneous fat.
Chronic exposure of the skin to cold environment canprovide greater tolerance and can increase vasodilationand local warming.
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Reference:
Wilmore, J., PhD., & Costill, D., PhD. (1994).
Physiology of sport and exercise. USA:Human Kinetics.
