Body response to cold
The effect of cold on exercise performance depends largely on the severity of the cold and the nature of the exercise. With x-c skiing, exposure to extreme cold reduces both the athlete's core body temperature and maximal aerobic power (VO2 max), impairing the athlete's performance.
Moderate cold exposure, however, may actually produce a positive effect. Like all warm-blooded animals, skiers must maintain an internal body temperature close to 98.6 0F (37 0C). During exposure to a cold environment, the normal body temperature is maintained by increasing heat production and/or reducing the rate of heat loss (heat conservation).
Heat production can be increased by voluntary exercise or by shivering, which is caused by involuntary muscle contractions.
Heat conservation is accomplished behaviorally by adding clothing or physiologically by constricting the vessels that carry blood to the skin and to regions of the body such as the ears, feet, and hand.
Factors affecting body heat loss
Research has shown that the performance of endurance exercise is enhanced by cooler environmental conditions and by treatments such as brief pre-exercise cold showers. Indeed, record performances during long-distance running and cycling are usually achieved in cool climatic conditions.
In contrast, both severe and moderate cold can adversely affect the performance of activities that depend on high levels of anaerobic power (ski jumping, biathlon and some shorter distances of x-c ski competition). These effects are most profound when the conditions are severe enough to reduce muscle temperature. As in the case of heat stress, the body's ability to meet the demands of thermoregulation is limited when exposed to extreme cold. Too much heat loss can occur. Those factors (conduction, convection, radiation, and evaporation) that usually perform so effectively in dis-sipating metabolically produced heat during exercise in warm conditions, can, in a cold environment, dissipate heat faster than the body produces it.
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| It is more difficult for child than the adult to maintain body temperature in cold environment due to the significantly larger surface area to weight ratio. Extra caution must be taken by teachers to prevent hypothermia in children while they ski or skate outdoors. |
 |
|
Person
|
Weight
(kg)
|
Height
(cm)
|
Surface
area (cm2)
|
Area/weight
ratio
|
|
Adult
|
80
|
185
|
210
|
2.48
|
|
Child
|
25
|
100
|
3.16
|
Practical Tips for Exercising and Competing in Cold Environment
Exercise and sport participation can be pursued safely and successfully in cold conditions by observing the following precautions:
Proper warm-up
In many athletic activities, particularly those relying on speed and power, optimal performance requires the elevation of the muscle temperature before competition. In cold conditions, this state is difficult to achieve and may require wearing heavier clothing, exercising more intensely and/or longer, and continuing the warm-up activity until immediately before the competition.
Appropriate clothing
When dressing for exercise in the cold, the athlete should ensure adequate insulation while avoiding an accumulation of sweat in the garments. Clothing should be selected for comfort during the activity, after metabolic heat production has reached a steady-state. Athletes should resist the temptation to overdress, as this can lead to sweat accumulation in the clothing. Multiple layers of clothing provide good insulation. However, the innermost layers should carry moisture away from the body surface. Polypropylene or cotton fishnet materials are recommended. Since much heat can be lost through the head, proper head covering is a must.
Gauge the wind
Wind can greatly increase heat loss from the body. During training, runners, cross-country skiers, and other endurance athletes should go out facing the wind and come in with the wind. This will avoid exposure to high wind chill while wearing sweat-soaked clothing.
Prevent frostbite
During cold exposure, the fingers, toes, ears, and facial tissues are susceptible to frostbite because of the reduction of blood flow to these tissues. These areas should be checked regularly during prolonged exposure to cold, windy conditions.
Note: Victims of frostbite are often unaware of the condition because extreme cold blocks sensations of pain.
Prevention of postexercise hypothermia
Hypothermia is a dangerous and potentially lethal condition in which body temperature falls markedly below the normal 98.6 0F (37 0C). Many cases of hypothermia can develop rapidly after exercise at low temperatures because the heat production has decreased while the rate of heat loss has remained high. Postexercise hypothermia can be prevented by adding clothing and moving to a warm environment soon after finishing the competition and drinking fluids.
