Cold weather presents an array of potential physical problems for anyone who is active in the outdoors. Winter sports can be of particular concern to the athlete, because the cold is a problem on its own, as well as often magnifying other inherent risks.
Cold is a somewhat subjective state, as some people, through either acclimatization or body type, are better equipped to tolerate cold weather. Science has determined that the threat of cold-related illness is usually considered when the outdoor temperature reaches 40°F (4°C) or below. At these temperatures, the cold weather will begin to impact on the function of the body's cardiovascular and cardiorespiratory systems, both of which function best when the core temperature of the body is 98.6°F (37°C).
Outdoor temperature is the most important, but not the exclusive, component when assessing the risk factors that contribute to a cold weather illness. In order of importance, the factors are:
In cold weather conditions, approximately 60% of bodily energy stores are used for heat. The body's energy is derived from its metabolism of glucose, stored as a fuel within the muscles and liver. When the body is required to deliver energy to working muscles in cold weather, as in endurance sports such as cross-country skiing, the potential risks from cold weather are magnified, as the body uses significant stores for athletic power. When exposed to cold temperatures, the cardiovascular system will seek to protect itself by constricting the blood vessels near the skin surface.
The combination of cold weather and wind creates what is known as the "wind chill factor," which quantifies the relationship between cold temperatures and wind on the body. Wind chill is an expression for the actual effect of the environment on the body in a given atmospheric condition.
The wind chill factor is best understood, for example, when the air temperature is 0°F (13°C) and there is no wind, unprotected skin will freeze in 30 minutes; when the wind speed is 20 mph (32 km/ hr) at this same temperature, the wind chill is ™22°F (™30°C), skin will freeze in as little as 10 minutes, resulting in the condition known as frostbite.
Frostbite is the freezing of the skin or underlying body tissue. It is a serious condition, as the damage done to the body, typically to the toes, the nose, fingers, cheeks or ears, may necessitate amputation of the afflicted part. Frostbite often, but not exclusively, occurs in conjunction with the cold-related illness, hypothermia. Hypothermia has a very simple causal mechanism—if, exposed to extreme cold, the body temperature falls below 95°F (35°C), the gland that regulates body temperature, the hypothalamus, will no longer function. The body will then become too chilled to generate sufficient energy to produce replacement body heat to raise its temperature; the essential systems will ultimately cease function. Hypothermia requires immediate medical attention to reverse the body temperature drop.
There are a number of circumstances that may accelerate the onset of hypothermia, including:
Hypothermia and frostbite can occur independently of one another. For example, if a cross-country skier or snow mobiler falls through the ice into a body of water, the water temperature will likely be close to 32°F (0°C), given it is not frozen. The skin of the victim will not freeze while in the water, but the person will die of hypothermia in less than 10 minutes in such conditions.
Frostbite will typically appear as a pale or whitish-colored spot on the skin. In its initial stages, frostbitten skin may ache or cause an itching sensation. As the affliction progresses, the victim will usually experience a loss of feeling in the skin; to the touch, the skin may feel as if it has thickened. In a frostbite emergency, it is imperative that the injured limb or portion of the body immediately be protected from further exposure to the cold. The skin may then be slowly warmed, with a heated wrap or similar covering with which the skin temperature may be gradually raised.
In a case of hypothermia, it is imperative that the torso and chest be warmed first, so as to maintain a supply of reasonably warm blood in the heart to be circulated; warming the extremities may cause a rush of cold temperature blood to the heart, which may cause a sudden cardiac arrest. The victim should be kept warm, but alcohol or narcotics should not be administered.