Human beings work and exercise in a variety of environmental conditions. Hot and cold weather produce unique problems for people who function outdoors. Their safety and comfort depend on their knowledge of the ways the body reacts to physical activity in different climatic conditions.

Heat is produced in the body as a by product of metabolism. Physical activities significantly increase metabolism, so more heat than normal is generated. Heat must be dissipated effectively, or heat build up (hyperthermia) may result in illness and possible death. Hyperthermia is abnormally high body temperature. Heat exhaustion is a serious condition but not an imminent threat to life. It is characterized by dizziness, fainting, rapid pulse, and cool skin. Treatment includes immediate cessation of activity and moving to a cool, shady place. The Victim is placed in a reclining position and given cool fluids to drink.

Heat stroke is a medical emergency and a threat to life. It is the most severe of the heat induced illnesses. The symptoms include a high temperature (106° F or above) and dry skin caused by cessation of sweating. These symptoms are accompanied by some or all of the following: delirium, convulsions, and loss of consciousness. The early warning signs include chills, nausea, headache, and general weakness. Victims of heat stroke should be rushed immediately to the nearest hospital for treatment.

Guidelines For Exercise In The Cold

Problems related to exercise in cold weather include frostbite and hypothermia (abnormally low body temperature). Frostbite can lead to permanent damage or loss of a body part from gangrene. This can be prevented by adequately protecting exposed areas, such as fingers, the nose, ears, facial skin, and toes. Gloves, preferably mittens or thick socks, should be worn to protect the fingers, hands, and wrists. A stocking hat is preferable for two reasons:

Blood vessels in the scalp do not constrict effectively, so a significant amount of heat is lost if a head covering is not worn.

A stocking type hat can be pulled down to protect the ears.

In very cold or windy weather, you can use surgical or ski masks and scarves to keep facial skin warm and to moisten and warm inhaled air. All exposed or poorly protected flesh is vulnerable to frostbite when the temperature is low and the wind chill high. Air temperature plus wind speed equals the wind chill index. This value should be known if one is to dress appropriately for outdoor exercise. A temperature of 40°F with a wind speed of 15 mph produces a windchill index of 22°F, meaning that these two factors together make a temperature of 40°F feel like 22°F.

People often experience a hacking cough for a minute or two after physical exertion in cold weather. This is a normal response and should not cause alarm. Very cold, dry air may not be fully moistened when it is inhaled rapidly and in large volumes during exercise, so the lining of the throat dries out. When exercise is discontinued, the respiratory rate slows and the volume of inhaled air decreases, allowing enough time for the body to fully moisturize it. Coughing stops within a couple of minutes as the linings are remoistened.

Hypothermia is the most severe of the problems associated with outdoor activity in cold weather. Hypothermia occurs when body heat is lost faster than it can be produced. This can be a life threatening situation.

Exercise in cold weather requires insulating layers of clothing to preserve normal body heat. Without this protection, body heat is quickly lost because of the large temperature gradient between the skin and environment. In addition to the insulating qualities of layers of clothing, a layer or two can be discarded if you get too hot.

Hypothermia can occur even if the air temperature is above freezing. For instance, the rate of heat loss for any temperature is influenced by wind velocity. Wind velocity increases the amount of cold air molecules that come in contact with the skin. The more cold molecules, the more effective the heat loss. The speed of walking, jogging, or cycling into the wind must be added to the speed of the wind to properly evaluate the impact of wind chill.

You should wear enough clothing to stay warm but not so much that you induce profuse sweating. The amount of clothing appropriate is based on experience that comes from exercising in different environmental conditions. Clothing that becomes wet with sweat loses its insulating qualities. It becomes a conductor of heat, moving it from the body quickly and potentially endangering the exerciser.

If you exercise or work outdoors in cold weather, you may want to wear polypropylene undergarments. Polypropylene is designed to wisk perspiration away from the skin so that evaporative cooling will not rob heat from the body. You should wear a warm outer garment, preferably made of wool, over this material. If it is windy, you should wear a breathable windbreaker as the third, outer layer.

If you follow the guidelines for activity in hot and cold weather, you can usually participate quite comfortably all year long.