How the Body Maintains Internal Temperature

The body maintains a normal temperature of approximately 98.6°F (37°C). This is referred to as the body's core temperature. Your core temperature may vary by one degree throughout the day, depending on your level of physical activity and emotional factors. Also, every person is different, and this core temperature can vary slightly from individual to individual.

The body loses heat from the following conditions:

• Evaporation: Heat is lost in the form of vapor when the body uses heat to evaporate moisture from the skin's surface. This is known as perspiration or sweat.
• Convection: Heat is lost from wind or blowing air, which removes the layer of warm air next to the skin. The rate of heat loss is dependent on wind and air speed.
• Respiration: Heat is lost when the lungs warm inhaled cold air, which is then exhaled.
• Conduction: Heat is lost through contact with a cooler object when the heat is transferred to that object. This increases when in contact with cold, wet objects.
• Radiation: Heat is lost from exposed body areas due to the difference between body temperature and cooler air temperature.

Your body produces heat in the following ways:

• Metabolism: Heat is produced through metabolic processes when you digest food.
• Physical activity: Heat is produced by your muscles during physical activity.
• Shivering: Heat is produced when your muscles involuntarily quiver in response to cold temperatures. This response only lasts a few hours because of depletion of muscle "fuel" stores and the onset of fatigue.

There are external factors that influence your body's ability to produce heat, including the following:

• Food intake
• Glycogen store
• Fluid balance
• Body size and shape (surface to volume ratio)
• Layer of fat under the skin
• Insulation (clothing)

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