Monday, January 25, 2016

MLS Seamanship Series - How Your Body Gains and Loses Heat

Your body operates at its prime within a very narrow temperature range of only two or three degrees. It has only three ways to gain heat but five different ways to lose it.

High Heat Loss Areas

Your body has five major heat loss areas:
  1. Head
  2. Neck
  3. Armpits
  4. Sides of chest
  5. Groin
Although your hands and feet may be the first to feel cold, they are not major heat loss sources.

Heat Gain - Your body gains heat three ways:
  1. External Sources: The sun, fires, and other heat sources warm your body.
  2. Digestion: Heat is produced as your body digest food.
  3. Muscular activity: As you move, your body produces heat, but activity in cold water may cause you to loose more heat than you gain because cold water is constantly flowing past your body's high heat loss areas.
 Heat Loss - Your body can lose heat five different ways:
  1. Radiation: Radiation occurs when heat is emitted from your body. Clothing is the obvious answer to preventing heat loss through radiation.
  2. Respiration: You lose heat by exhaling air that your body has warmed. Some of this heat loss can be prevented by covering your mouth with a loose knit scarf, hat, or other fabric.
  3. Evaporation: When your sweat evaporates, your body looses heat and moisture into the air. This explains why wet clothes make you cooler, which can be a good thing in a hot climate but deadly in a cool one.
  4. Conduction: Being in direct contact with cold surfaces - either solids or liquids - takes your heat away. Insulating yourself from these cold surfaces will stop or greatly slow conductive heat loss.
  5. Convection: Why does it feel cooler on wind days? Convection! This happens when your body's heat is taken away by moving air or water.
The combination of conduction and convection is the reason your body looses heat 25 times faster in water than in air of the same temperature.

Not being able to control your body's heat loss can lead to hypothermia, the lowering of your body's core temperature, which is one of the leading killers outdoors.

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