Wilderness Skills - Olympia Mountaineers

Understanding and applying a few
elementary principals of thermodynamics,
physiology and fabric technology can help
you choose the best clothing for your
needs. These basic concepts include:
Heat Production, Temperature
Requirements, Heat Retention, Insulation,
Moisture Management, and Weather
Protection. With the following information,
you can apply a little science to your
challenge of selecting clothes for safe and
comfortable adventures, or you can buy
what everyone else is wearing and skip
this stuff.
The following information also covers
some practical lessons on selecting the
right clothes for your needs. This
information should help you select an item of clothing for its
adaptability, range of applications, price, longevity, ease and
cost of care, and finally appearance.
Practical Information for Selecting the Right Clothes
Heat Production
The human body generates heat as result of normal
metabolism, the oxidation of the food consumed or stores in the
body. When the ambient temperature, the temperature of the
surrounding air, is around 70° F, a healthy body generates more
than enough heat to stay comfortable. With exertion, the body
will produce excess heat, and will heat the air around it. During
the average day of modern office-home activity, a person burns between 100 and 200 calories per hour. At this
level of exertion a person will perspire, but at a low level that will usually evaporate rather than accumulate.
During 4 to 6 hours of high exertion during a scramble with 3500 ft elevation gain, the body consumes greater
quantities of energy ranging between 250 and 1000 calories per hour. This level of exertion will generate great
quantities of excess heat and perspiration for all but the most fit climber or the coldest weather conditions. The
scrambler will need an effective system for venting this heat or suffer wetness from the body’s natural cooling
agent; perspiration. Worse consequences include; exhaustion, disorientation, and heat exhaustion.
To reduce the build up of body heat, the efficient hiker will simply shed clothing as the most common option.
During rain or snow conditions, this doesn’t work as well. A great deal of heat will be trapped inside rain gear
although most of the insulating clothing has been removed. Traditional options for ventilation include oiled or
raw wool, poncho, or stop and cool down. New options include breathable, waterproof clothing with zippered
vents or waterproof; non-breathable clothing that functions as a vapor barrier (a moisture trapping system).
Temperature Requirements
To function properly, the human body maintains a core temperature (central organs and brain) of nearly 100°
F, actually 98.6° F. The core temperature must be stay within a narrow range because the central organs
cannot tolerate changes of more than a few degrees above or below 98.6°. The extremities, such as the arms,
hands, feet, and skin however, can adjust to a much wider range of temperatures. Your face, for example, is
able to endure a temperature range of over 50° F (from 40° to 90°) without noticeable difficulty. With core
temperature change of 3 to 4 degrees, however and you’ll feel sick and look sick.
Wilderness Skills Module Page 21 of 73
Olympia Mountaineers - Hiking, Alpine Scrambling and Basic Climbing