COLD INJURIES - Medicine for Mountaineering and Other Wilderness Activities - page 394

Protecting Hands and Feet
When the body is cool, the blood vessels in the hands and feet constrict, reducing heat
loss through those tissues but also reducing their temperature and commonly causing dis-
comfort,whichcanbesevere.Themosteffectivewaytopreventcoldextremitiesistokeep
the body warm, a lesson some outdoor enthusiasts seem to have difficulty learning.
For the hands, mittens are much warmer than gloves. Radiant heat is lost from the sur-
face of protective garments; the larger the surface area, the greater the heat loss. Because
the fingers are such narrow cylinders, increasing the thickness of gloves by more than one-
quarter inch increases the surface area to such an extent that the increased heat loss elim-
inates any benefit from the increased insulation. Because mittens do not have such a large
relative surface area, their thickness can be increased to a much greater extent without a
concomitant increase in heat loss.
Thebasiccomponentsofmittensareanoutershellandaninsulatinglayer.Athirdinner
layer of a thin fabric such as nylon or silk—usually a glove—is useful if the mittens have
to be removed to manipulate clothing or equipment. The outer shell should be an abrasion-
resistant material, typically nylon. Wool works well for insulation, but down and synthetic
materials are also used. Many different types of one-piece mittens have been developed,
particularly for skiing. Many are quite expensive but are not more effective than a simple,
inexpensive wool mitten with an outer nylon shell.
Oneofthewarmest typesoffootgearyetdevisedistheU.S.Armydouble-vapor-barrier
boot known as the white Korean (Mickey Mouse) boot. However, this type of footwear is
toosoftforkickingstepsinhardsnowandisdifficulttofitwithcrampons.Fortheseverely
coldclimates typicalofhighaltitudes, doubleortriplebootsarebestforclimbers.Theout-
er boot is usually constructed of hard, protective plastic, and the inner boots are made of
softer insulating material. Older double boots were made of leather, which is heavier than
plastic. Leather is porous, which allows moisture to escape, and leather can expand to ac-
commodateswellingoffeetandanklesduetoanuprightpositionoraltitude.Itremainsthe
best material for single boots in moderately cold climates.
Head Protection
The voluminous blood flow to the head is a potential source of major heat loss. In cold
weather, effective headgear such as wool caps is essential. Balaclavas that cover the neck
and lower face are desirable for severe conditions. Hoods do not fit closely enough to be
as effective but do provide additional protection when worn over caps, particularly if the
hood is insulated.
Insulatingscarvesandneckgaiters(wool,usually)reduceheatlossfromthelargeblood
vessels that are close to the skin surface in the neck.