US Military Guide to Feet
US Military Guide to Feet
Source: TB MED 508 PREVENTION AND MANAGEMENT OF COLD-WEATHER INJURIES
Socks
Feet sweat at rest and even more so during physical activity. Layering using two pairs of socks is recommended. The first layer will be a thin nylon or polypropylene sock that wicks moisture away from the skin. The second layer will consist of a wool or wool-blend sock (either NSN 8440-00-153-6717 or 8440-00-543-7778) that can absorb the sweat from the foot. This sock must not be so thick that the boot fits too snugly as this can cause constriction of the blood vessels and increase the risk of cold injury. Boots may need to be sized larger so that a liner and an insulated sock can be worn.
Even with boots that are “breathable,” foot sweat will cause socks to become wet, which increases conductive cooling and cold injury risk. Socks therefore must be changed a minimum of two to three times throughout the day. Having wet feet for prolonged periods (more than 12 hours) increases the risk for trench foot.
Vapor barrier socks are effective in preventing foot perspiration from being absorbed into the boot; these socks also help to maintain warmer feet by reducing evaporative heat loss. The use of vapor barrier socks is a clothing technique that requires practice and experience in order to understand how moisture management works; it also requires drying feet overnight or the skin of the feet will rapidly deteriorate, resulting in blisters, trench foot, and increased risk of infection. Vapor barrier socks can also be used during conditions when boots will be wet due to movements through streams or swamps. In this case, a vapor barrier sock worn over the two layer sock will protect the feet from outside moisture, although sweat accumulation will increase.
Snow can fall inside any boot and melt, creating a cold-wet microenvironment. Gaiters (NSN 8415-01-514-2398) can help prevent this from occurring and also increase insulation by trapping air, helping to keep feet warmer and drier.
Soldiers will not sleep with footwear on, for several reasons. Feet need to be dried out overnight to maintain the skin integrity and prevent nonfreezing cold injuries. Also, feet will continue to sweat if boots are worn while sleeping, and the boots cannot dry completely. Boots can be placed inside the sleeping bag to dry out. Boots must not be placed outside in very cold temperatures because the moisture in them can freeze, and cold injuries can occur when placing feet in cold boots.
Boots
The Army has several types of boots for cold-weather operations.
The intermediate cold/wet boot (NSN 8430-01-471-8230) is designed to be worn in cold, wet environments where the temperature is above 10 °F. Wearing this boot for extended periods at air temperatures below 10 °F will increase susceptibility to cold injury, because considerable foot cooling will occur at these low temperatures due to insufficient boot insulation.
Two vapor barrier boots are in the Army’s inventory. One is colored black (NSN 8430- 00-823-7046) and is rated down to –20 °F. The other boot is colored white (NSN 8430-00-655- 5563) and can be used at temperatures as low as –60 °F. Proper fitting of the vapor barrier boots is essential, because tight boots will constrict blood flow, yet loose boots can cause blisters and also allow considerable snow to fall into the boot. Soldiers need to try on several pairs of vapor barrier boots while wearing the appropriate socks to get the proper fit and must not rely on the shoe size only.
The intermediate cold/wet boot has a limited capacity to transfer sweat, and the extreme cold-weather boot (vapor barrier) allows no evaporation, making it necessary for soldiers to change their socks two to three times daily.