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human clothing worn to protect the feet from harmful external effects.
Modern footwear is designed for everyday or special wear. Everyday footwear includes shoes for daytime, evening (high fashion), and home wear. Special footwear comprises orthopedic and industrial shoes and shoes worn for various sports.
The comfort of footwear is determined by internal dimensions and shape, particularly the size and width. In the French size code that was formerly used in the USSR and still exists in many countries, shoe size is determined by the length of the bottom of the last (insole) on which the footwear is manufactured. The size is expressed in units, with 1 unit equaling 2/3 cm. For example, a size 36 shoe has an insole length equal to 36 units. In the USSR, a system of footwear sizes has been introduced (State Standard 3927–64) in which the length in cm of the foot is used as the size number. Each size represents an increase of 0.5 cm. Table 1 shows the various shoe-size categories in the USSR. Shoes of the same size should be available in different widths. The width corresponds to the girth of the foot at the metatarsophalangeal joint and is designated by a number or a letter.
|Table 1. Shoe size categories in the USSR|
|Infants (up to 1 year) .........................||9.0–10.0|
|Infants (1 to 1½ years) ........................||10.5–13.0|
|Toddlers (2½ to 4½ years) .....................||13.5–16.5|
|Children (5 to 7½ years) .......................||17.0–19.0|
|Girls (8 to 10½ years).........................||19.5–21.5|
|Girls (10½ to 13½ years) ......................||21.5–24.0|
|Boys (8 to 10½ years) ........................||19.5–22.0|
|Boys (11 to 14 years).........................||22.5–24.5|
The design of footwear is determined by the anatomy of the foot and its range of movement. Moreover, the design of the last is determined by aesthetic requirements, fashion, and the capabilities of production equipment. Because movement causes the foot to expand 10 to 12 mm, the length of the insole is made greater than that of the foot (5 mm longer in women’s everyday shoes and 10 mm longer in men’s and boys’ shoes). In children’s footwear, annual foot growth is taken into consideration. With mass production of footwear, the range of sizes and the quantity of each size to be manufactured are calculated on the basis of a norm established by a survey of foot sizes.
Modern footwear is marked by a great diversity of form, style, decoration, and detail. The various shoe parts, depending on the load or stress acting on them, are manufactured from materials with different mechanical properties. For the exterior of the upper, leather, cloth, or artificial leather is used. The soles are made of leather, rubber (porous, nonporous, or leatherlike), Nylon 6, polyvinyl chloride, polyethylene, or other materials. The parts of the upper generally are stitched together, forming the upper stock. The upper is joined to the sole by one of various methods, including the cement shoe technique, hot vulcanization, the injection-molded-sole technique, and stitching. The cement shoe method involves applying cement to the stretched edges of the upper and to the sole. Hot vulcanization of the bottom to the footwear is done in special presses, into which the upper has already been placed together with the bottom stock (sole, heel, and lining), which has been cut from a raw rubber mixture. The upper has been stretched on a last, and cement has been applied to its stretched edge. The temperature and pressure in the presses simultaneously vulcanize the raw rubber and fasten the bottom to the upper. In the injected-molded-sole technique, a single production operation both molds the bottom (from a polymer or gelatinous paste) and fastens it to the upper. After a brief cooling period, the finished articles are removed from the mold and do not require further processing. The stitching method consists of sewing the bottom to the upper with linen or nylon thread. The most common stitching method is welting, whereby the sole is fastened to a welt, a strip of leather or synthetic material measuring 12–14 mm wide. The welt is first sewn to the upper and then to the insole.
Modern footwear must meet a number of hygienic, physical, and sanitary requirements. Under normal air conditions (temperature of 18°–20°C and humidity of 65–75 percent), 1.5–3 g of perspiration are given off in 1 hour from the foot surface of an adult at rest, and 8–12 g when in motion. Evaporation is possible only if the relative air humidity inside the footwear is sufficiently low. It is essential that the foot be in a medium having a definite temperature and humidity. This can be ensured by selecting the proper materials and design for footwear.
V. M. KLIUCHNIKOVA
Everyday footwear should not press on the foot. The toe of the shoe should correspond to the shape of the toes, the sole should be flexible, and the counter should be stiff. The toe may be pointed only in that portion of the shoe beyond the toes. Poorly fitted footwear for children impedes normal growth of the foot. The arches of the feet may be damaged, and flatfootedness may develop. Tight and narrow footwear, with long wearing, can lead to deformation of the foot, restriction of joint mobility, and a disruption of blood and lymph circulation. In cold and damp weather, tight shoes cause the feet to get cold and to freeze. Excessively large footwear may cause chafing and the formation of calluses.
The most comfortable shoes are those having a broad heel of moderate height (2–3 cm for men, 2–4 cm for women, 1–2 cm for schoolchildren, and 2–3 cm for teenagers). Wearing footwear with too high a heel shortens the gastrocnemius muscles and weakens the ligaments and the anterior muscles of the knee. It can cause foot cramps, sprained ligaments, and dislocated ankles. The wearing of high-heeled shoes by youngsters can cause curvature of the spine, a change in the shape of the pelvis, and displacement of internal organs. The thermal insulation properties of footwear are particularly important, as they provide a normal temperature on the surface of the foot during the various seasons.
Leather footwear having a leather sole is most hygienic. It is sufficiently strong, air permeable, and flexible. Footwear for winter use in cold climates should be inslated with wool, natural or simulated fur, or any one of various synthetic materials. In summer footwear, such as sandals, sufficient air exchange should be provided.
Footwear designed for various sports should meet the special requirements of its specific purpose. Footwear for hiking, skiing, and mountain climbing should be heat retentive and waterproof and have a free cut. Mountain-climbing footwear is made from thick leather and has a double sole, to which metal lugs are attached when necessary. Cross-country skiers wear a light shoe with a flexible toe, which enables the toe to bend. Slalom skiers and ski jumpers wear a boot with a thick, unbending sole and with special straps that hold the ankle securely. Speed skaters wear a light shoe, with a narrow sole and with welts on the skates for better stability. Figure skates are high, at least 8 cm above the ankle, to prevent spraining the ankle ligaments. Track shoes are light and are made from soft leather that fits the foot snugly. They do not have stiff counters and toes or coarse seams and folds on the inside. Footwear for wrestlers, boxers, and weight lifters is made from strong soft leather and is ankle-high. Rubber is cemented to the sole to prevent slipping.
Orthopedic footwear is prescribed to treat pathological changes in the feet. It also helps to correct incipient, nonpermanent deformations of the legs, by arresting the aggravation of such deformations. Orthopedic shoes often compensate for shortened legs. The footwear should correspond in shape and size to the patient’s foot and should be light, flexible, and strong. Its shape should not be altered during wear. The interior should be smooth, without rough seams; indentations are provided for the painful areas of the foot. The upper of all orthopedic footwear is made from soft leather. Stiff leather is used for the counters and, sometimes, for the sides; leather, Duralumin, cork, felt, or plastic is used for the insoles.
Industrial footwear is used to protect the feet from occupational injury. High or low boots are manufactured for work in hot shops. The front surface is smooth, and there is a diagonal side slit and easily opening clasps. The upper is made from heat-resistant Russian leather or kersey, and the sole from heat-resistant rubber. The insole is made of felt and leatherboard. In emergency situations, protective asbestos overboots with a fireproof backing are worn. For protection against moisture, footwear made from rubber or leather treated with water repellents is used. For protection against cold, footwear is made from fur, felt, coarse-wooled fabric, or insulated Russian leather and has a warm lining and loose insoles.
Dielectric boots are worn in cases where there is contact with electric current. Such footwear is stored in a dark area with a temperature of 5°–20°C and a relative humidity of 50–70 percent. The dielectric properties are tested at least once every six months. For protection against chemicals (acids, alkalies), special rubber boots are worn. After use the boots should be neutralized with soda against an acid or with an organic acid solution against an alkali. The boots should then be rinsed with water. Such footwear should be stored in a dark area at a temperature of 0°–20°C. In occupations that have high risk of physical injury, shoes with external or internal metal toes are worn. Vibration-resistant footwear has a sole of multilayer porous rubber and loose insoles of fine porous materials. In jobs in which radioactive substances are handled, rubber boots are worn, as are rubber and plastic larrigans. Such footwear is stored in a special place and is periodically inspected. It is prohibited to remove such footwear from the factory’s or plant’s premises.