Hardening of the Body

a set of procedures to help increase resistance to unfavorable environmental factors and to form conditioned reflexes to improve thermoregulation. Hardening makes the body resistant to chilling and, as a result, to colds and some other diseases. If an organism is not conditioned to cold, its reaction is comparable to an unconditioned reflex: the time required for heat production is protracted, the blood vessels in the skin cannot constrict quickly enough, and the blood vessels become paralytically relaxed, causing even more heat to be emitted. The reaction of a hardened body to chilling is conditioned in nature: heat production increases, heat is retained because the skin blood vessels constrict (the so-called play of the vasomotors—brief dilatation of the blood vessels and an intensified blood flow), and the metabolic rate accelerates.

It is important to begin hardening in childhood, when thermoregulation is in the formative stage and the mechanisms of immunobiological defense are developing. Proper hardening requires the use of a set of procedures conforming to the principles of comprehensiveness, gradualness, regularity, and regard for individual characteristics. These procedures include convection cooling (air and sun-and-air baths) and conduction cooling (toweling, affusion, footbaths, swimming in open bodies of water, and contrasting procedures—for example, pouring alternately warm and cold water, differing in temperature from 3° to 10°C, upon the body; or going barefoot). Ultraviolet irradiation from artificial sources is important in the winter months, especially in the north.

The strength of the stimulus used for hardening is increased gradually. Water and air temperatures can be lowered more rapidly in spring and summer, when hardening is more spontaneous because lighter clothing is worn, and people swim in open bodies of water. When hardening is conducted in the fall and winter, the water and air temperatures are lowered gradually, after longer intervals. The procedures begin with air baths at mild air temperatures ranging from 24°C for infants to 18°-12°C for older schoolchildren and adults (at an air velocity of no more than 0.1 m per sec and a relative humidity of 40–65 percent). Sunbaths are three to five minutes long at first and then are gradually increased to 20–40 minutes, depending on the age of the individual. The skin temperature in the area of the heart is the basis used for general water procedures: 35°-36°C for children under one year of age and 31°-33°C for adults. Water at this temperature is used for rub-downs, 1°-2°C higher for suffusions and 1°-2°C lower for footbaths. The temperature is gradually lowered to 24°-26°C for children under three and to 12°-15°C for older children. The temperature of the exposed parts of the body (about 25°-29°C) is used as the basis for local water procedures and then gradually lowered to 10°-12°C. Contrasting procedures can be systematically used the second year. Swimming in an open body of water is a good hardening procedure.

Hardening must be carried out systematically. If a stimulus acts rather steadily for a longer or shorter period of time, a definite stereotype is formed to the stimulus. The effect of hardening is cancelled if it is not adequately reinforced. Thus, if the procedures are carried out for two or three months and then halted, the hardness acquired disappears in one to ll/2 months. If the interruption has lasted a long time, the hardening procedure is resumed at the original water and air temperatures. It is important, particularly in the case of children, to take individual characteristics into account (for example, the focuses of a dormant infection, convalescence from a sickness, anemia, heart disease, or asthma). The hardening is conducted without lowering the mild water and air temperatures. It should be borne in mind that excitable persons need tranquilizing procedures (air baths, rubdowns, and so on); sun-and-air baths are ruled out for them. Suffusion and contrasting procedures are recommended for people with inhibited reflexes, suffusion directly afier sleep for sluggish people, and morning calisthenics for calm and balanced ones. Sick people are not to be exposed to hardening procedures until they have completely recovered. The procedures are prohibited for people suffering from congenital and acquired heart defects in the stage of decompensation or from chronic kidney diseases.