The accounts that open this post were taken from the diaries of two courageous explorers who were among the first Europeans to explore the vast wastelands of the Arctic and Antarctic. Because these explorers traveled and years ago, respectively, it is fair to ask what relevance their experiences have for athletes, soldiers, and laborers today. The answer is’great relevance. Even with the development of modern fabrics and insulated gear, intense or prolonged cold exposure can still disrupt the maintenance of body temperature homeostasis, impair pulmonary function via bronchospasm, and injure skin and other tissues. A typical case of cold injury occurred in Fairbanks, Alaska, inThe official maximum temperature was -C -F or lower for days. A woman, whose car had stalled, walked for minutes with her legs covered only by silk stockings, and subsequently spent a month in the hospital with frostbitten legs. This exemplifies the fact that in our modern age of heated homes, automobiles, and businesses, the average person is not aware that all of his or her physiological reserves for combating cold may suddenly be drawn on.
In the cold climates of earth, there are multiple environmental stressors that disturb homeostasis in the body’s systems. The most obvious stressor is air temperature that is below skin and core body temperature. As figureillustrates, the balance of heat production from basal metabolic rate, exercise versus heat loss from evaporation, radiation, convection; see post is disrupted; heat loss exceeds production and the central body temperature decreases, sometimes to the point of death by hypothermia rectal temperature approximately C, F or injury by frostbite skin temperature – to C, to F. The second common environmental stressor is air movement across the body. Wind greatly accelerates the loss of body heat, by a removing via convection still warm air layers trapped in insulative clothing, b increasing evaporative cooling when the insulative material is wet, orincreasing evaporative cooling directly from sweat- soaked skin. Antarctic explorer Paul Siple coined the term wind chill to define the combined effect that low air temperature and air movement have on skin. This effect may account for as much as of all heat lost from the body in cold air. Figurepresents the widely recognized windchill chart, which describes the risk of freezing exposed flesh in cold environments. You should note that flesh may freeze in one minute or less, if the windchill is severely low in the increased risk or great risk categories. The risk of whole-body hypothermia also increases as the windchill becomes more severe.
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The third environmental stressor that disturbs the homeostasis of the body’s systems and organs is dry air. Air with a very low relative humidity has been identified as a stressor at two sites: the hot, dry desert winds known as the Foehn or Sharav see chapterand cold, dry air that contains pollutants see chapterIn this chapter, the effects of dryness plus cold air will be considered as they affect the smooth muscle surrounding lung and bronchial airways. Inhalation of cold, dry air stimulates exercise-induced bronchospasm EIB, whereas warm, moist air during swimming is tolerated much better by asthmatics and other sensitive individuals. This effect apparently occurs even when warm, dry air is inhaled by healthy adults at high ventilatory rates; in this instance, FEVt is reduced.
Water immersion, of the entire body or the extremities, is the final environmental stressor that may be associated with cold Earth’s cold environments left and cold-induced central body or tissue temperature in various animals right: a hypothermia is defined as a rectal temperature below C; b frostbite occurs when skin temp falls below – to C.
In contrast to wet skin, hair, or clothing, which accelerates evaporative cooling, water immersion which involves convection and conduction may cause faster cooling of core body temperature than any other environment that laborers, soldiers, and athletes face. At rest, the fact that cooling via cold water is – times greater than in air at the same temperature explains why a pilots typically die from hypothermia when they perform emergency landings in the ocean see figure and b ice-water immersion is the most effective whole-body cooling technique see bars f andin figure pageTherefore, whenever working or exercising in a cold environment, you should avoid water immersion.
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