International Union for Circumpolar Health Ministry of Public Health and Social Development of RF Russian Academy of Medical Sciences Siberian Branch of Russian Academy of Medical Sciences Siberian Branch of Russian Academy of Sciences Medical Polar Fund “Science” The Northern Forum

Abstracts

Plenary session

Human thermal responses to cold are similar to those of tropical mammals. The thermoneutral ambient temperature for a naked and resting human is ca. 27 °C. Exposure to cold stimulates cold receptors of skin which causes cold thermal sensations and stimulation of sympathetic nervous system. Sympathetic stimulation causes vasoconstriction in skin, arms and legs. Diminished skin and extremity blood flow increases the thermal insulation of superficial tissues more than 300 % corresponding 0.9 clo (0.13 °C.m-2.W-1). With thermoregulatory vasoconstriction/vasodilatation the body heat balance can be maintained within a range of ca. 4 °C, the middle of the range being at ca. 21 °C when light clothing is used. Below the thermoneutral zone heat production (shivering) is stimulated and above the zone starts heat loss by evaporation (sweating). When ambient temperature decreases, the 24-hour energy expenditure increases 100 - 130 kJ/1 °C due to increased amount of clothing, cold induced heat production and other factors like snow, ice and darkness.

Cold induced vasoconstriction increases blood pressure and blood viscosity and decreases plasma volume consequently increasing cardiac work. Cold induced hypertensive response can be counteracted by light exercise like walking 3 km h-1 which stimulates circulation in legs, while starting heavy work in cold markedly increases blood pressure before the heat production of muscular work counteracts the effect. In very cold conditions the sympathetic stimulation opens the anastomoses between arterioles and venules which increases skin temperatures markedly but temporarily. This cold induced vasodilatation (CIVD) is most common in fingers and to some extent in face. Adaptation to cold takes ca. 2 weeks, whereafter the physiological responses to cold are attenuated and cold exposure is subjectively considered less stressful. Cold adaptation of hands diminishes the local vasoconstriction which allows higher circulation and skin temperatures in hands.

Note. Abstracts are published in author's edition

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Last update: 06-Jul-2012 (11:52:05)