Clothing insulation as a biometeorological parameter during rest and exercise.
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Body Temperature↗
Biomedical subjects
A P Gagge
Publications and source records attributed to A P Gagge.
Indices of thermoregulatory strain for moderate exercise in the heat.
The effect of varying humidity and dry bulb temperatures was studied on five normal male unclothed subjects while exercising (40-45 min) at 28% VO2max. Air movement was 0.75 m.s-1. The initial test and the 16th test on each subject both done at 50 degrees C and 30 Torr (32% rh). Each subject did the intervening 14 experiments twice per day at varying ambient temperature (Ta) and water vapor pressure (Pa) levels, so selected to progressively increase skin wettedness levels. Mean skin temperature (Tsk) and esophageal temperature (Tes), heart rate (HR), skin evaporative heat loss (Esk), and warm discomfort were continuously observed. Skin wettedness (w) was evaluated as the ratio of the observed Esk to the maximum evaporative capacity of the environment. A rational effective temperature (ET) is defined as the dry bulb temperature at 50% rh in which the total heat exchange from skin surface would be the same as in the test environment, described by the observed Ta and Pa. The results showed that 1) during steady state both HR and Tes were unaffected by Ta from 26 to 41 degrees C responding to the level of exercise intensity, when Pa less than or equal to 20 Torr; 2) both mean body temperature, found by weighting Tsk:Tes by 1:9, and ET were each significant indicators of physiological strain when Pa greater than 20 Torr; 3) a level of strain, caused by skin wettedness values greater than 0.5, is suggested as a primary condition necessary for inducing heat acclimation.
Acclimatization↗
Effective temperature scale useful for hypo- and hyperbaric environments.
Basic physics of man's heat exchange by radiation, convection, evaporation, and conduction through clothing is used to define and establish a Standard Effective Temperature Scale (SET), with which sensory and physiological responses of sedentary and active personnel can be related. The standard environment chosen is the Effective Temperature (ET) Scale, used by the American Society of Heating, Refrigerating and Air-Conditioning Engineers; namely, as the temperature of an isothermal enclosure at sea level with 50% rh and still air (0.1-0.15 m/s) in which a clothed (0.6 clo) sedentary subject would exchange the same total sensible and insensible heat as in the actual test environment. Mean skin temperature (Tsk) and skin wettedness (w) can be associated at sea level with thermal comfort and neutrality and with heat exchange. For hypo- and hyperbaric environments, thermal equivalence between SET and any test environment occurs when mean body temperature (Tb) for each is identical. Comprehensive data, developed for a 2-node model of human temperature regulation and of the associated partitional calorimetry, demonstrates the expected interaction between SET and the basic environmental and clothing factors over the barometric range 0.33 to 30 ATA.
Air Movements↗
Warm discomfort and associated thermoregulatory changes during dry, and humid-heat acclimatization.
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Acclimatization↗
Prediction of equivalent environments by energy exchange and assessments of physiological strain and discomfort.
The described equivalence postulate was confirmed experimentally by examining physiological responses as well as discomfort sensation in a series of predicted equivalent conditions during exercise (congruent to 3 met). ET or the equivalent Ta at 50% RH is a single independent variable that is uniquely related to the mean skin temperature (Tsk), skin wettedness (w), body core temperature (Tcore) and sense of discomfort.
Body Temperature Regulation↗