THE INFLUENCE OF CLOTHING ON THE PHYSIOLOGICAL REACTIONS OF THE HUMAN BODY TO VARYING ENVIRONMENTAL TEMPERATURES

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Abstract
The partition of heat loss from normally clothed resting subjects, over a wide range of environmental temps., is shown to be broadly comparable to that found for nude subjects. The principal differences observed are: (1) broadening, in terms of environmental temp., of the degree range of vasomotor adjustment for the clothed condition; (2) a difference in the segmental skin temp. regulation employed to maintain the same absolute heat loss in the respective zones of body cooling; (3) a markedly greater rise in mean skin temperature and thermal conductance for the clothed condition at points of identical absolute heat loss in the zone of evaporative regulation. A difference of approximately 8[degree]C between skin and the environmental temperature can exist before body cooling sets in at 25[degree]T0 (operative temp.). Between 25[degree] and 29[degree]T). thermal equilibrium of the clothed body is maintained by vasomotor regulation. Above 29[degree]T0, evaporative regulation sets in. For equal wall and air temps. and a turbulent air movement of 5 m. per min., 55% of the total loss by radiation plus convection is lost in radiation; the transfer of heat from the clothing surface to the environment by radiation and convection is expressed by a value for the environmental constant of 7.34 kgm.cal./m2-hr.-[degree]C. The physical conductance of the clothing is 15.8 kgm.cal./m2-hr.-[degree]C. The thermal conductance of the skin has been expressed quantitatively in terms of an effective peripheral blood flow and a mean depth of the thermal gradient. Subsequent analysis shows that, in the zones of vasomotor regulation and evaporative regulation, blood flow is the principal variable in conductance. In the zone of body cooling (below 25[degree]T0), it is shown that with increasing depth of thermal gradient, as indicated by a general increased rate of cooling of the body, a peripheral flow of blood may slowly return. A range of 4[degree]-4.5[degree]C difference between internal tissues and skin represents a point of minimum conductance and presumable maximum vasoconstriction.

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