Metabolic Heat Retention and the Vehicle Operator

Heat stress and metabolic heat retention is known to be a major contributing factor to discomfort, fatigue, reduced visual acuity, and performance decrements. Trim materials and other constituents of the seating devices have been studied to determine their effect on heat dissipation. Forty-five trim cover materials, sixteen trim pads, and five foam cushion pads were studied for impedance to body heat loss by evaporation, conduction, convection, and radiation. The range of heat flux through the various materials ranged from 6.5 BTU/FT²/HR to 35 BTU/FT²/HR. The minimum desirable heat flux value of 24 BTU/FT²/HR was established. The relationship of metabolic heat retention to physiological variations that can affect overall performance were discussed.