Benefit of heat acclimation is limited by the evaporative potential when wearing chemical protective clothing

Heat acclimation-induced sweating responses have the potential of reducing heat strain for chemical protective garment wearers. However, this potentia l benefit is strongly affected by the properties of the garment. If the clo thing ensemble permits sufficient evaporative heat dissipation, then heat a cclimation becomes helpful in reducing heat strain. an the other hand, if t he garment creates an impenetrable barrier to moisture, no benefit can be g ained from heat acclimation as the additional sweating cannot be evaporated . Ten subjects were studied exercising on a treadmill while wearing two dif ferent chemical protective ensembles. Skin heat Aux. skin temperature, core temperature, metabolic heat production and heart rate were measured. It wa s found that the benefit of heat acclimation is strongly dependent on the a bility of the body to dissipate an adequate amount of heat evaporatively. T he evaporative potential (EP), a measure of thermal insulation modified by moisture permeability, of the clothing ensemble offers a quantitative index useful to determine, a priori, whether heat acclimation would be helpful w hen wearing protective clothing system. The data show that when EP is < 15% , heat acclimation affords no benefit. An evaporative potential graph is cr eated to aid in this determination.