VALIDATION AND ADJUSTMENT OF THE MATHEMATICAL PREDICTION MODEL FOR HUMAN SWEAT RATE RESPONSES TO OUTDOOR ENVIRONMENTAL-CONDITIONS

Based on indoor laboratory studies, a mathematical model to predict sw eat loss response was suggested as follows: m(sw) = 27.9E(req)(E(max)) (-0.455) (g . m(-2). h(-1)) Under outdoor conditions this model was ov er estimating sweat loss response in shaded (low solar radiation) envi ronments, and underestimating the response when solar radiation was hi gh (open field areas). The present study was conducted in order to adj ust the model to be applicable under outdoor environmental conditions. Four groups of fit acclimated subjects participated in the study. The y were exposed to three climatic conditions (30 degrees, 65% rh; 31 de grees C, 40% rh; and 40 degrees C, 20% rh) and three levels of metabol ic rate (100, 300 and 450 W) in shaded and sunny areas while wearing s horts, cotton fatigues (BDUs) or protective garments. The original pre dictive equation for sweat loss was adjusted for the outdoor condition s by evaluating separately the radiative heat exchange, short-wave abs orption in the body and long-wave emission from the body to the atmosp here and integrating them in the required evaporation component (E(req )) of the model, as follows: H-r = 1.5SL(0.6)/I-T (watt) H-l = 0.047M( e.th)/I-T (watt), where SL is solar radiation (W . m(-2)), M(e.th) is the Stephan Boltzman constant, and I-T is the effective clothing insul ation coefficient. This adjustment revealed a high correlation between the measured and expected values of sweat loss (r = 0.99, p < 0.0001) .