result, both core and skin temperatures can rise excessively and result in high levels of sweat output, which cannot evaporate within the garments. For example, during light-to moderate-intensity (about 150 to 400 watts) exercise in hot environments, soldiers wearing NBC clothing routinely have sweating rates of 1 to 2 liters per hour (Muza et al., 1988; Pimental et al., 1987).
For athletes, the highest sweating rates occur during prolonged highintensity exercise in the heat. Figure 3-6 (Sawka and Pandolf, 1990) provides an approximation of hourly sweating rates and, therefore, water requirements for runners based on metabolic rate data from several laboratories. The sweating rates were predicted by the equation developed by Shapiro et al. (1982). The amount of body fluid lost as sweat can vary greatly, and sweating rates of 1 liter per hour are very common. The highest sweating