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FIGURE 4-18 Approximate daily water requirements as a function of climatic temperature (Wet Bulb Globe Temperature, WBGT) and total energy expenditure (kcal). Reprinted with permission from Sawka and Montain (2001). Copyright 2001 by International Life Sciences Institute.

tized persons forced to work at very high metabolic rates for an extended period of time.

Figure 4-17 presents a graph published a number of years ago by the U.S. Army (1959) that displays daily fluid (water) requirements for soldiers living in hot climates under three conditions. It should be noted that no indication was given as to the type of data used to develop this graph. The analysis did not specify the exact metabolic rates (kcal/day) or climatic heat stress (e.g., radiant heat, humidity, air motion). Note that if the daily mean temperature was 30°C (86°F), the daily water requirements estimated in this graph approximate 12 qt (11.4 L) if working 8 hours per day and 4 qt (3.8 L) if resting in the shade. The figure suggests that in extreme heat stress and activity conditions, the daily water requirements could be greater than 20 qt (19 L).

Daily fluid (water) requirements have been estimated based upon mathematical modeling of sweating rates for a given environmental

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