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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
FIGURE 4-20 Approximate daily sweating rates as a function of dry-bulb temperature and level of physical activity derived from modeling available data. The hatched area indicates the ≈ 1 L minimal water requirements as described in Table 4-2. The y-axis represents the predicted water requirements that increase because of increased sweat losses to enable thermoregulation. The x-axis is the average daytime dry bulb temperature. “Very active” is equivalent to approximately 3,600 total kcal/ day of energy expenditure, “active” is equivalent to approximately 2,900 total kcal/ day of energy expenditure, “low active” is equivalent to approximately 2,400 total kcal/day of energy expenditure, and “sedentary” is equivalent to approximately 1,900 total kcal/day of energy expenditure, categories identified in estimates of energy expenditure (IOM, 2002/2005). The model used to develop this graph is further explained in Appendix C.
ference prevails even when sweating rate is corrected for skin surface area (Araki et al., 1979; Falk et al., 1992a; Wagner et al., 1972), and it becomes manifested during midpuberty. For example, while performing moderate-intensity exercise at dry climatic heat (42°C [107.6°F], 20 percent relative humidity), prepubertal boys produced ≈ 15 to 25 percent less sweat, 294 mL/m2skin/hour of sweat compared with 342 and 396 mL/m2skin/hour in mid- and late-pubertal boys, respectively (Falk et al., 1992b).