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TABLE 4-15 Summary of Estimated Median Daily Total Water Intake for Individuals Reporting Leisure Time Activity in the United States

Age

Males, Total Water Intake (L/d)

Females, Total Water Intake (L/d)

Least Active,a Median

Most Active,b Median

Least Active,a Median

Most Active,b Median

8–16 yr

2.11

2.69

1.78

2.29

17–18 yr

2.04

3.35

1.90

2.74

19–30 yr

3.16

3.78

2.60

2.93

31–50 yr

3.54

3.77

2.52

3.16

51–70 yr

3.22

3.42

2.81

3.06

71+ yr

2.54

3.05

2.33

2.75

a Least active = no reported leisure time activity.

b Most active = leisure time activity reported five or more times per week.

SOURCE: Third National Health and Nutrition Examination Survey, 1988–1994. Appendix Tables H-1, H-2, and H-4.

ety of average daytime ambient dry bulb temperatures (i.e., with 50 percent relative humidity and a partly cloudy sky) and varying their level of physical activity from sedentary, low active, active, and very active levels. The sweating rates were predicted by an equation developed for healthy adults that includes the effects of metabolic rate, climate, and clothing (Moran et al., 1995; Sawka et al., 1996a; Shapiro et al., 1982). Considerable variability can be expected among persons due to individual differences in body size, diet, and sweat loss responses (e.g., heat acclimatization, physical fitness, air movement). In addition, most individuals will not be constantly exposed to one environmental condition. Note that the daily water requirements for temperate conditions can double or even triple in very hot weather (≈ 40°C [104°F]). Adolph’s (1933) “minimal,” “average,” and “liberal” water requirements of 2.1, 3.4, and 5.0 L/day, respectively, are fairly consistent with this figure, except for very active persons in hot weather. The daily water requirement increases with activity and ambient temperature are a result of increased sweating to meet evaporative cooling requirements.

Active Children

Sweat production in children is considerably less than in adults under similar climatic and activity conditions (Falk, 1998). This dif-



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