(2) Water loss must be replaced, preferably by periodic intake of small
amounts of water throughout the work period. During moderate activity, with moderate
environmental conditions, the water requirement will be one pint or more per hour per
person. This is best taken at 20 to 30 minutes intervals. As activities or conditions
become more severe, the intake should be increased accordingly.
(3) Thirst is not an adequate stimulus for water intake. Individuals with
ample water supplies will frequently dehydrate by one or two quarts unless drinking is
encouraged or required by command control. Actually, some overhydration is strongly
(4) The optimum drinking water temperature is between 50F and 60F
(10C and 16C). It is a good idea to flavor the water lightly with citrus fruit flavors (or
extracts since this makes the water more tasteful).
(5) If water is in short supply, there are two ways to economize -- reduce
physical activity or limit physical activity to early morning, evening, and night when the
heat load is less and people sweat less. DO NOT attempt to conserve water by
restricting water intake of personnel. The result is reduced work capability, reduced
efficiency, and increased risk of a heat injury.
(1) Sodium chloride as well as water is lost in sweating. A normal diet
ordinarily contains an adequate amount of salt, but additional salt may be given
cautiously during the first few days an individual is exposed to heat, especially in the
case of unacclimatized individuals. An unacclimatized person will lose a greater
amount of salt because of increased sweating than after acclimatization.
Additional salt intake can delay the rate at which the full sweat product
occurs. If salt is given in excess, a person can accumulate too much heat
and have a higher body temperature than appropriate for the heat and current
Among acclimatized individuals, the need for added salt varies.
(a) People in the older age groups tend to retain excess salt in the
body; therefore, these people need less salt after acclimatization than younger people.
(b) Under heavy heat stress when sweating is excessive, individuals
may take some additional salt, but cautiously. Excess intake of salt should be avoided
since it may cause increased thirst and incapacitating nausea. Unless individuals are
sweating continuously or repeatedly, they do not need saline fluids or salt tablets. Extra
salt in cooking, in bread, and on the plate, coupled with sound training will meet most