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as experienced by the individual soldier exercising in the heat, are important because they are the sole indications by which the soldier judges the onset of heat injury (Armstrong et al., 1987).

In a study of the signs and symptoms of one type of heat illness—heat exhaustion—Armstrong et al. (1987) exposed 14 healthy unacclimated men to 8 days of heat acclimation by intermittent treadmill running in an environmental chamber set at 41°C, 39 percent relative humidity. During the study, the subjects experienced nine different signs and symptoms: abdominal cramps, chills, dizziness, flushed skin with ''heat sensations,'' elevated resting heart rate, hyperirritability, "rubbery" legs, piloerection, and vomiting and nausea. The incidence of these signs and symptoms decreased as the number of days of heat exposure increased. The signs and symptoms were gathered through careful clinical observations and the solicitation of the subjects' verbal reports of their experiences.

In the present study, a standardized psychological instrument, the Environmental Symptoms Questionnaire (ESQ) (Kobrick and Sampson, 1979; Sampson and Kobrick, 1980), was used to evaluate soldiers' reports of symptoms of heat illness. The ESQ is a 68-item questionnaire that measures a variety of symptoms including headache, dizziness, nausea, thirst, and cramps (Table 14-1). The ESQ is worded in the past tense, and the subject is required to reflect on symptoms experienced during the hours prior to administration. The subject rates each symptom on a 6-point scale ranging from "not at all" to "extreme." The ESQ has been successfully used to assess symptomatology under conditions of high terrestrial altitude (Banderet and Lieberman, 1989; Kobrick and Sampson, 1979; Rock et al., 1987; Sampson and Kobrick, 1980), ambient cold (Johnson et al., 1989), combat field feeding (Hirsch et al., 1984; USACDEC/USARIEM, 1986), and the administration of nerve agent antidote (Kobrick et al., 1990).

METHOD

Subjects

Seventeen healthy male U.S. Army soldiers volunteered to participate in the study. Prior to heat acclimation, all underwent 1 week of dietary stabilization (days 1 to 7) during which consumption of dietary salt was held constant at 8 g per day. On the first (day 8) of 10 days of heat acclimation (days 8 to 17), subjects were randomly, and in a double-blind fashion, assigned to either the 4-g dietary salt group (n = 8), or the 8-g dietary salt group (n = 9). Examination of selected personal characteristics (age, height, weight, and race) indicated that the two groups were comparable to one another. The subjects assigned to the 4-g salt group averaged 19.8 years old, 71.3 inches tall, and weighed 174.9 pounds; seven were Caucasian and one



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