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Annual Workshop on Space Operations Applications and Research (SOAR '93) (7th). Volume 2. Proceedings of a Workshop held in Houston, Texas on August 3 - 5, 1993.

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Several studies have shown that individuals consuming low-salt diets and working in the heat have an increased risk or incidence of heat injury, suggestive of inadequate cardiovascular adjustment. Furthermore, others have shown that prolonged work in hot climates can precipitate orthostatic hypotension and syncope. This study was designed to evaluate the effects of moderate-salt MS and low-salt LS diets on the circulatory responses and incidence of presyncopal symptoms to an orthostatic test OT during successive days of heat acclimation HA. Seventeen unacclimatized male soldiers mean - SEage, 20 - 1 yrs participated in this two-phase study. The first phase consisted of a seven day dietary stabilization period during which all subjects consumed similar diets of about 4000 kcalday containing 8g NaCl and lived in a dormitory setting 21 deg C, 30 RH. The second phase commenced on day eight and consisted of dietary NaCl restriction and 10 days HA days 8-17. Volunteers were randomly assigned to either the MS diet n9 providing 8g NaClday or the LS diet n8 furnished just 4g NaClday. The acquisition of HA was manifested on both groups by reductions in exercising rectal temperature and heart rate HR these characteristics were similar in the MS and LS diets. The OT was performed at 21 deg C on day seven of the stabilization phase and on days 9, 11, 13, 15, and 17 of the HA phase, before and after 8.5 hr of intermittent treadmill working 30 minhr, 5.6 kmhr, 5 grade in a hot environment 41 deg C, 21 RH, 1.2 msec windspeed. Blood pressure BP and HR responses at 1, 2 and 4 min and any presyncopal symptoms were recorded after assuming an upright position from recumbency.

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  • Stress Physiology

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