Physiological Responses to WBGT-Equivalent Environments and Two Clothing Types during Simulated Desert Marches

The purpose of this investigation was two-fold: (1) to determine if hot-wet and hot-dry environments were equally stressful to the exercising individual and (2) to examine the effects of clothing (shorts vs modified Battle Dress Uniform) worn while exercising in both environments. The physiological...

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Bibliographic Details
Main Authors: Armstrong, Lawrence E, Szlyk, Patricia C, Hubbard, Roger W, Engell, Dianne B, Sils, Ingrid V
Format: Report
Language:English
Subjects:
ARMY PERSONNEL
BLOOD VOLUME
BODY TEMPERATURE
CONSUMPTION
DRY CLIMATE
ELECTROLYTES(PHYSIOLOGY)
EXERCISE(PHYSIOLOGY)
EXHAUSTION(PSYCHOLOGICAL)
HEAT STRESS(PHYSIOLOGY)
HEAT STROKE
HIDROMEIOSIS
HIGH HUMIDITY
HIGH TEMPERATURE
HYPERTHERMIA
OXYGEN CONSUMPTION
PERSPIRATION
Stress Physiology
SWEAT COOLING
UNIFORMS
VENTILATION
WALKING
WATER
WET BULB TEMPERATURE
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Summary:The purpose of this investigation was two-fold: (1) to determine if hot-wet and hot-dry environments were equally stressful to the exercising individual and (2) to examine the effects of clothing (shorts vs modified Battle Dress Uniform) worn while exercising in both environments. The physiological effects of exercise in a hot-humid environment (89 F, 80% RH) have been compared to those of exercise in a hot-dry environment (104 F, 28% RH), both equivalent to a WBGT temperature of 86.5 F. Six male soldiers walked on a treadmill in a climatic chamber, simulating a 3 hr desert march. Each soldier underwent five trials, on non-consecutive days: warm-dry in shorts, hot-wet in shorts, hot-wet in BDU, hot-dry in shorts, and hot-dry in BDU. Many significant differences (p. 05) in physiological responses were measured. We concluded that: (1) the modified BDU compounded the effects of the hot-wet environment; (2) different responses were observed in hot-wet vs hot-dry environments; (3) increasing the humidity from 48% to 80% (at 89 F) resulted in an elevated rectal temperature and a reduced plasma volume post-exercise; (4) significant hidromeiosis occurred only during the hot-wet BDU trial; (5) sweat rate (but not sweat electrolyte losses), ventilation, and change in rectal temperature varied between trials, possibly explaining why symptoms of heat exhaustion and heat stroke vary between patients; and (6) equivalent physiological responses will not occur simply because hot-wet and hot-dry environments have equivalent WBGT values.