Intermittent microclimate cooling during exercise-heat stress in US army chemical protective clothing.
The effectiveness of intermittent, microclimate cooling for men who worked in US Army chemical protective clothing (modified mission-oriented protective posture level 3; MOPP 3) was examined. The hypothesis was that intermittent cooling on a 2 min on-off schedule using a liquid cooling garment (LCG) covering 72% of the body surface area would reduce heat strain comparably to constant cooling. Four male subjects completed three experiments at 30 degrees C, 30% relative humidity wearing the LCG under the MOPP 3 during 80 min of treadmill walking at 224 +/- 5 W . m(-2). Water temperature to the LCG was held constant at 21 degrees C. The experiments were; 1) constant cooling (CC); 2) intermittent cooling at 2-min intervals (IC); 3) no cooling (NC). Core temperature increased (1.6 +/- 0.2 degrees C) in NC, which was greater than IC (0.5 +/- 0.2 degrees C) and CC (0.5 +/- 0.3 degrees C) ( p < 0.05). Mean skin temperature was higher during NC (36.1 +/- 0.4 degrees C) than IC (33.7 +/- 0.6 degrees C) and CC (32.6 +/- 0.6 degrees C) and mean skin temperature was higher during IC than CC ( p < 0.05). Mean heart rate during NC (139 +/- 9 b . min(-1)) was greater than IC (110 +/- 10 b . min(-1)) and CC (107 +/- 9 b . min(-1)) ( p < 0.05). Cooling by conduction (K) during NC (94 +/- 4 W . m(-2)) was lower than IC (142 +/- 7 W . m(-2)) and CC (146 +/- 4 W . m(-2)) ( p < 0.05). These findings suggest that IC provided a favourable skin to LCG gradient for heat dissipation by conduction and reduced heat strain comparable to CC during exercise-heat stress in chemical protective clothing.
U.S. Army Research Institute of Environmental Medicine, Kansas St., Natick, MA 01760-5007, USA. bruce.cadarette@us.army.mil
Bruce S
BS
Cadarette
Samuel N
SN
Cheuvront
Margaret A
MA
Kolka
Lou A
LA
Stephenson
Scott J
SJ
Montain
Michael N
MN
Sawka
D000328:Adult; D001833:Body Temperature Regulation; D003080:Cold Temperature; D015444:Exercise / Q000502:physiology*; D015386:Hazardous Substances; D018882:Heat Stress Disorders / Q000517:prevention & control*; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D008297:Male; D008834:Microclimate; D008887:Military Medicine / Q000295:instrumentation*; D008889:Military Personnel; D005082:Physical Exertion / Q000502:physiology; D011446:Prospective Studies; D011481:Protective Clothing; D012881:Skin Temperature / Q000502:physiology*; D013997:Time Factors; D014481:United States
D015386:Hazardous Substances