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Cold Acclimation Can Be Induced in Humans by Repeated Cold Water Immersion,
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA
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The effects of repeated cold water immersion on thermoregulatory responses to cold air were studied in seven males. A cold air stress test CAST was performed before and after completion of an acclimation program consisting of daily 90-min cold 18C water immersion, repeated 5 timeswk for 5 consecutive wk. The CAST consisted of resting 30 min in a comfortable 24C, 30 relative humidity rh environment followed by 90 min in cold 5C, 30 rh air. Pre- and post-acclimation, metabolism M increased P0.01 by 85 during the first 10 min of CAST and thereafter rose slowly. After acclimation, M was lower P0.02 at 10 min of CAST compared with before, but by 30 min M was the same. Therefore, shivering onset may have been delayed following acclimation. After acclimation, rectal temperature T sub re was lower P0.01 before and during CAST, and the drop in T sub re during CAST was greater p0.01 than before. Mean weighted skin temperature T sub sk was lower p0.01 following acclimation than before, and acclimation resulted in a larger P0.02 T re to T sk gradient. Plasma norepinephrine increased during both CAST p0.002, but the increase was larger P0.004 following acclimation. These findings suggest that repeated cold water immersion stimulates development of true cold acclimation in humans as opposed to habituation. The cold acclimation produced appears to be of the insulative type.
APPROVED FOR PUBLIC RELEASE