Accession Number:

ADA093194

Title:

Physiological and Hematological Responses to Summer and Winter Dry-Heat Acclimation,

Descriptive Note:

Corporate Author:

ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA

Report Date:

1980-07-25

Pagination or Media Count:

36.0

Abstract:

Differences between acclimation to heat at the end of winter W and at the end of summer S were studied on the same 8 male volunteers. Subjects were exposed to 40 C, 30 rh for 10 days on two separate occasions approximately 5 months apart S and W. Daily exposures lasted 120 min 10 min rest, 50 min walking 1.34ms on the level, 10 min rest, 50 min walking. During W acclimation, rectal temperature Tre and heart rate HR decreased, sweat rate msw remained unchanged, and plasma and red cell volume of the blood expanded. During S acclimation, HR decreased while Tre and msw remained unchanged, and plasma volume increased. The Tre of the acclimated subjects remained higher in W and msw lower than in S. It was concluded that acclimation does not totally eliminate the seasonal differences in thermoregulatory set-point and sweat sensitivity. Further, acclimation to a more severe heat did not improve the thermoregulatory set-point that was achieved by natural acclimatization to a milder heat, but affected the cardiovascular adjustment and caused greater plasma volume expansion. W acclimation caused both plasma and blood cell volume expansion while S acclimation affected only plasma volume. Author

Subject Categories:

  • Meteorology
  • Anatomy and Physiology
  • Stress Physiology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE