Journal of Applied Physiology, Vol 40, Issue 1 55-59, Copyright © 1976 by American Physiological Society
Body fluid responses of heat-tolerant and intolerant men to work in a hot wet environment
L. C. Senay and R. Kok
Acclimatization to heat before proceeding underground is a requirement for
each South African mine laborer. Certain individuals among this large
population cannot be acclimatized to heat (33.3 degrees C db, 31.7 degrees
C wb) and are classified as heat intolerant. In this study certain body
fluid responses to heat and work were compared between a group of 19
heat-tolerant (HT) and of 15 heat-intolerant (HI) subjects. To the factors
known to affect heat tolerance such as age, weight, and oxygen consumption
must now be added differences in body fluid responses. The HI group of
subjects failed to hemodilute to the same degree as the HT group though
working at the same relative work loads (30% and 50% VO2 max). As the 4-h
work period (33.3 degrees C db, 31.7 degrees C wb) continued, the HI group
did not maintain hemodilution in spite of the lower absolute work loads,
sweat rates, and water deficits suffered by this group. From analysis of
blood constituent changes it was suggested that the reason for the
differences noted in body fluid dynamics concerned plasma protein
equilibrium across capillary walls as well as the protein population of
interstitial spaces.
