Journal of Applied Physiology, Vol 44, Issue 6 918-925, Copyright © 1978 by American Physiological Society
Physiological and biophysical limits to work in the heat for clothed men and women
E. Kamon, B. Avellini and J. Krajewski
Heat-acclimated, lightly clothed men and women (four of each) walked on a
treadmill at 25% and 43% VO2 max, respectively, (M =194 W.m-2), under seven
air temperatures (Ta) ranging from 36 to 52 degrees C. Each experiment
involved 1 h of fixed and a 2nd h of progressively increasing ambient vapor
pressure (Pa). The relative steady state of rectal temperature (Tre), mean
skin temperature (Tsk), and heart rate (HR) reached in the 1st h were
forced upward during the 2nd h by the rising Pa. The critical air vapor
pressure (Pcrit) was identified by the Tre point of inflection for each Ta.
One man did not fully reach steady state, but inflection could be
determined for his physiological responses. The mean values of all points
of inflection were calculated for Tre, Tsk, and HR. Significant sex
difference in HR was found only by excluding the results of the one man.
Tre and Tsk showed no significant difference between men and women. The
coefficient for evaporative heat transfer (he), which could be derived
using the Pcrit for the low Ta range, was 14.5 +/- 2.2 W.m-1 Torr-1.
