Journal of Applied Physiology, Vol 56, Issue 4 896-899, Copyright © 1984 by American Physiological Society
Heat exchange following atropine injection before and after heat acclimation
M. A. Kolka, W. L. Holden and R. R. Gonzalez
The effect of saline and atropine injection (2 mg, im) on eight healthy
male subjects before and after heat acclimation was studied while each
subject walked on a treadmill (1.34 m X s-1) in a hot-dry environment
(ambient temperature = 48.4 degrees C, dew-point temperature = 20.5 degrees
C). Partitional calorimetric analysis was done for the periods in which
maximum sweat inhibition occurred (30 min). Mean skin temperature, rectal
temperature, and heart rate were continuously observed. Evaporative loss
from the skin was calculated by changes in body weight (Sauter balance);
heat transfer coefficients were defined by Nishi equations. A prediction of
sweat inhibition based on an analysis of heat storage and its effect on a
theoretical temperature, which can be graphed on a psychrometric chart, was
developed. A rational effective temperature (ET) defined as the operative
temperature at the intersection of the 50% rh, which encompasses total heat
exchange, was used to compare the effects of atropine before and after heat
acclimation. The results show that heat acclimation reduced ET by
approximately 2.5 degrees C when compared with the unacclimated state after
atropine injection. Thus heat acclimation reduces the hazards of heatstroke
caused by exercise in the heat with atropine injection.
