Journal of Applied Physiology, Vol 43, Issue 4 684-688, Copyright © 1977 by American Physiological Society
Prediction of heat tolerance from heart rate and rectal temperature in a temperate environment
E. Shvartz, S. Shibolet, A. Meroz, A. Magazanik and Y. Shapiro
To determine if heat tolerance could be predicted from responses to
exercise in temperature conditions, 51 young men performed 15 min of bench
stepping at an average work load of 80 W at 23 degrees C. On the following
day they attempted to perform 3 h of bench stepping at 40 W in heat (39.3
degrees C dry bulb, 30.3 degrees C wet bulb). Of these subjects, 4 were
heat intolerant, judged by previous heat stroke episodes during field
marches, 12 were heat acclimated, and 35 were unacclimated. The
heat-intolerant subjects showed the highest heart rates (HR) and rectal
temperatures (Tre) at 23 degrees C and in heat, and the acclimated subjects
showed the lowest corresponding values. HR and Tre in each environment were
combined into a single score, from 10, indicating the poorest responses, to
100, indicating the best responses. These scores at 23 degrees C when
correlated with the corresponding scores in heat resulted in a linear
correlation coefficient of r = 0.94 with a standard error of estimate of
8.6%. Scores of the heat-intolerant subjects were below 35, and those of
the acclimated subjects were between 70 and 100. Thus heat tolerance can
accurately be predicted for HR and Tre responses to exercise at room
temperature.
