2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
As the lowering of resting values was also found in a neutral climate, and this leads to the
hypothesis that during the acclimation to moderate heat stress (WBGT = 33.5°C in present
study), the lowering of resting Tco is mainly due to the physical work performed. Whether
higher heat stress levels that are known to provoke greater acclimation effects on final Tco
may also enhance the observed effects on resting Tco should be a subject of future research.
Additionally, our results reveal a high inter-individual variability with some persons even
showing increases of resting as well as of final Tco during heat acclimation. The potential
influence of effect modifying variables like physical fitness or gender could not be identified
in this study, because they were either not observed, or due to the low fraction of female
participants. There are efforts to extend the database to answer some of these questions.
To conclude, our analyses provide evidence that the acclimation process is accompanied by a
lowering in resting core temperature that accounts for a substantial part of the reduced
physiological strain. This may be considered when predicting effects of heat acclimatization
(Givoni and Goldman, 1973), or may lead to modifications of analytical models of
thermoregulation.
REFERENCES
Buono, M.J., Heaney, J.H., Canine, K.M., 1998. Acclimation to humid heat lowers resting
core temperature. Am. J. Physiol. (Regulatory Integrative Comp. Physiol.) 274, R1295-
R1299.
Givoni, B., Goldman, R.F., 1973. Predicting effects of heat acclimatization on heart rate and
rectal temperature. J. Appl. Physiol. 35.6, 875-879.
Griefahn, B., 1997. Acclimation to three different hot climates with equivalent wet bulb globe
temperatures. Ergonomics 40, 223-234.
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