Determination of the individual state of acclimatization

An attempt was made to define a subject's state of acclimatization in terms of the reactions of several physiological variables (sweat rate, core temperature, heart rate) to a heat stress test. For this purpose, four subjects performed work in a warm environment (34·C. 30% RH) both before and after an acclimation procedure to heat (40·C.20% RH). The overall effect of acclimation was similar to results described in the literature: lower heart rate. higher sweat sensitivity. lower core temperature. Individual effects, however, were more difficult to interprete. Qualitatively, they all showed the above mentioned changes, but comparing their individual physiological reactions. differences could be observed. Ranking orders for their acclimatization state, based on their heart rate response, were different from those based on core temperature and sweat rate-core temperature relation responses. It appears that the heart rate core temperature and sweat rate-core temperature relations are correlated to the acclimatization state, whereas the heart-rate response is also strongly influenced by a subjects fitness level. However, these relations, as well as the influence of % body fat etc., need further study, using a larger number of subjects.