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2) Ohara's sweating type method, representing a relation between local sweat rate and sodium concentration in sweat, was modified by using salt loss in place of sodium concentration. Sweating patterns were classified into U, N, and T Types in the Q' (salt loss)-V (peak sweat rate) plane. Type U corresponds to Ohara's Type 1, the least heat tolerant, and Type T corresponds to Ohara's Type 4, the most heat tolerant.3) Results obtained with the authors' method and Index I coordinated well. Type U showed the highest value of Index I, Type T the lowest which suggest that the lower value of Index I indicates a greater heat tolerance.4) The three type method and Index S revealed no significant correlation, which suggests that Index S is not a measure to be applied to heat tolerance. It was discussed that Index S may be utilized as an index to represent effectiveness of homeostatic mechanism to thermal regulation. 5) Ohara's four sweating types and Index I showed no significant correlation. Thus, the three-type method appears to be a more satisfactory tool for examining heat tolerance.As an index for determining heat adaptability, OHARA (1967) proposed

ABSTRACT.-We proposed a numerical index for evaluating human heat tolerance which is practically useful. The adaptive changes in heat tolerance of unacclimatized subjects during short-term heat acclimatization could be evaluated by this index. The present investigation was performed to examine whether or not our index can reflect effects on heat tolerance of a long-term acclimatization as seen in subtropical natives. Nineteen young male residents born and raised in Okinawa (subtropical zone), 18 male residents born in the Japan Main Islands (temperate zone) but moved to Okinawa and 25 male students in Kyoto (temperate zone) were chosen to be subjects. Their age were from 19 to 29 years. Sweating reaction was examined for 60 rain in summer, by immersing legs in stirring water of 42°C by using a mobile climatic chamber of 30oc with 70 RH. Local sweat samples from the chest and back were collected at 15 rain interval by the filter paper method. Sweating reaction of the residents born and raised in Okinawa was characterized by smaller volume of sweating and lower salt concentration in sweat, while the rise in rectal temperature and increase in heart rate differ less between the three groups. It is concluded that residents born and raised in Okinawa showed higher heat tolerance than the other two groups when assessed by our factorial index method.

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