Correlative relationships of response patterns between body temperature, sweat rate and sodium concentration in sweat during heat exposure in man.

Abstract

Sweating and body temperature response were studied in a total of 268 Japanese (non-Ainu Japanese and Ainu Japanese) of various groups which differed in sex, racial and ecological status. The pattern of response for the whole period of heat application was used for the analysis of the observations. In order to arrive at determinants of body temperature response-equilibrium body temperature, rise of body temperature at the equilibrium period, and slope of changes in body temperature in the post-equilibrium period were calculated. Sweating function was represented by the determinants such as peak rate of sweating, peak Na concentration in sweat, slope of changes in the rate of sweating as well as in Na concentration in sweat in the post-equilibrium period. Latent time of sweat suppression after the maximum sweating was also measured. Sweating types were assigned to individuals according to the criteria previously reported. Correlations between determinants above mentioned were examined and discussed from point of view of heat adaptability. The results are summarized as follows:1) Latent time and rate of sweat suppression correlates well with body temperature response in the following manner; in subjects in whom sweat suppression progressed rapidly with a short latent time, the rise of body temperature at the equilibrium period was small. In these subjects, body temperature tended to decline more markedly in the postequilibrium period.2) It was found that the sweat rate and body temperature not always changed in the same direction in the post-equilibrium period, thus it follows that no causual relationships exist between the two in this period. Na concentration in sweat changed in most cases in parallel with the sweat rate in the post-equilibrium period. However, it was observed in not a few subjects that Na concentration increased while the sweat rate was decreasing. In these subjects, body temperature showed less tendency to decline, or conversely, a tendency to rise again even after the equilibration of body temperature was once established.3) The analysis of the correlation between “sweating types” and determinants for body temperature response and sweating pattern revealed inter-sweating types differences in most of the determinants with a statistical significance. The equilibrium body temperature after heat application was lower in sweating types 2 and 4 than in types 1 and 3. The rise in equilibrium body temperature from the initial temperature showed a similar tendency to the above according to sweating types, i. e. smaller in types 2 and 4 than in types 1 and 3. Also, the body temperature tended to decline in the post-equilibrium period more markedly in the former types than in the latter types. Sweat suppression was produced more rapidly in type 4 than in types 1 and 3. It was suggested that there are inborn differences in sweating responses among individuals which may play some role in heat adaptability.