Heat acclimatization by controlled hyperthermia in hot-dry and hot-wet climates.

Abstract

Acclimatization by controlled hyperthermia (38.2[degree]C for 2 hr. daily for 12 days) of one group of subjects in hot-dry conditions was compared with the same exposure of a 2nd group in hot-wet conditions. Compared in the same standard tests both groups initially responded equally and after acclimatization both had developed marked and similar improvements in response. However, arm sweat measurements showed that there was a difference in the effects of the 2 climates on the sweat suppression phenomenon. Arms that had been exposed to hot-wet conditions throughout acclimatization developed a reduced rate of sweat suppression not seen in the arms exposed throughout to hot-dry conditions. This difference between acclimatization in hot-wet and hot-dry conditions could be important in determining the subjects subsequent tolerance to heat, especially when the exposure is prolonged and the conditions are humid. It is suggested that when sweat rate is used as an index of acclimatization both the maximum sweating capacity for a given increase in body temperature and the rate of sweat suppression need to be measured.