Core temperature and sweating onset in humans acclimated to heat given at a fixed daily time

Citation
O. Shido et al., Core temperature and sweating onset in humans acclimated to heat given at a fixed daily time, AM J P-REG, 45(4), 1999, pp. R1095-R1101
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physiology
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
ISSN journal
0363-6119 → ACNP
Volume
45
Issue
4
Year of publication
1999
Pages
R1095 - R1101
Database
ISI
SICI code
0363-6119(199904)45:4<R1095:CTASOI>2.0.ZU;2-O
Abstract
The thermoregulatory functions of rats acclimated to heat given daily at a fixed time are altered, especially during the period in which they were pre viously exposed to heat. In this study, we investigated the existence of si milar phenomena in humans. Volunteers were exposed to an ambient temperatur e (T-a) of 46 degrees C and a relative humidity of 20% for 4 h (1400-1800) for 9-10 consecutive days. In the first experiment, the rectal temperatures (T-re) of six subjects were measured over 24 h at a T-a of 27 degrees C wi th and without heat acclimation. Heat acclimation significantly lowered T-r e only between 1400 and 1800. In the second experiment, six subjects rested in a chair at a T-a of 28 degrees C and a relative humidity of 40% with bo th legs immersed in warm water (42 degrees C) for 30 min. The T-re and swea ting rates at the forearm and chest were measured. Measurements were made i n the morning (0900-1100) and afternoon (1500-1700) on the same day before and after heat acclimation. Heat acclimation shortened the sweating latency and decreased the threshold T-re for sweating. However, these changes were significant only in the afternoon. The results suggest that repeated heat exposure in humans, limited to a fixed time daily, alters the core temperat ure level and thermoregulatory function, especially during the period in wh ich the subjects had previously been exposed to heat.