Korean J Physiol Pharmacol.  2007 Dec;11(6):233-237.

Long-Term Tropical Residency Diminishes Central Sudomotor Sensitivities in Male Subjects

• Lee JB
• Bae JS
• Shin YO
• Kang JC
• Matsumoto
• Toktasynovna AA
• Kaimovich
• Kim WJ
• Min YK
• Yang HM

Abstract

Tropical natives (TROP) are capable of tolerating tropical heat because of their long-term adaptation to tropical environments. When exposed to heat stress, these natives tend to respond with lower sweat output, which is generally thought to be the result of heat acclimatization. The main objective of this study was to clarify central mechanisms inherent to suppressed thermal sweating in tropical natives (Malaysians) by comparing their sweating responses to those of temperate native (TEMP) (Koreans). This experiment was conducted in a thermoneutral climatic chamber (24+/-0.5 degrees C, 40+/-3% relative humidity). Heat loads were applied to each subject by the immersion of their lower legs in a hot water bath (43 degrees C for 30 min). Sweat onset-time and sweat volume were compared between TROP and TEMP. The sweat onset-times on four selected points on the body ranged from 10.25 to 13.47 min in TEMP subjects, and from 16.24 to 17.83 min in TROP subjects (p<0.001). The local sweat volumes at the same sites ranged from 4.30 to 9.74 mg/cm2 in TEMP subjects, and from between 1.80 to 4.40 mg/cm2 in TROP subjects (p<0.001). These results demonstrated a significant difference between TROP and TEMP subjects with regard to the manner in which they regulate their body temperatures when exposed to heat loads, and verified that long-term thermal adaptation blunts sweating sensitivities.

Keyword

Heat tolerance; Sweating; Central sudomotor; Environmental adaptation

MeSH Terms

Acclimatization
Baths
Body Temperature
Hot Temperature
Humans
Immersion
Internship and Residency*
Leg
Male*
Population Groups
Sweat
Sweating
Water
Water