| Co-Investigator(Kenkyū-buntansha) |
INOUE Yoshimitsu Osaka International University, Faculty of Human Science, Professor (70144566)
MATSUMOTO Taknki Chukyo University, Faculty of Sports Science, Professor (60199875)
KONDO Narihiko Kobe University, Faculty of Human Development, Professor (70215458)
UEDA Hiroyuki Osaka Shin-ai College, Department of Human and Environmental Studies, Professor (00203448)
|
|---|
| Research Abstract |
In this study, physically trained Thai and Japanese males and untrained Thai and Japanese males participated in the foot-bath test (by placing the lower legs and feet in a water bath at 42C while sitting in conditions of 28C and 60%RH for 40 min), cycle exercise test (a continuous graded cycling exercise in the semi-supine position at intensities of 35, 50, and 65% of VO2max for 20 min each without rest between intensities), and acetylcholine (ACh)-induced sweating test (by the iontophoresis method using a direct current of 2 mA for 5 min) to examine the characteristics of heat loss responses in tropical natives. The results from the foot-bath test and cycle exercise, suggested that, compared with Japanese men, heat loss from Thai men depends more on cutaneous vasodilation than on sweating, and that sweating function can be suppressed by long-term heat acclimation and enhanced by physical training. The modifications of sweating function by long-term heat acclimation and by physical tra
… More
ining were also observed in the axon reflex-mediated (AXR) sweating and directly activated (DIR) sweating responses in the ACh-induced sweating test. These results suggested that the modifications by long-term heat acclimation and by physical training were due to modifications of peripheral mechanisms involving sudomotor nerve fibres (from the results of AXR) and of the sweat gland itself and its surroundings (from the results of DIR).
Furthermore, Thai prepubertal boys, young men, and older men and Japanese young men and older men participated in the foot-bath test and the ACh-induced sweating test to examine maturation-and aging-related changes of heat loss responses (especially sweating mechanisms) in tropical natives. We found in the foot-bath tests that, compared to young men, Thai boys showed greater skin blood flow despite a lower sweating rate, and Thai older men presented lower sweat rate and skin blood flow. The lower sweat rate observed in the boys and older men was due to lower sweat gland output (SGO), not to a lower number of sweat glands (ASG). In the Ach-induced sweating test, the boys showed lower DIR sweat rate (but not AXR) compared to the young men, and the lower DIR was due to lower SGO. The older men presented lower AXR and DIR sweat rates, and the lower rate was due to lower ASG and/or SGO. Our results suggested that maturation-and aging-related changes in heat loss responses occurred in Thai natives, who have different strategies to adapt to heat stress, but the rates of change in Thai natives were smaller than in Japanese. Therefore, the effect of long-term heat acclimation was most remarkable in young men. Less
|
