Relationship between skin blood flow and sweating rate, and age related regional differences |
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| Authors: | Yoshimitsu Inoue Manabu Shibasaki Kozo Hirata Tsutomu Araki |
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| Institution: | (1) Laboratory for Human Performance Research, Osaka International University for Women, 6-21-57 Tohda-cho, Moriguchi, Osaka 570-8555, Japan, JP;(2) The graduate School of Science and Technology, Kobe University, Kobe 657-8505, Japan, JP;(3) Faculty of Home Economics, Kobe Women's University, Kobe 654-8585, Japan, JP;(4) Hyogo University of Teacher Education, Kato-gun 673-1461, Japan, JP |
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| Abstract: | To examine the mechanisms and regional differences in the age-related decrement of skin blood flow, 11 young (age 20–25 years)
and 10 older (age 64–76 years) men were exposed to a mild heat stress by immersing their feet and lower legs in water at 42°C
for 60 min, while they were sitting in near thermoneutral conditions 25°C and 45% relative humidity (rh)]. During the equilibrium
period (25°C and 45% rh) before the heat test, no group differences were observed in rectal (T
re) and mean skin (T
sk) temperatures or mean arterial pressure (MAP). During passive heating, T
sk was significantly lower in the older men 20 min after commencing exposure (P < 0.001), although there were similar increases in T
re in both groups. Exposure time and age did not affect MAP. The local sweating rate (m˙
sw) and the percentage change in skin blood flow by laser Doppler flowmetry (%LDF) relative to baseline values on the chest,
back, forearm and thigh were significantly lower in the older men (P < 0.001), especially on the thigh. After starting the heat exposure, three temporal phases were observed in the relationship
between %LDF and m˙
sw at most sites in each subject. In phase A, %LDF increased but with no increase in m˙
sw. In phase B, m˙
sw increased but with no secondary increase in %LDF. Finally, in phase C, there were proportional increases in %LDF and m˙
sw. The increase in %LDF in phase A was significantly lower on the forearm and thigh (P < 0.05) for the older men, but not on the chest and back. In phase C, the slopes of the regression lines between %LDF and
m˙
sw were lower for the older men on the back (P < 0.03), forearm (P = 0.08) and thigh (P < 0.03), but not on the chest. These results would suggest that the age-related decrement in skin blood flow in response
to passive heating may be due in part to a smaller release of vasoconstrictor tone and to less active vasodilatation once
sweating begins. Regional differences exist in the impaired vasoconstriction and active vasodilatation systems.
Accepted: 29 May 1998 |
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| Keywords: | Cutaneous vasodilatation Laser Doppler flowmetry Sweating Aging Heating |
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