Cutaneous vascular and sudomotor responses to isometric exercise in
humans.
Crandall, Craig G., James Musick, John P. Hatch, Dean L. Kellogg, Jr,
and John M. Johnson.
Departments of Physiology, Medicine, and Psychiatry, The University
of Texas, Health Science Center of San Antonio, San Antonio, TX
78284, and Department of Physiology and Biophysics, University of
Washington School of Medicine, Seattle, WA 98195
APStracts 2:0352A, 1995.
To identify whether isometric handgrip exercise (IHG) affects
cutaneous vasoconstrictor and/or active vasodilator activities, seven
subjects (6 male and 1 female) performed 30% maximal voluntary
contraction of a forearm under normothermic (1 bout) and hyperthermic
(2 bouts) conditions. Skin blood flow was indexed by laser-Doppler
flowmetry at a contralateral forearm site at which adrenergic
vasoconstrictor function was blocked by iontophoresis of bretylium
tosylate and therefore only has active vasodilation as a mechanism
for reflex control. Skin blood flow was also monitored at an adjacent
untreated site. Cutaneous vascular conductance (CVC) was calculated
from the flow signal and non-invasive blood pressure. CVC was
normalized to the value obtained from maximal vasodilation at that
site. Sweat rate (SR) was measured at the same locations. During
normothermia, IHG did not affect CVC at either the control or
bretylium-treated sites; nor did IHG affect SR (p>0.05). The
second bout of IHG in hyperthermia evoked significant reductions in
CVC at both the untreated (69.4+/-3.4 to 58.9+/-2.5% of maximum,
P<0.05) and bretylium-treated sites (75.4+/-6.1 to 64.4+/-6.2%
of maximum, P<0.05), whereas SR significantly increased (0.62+/
-0.16 to 0.70+/-0.17 mg.cm-2.min-1, P<0.05). These findings
uniquely show that, in hyperthermia, IHG reduces active vasodilator
activity while at the same time sudomotor activity is increasing.
This suggests independent control of these effectors.
Received 10 April 1995; accepted in final form 31 July 1995.
APS Manuscript Number A389-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.