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This Article Full Text Full Text (PDF) All Versions of this Article: 565/2/667    most recent jphysiol.2005.083535v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Shibasaki, M. Articles by Crandall, C. G. Search for Related Content PubMed PubMed Citation Articles by Shibasaki, M. Articles by Crandall, C. G.

¹ Department of Human Environmental Health, Nara Women's University, Nara, Japan
² Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, TX, USA
³ Department of Anaesthesia and Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
⁴ Department of Physiology, University of Texas Health Science Center at San Antonio, TX, USA
⁵ Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA

Cutaneous vascular conductance (CVC) decreases during isometric handgrip exercise in heat stressed individuals, and we hypothesized that central command is involved in this response. Seven subjects performed 2 min of isometric handgrip exercise (35% of maximal voluntary contraction) followed by postexercise ischaemia in normothermia and during heat stress (increase in internal temperature 1°C). To augment the contribution of central command independent of force generation, on a separate day the protocol was repeated following partial neuromuscular blockade (PNB; I.V. cisatracurium). Forearm skin blood flow was measured by laser-Doppler flowmetry, and CVC was the ratio of skin blood flow to mean arterial pressure. The PNB attenuated force production despite encouragement to attain the same workload. During the heat stress trials, isometric exercise decreased CVC by 12% for both conditions, but did not change CVC in either of the normothermic trials. During isometric exercise in the heat, the increase in mean arterial pressure (MAP) was greater during the control trial relative to the PNB trial (31.0 ± 9.8 versus 18.6 ± 6.4 mmHg, P < 0.01), while the elevation of heart rate tended to be lower (19.4 ± 10.4 versus 27.4 ± 8.1 b.p.m., P = 0.15). During postexercise ischaemia, CVC and MAP returned to pre-exercise levels in the PNB trial but remained reduced in the control trial. These findings suggest that central command, as well as muscle metabo-sensitive afferent stimulation, contributes to forearm cutaneous vascular responses in heat stressed humans.

(Received 20 January 2005; accepted after revision 18 March 2005; first published online 24 March 2005)
Corresponding author C. G. Crandall: Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, 7232 Greenville Ave. Suite 435, Dallas, TX 75231, USA. Email: craigcrandall{at}texashealth.org

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