HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 95/4/1493    most recent 00344.2002v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science 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 ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Daley, J. C. Articles by Sinoway, L. I. Search for Related Content PubMed PubMed Citation Articles by Daley, J. C., III Articles by Sinoway, L. I.

Autonomic and vascular responses to reduced limb perfusion

Divisions of ¹Pulmonary, Allergy, and Critical Care and ²Cardiology, The Pennsylvania State University College of Medicine, The Milton S. Hershey Medical Center, Hershey 17033; and ³Lebanon Veterans Affairs Medical Center, Lebanon, Pennsylvania 17042

Submitted 17 April 2002 ; accepted in final form 23 June 2003

The purpose of this study was to examine hemodynamic responses to graded muscle reflex engagement in human subjects. We studied seven healthy human volunteers [24 ± 2 (SE) yr old; 4 men, 3 women] performing rhythmic handgrip exercise [40% maximal voluntary contraction (MVC)] during ambient and positive pressure exercise (+10 to +50 mmHg in 10-mmHg increments every minute). Muscle sympathetic nerve activity (MSNA), mean arterial blood pressure (MAP), and mean blood velocity were recorded. Plasma lactate, hydrogen ion concentration, and oxyhemoglobin saturation were measured from venous blood. Ischemic exercise resulted in a greater rise in both MSNA and MAP vs. nonischemic exercise. These heightened autonomic responses were noted at +40 and +50 mmHg. Each level of positive pressure was associated with an immediate fall in flow velocity and forearm perfusion pressure. However, during each minute, perfusion pressure increased progressively. For positive pressure of +10 to +40 mmHg, this was associated with restoration of flow velocity. However, at +50 mmHg, flow was not restored. This inability to restore flow was seen at a time when the muscle reflex was clearly engaged (increased MSNA). We believe that these findings are consistent with the hypothesis that before the muscle reflex is clearly engaged, flow to muscle is enhanced by a process that raises perfusion pressure. Once the muscle reflex is clearly engaged and MSNA is augmented, flow to muscle is no longer restored by a similar rise in perfusion pressure, suggesting that active vasoconstriction within muscle is occurring at +50 mmHg.

muscle blood flow; sympathetic nervous system; ischemia

This article has been cited by other articles:

				D. S. O'Leary and M. J. Joyner Point: The muscle metaboreflex does restore blood flow to contracting muscles J Appl Physiol, January 1, 2006; 100(1): 357 - 361. [Full Text] [PDF]