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This Article Full Text Full Text (PDF) All Versions of this Article: 92/5/841    most recent expphysiol.2007.037937v1 Alert me when this article is cited Alert me if a correction is posted 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 Google Scholar Google Scholar Articles by Zamir, M. Articles by Shoemaker, J. K. Search for Related Content PubMed PubMed Citation Articles by Zamir, M. Articles by Shoemaker, J. K.

¹ Departments of Applied Mathematics and of Medical Biophysics² School of Kinesiology³ Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario N6A 3K7, Canada

The current view of neurogenic vasomotor control in skeletal muscle is based largely on changes in vascular bed resistance. The purpose of this study was to determine to what extent vascular bed compliance may also play a role in this regulation. For this purpose, pressure waveforms (Millar and Finometer) and flow waveforms (Doppler ultrasound) were measured simultaneously in the brachial artery of seven healthy individuals during physiological manoeuvres which were expected to produce non-neurogenic changes in resistance (wrist-cuff occlusion; n = 5) or compliance (arm elevation; n = 6) of the forearm vascular bed. Vascular resistance (R) was calculated from the average flow and pressure values. A lumped Windkessel model was used to obtain vascular bed compliance (C) from these concurrently measured waveforms. Compared with baseline (3.81 ± 1.59 ml min^–1 mmHg^–1), wrist occlusion increased R (65 ± 75%; P < 0.05) with minimal change in C (–15 ± 16%; n.s.). Compared with the arm in neutral position (0.0075 ± 0.003 ml mmHg^–1), elevation of the arm above heart level produced a 86 ± 41% increase in C (P < 0.05) with little change in R (–5 ± 11%). In addition, neurogenic changes were assessed during lower body negative pressure (LBNP) and a cold pressor test (CPT; n = 7). Lower body negative pressure induced a 29 ± 24% increase in R and a 26 ± 12% decrease in C (both P < 0.05). The CPT induced no consistent change in R but a 22 ± 7% reduction in C (P < 0.05). It was concluded that vascular bed compliance is an independent variable which should be considered along with vascular bed resistance in the mechanics of vasomotor regulation in skeletal muscle.

(Received 23 March 2007; accepted after revision 29 May 2007; first published online 1 June 2007)
Corresponding author J. K. Shoemaker: Neurovascular Research Laboratory, School of Kinesiology, Room 3110 Thames Hall, The University of Western Ontario, London, Ontario, N6A 3K7, Canada. Email: kshoemak{at}uwo.ca