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dc.contributor.authorKing, Trevoren
dc.date2012-09-06 14:31:50.467
dc.date.accessioned2012-09-06T23:29:35Z
dc.date.available2012-09-06T23:29:35Z
dc.date.issued2012-09-06
dc.identifier.urihttp://hdl.handle.net/1974/7427
dc.descriptionThesis (Master, Kinesiology & Health Studies) -- Queen's University, 2012-09-06 14:31:50.467en
dc.description.abstractShear stress is the frictional force exerted on the vascular wall by blood flowing through an artery. It is a major regulator of endothelial cell function, which is essential for vasoprotection and local regulation of vascular tone. Using handgrip exercise (HGEX) to increase shear stress is an increasingly popular method for assessing brachial artery (BA) endothelial cell function via flow-mediated dilation (FMD, dilation which increases with improved endothelial function). However, different exercise duty-cycles (ratio of handgrip relaxation to contraction in seconds) produce different patterns of BA shear stress with different anterograde and retrograde flow magnitudes. PURPOSE: To determine the impact of HGEX duty-cycle on BA %FMD while maintaining a constant mean shear stress. METHODS: N=16 healthy males. BA diameter (BAD) and blood velocity (BV) were assessed via echo and Doppler ultrasound. Shear stress was estimated as shear rate (SR=BV/BAD) and reported as mean SR during the last minute of baseline (target 10 s 1) and each minute of HGEX (75 s-1). Subjects performed 3 six minute HGEX trials on each of 2 separate days (like trials averaged). Each trial was one of 3 randomly ordered HGEX duty-cycles (1:1, 3:1, 5:1). %FMD was calculated as the increase in BAD from baseline to the end of HGEX and at each minute (subset N=10) during HGEX. RESULTS: Data are means ± SD. As intended, mean SR was similar between duty-cycles (main effect, p=0.835), despite significant differences in anterograde and retrograde SR (P<0.001). There was no impact of duty cycle on blood pressure (p=0.188) or heart rate (p=0.131) responses. End exercise %FMD (4.0 ± 1.3%, 4.1 ± 2.2%, 4.2 ± 1.4%, p=0.860) and minute by minute %FMD (main effect p=0.939; interaction, p=0.545) were also not different between duty-cycles. CONCLUSION: Distinct HGEX duty-cycles create markedly different shear stress patterns in the BA. However, duty cycle had no impact on %FMD magnitude suggesting that mean shear stress is the most important stimulus for FMD in the BA. Using a 5:1 duty cycle may yield the best vessel image and diameter measurement quality due to the long period of arm stability between contractions.en
dc.language.isoengen
dc.relation.ispartofseriesCanadian thesesen
dc.rightsThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.en
dc.subjectEndothelial Functionen
dc.subjectFlow Mediated Dilationen
dc.titleThe Effect of Handgrip Exercise Duty Cycle on Brachial Artery Flow Mediated Dilationen
dc.typethesisen
dc.description.degreeMaster of Scienceen
dc.contributor.supervisorPyke, Kyra E.en
dc.contributor.departmentKinesiology and Health Studiesen
dc.degree.grantorQueen's University at Kingstonen


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