Life Sciences Commons^™

Impact Of Age On Cerebrovascular Dilation Versus Reactivity To Hypercapnia., Nicole S Coverdale, Mark B Badrov, J Kevin Shoemaker

Kinesiology Publications

This study quantified the effect of age on cerebrovascular reactivity and cerebrovascular conductance while accounting for differences in grey matter volume in younger (YA: n = 12; 24 ± 4 years, six females) and older adults (OA: n = 10; 66 ± 7 years; five females). Cerebral blood flow velocity (CBFV; transcranial Doppler) in the middle cerebral artery (MCA), MCA cross-sectional area (CSA), intracranial volumes (magnetic resonance imaging), and mean arterial pressure (MAP; Finometer), were measured under normocapnic and hypercapnic (6% carbon dioxide) conditions. Cerebral blood flow (CBF) was quantified from CBFV and MCA CSA and normalized to grey matter …

Effects Of Acute And Chronic Interval Sprint Exercise Performed On A Manually Propelled Treadmill On Upper Limb Vascular Mechanics In Healthy Young Men., T Dylan Olver, Steph M Reid, Alan R Smith, Mair Zamir, Peter W R Lemon, M Harold Laughlin, J Kevin Shoemaker

Kinesiology Publications

Interval sprint exercise performed on a manually propelled treadmill, where the hands grip the handle bars, engages lower and upper limb skeletal muscle, but little is known regarding the effects of this exercise modality on the upper limb vasculature. We tested the hypotheses that an acute bout of sprint exercise and 6 weeks of training induces brachial artery (BA) and forearm vascular remodeling, favoring a more compliant system. Before and following a single bout of exercise as well as 6 weeks of training three types of vascular properties/methodologies were examined in healthy men: (1) stiffness of the entire upper limb …

Positional Differences In Reactive Hyperemia Provide Insight Into Initial Phase Of Exercise Hyperemia., Jeffrey L Jasperse, J Kevin Shoemaker, Eric J Gray, Philip S Clifford

Kinesiology Publications

Studies have reported a greater blood flow response to muscle contractions when the limb is below the heart compared with above the heart, and these results have been interpreted as evidence for a skeletal muscle pump contribution to exercise hyperemia. If limb position affects the blood flow response to other vascular challenges such as reactive hyperemia, this interpretation may not be correct. We hypothesized that the magnitude of reactive hyperemia would be greater with the limb below the heart. Brachial artery blood flow (Doppler ultrasound) and blood pressure (finger-cuff plethysmography) were measured in 10 healthy volunteers. Subjects lay supine with …

Effect Of Age On The Hemodynamic And Sympathetic Responses At The Onset Of Isometric Handgrip Exercise., Sophie Lalande, Carolyn P Sawicki, Jacquie R Baker, Kevin Shoemaker

Kinesiology Publications

Cardiac and peripheral vasomotor factors contribute to the rapid pressor response at the onset of isometric handgrip exercise. We tested the hypothesis that age enhances the sympathetic and vasoconstrictor response at the onset of isometric handgrip exercise so that the pressor response is maintained, despite a diminished cardiac function. Twelve young and twelve older (24 ± 3 and 63 ± 8 yr) individuals performed 20-s isometric handgrip exercise at 30, 40, or 50% of maximal voluntary contraction force. Muscle sympathetic nerve activity (MSNA) was measured using microneurography. Mean arterial pressure (MAP) and cardiac output (Q) were assessed continuously by finger …

Neuropeptide Y And Neurovascular Control In Skeletal Muscle And Skin., Gary J Hodges, Dwayne N Jackson, Louis Mattar, John M Johnson, J Kevin Shoemaker

Kinesiology Publications

Neuropeptide Y (NPY) is a ubiquitous peptide with multiple effects on energy metabolism, reproduction, neurogenesis, and emotion. In addition, NPY is an important sympathetic neurotransmitter involved in neurovascular regulation. Although early studies suggested that the vasoactive effects of NPY were limited to periods of high stress, there is growing evidence for the involvement of NPY on baseline vasomotor tone and sympathetically evoked vasoconstriction in vivo in both skeletal muscle and the cutaneous circulation. In Sprague-Dawley rat skeletal muscle, Y(1)-receptor activation appears to play an important role in the regulation of basal vascular conductance, and this effect is similar in magnitude …

Cortical Regions Associated With Autonomic Cardiovascular Regulation During Lower Body Negative Pressure In Humans., Derek S Kimmerly, Deborah D O'Leary, Ravi S Menon, Joseph S Gati, J Kevin Shoemaker

Kinesiology Publications

The purpose of the present study was to determine the cortical structures involved with integrated baroreceptor-mediated modulation of autonomic cardiovascular function in conscious humans independent of changes in arterial blood pressure. We assessed the brain regions associated with lower body negative pressure (LBNP)-induced baroreflex control using functional magnetic resonance imaging with blood oxygen level-dependent (BOLD) contrast in eight healthy male volunteer subjects. The levels of LBNP administered were 5, 15 and 35 mmHg. Heart rate (HR; representing the cardiovascular response) and LBNP (representing the baroreceptor activation level) were simultaneously monitored during the scanning period. In addition, estimated central venous pressure …

Critical Analysis Of Cerebrovascular Autoregulation During Repeated Head-Up Tilt., R L Hughson, M R Edwards, D D O'Leary, J K Shoemaker

Kinesiology Publications

BACKGROUND AND PURPOSE: Cerebrovascular autoregulation has been described with a phase lead of cerebral blood flow preceding changes in cerebral perfusion pressure (CPP), but there has been less focus on the effect of CPP on cerebral vascular resistance. We investigated these relations during spontaneous fluctuations (control) and repeated head-up tilt.

METHODS: Eight healthy adults were studied in supine rest and repeated tilt with 10-second supine, 10 seconds at 45 degrees head-up tilt for a total of 12 cycles. Cerebral blood flow was estimated from mean flow velocity (MFV) by transcranial Doppler ultrasound, CPP was estimated from corrected finger pressure (CPP(F)), …

Mri Measures Of Middle Cerebral Artery Diameter In Conscious Humans During Simulated Orthostasis., J M Serrador, P A Picot, B K Rutt, J K Shoemaker, R L Bondar

Kinesiology Publications

BACKGROUND AND PURPOSE: The relationship between middle cerebral artery (MCA) flow velocity (CFV) and cerebral blood flow (CBF) is uncertain because of unknown vessel diameter response to physiological stimuli. The purpose of this study was to directly examine the effect of a simulated orthostatic stress (lower body negative pressure [LBNP]) as well as increased or decreased end-tidal carbon dioxide partial pressure (P(ET)CO(2)) on MCA diameter and CFV.

METHODS: Twelve subjects participated in a CO(2) manipulation protocol and/or an LBNP protocol. In the CO(2) manipulation protocol, subjects breathed room air (normocapnia) or 6% inspired CO(2) (hypercapnia), or they hyperventilated to approximately …

Faster Femoral Artery Blood Velocity Kinetics At The Onset Of Exercise Following Short-Term Training., J K Shoemaker, S M Phillips, H J Green, R L Hughson

Kinesiology Publications

OBJECTIVE: The hypothesis that the adaptation to endurance exercise training included a faster increase in blood flow at the onset of exercise was tested in 12 healthy young men who endurance-trained (ET) 2 h/day, for 10 days at 65% VO2 peak on a cycle ergometer, and in 11 non-training control (C) subjects.

METHODS: Blood flow was estimated from changes in femoral artery mean blood velocity (MBV) by pulsed Doppler. Beat-by-beat changes in cardiac output (CO) and mean arterial pressure (MAP) were obtained by impedance cardiography and a Finapres finger cuff, respectively. MBV, MAP and CO were measured at rest and …