| Alterations in autonomic function and cerebral hemodynamics to orthostatic challenge following a mountain marathon. | |
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MedLine Citation:
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PMID: 17379746 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We examined potential mechanisms (autonomic function, hypotension, and cerebral hypoperfusion) responsible for orthostatic intolerance following prolonged exercise. Autonomic function and cerebral hemodynamics were monitored in seven athletes pre-, post- (<4 h), and 48 h following a mountain marathon [42.2 km; cumulative gain approximately 1,000 m; approximately 15 degrees C; completion time, 261 +/- 27 (SD) min]. In each condition, middle cerebral artery blood velocity (MCAv), blood pressure (BP), heart rate (HR), and cardiac output (Modelflow) were measured continuously before and during a 6-min stand. Measurements of HR and BP variability and time-domain analysis were used as an index of sympathovagal balance and baroreflex sensitivity (BRS). Cerebral autoregulation was assessed using transfer-function gain and phase shift in BP and MCAv. Hypotension was evident following the marathon during supine rest and on standing despite increased sympathetic and reduced parasympathetic control, and elevations in HR and cardiac output. On standing, following the marathon, there was less elevation in normalized low-frequency HR variability (P < 0.05), indicating attenuated sympathetic activation. MCAv was maintained while supine but reduced during orthostasis postmarathon [-10.4 +/- 9.8% pre- vs. -15.4 +/- 9.9% postmarathon (%change from supine); P < 0.05]; such reductions were related to an attenuation in BRS (r = 0.81; P < 0.05). Cerebral autoregulation was unchanged following the marathon. These findings indicate that following prolonged exercise, hypotension and postural reductions in autonomic function or baroreflex control, or both, rather than a compromise in cerebral autoregulation, may place the brain at risk of hypoperfusion. Such changes may be critical factors in collapse following prolonged exercise. |
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Authors:
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Carissa Murrell; Luke Wilson; James D Cotter; Samuel Lucas; Shigehiko Ogoh; Keith George; Philip N Ainslie |
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Publication Detail:
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Type: Comparative Study; Journal Article Date: 2007-03-22 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 103 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2007 Jul |
Date Detail:
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Created Date: 2007-07-06 Completed Date: 2007-09-18 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: United States |
Other Details:
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Languages: eng Pagination: 88-96 Citation Subset: IM |
Affiliation:
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Department of Physiology, University of Otago, Dunedin, New Zealand. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adult Autonomic Nervous System / physiopathology* Baroreflex* Blood Flow Velocity Blood Pressure Cardiac Output Cerebrovascular Circulation* Dizziness / etiology*, physiopathology Female Heart Rate Humans Hypotension, Orthostatic / complications, physiopathology* Male Middle Cerebral Artery / physiopathology* Physical Endurance* Physical Exertion* Posture Supine Position Time Factors |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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