Document Detail

Cardiovascular and thermal responses to repeated head-up tilts following exercise-induced heat stress.
MedLine Citation:
PMID:  20597243     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: We evaluated the acute cardiovascular and thermoregulatory responses to repeated 70 degrees head-up tilts (HUT) performed following exercise-induced hyperthermia. METHODS: Eight male subjects underwent intermittent episodes of 70 degrees HUT in either a non-exercise/ non-heat stress state (NH) or an exercise-induced hyperthermic state (EIH). Subjects remained supine for 30 min in a thermoneutral environment (22 degrees C) and were subsequently exposed to three successive 6-min 70 degrees head-up tilts (HUT1, HUT2, HUT3), each separated by 10 min of supine resting. During EIH, subjects were rendered hyperthermic by exercise in the heat (core temperature of approximately 40.0 degrees C) and were then transferred to an ambient temperature of 22 degrees C. We evaluated the relative change in hemodynamic and thermal responses from the last minute in the supine position preceding the HUT to the final minute in HUT. RESULTS: While we measured a difference in the relative change in heart rate between conditions for all HUTs, no differences were observed in mean arterial pressure (MAP), total peripheral resistance, or cardiac output. A reduced change in baroreceptor sensitivity was measured in EIH for HUT1 only (-2 +/- 1 ms x mmHg(-1) following EIH compared to -13 +/- 3 ms x mmHg(-1) during NH). A significant transient reduction in cutaneous vascular conductance (CVC) occurred during HUT1 and HUT2 following EIH (-20 +/- 5% CVCmax and -9 +/- 3 %CVCmax, respectively), despite significant elevations in core temperature above resting levels (i.e., 1.4 degrees C and 0.9 degrees C for HUT1 and HUT2). CONCLUSION: We conclude that the maintenance of MAP following exercise in the heat is mitigated by reductions in skin perfusion despite significant elevations in core temperature.
Rachel G Armstrong; Andrew J Seely; Donald Kilby; W Shane Journeay; Glen P Kenny
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Aviation, space, and environmental medicine     Volume:  81     ISSN:  0095-6562     ISO Abbreviation:  Aviat Space Environ Med     Publication Date:  2010 Jul 
Date Detail:
Created Date:  2010-07-05     Completed Date:  2010-07-26     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7501714     Medline TA:  Aviat Space Environ Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  646-53     Citation Subset:  IM; S    
Human and Environmental Physiology Research Unit, Faculty of Health Sciences, University of Ottawa, Ottawa, Ontario, Canada.
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MeSH Terms
Baroreflex / physiology
Blood Pressure / physiology*
Body Temperature Regulation / physiology*
Cardiac Output
Exercise / physiology
Heart Rate / physiology
Heat Stress Disorders / etiology,  physiopathology*
Posture / physiology*
Regional Blood Flow
Skin / blood supply
Young Adult

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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