Document Detail

Lower body negative pressure exercise plus brief postexercise lower body negative pressure improve post-bed rest orthostatic tolerance.
MedLine Citation:
PMID:  17947505     Owner:  NLM     Status:  MEDLINE    
Orthostatic intolerance follows actual weightlessness and weightlessness simulated by bed rest. Orthostasis immediately after acute exercise imposes greater cardiovascular stress than orthostasis without prior exercise. We hypothesized that 5 min/day of simulated orthostasis [supine lower body negative pressure (LBNP)] immediately following LBNP exercise maintains orthostatic tolerance during bed rest. Identical twins (14 women, 16 men) underwent 30 days of 6 degrees head-down tilt bed rest. One of each pair was randomly selected as a control, and their sibling performed 40 min/day of treadmill exercise while supine in 53 mmHg (SD 4) [7.05 kPa (SD 0.50)] LBNP. LBNP continued for 5 min after exercise stopped. Head-up tilt at 60 degrees plus graded LBNP assessed orthostatic tolerance before and after bed rest. Hemodynamic measurements accompanied these tests. Bed rest decreased orthostatic tolerance time to a greater extent in control [34% (SD 10)] than in countermeasure subjects [13% (SD 20); P < 0.004]. Controls exhibited cardiac stroke volume reduction and relative cardioacceleration typically seen after bed rest, yet no such changes occurred in the countermeasure group. These findings demonstrate that 40 min/day of supine LBNP treadmill exercise followed immediately by 5 min of resting LBNP attenuates, but does not fully prevent, the orthostatic intolerance associated with 30 days of bed rest. We speculate that longer postexercise LBNP may improve results. Together with our earlier related studies, these ground-based results support spaceflight evaluation of postexercise orthostatic stress as a time-efficient countermeasure against postflight orthostatic intolerance.
Donald E Watenpaugh; Deborah D O'Leary; Suzanne M Schneider; Stuart M C Lee; Brandon R Macias; Kunihiko Tanaka; Richard L Hughson; Alan R Hargens
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Publication Detail:
Type:  Journal Article; Randomized Controlled Trial; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Twin Study     Date:  2007-10-18
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  103     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2007 Dec 
Date Detail:
Created Date:  2007-12-06     Completed Date:  2008-02-21     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1964-72     Citation Subset:  IM    
Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX, USA.
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MeSH Terms
Bed Rest / adverse effects*
Blood Pressure
Cardiac Output
Dizziness / etiology,  physiopathology,  prevention & control*
Head-Down Tilt
Heart Rate
Lower Body Negative Pressure*
Research Design
Space Flight*
Stroke Volume
Supine Position
Time Factors
Twins, Monozygotic
Vascular Resistance
Weightlessness Countermeasures*
Weightlessness Simulation*
Grant Support

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

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