| Supine cycling plus volume loading prevent cardiovascular deconditioning during bed rest. | |
| | |
MedLine Citation:
|
PMID: 20223994 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
There are two possible mechanisms contributing to the excessive fall of stroke volume (and its contribution to orthostatic intolerance) in the upright position after bed rest or spaceflight: reduced cardiac filling due to hypovolemia and/or a less distensible heart due to cardiac atrophy. We hypothesized that preservation of cardiac mechanical function by exercise training, plus normalization of cardiac filling with volume infusion, would prevent orthostatic intolerance after bed rest. Eighteen men and three women were assigned to 1) exercise countermeasure (n=14) and 2) no exercise countermeasure (n=7) groups during bed rest. Bed rest occurred in the 6 degrees head-down tilt position for 18 days. The exercise regimen was prescribed to compensate for the estimated cardiac work reduction between bed rest and ambulatory periods. At the end of bed rest, the subjects were further divided into two additional groups for post-bed rest testing: 1) volume loading with intravenous dextran to normalize cardiac filling pressure and 2) no volume loading. Dextran infusion was given to half of the exercise group and all of the sedentary group after bed rest, leading ultimately to three groups: 1) exercise plus volume infusion; 2) exercise alone; and 3) volume infusion alone. Exercise training alone preserved left ventricular mass and distensibility as well as upright exercise capacity, but lower body negative pressure (LBNP) tolerance was still depressed. LBNP tolerance was maintained only when exercise training was accompanied by dextran infusion. Dextran infusion alone following bed rest without exercise maintained neither orthostatic tolerance nor upright exercise capacity. We conclude that daily supine cycle exercise sufficient to prevent cardiac atrophy can prevent orthostatic intolerance after bed rest only when combined with plasma volume restoration. This maintenance of orthostatic tolerance was achieved by neither exercise nor dextran infusion alone. Cardiac atrophy and hypovolemia are likely to contribute independently to orthostatic intolerance after bed rest. |
| | |
Authors:
|
Shigeki Shibata; Merja Perhonen; Benjamin D Levine |
Related Documents
:
|
1275824 - Exercise cardiac output following skylab missions: the second manned skylab mission. 22681184 - New insights into fish swimming: a proteomic and isotopic approach in gilthead sea bream. 20643664 - The impact of acute reduction of continuous-flow left ventricular assist device support... 16214454 - Comparison and relation of indirect and direct dynamic indexes of cardiac pumping capac... 17990214 - Bright light and thermoregulatory responses to exercise. 23624624 - Immediate effects of a single exercise bout on protein o-glcnacylation and chromatin re... |
Publication Detail:
|
Type: Journal Article; Randomized Controlled Trial; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S. Date: 2010-03-11 |
Journal Detail:
|
Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 108 ISSN: 1522-1601 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2010 May |
Date Detail:
|
Created Date: 2010-05-05 Completed Date: 2010-08-12 Revised Date: - |
Medline Journal Info:
|
Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: United States |
Other Details:
|
Languages: eng Pagination: 1177-86 Citation Subset: IM |
Affiliation:
|
Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, and University of Texas Southwestern Medical Center at Dallas, 7232 Greenville Ave., Suite 435, Dallas, TX 75231, USA. |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Atrophy Bed Rest / adverse effects* Bicycling* Blood Volume Cardiovascular Deconditioning* Combined Modality Therapy Compliance Dextrans / administration & dosage* Exercise Test Exercise Tolerance Female Head-Down Tilt / adverse effects* Hemodynamics Humans Hypovolemia / etiology, physiopathology, prevention & control Infusions, Intravenous Lower Body Negative Pressure Male Myocardium / pathology Orthostatic Intolerance / etiology, pathology, physiopathology, prevention & control* Plasma Substitutes / administration & dosage* Supine Position* Time Factors Treatment Outcome Ventricular Function, Left Ventricular Pressure |
| Grant Support | |
ID/Acronym/Agency:
|
RR-00633/RR/NCRR NIH HHS |
| Chemical | |
Reg. No./Substance:
|
0/Plasma Substitutes; 9004-54-0/Dextrans |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: Hypoxia-induced vasodilation and effects of regional phentolamine in awake patients with sleep apnea...
Next Document: Deficits in lung alveolarization and function after systemic maternal inflammation and neonatal hype...