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Skin surface cooling improves orthostatic tolerance following prolonged head-down bed rest.
MedLine Citation:
PMID:  21454746     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Prolonged exposure to microgravity and its ground-based analog, head-down bed rest (HDBR), reduces orthostatic tolerance in humans. While skin surface cooling improves orthostatic tolerance, it remains unknown whether this could be an effective countermeasure to preserve post-HDBR orthostatic tolerance. We tested the hypothesis that skin surface cooling improves orthostatic tolerance after prolonged HDBR. Eight subjects (6 men and 2 women) participated in the investigation. Orthostatic tolerance was determined using a lower-body negative pressure (LBNP) tolerance test before HDBR during normothermic conditions and on day 16 or 18 of 6° HDBR during normothermic and skin surface cooling conditions (randomized order post-HDBR). The thermal conditions were achieved by perfusing water (normothermia ~34 °C and skin surface cooling ~12-15 °C) through a tube-lined suit worn by each subject. Tolerance tests were performed after ~30 min of the respective thermal stimulus. A cumulative stress index (CSI: mm Hg LBNP(.)min) was determined for each LBNP protocol by summing the product of the applied negative pressure and the duration of LBNP at each stage. HDBR reduced normothermic orthostatic tolerance as indexed by a reduction in the CSI from 1037±96 mm Hg(.)min to 574±63 mm Hg(.)min (P < 0.05). After HDBR, skin surface cooling increased orthostatic tolerance (797±77 mm Hg(.)min) compared to normothermia (P < 0.05). While the reduction in orthostatic tolerance following prolonged HDBR was not completely reversed by acute skin surface cooling, the identified improvements may serve as an important and effective countermeasure for individuals exposed to microgravity, as well as immobilized and bed-stricken individuals.
Authors:
David Melvin Keller; David A Low; Scott L Davis; Jeffrey L Hastings; Craig G Crandall
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-3-31
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  -     ISSN:  1522-1601     ISO Abbreviation:  -     Publication Date:  2011 Mar 
Date Detail:
Created Date:  2011-4-1     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
1University of Texas Arlington.
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