| Chronic intermittent hypoxia and incremental cycling exercise independently depress muscle in vitro maximal Na+-K+-ATPase activity in well-trained athletes. | |
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MedLine Citation:
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PMID: 15033968 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Athletes commonly attempt to enhance performance by training in normoxia but sleeping in hypoxia [live high and train low (LHTL)]. However, chronic hypoxia reduces muscle Na(+)-K(+)-ATPase content, whereas fatiguing contractions reduce Na(+)-K(+)-ATPase activity, which each may impair performance. We examined whether LHTL and intense exercise would decrease muscle Na(+)-K(+)-ATPase activity and whether these effects would be additive and sufficient to impair performance or plasma K(+) regulation. Thirteen subjects were randomly assigned to two fitness-matched groups, LHTL (n = 6) or control (Con, n = 7). LHTL slept at simulated moderate altitude (3,000 m, inspired O(2) fraction = 15.48%) for 23 nights and lived and trained by day under normoxic conditions in Canberra (altitude approximately 600 m). Con lived, trained, and slept in normoxia. A standardized incremental exercise test was conducted before and after LHTL. A vastus lateralis muscle biopsy was taken at rest and after exercise, before and after LHTL or Con, and analyzed for maximal Na(+)-K(+)-ATPase activity [K(+)-stimulated 3-O-methylfluorescein phosphatase (3-O-MFPase)] and Na(+)-K(+)-ATPase content ([(3)H]ouabain binding sites). 3-O-MFPase activity was decreased by -2.9 +/- 2.6% in LHTL (P < 0.05) and was depressed immediately after exercise (P < 0.05) similarly in Con and LHTL (-13.0 +/- 3.2 and -11.8 +/- 1.5%, respectively). Plasma K(+) concentration during exercise was unchanged by LHTL; [(3)H]ouabain binding was unchanged with LHTL or exercise. Peak oxygen consumption was reduced in LHTL (P < 0.05) but not in Con, whereas exercise work was unchanged in either group. Thus LHTL had a minor effect on, and incremental exercise reduced, Na(+)-K(+)-ATPase activity. However, the small LHTL-induced depression of 3-O-MFPase activity was insufficient to adversely affect either K(+) regulation or total work performed. |
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Authors:
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R J Aughey; C J Gore; A G Hahn; A P Garnham; S A Clark; A C Petersen; A D Roberts; M J McKenna |
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Publication Detail:
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Type: Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't Date: 2004-03-19 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 98 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2005 Jan |
Date Detail:
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Created Date: 2004-12-13 Completed Date: 2005-05-11 Revised Date: 2007-11-15 |
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: 186-92 Citation Subset: IM |
Affiliation:
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School of Human Movement, Recreation and Performance (FO22) Victoria University of Technology, P.O. Box 14428, MCMC, Melbourne, Victoria 8001, Australia. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adult Altitude* Anoxia / physiopathology* Bicycling* Chronic Disease Enzyme Activation Exercise* Gene Expression Regulation Humans Male Muscle, Skeletal / physiopathology* Physical Endurance* Sodium-Potassium-Exchanging ATPase / metabolism* Sports Time Factors |
| Chemical | |
Reg. No./Substance:
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EC 3.6.3.9/Sodium-Potassium-Exchanging ATPase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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