| The effect of higher ATP cost of contraction on the metabolic response to graded exercise in patients with chronic obstructive pulmonary disease. | |
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MedLine Citation:
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PMID: 22174392 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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To better understand the metabolic implications of a higher ATP cost of contraction in chronic obstructive pulmonary disease (COPD), we used (31)P-magnetic resonance spectroscopy ((31)P-MRS) to examine muscle energetic and pH in response to graded exercise. Specifically, in 6 patients and 6 well-matched healthy controls, we determined the intracellular threshold for pH (T(pH)) and inorganic phosphate to phosphocreatine ratio (T(Pi/PCr)) during progressive dynamic plantar flexion exercise with work rate expressed as both absolute and relative intensity. Patients with COPD displayed a lower peak power output (WRmax) compared to controls (controls: 25±4, COPD: 15±5 W, P=0.01) while end-exercise pH (controls: 6.79±0.15, COPD: 6.76±0.21, P=0.87) and PCr consumption (controls: 82 ± 10%, COPD: 70±18%, P=0.26) were similar between groups. Both T(pH) and T(Pi/PCr) occurred at a significantly lower absolute work rate in patients with COPD compared to controls (controls: 14.7±2.4 W for T(pH) and 15.3±2.4 W for T(Pi/PCr); COPD: 9.7±4.5 W for T(pH) and 10.0±4.6 W for T(Pi/PCr), P<0.05), but these thresholds occurred at the same percentage of WRmax (controls: 63 ± 11% WRmax for T(pH) and 67 ± 18% WRmax for T(Pi/PCr); COPD: 59 ± 9% WRmax for T(pH) and 61 ± 12% WRmax for T(Pi/PCr), P > 0.05). Indices of mitochondrial function, the PCr recovery time constant (controls: 42 ± 7s, COPD: 45 ± 11s, P = 0.66) and the PCr resynthesis rate (controls: 105 ± 21%.min(-1), COPD: 91 ± 31%.min(-1), P = 0.43) were similar between groups. In combination, these results reveal that when energy demand is normalized to WRmax, as a consequence of higher ATP cost of contraction, patients with COPD display the same metabolic pattern as healthy subjects, suggesting that skeletal muscle energy production is well preserved in these patients. |
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Authors:
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Gwenael Layec; Luke J Haseler; Russell S Richardson |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-12-15 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: - ISSN: 1522-1601 ISO Abbreviation: - Publication Date: 2011 Dec |
Date Detail:
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Created Date: 2011-12-16 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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1University of Utah. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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