Document Detail

The effect of higher ATP cost of contraction on the metabolic response to graded exercise in patients with chronic obstructive pulmonary disease.
MedLine Citation:
PMID:  22174392     Owner:  NLM     Status:  MEDLINE    
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 energetics and pH in response to graded exercise. Specifically, in six patients and six 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 with controls (controls 25 ± 4 W, 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 with 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). Indexes of mitochondrial function, the PCr recovery time constant (controls 42 ± 7 s, COPD 45 ± 11 s, P = 0.66) and the PCr resynthesis rate (controls 105 ± 21%/min, COPD 91 ± 31%/min, 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.
Gwenael Layec; Luke J Haseler; Russell S Richardson
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2011-12-15
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  112     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2012 Mar 
Date Detail:
Created Date:  2012-03-16     Completed Date:  2012-09-13     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:  1041-8     Citation Subset:  IM    
Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah, USA.
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MeSH Terms
Adenosine Triphosphate / metabolism*
Energy Metabolism / physiology
Exercise / physiology*
Hydrogen-Ion Concentration
Magnetic Resonance Spectroscopy / methods
Mitochondria / metabolism,  pathology
Muscle Contraction / physiology*
Muscle, Skeletal / metabolism
Phosphates / metabolism
Phosphocreatine / metabolism
Pulmonary Disease, Chronic Obstructive / metabolism*
Grant Support
Reg. No./Substance:
0/Phosphates; 56-65-5/Adenosine Triphosphate; 67-07-2/Phosphocreatine

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