Document Detail

Muscle metabolism and acid-base status during exercise in forearm work-related myalgia measured with 31P-MRS.
MedLine Citation:
PMID:  19112160     Owner:  NLM     Status:  MEDLINE    
In this study, we examined muscle metabolic and acid-base status during incremental wrist extension exercise in the forearm of individuals with work-related myalgia (WRM). Eighteen women employed in full-time occupations involving repetitive forearm labor were recruited in this cross-sectional study. Nine of these women were diagnosed with WRM, while the other nine had no previous WRM history and were used as age-matched controls (Con). Phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) was used to noninvasively monitor the intracellular concentrations of phosphocreatine ([PCr]) and inorganic phosphate ([P(i)]) as well as intracellular pH (pH(i)) status during exercise in WRM and Con. We observed a 38% decreased work capacity in WRM compared with Con [0.18 W (SD 0.03) vs. 0.28 W (SD 0.10); P = 0.007]. Piecewise linear regression of the incremental exercise data revealed that the onset of a faster decrease in pH(i) (i.e., the pH threshold, pHT) and the onset of a faster increase in log([P(i)]/[PCr]) (i.e., the phosphorylation threshold, PT) occurred at a 14% relatively lower power output in WRM [pHT: 45.2% (SD 5.3) vs. 59.0% (SD 4.6), P < 0.001; PT: 44.8% (SD 4.3) vs. 57.8% (SD 3.1), P < 0.001; % of peak power output, Con vs. WRM, respectively]. Monoexponential modeling of the kinetics of [PCr] and pH(i) recovery following exercise demonstrated a slower (P = 0.005) time constant (tau) for [PCr] in WRM [113 s (SD 25)] vs. Con [77 s (SD 23)] and a slower (P = 0.007) tau for pH(i) in WRM [370 s (SD 178)] vs. Con [179 s (SD 52)]. In conclusion, our results suggest that WRM is associated with an increased reliance on nonoxidative metabolism. Possible mechanisms include a reduction in local muscle blood flow and perfusion, an increased ATP cost of force production, or both.
Graydon H Raymer; Howard J Green; Don A Ranney; Greg D Marsh; R Terry Thompson
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-12-26
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  106     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2009 Apr 
Date Detail:
Created Date:  2009-04-01     Completed Date:  2009-05-29     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:  1198-206     Citation Subset:  IM    
School of Physical and Health Education, Nipissing University, North Bay, ON, Canada.
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MeSH Terms
Acid-Base Equilibrium / physiology*
Cross-Sectional Studies
Exercise / physiology*
Exercise Tolerance / physiology
Forearm / physiology*
Hydrogen-Ion Concentration
Magnetic Resonance Imaging
Magnetic Resonance Spectroscopy
Middle Aged
Muscle Fatigue / physiology
Muscle Strength / physiology
Muscle, Skeletal / anatomy & histology,  metabolism*
Pain / etiology,  metabolism*,  physiopathology
Phosphates / metabolism
Phosphocreatine / metabolism
Reg. No./Substance:
0/Phosphates; 67-07-2/Phosphocreatine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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