pH abnormalities in the muscle during exercise and Work-Related Pain

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Full title: Work-Related Pain in Extrinsic Finger Extensor Musculature of Instrumentalists Is Associated with Intracellular pH Compartmentation during Exercise

Work-Related Pain in Extrinsic Finger Extensor Musculature of Instrumentalists Is Associated with Intracellular pH Compartmentation during Exercise.

PLoS One. 2010 Feb 9;5(2):e9091.

Moreno-Torres A, Rosset-Llobet J, Pujol J, Fbregas S, Gonzalez-de-Suso JM.

Research Department, Centre Diagnstic Pedralbes, Esplugues de Llobregat, Spain.

BACKGROUND: Although non-specific pain in the upper limb muscles of workers engaged in mild repetitive tasks is a common occupational health problem, much is unknown about the associated structural and biochemical changes. In this study, we compared the muscle energy metabolism of the extrinsic finger extensor musculature in instrumentalists suffering from work-related pain with that of healthy control instrumentalists using non-invasive phosphorus magnetic resonance spectroscopy ((31)P-MRS). We hypothesize that the affected muscles will show alterations related with an impaired energy metabolism.

METHODOLOGY/PRINCIPAL FINDINGS: We studied 19 volunteer instrumentalists (11 subjects with work-related pain affecting the extrinsic finger extensor musculature and 8 healthy controls). We used (31)P-MRS to find deviations from the expected metabolic response to exercise in phosphocreatine (PCr), inorganic phosphate (Pi), Pi/PCr ratio and intracellular pH kinetics. We observed a reduced finger extensor exercise tolerance in instrumentalists with myalgia, an intracellular pH compartmentation in the form of neutral and acid compartments, as detected by Pi peak splitting in (31)P-MRS spectra, predominantly in myalgic muscles, and a strong association of this pattern with the condition.

CONCLUSIONS/SIGNIFICANCE: Work-related pain in the finger extrinsic extensor muscles is associated with intracellular pH compartmentation during exercise, non-invasively detectable by (31)P-MRS and consistent with the simultaneous energy production by oxidative metabolism and glycolysis. We speculate that a deficit in energy production by oxidative pathways may exist in the affected muscles. Two possible explanations for this would be the partial and/or local reduction of blood supply and the reduction of the muscle oxidative capacity itself.

PMID: 20161738 [PubMed - in process]

Full text is available for free at:
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009091

I wonder if there is any similarity with:

Abnormalities in pH Handling by Peripheral Muscle and Potential Regulation by the Autonomic Nervous System in Chronic Fatigue Syndrome

David EJ Jones MD PhD 1 , Kieren G Hollingsworth MD PhD 2 , Roy Taylor MD 2 , Andrew M Blamire PhD 2 , Julia L Newton MD PhD 1,3

Institute of Cellular Medicine1 , Newcastle Magnetic Resonance Centre2
3 Institute for Ageing and Health, Newcastle University, UK
d.e.j.jones@ncl.ac.uk
Correspondence: Professor Julia L Newton
Institute for Ageing and Health
Medical School
Framlington Place
Newcastle-upon-Tyne
NE2 4HH
UK
Tel: 0191 2824128
Email: julia.newton@nuth.nhs.uk

Chronic fatigue syndrome muscle bioenergetics autonomic dysfunction magnetic resonance spectroscopy

ABSTRACT

Objectives: To examine muscle acid handling following exercise in Chronic Fatigue Syndrome (CFS/ME) and the relationship with autonomic dysfunction.

Design: Observational study

Setting: Regional Fatigue Service.

Subjects & Interventions: CFS/ME (n=16) and age and sex matched normal controls (n=8) underwent phosphorus magnetic resonance spectroscopy (MRS) to evaluate pH handling during exercise. Subjects performed plantar flexion at fixed 35% load Maximum Voluntary Contraction. Heart rate variability was performed during 10 minutes supine rest using digital photophlethysmography as a measure of autonomic function.

Results: Compared to normal controls, the CFS/ME group had significant suppression of proton efflux both immediately post-exercise (CFS: 1.1 0.5 mM/min v Normal: 3.6 1.5 mM/min, p<0.001) and maximally (CFS: 2.7 3.4 mM/min v Control: 3.8 1.6 mM/min, p<0.05). Furthermore, the time taken to reach maximum proton efflux was significantly prolonged in patients (CFS: 25.6 36.1s v Normal: 3.8 5.2 s, p<0.05). In controls the rate of maximum proton efflux showed a strong inverse correlation with nadir muscle pH following exercise (r2=0.6; p<0.01). In CFS patients, in contrast, this significant normal relationship was lost (r2=0.003; p=ns). In normal individuals the maximum proton efflux following exercise were closely correlated with total heart rate variability (r2=0.7;p=0.007) this relationship was lost in CFS/ME patients (r2<0.001;p=ns).

Conclusion: Patients with CFS/ME have abnormalities in recovery of intramuscular pH following standardised exercise degree of which is related to autonomic dysfunction. This study identifies a novel biological abnormality in patients with CFS/ME which is potentially open to modification.

Full text available (not for free) at:
http://www3.interscience.wiley.com/journal/122564291/abstract?CRETRY=1&SRETRY=0