[Note: according to University of Mississippi Medical Center, the cellular acidity/alkalinity status (pH) of resting skeletal muscle is typically 7.15. It falls - becomes more acid - during exercise in proportion to the intensity of the exercise, as concentrations of pCO2 and lactic acid build up. Exercising to exhaustion normally brings pH to about 6.60. The acidity appears to be an important contributor to perceived/real exhaustion. Measured proton efflux rate rises as pH declines/acidity increases.]
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.
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 ± 36.1 s 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 [lowest] 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).
• Patients with CFS/ME have abnormalities in recovery of intramuscular pH following standardized 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.
Source: Journal of Internal Medicine, online Aug 20, 2009. DOI: 10.1111/j.1365-2796.2009.02160.x Jones DEJ, Hollingsworth KG, Taylor R, Blamire AM, Newton JL. Institute of Cellular Medicine, Newcastle Magnetic Resonance Centre, Institute for Ageing and Health, Newcastle University, Newcastle-upon-Tyne, UK. [E-mail: firstname.lastname@example.org]