quote: Diminished central activation during maximal voluntary contraction inchronic fatigue syndrome.Journal: Clin Neurophysiol. 2004 Nov;115(11):2518-24.Authors: Schillings ML, Kalkman JS, van der Werf SP, van Engelen BG,Bleijenberg G, Zwarts MJ.Affiliation: Department of Clinical Neurophysiology, University MedicalCentre Nijmegen, Internal postal code 314, P.O. Box 9101, 6500 HBNijmegen, Netherlands.NLM Citation: PMID: 15465441Objective: We have investigated whether central activation failure (CAF)is increased during local muscle fatigue in chronic fatigue syndrome(CFS).Methods: Fourteen female CFS patients and 14 age-matched healthy femalecontrols made a 2 min sustained maximal voluntary contraction (MVC) ofthe biceps brachii muscle. Before, during, and after sustained MVC,electrical endplate stimulation was applied. Force and 5 channel surfaceEMG (sEMG) were registered.Results: Although force responses upon stimulation during rest did notdiffer between patients and controls, MVC was significantly lower inpatients. Already at the beginning of sustained MVC, CFS patients showedsignificantly larger CAF than controls (36.5+/-17.0% and 12.9+/-13.3%,respectively). For all individual patients mean CAF over the first 45 swas higher than 30%, while it was below 30% for all controls. Lessperipheral fatigue in patients was demonstrated by the changes in musclefibre conduction velocity and the differences between force responsesbefore and after contraction.Conclusions: Central activation is diminished in CFS patients. Possiblecauses include changed perception, impaired concentration, reduced effortand physiologically defined changes, e.g. in the corticospinalexcitability or the concentration of neurotransmitters. As a consequence,demands on the muscle are lower, resulting in less peripheral fatigue.Significance: CFS patients show reduced central activation during MVC.The underlying pathophysiological processes remain still to bedetermined.