Chronic fatigue syndrome: Abnormally fast muscle fiber conduction in the membranes of motor units at low static force load

E. G. Klaver-Krol*, H. J. Hermens, R. C. Vermeulen, M. M. Klaver, H. Luyten, N. R. Henriquez, M. J. Zwarts

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

6 Citations (Scopus)
174 Downloads (Pure)


Objective: Chronic fatigue syndrome (CFS) and fibromyalgia (FM) are disorders of unknown etiology and unclear pathophysiology, with overlapping symptoms of – especially muscular –fatigue and pain. Studies have shown increased muscle fiber conduction velocity (CV) in the non-painful muscles of FM patients. We investigated whether CFS patients also show CV abnormalities. Methods: Females with CFS (n = 25), with FM (n = 22), and healthy controls (n = 21) underwent surface electromyography of the biceps brachii, loaded up to 20% of maximum strength, during short static contractions. The mean CV and motor unit potential (MUP) velocities with their statistical distribution were measured. Results: The CV changes with force differed between CFS-group and both FM-group and controls (P = 0.01). The CV of the CFS-group increased excessively with force (P < 0.001), whereas that of the controls increased only slightly and non-significantly, and that of the FM-group did not increase at all. In the CFS-group, the number of MUPs conveying very high conduction velocities increased abundantly with force and the MUPs narrowed. Conclusion: Our results suggest disturbed muscle membrane function in CFS patients, in their motor units involved in low force generation. Central neural deregulation may contribute to this disturbance. Significance: These findings help to detangle the underlying mechanisms of CFS.

Original languageEnglish
Pages (from-to)967-974
Number of pages8
JournalClinical neurophysiology
Issue number4
Early online date29 Jan 2021
Publication statusPublished - Apr 2021


  • Chronic fatigue syndrome
  • Force generation
  • Muscle fiber conduction velocity
  • Muscle membrane dysfunction
  • Surface electromyography


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