Corticomotor excitability and perception of effort during sustained exercise in the chronic fatigue syndrome

Clin Neurophysiol. 1999 Nov;110(11):1883-91. doi: 10.1016/s1388-2457(99)00144-3.


Objective: We have investigated the possibility of a central basis for the complaints of fatigue and poor exercise tolerance in subjects with chronic fatigue syndrome (CFS).

Methods: Transcranial magnetic stimulation of the motor cortex was used to measure sequential changes in motor evoked potential (MEP) amplitude, post-excitatory silent period (SP) duration and twitch force of the biceps brachii muscle during a 20% maximum isometric elbow flexor contraction maintained to the point of exhaustion. Ten patients with post-infectious CFS and 10 age- and sex-matched control subjects were studied. Results were analysed using non-parametric repeated measures analysis of variance (Friedman's test) and Mann-Whitney U-tests for intra- and inter-group comparisons respectively.

Results: Mean endurance time for the CFS group was lower (13.1+/-3.2 min, mean +/- SEM) than controls (18.6+/-2.6 min, P < 0.05) and CFS subjects reported higher ratings of perceived exertion. During the exercise period MEP amplitude and SP duration increased in both groups but to a lesser extent in CFS subjects. Interpolated twitch force amplitude also increased during exercise, being more pronounced in CFS subjects.

Conclusion: The findings are in keeping with an exercise-related diminution in central motor drive in association with an increased perception of effort in CFS.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Elbow / innervation
  • Elbow / physiopathology
  • Electromagnetic Fields
  • Electromyography
  • Energy Metabolism / physiology*
  • Evoked Potentials, Motor / physiology
  • Fatigue Syndrome, Chronic / physiopathology*
  • Fatigue Syndrome, Chronic / psychology*
  • Female
  • Humans
  • Isometric Contraction / physiology
  • Male
  • Middle Aged
  • Motor Cortex / physiopathology*
  • Perception / physiology*
  • Physical Endurance / physiology