title: Corticomotor excitability and perception of effort during sustained exercise in the chronic fatigue syndrome.
abstract: 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.
  
  
  CONCLUSIONS
  The findings are in keeping with an exercise-related diminution in central motor drive in association with an increased perception of effort in CFS.
authors.affiliation: Australian Neuromuscular Research Institute, QE II Medical Centre, Nedlands, WA, Australia. psacco@cyllene.uwa.edu.au
authors.forename: P
authors.initials: P
authors.lastname: Sacco
authors.forename: P A
authors.initials: PA
authors.lastname: Hope
authors.forename: G W
authors.initials: GW
authors.lastname: Thickbroom
authors.forename: M L
authors.initials: ML
authors.lastname: Byrnes
authors.forename: F L
authors.initials: FL
authors.lastname: Mastaglia
mesh_terms: D000328:Adult; D004550:Elbow / Q000294:innervation / Q000503:physiopathology; D004574:Electromagnetic Fields; D004576:Electromyography; D004734:Energy Metabolism / Q000502:physiology*; D019054:Evoked Potentials, Motor / Q000502:physiology; D015673:Fatigue Syndrome, Chronic / Q000503:physiopathology* / Q000523:psychology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D010465:Perception / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology