title: Pain inhibition and postexertional malaise in myalgic encephalomyelitis/chronic fatigue syndrome: an experimental study.
abstract: OBJECTIVE
  To examine the efficacy of the pain inhibitory systems in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) during two different types of exercise and to examine whether the (mal)functioning of pain inhibitory systems is associated with symptom increases following exercise.
  
  
  METHODS
  A controlled experimental study.
  
  
  METHODS
  Twenty-two women with ME/CFS and 22 healthy sedentary controls were studied at the Department of Human Physiology, Vrije Universiteit Brussel.
  
  
  METHODS
  All subjects performed a submaximal exercise test and a self-paced, physiologically limited exercise test on a cycle ergometer. The exercise tests were undertaken with continuous cardiorespiratory monitoring. Before and after the exercise bouts, subjects filled out questionnaires to assess health status, and underwent pressure pain threshold measurements. Throughout the study, subjects' activity levels were assessed using accelerometry.
  
  
  RESULTS
  In patients with ME/CFS, pain thresholds decreased following both types of exercise, whereas they increased in healthy subjects. This was accompanied by a worsening of the ME/CFS symptom complex post-exercise. Decreased pressure thresholds during submaximal exercise were associated with postexertional fatigue in the ME/CFS group (r = 0.454; P = 0.034).
  
  
  CONCLUSIONS
  These observations indicate the presence of abnormal central pain processing during exercise in patients with ME/CFS and demonstrate that both submaximal exercise and self-paced, physiologically limited exercise trigger postexertional malaise in these patients. Further study is required to identify specific modes and intensity of exercise that can be performed in people with ME/CFS without exacerbating symptoms.
authors.affiliation: Department of Human Physiology, Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Van Oosterwijck
authors.forename: J
authors.initials: J
authors.lastname: Nijs
authors.forename: M
authors.initials: M
authors.lastname: Meeus
authors.forename: I
authors.initials: I
authors.lastname: Lefever
authors.forename: L
authors.initials: L
authors.lastname: Huybrechts
authors.forename: L
authors.initials: L
authors.lastname: Lambrecht
authors.forename: L
authors.initials: L
authors.lastname: Paul
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance / Q000502:physiology; D015673:Fatigue Syndrome, Chronic / Q000503:physiopathology / Q000523:psychology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D017288:Pain Threshold / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods; D055815:Young Adult