title: Unravelling the nature of postexertional malaise in myalgic encephalomyelitis/chronic fatigue syndrome: the role of elastase, complement C4a and interleukin-1beta.
abstract: OBJECTIVE
  Too vigorous exercise or activity increase frequently triggers postexertional malaise in people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a primary characteristic evident in up to 95% of people with ME/CFS. The present study aimed at examining whether two different types of exercise results in changes in health status, circulating elastase activity, interleukin (IL)-1beta and complement C4a levels.
  
  
  METHODS
  Comparative experimental design.
  
  
  METHODS
  University.
  
  
  METHODS
  Twenty-two women with ME/CFS and 22 healthy sedentary controls
  
  
  METHODS
  participants were subjected to a submaximal exercise (day 8) and a self-paced, physiologically limited exercise (day 16). Each bout of exercise was preceded and followed by blood sampling, actigraphy and assessment of their health status.
  
  
  RESULTS
  Both submaximal exercise and self-paced, physiologically limited exercise resulted in postexertional malaise in people with ME/CFS. However, neither exercise bout altered elastase activity, IL-1beta or complement C4a split product levels in people with ME/CFS or healthy sedentary control subjects (P > 0.05). Postexercise complement C4a level was identified as a clinically important biomarker for postexertional malaise in people with ME/CFS.
  
  
  CONCLUSIONS
  Submaximal exercise as well as self-paced, physiologically limited exercise triggers postexertional malaise in people with ME/CFS, but neither types of exercise alter acute circulating levels of IL-1beta, complement C4a split product or elastase activity. Further studying of immune alterations in relation to postexertional malaise in people with ME/CFS using multiple measurement points postexercise is required.
authors.affiliation: Department of Human Physiology, Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium. jo.nijs@vub.ac.be
authors.forename: J
authors.initials: J
authors.lastname: Nijs
authors.forename: J
authors.initials: J
authors.lastname: Van Oosterwijck
authors.forename: M
authors.initials: M
authors.lastname: Meeus
authors.forename: L
authors.initials: L
authors.lastname: Lambrecht
authors.forename: K
authors.initials: K
authors.lastname: Metzger
authors.forename: M
authors.initials: M
authors.lastname: Frémont
authors.forename: L
authors.initials: L
authors.lastname: Paul
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D015934:Complement C4a / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D005221:Fatigue / Q000378:metabolism*; D015673:Fatigue Syndrome, Chronic / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D006801:Humans; D053583:Interleukin-1beta / Q000097:blood*; D010196:Pancreatic Elastase / Q000097:blood*; D011795:Surveys and Questionnaires
chemical_list: D053583:Interleukin-1beta; D015934:Complement C4a; D010196:Pancreatic Elastase