title: Endogenous pain modulation in response to exercise in patients with rheumatoid arthritis, patients with chronic fatigue syndrome and comorbid fibromyalgia, and healthy controls: a double-blind randomized controlled trial.
abstract: OBJECTIVE
  Temporal summation (TS) of pain, conditioned pain modulation (CPM), and exercise-induced analgesia (EIA) are often investigated in chronic pain populations as an indicator for enhanced pain facilitation and impaired endogenous pain inhibition, respectively, but interactions are not yet clear both in healthy controls and in chronic pain patients. Therefore, the present double-blind randomized placebo-controlled study evaluates pains cores, TS, and CPM in response to exercise in healthy controls, patients with chronic fatigue syndrome and comorbid fibromyalgia (CFS/FM), and patients with rheumatoid arthritis (RA), both under placebo and paracetamol condition.
  
  
  METHODS
  Fifty-three female volunteers - of which 19 patients with CFS/FM, 16 patients with RA, and 18 healthy controls - underwent a submaximal exercise test on a bicycle ergometer on 2 different occasions (paracetamol vs. placebo), with an interval of 7 days. Before and after exercise, participants rated pain intensity during TS and CPM.
  
  
  RESULTS
  Patients with rheumatoid arthritis showed decreased TS after exercise, both after paracetamol and placebo (P < 0.05). In patients with CFS/FM, results were less univocal. A nonsignificant decrease in TS was only observed after taking paracetamol. CPM responses to exercise are inconclusive, but seem to worsen after exercise. No adverse effects were seen.
  
  
  CONCLUSIONS
  This study evaluates pain scores, TS, and CPM in response to submaximal exercise in 2 different chronic pain populations and healthy controls. In patients with RA, exercise had positive effects on TS, suggesting normal EIA. In patients with CFS/FM, these positive effects were only observed after paracetamol and results were inconsistent.
authors: Departments of Human Physiology and Rehabilitation Sciences, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium; Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium; Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium; "Pain in Motion" Research Group.
authors: Mira
authors: M
authors: Meeus
authors: Linda
authors: L
authors: Hermans
authors: Kelly
authors: K
authors: Ickmans
authors: Filip
authors: F
authors: Struyf
authors: Deborah
authors: D
authors: Van Cauwenbergh
authors: Laura
authors: L
authors: Bronckaerts
authors: Luc S
authors: LS
authors: De Clerck
authors: Greta
authors: G
authors: Moorken
authors: Guy
authors: G
authors: Hans
authors: Sofie
authors: S
authors: Grosemans
authors: Jo
authors: J
authors: Nijs
mesh_terms: D000082:Acetaminophen / Q000627:therapeutic use*; D000328:Adult; D000368:Aged; D000698:Analgesia; D018712:Analgesics, Non-Narcotic / Q000627:therapeutic use*; D001172:Arthritis, Rheumatoid / Q000628:therapy*; D059350:Chronic Pain; D015897:Comorbidity; D018592:Cross-Over Studies; D004311:Double-Blind Method; D015444:Exercise; D015673:Fatigue Syndrome, Chronic / Q000453:epidemiology / Q000628:therapy*; D005260:Female; D005356:Fibromyalgia / Q000453:epidemiology / Q000628:therapy*; D006801:Humans; D008875:Middle Aged; D059408:Pain Management; D059227:Postsynaptic Potential Summation; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D018712:Analgesics, Non-Narcotic; D000082:Acetaminophen
keywords: acetaminophen; chronic fatigue syndrome; conditioned pain modulation; exercise-induced analgesia; fibromyalgia; pain inhibition; randomized controlled trial; rheumatoid arthritis; sensitization; temporal summation