title: How does cognitive behaviour therapy reduce fatigue in patients with chronic fatigue syndrome? The role of physical activity.
abstract: BACKGROUND
  Cognitive behaviour therapy (CBT) is known to reduce fatigue severity in chronic fatigue syndrome (CFS). How this change in symptomatology is accomplished is not yet understood. The purpose of the present study was to determine whether the effect of CBT on fatigue is mediated by an increase in physical activity.
  
  
  METHODS
  Three randomized controlled trials were reanalysed, previously conducted to evaluate the efficacy of CBT for CFS. In all samples, actigraphy was used to assess the level of physical activity prior and subsequent to treatment or a control group period. The mediation hypothesis was analysed according to guidelines of Baron & Kenny [Journal of Personality and Social Psychology (1986)51, 1173-1182]. A non-parametric bootstrap approach was used to test statistical significance of the mediation effect.
  
  
  RESULTS
  Although CBT effectively reduced fatigue, it did not change the level of physical activity. Furthermore, changes in physical activity were not related to changes in fatigue. Across the samples, the mean mediation effect of physical activity averaged about 1% of the total treatment effect. This effect did not yield significance in any of the samples.
  
  
  CONCLUSIONS
  The effect of CBT on fatigue in CFS is not mediated by a persistent increase in physical activity.
authors.affiliation: Department of Medical Psychology, Radboud University Nijmegen Medical Centre, Expert Centre Chronic Fatigue, The Netherlands. j.wiborg@nkcv.umcn.nl
authors.forename: J F
authors.initials: JF
authors.lastname: Wiborg
authors.forename: H
authors.initials: H
authors.lastname: Knoop
authors.forename: M
authors.initials: M
authors.lastname: Stulemeijer
authors.forename: J B
authors.initials: JB
authors.lastname: Prins
authors.forename: G
authors.initials: G
authors.lastname: Bleijenberg
mesh_terms: D056044:Actigraphy; D000293:Adolescent; D000328:Adult; D001294:Attitude to Health; D015928:Cognitive Behavioral Therapy; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis / Q000523:psychology* / Q000628:therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D016032:Randomized Controlled Trials as Topic; D055815:Young Adult