title: Sleep characteristics, exercise capacity and physical activity in patients with chronic fatigue syndrome.
abstract: OBJECTIVE
  Unrefreshing sleep and lowered physical activity are commonly observed in chronic fatigue syndrome (CFS) patients, but how they might influence each other remains unexplored. Therefore, this study simultaneously examined the exercise capacity, sleep characteristics and physical activity in CFS patients.
  
  
  METHODS
  Handgrip strength and cycle exercise capacity were assessed in 42 female CFS patients and 24 inactive control subjects. During four consecutive days and nights, energy expenditure, activity and sleep-wake pattern were objectively registered using a Sensewear Armband.
  
  
  RESULTS
  Exercise capacity was significantly lower in CFS patients. In both groups VO2peak correlated with the time subjects were physically active. In CFS patients only, VO2peak correlated negatively with sleeping during the day whilst physical activity level and energy expenditure correlated negatively with sleep latency and lying awake at night.
  
  
  CONCLUSIONS
  In the present study, CFS patients with higher VO2peak tend to sleep less over day. Occupation in physical activities was negatively associated with sleep latency and lying awake at night. Increased physical activity potentially has beneficial effects on sleep quality in CFS. However, a close monitoring of the effects of increasing physical activity is essential to avoid negative effects on the health status of patients.
  
  
  CONCLUSIONS
  Female patients with chronic fatigue syndrome (CFS) have normal sleep latency and sleep efficiency, but sleep more and spent more time in bed as compared to healthy inactive women. Female CFS patients have lower exercise capacity, and a lower physical activity level as compared to healthy inactive women. CFS patients appear to be more sensitive for sleep quality (sleep latency and lying awake at night), which is associated with a low physical activity level.
authors.affiliation: a Department of Human Biometry and Biomechanics , and.|b Department of Movement Education and Sports Training , Vrije Universiteit Brussel , Brussels , Belgium .
authors.forename: Dirk
authors.initials: D
authors.lastname: Aerenhouts
authors.affiliation: c Pain in Motion Research Group .|d Department of Human Physiology and Rehabilitation Sciences , Vrije Universiteit Brussel , Brussels , Belgium .|e Department of Physical Medicine and Physiotherapy , University Hospital Brussels , Brussels , Belgium .
authors.forename: Kelly
authors.initials: K
authors.lastname: Ickmans
authors.affiliation: a Department of Human Biometry and Biomechanics , and.
authors.forename: Peter
authors.initials: P
authors.lastname: Clarys
authors.affiliation: b Department of Movement Education and Sports Training , Vrije Universiteit Brussel , Brussels , Belgium .
authors.forename: Evert
authors.initials: E
authors.lastname: Zinzen
authors.affiliation: f CVS Contactgroep Belgium , Brugge , Belgium , and.
authors.forename: Geert
authors.initials: G
authors.lastname: Meersdom
authors.affiliation: g Private Practice for Internal Medicine , Ghent , Belgium.
authors.forename: Luc
authors.initials: L
authors.lastname: Lambrecht
authors.affiliation: c Pain in Motion Research Group .|d Department of Human Physiology and Rehabilitation Sciences , Vrije Universiteit Brussel , Brussels , Belgium .|e Department of Physical Medicine and Physiotherapy , University Hospital Brussels , Brussels , Belgium .
authors.forename: Jo
authors.initials: J
authors.lastname: Nijs
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D004734:Energy Metabolism; D017079:Exercise Tolerance; D015673:Fatigue Syndrome, Chronic / Q000534:rehabilitation*; D005260:Female; D018737:Hand Strength; D006304:Health Status; D006801:Humans; D008875:Middle Aged; D017286:Polysomnography; D012890:Sleep; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Exercise capacity; fatigue; functional strength; physical activity; sleep