title: Reliability of heart rate variability measures at rest and during light exercise in children.
abstract: OBJECTIVE
  To investigate the reliability of heart rate variability (HRV) measures at rest and during light exercise in children.
  
  
  METHODS
  Short term (five minute) HRV was assessed in 12 children (11-12 years of age). HRV measures were collected at rest with the children supine, breathing at 12 breaths/min, and during exercise on a cycle ergometer while exercising at 25% of peak oxygen uptake. Both resting and exercise data were collected twice from each child.
  
  
  RESULTS
  Intraclass correlation coefficients were low to moderate for most measures with wide confidence intervals for each variable in both resting and exercise conditions. Random variation (typical error) within repeated measurements ranged from 31% to 187%.
  
  
  CONCLUSIONS
  These preliminary findings suggest that HRV measures are unreliable at rest and during light exercise in children aged 11-12 years. Tighter control of extraneous influences is recommended.
authors.affiliation: Children's Health and Exercise Research Centre, University of Exeter, Heavitree Road, Exeter EX1 2LU, Devon, UK. r.j.winsley@exeter.ac.uk
authors.forename: R J
authors.initials: RJ
authors.lastname: Winsley
authors.forename: N
authors.initials: N
authors.lastname: Armstrong
authors.forename: K
authors.initials: K
authors.lastname: Bywater
authors.forename: S G
authors.initials: SG
authors.lastname: Fawkner
mesh_terms: D002648:Child; D016001:Confidence Intervals; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D012146:Rest; D012680:Sensitivity and Specificity