title: Heart rate variability in obese children: relations to total body and visceral adiposity, and changes with physical training and detraining.
abstract: OBJECTIVE
  Heart rate variability provides non-invasive information about cardiac parasympathetic activity (PSA). We determined in obese children: (1) relations of baseline PSA to body composition and hemodynamics; (2) effects of physical training (PT) and cessation of PT; and (3) which factors explained individual differences in responsivity of PSA to the PT.
  
  
  METHODS
  The root mean square of successive differences (RMSSD) was the index of PSA. Obese children (n = 79) were randomly assigned to groups that participated in PT during the first or second 4-month periods of the study.
  
  
  RESULTS
  Baseline RMSSD was significantly (p<0.05) associated with lower levels of: fat mass, fat-free mass, subcutaneous abdominal adipose tissue, resting heart rate (HR), resting systolic blood pressure, and exercise HR. Stepwise multiple regression produced a final model (R2 = 0.36) that included only resting HR. The analysis of changes over the three time points of the study found a significant (p = 0.026) time by group interaction, such that RMSSD increased during periods of PT and decreased following cessation of PT. Greater individual increases in response to the PT (p<0.05) were seen in those who had lower pre-PT RMSSD levels, showed the greatest decreases in resting HR, and increased most in vigorous physical activity. The final regression model retained only the change in resting HR as a significant predictor of the changes in the RMSSD (R2 = 0.23).
  
  
  CONCLUSIONS
  Regular exercise that improved fitness and body composition had a favorable effect on PSA in obese children.
authors.affiliation: Georgia Prevention Institute, Department of Pediatrics, Medical College of Georgia, 30912, USA. bgutin@mail.mcg.edu
authors.forename: B
authors.initials: B
authors.lastname: Gutin
authors.forename: P
authors.initials: P
authors.lastname: Barbeau
authors.forename: M S
authors.initials: MS
authors.lastname: Litaker
authors.forename: M
authors.initials: M
authors.lastname: Ferguson
authors.forename: S
authors.initials: S
authors.lastname: Owens
mesh_terms: D000273:Adipose Tissue; D001794:Blood Pressure; D001823:Body Composition; D002648:Child; D004032:Diet; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D012044:Regression Analysis