title: Dose-response relation between physical activity and blood pressure in youth.
abstract: The dose-response relationship between physical activity (PA) and cardiovascular health in children and adolescents is unclear. Blood pressure (BP) is a practical and useful measure of cardiovascular health in youth.
  
  
  OBJECTIVE
  This study aims to examine the dose-response relationship between objectively measured PA and BP in children and adolescents.
  
  
  METHODS
  The sample included 1170 youth aged 8-17 yr from the 2003/04 U.S. National Health and Nutrition Examination Survey. PA was measured using Actigraph accelerometers (Ft. Walton Beach, FL, USA) over 7 d. Thresholds of 2000 and 3000 counts per minute were used to denote those minutes where the participants were engaged in total PA and moderate-to-vigorous intensity PA, respectively. BP was measured using standard procedures. Systolic and diastolic BP values were adjusted for age, height, and sex. Participants with adjusted BP values > or = 90th percentile were considered to have hypertension. Thirty-six fractional polynomial regression models were used to obtain the dose-response curve that best fit the relation between PA with systolic BP, diastolic BP, and hypertension.
  
  
  RESULTS
  Inverse dose-response relations were observed between total and moderate-to-vigorous PA with systolic and diastolic BP. The slopes of the curves were modest indicating a minimal influence of PA on mean BP values. The likelihood of having hypertension decreased in a curvilinear manner with increasing minutes of PA. At 30 and 60 min.d of moderate-to-vigorous PA, the odd ratios (95% confidence intervals) for hypertension were 0.50 (0.28-0.64) and 0.38 (0.17-0.52), respectively, in comparison to no PA.
  
  
  CONCLUSIONS
  A modest dose-response relation was observed between PA and mean systolic and diastolic BP values. PA did, however, have a strong gradient effect on BP when predicting hypertensive values. These results support the public health recommendation that children and youth accumulate at least 60 min of moderate-to-vigorous PA daily.
authors.affiliation: School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Mark
authors.forename: Ian
authors.initials: I
authors.lastname: Janssen
mesh_terms: D000293:Adolescent; D001794:Blood Pressure / Q000502:physiology*; D002648:Child; D005260:Female; D006801:Humans; D006973:Hypertension / Q000517:prevention & control*; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009749:Nutrition Surveys; D016017:Odds Ratio