title: How much activity do youth get? A quantitative review of heart-rate measured activity.
abstract: OBJECTIVE
  Recommendations for adult physical activity have shifted from 20 to 60 minutes of continuous vigorous activity 3 to 5 times a week to accumulation of 30 minutes of moderate to vigorous physical activity most days of the week. Variations of these guidelines also have been suggested for children, based on the idea of accumulating moderate to vigorous physical activity throughout the day, rather than attaining vigorous physical activity in continuous blocks. The goal of this study was to assess accumulated amounts of physical activity at different intensities in children.
  
  
  METHODS
  We reviewed 26 studies (n = 1883) in youth aged 3 to 17 years that used heart-rate recording to measure physical activity in children to determine accumulated daily activity. Included were studies that provided time being active for at least 2 heart rate intensities at or above 120 beats/minute. Descriptive characteristics of the study groups were determined, and the influence of age, gender, and hours and days of observation on the slope of activity time as a function of percentage of heart rate reserve (HRR) was determined using hierarchical linear regression.
  
  
  RESULTS
  Youth attained 128.0 +/- 45.6, 47.1 +/- 14.9, 29.3 +/- 13.7, and 14.7 +/- 6.0 minutes/day between 20% to 40%, 40% to 50%, 50% to 60%, and greater than 60% HRR, respectively. Age was a significant predictor of the intercept and slope of the physical activity and %HRR relationship.
  
  
  CONCLUSIONS
  Youth of all ages attain >60 minutes/day of low-intensity physical activity and approximately 30 minutes/day of activity at traditional cardiovascular fitness training levels of 50% or more of HRR. Recommendations for youth activity are discussed.
authors.affiliation: Departments of Pediatrics, State University of New York at Buffalo, Buffalo, New York, USA. lhenet@acsu.buffalo.edu
authors.forename: L H
authors.initials: LH
authors.lastname: Epstein
authors.forename: R A
authors.initials: RA
authors.lastname: Paluch
authors.forename: L E
authors.initials: LE
authors.lastname: Kalakanis
authors.forename: G S
authors.initials: GS
authors.lastname: Goldfield
authors.forename: F J
authors.initials: FJ
authors.lastname: Cerny
authors.forename: J N
authors.initials: JN
authors.lastname: Roemmich
mesh_terms: D000203:Activities of Daily Living; D000293:Adolescent; D000704:Analysis of Variance; D002648:Child; D002675:Child, Preschool; D005060:Europe; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008019:Life Style; D016014:Linear Models; D008297:Male; D010809:Physical Fitness / Q000502:physiology*; D014481:United States