title: Physical activity monitoring in extremely obese adolescents from the Teen-LABORATORIES study.
abstract: BACKGROUND
  The accuracy of physical activity (PA) monitors to discriminate between PA, sedentary behavior, and nonwear in extremely obese (EO) adolescents is unknown.
  
  
  METHODS
  Twenty-five subjects (9 male/16 female; age = 16.5 ± 2.0 y; BMI = 51 ± 8 kg/m2) wore 3 activity monitors (StepWatch [SAM], Actical [AC], Actiheart [AH]) during a 400-m walk test (400MWT), 2 standardized PA bouts of varying duration, and 1 sedentary bout.
  
  
  RESULTS
  For the 400MWT, percent error between observed and monitor-recorded steps was 5.5 ± 7.1% and 82.1 ± 38.6% for the SAM and AC steps, respectively (observed vs. SAM steps: -17.2 ± 22.2 steps; observed vs. AC steps: -264.5 ± 124.8 steps). All activity monitors were able to differentiate between PA and sedentary bouts, but only SAM steps and AH heart rate were significantly different between sedentary behavior and nonwear (P < .001). For all monitors, sedentary behavior was characterized by bouts of zero steps/counts punctuated by intermittent activity steps/counts; nonwear was represented almost exclusively by zero steps/counts.
  
  
  CONCLUSIONS
  Of all monitors tested, the SAM was most accurate in terms of counting steps and differentiating levels of PA and thus, most appropriate for EO adolescents. The ability to accurately characterize PA intensity in EO adolescents critically depends on activity monitor selection.
authors.affiliation: Dept of Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH.
authors.forename: Renee M
authors.initials: RM
authors.lastname: Jeffreys
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Inge
authors.forename: Todd M
authors.initials: TM
authors.lastname: Jenkins
authors.forename: Wendy C
authors.initials: WC
authors.lastname: King
authors.forename: Vedran
authors.initials: V
authors.lastname: Oruc
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Douglas
authors.forename: Molly S
authors.initials: MS
authors.lastname: Bray
mesh_terms: D056044:Actigraphy; D000293:Adolescent; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D009765:Obesity; D016138:Walking / Q000502:physiology*