title: Wear Compliance and Activity in Children Wearing Wrist- and Hip-Mounted Accelerometers.
abstract: OBJECTIVE
  This study aimed to 1) explore children's compliance to wearing wrist- and hip-mounted accelerometers, 2) compare children's physical activity (PA) derived from raw accelerations of wrist and hip, and 3) examine differences in raw and counts PA measured by hip-worn accelerometry.
  
  
  METHODS
  One hundred and twenty-nine 9- to 10-yr-old children wore a wrist-mounted GENEActiv accelerometer (GAwrist) and a hip-mounted ActiGraph GT3X+ accelerometer (AGhip) for 7 d. Both devices measured raw accelerations, and the AGhip also provided count-based data.
  
  
  RESULTS
  More children wore the GAwrist than those from the AGhip regardless of wear time criteria applied (P < 0.001-0.035). Raw data signal vector magnitude (r = 0.68), moderate PA (MPA) (r = 0.81), vigorous PA (VPA) (r = 0.85), and moderate-to-vigorous PA (MVPA) (r = 0.83) were strongly associated between devices (P < 0.001). GAwrist signal vector magnitude (P = 0.001), MPA (P = 0.037), VPA (P = 0.002), and MVPA (P = 0.016) were significantly greater than those from the AGhip. According to GAwrist raw data, 86.9% of children engaged in at least 60 min · d(-1) of MVPA, compared with 19% for AGhip. ActiGraph MPA (raw) was 42.00 ± 1.61 min · d(-1) compared with 35.05 ± 0.99 min · d(-1) (counts) (P = 0.02). ActiGraph VPA was 7.59 ± 0.46 min · d(-1) (raw) and 37.06 ± 1.85 min · d(-1) (counts; P = 0.19).
  
  
  CONCLUSIONS
  In children, accelerometer wrist placement promotes superior compliance than the hip. Raw accelerations were significantly higher for GAwrist compared with those for AGhip possibly because of placement location and technical differences between devices. AGhip PA calculated from raw accelerations and counts differed substantially, demonstrating that PA outcomes derived from cut points for raw output and counts cannot be directly compared.
authors.affiliation: 1Department of Sport and Physical Activity, Edge Hill University, Ormskirk, UNITED KINGDOM; 2Department of Physical Education and Sport Sciences, University of Limerick, Limerick, IRELAND; 3Physical Activity Exchange, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UNITED KINGDOM; 4Diabetes Research Centre, University of Leicester, Leicester General Hospital, Leicester, UNITED KINGDOM; 5National Institute for Health Research Leicester-Loughborough Diet, Lifestyle, and Physical Activity Biomedical Research Unit, Leicester, UNITED KINGDOM; and 6MoveLab, Physical Activity and Exercise Research, Institute of Cellular Medicine, Newcastle University, Newcastle, UNITED KINGDOM.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Fairclough
authors.forename: Robert
authors.initials: R
authors.lastname: Noonan
authors.forename: Alex V
authors.initials: AV
authors.lastname: Rowlands
authors.forename: Vincent
authors.initials: V
authors.lastname: Van Hees
authors.forename: Zoe
authors.initials: Z
authors.lastname: Knowles
authors.forename: Lynne M
authors.initials: LM
authors.lastname: Boddy
mesh_terms: D061725:Accelerometry / Q000295:instrumentation* / Q000379:methods; D002648:Child; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D013997:Time Factors