title: Influence of accelerometer type and placement on physical activity energy expenditure prediction in manual wheelchair users.
abstract: OBJECTIVE
  To assess the validity of two accelerometer devices, at two different anatomical locations, for the prediction of physical activity energy expenditure (PAEE) in manual wheelchair users (MWUs).
  
  
  METHODS
  Seventeen MWUs (36 ± 10 yrs, 72 ± 11 kg) completed ten activities; resting, folding clothes, propulsion on a 1% gradient (3,4,5,6 and 7 km·hr-1) and propulsion at 4km·hr-1 (with an additional 8% body mass, 2% and 3% gradient) on a motorised wheelchair treadmill. GT3X+ and GENEActiv accelerometers were worn on the right wrist (W) and upper arm (UA). Linear regression analysis was conducted between outputs from each accelerometer and criterion PAEE, measured using indirect calorimetry. Subsequent error statistics were calculated for the derived regression equations for all four device/location combinations, using a leave-one-out cross-validation analysis.
  
  
  RESULTS
  Accelerometer outputs at each anatomical location were significantly (p < .01) associated with PAEE (GT3X+-UA; r = 0.68 and GT3X+-W; r = 0.82. GENEActiv-UA; r = 0.87 and GENEActiv-W; r = 0.88). Mean ± SD PAEE estimation errors for all activities combined were 15 ± 45%, 14 ± 50%, 3 ± 25% and 4 ± 26% for GT3X+-UA, GT3X+-W, GENEActiv-UA and GENEActiv-W, respectively. Absolute PAEE estimation errors for devices varied, 19 to 66% for GT3X+-UA, 17 to 122% for GT3X+-W, 15 to 26% for GENEActiv-UA and from 17.0 to 32% for the GENEActiv-W.
  
  
  CONCLUSIONS
  The results indicate that the GENEActiv device worn on either the upper arm or wrist provides the most valid prediction of PAEE in MWUs. Variation in error statistics between the two devices is a result of inherent differences in internal components, on-board filtering processes and outputs of each device.
authors.affiliation: Centre for DisAbility Sport and Health (DASH), Department for Health, University of Bath, Bath, Somerset, United Kingdom.
authors.forename: Tom Edward
authors.initials: TE
authors.lastname: Nightingale
authors.affiliation: Centre for DisAbility Sport and Health (DASH), Department for Health, University of Bath, Bath, Somerset, United Kingdom.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Walhin
authors.affiliation: Centre for DisAbility Sport and Health (DASH), Department for Health, University of Bath, Bath, Somerset, United Kingdom.
authors.forename: Dylan
authors.initials: D
authors.lastname: Thompson
authors.affiliation: Centre for DisAbility Sport and Health (DASH), Department for Health, University of Bath, Bath, Somerset, United Kingdom.
authors.forename: James Lee John
authors.initials: JL
authors.lastname: Bilzon
mesh_terms: D061725:Accelerometry; D000328:Adult; D001132:Arm; D002153:Calorimetry, Indirect; D004734:Energy Metabolism; D006339:Heart Rate; D006801:Humans; D016014:Linear Models; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D014910:Wheelchairs; D014953:Wrist