title: Estimation of energy expenditure using CSA accelerometers at hip and wrist sites.
abstract: OBJECTIVE
  This study was designed to establish prediction models that relate hip and wrist accelerometer data to energy expenditure (EE) in field and laboratory settings. We also sought to determine whether the addition of a wrist accelerometer would significantly improve the prediction of EE (METs), compared with a model that used a hip accelerometer alone.
  
  
  METHODS
  Seventy participants completed one to six activities within the categories of yardwork, housework, family care, occupation, recreation, and conditioning, for a total of 5 to 12 participants tested per activity. EE was measured using the Cosmed K4b2 portable metabolic system. Simultaneously, two Computer Science and Applications, Inc. (CSA) accelerometers (model 7164), one worn on the wrist and one worn on the hip, recorded body movement. Correlations between EE measured by the Cosmed and the counts recorded by the CSA accelerometers were calculated, and regression equations were developed to predict EE from the CSA data.
  
  
  RESULTS
  The wrist, hip, and combined hip and wrist regression equations accounted for 3.3%, 31.7%, and 34.3% of the variation in EE, respectively. The addition of the wrist accelerometer data to the hip accelerometer data to form a bivariate regression equation, although statistically significant (P = 0.002), resulted in only a minor improvement in prediction of EE. Cut points for 3 METs (574 hip counts), 6 METs (4945 hip counts), and 9 METs (9317 hip counts) were also established.
  
  
  CONCLUSIONS
  The small amount of additional accuracy gained from the wrist accelerometer is offset by the extra time required to analyze the data and the cost of the accelerometer.
authors.affiliation: Department of Exercise Science and Sport Management, University of Tennessee, Knoxville 37996, USA. aswartz@utkux.utcc.utk.edu
authors.forename: A M
authors.initials: AM
authors.lastname: Swartz
authors.forename: S J
authors.initials: SJ
authors.lastname: Strath
authors.forename: D R
authors.initials: DR
authors.lastname: Bassett
authors.forename: W L
authors.initials: WL
authors.lastname: O'Brien
authors.forename: G A
authors.initials: GA
authors.lastname: King
authors.forename: B E
authors.initials: BE
authors.lastname: Ainsworth
mesh_terms: D000328:Adult; D000368:Aged; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D005260:Female; D006615:Hip; D006801:Humans; D008124:Locomotion; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D010101:Oxygen Consumption