title: Estimation of daily energy expenditure in pregnant and non-pregnant women using a wrist-worn tri-axial accelerometer.
abstract: BACKGROUND
  Few studies have compared the validity of objective measures of physical activity energy expenditure (PAEE) in pregnant and non-pregnant women. PAEE is commonly estimated with accelerometers attached to the hip or waist, but little is known about the validity and participant acceptability of wrist attachment. The objectives of the current study were to assess the validity of a simple summary measure derived from a wrist-worn accelerometer (GENEA, Unilever Discover, UK) to estimate PAEE in pregnant and non-pregnant women, and to evaluate participant acceptability.
  
  
  METHODS
  Non-pregnant (N = 73) and pregnant (N = 35) Swedish women (aged 20-35 yrs) wore the accelerometer on their wrist for 10 days during which total energy expenditure (TEE) was assessed using doubly-labelled water. PAEE was calculated as 0.9×TEE-REE. British participants (N = 99; aged 22-65 yrs) wore accelerometers on their non-dominant wrist and hip for seven days and were asked to score the acceptability of monitor placement (scored 1 [least] through 10 [most] acceptable).
  
  
  RESULTS
  There was no significant correlation between body weight and PAEE. In non-pregnant women, acceleration explained 24% of the variation in PAEE, which decreased to 19% in leave-one-out cross-validation. In pregnant women, acceleration explained 11% of the variation in PAEE, which was not significant in leave-one-out cross-validation. Median (IQR) acceptability of wrist and hip placement was 9(8-10) and 9(7-10), respectively; there was a within-individual difference of 0.47 (p<.001).
  
  
  CONCLUSIONS
  A simple summary measure derived from a wrist-worn tri-axial accelerometer adds significantly to the prediction of energy expenditure in non-pregnant women and is scored acceptable by participants.
authors.affiliation: Medical Research Council Epidemiology Unit, Institute of Metabolic Science, Cambridge, United Kingdom. vincent.vanhees@mrc-epid.cam.ac.uk
authors.forename: Vincent T
authors.initials: VT
authors.lastname: van Hees
authors.forename: Frida
authors.initials: F
authors.lastname: Renström
authors.forename: Antony
authors.initials: A
authors.lastname: Wright
authors.forename: Anna
authors.initials: A
authors.lastname: Gradmark
authors.forename: Michael
authors.initials: M
authors.lastname: Catt
authors.forename: Kong Y
authors.initials: KY
authors.lastname: Chen
authors.forename: Marie
authors.initials: M
authors.lastname: Löf
authors.forename: Les
authors.initials: L
authors.lastname: Bluck
authors.forename: Jeremy
authors.initials: J
authors.lastname: Pomeroy
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Wareham
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.forename: Søren
authors.initials: S
authors.lastname: Brage
authors.forename: Paul W
authors.initials: PW
authors.lastname: Franks
mesh_terms: D000054:Acceleration; D000203:Activities of Daily Living; D000328:Adult; D001835:Body Weight; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006615:Hip; D006801:Humans; D008991:Monitoring, Physiologic; D009043:Motor Activity / Q000502:physiology*; D011247:Pregnancy; D014953:Wrist; D055815:Young Adult