title: Tracmor system for measuring walking energy expenditure.
abstract: OBJECTIVE
  Walking is an important mode of exercise and is likely to represent a major component of nonexercise activity thermogenesis. The question arises, how best to quantify walking-energy expenditure (EE) in free-living individuals. The triaxial accelerometer for movement registration (Tracmor) is a valid measure of body displacement and so we wanted to evaluate this tool for quantifying walking-EE.
  
  
  OBJECTIVE
  In this study, we test the hypothesis that walking-EE, measured in a Room Calorimeter, can be predicted from Tracmor output using a regression equation derived from a brief Tracmor/treadmill/Metabolic Cart protocol.
  
  
  METHODS
  First, 11 healthy subjects completed a 40-min procedure whereby they wore a Tracmor unit and walked on a treadmill at 0, 1, 2 and 3 mph while EE was measured using a Metabolic Cart. This allowed a regression equation to be defined for each subject to convert Tracmor output to EE. Each subject then entered a Room Calorimeter wearing the Tracmor Unit and walked at two self-selected velocities ('slow', 'fast') while EE was measured. 'Tracmor/regression equation' predictions of walking-EE were compared with Room Calorimeter measurements of walking-EE for the two velocities.
  
  
  RESULTS
  The 'Tracmor/regression equation' prediction of EE for walking slowly was 6.36+/-1.67 kJ/min, and for walking fast it was 11.0+/-2.60 kJ/min. Room Calorimeter measurements were 6.43+/-1.85 and 10.9+/-3.03 kJ/min, respectively. The intraclass correlation coefficient for slow-paced walking was 0.93 (P<0.001), and for fast-paced walking it was 0.82 (P<0.005).
  
  
  CONCLUSIONS
  When combined with laboratory measures of EE, the Tracmor accelerometer provides useful data on walking-EE and is applicable to free-living individuals.
authors.affiliation: Endocrine Research Unit, Mayo Clinic, Rochester, MN 55905, USA. levine.james@mayo.edu
authors.forename: J
authors.initials: J
authors.lastname: Levine
authors.forename: E L
authors.initials: EL
authors.lastname: Melanson
authors.forename: K R
authors.initials: KR
authors.lastname: Westerterp
authors.forename: J O
authors.initials: JO
authors.lastname: Hill
mesh_terms: D000054:Acceleration; D000328:Adult; D002153:Calorimetry, Indirect / Q000295:instrumentation; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D012016:Reference Values; D012044:Regression Analysis; D016138:Walking / Q000502:physiology*