title: Precision and accuracy of an ankle-worn accelerometer-based pedometer in step counting and energy expenditure.
abstract: BACKGROUND
  Walking is a widely used approach to increase physical activity levels in obese patients. In this paper, we investigate the precision and accuracy of an ankle-worn dual-axis accelerometer (Stepwatch) and investigate its potential application as a predictor of energy expenditure.
  
  
  METHODS
  Twenty healthy subjects (10 lean, 10 obese) wore spring-levered (Accusplit), piezoelectric (Omron HF-100), and Stepwatch pedometers. Subjects walked on a treadmill at 1, 2, and 3 mph and in a hallway at 1 and 1.85 mph, during which energy expenditure was measured.
  
  
  RESULTS
  The Stepwatch counted 99.7 +/- 0.67% (mean +/- SEM) of the manual counts. In comparison, the Omron pedometer counted 61 +/- 3.3% and the Accusplit counted 26 +/- 2.8% of the manual counts at 1 mph although all pedometers were accurate (> 98% of counts) at 3 mph. In repeated measures, the Stepwatch produced negligible variance (SD = 0.36) over all speed whereas the other pedometers showed a large amount of variance at all speed (SD = 4-13). Stepwatch counts were predictive of walking energy expenditure corrected by weight (r2 > 0.8).
  
  
  CONCLUSIONS
  The counts from the Stepwatch were virtually identical to the manual counts from a trained investigator and provided a reliable predictor of walking energy expenditure.
authors.affiliation: Endocrine Research Unit, Division of Endocrinology, Department of Internal Medicine, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Randal C
authors.initials: RC
authors.lastname: Foster
authors.forename: Lorraine M
authors.initials: LM
authors.lastname: Lanningham-Foster
authors.forename: Chinmay
authors.initials: C
authors.lastname: Manohar
authors.forename: Shelly K
authors.initials: SK
authors.lastname: McCrady
authors.forename: Lana J
authors.initials: LJ
authors.lastname: Nysse
authors.forename: Kenton R
authors.initials: KR
authors.lastname: Kaufman
authors.forename: Denny J
authors.initials: DJ
authors.lastname: Padgett
authors.forename: James A
authors.initials: JA
authors.lastname: Levine
mesh_terms: D000328:Adult; D000842:Ankle; D015992:Body Mass Index; D004734:Energy Metabolism / Q000502:physiology*; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008910:Minnesota; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D016138:Walking / Q000502:physiology*