title: Accuracy of a piezoelectric pedometer in persons with and without Down syndrome.
abstract: BACKGROUND
  Piezoelectric pedometers with a tri-axial accelerometer mechanism may effectively monitor physical activity in persons with Down syndrome (DS), but their accuracy has not been determined in this population.
  
  
  OBJECTIVE
  To examine the accuracy of a pedometer with a tri-axial accelerometer mechanism in measuring steps at different walking speeds in persons with and without DS.
  
  
  METHODS
  Eighteen persons with DS (8 women; age 25±7y) and 22 persons without DS (9 women; 26±5y) participated in this study. Participants completed six over-ground walking trials at the preferred speed and at 0.5, 0.75, 1.0, 1.25, and 1.5ms-1, each lasting 6min. The steps taken were measured with hand-tally and with the Walk4Life MVPa piezoelectric pedometer. Pedometer accuracy was assessed with absolute percent error and Bland-Altman plots.
  
  
  RESULTS
  Absolute percent error did not differ between persons with and without DS across speeds. Error decreased with increased speed (p<0.001), but leveled off at ≥1.0ms-1. Pedometers underestimated steps at 0.5 and 0.75ms-1, but were highly accurate at the preferred walking speed and at speeds ≥1.0ms-1.
  
  
  CONCLUSIONS
  A piezoelectric pedometer with a tri-axial accelerometer mechanism measures steps with high accuracy at the preferred walking speed and at speeds ≥1.0ms-1in persons with and without DS. Accuracy, however, is compromised at slower speeds. Across speeds, pedometer error is similar between persons with and without DS.
authors: Department of Kinesiology, Mississippi State University, 240 McCarthy Gym, P.O. Box 6186, MS 39762, USA. Electronic address: sagiovlasitis@colled.msstate.edu.
authors: Stamatis
authors: S
authors: Agiovlasitis
authors: Department of Exercise Science, Arnold School of Public Health, University of South Carolina, 921 Assembly Street, RM 131, Columbia, SC 29208, USA.
authors: Michael W
authors: MW
authors: Beets
authors: Department of Kinesiology, Mississippi State University, 240 McCarthy Gym, P.O. Box 6186, MS 39762, USA.
authors: John
authors: J
authors: Lamberth
authors: Department of Physical Therapy, Wichita State University, 417 Ahlberg Hall, Wichita, KS 67260, USA.
authors: Kenneth H
authors: KH
authors: Pitetti
authors: College of Applied Health Sciences, University of Illinois at Chicago, 808 South Wood Street, 169 CMET, Chicago, IL 60612, USA.
authors: Bo
authors: B
authors: Fernhall
mesh_terms: D061725:Accelerometry / Q000295:instrumentation*; D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D004314:Down Syndrome; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D016138:Walking; D000072797:Walking Speed; D055815:Young Adult
keywords: Activity monitor; Disability; Exercise; Physical activity