title: The accuracy of a simple, low-cost GPS data logger/receiver to study outdoor human walking in view of health and clinical studies.
abstract: BACKGROUND
  Accurate and objective measurements of physical activity and lower-extremity function are important in health and disease monitoring, particularly given the current epidemic of chronic diseases and their related functional impairment.
  
  
  OBJECTIVE
  The aim of the present study was to determine the accuracy of a handy (lightweight, small, only one stop/start button) and low-cost (∼$75 with its external antenna) Global Positioning System (GPS) data logger/receiver (the DG100) as a tool to study outdoor human walking in perspective of health and clinical research studies. Methods. Healthy subjects performed two experiments that consisted of different prescribed outdoor walking protocols. Experiment 1. We studied the accuracy of the DG100 for detecting bouts of walking and resting. Experiment 2. We studied the accuracy of the DG100 for estimating distances and speeds of walking.
  
  
  RESULTS
  Experiment 1. The performance in the detection of bouts, expressed as the percentage of walking and resting bouts that were correctly detected, was 92.4% [95% Confidence Interval: 90.6-94.3]. Experiment 2. The coefficients of variation [95% Confidence Interval] for the accuracy of estimating the distances and speeds of walking were low: 3.1% [2.9-3.3] and 2.8% [2.6-3.1], respectively.
  
  
  CONCLUSIONS
  The DG100 produces acceptable accuracy both in detecting bouts of walking and resting and in estimating distances and speeds of walking during the detected walking bouts. However, before we can confirm that the DG100 can be used to study walking with respect to health and clinical studies, the inter- and intra-DG100 variability should be studied.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT00485147.
authors.affiliation: APCoSS, Institute of Physical Education and Sports Sciences (IFEPSA), UCO, Les Ponts de Cé, France.
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Noury-Desvaux
authors.forename: Pierre
authors.initials: P
authors.lastname: Abraham
authors.forename: Guillaume
authors.initials: G
authors.lastname: Mahé
authors.forename: Thomas
authors.initials: T
authors.lastname: Sauvaget
authors.forename: Georges
authors.initials: G
authors.lastname: Leftheriotis
authors.forename: Alexis
authors.initials: A
authors.lastname: Le Faucheur
mesh_terms: D000328:Adult; D003625:Data Collection / Q000191:economics* / Q000295:instrumentation / Q000379:methods*; D005260:Female; D040362:Geographic Information Systems / Q000191:economics*; D006262:Health / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D016138:Walking / Q000706:statistics & numerical data*; D055815:Young Adult