title: Test-Retest Reliability and Concurrent Validity of a Single Tri-Axial Accelerometer-Based Gait Analysis in Older Adults with Normal Cognition.
abstract: OBJECTIVE
  We investigated the concurrent validity and test-retest reliability of spatio-temporal gait parameters measured with a single tri-axial accelerometer (TAA), determined the optimal number of steps required for obtaining acceptable levels of reliability, and compared the validity and reliability of the estimated gait parameters across the three reference axes of the TAA.
  
  
  METHODS
  A total of 82 cognitively normal elderly participants walked around a 40-m long round walkway twice wearing a TAA at their center of body mass. Gait parameters such as cadence, gait velocity, step time, step length, step time variability, and step time asymmetry were estimated from the low pass-filtered signal of the TAA. The test-retest reliability and concurrent validity with the GAITRite® system were evaluated for the estimated gait parameters.
  
  
  RESULTS
  Gait parameters using signals from the vertical axis showed excellent reliability for all gait parameters; the intraclass correlation coefficient (ICC) was 0.79-0.90. A minimum of 26 steps and 14 steps were needed to achieve excellent reliability in step time variability and step time asymmetry, respectively. A strong level of agreement was seen for the basic gait parameters between the TAA and GAITRiteⓇ (ICC = 0.91-0.96).
  
  
  CONCLUSIONS
  The measurement of gait parameters of elderly individuals with normal cognition using a TAA placed on the body's center of mass was reliable and showed superiority over the GAITRiteⓇ with regard to gait variability and asymmetry. The TAA system was a valid tool for measuring basic gait parameters. Considering its wearability and low price, the TAA system may be a promising alternative to the pressure sensor walkway system for measuring gait parameters.
authors.affiliation: Department of Psychiatry, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Seonjeong
authors.initials: S
authors.lastname: Byun
authors.affiliation: Department of Psychiatry, Seoul National University College of Medicine, Seoul, Korea.|Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Ji Won
authors.initials: JW
authors.lastname: Han
authors.affiliation: Department of Psychiatry, Yonsei University Wonju Severance Christian Hospital, Wonju, Korea.
authors.forename: Tae Hui
authors.initials: TH
authors.lastname: Kim
authors.affiliation: Department of Psychiatry, Seoul National University College of Medicine, Seoul, Korea.|Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Korea.|Department of Brain and Cognitive Science, Seoul National University College of Natural Sciences, Seoul, Korea.
authors.forename: Ki Woong
authors.initials: KW
authors.lastname: Kim
mesh_terms: D000054:Acceleration; D061725:Accelerometry / Q000379:methods*; D000368:Aged; D003071:Cognition; D005260:Female; D005684:Gait; D006801:Humans; D008297:Male; D008875:Middle Aged; D016138:Walking