title: Validity of the microsoft kinect system in assessment of compensatory stepping behavior during standing and treadmill walking.
abstract: BACKGROUND
  Rapid compensatory stepping plays an important role in preventing falls when balance is lost; however, these responses cannot be accurately quantified in the clinic. The Microsoft Kinect™ system provides real-time anatomical landmark position data in three dimensions (3D), which may bridge this gap.
  
  
  METHODS
  Compensatory stepping reactions were evoked in 8 young adults by a sudden platform horizontal motion on which the subject stood or walked on a treadmill. The movements were recorded with both a 3D-APAS motion capture and Microsoft Kinect™ systems. The outcome measures consisted of compensatory step times (milliseconds) and length (centimeters). The average values of two standing and walking trials for Microsoft Kinect™ and the 3D-APAS systems were compared usingt-test, Pearson's correlation, Altman-bland plots, and the average difference of root mean square error (RMSE) of joint position.
  
  
  RESULTS
  The Microsoft Kinect™ had high correlations for the compensatory step times (r= 0.75-0.78,p= 0.04) during standing and moderate correlations for walking (r= 0.53-0.63,p= 0.05). The step length, however had a very high correlations for both standing and walking (r> 0.97,p= 0.01). The RMSE showed acceptable differences during the perturbation trials with smallest relative error in anterior-posterior direction (2-3%) and the highest in the vertical direction (11-13%). No systematic bias were evident in the Bland and Altman graphs.
  
  
  CONCLUSIONS
  The Microsoft Kinect™ system provides comparable data to a video-based 3D motion analysis system when assessing step length and less accurate but still clinically acceptable for step times during balance recovery when balance is lost and fall is initiated.
authors.affiliation: Department of Software and Information Systems Engineering, Faculty of Engineering Sciences, Ben-Gurion University, Beer-Sheva, Israel.
authors.forename: Guy
authors.initials: G
authors.lastname: Shani
authors.affiliation: Department of Mechanical Engineering, Faculty of Engineering Sciences, Ben-Gurion University, Beer-Sheva, Israel.
authors.forename: Amir
authors.initials: A
authors.lastname: Shapiro
authors.affiliation: Department of Software and Information Systems Engineering, Faculty of Engineering Sciences, Ben-Gurion University, Beer-Sheva, Israel.
authors.forename: Goldstein
authors.initials: G
authors.lastname: Oded
authors.affiliation: Department of Software and Information Systems Engineering, Faculty of Engineering Sciences, Ben-Gurion University, Beer-Sheva, Israel.
authors.forename: Kagan
authors.initials: K
authors.lastname: Dima
authors.affiliation: Schwartz Movement Analysis & Rehabilitation Laboratory, Physical Therapy Department, Recanati School for Community Health Professions, Faculty of Health Sciences, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva, 84105 Israel.
authors.forename: Itshak
authors.initials: I
authors.lastname: Melzer
keywords: Balance; Compensatory stepping; Falls; Older adults; The Microsoft Kinect™