Research Article| Volume 70, P146-152, December 2019

The validity and usability of an eight marker model for avatar-based biofeedback gait training

  • A.T.C. Booth
    Corresponding author at: Department of Rehabilitation Medicine, Amsterdam Movement Science, VU University Medical Center, 1007 MB Amsterdam, Netherlands.
    Department of Rehabilitation Medicine, Amsterdam UMC, VU University Medical Center, Amsterdam Movement Sciences, Netherlands

    Department of Clinical Applications and Research, Motek Medical B.V., Amsterdam, Netherlands
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  • M.M. van der Krogt
    Department of Rehabilitation Medicine, Amsterdam UMC, VU University Medical Center, Amsterdam Movement Sciences, Netherlands
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  • A.I. Buizer
    Department of Rehabilitation Medicine, Amsterdam UMC, VU University Medical Center, Amsterdam Movement Sciences, Netherlands
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  • F. Steenbrink
    Department of Clinical Applications and Research, Motek Medical B.V., Amsterdam, Netherlands
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  • J. Harlaar
    Department of Rehabilitation Medicine, Amsterdam UMC, VU University Medical Center, Amsterdam Movement Sciences, Netherlands

    Department Biomechanical Engineering, Delft University of Technology, Delft, Netherlands
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      • An application for biofeedback gait training was developed for an integrated treadmill.
      • With 8 passive markers, simple gait biomechanics can be calculated in real-time.
      • Gait can be visualised and challenged using an avatar in virtual reality.
      • The application is clinically usable and may benefit patient populations undergoing gait training.



      Virtual reality presents a platform for therapeutic gaming, and incorporation of immersive biofeedback on gait may enhance outcomes in rehabilitation. Time is limited in therapeutic practice, therefore any potential gait training tool requires a short set up time, while maintaining clinical relevance and accuracy. The aim of this study was to develop, validate, and establish the usability of an avatar-based application for biofeedback-enhanced gait training with minimal set up time.


      A simplified, eight marker model was developed using eight passive markers placed on anatomical landmarks. This allowed for visualisation of avatar-based biofeedback on pelvis kinematics, hip and knee sagittal angles in real-time. Retrospective gait analysis data from typically developing children (n = 41) and children with cerebral palsy (n = 25), were used to validate eight marker model. Gait outcomes were compared to the Human Body Model using statistical parametric mapping. Usability for use in clinical practice was tested in five clinical rehabilitation centers with the system usability score.


      Gait outcomes of Human Body Model and eight marker model were comparable, with small differences in gait parameters. The discrepancies between models were <5°, except for knee extension where eight marker model showed significantly less knee extension, especially towards full extension. The application was considered of ‘high marginal acceptability’ (system usability score, mean 68 (SD 13)).


      Gait biofeedback can be achieved, to acceptable accuracy for within-session gait training, using an eight marker model. The application may be considered usable and implemented for use in patient populations undergoing gait training.


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