Mehdizadeh, S. | Search bioRxiv

bioRxiv2018

Effect of real-time video feedback on the gait foot placement regularity and symmetry in individuals with trans-tibial amputation: A case study

Low stability and asymmetrical gait are two important challenges in gait of individuals with trans-tibial amputation. The aim of this case report was to determine the feasibility and effectiveness of a real-time video feedback of foot placement on stability (i.e. foot placement regularity) and symmetry of trans-tibial amputees. Furthermore, we aimed at differentiating the effect of video feedback from front, back and lateral views on amputees walking. Seven male participants with unilateral trans-tibial amputation took part in this study. Each participant walked for 2 minutes in four conditions: no video feedback, video feedback from front view, video feedback from back view and video feedback from lateral view. Participants motion was recorded using five motion capture cameras. Nonlinear measure of sample entropy was adopted to quantify foot placement regularity (i.e. stability). The symmetry of step length and width was also determined using symmetry angle algorithm. Results demonstrated that video feedback significantly led to more regular and more symmetrical step length. Our findings suggest that amputees rely on visual feedback to have more stable and more symmetrical gait. The findings of this study suggest that implementing of video feedback gait training could reduce neuromusculoskeletal problems resulted from asymmetrical gait.

neuroscience↗

bioRxiv2018

A Robust Method to Estimate the Largest Lyapunov Exponent of Noisy Signals: A Revision to the Rosenstein’s Algorithm

AimThis study proposed a revision to the Rosensteins method of numerical calculation of largest Lyapunov exponent (LyE) to make it more robust to noise.\n\nMethodsTo this aim, the effect of increasing number of initial neighboring points on the LyE value was investigated and compared to the values obtained by filtering the time series. Both simulated (Lorenz and passive dynamic walker) and experimental (human walking) time series were used to calculate LyE. The number of initial neighbors used to calculate LyE for all time series was 1 (the original Rosensteins method), 2, 3, 4, 5, 10, 15, 20, 25, and 30 data points.\n\nResultsThe results demonstrated that the LyE graph reached a plateau at the 15-point neighboring condition inferring that the LyE values calculated using at least 15 neighboring points were consistent and reliable.\n\nConclusionThe proposed method could be used to calculate LyE more reliably in experimental time series acquired from biological systems where noise is omnipresent.

biophysics↗