Citation

Raffalt P, Alkjaer T, Brynjólfsson B, Rgensen LJ, Bartholdy CR, Henriksen M. J. Biomech. Eng. 2018; ePub(ePub): ePub.

Affiliation

The Parker Institute, Copenhagen University Hospital Bispebjerg, Frederiksberg, Denmark; Department of Physical and Occupational Therapy, Copenhagen University Hospital Bispebjerg, Frederiksberg, Denmark.

Copyright

(Copyright © 2018, American Society of Mechanical Engineers)

DOI

10.1115/1.4041044

PMID

30098178

Abstract

The present study investigated the day-to-day reliability (quantified by the absolute and relative reliability) of nonlinear methods that assess human locomotion dynamics. Twenty-four participants completed 5 minutes of treadmill walking at self-selected preferred speed on two separate days. Lower limb kinematics were recorded at 100Hz and hip, knee and ankle joint angles, three dimensional sacrum marker displacement and stride time intervals were extracted for 170 consecutive strides. The largest Lyapunov exponent and correlation dimension were calculated for the joint angle and sacrum displacement data using three different state space reconstruction methods (group average, test-retest average, individual time delay and embedding dimension). Sample entropy and detrended fluctuation analysis were applied to the stride time interval time series. Relative reliability was assessed using intra-class correlation coefficients and absolute reliability was determined by measurement error (ME). The group average state space reconstruction method resulted in the best relative and absolute reliability of the LyE parameter when compared to the individual and test-retest average methods. The detrended fluctuation analysis exhibited good reliability, while sample entropy showed poor reliability. The results comprise a reference material that can inspire and guide future studies of non-linear gait dynamics.

Language: en