INFLUENCE OF CALCULATION PARAMETERS ON NONLINEAR DYNAMICS MEASURES

Nonlinear analysis methods based on a dynamical systems approach have become more prevalent in recent biomechanics studies. The aim of this study is to identify the range of time delay and embedding dimension values estimated for gait data, and how sensitive Lyapunov exponent and correlation dimension are to the range of these values. A participant walked at 3 km/h and ran at 9 km/h on a treadmill for 2 minutes. Lyaponuv exponent and correlation dimension were calculated based on a combination of the optimal and mean average time delay (TD) and embedding dimension (ED) for both angle and marker data. In the majority of literature, only one ED and TD is considered for LyE estimation, based on an average across data or values suggested in previous papers. However, the results of our study show that every angle or position, has an optimum ED and TD, and the use of these values affects the nonlinear dynamics values in non-trivial ways

EFFECTS OF AGEING ON GAIT COMPLEXITY

Ageing alters gait patterns that influences the control mechanism of human movement. The aim of this study was to identify the age-related differences in complexity of gait kinematics. Gait is a fundamental but complex action, and loss of complexity has been suggested with ageing. In this study multiscale entropy (MSE) analysis was used to investigate complexity in gait. Whole body kinematic data for 10 younger adults (21±1.84 years old) and 10 older adults (62.7±2.2 years old) running at 9 km/h on the treadmill for 2 minutes were analysed. Body centre of mass (CoM) were calculated. MSE of CoM position, and ankle, knee and hip angles were estimated. Hip angular displacement exhibited higher MSE (higher complexity) compared to the CoM position, ankle and knee angular displacement. MSE increased from ankle to knee to hip. MSE of the Hip was significantly lower for the older compared to the younger group, but MSE was not different between young and old participants for other variables. Loss of complexity may only be observed for some kinematic variables, which is a key point to consider for future work applying these techniques to understand gait changes with age