1Robot-assisted training is a promising tool under development for improving walking 2 function based on repetitive goal-oriented task practice. The challenges in developing 3 the controllers for gait training devices that promote desired changes in gait is 4 complicated by the limited understanding of the human response to robotic input. A 5 possible method of controller formulation can be based on the principle of 6 bio-inspiration, where a robot is controlled to apply the change in joint moment applied 7 by human subjects when they achieve a gait feature of interest. However, it is currently 8 unclear how lower extremity joint moments are modulated by even basic gait 9 spatio-temporal parameters.
10In this study, we investigated how sagittal plane joint moments are affected by a 11 factorial modulation of two important gait parameters: gait speed and stride length.
12November 10, 2018 1/25We present the findings obtained from 20 healthy control subjects walking at various 13 treadmill-imposed speeds and instructed to modulate stride length utilizing real-time 14 visual feedback. Implementing a continuum analysis of inverse-dynamics derived joint 15 moment profiles, we extracted the effects of gait speed and stride length on joint 16 moment throughout the gait cycle. Moreover, we utilized a torque pulse approximation 17 analysis to determine the timing and amplitude of torque pulses that approximate the 18 difference in joint moment profiles between stride length conditions, at all gait speed 19 conditions.
20Our results show that gait speed has a significant effect on the moment profiles in all 21 joints considered, while stride length has more localized effects, with the main effect 22 observed on the knee moment during stance, and smaller effects observed for the hip 23 joint moment during swing and ankle moment during the loading response. Moreover,
24our study demonstrated that trailing limb angle, a parameter of interest in programs 25 targeting propulsion at push-off, was significantly correlated with stride length. As such, 26our study has generated assistance strategies based on pulses of torque suitable for 27 implementation via a wearable exoskeleton with the objective of modulating stride 28 length, and other correlated variables such as trailing limb angle. 29 Introduction 30 Robot-assisted training is a promising tool under development for improving walking 31 function [1, 2]. A primary indicator of gait performance improvement is gait speed (GS), 32 which is associated with a better quality of life [3] and overall functional status [4]. 33 Currently, it is not well understood how the modulation of assistance provided by a 34 robot during gait training will lead to changes in GS. The gait parameter of GS is 35 known to be correlated with anterior-posterior ground reaction force, the propulsive 36 force of the foot against the ground. Furthermore, propulsive impulse, the propulsive 37 force integrated over time, is associated with the posture of the trailing limb at 38 push-off [5]. The posture of ...