Date of Award

12-11-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Systems Engineering

First Advisor

Kamran Iqbal

Abstract

Background: In human postural studies, it is believed that low dimensional motor modules are combined to simplify the movement. These lower dimensional modules are termed as muscle synergies (MS). Therefore, understanding MS evoked by postural perturbation may provide us the specific muscle co-activation pattern for stability. Research Aim: The scope of our study is to identify synergies associated with postural stability while walking on a perturbing platform and study the effect of different proficiency levels on their size and structure. Methodology: We asked nine human participants to walk overground and on a slackline to study task-specific modulation of synergy structures. To study proficiency-based synergies, we recruited individuals with different proficiency levels and categorized them into different groups. We acquired electromyography signals (EMG) from 9 muscles of dominant leg for both tasks and also across participants with different proficiency levels. The EMG signals were decomposed into MS and their respective activation coefficients using factor analysis (FA) in our study. The hip and joint angles were recorded using electrogoniometers to examine the kinematics for stability in relation to shared MS. Moreover, the perturbations from the task while slacklining were recorded using a triaxial accelerometer in Mediolateral (X), Anteroposterior (Y) and Vertical plane (Z). Research Significance: The study emphasizes on identifying neuromuscular strategies to avoid fall. The task-specific MS adaptation during slacklining is specific muscle co-activation pattern required for stability. Also, identification of proficiency-based synergies has provided neuromuscular strategies that could improve stability. This specific muscle co-activation pattern can be further used in physiotherapy and robotics to facilitate rehabilitation of neuromotor deficits. We found higher co-activation of quadriceps and hamstrings muscles in the shared synergy space that was in relation to higher hip and knee flexion (crouched gait). The activation of lower leg muscles showed higher activation while overground walking than slacklining due to a proper push off response. Moreover, regarding proficiency, an additional synergy emerged for proficient and non-proficient group. A higher knee flexion for proficient and a consistent knee flexion with its higher range of motion for novices were in relation to additional synergy.

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