University of Twente Student Theses


Effects of short-term body-weight support training on soleus motor unit behaviour

Millar, Alexandra (2023) Effects of short-term body-weight support training on soleus motor unit behaviour.

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Abstract:Gait impairment arises from a range of conditions, many of which fall under the umbrella of central nervous system injury. Central nervous system disorders are one of the largest contributors to disability worldwide and stem from a multitude of causes ranging from genetic disorders to traumatic injuries. A variety of treatment options exist for individuals with central nervous system disorders. These treatments can range from manual physiotherapy to gait training using robotic interventions such as body-weight support. Body-weight support is a rehabilitative tool that can support patients over a wide variety of tasks from simple treadmill walking to dynamic actions such as climbing stairs. While extensive research has been done to evaluate the physiological outcomes of body-weight support training, there is limited understanding of the underlying neurophysiological adaptations that drive these changes. The soleus stretch reflex is one window into the motor unit behaviour that drives gait and balance. By examining the effects of short-term body-weight support training on motor unit behaviour, further insights into the kinematic improvements of patients may be understood. In this study, the soleus short latency reflex response is selected as a method of evoking motor unit discharges. The reflex is evoked by administering approximately 80 dorsiflexion perturbations while the subject maintains 20% of their maximum voluntary contraction. This perturbation protocol is administered once as a baseline measurement and compared to recordings taken after training with the ZeroG body-weight support system at 40% gravity compensation and unassisted treadmill walking. Electromyography data is recorded using a high-density sensor grid during the perturbation protocols, and decomposed into motor unit innervation pulse trains using Convolution Kernel Compensation. Peri-stimulus time histograms and frequencygrams are used to extract the latency, amplitude, duration, and mean discharge rate of the short latency reflex from the decomposed motor unit data. A total of 99 motor units were pooled across subjects and recordings. No changes were found in the pooled data, however, an analysis of individual motor units tracked between recordings indicated that there may be an increase in latency after training with body-weight support. This limited but promising result suggests that the analysis of individual motor units may hold the keys to unlocking overarching motor unit behaviour.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Programme:Biomedical Engineering MSc (66226)
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