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Title: Locomotion and stance at height
Author: Tersteeg, Margaretha Cornelia Antonia
ISNI:       0000 0004 2724 307X
Awarding Body: Manchester Metropolitan University
Current Institution: Manchester Metropolitan University
Date of Award: 2012
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Postural threat induced by height affects the control of movement. The aim of this thesis was to develop a better understanding of the extent and the mechanisms through which postural threat can affect movement. The first study showed that a postural threat induced with a height of 80 cm (walkway width 22 cm) did not affect the gait pattern or arousal levels of young healthy adults. Whereas a height of 3.5 m did, an increase in arousal and a more cautious gait pattern compared to walking at ground level were observed. The influence of visual information was tested by occluding visual information of the drop when walking on a 3.5 m high walkway while retaining the danger. Occluding the visual information lead to reduced arousal but still a cautious gait pattern was observed which did not differ from walking at this height with the presence of visual information of the drop. So visually driven balance mechanisms were not the dominant cause of the gait adaptations observed at height (3.5 m). In a third study the walking task was repeated several times. While walking at a walkway raised 3.85 m off the ground a tendency to reduce the lateral centre of mass (COM) movement was observed. It was proposed that a minimizing lateral COM movement was prioritized. The thesis continued with two studies exploring the effect of cognitive factors on adaptations seen in conditions of postural threat. A one-leg stance task was performed repeatedly on various locations. Risk of the task, quantified by a simple model based on the constraint in recovery possibilities, could not explain the adaptations (increased co-contraction index, flexion of the stance leg and increased heart rate) to the one-leg stance task completely. A priori expectations of the task were shown to influence the one-leg stance task: anticipation and familiarization were observed in two separate studies. Furthermore, exposure (position further along the walkway) did influence the execution of the one-leg stance task. The final study of this thesis investigated the response to galvanic vestibular stimulation (GVS) during standing. GVS elicits a lateral body sway. The maximum lateral displacement of the body was significantly reduced while standing on a 3.85 m high walkway compared to standing on the ground. However the initial vestibular reflexes were unaffected. The results suggest that feed forward control did not influence the vestibular reflexes under postural threat.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available