Go to  Advanced Search

Postural threat-induced modulation of stretch reflex pathways in static and dynamic postural control

Show full item record

Files in this item

Files Size Format Description   View
ubc_2010_fall_horslen_brian.pdf 37.03Mb Adobe Portable Document Format   View/Open
 
Title: Postural threat-induced modulation of stretch reflex pathways in static and dynamic postural control
Author: Horslen, Brian Christopher
Degree Master of Science - MSc
Program Human Kinetics
Copyright Date: 2010
Publicly Available in cIRcle 2010-09-22
Abstract: There are clear changes to human static and dynamic postural control in situations of elevated postural threat (e.g. standing at the edge of an elevated platform). One possible explanation for these changes is that the amount of afferent information from muscle spindles in the ankle musculature is altered by postural threat. Two experiments have been conducted to explore postural threat-induced changes to soleus spinal stretch reflex function during static control of posture (Study 1), and in response to dynamic postural disturbances (Study 2). In Study 1, soleus Hoffmann (H-) and tendon stretch (T-) reflexes were used to explore changes in reflex amplitude while subjects stood quietly in conditions of low (ground level) and high (3.2m above ground) postural threat. Height-induced postural threat was associated with larger T-reflexes and higher arousal, these effects occurred without systematic changes in H-reflex amplitudes or background muscle activation. We interpret these findings as indirect evidence for arousal-mediated changes in muscle spindle sensitivity. In Study 2, emotionally-charged pictures were used to explore the effects of arousal on H- and T-reflexes, as well as whole body postural perturbations. The pictures failed to elicit significant changes in physiological arousal, H- or T-reflexes, or perturbation response parameters. However, the threat of postural perturbation caused parallel increases in T-reflexes, physiological arousal, and perceived anxiety. Therefore, we conclude that arousal-induced changes in stretch reflexes are not context specific, but rather a generalized response to postural threat. Furthermore, these results together provide substantial evidence in support of independent modulation of muscle spindle sensitivity in humans.
URI: http://hdl.handle.net/2429/28643
Scholarly Level: Graduate

This item appears in the following Collection(s)

Show full item record

All items in cIRcle are protected by copyright, with all rights reserved.

UBC Library
1961 East Mall
Vancouver, B.C.
Canada V6T 1Z1
Tel: 604-822-6375
Fax: 604-822-3893