Date of Award

Spring 2007

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Biomedical Engineering

First Advisor

Schmit, Brian

Second Advisor

Schindler-Ivens, Sheila

Third Advisor

Winters, Jack


In human spinal cord injury (SCI), hip-triggered reflexes are associated with organized interneuronal spinal networks, and it has been suggested that these spastic reflex pathways incorporate interneuronal circuitry involved with spinal control of locomotion (Schmit and Benz 2002; Steldt and Schmit 2004). To determine if spastic reflex pathways overlap with spinal circuits involved with locomotion, we investigated the effects of afferent input from the contralateral hip on spastic reflex activity in eleven chronic SCI study participants. A novel servomotor drive system was constructed to impose bilateral hip oscillations while the knees and ankles were held in an isometric position using instrumented leg braces. Surface electromyograms (EMGs) and joint torques were recorded during the imposed hip oscillations. Tests were conducted at two different frequencies to test for velocity-dependence of the reflexes and the following four tests were used to examine the effects of contralateral hip afferent feedback on spastic reflexes: (1) bilateral alternating, (2) bilateral synchronous, (3) unilateral leg oscillation with the contralateral leg held stationary in hip extension, and (4) unilateral leg oscillation with the contralateral leg held stationary in hip flexion. The response to bilateral alternating movements resulted in an increase in the reflex magnitude compared to the bilateral synchronous movements. Unilateral leg perturbations yielded reflex patterns that were consistent with the reflex patterns observed during alternating and synchronous hip oscillations. These observations suggest that spastic reflex excitability is modulated through afferent input from the contralateral hip, and further suggest that spastic reflexes in human SCI may be linked with spinal locomotor networks.



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