Faculty Collaboration Database

Spastic reflexes triggered by ankle load release in human spinal cord injury. J Neurophysiol 2006 Dec;96(6):2941-50

Date

07/21/2006

Pubmed ID

16855114

DOI

10.1152/jn.00186.2006

Scopus ID

2-s2.0-33751537682 (requires institutional sign-in at Scopus site)   19 Citations

Abstract

The rapid decrease in firing of load-sensitive group Ib muscle afferents during unloading may be particularly important in triggering the swing phase of gait. However, it still remains unclear whether load-sensitive muscle afferents modulate reflex activity in human spinal cord injury (SCI), as suggested by studies in the cat. The right hip of 12 individuals with chronic SCI was subjected to ramp (60 degrees /s) and hold (10 s) movements over a range from 40 degrees flexion to 0-10 degrees extension using a custom servomotor system. An ankle dorsiflexion load was imposed and released after the hip reached a targeted position using a custom-designed pneumatic motor system. Isometric joint torques of the hip and knee, reaction torque of the ankle, and surface electromyograms (EMGs) from eight muscles of the leg were recorded following the imposed hip movement and ankle load release. Reflexes, characterized by hip flexion torque, knee extension, and coactivation of ankle flexors and extensors, were triggered by ankle load release when the hip was in an extended position. The ankle load release was observed to enhance the reflexes triggered by hip extension itself, suggesting that ankle load afferents play an important role in spastic reflexes in human SCI and that the reflex pathways associated with ankle load afferents have important implications in the spinal reflex regulation of human movement. Such muscle behaviors emphasize the role of ankle load afferents and hip proprioceptors on locomotion. This knowledge may be especially helpful in the treatment of spasms and in identifying rehabilitation strategies for producing functional movements in human SCI.

Author List

Wu M, Schmit BD

Author

Brian Schmit PhD Professor in the Biomedical Engineering department at Marquette University

MESH terms used to index this publication - Major topics in bold

Adult
Aged
Algorithms
Ankle
Electromyography
Female
Hip
Humans
Interneurons
Locomotion
Male
Middle Aged
Movement
Muscle, Skeletal
Nerve Net
Physical Stimulation
Reflex
Spasm
Spinal Cord Injuries