Experimental Brain Research

, Volume 165, Issue 4, pp 422–434

Identification of intrinsic and reflex ankle stiffness components in stroke patients

Research Article

DOI: 10.1007/s00221-005-2320-z

Cite this article as:
Galiana, L., Fung, J. & Kearney, R. Exp Brain Res (2005) 165: 422. doi:10.1007/s00221-005-2320-z

Abstract

Reflex and intrinsic contributions to ankle stiffness were examined in 11 stroke patients with clinical evidence of ankle spasticity and nine gender-matched and age-matched controls. Subjects lay supine with one foot placed in a custom-fitted boot attached to an electro-hydraulic actuator. They were instructed to relax while pseudo-random binary sequence perturbations were applied to their ankle joint. The ankle position and torque, as well as EMG from the ankle dorsiflexors and plantarflexors were recorded. These were used to identify reflex and intrinsic components of ankle stiffness, using a non-linear, parallel-cascade, system identification method. Results demonstrated that the majority of stroke patients (7/11) had ankle stiffness similar to that of control subjects. In contrast, a minority of stroke patients (4/11) had an abnormal increase in ankle stiffness, most of which could be attributed to an increased reflex gain. Reflex stiffness increased as the ankle was dorsiflexed in all subjects. These results differ from a previous study showing that reflex gain and intrinsic stiffness were increased in all patients with spinal cord injury. This difference may reflect the different topography of the lesions in the two neurological conditions.

Keywords

Stroke Spasticity System identification Reflex Stiffness Ankle Intrinsic properties 

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Jewish Rehabilitation Hospital Research Center (Research site of CRIR)LavalCanada
  2. 2.School of Physical and Occupational TherapyMontrealCanada
  3. 3.Department of Biomedical EngineeringMcGill UniversityMontrealCanada