title: The effects of long-term FES-assisted walking on intrinsic and reflex dynamic stiffness in spastic spinal-cord-injured subjects.
abstract: The effects of long-term functional electrical stimulation (FES)-assisted walking on ankle dynamic stiffness were examined in spinal cord-injured (SCI) subjects with incomplete motor function loss. A parallel-cascade system identification method was used to identify intrinsic and reflex contributions to dynamic ankle stiffness at different ankle positions while subjects remained relaxed. Intrinsic stiffness dynamics were well modeled by a linear second-order model relating intrinsic torque to joint position. Reflex stiffness dynamics were accurately described by a linear third-order model relating halfwave rectified velocity to reflex torque. We examined four SCI subjects before and after long-term FES-assisted walking (> 16 mo). Another SCI subject, who used FES for only five months was examined 12 mo latter to serve as a non-FES, SCI control. Reflex stiffness decreased in FES subjects by an average of 53% following FES-assisted walking, intrinsic stiffness also dropped by 45%. In contrast, both reflex and intrinsic stiffness increased in the non-FES, SCI control. These findings suggest that FES-assisted walking may have therapeutic effects, helping to reduce abnormal joint stiffness.
authors.affiliation: Department of Biomedical Engineering, McGill University, Montreal, QC H3A 2B4, Canada.
authors.forename: Mehdi M
authors.initials: MM
authors.lastname: Mirbagheri
authors.forename: Michel
authors.initials: M
authors.lastname: Ladouceur
authors.forename: Hugues
authors.initials: H
authors.lastname: Barbeau
authors.forename: Robert E
authors.initials: RE
authors.lastname: Kearney
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000503:physiopathology*; D002574:Cervical Vertebrae / Q000293:injuries; D002908:Chronic Disease; D004548:Elasticity; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D020233:Gait Disorders, Neurologic / Q000209:etiology / Q000503:physiopathology / Q000534:rehabilitation*; D006801:Humans; D008137:Longitudinal Studies; D008159:Lumbar Vertebrae / Q000293:injuries; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009128:Muscle Spasticity / Q000209:etiology / Q000503:physiopathology / Q000534:rehabilitation*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D016059:Range of Motion, Articular; D012026:Reflex, Stretch; D012680:Sensitivity and Specificity; D013119:Spinal Cord Injuries / Q000150:complications / Q000503:physiopathology / Q000534:rehabilitation*; D013314:Stress, Mechanical; D013904:Thoracic Vertebrae / Q000293:injuries; D019415:Torque; D016896:Treatment Outcome; D016138:Walking