title: Effect of antispastic drugs on motor reflexes and voluntary muscle contraction in incomplete spinal cord injury.
abstract: OBJECTIVE
  To investigate the effects of antispastic drugs baclofen and tizanidine on reflexes and volitional tasks.
  
  
  METHODS
  Double-blind, placebo-controlled, crossover, before-after trial, pilot study.
  
  
  METHODS
  Research laboratory in a rehabilitation hospital.
  
  
  METHODS
  Men with chronic (>6mo) motor incomplete spinal cord injury (N=10) were recruited for the study.
  
  
  METHODS
  Tizanidine, baclofen, and placebo were tested in this study. Agents were tested in separate experimental sessions separated by >1 week.
  
  
  METHODS
  Reflex and strength were measured before and after the administration of a single dose of each intervention agent. Electromyographic and joint torque data were collected during assessments of plantar flexor stretch reflexes, maximum contraction during motor-assisted isokinetic movements, and maximum isometric knee extension and flexion.
  
  
  RESULTS
  Reduced stretch reflex activity was observed after the administration of either tizanidine or baclofen. We observed that tizanidine had a stronger inhibitory effect on knee extensors and plantar flexors whereas baclofen had a stronger inhibitory effect on the knee flexors. The effects of these drugs on strength during isometric and isokinetic tasks varied across participants, without a consistent reduction in torque output despite decreased electromyographic activity.
  
  
  CONCLUSIONS
  These results suggest that antispastic drugs are effective in reducing stretch reflexes without substantially reducing volitional torque. Differential effects of tizanidine and baclofen on reflexes of flexors and extensors warrant further investigation into patient-specific management of antispastic drugs.
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL. Electronic address: vchu@ric.org.
authors.forename: Virginia Way Tong
authors.initials: VW
authors.lastname: Chu
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL; Department of Physical Therapy, University of Illinois at Chicago, Chicago, IL.
authors.forename: Thomas George
authors.initials: TG
authors.lastname: Hornby
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL; Department of Biomedical Engineering, Marquette University, Milwaukee, WI.
authors.forename: Brian David
authors.initials: BD
authors.lastname: Schmit
mesh_terms: D000328:Adult; D001418:Baclofen / Q000494:pharmacology; D003000:Clonidine / Q000031:analogs & derivatives / Q000494:pharmacology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction / Q000187:drug effects* / Q000502:physiology; D035002:Lower Extremity / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009125:Muscle Relaxants, Central / Q000494:pharmacology*; D053580:Muscle Strength / Q000187:drug effects / Q000502:physiology; D010865:Pilot Projects; D012026:Reflex, Stretch / Q000187:drug effects* / Q000502:physiology; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D019415:Torque
chemical_list: D009125:Muscle Relaxants, Central; C023754:tizanidine; D001418:Baclofen; D003000:Clonidine
keywords: Muscle spasticity; Muscle strength; Reflex, stretch; Rehabilitation; Spinal cord injuries