title: Changes in corticospinal transmission following 8weeks of ankle joint immobilization.
abstract: OBJECTIVE
  Joint immobilization has previously been shown to modulate corticospinal excitability. The present study investigated changes in the excitability of distinct fractions of the corticospinal pathway by means of conditioning the H-reflex with transcranial magnetic stimulation (TMS) of the primary motor cortex (Hcond). This method allows assessment of transmission in fast (monosynaptic) and slow(er) (polysynaptic) corticospinal pathways.
  
  
  METHODS
  9 subjects underwent 8weeks of unilateral ankle joint immobilization during daytime, 7 subjects served as controls. The measures obtained before and after immobilization included stretch- and H-reflexes assessing excitability of the spinal reflex circuitries, TMS recruitment curves estimating overall changes in corticospinal excitability, and Hcond.
  
  
  RESULTS
  TMS recruitment curves showed an overall increase in corticospinal excitability following immobilization. Importantly, Hcond revealed significant facilitation of conditioned reflexes, but only for longer conditioning intervals, suggesting that immobilization increased excitability only of slower, indirect corticospinal pathways. No changes were observed in the control group. Immobilization had no significant effects on spinal reflex measures.
  
  
  CONCLUSIONS
  8weeks of ankle joint immobilization was accompanied by pathway-specific modulation of corticospinal transmission.
  
  
  CONCLUSIONS
  It is particularly interesting that fast corticospinal projections were unaffected as these are involved in controlling many, if not most, movements in humans.
authors.affiliation: Department of Medicine, Movement and Sport Science, University of Fribourg, Switzerland. Electronic address: christian.leukel@unifr.ch.
authors.forename: Christian
authors.initials: C
authors.lastname: Leukel
authors.affiliation: Department of Medicine, Movement and Sport Science, University of Fribourg, Switzerland.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Taube
authors.affiliation: German Aerospace Centre, Institute of Aerospace Medicine, Division Space Physiology, Cologne, Germany.
authors.forename: Jörn
authors.initials: J
authors.lastname: Rittweger
authors.affiliation: Department of Sport Science, University of Freiburg, Germany.
authors.forename: Albert
authors.initials: A
authors.lastname: Gollhofer
authors.affiliation: German Aerospace Centre, Institute of Aerospace Medicine, Division Space Physiology, Cologne, Germany.
authors.forename: Michel
authors.initials: M
authors.lastname: Ducos
authors.affiliation: German Aerospace Centre, Institute of Aerospace Medicine, Division Space Physiology, Cologne, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Weber
authors.affiliation: Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark; Department of Neuroscience and Pharmacology, University of Copenhagen, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Lundbye-Jensen
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000502:physiology*; D019054:Evoked Potentials, Motor / Q000502:physiology; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D011712:Pyramidal Tracts / Q000502:physiology*; D012149:Restraint, Physical / Q000379:methods; D009435:Synaptic Transmission / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods
keywords: H-reflex conditioning; MEP recruitment; Motor evoked potential; Primary motor cortex; Spinal cord; Transcranial magnetic stimulation