title: Corticomotor excitability of arm muscles modulates according to static position and orientation of the upper limb.
abstract: OBJECTIVE
  We investigated how multi-joint changes in static upper limb posture impact the corticomotor excitability of the posterior deltoid (PD) and biceps brachii (BIC), and evaluated whether postural variations in excitability related directly to changes in target muscle length.
  
  
  METHODS
  The amplitude of individual motor evoked potentials (MEPs) was evaluated in each of thirteen different static postures. Four functional postures were investigated that varied in shoulder and elbow angle, while the forearm was positioned in each of three orientations. Posture-related changes in muscle lengths were assessed using a biomechanical arm model. Additionally, M-waves were evoked in the BIC in each of three forearm orientations to assess the impact of posture on recorded signal characteristics.
  
  
  RESULTS
  BIC-MEP amplitudes were altered by shoulder and elbow posture, and demonstrated robust changes according to forearm orientation. Observed changes in BIC-MEP amplitudes exceeded those of the M-waves. PD-MEP amplitudes changed predominantly with shoulder posture, but were not completely independent of influence from forearm orientation.
  
  
  CONCLUSIONS
  Results provide evidence that overall corticomotor excitability can be modulated according to multi-joint upper limb posture.
  
  
  CONCLUSIONS
  The ability to alter motor pathway excitability using static limb posture suggests the importance of posture selection during rehabilitation aimed at retraining individual muscle recruitment and/or overall coordination patterns.
authors.affiliation: Environment and Ergonomics Research Group, Autodesk Research, Toronto, ON, Canada; Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA; Department of Physical Medicine & Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Jeremy P M
authors.initials: JP
authors.lastname: Mogk
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA; Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Lynn M
authors.initials: LM
authors.lastname: Rogers
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA; Department of Physical Medicine & Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, IL, USA; Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA; Edward Hines, Jr. VA Hospital, Hines, IL, USA. Electronic address: w-murray@northwestern.edu.
authors.forename: Wendy M
authors.initials: WM
authors.lastname: Murray
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA; Department of Physical Medicine & Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, IL, USA; Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Perreault
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA; Department of Physical Medicine & Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, IL, USA; Department of Sport & Exercise Science, University of Auckland, Auckland, New Zealand.
authors.forename: James W
authors.initials: JW
authors.lastname: Stinear
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D057645:Deltoid Muscle / Q000502:physiology; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009138:Musculocutaneous Nerve / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011712:Pyramidal Tracts; D050781:Transcranial Magnetic Stimulation; D004561:Transcutaneous Electric Nerve Stimulation; D034941:Upper Extremity / Q000294:innervation / Q000502:physiology*; D055815:Young Adult
keywords: Corticomotor excitability; Peripheral nerve stimulation; Tendon transfer; Transcranial magnetic stimulation; Upper extremity; Upper limb posture