title: Reproducibility of transcranial magnetic stimulation metrics in the study of proximal upper limb muscles.
abstract: OBJECTIVE
  Reproducibility of transcranial magnetic stimulation (TMS) metrics is essential in accurately tracking recovery and disease. However, majority of evidence pertains to reproducibility of metrics for distal upper limb muscles. We investigate for the first time, reliability of corticospinal physiology for a large proximal muscle - the biceps brachii and relate how varying statistical analyses can influence interpretations.
  
  
  METHODS
  14 young right-handed healthy participants completed two sessions assessing resting motor threshold (RMT), motor evoked potentials (MEPs), motor map and intra-cortical inhibition (ICI) from the left biceps brachii. Analyses included paired t-tests, Pearson's, intra-class (ICC) and concordance correlation coefficients (CCC) and Bland-Altman plots.
  
  
  RESULTS
  Unlike paired t-tests, ICC, CCC and Pearson's were >0.6 indicating good reliability for RMTs, MEP intensities and locations of map; however values were <0.3 for MEP responses and ICI.
  
  
  CONCLUSIONS
  Corticospinal physiology, defining excitability and output in terms of intensity of the TMS device, and spatial loci are the most reliable metrics for the biceps. MEPs and variables based on MEPs are less reliable since biceps receives fewer cortico-motor-neuronal projections. Statistical tests of agreement and associations are more powerful reliability indices than inferential tests.
  
  
  CONCLUSIONS
  Reliable metrics of proximal muscles when translated to a larger number of participants would serve to sensitively track and prognosticate function in neurological disorders such as stroke where proximal recovery precedes distal.
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States.
authors.forename: Vishwanath
authors.initials: V
authors.lastname: Sankarasubramanian
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Roelle
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States.
authors.forename: Corin E
authors.initials: CE
authors.lastname: Bonnett
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Janini
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Varnerin
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Cunningham
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Sharma
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States.
authors.forename: Kelsey A
authors.initials: KA
authors.lastname: Potter-Baker
authors.affiliation: Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, OH, United States.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Wang
authors.affiliation: Human Performance and Engineering Research, Kessler Foundation, West Orange, NJ, United States.
authors.forename: Guang H
authors.initials: GH
authors.lastname: Yue
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States; Department of Physical Medicine and Rehabilitation, Cleveland Clinic, Cleveland, OH, United States; Center for Neurological Restoration, Cleveland Clinic, Cleveland, OH, United States. Electronic address: plowe2@ccf.org.
authors.forename: Ela B
authors.initials: EB
authors.lastname: Plow
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D004576:Electromyography / Q000379:methods* / Q000592:standards; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D015203:Reproducibility of Results; D050781:Transcranial Magnetic Stimulation / Q000379:methods* / Q000592:standards
keywords: Corticospinal; Motor evoked potential; Primary motor cortex; Proximal muscles; Reliability; Transcranial magnetic stimulation