title: Reliability of motor-evoked potentials during resting and active contraction conditions.
abstract: OBJECTIVE
  To determine the reliability of motor-evoked potentials (MEP) obtained using transcranial magnetic stimulation (TMS) in the first dorsal interosseous (FDI) and biceps brachii muscles.
  
  
  METHODS
  Fourteen college subjects attended the laboratory on three separate days. TMS was used to obtain MEP with the subject relaxed (resting condition) at stimulation intensities of 70%, 85%, and 100% of maximal stimulator output. MEP were also obtained during four active contraction conditions involving contractions of 25%, 50%, 75%, and 100% of maximal effort (MVC). Reliability was measured using an intraclass correlation analysis of variance (ANOVA) design.
  
  
  RESULTS
  In the resting condition, substantial increases in MEP amplitude were observed for both muscles from day 1 to day 2. Intraclass reliability estimates were higher for the biceps muscle (ICC = 0.95-0.99) than for the FDI muscle (ICC = 0.60-0.81). During the active conditions, the greatest MEP were observed at 25% and 50% MVC, with smaller MEP at 75% and 100% MVC. Intraclass correlations in the active condition were approximately 0.63-0.73.
  
  
  CONCLUSIONS
  : Moderate to good reliability of MEP amplitude in the biceps and FDI muscles can be obtained using TMS in both resting and active contraction conditions.
authors.affiliation: Department of Exercise Science, University of Massachusetts-Amherst, Amherst, MA 01003-9258, USA. kamen@excsci.umass.edu
authors.forename: Gary
authors.initials: G
authors.lastname: Kamen
mesh_terms: D000293:Adolescent; D000328:Adult; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology*; D014481:United States