title: Cross-education of muscular strength is facilitated by homeostatic plasticity.
abstract: OBJECTIVE
  We examined the effect of priming the ipsilateral motor cortex (M1) using anodal transcranial direct current stimulation (tDCS) prior to a single bout of strength training on the cross-transfer of strength and corticospinal excitability and inhibition of the ipsilateral M1.
  
  
  METHODS
  In a randomized double-blinded cross-over design, changes in strength and indices of corticospinal plasticity were analysed in 13 adults who were exposed to 20 min of ipsilateral anodal and sham tDCS (applied to the ipsilateral M1 to the training arm) followed by a single strength training session of the right Biceps Brachii only.
  
  
  RESULTS
  The induction of homeostatic plasticity via anodal tDCS priming, significantly increased strength of the untrained left Biceps Brachii (12%) compared to sham tDCS (2%), increased corticospinal excitability (12-33%) and cross-activation (25%) when ipsilateral anodal tDCS was applied to the right M1 prior to a single session of strength training. Interestingly, ipsilateral sham tDCS and strength training resulted in an average increase in MEP amplitude of 2-32%.
  
  
  CONCLUSIONS
  The novel findings of this study include: priming the ipsilateral M1 via anodal tDCS prior to a single bout of strength training augments the cross-transfer of strength which is manifested by an increase in corticospinal excitability and cross-activation. These findings provide insight into how priming methods that induce homeostatic plasticity may be used to enhance the cross-education phenomenon.
authors.affiliation: Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia. ashlyn.frazer@live.vu.edu.au.
authors.forename: Ashlyn K
authors.initials: AK
authors.lastname: Frazer
authors.affiliation: Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Williams
authors.affiliation: Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Spittle
authors.affiliation: Discipline of Exercise Science, School of Allied Health, La Trobe University, Melbourne, Australia.
authors.forename: Dawson J
authors.initials: DJ
authors.lastname: Kidgell
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006706:Homeostasis; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D009473:Neuronal Plasticity; D011712:Pyramidal Tracts / Q000502:physiology; D055070:Resistance Training / Q000379:methods*; D065908:Transcranial Direct Current Stimulation
keywords: Cross-education; Homeostatic plasticity; Priming; Strength training; Transcranial direct current stimulation