title: Strength training of one limb increases corticomotor excitability projecting to the contralateral homologous limb.
abstract: The contralateral transfer of strength following unilateral strength training (ULS) is thought to be due to changes within the nervous system. Using transcranial magnetic stimulation (TMS) we compared corticospinal responses following ULS of the right biceps brachii (BB) projecting to the untrained left BB. Motor evoked potentials (MEPs) were recorded from both BB of 23 individuals pre and post 4 weeks heavy load (80% of 1RM) ULS of right BB. TMS was delivered at intensities below active motor threshold (AMT) to saturation of the MEP (MEPmax). ULS resulted in a 28% increase in 1RM right BB strength, resulting in a 19.2% increase in contralateral strength of the left BB (p = .0001). There was a significant increase in MEP amplitude of 30.3% (p = .03), 33% (p = .05), and 26.5% (p = .01) at AMT, 20% above AMT and MEPmax respectively. No significant differences in silent period were seen at AMT, 20% above AMT or MEPmax. This study has demonstrated increased corticospinal excitability projecting to the untrained arm following heavy load ULS.
authors.affiliation: Centre for Physical Activity and Nutrition Research, Deakin University, Australia.
authors.forename: Dawson J
authors.initials: DJ
authors.lastname: Kidgell
authors.forename: Mark A
authors.initials: MA
authors.lastname: Stokes
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Pearce
mesh_terms: D000293:Adolescent; D000328:Adult; D001132:Arm / Q000294:innervation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation*; D009473:Neuronal Plasticity / Q000502:physiology; D011712:Pyramidal Tracts / Q000502:physiology*; D055070:Resistance Training; D050781:Transcranial Magnetic Stimulation; D014163:Transfer, Psychology / Q000502:physiology*; D055815:Young Adult