title: Reduced cortical voluntary activation during bilateral knee extension.
abstract: BACKGROUND
  Reduced neural drive is mainly thought to explain the bilateral deficit phenomenon, i.e. the difference in maximal isometric voluntary contraction (MVC) between unilateral and bilateral contractions. The aim of the present study was to further document if bilateral knee extension is associated with changes in voluntary activation level assessed by both peripheral nerve electrical stimulation and transcranial magnetic stimulation.
  
  
  METHODS
  Fourteen subjects performed unilateral and bilateral knee extensions with both superimposed femoral electrical nerve stimulation and transcranial magnetic stimulation in order to assess voluntary activation (VAFNES) and cortical voluntary activation (VATMS), respectively.
  
  
  RESULTS
  There was no difference in MVC force of the tested leg when involved in unilateral and bilateral knee extensions (p=0.87). However, a significantly reduced VAFNES(-2.1±2.4%; p=0.01) and VATMS(-1.6±2.7%; p=0.04) have been evidenced during bilateral knee extension.
  
  
  CONCLUSIONS
  It is hypothesized that counterbalances could have masked the decrease of voluntary activation during bilateral contraction.
authors.affiliation: Univ Lyon, UJM-Saint-Etienne, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F-42023 Saint-Etienne, France.
authors.forename: Luc
authors.initials: L
authors.lastname: Girompaire
authors.affiliation: Univ Lyon, UJM-Saint-Etienne, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F-42023 Saint-Etienne, France; Université du Maine, Laboratoire ≪Motricité, Interaction, Performance≫ EA4334, UFR Sciences et Technique, Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France.
authors.forename: Baptiste
authors.initials: B
authors.lastname: Morel
authors.affiliation: Univ Lyon, UJM-Saint-Etienne, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F-42023 Saint-Etienne, France. Electronic address: thomas.lapole@univ-st-etienne.fr.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lapole
mesh_terms: D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D005267:Femoral Nerve / Q000502:physiology; D007839:Functional Laterality; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007717:Knee / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: Antagonist co-activation; Bilateral deficit; Femoral nerve electrical stimulation; Knee extension; Transcranial magnetic stimulation; Voluntary activation