title: Vastus medialis and lateralis activity during voluntary and stimulated contractions.
abstract: BACKGROUND
  The purpose of this study was to investigate the relative activation of vastus medialis (VM) and vastus lateralis (VL) muscles during voluntary and stimulated isometric contractions at different joint angles.
  
  
  METHODS
  Sixteen healthy men (mean age: 26 years) completed maximal voluntary and stimulated contractions of the knee extensor muscles at 30°, 65°, and 100° of knee flexion. VM/VL ratios were calculated from voluntary electromyographic (EMG) and evoked torque recordings.
  
  
  RESULTS
  Both EMG and VM/VL torque ratios were significantly lower at 30° than at 100° of knee flexion (P < 0.05).
  
  
  CONCLUSIONS
  These results can be explained by the relatively small contribution of the VM muscle to knee extension torque at short muscle length. Such disadvantage of the VM muscle at extended knee positions does not seem to be compensated by an increased neural drive. Muscle Nerve 56: 968-974, 2017.
authors.affiliation: Human Performance Lab, Schulthess Clinic, Lengghalde 2, 8008, Zurich, Switzerland.
authors.forename: Rosa M S
authors.initials: RMS
authors.lastname: Visscher
authors.affiliation: Human Performance Lab, Schulthess Clinic, Lengghalde 2, 8008, Zurich, Switzerland.
authors.forename: Diego
authors.initials: D
authors.lastname: Rossi
authors.affiliation: Human Performance Lab, Schulthess Clinic, Lengghalde 2, 8008, Zurich, Switzerland.
authors.forename: Bernd
authors.initials: B
authors.lastname: Friesenbichler
authors.affiliation: Sport Physical Therapy, Schulthess Clinic, Zurich, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Dohm-Acker
authors.affiliation: Sport Physical Therapy, Schulthess Clinic, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Rosenheck
authors.affiliation: Human Performance Lab, Schulthess Clinic, Lengghalde 2, 8008, Zurich, Switzerland.
authors.forename: Nicola A
authors.initials: NA
authors.lastname: Maffiuletti
mesh_terms: D000328:Adult; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007719:Knee Joint / Q000294:innervation / Q000502:physiology*; D008297:Male; D052097:Quadriceps Muscle / Q000502:physiology*; D016059:Range of Motion, Articular; D018709:Statistics, Nonparametric; D019415:Torque; D004561:Transcutaneous Electric Nerve Stimulation
keywords: electrical stimulation; electromyography; knee angle; neural activation; quadriceps; twitch torque