title: The acute effects of local muscle vibration frequency on peak torque, rate of torque development, and EMG activity.
abstract: OBJECTIVE
  Vibratory stimuli enhance muscle activity and may be used for rehabilitation and performance enhancement. Efficacy of vibration varies with the frequency of stimulation, but the optimal frequency is unclear. The purpose of this study was to examine the effects of 30 Hz and 60 Hz local muscle vibration (LMV) on quadriceps function.
  
  
  METHODS
  Twenty healthy volunteers (age = 20.4 ± 1.4 years, mass = 68.1 ± 11.0 kg, height = 170.1 ± 8.8 cm, males = 9) participated. Isometric knee extensor peak torque (PT), rate of torque development (RTD), and electromyography (EMG) of the quadriceps were assessed followed by one of the three LMV treatments (30 Hz, 60 Hz, control) applied under voluntary contraction, and again immediately, 5, 15, and 30 min post-treatment in three counterbalanced sessions. Dependent variables were analyzed using condition by time repeated-measures ANOVA.
  
  
  RESULTS
  The condition × time interaction was significant for EMG amplitude (p = 0.001), but not for PT (p=0.324) or RTD (p = 0.425). The increase in EMG amplitude following 30 Hz LMV was significantly greater than 60 Hz LMV and control.
  
  
  CONCLUSIONS
  These findings suggest that 30 Hz LMV may elicit an improvement in quadriceps activation and could be used to treat quadriceps dysfunction resulting from knee pathologies.
authors.affiliation: Neuromuscular Research Laboratory, University of North Carolina at Chapel Hill, USA; Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, USA; Curriculum in Human Movement Science, University of North Carolina at Chapel Hill, USA.
authors.forename: Derek N
authors.initials: DN
authors.lastname: Pamukoff
authors.affiliation: Neuromuscular Research Laboratory, University of North Carolina at Chapel Hill, USA; Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, USA; Curriculum in Human Movement Science, University of North Carolina at Chapel Hill, USA.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Ryan
authors.affiliation: Neuromuscular Research Laboratory, University of North Carolina at Chapel Hill, USA; Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, USA; Curriculum in Human Movement Science, University of North Carolina at Chapel Hill, USA. Electronic address: troyb@unc.edu.
authors.forename: J Troy
authors.initials: JT
authors.lastname: Blackburn
mesh_terms: D004576:Electromyography / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology*; D008297:Male; D026741:Physical Therapy Modalities / Q000295:instrumentation; D052097:Quadriceps Muscle / Q000502:physiology*; D013997:Time Factors; D019415:Torque; D014732:Vibration; D055815:Young Adult
keywords: Electromyography; Neuromuscular; Quadriceps; Vibration