title: Agonist-antagonist common drive during fatiguing knee extension efforts using surface electromyography.
abstract: OBJECTIVE
  This study examined the electromyographic (EMG) activity of knee extensor agonists and a knee extensor antagonist muscle during fatiguing isometric extensions across a range of force levels.
  
  
  METHODS
  Five female subjects performed isometric knee extensions at 25%, 50%, 75% and 100% of their maximal voluntary contraction (MVC) with the knee flexed to 75 degrees. Surface EMG (SEMG) was recorded with bipolar electrodes from the vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF) and biceps femoris (BF) and the root-mean-squared (RMS) amplitude and the percentage frequency compression of these recordings were calculated. Commonality and cross talk between recordings were also examined.
  
  
  RESULTS
  Cross talk between recordings was deemed negligible despite significant levels of commonality between the agonist and antagonist SEMG, which was attributed to common drive. SEMG RMS amplitude increased significantly for all muscles during the 25%, 50%, 75% MVC knee extensions until task failure, and decreased significantly for 100% MVC. The frequency spectrum of the SEMG compressed significantly for all muscles and % MVC levels. The VM, VL and BF SEMG recordings responded similarly to fatigue. The RF's frequency spectrum compressed to a significantly higher degree.
  
  
  CONCLUSIONS
  The VM, VL, RF, and BF fatigue in parallel, with high similarity between VM, VL and BF, giving support to the concept of a shared agonist-antagonist motoneuron pool.
authors.affiliation: Department of Electronic and Electrical Engineering, University College Dublin, 4, Dublin, Ireland.
authors.forename: Hugh
authors.initials: H
authors.lastname: Mullany
authors.forename: Mark
authors.initials: M
authors.lastname: O'Malley
authors.forename: Alan
authors.initials: A
authors.lastname: St Clair Gibson
authors.forename: Christopher
authors.initials: C
authors.lastname: Vaughan
mesh_terms: D000328:Adult; D004566:Electrodes; D004576:Electromyography; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*