title: Influence of joint position on synergistic muscle activity after fatigue of a single muscle head.
abstract: BACKGROUND
  We investigated synergistic muscle activity after fatigue of a single muscle in different joint positions.
  
  
  METHODS
  Two experimental groups (n = 12 each) performed maximal voluntary contractions (MVCs) before and after fatiguing the gastrocnemius lateralis (GL), using neuromuscular electrical stimulation (NMES). Neuromuscular tests, including muscle activity during MVC, H-reflex, and twitch interpolation, were performed. One group completed the experiment in a knee-extended position with the second group in a knee-flexed position.
  
  
  RESULTS
  In the knee-flexed position, the muscle activity increased in non-stimulated synergistic muscles. In contrast, in the knee-extended position, muscle activity of the synergistic muscles remained unaltered. The MVC force remained unaltered in the flexed position and decreased in the extended position.
  
  
  CONCLUSIONS
  Synergistic muscles compensate for the fatigued muscle in the flexed position but not in the extended position. Compensation mechanisms seem to depend on joint position.
authors.affiliation: Exercise Science, Institute of Sport and Movement Science, University of Stuttgart, Allmandring 28, 70569, Stuttgart, Germany; Exercise Science, Institute of Sport Science, Friedrich Schiller University Jena, Seidelstraße 20, 07749 Jena, Germany.
authors.forename: Norman
authors.initials: N
authors.lastname: Stutzig
authors.forename: Tobias
authors.initials: T
authors.lastname: Siebert
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000704:Analysis of Variance; D004558:Electric Stimulation; D004576:Electromyography; D006801:Humans; D007719:Knee Joint / Q000294:innervation*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D019415:Torque; D055815:Young Adult
keywords: H-reflex; compensation; interpolated twitch; neuromuscular electrical stimulation; spinal reflex; triceps surae