title: Intensity-dependent EMG response for the biceps brachii during sustained maximal and submaximal isometric contractions.
abstract: OBJECTIVE
  There have been recent attempts to characterize the mechanisms associated with fatigue-induced task failure. We compared the time to failure and the corresponding changes in the surface electromyogram (EMG) during sustained maximal and submaximal isometric force tasks.
  
  
  METHODS
  EMG activity was measured from the biceps brachii of 18 male participants as they sustained either a maximal or submaximal (60 % MVC) isometric contraction of the dominant elbow flexors until force could not be maintained above 55 % MVC.
  
  
  RESULTS
  Intensity-dependent patterns of change were observed for EMG amplitude and mean power frequency (MNF) between the two force tasks. Interestingly, the only significant predictor of failure time was the rate of change in EMG MNF during the submaximal task (r (2) = 0.304). In addition, EMG amplitude at submaximal failure was significantly lower (p < 0.05) than the values obtained during MVC.
  
  
  CONCLUSIONS
  The patterns of EMG response emphasize the basis of neuromuscular fatigue and task dependency. Additionally, our data suggest that the EMG MNF should be used when monitoring the progression of local muscle fatigue.
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, 1401 Asp Avenue, Room 104, Norman, OK, 73019, USA. jc.carr@ou.edu.
authors.forename: Joshua C
authors.initials: JC
authors.lastname: Carr
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, 1401 Asp Avenue, Room 104, Norman, OK, 73019, USA.
authors.forename: Travis W
authors.initials: TW
authors.lastname: Beck
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, 1401 Asp Avenue, Room 104, Norman, OK, 73019, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Ye
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, 1401 Asp Avenue, Room 104, Norman, OK, 73019, USA.
authors.forename: Nathan P
authors.initials: NP
authors.lastname: Wages
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Isometric; Neuromuscular fatigue; Surface electromyography; Task failure