title: Shoulder muscle activation and fatigue during a controlled forceful hand grip task.
abstract: OBJECTIVE
  Reliable electromyographic evaluation of the shoulder in common painful conditions is a major challenge due to a reduced range of movement and pain-related muscle inhibition. This study investigates the use of a hand grip task for the assessment of shoulder muscle activation.
  
  
  METHODS
  Muscle activity and fatigue for supraspinatus and infraspinatus muscles were measured in 16 healthy controls using fine-wire electrodes during a controlled gripping task at 50% of maximum voluntary contraction, in a standardized sitting and arm position. Changes in muscle activity and fatigue were measured by the time-slope of root mean square amplitude and median frequency, respectively.
  
  
  RESULTS
  A significant positive amplitude slope (p<0.01) was found for both supraspinatus and infraspinatus, indicating that the task resulted in increasing muscle activity. Judging by the median frequency slope, there was no sign of fatigue progression.
  
  
  CONCLUSIONS
  A standardized hand grip task in a neutral position activates key rotator cuff muscles. This might provide a method for electromyographic assessment of shoulder girdle muscles which avoids problems due to pain-related limitation of movement, and might be useful in the development and monitoring of shoulder rehabilitation strategies.
authors: Musculoskeletal Science Research Group, Institute of Translational Medicine, University of Liverpool, Liverpool, UK. omid@liv.ac.uk
authors: O
authors: O
authors: Alizadehkhaiyat
authors: A C
authors: AC
authors: Fisher
authors: G J
authors: GJ
authors: Kemp
authors: Karthik
authors: K
authors: Vishwanathan
authors: S P
authors: SP
authors: Frostick
mesh_terms: D000328:Adult; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*