title: Effect of shoulder rotation, upper arm rotation and elbow flexion in a repetitive gripping task.
abstract: OBJECTIVE
  To investigate the effects of upper limb postures on discomfort score for repetitive gripping task.
  
  
  METHODS
  Eighteen right handed male participants volunteered in the experimental investigations.
  
  
  METHODS
  The present study was divided into two experiments. A Full factorial design of 2 (Two shoulder rotation angles) × 3 (Three elbow flexion angles) × 3 (Three upper arm rotation angles) was used. The effect of postures on MVC grip strength, Grip endurance and on discomfort score, for a repetitive task at 150 N ± 5 N with exertions 15 per minute was recorded. In a supplementary experiment, the EMG recordings were also taken for validating the effect of elbow flexion angle.
  
  
  RESULTS
  ANOVA showed that the main effects of postures were not significant on MVC grip, except elbow flexion (p < 0.001). The endurance time was also significant (p=0.0100) for elbow flexion and there was no effect of other postures. The second experiment showed that the effect of shoulder rotation, elbow flexion and forearm rotation was significant (p <0.001) on discomfort score. The EMG activity of the muscles also showed that FDP and ECRB muscles had maximum reduction in median frequencies of the EMG signals of the respective muscles at 45° elbow flexion angle.
  
  
  CONCLUSIONS
  The main effects of elbow flexion angle, shoulder rotation and forearm rotation were significant on discomfort score for the repetitive gripping task of the present study.
authors.affiliation: Department of Mechanical Engineering, Aligarh Muslim University, Aligarh, UP, India.
authors.forename: Mohd
authors.initials: M
authors.lastname: Farooq
authors.forename: Abid Ali
authors.initials: AA
authors.lastname: Khan
mesh_terms: D000328:Adult; D004551:Elbow Joint / Q000502:physiology*; D004576:Electromyography; D005542:Forearm / Q000502:physiology; D018737:Hand Strength; D006801:Humans; D008297:Male; D010147:Pain Measurement; D011187:Posture; D016059:Range of Motion, Articular / Q000502:physiology*; D012782:Shoulder / Q000502:physiology*; D013647:Task Performance and Analysis; D055815:Young Adult