title: The effect of grip force, stroke rotation and frequency on discomfort for a torqueing tasks.
abstract: BACKGROUND
  Occupational tasks involve awkward upper limb postures, especially movement of forearm with repetitive combined gripping and torqueing exertions, which may lead to development of WMSDs. From the literature survey it was observed that there was a lack of studies focussed on the combined effect of torque and grip exertions on forearm discomfort.
  
  
  OBJECTIVE
  The present study was to investigate the effects of grip force, stroke rotation and frequency of exertions on discomfort and Electromyography (EMG) activities of the forearm muscles in a repetitive torqueing task.
  
  
  METHODS
  Twenty-seven male participants volunteered in this study. The participants performed repetitive exertions for a 5 minutes duration for each combination of the different levels of stroke rotation, grip force and frequency of exertions. Three levels of stroke rotation, three levels of grip force and three levels of frequency of exertion were chosen as independent variables. Therefore a 3 × 3 customized factorial design was used for the experiment for each level of grip force. Hence, the study was divided into three groups on the basis of grip force (50N, 70N and 90N).
  
  
  RESULTS
  The ANOVA showed that stroke rotation and frequency of exertion were significant on discomfort. Further Students Newmann test (SNK) revealed that discomfort was increased with increasing stroke rotation and frequency of exertion. The multivariate analysis of variances (MANOVA) performed on EMG data instead of ANOVA because EMG activities of five muscles simultaneously were recorded. The Results found that extensor muscles were more fatigued in torqueing with gripping task.
  
  
  CONCLUSIONS
  It was found that stroke rotation for the torqueing tasks must be kept below 45°. It was concluded that it is important to control stroke rotation to improve performance of repetitive torqueing activity.
authors.affiliation: Department of Industrial Engineering, King Abdul Aziz University, Jeddah, KSA.
authors.forename: Farheen
authors.initials: F
authors.lastname: Bano
authors.affiliation: Department of Mechanical Engineering, Jamia Millia Islamia, New Delhi, India.
authors.forename: Zulqernian
authors.initials: Z
authors.lastname: Mallick
authors.affiliation: Department of Mechanical Engineering, Jamia Millia Islamia, New Delhi, India.
authors.forename: Abid Ali
authors.initials: AA
authors.lastname: Khan
mesh_terms: D004551:Elbow Joint / Q000503:physiopathology*; D004576:Electromyography; D005542:Forearm / Q000503:physiopathology*; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000502:physiology*; D059352:Musculoskeletal Pain / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D010147:Pain Measurement; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D013647:Task Performance and Analysis; D019415:Torque
keywords: Discomfort; grip force; muscle fatigue; repetitive torqueing exertion; stroke rotation