Affiliations: Department of Mechanical Engineering, Aligarh Muslim
University, Aligarh, UP, India | Ergonomics Research Division, Department of Mechanical
Engineering, Aligarh Muslim University, Aligarh, UP, India
Note: [] Address for correspondence: Abid Ali Khan, Ergonomics Research
Division, Department of Mechanical Engineering, Aligarh Muslim University,
Aligarh, UP, India. Tel.: +91 9837111865; E-mail: abida.khan@amu.ac.in
Abstract: Objectives: To investigate the effects of upper limb postures on
discomfort score for repetitive gripping task. Participants: Eighteen right handed male participants volunteered in
the experimental investigations. Method: 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.
Keywords: MVC grip strength, grip endurance time, EMG activities
