Effect of shoulder rotation, upper arm rotation and elbow flexion in a repetitive gripping task

Abstract

To investigate the effects of upper limb postures on discomfort score for repetitive gripping task. Eighteen right handed male participants volunteered in the experimental investigations. 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. 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. 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.