Evaluation of the Manual Workload in Repetetive Wrist and Finger Motions

Abstract

The purpose of this study was to evaluate the manual workload on repetitive wrist and finger motions. To evaluate the manual workload, angular displacement of the joint, EMG of the muscle and subjective rating were studied. A screw-driving task was used for the wrist motion experiment. A keyboard-typing task was used for the finger motion experiment. Repetition rates of 0.5, 1, 2 motions per second were used with each task. As a result, manual workload increased with increasing repetitiveness. Peak spectral magnitude and frequency components corresponded closely with joint angular displacement amplitudes and repetition rates. Results of the correlation analysis showed that there were significant correlations among EMG, frequency-weighted filtering and subjective measurement. Both EMG and frequency-weighted filtering showed consistent workload estimation with increasing task frequency. Subjective ratings showed a slight over-estimation of the workload as the task frequency is increased.

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