An Experimental Investigation of the Discomfort of Arm Reaching Movements in a Seated Position

The majority of existing studies on arm reaching were either limited to the determination of reach envelopes or to motion analysis for understanding motion control strategies and/or their simulation. For ergonomic applications of digital humans, it is important to simulate motion and also to predict the discomfort felt by the virtual operator. Generic arm reaching movements in a seated position were studied in order to investigate the effects of age, gender and target position on motion and discomfort. The main results of discomfort analysis will be reported in the present paper.

The analysis of the discomfort ratings has shown that elderly subjects differed significantly from younger ones. The results showed that both target orientation plane and height had a quadratic effect on the discomfort. The minimum was located in the sagittal plane at the half height between the seat and shoulder. Discomfort increased almost linearly with the distance. Based on these observations, a regression model of discomfort prediction for reach movements was proposed. The reliability of discomfort evaluation using a rating scale was also discussed.