Evaluating posture behavior during seated tasks

Abstract

A method was developed to evaluate posture behavior of the trunk, neck, eye, and upper extremity in three-dimensional space during the performance of static, seated tasks. Body postures were measured using an ultrasonic measurement system to determine the Cartesian coordinates of joints and the angles between adjacent limbs. Posture preferences for a variety of visual and manual tasks were then determined.Pilot studies using three subjects performing visual and right-handed tasks showed that the postures were affected by target location, body size, and target size. These experiments suggest that the preferred horizontal location of visual targets is within 10[deg] of the sagittal plane of the head. The preferred vertical location of visual targets is 10[deg] to 35[deg] below the seated eye height. For manual reaches, the target-to-shoulder distance should be at least one-third the length of the upper extremity to avoid extreme elbow flexion. In addition, the seat pan should swivel and should allow a person to move fore and aft in order to adjust to a comfortable work posture.