An Evaluation of Postural Motions, Chair Motions, and Contact in Four Office Seats

Abstract

The goal of this study was to use biomechanical procedures and models to measure people and office chairs in terms of fit, movement, and support during changes in recline and spinal curvature. Testing was performed with four office chairs in a simulated keyboarding workspace with fourteen subjects ranging from petite, light women to tall, heavy men. Postures, body motions and chair motions were measured with a video-based system. A Lordosimeter measured changes in lumbar spinal curvature. Torso positions relative to the keyboard and desktop were evaluated for changes in recline angle and lumbar curvature. Pressure distributions were measured on the back of the chairs and related to changes in torso posture (back inclination and lumbar curvature). Based on the contact areas between the subject's back and the seat back, the amount of support was evaluated for changes in recline angle and lumbar curvature. Chair D, the LEAP chair had the best overall performance. LEAP was found to move with people as they moved their spine from flexion to extension. During recline motions LEAP demonstrated a reduction in travel of the wrist and head as compared to the other chairs and a reduction in the pressure necessary to recline the seat, specifically in the shoulder region. The LEAP chair also provided a consistent pressure map for all test conditions, confirming that the chair maintained contact with the torso.