Effect of seat orientation on ingress/egress joint kinematics and reach envelope

Abstract

BACKGROUND: Little is known about ingress/egress requirements and forward reach for workstations with horizontal seats. This research explored differences between ingress/egress kinematics and reach due to seat orientation. METHODS: 10 participants performed ingress/egress tasks using three seat orientations (horizontal with 90 ◦ and 120 ◦ seat angles, and vertical with 90 ◦ seat angle) and planar reach tasks in three anatomical planes using horizontal and vertical seats with 90 ◦ seat angle. An optical motion capture system was used to record kinematic data. Marker data was processed and modeled to estimate peak joint angles and ranges of motion of several body joints. For reach tasks, marker data of the clavicle and finger were used to plot reach capacity. RESULTS:Ingress/egress joint kinematics differed greatly between horizontal and vertical seats, while few differences existed between the horizontal seat orientations. Peak angles and ranges of motion during ingress/egress of the horizontal seats were significantly higher than the vertical seats, often by a factor of 3–4. The direction of motion affected several peak angles and ranges of motion, but to a lesser extent than seat orientation. Reach was unaffected by seat orientation. CONCLUSION: This study’s findings suggest that ingress/egress of horizontal seats is more stressful for the body, especially the shoulders and lower back, than regular upright seats.