Dynamic backrest enables more trunk movement during multi-device office tasks
A dynamic backrest may help accommodate trunk movement, and multi-device work elicits more of it: An exploratory comparison of high-end office chairs under single- and multi-device tasks
Human-Computer Interaction
Summary
People often work with more than one device at the same time, which makes their upper body move more. The authors studied office chairs designed to move with the user and found that a chair with a flexible backrest allowed for more natural twisting of the torso during these multi-device tasks. However, overall comfort, muscle activity, and work performance did not change much between different chairs. The study suggests that office chairs should support more movement because modern work involves lots of shifting and turning.
What this means in practice
- •For office furniture designers: Design office chairs that allow lateral backrest movement to better support natural trunk motions during multi-device work.
- •For ergonomics consultants: Develop workplace assessments and recommendations that consider increased upper body movement demands in multi-device office setups.
Authors
Yejin Kang, Dusan Baek, Dongwoo Park, Kitae Hwang, Woojin Park
Abstract
Dynamic-sitting office chairs are usually compared with static sitting rather than with each other, and the contribution of backrest deformability (lateral backrest movement) is unknown. Office work also increasingly spans multiple devices. Twenty healthy adults (10 men, 10 women) completed a 15-minute single-device and a 15-minute multi-device proofreading task on each of three chairs: two commercial dynamic-sitting chairs (T90, Aeron) and a T90 whose backrest lateral movement was mechanically fixed (T90-fixed). We recorded subjective ratings, head and trunk posture (inertial measurement units), upper trapezius and lateral gastrocnemius activity (electromyography), and task performance. Chair effects were largely null: T90 and Aeron did not differ in ratings or performance, posture and muscle activity showed only isolated, direction-inconsistent differences, and preferences were polarized. The standard T90 showed greater trunk movement (mean absolute angular velocity in yaw) than T90-fixed during the multi-device task (p = 0.042), which may indicate that its movable backrest helps accommodate trunk movement under demanding work; no other whole-sample posture, muscle, rating or performance measure differed between these two configurations, and replication is needed. Task effects were large and consistent: the multi-device task elicited greater and faster head, trunk and shoulder movement and higher upper trapezius activity than the single-device task, with lower reading throughput. Multi-device work thus imposes substantially greater movement demands than single-device work, which supports designing chairs that accommodate movement in modern work environments.