Ergonomic study of special office chairs

Frequent and sustained work in a static seated posture may lead to muscle tension and spinal disorders at VDU and office workplaces. This can cause both excessive stress upon the muscular system, particularly in the neck and shoulder region, and functional underloading of certain muscle groups, such as the back and abdominal muscles. The concept of dynamic sitting has therefore been promoted in recent years in the development of office chairs. Some chair manufacturers have used design elements, such as dynamic mounting or inherent spin of the seat surface, to create particular chair properties which promote dynamic sitting and thus assist in preventing musculoskeletal diseases at office and VDU workplaces.

In the light of these developments, the VBG (the institution for statutory accident insurance and prevention in the administrative sector) initiated an ergonomic study in which four special dynamic office chairs were evaluated in comparison with a conventional office chair. The study was conducted in conjunction with the IFA and the Dutch TNO Work and Employment institute. The objective of the study was to find answers to the following questions:

• Do specific dynamic chairs lead to a significant increase in physical/muscular activity at VDU and office workplaces in comparison to a conventional office chair?
• Do employees working at VDU and office workplaces experience the special chairs subjectively as beneficial to their health when compared to a conventional office chair, and do they accept the chairs in their everyday work?

In order to find answers to these questions, a representative VDU/office workplace was created in a laboratory environment with which the sitting and movement behaviour of ten laboratory test subjects performing standardized office tasks could be analysed by means of measurements and standardized interviews. In addition, measurements and surveys of 40 test subjects in total in four different companies were conducted under real-case conditions.

For the purpose of the study, a measurement system based upon the CUELA system was developed and employed. This system permits ergonomic analysis of stress and strain parameters synchronous to office chair adjustment parameters, in both laboratory and field environments.