to achieve this, the user should be provided with a clear width of not less than 600mm beneath the worksurface, a clear depth of not less than 600mm from the front edge of the worksurface and a vertical space of not less than 650mm from the floor. However, these are only the minimum dimensions and larger clearances are preferable to give greater freedom of movement. The very nature of office work can result in people spending prolonged periods of time in the
seated position. It is vital, therefore, that any seat provides stable bodily support in a position that is comfortable over a period of time, physiologically satisfactory and appropriate to the task or activity.
The main requirements for an office seat
- Blood circulation to the lower limbs is not restricted
- It is easy to change and maintain a variety of postures with little muscular effort
- Loading or stress on the spine is minimised
- The seat surface has sufficient friction to avoid slipping off
- For thermal comfort, fabrics are permeable
- Compatibility with the worksurface – especially height and the layout of equipment.
BS EN 1335 part 1 (Office furniture Æ office work chair: dimensions) specifies requirements for various aspects of office seating such as height, depth and width, and dimensions of backrests and armrests. However, it is acknowledged that seating comfort is a complex matter, which involves more than just supplying a chair that fulfils these criteria. The chair cannot be considered in isolation. It must always be considered in conjunction with the worksurface and the tasks being undertaken. If the user's work is varied, involving frequent changes in position such as walking from office to office, the
posture changes allow muscles to alternate between states of tension and relaxation alleviating the pressure on spinal discs. For some workers, however, whose daily tasks require sitting in a relatively static position for extended periods respite for muscles and spinal discs is not so easily achieved. This is highlighted in the instance of VDU workers where the workstation equipment determines the person's posture. For example, the position of the operator's arms, hands and the distance he or she can sit from the desk is dictated by the position of the keyboard and the arrangement of equipment. There is limited opportunity for them to change position at their desk whilst still being able to complete their task. There is some clinical evidence that
constrained postures such as these contribute to adverse health issues like
back pain. It is essential, therefore, that predominantly desk-based office workers have an adjustable chair , which allows plenty of posture changes. Adjustment should be possible to the backrest, seat and backrest height and the degree of seat tilt by controls that are easily reached from the seated position and operable without excessive force. It is counter productive to have a chair with numerous complicated controls which users do not know how to adjust, adjust incorrectly or simply do not bother with. People should be educated to know why, when and how to make adjustments.
