ergonomic chair - worksafe report

 

REPORT ON THE KNEELSIT ERGONOMIC CHAIR

This chair presents as an unusual and carefully designed combination chair which includes both a height adjustable backrest and kneeling cushion. The mobility of the chair is facilitated by the attachment of five floor casters to a rigid sleigh shaped metal frame. The upholstery foam and fabric appear to meet chair standards for durability, composition and flammability. The chair moves quietly and it feels solid

Chair Finish

After an initial inspection of this chair a few years ago quality improvements have included a covering of the seat depth adjustment notches with a swing cover to prevent any injury to the user or the catching of clothing during use.
The metal frame and parts have all been treated for rust resistance and smoothly coated to prevent hand or foot injury during component adjustment or use.

Chair components

a) Backrest
The backrest is solid and well constructed.   The upholstery is firm with sufficient foam density to provide forward and upward lumbar spine support.  The size and height of the backrest and the horizontal and vertical adjustments fall within the suggested sizes of backrests for commercial chairs suggested by the Worksafe criteria and current AS/NZS standard No.4438:1997.  The backrest is also height adjustable  along a substantial shaft. 
All these adjustments, including the rearward extension, reinforce the efforts made to accommodate a large range of users.

b) Chair seat
Again the upholstery is well shaped and firmly covered for user support. The seat does not bottom out and sideways dishing of the seat is minimal to prevent any movement constraint on the user when changing position.  The seat can be moved through a range of upper leg lengths for thigh distance comfort and to reduce forward pressure on the knees. 

The seat is also compression adjustable by a spring mechanism under the seat pan. This mechanism allows for the accommodation of a range of body weights . Heavy rubber stoppers are positioned on all components of the chair to prevent metal to metal impact and to reduce jarring when changing sitting position.
It should be noted that care should be taken to avoid trapping fingers under the compressible seat pan. #

c) Kneeling Cushion
The  cushion  is  strongly constructed and covered with the  same quality upholstery.  The rotation shafts on the cushion base fit firmly into the height adjustment notches to prevent unexpected swivel or displacement of the cushion.   The cushion can be height and angle adjusted through a considerable range  to accommodate upper leg length and also different degrees of flexion involving the lower leg.   This mechanism allows for many options in reducing the forward knee pressure and accommodating upper leg length.The options available in the angle and height position of  the kneeling cushion also allow accommodation of varying knee flexion and lower leg length.

User comfort and convenience

In general, dissatisfaction expressed by users of "kneeling design" chairs has included the lack of back support when the user becomes fatigued. The designer of this chair has made every effort to overcome this disadvantage by adding a lumbar support cushion which is ideally designed and mounted with optimum flexibility.

Difficulties arise when chair design needs to accommodate a broad range of users and this chair has an added constraint over and above the design of conventional, ergonomic chairs which are not directly influenced by the upper leg length of the user.  In this chair design every effort has been made to comfortably seat users across a very broad range of anthropometric dimension and to avoid undue forward pressure on the knees.

Comments

The options for posture change and lumbar support combined with a sit/kneel position of seating makes this chair design unusual and innovative.  Not only would this chair appeal to a general user community but users with mobility disfunction should benefit by its unique design.  The appeal of this chair, in a multicultural community like Australia with diverse population anthropometry, should also be applauded.

Glena Ellitt

M.Safety.Sc., B.Sc., G.Dip.Ed., Cert.Q.Audit, R.N., M.R.C.N.A., M.E.S.A.

# This aspect has now been corrected by the addition of fingerguards.
(G. Usher)