Kylmäaho E, Rauas S, Ketola R, Viikari-Juntura E. Finnish Institute of Occupational Health, Helsinki, Finland
A high number of people use the computer daily. Many studies have found relationships between video display unit (VDU) work and musculoskeletal problems. Especially disorders of the upper extremities have been related to a long duration of VDU work per day ( Punnett and Bergqvist 1997). Some studies suggest that supporting the forearm decreases the risk of musculoskeletal symptoms in mouse and keyboard work ( Aarås et al. 1997, Karlqvist et al. 1998). Supporting the entire forearm reduces static trapezius load during mouse and keyboard work ( Aarås et al. 1995), but supporting only the wrist during typing may increase the trapezius load ( Bendix and Jessen 1986). It has been commonly recommended to support the wrist and forearm during computer work. It is not clear, however, whether the location and extent of the wristforearm area that is supported, the degree of supporting, the type of support used or the continuity of supporting has any effect on musculoskeletal symptoms.
Our aim was to describe in a semiquantitative way how VDT workers support their forearms and wrists during mouse and keyboard work. These data formed a part of exposure information against neck and upper arm disorders in an intervention study ( Ketola et al. 1999).
The study population consisted of 109 office workers; 64 women and 45 men. Their mean age was 47.9 ±7.9 years. Two experienced physiotherapists interviewed the subjects and observed and made videorecordings of them in their regular computer work for about 15 minutes. Dimensions of the workstation were also measured and the equipment used was recorded.
The observers used a diagram of hands and forearms, in which they marked the contact area of the forearm and wrist (Diagram 1.). They also observed the degree of supporting (not at all, lightly, with full weight), the continuity of supporting (not at all, occasionally, all the time) and the type of supporting. In the analysis the contact area of the forearm was estimated as proportional area of