Perceived muscular tension, emotional stress, psychological demands and physical load during VDU work

Objectives. The aim of this study was to investigate whether perceived muscular tension, psychological demands and emotional stress were associated with physical load or working technique during visual display unit (VDU) work. Methods. Subjects (28 women and 29 men) from two different organisations volunteered to participate in the study. The study design was cross-sectional, and the data were assessed when the subjects performed their usual work tasks at their usual work place. Multivariate linear and logistic regression models were used to investigate possible associations. The different outcome variables were: median muscle activity and muscular rest in the trapezius muscle bilaterally, wrist movements and working technique. The different explanatory variables were: perceived muscular tension (binary), emotional stress (binary), psychological demands (binary), organisation (binary) and gender (binary). Age (continuous) and present musculoskeletal pain (binary) were also controlled for in the multivariate models. Electromyography (EMG) and electrogoniometers were used to assess the physical load, and the data collection time was 15 min. An ergonomic checklist was used to assess working technique, i.e. work with lifted shoulders. Results. Subjects who perceived muscular tension at least a few times per week the month before the measurements were made worked with higher muscle activity [expressed as per cent of a reference voluntary electrical activity (% RVE)] in the trapezius muscle bilaterally (5% RVE, P=0.05). High emotional stress during the measurement was associated with higher muscle activity in the trapezius muscle on the side not operating the computer mouse (8% RVE, P=0.006). Subjects who reported high levels of emotional stress worked more often with lifted shoulders (odds ratio 6.0, 95% CI 1.2-28.9). However, when present musculoskeletal pain was included in the multivariate model the odds ratio for high emotional stress decreased to 4.5 (95% CI 0.9-23.2). Conclusions. Perceived muscular tension and emotional stress were associated with physical load, in terms of muscle activity in the trapezius muscles, during VDU work in ordinary occupational settings.