Documents Wahlström, Jens 3 results

"Assessment of working postures by observation is a common practice in ergonomics. The present study investigated whether monetary resources invested in a video-based posture observation study should preferably be spent in collecting many video recordings of the work and have them observed once by one observer, or in having multiple observers rate postures repeatedly from fewer videos. The study addressed this question from a practitioner's perspective by focusing two plausible scenarios: documenting the mean exposure of one individual, and of a specific occupational group. Using a data set of observed working postures among hairdressers, empirical values of posture variability, observer variability, and costs for recording and observing one video were entered into equations expressing the total cost of data collection and the information (defined as 1/SD) provided by the resulting estimates of two variables: percentage time with the arm elevated <15° and >90°. Sixteen measurement strategies involving 1–4 observers repeating their posture ratings 1–4 times were examined for budgets up to €2000. For both posture variables and in both the individual and group scenario, the most cost-efficient strategy at any specific budget was to engage 3–4 observers and/or having observer(s) rate postures multiple times each. Between 17% and 34% less information was produced when using the commonly practiced approach of having one observer rate a number of video recordings one time each. We therefore recommend observational posture assessment to be based on video recordings of work, since this allows for multiple observations; and to allocate monetary resources to repeated observations rather than many video recordings."

"This review summarizes the knowledge regarding ergonomics and musculoskeletal disorders and the association with computer work. A model of musculoskeletal disorders and computer work is proposed and the evidence and implications of the model together with issues for future research is discussed. The model emphasizes the associations between work organization, psychosocial factors and mental stress on the one hand and physical demands and physical load on the other. It is hypothesized that perceived muscular tension is an early sign of musculoskeletal disorder, which arises as a result of work organizational and psychosocial factors as well as from physical load and individual factors. It is further hypothesized that perceptions of exertion and comfort are other possible early signs of musculoskeletal disorders in computer work. Interventions aimed at reducing musculoskeletal disorders due to computer work should be directed at both physical/ergonomic factors and work organizational and psychosocial factors. Interventions should be carried out with management support and active involvement of the individual workers."(Author's abstract)

"The overall aim of this thesis was to explore associations between physicalload, psychosocial and individual factors in visual display unit (VDU)work. Furthermore, the aim was to investigate whether perceived musculartension is a predictor of neck pain among VDU operators. The thesisis based upon five separate studies, two laboratory studies, two fieldstudies and one prospective cohort study.Several different methods were used to assess the physical load. Electromyography(EMG) was used to record muscle activity. Wrist postures andmovements were assessed by means of electrogoniometers. An instrumentedcomputer mouse was used to measure the forces applied to thecomputer mouse. Working technique was assessed with an observationprotocol. Perceived exertion, comfort, mental stress and perceivedmuscular tension were assessed with questionnaires.The results of this work are discussed in relation to a proposed model forVDU work and musculoskeletal symptoms. The first two studies (StudiesI and II) support an association between individual factors (workingtechnique and sex) and the physical load. In Study III we observed thatthe physical load increased as a result of mental stress and increasedproductivity. Besides an increase in muscle activity; increases in the forcesapplied to the computer mouse and increased repetitiveness of wristmovements were also observed. The results from the third study alsosupport an association between psychosocial factors and physical loadthrough increased physical demands. The fourth study (Study IV)supports an association between perceived muscular tension and physicalload and perceived muscular tension is hypothesized to be an early sign ofmusculoskeletal symptoms. In Study V an increased risk of developingneck pain was observed among subjects who perceived high musculartension, even when controlling for job strain, physical exposure and age.It is concluded that the physical load during VDU work is affected bypsychosocial and individual factors as well as physical demands. VDUusers who perceives muscular tension at least a few times per week appearto have an increased risk of developing neck pain."