Working postures and activities of lorry drivers: a reliability study of on-site observation and recording on a pocket computer.

Poor working postures are associated with the development of musculoskeletal disorders. Many different observation methods have been developed to analyse working posture and activity. TRAC (Task Recording and Analysis on Computer) enables the observer to choose and define the variables and the categories within variables to be recorded at the workplace and analysed afterwards. In this study, inter-observer reliabilities were determined for the variables that were essential to ensure accurate recording of both working posture and activity of lorry drivers. The pre-set standard for observer reliability was not reached before the number of variables was decreased: the variables concerning activities and load handled were omitted in favour of those concerning body posture. As a result of this reliability study an improved application of TRAC is proposed. For the purpose of recording all selected variables a second observer is introduced, so that two observers work simultaneously at the working site. The first observer pays attention only to working postures and the second observer records, among other things, activities. An additional program has been written to combine the variables of both observers for subsequent analysis. This enables us to investigate the relation between activity, appliances or goods being handled, and the corresponding working postures. The second observer records on a real-time basis and provides accurate information on the duration and sequence of activities. It is considered that this twofold application of TRAC is an important contribution to the accurate analysis of workplaces.