Computer workstations - body postures

Insufficient physical exercise and one-sided body stress in primarily sitting activities may lead to strain injuries of the lumbar spine. Therefore, we were concerned with the question how to optimize the design and use of ergonomic office chairs. In this field, one needs information about body postures assumed at the workplace, which can be determined by observation techniques or self assessment of the employees. We investigated the validity of self assessment data, compared to those collected during observation.

It was expected that the employees misperceive their body posture, at least to a certain extent. However, with increasing practice in self assessment, the corresponding error should decline. In addition, we investigated whether the degree of misperception is moderated by  the presence or absence of back pain.

To assure comparability of self assessment and observation data, a questionnaire for the self assessment has been developed, by analogy with the REFA multi-moment observation technique. Using this questionnaire during 10 weeks, 30 subjects assessed their posture while the experimenter recorded the same features employing the REFA method. Biographical data were collected to group the subjects as suffering or not suffering from back pain.

The values for the self assessment of body posture are rather close to the observation data. In addition, the practice effect was significant, the self assessment improved especially during the first days of the investigation. And finally, the expected sensitization effect for subjects with back pain could be confirmed. However, this effect was not restricted to body posture, but was also found for the self assessment of task variables.

In subsequent investigations the seemingly unspecific sensitization effect of back pain should be analyzed in more detail. A potential reason for our result might have been that task variables correlated with body posture in the field setting, allowing to infer one aspect from the other. Thus, for settings with no correlation of these variables one would expect a sensitization more restricted to the body posture aspects.

Schwarz, S. (1998). Untersuchung zur subjektiven Einschätzung der Körperhaltung an Büroarbeitsplätzen. Unveröffentlichte Diplomarbeit, Fakultät für Psychologie, Ruhr-Universität Bochum.