Pour évaluer les facteurs de risque reliés aux postures contraignantes et aux vitesses élevées, les chercheurs utilisent des méthodes techniques pour mesurer objectivement la charge de travail. Si les travailleurs disposent d’instructions écrites, ils peuvent éventuellement enregistrer leur propre charge de travail physique, ce qui permettrait d’évaluer des risques précis pour l’ensemble des travailleurs d’un milieu donné. Les objectifs principaux de cette étude étaient: 1) de comparer les analyses d’auto-enregistrement de l’élévation du bras pendant le travail en utilisant une posture de référence simplifiée par rapport à l’utilisation d’une posture de référence standard, et 2) de comparer les deux postures de référence. La faible différence entre les deux analyses indique que les enregistrements effectués par les employés eux-mêmes sont comparables, au niveau du groupe, à ceux effectués par les chercheurs. Les auto-enregistrements associés aux seuils d’intervention fourniraient aux employeurs une méthode d’évaluation des risques constituant une base solide pour la prévention des troubles musculo-squelettiques liés au travail.
Background
To reduce ergonomic risk factors in terms of awkward and constrained postures and high velocities, it is important to perform adequate risk assessments. Technical methods provide objective measures of physical workload. These methods have so far mainly been used by researchers. However, if written instructions how to apply the sensors and how to adopt the reference posture are provided, together with triaxial accelerometers, it may be possible for employees to record their own physical workload. The exposure in terms of e.g. upper arm elevations could then easily be assessed for all workers in a workplace. The main aims of this study were: 1) to compare analyses for self-recording of upper arm elevation during work using a simplified reference posture versus using a standard reference posture, and 2) to compare the two reference postures.
Methods
Twenty-eight cleaners attached an accelerometer to their dominant upper arm and adopted a simplified reference according to a written instruction. They were thereafter instructed by a researcher to adopt a standard reference. Upper arm elevations were recorded for 2 or 3 days. Each recording was analysed twice; relative to the simplified reference posture and relative to the standard reference posture. The group means of the differences in recorded upper arm elevations between simplified and standard reference analyses were assessed using Wilcoxon signed ranks test. Furthermore, we calculated the group mean of the differences between the simplified reference posture and the standard reference posture.
Results
For arm elevation during work (50th percentile), the group mean of the differences between the two analyses was 0.2° (range -7 – 10°). The group mean of the differences between the two references was 9° (range 1 – 21°). The subjects were able to follow the instructions in the protocol and performed self-recording of upper arm elevation and velocity.
Conclusions
The small difference between the two analyses indicates that recordings performed by employees themselves are comparable, on a group level, with those performed by researchers. Self-recordings in combination with action levels would provide employers with a method for risk assessment as a solid basis for prevention of work-related musculoskeletal disorders.