Influence of the two-hand control device on the WRMSD risk

Within the framework of its missions of assistance for the prevention of WRMSD of the Upper Limb, the INRS was requested to study the possible relation between the use of two-hand control devices and the development of WRMSD. This request came from the employers representatives, the employees representatives and CRAM. In addition, during the last few years and according to manufacturers, two-hand control devices were the object of technological development for reducing WRMSD. However, no bibliographical data are related to the ergonomics of old or new two-hand control devices. The two-hand control devices are safety devices. By using them, the hands of the operators are outside a danger zone. The use of these devices is always included in a global task. Consequently, the study of these control devices cannot be done without analyzing the work task which surrounds it and which builds its context of use. The study was led in two firms. This allowed to analyse different use contexts and several types of two-hand control devices. The results show that the two-hand control devices can be regarded as a working tool. Indeed, their use demands a significant time and is a real part of the task within the operating cycle. The use of two-hand control devices does not seem to be a risk factor of WRMSD, except in specific contexts. However, this study does not make it possible to conclude definitively on the relation between the use of the two-hand control devices and the development of WRMSD, but it provides some answers and reflections on this new request.