Increasing frequency in skeletal muscle problems in sectors of employment where the work is repetitive is the cause of growing concern. A number of agro-food businesses have participated in ergonomic studies aimed at a better understanding of repetitive work and its effects on health, as well as at improving work situations. Different issues related to the analysis of work and the contribution of the ergonomic approach were raised in these studies. In particular, the results of a study of a poultry processing plant were used to illustrate these issues. The first part of this article deals mainly with the expectations of those within firms requesting service vis-à-vis the work of ergonomists and the characteristics of their approach. Even though the field of study of ergonomists is often restricted to the biomechanical aspects of the activity, they rather seek to obtain an overall view of work situations by examining not only the physical aspects but also the cognitive, perceptive, social and subjective aspects which cannot be disassociated from work efficiency.

During an intervention, the reference data of the ergonomist are limited, especially those related to skeletal muscle problems. It is observed that these references can only be used as pointers identifying occupational hazards, and only specifie knowledge of the work environment, continuously updated with each new study, can provide them with the elements of understanding and demonstration necessary for change. Furthermore, an ergonomic approach can lead to work situations being changed only if there are changes in the way that different participants, worker representatives and firm managers see their work. Thus, it is essential that various partners participate in the ergonomic study. Partners can participate through a project committee that brings together the key persons who will be trained in ergonomy, who will follow the progress of the study and who will develop recommendations and their application.

The second part highlights the importance of ergonomists using data from different sources in order to better understand the complexity of the work activity. Results from the exploratory stage of a study of a turkey cutting production line are used, especially those related to the seventeen women working in rotation at several stations on this line. Results obtained from three workstations are compared, and analysis of accidents, observation of work activity, answers from individual interviews and group meetings are used to interpret results. Above all, the apparent lack of coherence of the results was surprising. This workstation, which was the one most often mentioned in accident reports, is precisely where the women workers spend the least amount of time (5 % of their working time), and where a smaller number of workers reported feeling pain symptoms. It is also the most hated workstation. On the other hand, the station which is best liked is the one with which most workers associate the development of their pain symptoms. The third station is used for the temporary assignment of injured workers, and is where many workers report problems related to maintaining a static posture. These three stations will be examined in turn in order to bring to light the demands of each one, the actual experiences of workers at these stations and the possible contributing factors to the development of skeletal muscle problems. For example, we consider the possibility that reports of skeletal muscle problems can be made more easily about a station where accident-type circumstances can be described (such as through pulling or hitting) than about a station where the work is more static (such as visual checking of quality) in spite of considerable posture constraints. We also highlight the potential significance of pride in work well-done and pushing oneself, which makes workers seek a station where, apart from the physical constraints, they could take up a challenge and derive personal satisfaction from it. We discover the creativity developed by workers in spite of the very repetitive nature of their work. In conclusion, these different, seemingly contradictory results demonstrate different aspects of the same reality and provide direction for discussions about improvements to be made.

The third part is devoted to the systematic analysis of the activity and its use for improving work situations. Firstly, we describe the methods used in two work environments in order to obtain a more thorough understanding of the work activity and its determinants, and to make recommendations. These methods allow workers' know-how to be used profitably in order to better understand the work. Following the exploratory stage of the study of the turkey cutting production line, some of the stations were observed in more detall. The data are used to highlight the different operating methods developed by five workers at the same workstation, despite the fact that the work cycle only lasts twelve seconds. The differences show up in the order of operations and the movements and postures of work, thus demonstrating that on-line work which seems very stereotyped can be performed in very different ways. These differences also imply different physical demands as shown by the different skeletal muscle problems. Although the ways of doing things vary from one person to another, they can also vary in accordance with the conditions in which the work is performed. This fact was then demonstrated through the comparison of strategies of ten workers at the same workstation following two work paces. These different strategies developed by workers to cope with the demands for speed, given their physical capacity, have an impact on production. Complying with operating methods is of utmost importance since this involves the very identity of the people. However, the descriptions of these operating methods lead to the discovery of know-how which, used in training, can prevent some problems from developing. It is therefore very important to stress on know-how in these work environments where automation has resulted in the occupation being devalued.

To conclude, the work of ergonomists is performed on several levels. Not only do they have to observe how people work and understand why they work in different ways, but they also have to be able to be convincing and create dynamics producing change in work. Moreover, given the importance of the approach of studying the multidimensional aspects of work activity, it is useful to bring the disciplines together in order to use current knowledge effectively thus serving to improve work safety and efficiency.