BACKGROUND : Work activity integrates the tasks to be performed, the means of work available, the instructions, the rules to be observed, the particular factors related to the individuals (skills, inner state), and the effects both on the task and on the operator. By analyzing the activity, the different logics and conflicts in the design of production systems are revealed. OBJECTIVE : To show how the work activity can support the transformation of the working conditions, when revealed by an ergonomic intervention, by integrating the different design standpoints, which are always present in the project’s work situations. METHODS : For this case study, the Ergonomic Work Analysis (EWA) was used on the staff that serves meals at a new university restaurant in Rio de Janeiro (Brazil) with a focus on the portioning of the transported ready-cooked meals and the variability related thereto. The results of observations, verbalizations, self-confrontations and strategy analysis, collected through field notes and audio and photographic records, became a final report submitted to the directors of the university restaurant. RESULTS: This research showed that the work activity of the serving maids helped to reveal the different logics of the heterogeneous actors in the design of the work situation under analysis. The work activity, when revealed by an ergonomic intervention, can be an interface during the design process to articulate these different logics and to support the dialog among different design standpoints. Thus, the concept of fixed portioning became a concept of flexible portioning, which provided the serving maids with an increased autonomy level at the counter, thus improving both the quality of services and the working conditions of those involved therewith. CONCLUSIONS : The activity-focused design can be understood as an ongoing, multiple logical process whereby workers bring the design into their workplaces, which reveals aspects of their own activity, thus helping to change the initial concepts. The ergonomic intervention, based on the revealed activity, helps to highlight the existence of different logics and also to support the actors in articulating their own logics during the design process.