A participatory approach could be used to implement work place or organizational improvements. However, the question is which participants should be involved and how. In this paper the theoretical involvement in different steps of a linear stepwise approach is described and compared with the latest projects of 300 practitioners. From a theoretical point of view ergonomists and employees play an essential role in the improvement process and are involved in most stages of a change process. Designers play an important role in idea generation and prototyping. Top management and middle management are important in the first step to set goals that are consistent with the strategy of the enterprise. Middle management is also needed in the steps where improvements are selected. This theoretical prediction is affirmed. However, middle management appeared to be also involved in implementation. The role of ergonomists is in practice limited in later stages in implementation, which is not preferred by the ergonomists.