International audience This communication presents the results of our intervention following a request for assistance in the prevention of musculoskeletal disorders in a construction company. Our primary objective was to understand the practices developed by workers and site managers to anticipate the daily difficulties and risks in work situations (regulation prudence and preservation expertise). At the same time, we wanted to understand the arbitrations carried out during the preparation phase, as well as during site and operational meetings (two weekly organizational arbitrations), through their consequences in terms of performance, quality, health and safety on the concerned site. The goal of this systemic analysis was to understand the organizational obstacles to the proper deployment of the intelligence of workers and site managers, in order to co-design a new organization to better value employees and promote their development.