The notions of Operational Leeway and Power to Act have been widely developed in recent years, particularly in the respective fields of ergonomics and psychology. The intuitive understandability of these notions has led to their widespread use in the discourses of clinical approaches to work activity, notably in relation with the prevention of musculoskeletal disorders or psychosocial risks. Consecutively, confusions and inaccuracies are noted both in scientific exchanges and professional debates of ergonomists and psychologists. In recent years, the growing collaborations between activity ergonomics and occupational psychology - and more specifically the clinical activity approach - has made this issue more evident. Thus, the authors - all ergonomists - propose a theoretical articulation of concepts of Operational Leeway and Power to Act. The main consequences of this model for ergonomic intervention are finally developed