The study aim was to explore the experience of doctors and nursing assistants in the management of physical restraint (PR) in critical care units. A multicentre phenomenological study that included 14 critical care units (CCU) in Madrid (Spain). The CCU were stratified according to their use of physical restraint: "frequently used" versus "seldom used". Three focus groups were formed: the first comprised nursing assistants from CCUs that frequently used physical restraint, the second comprised nursing assistants from CCUs that seldom used physical constraint, and the final group comprised doctors from both CCU subtypes. Sampling method: purposive. thematic content analysis. Data saturation was achieved. Four principle themes emerged: 1) concept of safety and risk (patient safety versus the safety of the professional), 2) types of restraint, 3) professional responsibilities (prescription, recording, and professional roles) and 4) "zero restraint" paradigm. The conceptualisation regarding the use of physical contentions shows differences in some of the principal themes, depending on the type of CCU, in terms of policies, use and management of physical constraint (frequently used versus seldom used). The real reduction in the use of physical restraint in CCU must be based on one crucial point: acceptance of the complexity of the phenomenon. The use of physical restraint observed in the different CCU is influenced by individual, group and organisational factors. These factors will determine how doctors and nursing assistants interpret safety and risk, the centre of care (patient or professional-centred care), the concept of restraint, professional responsibilities and interventions, interactions of the team and the leadership.