“work disability” or other restrictions to social participation. Close inspection of the definitions given above suggests that a number of steps can be identified in the pathway between the health condition and the social consequences described as work disability. At a micro level there are the pathological changes in the body and impairment in the structure and functioning of organs and body systems. There may be an impact on the activity of the person, ranging from simple movements, to basic activities of daily living, to instrumental activities of daily living, and so on. These can then contribute to the performance of more complex social roles, and ultimately, the person’s participation in all aspects of society can be adversely affected. Work is one such social role.
Both the Nagi and the ICIDH models cover the spectrum of the consequences of health conditions. As indicated earlier, as well as terminology, a major difference is where these models place the boundaries between the different concepts (see Figure 3). In the Nagi model the performance of all activities, except for basic actions or functions of the body, is subsumed into the overall category of disability (Nagi, 1976). In the ICIDH model the concept of activity includes these basic actions as well as ADLs, IADLs, and some other role activities (with the emphasis very much on activity) (WHO, 1980, 1997; Badley, 1993). Participation is reserved to highlight the way in which the performance of activities may be constrained by more than the immediate context of the activity. The juxtaposition of the two models in this way illuminates some nuances in the ways