Fig 2.

Shows how one of the authors (J.W.) would illustrate the hypothetical relationship among variables in the ICF framework, at impairment (body structure/function) and activity/participation levels. Note that several variables at a lower level contribute to performance at the next level (a highly oversimplified model in this example, in that each activity depends on only 3 body functions), with the numbers next to each arrow indicating hypothetical weights reflecting the importance of each variable in determining performance at the next level. Thus, for example, the activity of walking is strongly determined by performance capacity B (lower extremity strength), but less strongly by performance capacities A and C (proprioception and spatial attention, respectively). In contrast, the activity of driving is less strongly dependent on capacity B (lower extremity strength) but has a stronger relationship to capacities C (spatial attention) and D (peripheral vision). The enablement theory involves hypothesizing and subsequently determining the locations of the relevant causal arrows in such a schema and their relative weights. Note several implications of this model: (1) in general, improvement in capacity B (lower extremity strength) would be expected to have greater impact on walking than on driving; (2) isolated application of the study treatment, even if effective, would be predicted to lead to substantial improvements in walking for many patients, but in driving only for those patients with spatial attention and peripheral vision (ie, studies seeking to demonstrate impact of the study treatment alone on driving should select patients with normal spatial attention and peripheral vision); and (3) in a heterogeneous patient population, the study treatment may need to be combined with treatments for capacities C and D in order to see a widespread impact on driving.