rather than individual measurement. Measuring functional capacity outcomes requires determination of the performance of the whole person. Standardized measures of functional outcomes for use in evaluation or diagnosis are being developed, but they are not routinely used to obtain outcomes measurements for specific interventions. Contextual and environmental factors, however, must be noted and controlled: frequently, there is a difference between capability (the ability to complete a task in an ideal situation) and real-life performance (the ability to complete a task in a typical situation). Such standardized measures would be important for monitoring individuals and for determination of the costs-benefits of rehabilitation programs and interventions to society. Care must be taken in using existing outcomes measures accurately, because measurement at the functional limitation level is expensive and difficult.
Functional limitations measures—obtained, for example, through gait studies and gait analysis—are few and incompletely validated. Although computerized locomotion analysis laboratories have been widely available for many years, few data support the need for gait analysis in clinical decision making, with the possible exception of presurgical decisions for children with cerebral palsy (Krebs, 1995). More studies of locomotor activities of daily living (ADL) are needed to assess functional performance pre- and postintervention and to provide descriptions of the nature of functional limitations. For example, it is known that people with balance disorders may have ataxic gait, but there is no quantitative clinical, bedside, or laboratory measure of ataxia. As a result, treatment for ataxia resulting from cerebellar lesions is entirely empiric. Measurement at the level of functional limitation requires at least whole-body, person-level measurements of performance of ADL. Such measures should include not only the gait on smooth, level surfaces but also sit-to-stand, stair ascent and descent, turning, reaching, and other locomotor ADL.
Basic ADL include locomotor ADL and bowel, bladder, and sexual functions; that is, those ADL that are usually performed without aids or instrumentation. Instrumented ADL (IADL), by contrast, include some device such as a telephone or toothbrush in the performance of a task. Thus, the adaptation (or lack thereof) of the device will affect performance capacity. For example, a child may write or brush her teeth much better with a large-diameter pencil or toothbrush than with regular devices designed for use by adults. Elderly people with impaired vision will perform as well as subjects without impaired vision if the numbers on an instrument are large and have high contrast. Functional limitations research usually attempts to obviate such IADL differences, but in practice, some standardization is required even in basic ADL. For example, stair or chair height contributes substantially to performance variation (Krebs et al., 1992). Burden-of-care measures such as the Functional Independence