ABSTRACT
Inclusive design research and practice seeks to make work and everyday tasks more accessible to all. The analysis of human characteristics for the purpose of user centered design is a central theme within “inclusive design” research and practice. Using this inclusive design approach requires a detailed understanding of the functional capability of the users relative to the particular task demands. Within the context of inclusive design, exclusion occurs when the task demands exceed a person’s capability to effectively respond to them. Variations in capability have been identified across the population which has included age related reductions in a range of capabilities, including muscular strength (Voorbij & Steenbekkers, 2001) and injury responses to particular physical task demands and poor work postures (Tuomi et al., 1991). It would appear from this research that the older workers did have reduced capability relative to the younger workers in terms of their muscular strength and injury experiences. In contrast, there are equally significant injuries and conditions which impact on capability which are not age dependent. Examples of this have included arthritis, strokes and cerebral palsy (Sears & Young, 2003). These seemingly contrasting results tend to support the view that capability changes across the population are not driven by a one dimensional factor of ageing. Rather, that there are a range of factors which may impact on the capability ranges of the population. The notion of inclusive design within the context of the current work
is to examine hand functional capability across a wide range of the population to appreciate the variations in capability for the whole population with a view making tasks more accessible to all. There is an increase in the proportion of older people in the workplace and the community in general and this trend is predicted to continue for many nations with the global increase in the proportion of people over 65 years set to triple by 2051 (United Nations Population Division, 2001). This global trend of an increase in the proportion of older people requires an analysis of the functional capability of this changing population to provide an objective assessment of the capabilities of the whole population. The reduction in capability for many people within the population contrasts sharply with the broad proliferation of many products and task demands that are beyond the capabilities of these people. This mismatch between user capability and task demands can result in people being excluded from part or all of their tasks that have demands that are in excess of their capabilities despite these people providing enormous benefit to industry in terms of their skills and knowledge. This issue has the potential to have a high personal and financial cost to the individual if they are marginalized and cannot safely and effectively complete their work and everyday tasks. This will also have a profound impact on the business in terms of retaining its “knowledge capital” which is vital for sustaining business operations and retaining the growth potential of an organization.
In addition to the multi-faceted nature of the capability-task demand relationship, there are significant capability variations both between people and within people over time. That is, the nature of the capability-task demand relationship is multifaceted and the rate and rate and type of changes being highly variable between people over time. The current research has focused on the capability of the hands as a mechanism for focusing the discussion a specific set of functional capabilities. The hands are the part of the upper limbs that provide the opportunity to have tactile contact between us and the tasks we are performing. The fine bony architecture of the hands provides a high degree of dexterity whilst also being capable of forceful gripping actions. In many cases the hands represent a central feature of the human-task interaction. Being able to measure the hands functional capability at the individual and population levels is a significant issue for predicting exclusion from work and everyday tasks. The extent of an individual’s hand functional capability has the potential as a measure to determine if they can perform a particular level of task demands. The hands are remarkably malleable which creates challenges if one were to measure each degree of freedom of movement for varied hand movements (assuming this were technically possible) during a task where there could potentially be many changes in the capability of the hands. That is, the very things which provide the hands with their highly flexible and variable capabilities also create challenges for the measurement of those aspects of the hands performance. Some of the early work undertaken in the area of classifying hand movements was undertaken by Napier (1956) who qualitatively differentiated types of grips according to the functional capabilities of each grip type. More recent work has identified other attributes of different classes of hand actions such as maximal grip forces in different hand grips (e.g. Kroemer, 1994). In contrast some research has used epidemiological data to determine hand / arm capability limits (e.g. Silverstein, et al., 1987) and this data has in turn been used to estimate task demands limits
