Population today is progressively aging in developed countries. The increase in the proportion of older persons (60 years or older) is being accompanied by a decline in the proportion of the young (under age 15). Nowadays, the number of persons aged 60 years or older is estimated to be 629 million and expected to grow to almost 2 billion by 2050, when the population of older persons will be larger than the population of children (0-14 years) for the first time in human history [DPI]. Naturally, people living longer also implies an increasing number of people affected by chronic diseases, such as heart disease, cancer and mental disorders. Chronic diseases may frequently lead to disability. It is estimated that the costs of health care could rise from 1.3 trillion to over 4 trillion dollars for these reasons [Ciole&Trusko, 1999]. Costs are particularly high if persons are not independent due to a disability.

Disability is a difficult concept to define, unless in a broad sense. It could be accepted that a person has a physical or cognitive disability when they lose the capacity to do some things on their own, meaning that their independence is threatened and that they require assistance in every day tasks. More specifically, disability implies not being able to to carry out the so called basic Activities of Daily Living (ADL) such as bathing, eating, using the toilet and walking across a room, as well as shopping and meal preparation.

Under these circumstances, either home assistance has to be granted or the person needs to be institutionalized. In nursing facilities, though, costs are higher and the quality of life is often reduced [Barton,1997]. Lack of human resources to assist elder people leads naturally to
create systems to do it in an autonomous way (e.g. [Volosyak,2005]). Studies on the use of assistive devices in a general population in Swedish descriptive cross-sectional cohort studies [Ivanoff,2005] reported that one-fifth at the age of 70 and almost half the population at the age of 76 had assistive devices, usually in connection with bathing and mobility. Another study of 85-year-olds in a general elderly population found that 77% of them had one or more assistive devices, also more frequently for bathing and mobility. The same pattern has been found in other general population studies, although the prevalence rates vary from 23 to 75% according to studied population, age group and type of assistive devices.

To sum up, prevalence rates vary, but the use of assistive devices is very common among the elderly and their use increases with age. It is consequently of extreme importance to create a new generation of tools to assist people with disabilities, so that their independence and autonomy is improved. Specifically, it is stated by health professionals that mastering of mobility assistive device skills enhances a person's autonomy and participation in ADL [Cortes et al, 2004]. Training these skills is also an important part of the rehabilitation process. Furthermore, assessment of wheelchair skill performance can provide valuable information about daily functioning and participation and even be used to check the progress of degenerative processes or rehabilitation therapy.