Wheelchair and seating biomechanics research includes studies to prevent secondary conditions due to wheelchair and seating use, and to reduce the incidence of accidental injuries. Upper extremity models have been created in order to determine motion as well as net joint forces and moments. It has been shown that wheelchair pushrim forces are related to nerve conduction studies (NCS) variables. A pushrim activated power assisted wheelchair (PAPAW) uses motors and batteries to augment the power applied by the users to one or both pushrims during propulsion or braking. Powered wheelchairs can be grouped into several classes or categories. A convenient grouping by intended use is primarily indoor, both indoor/outdoor, and active indoor/outdoor. In response to the needs of clinicians with specialized knowledge of and experience with assistive technology (AT), the Rehabilitation Engineering and Assistive Technology Society of North America (RESNA) developed a credentialing program in AT.