Evaluation of Electric Powered Wheelchairs and Exposure to Whole-Body Vibration

The detrimental results of whole-body vibration (WBV) and their effect on humans in the seated position have been documented. Although wheelchair users are subjected to WBV little research has been conducted to assess these vibrations or attempt to reduce them.Sixteen able bodied subjects tested two powered wheelchairs: a Quickie S-626 and an Invacare 3G Torque SP. Each subject tested all of the configurations of the suspension wheelchairs and solid inserts to represent a non-suspension wheelchair. In each of the configurations of the wheelchairs, the subjects traversed an Activities of Daily Living (ADL) course. Vibrations were collected from a tri-axial accelerometer mounted to a ¼ inch aluminum seat plate during driving over the activities course. Root Mean Square Values and Vibration Dose Values were analyzedStatistical analyses of the RMS and VDV data revealed significant differences between the six different suspensions over each of the obstacles in the activities of daily living course. Post-hoc analyses revealed that for each of the obstacles, significant differences existed between the Invacare suspension and the Invacare solid insert. For the Quickie power wheelchair the solid insert setting was not significantly different from the most-stiff setting for each of the obstacles except the smooth surface. The solid insert setting was significantly different than the lowest and mid stiffness settings for all of the obstacles except the smooth surface and the deck surface.Without significant periods of rest the effects of WBV are cumulative throughout the course of the day, and the longer the exposure time the lower the threshold of non-harmful vibrations. Although most of the suspension systems are capable of reducing the amounts of vibration transmitted to the users the results of the vibration dose values seem to indicate that they may not reduce them enough to reduce probability of injury in powered wheelchair users.Future work should move towards examining these vibrations to evaluate what actual levels of WBV wheelchair users are experiencing over the course of an entire day and examining relationships between suspension and user weight to make data available to clinicians and wheelchair companies for suspension tuning