A Comparison of Front and Rear Wheel Shock Magnitudes for Manual Tilt-in-Space Wheelchairs with and Without Suspensions

When encountering an obstacle, both the front and rear wheels encounter a shock that may be unhealthy to the wheelchair user. Furthermore, depending on the obstacle there may be two peaks at each wheel - one when the wheel first encounters the obstacle and one when it leaves the obstacle. Limited research reports on these multiple peak accelerations at each wheel when investigating shock and vibration exposures in wheelchair users. There is also limited information comparing the front wheel impact to those at the rear wheel. One of the few studies available suggests the front wheel incurs greater shock than the rear wheel. However, this study had the wheelchair mounted on a treadmill for one of their obstacles. Although a treadmill controls for speed, the participants were not operating the wheelchair as they would during daily use. Using an attendant propelled tilt-in-space wheelchair, the present study investigated the initial impact at the front wheel versus the rear wheel, and the final impact at the front wheel versus the rear wheel. The obstacles included a door threshold, 2 cm descent, and 2 cm ascent. Front and rear wheel un-weighted and frequency- weighted (per the ISO 2631-1 standards) peak accelerations were significantly higher depending on the obstacle the wheelchair was traversing (door threshold, 2 cm descent or 2 cm ascent).