Influence of hand-rim wheelchairs with rear suspension on seat forces and head acceleration during curb descent landings.

OBJECTIVE: Shocks and vibrations experienced while using a hand-rim wheelchair can contribute to discomfort, fatigue and injury. The aim of this study was to compare the seat forces and head accelerations experienced by manual wheelchair users during independent curb descent landings in a standard and 3 suspension-type rigid-frame wheelchairs. EXPERIMENTAL: repeated measures analysis of variance. PARTICIPANTS: Eight men with paraplegia due to spinal cord injury. METHODS: Participants performed independently-controlled curb descent maneuvers with 4 wheelchairs. The seat force and head accelerations were compared across wheelchairs. RESULTS: The suspension-type wheelchairs decreased the seat force and head accelerations by significantly (p < 0.05) extending the force rise time. Also, the seat force and head accelerations were inversely related to the seat force at initial contact. The monoshock-based suspension wheelchairs showed the least seat force and longest force rise time. CONCLUSION: Suspension systems result in softer landings by attenuating the magnitude and time duration of the force and reducing head accelerations. Hand-rim wheelchair users can also soften landings by utilizing a "pull-up" strategy that reduces the force and head accelerations. Softer landings can contribute to improved ride quality.