Analysis of whole-body vibration during manual wheelchair propulsion: a comparison of seat cushions and back supports for individuals without a disability.

Whole-body vibration exposure has been found to be detrimental to the health of humans owing to effects such as degraded comfort, disc degeneration, and lower back pain. The purpose of this study was to determine if selected seat cushions and back supports minimize the transmission of vibrations during manual wheelchair propulsion. Ten unimpaired participants traversed an activities of daily living course using four seat cushions and four back supports. Vibrations were measured using triaxial accelerometers. The time domain and frequency domain transmissibility was used to determine if differences exist among seat cushions and back supports. Differences were found among the four seat cushions and four back supports. Seat cushion and back support manufacturers should concentrate on single-event shocks and repeated shocks, as opposed to oscillatory motions and self-generated vibrations, because the vibrations generated by these events tend to reside in the range of frequencies most sensitive to humans. Vibrations in this range of frequencies have the greatest effect on the transmission of whole-body vibration during manual wheelchair propulsion. Differences among the seat cushions and back supports appear to be due to the seat cushion/back support design and postural support. From a clinical perspective, the time domain transmissibility best describes the transmission of whole-body vibration.