Vibration exposure injuries and prevention

While propelling a wheelchair, users encounter obstacles such as bumps, curb descents, and uneven driving surfaces. These obstacles cause vibrations on the wheelchair and in turn, the wheelchair user, which through extended exposure can cause low back pain, disc degeneration and other harmful effects to the body (Seidel et al., 1986). Typically, seating systems are prescribed by clinicians based on the ability of the cushion to reduce pressure and provide proper positioning (Cooper et al., 1996). The primary goals being to reduce the risk of developing an ulcer and ensure adequate seated posture. The ability of a seating system to minimize impact (shock) and repetitive vibrations that an individual experiences is commonly not considered. Whole-body vibration experienced during wheelchair mobility can decrease an individual's comfort and increase the rate of fatigue (Boninger et al., 2003b; DiGiovine et al., 2000). This may adversely affect the physical performance of the individual. It may also lead to social inactivity. Shock and vibration induced discomfort and fatigue may also lead to poor body mechanics leading to secondary disability.

To date, little research has been conducted to assess the vibrations experienced by wheelchair users (Tai et al., 1998). VanSickle et al. recorded the forces when using the American National Standards Institute (ANSI)/Rehabilitation Engineering and Assistive Technology Society of North America (RESNA) standards double drum and curb drop tests and compared them to the road loads during ordinary propulsion (VanSickle et al., 1996, 2000). VanSickle et al. also showed that wheelchair propulsion produces vibration loads that exceed the ISO 2631-1 standards at the seat of the wheelchair as well as the head of the user (VanSickle et al., 2001). DiGiovine et al. (2000) showed that users prefer ultralight wheelchairs to lightweight wheelchairs while traversing a simulated road course with higher comfort level and better ergonomics. DiGiovine et al. (2003) examined the relationship between the seating systems for manual wheelchairs and the vibrations experienced, showing differences in how seating systems transmit or dampen vibrations. Foam and captured air cushions are best at attenuating the peak and average shocks and vibrations seen during actual wheelchair use. Wolf et al. (2001) concluded that, on average, suspension manual wheelchairs do reduce the transmission of shock vibrations to wheelchair users, but are not yet optimal in their design. Cooper et al. (2003b) have shown that in the natural frequency of humans (4-15 Hz) the addition of suspension caster forks do reduce the amount of vibrations transferred to the user. Wolf et al. (2002) have shown that suspension manual wheelchairs are approaching significance in reducing the amount of shock vibrations transmitted to wheelchair users during curb descents. Kwarciak et al. (2002) revealed that although suspension manual wheelchairs reduce shock vibrations the chairs are not yet ideal, possibly due to the orientation of the suspension elements.

Dobson et al. (2003) and Wolf et al. (2003) conducted evaluations of the vibration exposure during electric-powered wheelchair driving and manual wheelchair propulsion over selected sidewalk surfaces. Their results indicate that all surfaces with an 8 mm gap or less between components surfaces yielded results that were similar to the poured concrete sidewalk, and should be considered acceptable as a pedestrian access route for wheelchair users.

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Dealing With Back Pain

Dealing With Back Pain

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