Effect of rear suspension and speed on seat forces and head accelerations experienced by manual wheelchair riders with spinal cord injury

Abstract

Abstract-Whole-body shocks and vibrations experienced during manual wheelchair use can decrease an individual's comfort, increase the rate of fatigue, result in injury, and consequently limit mobility and community participation. We used a wheelchairvibration simulator to examine whether the seat reaction forces experienced by wheelchair users were differentially influenced by wheelchair suspension, trunk-muscle innervations, and ground speed. We used wheelchairs instrumented with load cells and accelerometers to determine the forces transmitted from the seat frame and the head accelerations experienced by riders. We determined that self-selected speed, seat force, and head accelerations differed between subjects with and without trunk-muscle innervations and between rigid and suspension wheelchairs. Seat force and head accelerations were greatest in the rigid-frame wheelchair and lowest in the spring-type suspension-frame wheelchairs. Those participants without trunk-muscle innervations preferred slower speeds than those with trunk-muscle innervations. Forward head accelerations were greater in those without than with trunk-muscle innervations. Wheelchair rear-suspension systems may improve wheelchair mobility function in terms of comfort at higher velocity by minimizing the seat forces and head accelerations experienced by the riders, especially those with higher level spinal cord injury and diminished postural control.

Changes in surface electromyography signals and kinetics associated with progression of fatigue at two speeds during wheelchair propulsion

“…Fourteen nondisabled participants (7 males, 7 females, mean age 30 ± 4 years [range [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] …”

“…The slow speed, 0.9 m/s, was selected because it is close to minimally safe speed (1.06 m/s, the speed required to cross a street with a timed light) [27]. Self-selected speeds for propulsion on a level surface have been reported from 0.8 to 1.6 m/s [27][28][29]. The upper limit, 1.6 m/s, was selected to present a challenging and strenuous situation for the participants.…”

Effect of Rear Wheel Suspension on Tilt‐in‐Space Wheelchair Shock and Vibration Attenuation

“…The magnitudes of unweighted peak acceleration R1 and R2 were similar, but there was only a significant decrease with the use of suspension while traversing the door threshold in unweighted peak acceleration R1. This potentially indicates collecting single peak accelerations, regardless of which wheel and where the wheel is during the traverse as in previous research [8,17,18,21], may mask some of the benefits of rear wheel suspension as there are multiple high-magnitude shocks when traversing obstacles.…”

“…This could potentially decrease the user's risk of the pain and discomfort associated with improper postures. One study investigating rear wheel suspension for self‐propelled manual wheelchairs found that subjects with higher spinal cord injuries and less postural control self‐selected faster speeds (suggesting suspension provided a smoother ride and increased user comfort) and saw the greatest reductions in forces and accelerations [8]. For tilt‐in‐space wheelchair users, especially nonverbal users unable to vocalize if they are no longer in a comfortable position, who do not have control over their speed and have less postural control, having the QuadshoX suspension reducing accelerations at the rear wheel may improve comfort as well as decrease health risk.…”

“…Some secondary health conditions may be induced by repeated shock and vibration exposure. Instantaneous peak acceleration, or shock, and wholebody vibration exposure has been correlated to low back pain, neck pain, muscle fatigue, early degeneration of the lumbar spine, herniated lumbar discs, and spinal discomfort and pain [3][4][5][6][7][8][9][10][11]. The International Organization for Standardization (ISO) established methods to quantify shock and whole-body vibration exposure and the risks associated with exposure in ISO 2631-1 [12].…”