Carmen P. DiGiovine

Multisite comparison of wheelchair propulsion kinetics in persons with paraplegia

A multisite collaborative study is being conducted on the association between propulsion biomechanics and upper-limb injuries. This substudy compared subject characteristics and pushrim kinetics across three sites and identified early on in the main study any differences that could affect interpretation of the findings or data pooling. A total of 42 manual wheelchair users with paraplegia (14 from each site) performed 0.9 m/s and 1.8 m/s steady state propulsion trials and an acceleration-brake-coastdown trial on a wheelchair dynamometer while propulsion forces and moment about the hub were measured with a SmartWheel. Significant differences between two sites were found in peak and average resultant force (p < 0.05), peak and average moment at the slower steady state speed (p < 0.005), and peak and average torque at the faster steady state speed (p = 0.06). Subjects at the site with significantly lower forces and torques had a slower deceleration rate during coastdown compared with the subjects at the other two sites (p < 0.001). These results imply that rolling resistance is lower at one of the sites and likely due to differences in dynamometer properties. A mechanical method was used to site-normalize the data and enable data pooling for future analyses.

Whole-body vibration during manual wheelchair propulsion with selected seat cushions and back supports

Although the exposure to whole-body vibrations (WBV) has been shown to be detrimental to seated humans, the effects of wheelchairs and seating systems on the transmission of vibration to an individual have not been thoroughly examined. The purpose of this study was to determine if the selected wheelchair seat cushions and back supports minimize the transmission of vibrations. Thirty-two wheelchair users traversed an activities of daily living course three times using 16 randomly selected seating systems as well as their own. Vibrations were measured using triaxial accelerometers at the seat and participants head. The weighted fore-to-aft (T/sub x/), vertical (T/sub z/), and resultant (T/sub r/) transmissibility based on the vibrational-dose-value (VDV) were used to determine if differences existed among the four seat cushions and back supports. The obstacles that seem to have the largest effect on the transmission of WBV are the single event shocks and the repeated event shocks. Comparisons between the individuals own seating system and the tested seating systems suggest that the individuals are not using the most appropriate seating system in terms of the reduction of vibration transmission.

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.

Frequency analysis of kinematics of racing wheelchair propulsion

The purpose of this study was to describe the frequency content of racing wheelchair propulsion motion data. The selection of the filter corner frequency in previous kinematic analyses of manual wheelchair propulsion was commonly based on gait literature. An estimate of the frequency separating the signal and the noise was determined to make recommendations for low-pass digital filters. The global (noncoordinate specific) cutoff frequency was 6 Hz. The directional cutoff frequencies were 5.1, 3.9, and 5.6 Hz, in the anterior-posterior, superior-inferior and medial-lateral directions, respectively. Recommendations for the corner frequencies of low-pass Butterworth digital filters based on the cutoff frequency are higher than the corner frequencies used in previous studies of manual wheelchair propulsion kinematic data. This study provides a foundation for the data reduction of manual wheelchair propulsion kinematic data that is independent of gait literature.

Modeling and analysis of a manual wheelchair coast down protocol

The purpose of the paper is to mathematically model a manual wheelchair on a dynamometer and flat tile floor respectively, using a simplified version of R.A. Coopers model (J. Rehabil. Res. Dev., vol. 27, no. 2, p. 151-62, 1990). Then the model is compared to measured data from coast down trials using the pearson-product correlation coefficient. Using a 2nd order polynomial to model the rear wheel angular position as a function of time we obtained pearson-product correlation coefficients which ranged from 0.9988 to 1.0000 with a mean of 0.9998. From the 2/sup nd/ order polynomial the authors were able to measure the friction torque which was used to compare the dynamometer to a flat tile floor. The friction torque for the dynamometer and the poor were significantly different for both sides when compared using analysis of variance with a significance value of 0.05. Therefore, a braking system should be added to the dynamometer in order to increase the dynamometer friction torque in order to match that of the flat tile floor. The normalized difference of the side to side friction torque for the dynamometer and the floor were not significantly different. This suggests that the side to side friction torque differences are due to the user and wheelchair setup not the dynamometer.

Advances in Manual Wheelchair Technology

The manual wheelchair has undergone much advancement over the past two decades. The purpose of this article is to provide an overview of the most significant advances in manual wheelchairs. These technological advances are now available in the clinical setting and should be recognized, discussed, and adopted by doctors, clinicians, engineers, funding sources, and, most important, consumers when the most appropriate manual wheelchair is being selected.

Fatigue-life of two manual wheelchair cross-brace designs

OBJECTIVE To compare the durability of two designs of cross-braces for folding manual wheelchairs and to determine the nature of wheelchair cross-brace failures. DESIGN Fatigue testing of two folding wheelchair cross-brace designs (one with a rectangular cross-section and the other with a circular cross-section). A total of 20 cross-brace pairs were tested. RESULTS The cross-braces with a circular cross-section endured a mean +/- SD of 100,159 +/- 45,814 cycles before experiencing a fatigue failure, whereas the cross-braces with a rectangular cross-section endured an average of 261,254 +/- 160,741 cycles. A t test showed significant differences (p = .01) in fatigue-life between cross-braces with a circular cross-section versus cross-braces with a rectangular cross-section. All 20 cross-braces experienced similar fatigue failures that would develop at the bolt hole where the two cross-braces connect to form a hinge. CONCLUSION The results suggest that the rectangular cross-brace design has a longer fatigue-life than the circular cross-brace design. People should regularly inspect the cross-brace for cracks. The area around the bolt forming the hinge should be inspected carefully. If a crack is observed, the cross-brace should be replaced immediately.

Comparison of absorbed power to vertical acceleration when measuring whole-body vibration during wheelchair propulsion

The purpose of this study was to examine the use of the absorbed power (AP) in describing whole-body vibration for individuals with a spinal cord injury (SCI) during manual wheelchair propulsion. The amplitude of the AP and the vertical acceleration were calculated in the frequency domain. The AP is more proficient than the acceleration metric at accentuating the frequencies related to whole-body vibration. The acceleration metric may be underestimating the amplitude of the vibration seen by an individual with a SCI especially at frequencies related to the natural frequency of the human body.

Digital filtering of kinematics of racing wheelchair propulsion

The purpose of this study was to examine the residual analysis technique described by D.A. Winter [1990] in the digital filtering of the kinematics of racing wheelchair propulsion. Specifically, the selection of the type and cut-off frequency of the digital filter were examined. The residual analysis was performed on the second metacarpophalangeal joint (2MP) marker. Four different types of digital filters were examined: a 2nd, a 4th, and a 10th order Butterworth, as well as a 10th order Chebyshev type I with a passband ripple of 0.001 dB. The residual analysis was useful in determining the appropriate cut-off frequency for each individual filter. The cut-off frequency was between 7 and 8 Hz in the x-direction, between 9 and 10 Hz in the y-direction, and 7 Hz in the z-direction, depending on the type and order of the filter implemented. The residual analysis was not useful in determining the appropriate type of filter. Knowledge regarding the magnitude and phase characteristics of the filter, as well as the type of data to be filtered, should be used to determine the most appropriate type of filter.