Search

During this study a pushrim activated electric powered wheelchair was tested to published standards, compared to a manual wheelchair for metabolic energy consumption, and assessed by wheelchair users. The device performed favorably in nearly all cases.

This study compared wrist kinematics during manual wheelchair propulsion (MWP) for 22 experienced Manual Wheelchair Users (MWU) with and without evidence of median mononeuropathy (MMN), an indicator of CTS. Thirteen (13) MWUs tested positive for MMN. Analysis found significantly higher peak wrist flexion for MWU who demonstrated CTS via the nerve conduction study. It may be prudent to instruct MWUs to avoid extremes of wrist extension.

The electromyographic (EMG) activity of forearm muscles and pushrim forces were compared between a standard and an ergonomic wheelchair pushrim for a group of non-impaired subjects propelling at two and four miles per hour. The maximum EMG signals were not statistically different for any of the muscles between rims while significantly higher peak tangential, radial, and resultant forces were found for the ergonomic pushrims.

Wheelchair users are at an increased risk for developing carpal tunnel syndrome (CTS). The objective of this study was to use electromyography (EMG) to describe wrist flexor activity (WFA) during wheelchair propulsion. EMG data on 3 flexor muscles for one subject were collected while he propelled at a constant speed of 0.9 m/s (2 mph). The flexor carpi radialis was the most active flexor muscle during the push phase with peak and average EMG at 51% and 33% of its maximum isometric contraction value.

This study examines three different types (depot, lightweight, ultralight) of manual wheelchairs that have been tested to fatigue according to ISO standards. Results indicate that ultralight wheelchairs were significantly better than lightweight and depot with regard to fatigue life.

Due to the dynamic nature of MWP, motion analysis via markers placed on bony prominences provides the best approximation of the three dimensional trajectory of the segments of the upper extremity. Previous models which use motion analysis markers have been described in the literature, but these models have not corrected for positioning of the hand in a non-neutral position. The current model provides a standard method for determining the three ranges of motion commonly attributed to the wrist: flexion/extension, radial/ulnar deviation, and pronation/supination. These quantities are calculated via a local coordinate system based at the wrist as described by Shimada (1997), but applies a correction factor to account for non-neutral hand position during calibration.

The interface between the hand and pushrim may have considerable effect on many of the models related to wheelchair propulsion biomechanics. This has led to investigation of the center of pressure (COP), and the development of a new metric called the point of force application (PFA). The center of pressure is a virtual point of forces application which accounts for the measured forces and moments at the sensor. The point of force application (PFA) represents the weighted geometric mean of the distributed force. This simple proof shows that the PFA is equivalent to the COP in the sagittal plane, provided that the assumptions are valid. This case may be described as the "force platform equivalent" COP as the PFA makes the same assumptions and the resultant equations are of the same form.

The purpose of this paper is to describe the development and testing of a 3-D local coordinate system for assessing wrist biomechanics during wheelchair propulsion. Vectors centered at the ulnar styloid define planes of the wrist and thus flexion/extension, radial/ulnar deviation, and supination/pronation can be determined. The three predominant forces occurring during the propulsion phase are a shear force acting from radial to ulnar styloid, a shear force acting from palmar to dorsal surface, and a compressive force acting along the long axis of the wrist and forearm. The largest moment acts in the direction of ulnar deviation, not flexion or extension. This study demonstrates the importance of using a 3-D local coordinate space for assessing wrist kinetics during wheelchair propulsion and further work will provide insight into possible injury mechanisms.

There are limited interface options for electric powered wheelchairs, which results in the inability of some individuals to drive independently. In addition, the development of new interface technologies will necessitate the development of alternative training methods. This study compares a conventional position sensing joystick to a novel isometric joystick during a driving task in a virtual environment and a real environment. The results revealed that there were few differences in task completion time and root-mean-square error (RMSE) between the two types of joysticks. There were significant correlations between the RMSE in the virtual environment and the real environment for both types of joysticks. The data indicate that performance in the virtual environment was representative of driving ability in the real environment, and the isometric joystick performed comparably to the position sensing joystick.

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.

In order to send command signals to and collect data from a wheelchair during propulsion, an infrared data communication system was designed. The digital data from the SMART/sup Wheel/ goes to the transmitter attached to the wheel and is transmitted at a data rate of 38.4 kbps. The receiver gets the data at a distance of 6 meters and then the data is transmitted to the RS-232 serial port of a PC. The infrared chip set acts as a transceiver, so the command signal can also be sent to the SMART/sup Wheel/.

The incidence of upper extremity injuries among wheelchair users is higher than the general population. The high incidence of injury has been attributed to the high impact forces and repetition motions associated with propelling a wheelchair. The purpose of this study was to determine if using gloves could reduce injurious pushrim forces and moments. Seven experienced wheelchair users were instructed to push their personal wheelchair at 1.8 m/s with a SMART/sup Wheel/ attached. The subjects propelled the wheelchair under two conditions: (1) with gloves, and (2) without gloves. Mean peak F/sub z/, F/sub r/, F/sub t/, M/sub z/, and mechanical efficiency values were calculated for each subject for 10 consecutive strokes. A pair t-test was utilized in order to determine if significant differences exist in force, moment, and mechanical efficiency values between the two conditions. Significantly larger F/sub t/ and M/sub z/ values were found when gloves were used. A trend towards increased mechanical efficiency was also observed when gloves were used. No significant differences were found in all other force measures between the two conditions. The authors conclude that the use of gloves is advantageous to the user by increasing the forces and moments responsible for forward motion of the wheelchair.

Many investigators have examined pushrim forces and moments and joint kinetics during wheelchair propulsion, but rarely are start-up kinetics performed in the analysis. Kinetic data were collected as nine spinal cord injured experienced wheelchair users propelled their wheelchairs with instrumented pushrims on a stationary dynamometer. The subjects pushed from rest to at least 1.8 meters/second (m/s) for 20 seconds. A paired t-test was used to determine significant differences between steady state propulsion and start-up propulsion. Significant increases (p

The SMART/sup HUB/ and SMART/sup CASTOR/ are two new strain-gage based sensors designed to measure the reaction forces and moments at the rear axle and castor spindle, respectively. Both are five degree-of-freedom sensors, which measure all three force components and the two moment components perpendicular to the axes of rotation. These sensors will be used to improve wheelchair designs by allowing advanced engineering techniques such as finite element analysis to be applied with greater confidence. Both sensors are highly linear. When calibrated the lowest correlation coefficient was 0.9965 (N=21) and the cross-axes sensitivity was always less than 5%. Preliminary data are presented for two wheelchair users propelling over an indoor course and a non-wheelchair user traversing an outdoor course. The indoor data was transferred from a microcontroller-based signal conditioning board to a host PC through a high-speed serial port. For the outdoor data, the microcontroller was programmed to sample the data and to generate a histogram of force and moment frequencies, which was subsequently downloaded.

Stand-up wheelchairs are becoming more popular among clinicians and consumers. This is due to the expected physiological, psychological and functional benefits of stand-up wheelchairs. However, little is known about the biomechanical and clinical aspects of stand-up wheelchairs. This poses a substantial risk to stand-up wheelchair users. This paper presents a model for examining knee forces, knee-block forces, seat shear forces, and backrest shear forces. The model shows that substantial forces can occur at the user's knee and wheelchair's knee-block. These forces must be properly aligned and distributed to prevent injury to the structures of the knee and lower leg.

The development and use of stand-up wheelchairs have become increasingly popular due to consumers becoming more aware of the benefits that passive wheelchair standing may provide. The purpose of this study was to evaluate the upper extremity kinematic differences between standing and sitting wheelchair propulsion. The kinematic analysis involved calculating joint angles and displacements. There were no distinct differences found between the starting and ending joint angles and joint excursions when the four propulsion conditions were compared. The study did not conclusively find kinematic differences between stand-up and standard wheelchair propulsion due to large variations in joint angles and displacements.

Wheelchair locomotion is an important form of mobility for many individuals with spinal cord injury. However, manual wheelchair propulsion can lead to upper-limb pain and can be very inefficient. This has led investigators to apply biomechanics to the study of wheelchair use. The objectives of this study were (1) to determine the frequency content of the motion of both hands during two speeds of wheelchair propulsion, (2) to obtain the filter frequencies necessary to remove noise from wheelchair motion data, and (3) to provide signal-to-noise ratio data for wheelchair kinematics. The participants in this study were a random sample of manual wheelchair users with paraplegia caused by spinal cord injury. Subjects propelled their personal wheelchairs on a computer-controlled dynamometer at speeds of 0.9 m/s and 1.8 m/s. Motion data were collected at 60 Hz with the use of a commercial infrared marker-based system. The main outcome measures were arm motions and noise frequency spectra, filter cutoff frequencies, and signal-to-noise ratio. Our results indicate that there is no useful signal power above 6 Hz during manual wheelchair propulsion at the speeds that we analyzed. In many cases, there was no useful signal power above 4 Hz. This would indicate that the frequency content of manual wheelchair propulsion is similar to that of human gait. The mean signal-to-noise ratio varied from a high of 91 dB to a low of 21.8 dB. The signal-to-noise ratio was greatest in the x direction (along the line of progression) and lowest in the z direction (medial-lateral). Manual wheelchair propulsion kinematic data should be low-pass filtered at approximately 6 Hz for speeds at or below 1.8 m/s. The data presented in the archival literature appear to have been filtered at an appropriate frequency.

There is a growing body of research related to prescription of mobility devices. This research enables clinicians and clients to make clinical decisions related to mobility based on sound research. Unfortunately, there is little research investigating appropriate prescriptions in degenerative disorders such as multiple sclerosis (MS). In this article we will review the literature on mobility devices in MS and how it can be used to assist with clinical decision-making considering the progressive nature of this condition. In addition, we will review other research not conducted on individuals with MS that is relevant to this population. Finally we will present a call for future research that should help address this critical area.

Boninger ML, Souza AL, Cooper RA, Fitzgerald SG, Koontz AM, Fay BT. Propulsion patterns and pushrim biomechanics in manual wheelchair propulsion. Arch Phys Med Rehabil 2002;83:718-23. Objectives: To classify stroke patterns of manual wheelchair users and to determine if different patterns of propulsion lead to different biomechanics. Design: Case series. Setting: Biomechanics laboratory. Participants: Thirty-eight individuals with paraplegia who use manual wheelchairs for mobility. Intervention: Subjects propelled their own wheelchair on a dynamometer at 2 different steady state speeds. Bilateral biomechanical data were obtained by using a force and moment sensing pushrim and a motion analysis system. Main Outcome Measures: The propulsive stroke of each participant for each speed and side was classified as following 1 of 4 patterns. These 4 patterns were then compared by using a mixed-model analysis of variance. The biomechanical variables that were compared were cadence, peak and rate of rise of the resultant force, mechanical effective force, push angle, and ratio of time spent pushing to time in recovery. Results: The most common propulsive stroke involved the user lifting the hand over the pushrim during the recovery phase. The stroke pattern was independent of axle position and varied from side to side and between speeds. After controlling for subject characteristics, significant differences were observed between stroke patterns in cadence and ratio of time spent pushing to time in recovery. A stroke pattern that involves using a semicircular motion with the hand below the pushrim during the recovery phase of the propulsion stroke was associated with a lower cadence and more time spent in the push phase relative to the recovery phase. Conclusion: The semicircular motion of propulsion displayed characteristics consistent with reduced repetition and more efficient propulsion. Use of this propulsion style may reduce trauma to the upper extremities. Clinicians should consider training individuals in this propulsion style. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

The objective of this study was to quantify the difference in mechanical efficiency and user power generation between traditional manual wheelchairs and a pushrim activated power assisted wheelchair (PAPAW). Ten manual wheelchair users were evaluated in a repeated measures design trial with and without the PAPAW for propulsion efficiency. Subjects propelled a Quickie GP equipped with the PAPAW and their own chair on a computer controlled wheelchair dynamometer at five different resistance levels. Power output, user power with the PAPAW hubs, subjects' oxygen consumption per minute and mechanical efficiency were analyzed. Metabolic energy and user power were significantly lower (p

Fitzgerald SG, Cooper RA, Boninger ML, Rentschler AJ. Comparison of fatigue life for 3 types of manual wheelchairs. Arch Phys Med Rehabil 2001;82:1484-8. Objectives: To examine 3 types of manual wheelchairs—ultralight wheelchairs (UWs), lightweight wheelchairs (LWs), and depot wheelchairs (DWs)—and to compare the fatigue life between the wheelchair types. Design: A database of different manual wheelchairs tested according to the International Organization for Standardization (ISO). Fatigue life was determined by using standards that define methods accepted internationally using double-drum and curb-drop testing equipment. Setting: A rehabilitation engineering center. Specimens: Sixty-one manual wheelchairs: 25 DWs, 22 UWs, and 14 LWs. Main Outcome Measures: Wheelchairs were examined for differences in fatigue life based on equivalent cycles. Unique survival curves were fit and compared for each wheelchair type. Results: The UWs lasted the longest, with a mean of 309,362 equivalent cycles. The DWs faired the worst, with a mean of 117,210 equivalent cycles. The Kaplan-Meier survival curves were significantly different ( p Conclusion: Fatigue life for UWs is significantly greater ( p © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Due to the high incidence of secondary wrist injury among manual wheelchair users, recent emphasis has been placed on the investigation of wheelchair propulsion biomechanics. Accurate representation of wrist activity during wheelchair propulsion may help to elucidate the mechanisms contributing to the development of wrist injuries. Unfortunately, no consensual wrist biomechanical model has been established. In order to determine if different methodologies obtain similar results, this investigation created and compared three different wrist models: 1) a fixed joint center placed between the styloids (midstyloid joint center); 2) a joint center with 2/spl deg/ of freedom computed from de Leva's joint center data; and 3) a floating joint center. Results indicate that wrist flexion and extension angles are highly consistent between models, however, radial and ulnar deviation angles vary considerably. Mean maximum right flexion angles were found to be 3.5/spl deg/, 2.2/spl deg/, and 5.0/spl deg/ for the midstyloid, de Leva, and floating joint center models, respectively. Extension angles were 22.3/spl deg/, 23.6/spl deg/, and 23.6/spl deg/, respectively. Mean maximum right radial deviation angles for the midstyloid, de Leva, and floating joint center models were 26.0/spl deg/, 26.9/spl deg/, and 45.1/spl deg/, respectively, and ulnar deviation angles were found to be 30.5/spl deg/, 38.8/spl deg/, and 10.2/spl deg/, respectively. This information is useful when comparing kinematic studies and further supports the need for consensual methodology.

The Accreditation Council for Graduate Medical Education includes training in research as a required component of physical medicine and rehabilitation residency programs. Unfortunately, there is a lack of practical information on how to meet this requirement. In this paper, information is provided for individuals involved in resident education on how to teach residents about research.

A barrier to performing more in-depth analyzes during the wheelchair design process is a lack of dynamic reaction force and moment data, and the instrumentation to collect this data. Instrumentation was developed to collect the dynamic force and moment data. New data collections methodologies and analysis techniques were implemented to facilitate computer-aided-engineering for wheelchair designs. Data were collected during standardized wheelchair fatigue tests, while driving over a simulated road course within a laboratory, and while driving in the community. Seventeen subjects participated in this study. Based upon the three test conditions, a pseudo-statistical distribution of the force and moment data at both a caster and rear wheel was developed. The key parameters describing the distribution and the extremums of the data (minima and maxima) were compared using analysis of variance. The results showed that the force and moment distributions and extreme values were similar for the both sets of human trials (i.e., simulated road course and field trials). However, the standardized testing (i.e., wheelchair fatigue testing) differed from both human trials. The force/moment data gathered during this study are suitable for inputs in finite element analysis and dynamic modeling. The authors' results suggest that the fatigue tests should be modified to change the magnitude and increase the frequency of the forces and moments imparted on the wheelchair. The data reported from this study can be used to improve wheelchair standards and to facilitate computer-aided-engineering in wheelchair design.

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.

Boninger ML, Baldwin M, Cooper RA, Koontz A, Chan L. Manual wheelchair pushrim biomechanics and axle position. Arch Phys Med Rehabil 2000;81:608-13. Objective: The biomechanics of wheelchair propulsion have been linked to upper extremity injury. Specifically, prior studies have correlated increased median nerve dysfunction with increasing propulsion frequency and a higher rate of rise of the resultant, or total, pushrim force. Despite this link, there is little research on the effect of wheelchair setup on propulsion biomechanics. The objective of this study was to determine the effect of rear axle position relative to the shoulder on pushrim biomechanics. Design: Case series. Setting: Biomechanics laboratory. Participants: Forty individuals with paraplegia who use manual wheelchairs for mobility. Intervention: Subjects propelled their own wheelchairs on a dynamometer at two different steady-state speeds and going from a dead stop to maximum speed. Bilateral biomechanical data were obtained using a force- and moment-sensing pushrim and a motion analysis system. Main Outcome Measures: Position of the axle relative to the shoulder at rest both horizontal (XPOS) and vertical (YPOS), and pushrim biomechanical variables including frequency of propulsion, peak and rate of rise of the resultant force, planar moment, and push angle. Partial correlation coefficients between relative axle position and propulsion biomechanics variables were calculated. Results: After controlling for subject characteristics, XPOS was significantly correlated with the frequency of propulsion ( p p p Conclusion: Specific biomechanical parameters known to correlate with median nerve injuries were found to be related to axle position relative to the shoulder. Providing wheelchair users with adjustable axle position and then fitting the user to the wheelchair can improve propulsion biomechanics and likely reduce the risk of injury. © 2000 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

DiGiovine MM, Cooper RA, Boninger ML, Lawrence BM, VanSickle DP, Rentschler AJ. User assessment of manual wheelchair ride comfort and ergonomics. Arch Phys Med Rehabil 2000;81:490-4. Objective: To examine wheelchair-user perceived ride comfort during propulsion and to compare the ride comfort of ultralight and lightweight manual wheelchairs. An ultralight wheelchair is defined as having a high degree of adjustability, whereas a lightweight wheelchair has minimal adjustability. Design and Participants: Repeated measures design of a sample of 30 community-dwelling manual wheelchair users evaluating 7 different manual wheelchairs over an activities of daily living course. Setting: A rehabilitation engineering center. Main Outcome Measures: Subject ratings of perceived ride comfort and basic ergonomics while propelling over the activities of daily living course. Ratings were recorded for each wheelchair on individual tasks and for the course overall. Results: The Invacare Action XT wheelchair was ranked best for both ride comfort and basic ergonomics. The ride-comfort scores ( p p Conclusion: There are differences in perceived ride comfort and basic ergonomics between the designs of the wheelchairs (lightweight vs ultralight). Subjects perceived that ultralight wheelchairs were more comfortable and had better basic ergonomics than lightweight wheelchairs. © 2000 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

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. At 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.

Objectives: To provide data for clinicians and wheelchair users to compare the durability, strength, stability, and cost effectiveness of four different ultralight wheelchair models, and to compare the results of this study with those published for lightweight wheelchairs. Design: Standards testing and cost-effectiveness analysis of four wheelchair models from different manufacturers (12 wheelchairs total). Results: There were significant differences ( p ≤ .05) in the fatigue life and value (equivalent cycles per dollar) among the ultralight wheelchairs tested. There was also a significant difference ( p ≤ .05) in rearward stability tilt angle for the least and most stable configurations. There were no differences in forward and lateral stability. The ultralight wheelchairs (1,009,108 cycles) had significantly ( p ≤ .05) higher fatigue lives than previously reported for lightweight wheelchairs (187,370 cycles). The lightweight wheelchairs had a mean value of 210 cycles per dollar compared to 673 cycles per dollar for the ultralight wheelchairs. The difference in value for the lightweight and ultralight wheelchairs was statistically significant ( p ≤ .05). Conclusion: There were differences in the fatigue life and value among the four models of ultralight manual wheelchairs tested. This indicates that ultralight manual wheelchairs are not all of equal quality. The fatigue life and value of the ultralight manual wheelchairs were significantly higher than those previously reported for lightweight manual wheelchairs. This indicates that ultralight wheelchairs may be of higher quality than lightweight manual wheelchairs. Clinicians and consumers should seriously consider selecting an ultralight manual wheelchair to meet their wheelchair mobility needs.

The measurement of the center of pressure (COP) has been and continues to be a successful tool for gait analysis. The definition of a similar COP for wheelchair propulsion. however, is not straightforward. Previously, a COP definition similar to that used in force plate analysis had been proposed. Unfortunately, this solution has the disadvantage of requiring a separate COP definition for each plane of analysis. A definition of the generalized center of pressure (GCOP) which is consistent in all planes of analysis is derived here. This definition is based on the placement of a force-moment system, equivalent to the force-moment system at the hub, on a line in space where the moment vector (wrench moment) is parallel to the force vector. The parallel force-moment system is then intersected with three planes defined by anatomical landmarks on the hand. Data were collected using eight subjects at propulsion speeds of 1.34 m/s and 2.24 m/s (1.34 m/s only for subject 1, 0.894 m/s and 1.79 m/s for subject 8). Each subject propelled a wheelchair instrumented with a SMARTwheel. A PEAK 5 video system was used to determine the position of anatomical markers attached to each subject's upper extremity. The GCOP in the transverse plane of the wrist formed clusters for all subject's except subject 2 at 1.34 m/s. The clustering of the GCOP indicates that the line of action for the force applied by the hand is approximately perpendicular to the transverse plane through the wrist. When comparing the magnitude of the moment vector part of the wrench with the moment of the force vector of the wrench about the hub, the wrench moment is approximately an order of magnitude smaller. This indicates that the role of the wrist for wheelchair propulsion is primarily to stabilize the force applied by the arm and shoulder.

Wheelchair propulsion kinetic measurements require the use of custom pushrim force/moment measuring instruments which are not currently commercially available. With the ability to measure pushrim forces and moments has come the development of several dynamic metrics derived for analyzing key aspects of wheelchair propulsion. This paper presents several of the equations used to calculate or derive the primary variables used in the study of wheelchair propulsion biomechanics. The uncertainties for these variables were derived, and then numerically calculated for a current version of the SMART/sup Wheel/. The uncertainty results indicate that the SMART/sup Wheel/ provides data which has better than 5 to 10% uncertainty, depending upon the variable concerned, at the maximum, and during most of the propulsion phase the uncertainty is considerably smaller (i.e. approximately 1%). The uncertainty analysis provides a more complete picture of the attainable accuracy of the SMART/sup Wheel/ and of the degree of confidence with which the data can be recorded. The derivations and results indicate where improvements in measurement of wheelchair propulsion biomechanical variables are likely to originate. The most efficient approach is to address those variables in the design of the system which make the greatest contribution to the uncertainty. Future research will focus on the point of force application and examination of nonlinear effects.

To investigate pushrim forces and joint kinetics during wheelchair propulsion and to discuss the differences between inexperienced and experienced wheelchair users.Cohort study.Human engineering laboratory at a state university.Four men who use manual wheelchairs for mobility and four nondisabled men who did not have extensive experience pushing a wheelchair; all subjects were asymptomatic for upper extremity pain or injury.Subjects pushed a commonly used wheelchair fitted with a force-sensing pushrim on a stationary wheelchair dynamometer. Video and force data were collected for 5 strokes at one speed of propulsion. Pushrim forces and net joint forces and moments were analyzed.Pushrim forces, radial (Fr) and tangential (Ft), were analyzed and compared for both groups in relation to peak values and time to peak values and as ratios of overall forces generated. Net joint forces and moments were analyzed in a similar fashion.Pushrim forces and joint moments were similar to those previously reported, with radial forces averaging between 34 and 39N and tangential forces ranging on average between 66 and 95N. Tangential forces were higher than radial forces, and mean ratios of tangential forces to the resultant force were approximately 75%, whereas mean radial force ratios were approximately 22%. All subjects showed higher joint moments at the shoulder than at the elbow or wrist. A large component of vertical reaction force was seen at the shoulder. Significant differences (p.05) were found between groups for peak tangential force and time to peak tangential and peak vertical forces, with wheelchair users having lower values and longer times to reach the peak values.Discrete variables from the force-time curves can be used to distinguish between wheelchair users and nonusers. The experienced users tended to push longer, used forces with lower peaks, and took longer time to reach peak values. This propulsive pattern may have been developed to reduce the chance of injury by minimizing the forces at the joints, as a means of maximizing efficiency or as a combination of these factors. More work investigating 3-dimensional forces and the influence of seating position and various conditions of propulsion such as speed changes, ramps, and directional changes on injury mechanisms needs to be completed.

Evidence suggests that wheelchair (WC) users are exposed to unhealthy levels of vibration during WC use. Health risks associated with vibration exposure include vertebral disc degeneration and back pain, which may consequently decrease the function and independence of WC users. Some evidence suggests that the cushions used in WCs may amplify vibrations, although conclusive evidence has not been presented in the literature. This study evaluated and compared the transmissibility of commercially available WC cushions with two laboratory test methods: (1) direct measurement of transmissibility while human subjects propelled a WC over a road course with different cushions and (2) characterization of cushions with a material testing system (MTS) combined with mathematical models of the apparent mass of the human body. Results showed that although dynamic characterization of WC cushions is possible with an MTS, the results did not correlate well with the transmissibility obtained in the WC road course. Significant differences were found for transmissibility among the cushions tested, with the air-based cushions having lower transmissibility than the foam- or gel-based cushions.

This study describes a new custom measurement system designed to investigate the biomechanics of sitting-pivot wheelchair transfers and assesses the reliability of selected biomechanical variables. Variables assessed include horizontal and vertical reaction forces underneath both hands and three-dimensional trunk, shoulder, and elbow range of motion. We examined the reliability of these measures between 5 consecutive transfer trials for 5 subjects with spinal cord injury and 12 non-disabled subjects while they performed a self-selected sitting pivot transfer from a wheelchair to a level bench. A majority of the biomechanical variables demonstrated moderate to excellent reliability (r > 0.6). The transfer measurement system recorded reliable and valid biomechanical data for future studies of sitting-pivot wheelchair transfers. We recommend a minimum of five transfer trials to obtain a reliable measure of transfer technique for future studies.

Returning wounded veterans and servicemembers to their highest level of function following traumatic injury is a priority of the Departments of Defense and Veterans Affairs. We surveyed 245 veterans from the Vietnam war and 226 servicemembers and veterans from Operation Iraqi Freedom/Operation Enduring Freedom (OIF/OEF) conflicts with at least one major traumatic lower-limb loss to determine their use of mobility assistive technology (AT) and patterns of limb abandonment. Prosthetic device use without wheelchair use is found in 50.5% of Vietnam and 42.8% of OIF/OEF groups. Prostheses and supplementary wheelchairs are used by Vietnam (32%) and OIF/OEF (53%) groups (p < 0.01). Exclusive wheelchair use is more frequent in the Vietnam group (18%) than in the OIF/OEF group (4.0%, p < 0.01). In Vietnam participants, multivariate analysis found that multiple-limb loss (adjusted odds ratio [AOR] = 14.5; 95% confidence interval [CI] 5.5-38.5), bilateral lower-limb loss (AOR = 12.7; 95% CI 6.2-26.1), and number of comorbidities (AOR = 1.3; 95% CI 1.2-1.5) are associated with increased likelihood of wheelchair use. In OIF/OEF participants, bilateral lower-limb loss (AOR = 29.8; 95% CI 11.0-80.7), multiple-limb loss (AOR = 16.3; 95% CI 3.1-85.3), cumulative trauma disorder (AOR = 2.4; 95% CI 1.2-4.9), and number of combat injuries (AOR = 1.4; 95% CI 1.2-1.7) are associated with wheelchair use. Combined use of different types of mobility ATs promotes improved rehabilitation and ability to function.

This study's main objective was to determine if upper-limb (UL) muscular demand was reduced when individuals with a spinal cord injury (SCI) performed a sitting pivot transfer (SPT) in the preferred direction compared with that in a nonpreferred direction. Fourteen individuals (mean +/- standard deviation age 47.0 +/- 8.3 yr, height 1.80 +/- 0.08 m, and weight 75.3 +/- 11.3 kg) with SCI levels ranging from the sixth cervical to first sacral vertebra levels volunteered to participate in this study during the 2008 National Disabled Veterans Winter Sports Clinic. Surface electromyography (EMG) was used to record activity of the biceps, triceps, deltoid, pectoralis major, trapezius, and latissimus dorsi bilaterally during SPTs. These transfers were performed in each of the preferred and nonpreferred directions from the individuals' wheelchairs to a padded tub bench of even height. To quantify electromyographic muscular utilization ratio (MUR(EMG)), we normalized EMG data recorded during the transfer tasks to values obtained during static maximum voluntary contraction and then multiplied this ratio by 100 to obtain a percentage MUR(EMG) (%MUR(EMG)). The overall peak %MUR(EMG) and the area under the %MUR(EMG) curve were selected as primary outcome measures. Similar peak %MUR(EMGs) were found between the preferred and nonpreferred transfer directions for all muscles from which data were recorded (p = 0.053 to 0.961). The peak %MUR(EMGs) were also found to be similar between the leading and trailing ULs during the transfers in all muscles from which data were recorded (p = 0.125 to 0.838), except for the anterior deltoid, which was found to be solicited the most in the trailing UL (p = 0.008). Comparable areas under the %MUR(EMG) curves were calculated between the preferred and nonpreferred transfer directions for all muscles (p = 0.289 to 0.678) and between the leading and trailing ULs (p = 0.104 to 0.946). These results indicate that direction preference expressed by individuals with SCI when transferring between seats of even height is not explained by relative muscular demand differences.

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.

Individuals with multiple sclerosis (MS) report decreased satisfaction with their mobility devices compared with individuals with spinal cord injuries (SCIs). This study (1) investigated the demographic differences between veterans with MS (V-MS) and veterans with SCI (V-SCI) who were issued a wheelchair by the Veterans Health Administration (VHA) and (2) described differences in mobility device prescription. We merged two VHA databases to obtain demographic and wheelchair information for all V-MS and V-SCI in 2000 and 2001. Descriptive information for issued wheelchairs was available for 2,154 V-MS and V-SCI. We found that V-MS were significantly less likely to receive higher quality wheelchairs (manual or power) compared with V-SCI (p < 0.001). The disparity in VHA wheelchair prescription between these two groups indicates a need for further research regarding the assistive device prescription process in these populations.

Yu-Sheng Yang, PhD, Alicia M. Koontz PhD, RET, Ronald J. Triolo PhD, Rory A. Cooper, PhD, Michael L. Boninger MD. Human Engineering Research Laboratories, VA Medical Center, Pittsburgh, PA, USA Cleveland FES Center, Louis Stokes Cleveland VA Medical Center, Cleveland OH, USA Department of Occupational therapy, Kaohsiung Medical University, Kaohsiung City, Taiwan email:yusheng@kmu.edu.tw, web: www.ot.kmu.edu.tw

During fiscal years 2000 and 2001, the Veterans Health Administration provided veterans with more than 131,000 wheelchairs and scooters at a cost of $109 million. This national study is the first to investigate Veterans Health Administration costs in providing wheelchairs and scooters and to compare regional prescription patterns. With a retrospective design, we used descriptive methods to analyze fiscal years 2000 and 2001 National Prosthetics Patient Database data (cleaned data set of 113,724 records). Wheelchairs were categorized by function, weight, and adjustability options for meeting individual needs (e.g., axle position, camber, position of wheels, tilt, and recline options). Results displayed a cost distribution that was negatively skewed by low-cost accessories coded as wheelchairs. Of the standard manual wheelchairs, 3.5% could be considered beyond the customary cost. Regionally, 71% to 86% of all wheelchairs provided were manual wheelchairs, 5% to 11% were power wheelchairs, and 5% to 20% were scooters. The considerable variation found in the types of wheelchairs and scooters provided across Veterans Integrated Service Networks may indicate a need for evidence-based prescription guidelines and clinician training in wheeled-mobility technologies.

Little is known about the reasoning process clinicians use when prescribing wheeled mobility equipment (WME) or about the outcomes of this process, i.e., how many devices are prescribed, to whom, how often, and at what cost. This study characterized veterans who received WME from the Veterans Health Administration. We analyzed variance in wheelchair provision based on sex, race/ethnicity, diagnosis, and age. Three years of data from the National Prosthetics Patient Database and the National Patient Care Database were merged, yielding more than 77,000 observations per fiscal year. Logistic regression analysis revealed associations between WME provision and age, sex, and race/ethnicity, when analysis was controlled for diagnosis and number of comorbidities. Hispanics (odds ratio [OR] = 1.864), African Americans (OR = 1.360), and American Indians/Asians (OR = 1.585) were more likely than Caucasians to receive standard wheelchairs. Hispanics (OR = 0.4), African Americans (OR = 0.7), and American Indians/Asians (OR = 0.4) were less likely than Caucasians to receive scooters.