Inclusion of people with disabilities.
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Letter↗
Biomedical subjects
Rory A Cooper
Publications and source records attributed to Rory A Cooper.
Tips and falls during electric-powered wheelchair driving: effects of seatbelt use, legrests, and driving speed.
OBJECTIVE: To measure the response of a test dummy while traversing common obstacles encountered by users of electric-powered wheelchairs (EPWs) to determine whether optimal wheelchair fit, use of seatbelts, and driving speed affect the frequency and severity of EPW tips and falls. DESIGN: Repeated-measures comparison study. SETTING: Constructed environment both in and around a Veterans Affairs medical center. PARTICIPANT: A 50th percentile Hybrid II anthropometric test dummy (ATD) was used to simulate a person driving an EPW. INTERVENTIONS: The ATD was driven in 4 different EPWs over commonly encountered obstacles at speeds of 1 and 2m/s, with and without the use of a seatbelt, and at varying legrest heights. MAIN OUTCOME MEASURES: The response and motion of the ATD were observed and recorded as no fall, loss of control (the ATD falls forward or sideways but remains in the EPW), the ATD falls out of the EPW, or the EPW tips completely. RESULTS: A total of 97 adverse events out of 1700 trials were recorded: 88 were losses of control (instability) and 9 were ATD falls. No complete tips of any EPW occurred. Univariate statistical analysis indicated a significant relationship between the adverse events and the use of seatbelts, legrest condition, and test obstacles (P<.05). A mixed-model analysis confirmed the significant relationships between the adverse events and the use of seatbelts, legrest condition, and test obstacles (P<.05). However, the mixed model indicated that (1) there was no significant relationship between the adverse events and driving speed and (2) no one obstacle was designated to be the most problematic. CONCLUSION: Persons who use EPWs should use seatbelts and legrests while driving their EPWs, and clinicians should include common driving tasks when assessing the proper set-up of EPWs.
Acceleration↗
Seat and footrest shocks and vibrations in manual wheelchairs with and without suspension.
OBJECTIVE: To examine differences in the shock and vibration transmitted to an occupant of a manual wheelchair with and without suspension caster forks and with and without rear-suspension systems. DESIGN: Repeated-measures engineering testing. SETTING: Rehabilitation engineering center with a wheelchair standards test laboratory. SPECIMENS: Six manual wheelchairs. INTERVENTIONS: An American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society of North America wheelchair test dummy and a Hybrid III test dummy were used to test shock and vibration transmission in wheelchairs equipped with original equipment manufacturer (OEM) caster forks and suspension caster forks. Ultralight wheelchairs, half of which had factory-equipped rear-suspension systems, were tested. Testing was conducted on a double-drum wheelchair test machine. MAIN OUTCOME MEASURES: Shocks were examined by using peak acceleration and the frequency at which peak acceleration occurs for the seat and footrest. Vibration was characterized by the acceleration power per octave for the seat and footrest. RESULTS: Significant differences were found in the peak accelerations at the seat (P=.0004) and footrest (P=.0007) between the wheelchairs with the OEM caster forks and those with the suspension casters. The wheelchairs with suspension had significantly different frequencies at which the peak accelerations occurred for both the seat (P=.01) and footrest (P=.0001). The wheelchairs with suspension caster forks had a lower total power per octave than the wheelchairs with the OEM caster forks. For the footrest vibrations, significant differences were found between the types of caster forks for all octaves except those associated with frequencies more than 78.75Hz. There were significant differences for wheelchairs with and without rear suspension for total power per octave of seat vibrations in the octaves between 7.81 and 9.84Hz (P=.01) and 12.40 and 15.63Hz (P=.008). CONCLUSIONS: Suspension caster forks reduce the shock and vibration exposure to the user of a manual wheelchair. Rear-suspension systems reduce some of the factors related to shock and vibration exposure, but they are not clearly superior to traditional designs.
Acceleration↗
Shoulder magnetic resonance imaging abnormalities, wheelchair propulsion, and gender.
OBJECTIVE: To investigate the relationship between pushrim forces and the progression of shoulder injuries in manual wheelchair users. DESIGN: Longitudinal case series. SETTING: Biomechanics laboratory and magnetic resonance imaging (MRI) facility at a Veterans Health Administration medical center and university hospital, respectively. PARTICIPANTS: Fourteen individuals with spinal cord injury (8 men, 6 women) who used manual wheelchairs. INTERVENTION: Subjects propelled their own wheelchairs on a dynamometer at 0.9 and 1.8m/s. Bilateral biomechanical data were obtained by using force and moment sensing pushrims at time 1. Bilateral shoulder MR images were also completed on 2 occasions, at time 1 and, approximately 2 years later, at time 2. MAIN OUTCOME MEASURES: The peak pushrim forces in a pushrim coordinate system were calculated, weight normalized and averaged over 5 strokes (presented as % body weight). MRI abnormalities were graded by using a summated scale. Differences between scores between times 1 and 2 were calculated. RESULTS: Subjects were divided into 2 groups based on change in MRI score. Seven subjects were in the group with worsening scores (MRI+; mean, 8.14 points; range, 5-16), and 7 were in the group with improving or unchanging scores (MRI-; mean, -1.00 point; range, -5 to 1). There was no significant difference between groups with respect to age, body mass index, or years from injury. There were significantly more women in the MRI+ group (6 women, 1 man) than in the MRI- group (7 men) (P=.001). The MRI+ group used significantly greater weight-normalized radial force, or force directed toward the axle at time 1, to propel their wheelchairs at each speed (P<.01): MRI+ at 0.9m/s (mean radial force +/- standard deviation, 5.2%+/-1.0%) and MRI- at 0.9m/s (mean radial force, 3.2%+/-1.7%) (P=.028); and MRI+ at 1.8m/s (mean radial force, 6.6%+/-1.2%) (P=.023) and MRI- at 1.8m/s (mean radial force, 4.1%+/-2.2%). In a separate analysis, women were found to propel with a significantly higher radial force. A logistic regression found a significant relationship between radial force at time 1 and increased risk of progression of MRI findings over time. CONCLUSION: Individuals who propel with a greater percentage of force directed toward the axle were at increased risk of progression of MRI findings over time. Most people in this group were women. Clinicians should instruct wheelchair users in effective propulsion techniques and should pay particular attention to women who use wheelchairs. Reducing forces during wheelchair propulsion may minimize the likelihood of developing shoulder injuries.
Adult↗
Integrated control and related technology of assistive devices.
Assistive devices are now available that allow persons with severe physical disabilities to complete tasks independently. When the user has severe physical limitations, it may be advantageous to have an integrated control system where a single control interface (e.g., joystick, head switches, voice recognition system, keypad) is used to operate two or more assistive devices (e.g., power wheelchairs, augmentative communication devices, computers, environmental control units, and other devices that are controlled electronically). The advantages of integrated control are that persons with limited motor control can access several devices with one access site without assistance, and the user does not need to learn a different operating mechanism for each device. The purpose of this review is to convey the depth and breadth of the research that has been conducted on integrated control systems, as well as to provide some insights into future directions. We reviewed research works pertaining to communication and environmental control, computer access, and wheelchair guidance systems. Information gathered in this study will help people become fully aware of the status of contemporary integrated control technology in order to increase the quality of life of people who use electronic assistive devices.
Persons with Disabilities↗
Influence of wheelchair front caster wheel on reverse directional stability.
The purpose of this research was to study directional stability during reversing of rear-wheel drive, electric powered wheelchairs (EPW) under different initial front caster orientations. Specifically, the weight distribution differences caused by certain initial caster orientations were examined as a possible mechanism for causing directional instability that could lead to accidents. Directional stability was quantified by measuring the drive direction error of the EPW by a motion analysis system. The ground reaction forces were collected to determine the load on the front casters, as well as back-emf data to attain the speed of the motors. The drive direction error was found to be different for various initial caster orientations. Drive direction error was greatest when both casters were oriented 90 degrees to the left or right, and least when both casters were oriented forward. The results show that drive direction error corresponds to the loading difference on the casters. The data indicates that loading differences may cause asymmetric drag on the casters, which in turn causes unbalanced torque load on the motors. This leads to a difference in motor speed and drive direction error.
Computer Simulation↗
A pilot study on community usage of a pushrim-activated, power-assisted wheelchair.
Manual wheelchair propulsion combined with other stresses to the upper extremities may result in secondary injury. Possible solutions would be to devise alternative methods of propulsion, such as a pushrim-activated, power-assist wheelchair (PAPAW). The goals of this study were to examine the usage of the PAPAW in a real world setting and to characterize the driving habits of manual wheelchair users. Feedback was also obtained regarding subjects' opinions with respect to the PAPAW: their likes and dislikes. A PAPAW was provided to subjects for 2 weeks. Usage (average and total distance traveled and velocity) was tracked for both the PAPAW and the subjects' own wheelchairs. Significant differences in usage were not seen between the personal wheelchairs or the PAPAW. As a result, weeks were combined to provide an overall examination of driving characteristics. The average distance traveled over an average day was 1,671.4 +/- 314.8 m with an average velocity of 0.44 +/- 0.09 m/second. This pilot study provides an idea of manual wheelchair usage in a population of individuals with spinal cord injury. The lack of significant findings between the PAPAW and the subjects' own wheelchairs may be a function of study methodology such as sample size and length of follow-up in the new wheelchair. Future studies should expand upon the pilot work completed here, strengthening the design.
Adult↗
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.
Acceleration↗
Use of the Independence 3000 IBOT Transporter at home and in the community.
BACKGROUND: The INDEPENDENCE 3000 IBOT Transporter (IBOT) is an electronically stabilizing mobility device for people with disabilities. It operates in 4 functions: Standard, Balance (raised on 2 rear wheels), 4 Wheel (for inclines, curbs, and uneven terrain), and Remote (for loading into a vehicle). OBJECTIVE: The purpose of this study was to observe the IBOT at use in the home and in the community. METHODS: Data were obtained via observations by trained clinicians, data recorded from a computerized data logger, and reports from each expert. PARTICIPANTS: Participants included 10 unimpaired nonwheelchair users (6 men, 4 women) and 4 expert wheelchair users (men with spinal cord injuries, T7-L1). The participants used the IBOT to perform a variety of activities, including holding eye-level discussions with colleagues and shopping by balancing on 2 wheels, going up and down steep ramps, traversing outdoor surfaces (eg, grass, dirt trails), and climbing curbs. OBSERVATIONS: The Balance and 4-Wheel functions were helpful and worked well. The IBOT required attention to control in the Standard function. The seat height was too high for most tables and desks, and the IBOT was challenging to use in the bathroom. CONCLUSION: The IBOT is a functional mobility device that expands the options of wheelchair users. It is most useful outdoors and where there is sufficient space to use its unique Balance function.
Activities of Daily Living↗
Range of motion and stroke frequency differences between manual wheelchair propulsion and pushrim-activated power-assisted wheelchair propulsion.
BACKGROUND/OBJECTIVE: The objective of this study was to examine the use and efficacy of a pushrim-activated power-assist wheelchair (PAPAW) in the reduction of upper extremity range of motion (ROM) and stroke frequency in manual wheelchair users. METHODS: Ten manual wheelchair users were evaluated using a repeated-measures design with and without the use of a PAPAW for maximum ROM of shoulder flexion/extension, abduction/adduction, internal/external rotation, and horizontal flexion/extension; elbow flexion/extension; wrist flexion/extension, supination/pronation, and ulnar/radial deviation; and stroke frequency. Participants propelled a Quickie 2 manual wheelchair configured as a PAPAW and their own wheelchair on a computer-controlled dynamometer at 3 different resistance levels and 2 different speeds. RESULTS: The use of the PAPAW significantly (P < 0.05) decreased shoulder flexion/extension and horizontal flexion/extension, elbow flexion/extension, and wrist flexion/extension and ulnar/radial deviation for many speed and resistance combinations. Univariate analysis revealed that stroke frequency was unaltered in all cases. CONCLUSION: These findings provide the foundation for studying the utility of the PAPAW in reducing the risk of upper limb injury and neuropathy in the manual wheelchair user population.
Adult↗
Investigating neck pain in wheelchair users.
OBJECTIVE: Despite the fact that wheelchair users are exposed to risk factors for neck and upper back pain (NP), little is known about the impact and possible diagnoses associated with NP. The purpose of this study was to examine the significance of NP in wheelchair users and to determine if a portion of the NP may be myofascial in origin. DESIGN: Cross-sectional cohort study using questionnaires and physical exams to evaluate NP in a convenience sample of wheelchair users from the National Veteran's Wheelchair Games. Main outcome measures included reported NP, visual analog scale of neck complaints, Neck Disability Index, and physical examination findings of trigger points. RESULTS: Sixty-six percent of subjects reported NP since becoming a wheelchair user and, 60% reported pain during the past month. Neither age nor length of time in a wheelchair was significantly different between those subjects who did and those subjects who did not report pain. Of those respondents who reported NP, 60% visited the doctor about the pain and 40% limited their daily activities due to the pain. Trigger-point palpation reproduced pain in 54% of those respondents who experienced pain in the past month (n = 34). CONCLUSION: This study provides a first step in defining the prevalence and significance of NP among wheelchair users. Clinicians who work with this population need to ask subjects about symptoms and consider a myofascial origin for that pain when considering treatment.
Adult↗
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 participant's head. The weighted fore-to-aft (Tx), vertical (Tz), and resultant (Tr) 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.
Acceleration↗
Comparison of virtual and real electric powered wheelchair driving using a position sensing joystick and an isometric joystick.
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.
Algorithms↗
Wheelchair users are not necessarily wheelchair bound.
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Activities of Daily Living↗
Driving characteristics of electric-powered wheelchair users: how far, fast, and often do people drive?
OBJECTIVES: To determine the driving characteristics of electric-powered wheelchair users during unrestricted community activities and to compare the activity levels among an active group and a group of regular users. DESIGN: Multisite engineering evaluation of electric-powered wheelchair driving activity during unrestricted community mobility. SETTING: Data were collected in the communities of Pittsburgh, PA, and the National Veterans Wheelchair Games (NVWG) in San Antonio, TX. PARTICIPANTS: Seventeen people participated, all of whom used electric-powered wheelchairs as their primary means of mobility. INTERVENTION: Each subject was asked standarized questions about self and wheelchair use. Data logger and sensor installed on wheelchair. Data downloaded from logger. MAIN OUTCOME MEASURES: Speed, distance traveled, and the time that each subject's personal wheelchair was being driven were recorded for 24hr/d over approximately 5 days for each subject by using a custom-built data logger. RESULTS: The NVWG group traveled faster than the Pittsburgh group, but this difference was only statistically significant on the first day. The NVWG group was more likely to travel longer than the Pittsburgh group with significant differences seen in day 4 (P = .03) and day 5 (P = .05). Total distance traveled during the 5-day period and average distance traveled per day were also significantly different between the groups (P = .02 for both 5-day distance and daily distance), with the NVWG group traveling longer (17,164 +/- 8708m) when compared with the Pittsburgh group (8335 +/- 7074m) over the 5-day period. Both distance traveled and speed increased during afternoon and evening hours. The maximum distance traveled by any subject for each hour across the 2 groups was used to create the theoretic maximum distance day, which resulted in 7970m of driving. CONCLUSION: Drivers of electric-powered wheelchairs are most active during the afternoon and evening hours. Over the 5-day period of this study, there was little variation in the speed or distance driven per day. The subjects participating in the NVWG were more active than their counterparts during a typical week at home. The maximum theoretic distance that a wheelchair user in our group would travel is less than 8km. The range of current electric-powered wheelchairs appears adequate, if not generous, for the subjects in our study.
Activities of Daily Living↗
Propulsion patterns and pushrim biomechanics in manual wheelchair propulsion.
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.
Adult↗
Intelligent walkers for the elderly: performance and safety testing of VA-PAMAID robotic walker.
A walker that could help navigate and avoid collisions with obstacles could help reduce health costs and increase the quality of care and independence of thousands of people. This study evaluated the safety and performance of the Veterans Affairs Personal Adaptive Mobility Aid (VA-PAMAID). We performed engineering tests on the VA-PAMAID to determine safety factors, including stability, energy consumption, fatigue life, and sensor and control malfunctions. The VA-PAMAID traveled 10.9 km on a full charge and avoided obstacles while traveling at a speed of up to 1.2 m/s. No failures occurred during static stability, climatic, or fatigue testing. Some problems were encountered during obstacle climbing and sensor and control testing. The VA-PAMAID has good range, has adequate reaction time, and is structurally sound. Clinical trials are planned to compare the device to other low-technical adaptive mobility devices.
Equipment Design↗
Pushrim biomechanics and injury prevention in spinal cord injury: recommendations based on CULP-SCI investigations.
Over 50 percent of manual wheelchair users with spinal cord injury (SCI) are likely to develop upper-limb pain and injury. The majority of studies related to pain have implicated wheelchair propulsion as a cause. This paper draws from a large multisite trial and a long-standing research program to make specific recommendations related to wheelchair propulsion that may decrease the risk of upper-limb injury. The studies include over 60 subjects over 1 yr after a traumatic SCI below the second thoracic level. Specific aspects of the propulsive stroke that may relate to injury include cadence, magnitude of force, and the pattern of the hand during the nonpropulsive part of the stroke. Lower peak forces, slower cadence, and a circular propulsive stroke in which the hand falls below the pushrim during recovery may help prevent injury. In addition, wheelchair users should use the lightest weight adjustable wheelchair possible. Future work should include interventional trials and larger studies that allow for more complex statistical models that can further detail the relationship between wheelchair propulsion, user characteristics, and upper-limb injuries.
Adult↗