Pushrim-activated Power-assisted Wheelchair Research Articles

Calibration to Differentiate Power Output by the Manual Wheelchair User from the Pushrim-Activated Power-Assisted Wheel on a Force-Instrumented Computer-Controlled Wheelchair Ergometer

To examine the biomechanical demands of manual wheelchair propulsion, it is crucial to determine the wheelchair user’s (WCU) force for propulsion technique parameter calculation. When using a pushrim-activated power-assisted wheelchair (PAPAW) on a wheelchair ergometer, a combined propulsion force from the WCU and PAPAW is exerted. To understand PAPAW’s assistance and distinguish the WCU’s force application from the force exerted by the PAPAW, both propulsion components must be assessed separately. In this study, a calibration of the PAPAW on an ergometer was developed to achieve this separation. The calibration consists of five steps: (I) Collecting data on force and velocity measured from the ergometer, along with electrical current and velocity from the PAPAW. (II) Synchronizing the velocity signals of the wheelchair ergometer and PAPAW using cross-correlation. (III) Calibrating the PAPAW’s electromotors to convert electrical current (mA) to force (N). A product-specific motor constant of 0.30, provided an average ICC of 0.563, indicating a moderate agreement between the raw ergometer data (N) and the motor constant-converted drive-rim (PAPAW) data (from mA to N). (IV) Subtracting the PAPAW’s force signal from the ergometer’s measured force to isolate forces generated by the WCU. (V) Using markerless motion capture to determine and validate the phase of hand contact with the handrim. This technical note provides an example of PAPAW calibration for researchers and clinicians. It emphasizes the importance of integrating this calibration into the development of PAPAW devices to reveal the complex interaction between PAPAW and WCU during wheelchair propulsion.

Calibration to Differentiate Power Output by the Manual Wheelchair User from the Pushrim-Activated Power-Assisted Wheel on a Force-Instrumented Computer-Controlled Wheelchair Ergometer

To examine the biomechanical demands of manual wheelchair propulsion, it is crucial to determine the wheelchair user’s (WCU) force for propulsion technique parameter calculation. When using a pushrim-activated power-assisted wheelchair (PAPAW) on a wheelchair ergometer, a combined propulsion force from the WCU and PAPAW is exerted. To understand PAPAW’s assistance and distinguish the WCU’s force application from the force exerted by the PAPAW, both propulsion components must be assessed separately. In this study, a calibration of the PAPAW on an ergometer was developed to achieve this separation. The calibration consists of five steps: (I) Collecting data on force and velocity measured from the ergometer, along with electrical current and velocity from the PAPAW. (II) Synchronizing the velocity signals of the wheelchair ergometer and PAPAW using cross-correlation. (III) Calibrating the PAPAW’s electromotors to convert electrical current (mA) to force (N). A product-specific motor constant of 0.30, provided an average ICC of 0.563, indicating a moderate agreement between the raw ergometer data (N) and the motor constant-converted drive-rim (PAPAW) data (from mA to N). (IV) Subtracting the PAPAW’s force signal from the ergometer’s measured force to isolate forces generated by the WCU. (V) Using markerless motion capture to determine and validate the phase of hand contact with the handrim. This technical note provides an example of PAPAW calibration for researchers and clinicians. It emphasizes the importance of integrating this calibration into the development of PAPAW devices to reveal the complex interaction between PAPAW and WCU during wheelchair propulsion.

Comparison of Manual Wheelchair and Pushrim-Activated Power-Assisted Wheelchair Propulsion Characteristics during Common Over-Ground Maneuvers.

Pushrim-activated power-assisted wheels (PAPAWs) are assistive technologies that use force sensor data to provide on-demand propulsion assistance to manual wheelchair users. However, available data about kinetic and kinematic of PAPAW use are mainly limited to experiments performed on a treadmill or using a dynamometer. In this work, we performed experiments to gather kinetics of wheelchair propulsion and kinematics of wheelchair motion for a variety of over-ground wheelchair maneuvers with a manual wheelchair with and without PAPAWs. Our findings revealed that using PAPAWs can significantly reduce the propulsion effort and push frequency. Both linear and angular velocities of the wheelchair were significantly increased when using PAPAWs. Less force and push frequency could potentially reduce risk of chronic upper limb injury. Higher linear velocity could be desirable for various daily life activities; however; the increase in the angular velocity could lead to unintended deviations from a desired path. Future research could investigate PAPAW controllers that amplify the desired intentions of users while mitigating any unwanted behaviours.

Practice-based skill acquisition of pushrim-activated power-assisted wheelchair propulsion versus regular handrim propulsion in novices

BackgroundRegular handrim wheelchair (RHW) propulsion is straining for the upper extremities and wheelchair users often experience overuse problems. A recent advancement in wheelchair technology that could assist users is the pushrim-activated power-assisted wheelchair (PAPAW). PAPAWs are challenging to control, yet it is unclear how people learn to use a PAPAW. The purpose of this study is to examine early skill acquisition through practice in PAPAWs and compare it with RHWs.MethodsTwenty-four able-bodied novices were randomly allocated to either the RHW group or the PAPAW group. The experiment consisted of five sessions with three blocks of 4 min steady-state practice at 1.11 m/s and 0.21 W/kg. Finally, a transfer to the other mode was made. Data were collected with a drag-test, breath-by-breath spirometry, and a motion capture system. The last minute of each four-minute block was used for analysis. A mixed analysis of variance (ANOVA) was used to test for group, time, and interaction effects.ResultsBoth groups improved their (assisted) mechanical efficiency, reduced their stroke rate, right-left and forward-backward deviation on the treadmill, and had a lower rate of perceived exertion (RPE) over time. (Assisted) mechanical efficiency was higher for the PAPAW group than for the RHW group and RPE was lower. However, left-right and forward-backward deviation was also found to be higher in the PAPAW group.ConclusionsAt the group level the energetic cost of RHW and PAPAW propulsion can be lowered through low-intensity practice in novice users. The PAPAW is more ‘efficient’ than the RHW given the reduced energy requirement of the user from the motor assist, but more difficult to control. Future studies on PAPAWs should focus on the control needs of the user and their interaction with the power-assist technology.

Effect of shoulder's centralized exercise and pushrim activated power assisted wheelchair on shoulder pain and function veterans affected by paraplegic spinal cord injury

Effect of shoulder's centralized exercise and pushrim activated power assisted wheelchair on shoulder pain and function veterans affected by paraplegic spinal cord injury

A systematic review on the pros and cons of using a pushrim-activated power-assisted wheelchair

Objective: To determine the (dis)advantages of transition to a power-assisted wheelchair, and derive the clinical implications for its use or prescription. Data sources: Relevant articles published prior to May 2012 were identified using PubMed, Cochrane Library, REHABDATA, CIRRIE and CINAHL databases. Review methods: Clinical or (randomized) controlled trials, published in a peer-reviewed journal, comparing power-assisted wheelchair use and hand-rim or powered wheelchair use were eligible. Data quality and validity were assessed by two reviewers independently using the Checklist for Measuring Quality developed by Downs and Black. Results: A systematic search yielded 15 cross-over trails with repeated measurement design and one qualitative interview. Methodological quality scored between 9 and 15 points out of the maximum score of 32. Ten studies measuring body function and structure reported reduced strain on the arm and cardiovascular system during power-assisted propulsion compared to hand-rim propulsion. Twelve studies measuring activities and social participation reported precision tasks easier to perform with a hand-rim wheelchair and tasks which require more torque were easier with a power-assisted wheelchair. Social participation was not altered significantly by the use of a hand-rim, powered or power-assisted wheelchair. Conclusion: Power-assisted propulsion might be beneficial for subjects in whom independent hand-rim wheelchair propulsion is endangered by arm injury, insufficient arm strength or low cardiopulmonary reserves. Also, subjects who have difficulty propelling a wheelchair in a challenging environment can benefit from power-assisted wheelchair use. Caution is warranted for the additional width and weight in relation to the usual mode of transportation and access to the home environment.

Experiences with Using a Pushrim-Activated Power-Assisted Wheelchair for Community-Based Occupations: A Qualitative Exploration

Occupational therapists strive to engage individuals in occupation and enhance community access through wheelchair prescription. Previous research with pushrim-activated, power-assisted wheelchairs identifies a reduction in the physical demands of manual wheelchair propulsion but limited evidence exists regarding user evaluation in context. This study explored the experience of using a power-assisted wheelchair in the community. Eight individuals who used both a power and manual device participated in focus groups after trialing a power-assist wheelchair for three weeks. Data were analyzed using a qualitative description approach. Three themes emerged from our analysis: relative advantages and disadvantages; environmental factors that affect accessibility; and evaluation of mobility device. Participants perceived the power-assist as improving performance and accessibility compared with the manual wheelchair, increasing the potential scope of occupations and environments, but not replacing their power mobility device. Sufficient time for adjustment of both user and device was important.

Relationship between wheelchair durability and wheelchair type and years of test

Objective. To investigate the relationship between the durability of wheelchairs according to American National Standard for Wheechairs/Rehabilitation Engineering and Assistive Technology Society of North America (ANSI/RESNA) Wheelchair Standards and wheelchair type as well as year of test.Design. A retrospective study design with a sample of 246 wheelchairs that were tested in accordance with the ANSI/RESNA standards from 1992 to 2008 including four types of wheelchairs: manual wheelchair (MWC), electrical powered wheelchair (EPW), scooters and pushrim-activated power-assisted wheelchair (PAPAW). Unconditional binary logic regression analysis was chosen to evaluate the relationship between test results and test year as well as wheelchair type.Setting. Rehabilitation Engineering Research Center.Main Outcome Measures: Wheelchair durability test result (fatigue test: pass or fail)Results. There was no significant correlation between the year when tested and equivalent cycles. A significant relation was found between test results and wheelchair type (Wald score = 10.845, degree of freedom = 3, p = 0.013) with scooters having a significantly higher pass ratio than MWC (OR = 15.629, 95% CI = 2.026–120.579). EPW also had significantly higher pass ratio than MWC (OR = 1.953, 95% CI = 1.049–3.636). No significant difference on pass ratio was found between PAPAW and MWC.Conclusions. No significant improvements in wheelchair test results during the time frame from 1992 to 2008 were discovered. Wheelchair standard tests should be conducted to assure minimum quality of the wheelchairs and for improving the design of wheelchairs. Although the ANSI/RESNA wheelchair durability test procedures have remained consistent, it does not appear that the introduction of new materials, designs and the availability of test data have improved wheelchair fatigue life.

Comparison of Shoulder Muscle Electromyographic Activity During Standard Manual Wheelchair and Push-Rim Activated Power Assisted Wheelchair Propulsion in Persons With Complete Tetraplegia

Lighthall-Haubert L, Requejo PS, Mulroy SJ, Newsam CJ, Bontrager E, Gronley JK, Perry J. Comparison of shoulder muscle electromyographic activity during standard manual wheelchair and push-rim activated power assisted wheelchair propulsion in persons with complete tetraplegia. Objectives To compare spatio-temporal propulsion characteristics and shoulder muscle electromyographic activity in persons with cervical spinal cord injury propelling a standard pushrim wheelchair (WC) and a commercially available pushrim-activated power assisted wheelchair (PAPAW) design on a stationary ergometer. Design Repeated measures. Setting Motion analysis laboratory within a rehabilitation hospital. Participants Men (N=14) with complete (American Spinal Injury Association grade A or B) tetraplegia (C6=5; C7=9). Intervention Participants propelled a standard pushrim WC and PAPAW during 3 propulsion conditions: self-selected free and fast and simulated 4% or 8% graded resistance propulsion. Main Outcome Measures Median speed, cycle length, cadence, median and peak electromyographic activity intensity, and duration of electromyographic activity in pectoralis major, anterior deltoid, supraspinatus, and infraspinatus muscles were compared between standard pushrim WC and PAPAW propulsion. Results A significant ( P<.05) decrease in electromyographic activity intensity and duration of pectoralis major, anterior deltoid, and infraspinatus muscles and significantly reduced intensity and push phase duration of supraspinatus electromyographic activity at faster speeds and with increased resistance were seen during PAPAW propulsion. Conclusions For participants with complete tetraplegia, push phase shoulder muscle activity was decreased in the PAPAW compared with standard pushrim WC, indicating a reduction in demands when propelling a PAPAW.

Participation in community-based activities of daily living: Comparison of a pushrim-activated, power-assisted wheelchair and a power wheelchair

Purpose. The purpose of this study was to evaluate pushrim-activated, power-assisted wheelchair (PPW) performance among dual-users in their natural environment to determine whether the PPW would serve as a satisfactory alternative to a power wheelchair for community-based activities.Methods. A concurrent mixed methods research design using a cross-over trial was used. The outcome measures used were number of hours reported using the different wheelchairs, Quebec User Evaluation of Satisfaction with assistive Technology (QUEST), Functioning Everyday with a Wheelchair (FEW), Psychosocial Impact of Assistive Devices Scale (PIADS) and Canadian Occupational Performance Measure (COPM).Results. The number of hours spent participating in self-identified activities was not significantly different. Only the Self-Esteem subscale of the PIADS identified a statistically significant difference between the PPW and power wheelchair conditions (p = 0.016). A clinically important difference for Performance and Satisfaction was suggested by the COPM, in favour of the power wheelchair.Conclusions. Additional knowledge was gained about the benefits of PPW technology. Participants were able to continue participating independently in their self-identified community activities using the PPW, and identified comparable ratings of satisfaction and performance with the PPW and the power wheelchair. For some individuals requiring power mobility, the PPW may provide an alternative to the power wheelchair.

Poster 27: Characterizing Successful Pushrim-Activated Power-Assist Wheelchair Users

Poster 27: Characterizing Successful Pushrim-Activated Power-Assist Wheelchair Users

Enquête de satisfaction sur l'équipement technologique des personnes tétraplégiques par blessure medullaire

Objective To measure the acquisition, use and satisfaction with high technology equipment by spinal cord injured tetraplegic subjects. Design and setting A questionnaire was mailed to 102 tetraplegic subjects who were hospitalised in the rehabilitation center ofKerpape (Ploemeur, France) between 1998 and 2004, and 59 subjects responded. The questionnaire asked about the use of telephones, computers, wheelchairs and environmental controls at home. Results When a piece of equipment was acquired, it was very often used. Patient satisfaction with equipment was 79.3%. Home phones and mobile phones were often used with options such as hands-free devices (78 and 59% respectively). A total of 64.4% of subjects acquired a manual wheelchair and 61% a power wheelchair. The most commonly acquired options on the power wheelchairs were the powered recline (73,7%) and tilt (71,1%) systems. All options were used but all were more desired than acquired. A total of 27.1% of subjects desired a pushrim-activated power-assist wheelchair, but only 15.3% had acquired one; 695% of subjects had a computer. Communication was the first use for the computer (82.5%); 49.2% of subjects had acquired an environmental control system, but 20% desired one. The first reason for lack of acquisition was financial difficulties but also accessibility and information problems. The factor that influenced the acquisition and need for equipment was the degree of spinal cord injury. No other factor reduced patient satisfaction with equipment. Conclusion Patients were satisfied with the equipment they acquired. But their needs, especially wheelchair options and environmental control systems, were not satisfied.

Comparison between performance with a pushrim-activated power-assisted wheelchair and a manual wheelchair on the Wheelchair Skills Test

Purpose. To test the hypothesis that people using a pushrim-activated power-assisted wheelchair (PAPAW) can accomplish a wider range of wheelchair skills than when using a manual wheelchair (MWC).Methods. We studied 30 able-bodied participants, using within-participant comparisons. Participants used a manual wheelchair equipped with both PAPAW and regular MWC rear wheels, and rear anti-tip devices (Arc-RADs) that permitted wheelie-like function. We trained participants to perform the wheelchair skills of the Wheelchair Skills Training Program (WSTP, Version 2.4). From the Wheelchair Skills Test (WST, Version 2.4), we calculated pass-fail success rates for the 50 individual skills and a total percentage WST score.Results. The mean (±SD) total WST scores were 89.3 (±7.0)% for the PAPAW and 88.8 (±8.4)% for the MWC, with a mean difference of 0.6 (±5.6)% (p = 0.59). Qualitative observations suggested that skills requiring a higher force on the pushrim (e.g., incline ascent) were performed more easily with the PAPAW, whereas skills requiring greater control of the wheelchair (e.g., wheelie-dependent skills) were performed more easily with the MWC.Conclusion. Overall wheelchair skill performance with the PAPAW is not superior to that when using the MWC. The PAPAW may be helpful for specific skills that require more wheel torque, but the additional torque appears to be disadvantageous when performing skills that require greater control.

Effect of a pushrim-activated power-assist wheelchair on the functional capabilities of persons with tetraplegia

Algood SD, Cooper RA, Fitzgerald SG, Cooper R, Boninger ML. Effect of a pushrim-activated power-assist wheelchair on the functional capabilities of persons with tetraplegia. ObjectivesTo test the differences between a pushrim-activated power-assisted wheelchair (PAPAW) and a traditional manual wheelchair while performing common driving activities and to assess their relative merits for people with tetraplegia. DesignRepeated measures. SettingAn activities of daily living (ADL) laboratory within a rehabilitation research center. ParticipantsFifteen full-time manual wheelchair users with tetraplegia due to a spinal cord injury. InterventionsParticipants propelled both their own manual wheelchairs and a PAPAW 3 times over an ADL course. The order in which the 2 different wheelchairs were presented to the participants was randomized. Main outcome measuresEach participant’s heart rate was monitored throughout testing by a digital, wireless heart-rate monitor. Time to complete the course was recorded, and participants were surveyed with a visual analog scale after the first, third, fourth, and sixth trials to determine the ease of completing each obstacle and their ergonomic preferences between the 2 wheelchairs. Participants also were observed throughout the trials to determine how much assistance they needed to complete each obstacle course. ResultsAfter using a Bonferroni adjustment, 4 obstacles (carpet, dimple strips, up a ramp, up a curb cut) were rated as being significantly easier (P<.001) to complete when using the PAPAW. Participants also showed a significant decrease in mean heart rate throughout all 3 trials (P=.015, P=.001, P=.003, respectively) when using a PAPAW. The amount of assistance needed by participants, the responses to ergonomic questions, and the overall time to complete the ADL course did not differ significantly between the 2 wheelchairs. ConclusionsFor subjects with tetraplegia, PAPAWs have the potential to improve functional capabilities during certain ADLs, especially when propelling up ramps, over uneven surfaces, and over thick carpet.

Impact of a pushrim-activated power-assisted wheelchair on the metabolic demands, stroke frequency, and range of motion among subjects with tetraplegia

Algood SD, Cooper RA, Fitzgerald SG, Cooper R, Boninger ML. Impact of a pushrim-activated power-assisted wheelchair on the metabolic demands, stroke frequency, and range of motion among subjects with tetraplegia. Arch Phys Med Rehabil 2004;85:1865–71. Objectives To determine differences in metabolic demands, stroke frequency, and upper-extremity joint range of motion (ROM) during pushrim-activated power-assisted wheelchair (PAPAW) propulsion and traditional manual wheelchair propulsion among subjects with tetraplegia. Design Repeated measures. Setting A biomechanics laboratory within a Veterans Affairs medical center. Participants Fifteen full-time manual wheelchair users who had sustained cervical-level spinal cord injuries. Interventions Participants propelled both their own manual wheelchairs and a PAPAW through 3 different resistances (slight, 10W; moderate, 12W; high, 14W) on a wheelchair dynamometer. Each propulsion trial was 3 minutes long. Main outcome measures Primary variables that were compared between the 2 wheelchairs were participants’ mean steady-state oxygen consumption, ventilation, heart rate, mean stroke frequency, and maximum upper-extremity joint ROM. Results When using the PAPAW, participants showed a significant ( P<.05) decrease in mean oxygen consumption and ventilation throughout all trials. Mean heart rate was significantly lower when using the PAPAW for the high resistance trial. Stroke frequency was significantly lower when using the PAPAW for the slight and moderate resistances. Overall joint ROM was significantly lower when using the PAPAW. Conclusions For subjects with tetraplegia, PAPAWs reduce the energy demands, stroke frequency, and overall joint ROM when compared with traditional manual wheelchair propulsion.

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.

Variable-ratio pushrim-activated power-assist wheelchair eases wheeling over a variety of terrains for elders

Levy CE, Chow JW, Tillman MD, Hanson C, Donohue T, Mann WC. Variable-ratio pushrim-activated power-assist wheelchair eases wheeling over a variety of terrains for elders. Arch Phys Med Rehabil 2004;85:104-12. Objectives To test (1) whether a prototype variable-ratio pushrim-activated power-assist wheelchair would decrease effort and perceived exertion associated with wheeling and (2) whether the prototype would be acceptable to elders. Design Repeated-measures design. Setting Biomechanics laboratory. Participants Eleven elderly wheelers (mean age ± standard deviation, 70.7±7.8y). Interventions Wheelers propelled their own wheelchairs and the prototype on a level surface, a carpet, and an incline. Main outcome measures Surface electromyographic activity from upper limb and torso, heart rate, number of pushes, category-ratio scale of perceived exertion, and Consumer Assessment of Power Assist Wheelchairs. Results Compared with subjects’ own manual wheelchairs, the prototype was associated with lower heart rate elevation ( P<.0125), lower perceived exertion ( P<.0125), and reduced electromyographic activity in 5 of 8 muscles. Of the 11 participants, 10 found the prototype to be “very easy” or “easy” to push on level and inclined surfaces; 9 gave that assessment on carpeted and inclined surfaces. Seven would “definitely” or “probably” trade their manual chairs for the power-assist chair if given the opportunity. Nine thought they would venture to new and different places in a power-assist wheelchair. Time and number of pushes to complete tasks did not differ significantly between chairs. Conclusions The prototype reduced the effort associated with wheeling and was an acceptable alternative to manual wheelchairs. Further testing outside the laboratory is warranted.

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 fle xion/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.

Performance assessment of a pushrim-activated power-assisted wheelchair control system

Wheelchairs are an important form of mobility for people with disabilities. For many years, there have only been three wheelchair varieties: electric-powered wheelchairs, scooters and manual wheelchairs. Recently, wheelchairs have been developed that use a combination of human power and electric power. The human power is delivered by the arms through the pushrims while the electric power is delivered by a battery through two electric motors. The shared control system for a pushrim-activated power-assisted wheelchair (PAPAW) must account for the human behavior and the interaction with the device. The PAPAW uses a form of gain scheduling based upon events recorded from the pushrim torque. The control system significantly altered (p<0.05) selected variables from pushrim torque curves for manual wheelchair propulsion and PAPAW operation as desired. The peak torque was reduced by over 50%, and the time on the rim was nearly doubled with the PAPAW. The PAPAW provided intuitive control and was capable of significantly reducing the strain on the upper extremities commonly associated with secondary disabling conditions among manual wheelchair users.

Mechanical efficiency and user power requirement with a pushrim activated power assisted wheelchair

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<0.05), and mechanical efficiency significantly higher with the PAPAW than with subjects' own chairs. Subjects needed to generate on average 3.65 times more power when propelling their own wheelchairs as compared to PAPAW. Mean mechanical efficiency over all trials was 80.33% higher with the power assisted hubs. PAPAW provides on average 73% of the total power when subjects propel with power assistance. Significantly increased efficiency and reduced requirement of user power is achieved using the PAPAW. With use, the PAPAW may contribute to delaying secondary injuries of manual wheelchair users. In addition, it may be suitable for people who have (or at risk for) upper extremity joint degeneration, reduced exercise capacity, low strength or endurance who currently use electric powered wheelchairs.