Alicia Koontz - Profile on Academia.edu (original) (raw)
articles by Alicia Koontz
Virtual reality and computer enhanced training applied to wheeled mobility: an overview of work in Pittsburgh
Papers by Alicia Koontz
BioMed research international, 2015
Identifying research needs for wheelchair transfers in the built environment
Disability and rehabilitation. Assistive technology, Jan 19, 2015
The purpose of this study is to describe the results of focus groups held during the Independent ... more The purpose of this study is to describe the results of focus groups held during the Independent Wheelchair Transfer (IWT) Workgroup. The aims were to facilitate exchange of ideas on (1) the impact of the built environment on the wheelchair transfer process within the community (i.e. moving from wheelchair to and from other surfaces (e.g. furniture, toilet seat, bath bench, car seat) to participate in daily activities), (2) wheelchair users' needs during transfers in the built environment, and (3) future research directions. Live web-based conferencing using Adobe Connect technology (Clarix Technologies, Inc., Pittsford, NY) was utilized to conduct three focus groups composed of experts in the field of assistive technology. Investigators independently reviewed focus group meeting transcripts and used qualitative methods to identify main themes. Thirty-one experts in assistive technology and related fields participated in focus groups. Nine main themes were found including the ef...
Biomechanics of Sitting Pivot Transfers Among Individuals with a Spinal Cord Injury: A Review of the Current Knowledge
Topics in Spinal Cord Injury Rehabilitation, 2009
... Biomechanics of Sitting Pivot Transfers Among Individuals with a Spinal Cord Injury: A Review... more ... Biomechanics of Sitting Pivot Transfers Among Individuals with a Spinal Cord Injury: A Review of the Current Knowledge Dany Gagnon, Alicia M. Koontz, Sara J. Mulroy, Debbie A. Nawoczenski, Emelie Butler-Forslund, Anna Granstrom, Sylvie Nadeau, and Michael L. Boninger ...
BioMed research international, 2014
This study investigated (1) the effect of repetitive weight-relief raises (WR) and shoulder exter... more This study investigated (1) the effect of repetitive weight-relief raises (WR) and shoulder external rotation (ER) on the acromiohumeral distance (AHD) among manual wheelchair users (MWUs) and (2) the relationship between shoulder pain, subject characteristics, and AHD changes. Twenty-three MWUs underwent ultrasound imaging of the nondominant shoulder in an unloaded baseline position and while holding a WR position before and after the WR/ER tasks. Paired t-tests and Spearman correlational analysis were used to assess differences in the AHD before and after each task and the relationships between pain, subject characteristics, and the AHD measures. A significant reduction in the subacromial space (P<0.01) occurred when subjects performed a WR position compared to baseline. Individuals with increased years of disability had greater AHD percentage narrowing after WR (P=0.008). Increased shoulder pain was associated with AHD percentage narrowing after ER (P≤0.007). The results suppo...
BioMed research international, 2014
Transfers are one of the most physically demanding wheelchair activities. The purpose of this stu... more Transfers are one of the most physically demanding wheelchair activities. The purpose of this study was to determine if using proper transfer skills as measured by the Transfer Assessment Instrument (TAI) is associated with reduced loading on the upper extremities. Twenty-three wheelchair users performed transfers to a level-height bench while a series of forces plates, load cells, and a motion capture system recorded the biomechanics of their natural transferring techniques. Their transfer skills were simultaneously evaluated by two study clinicians using the TAI. Logistic regression and multiple linear regression models were used to determine the relationships between TAI scores and the kinetic variables on both arms across all joints. The results showed that the TAI measured transfer skills were closely associated with the magnitude and timing of joint moments (P < .02, model R(2) values ranged from 0.27 to 0.79). Proper completion of the skills which targeted the trailing arm...
Comparison between overground and dynamometer manual wheelchair propulsion
Journal of applied biomechanics, 2012
Laboratory-based simulators afford many advantages for studying physiology and biomechanics; howe... more Laboratory-based simulators afford many advantages for studying physiology and biomechanics; however, they may not perfectly mimic wheelchair propulsion over natural surfaces. The goal of this study was to compare kinetic and temporal parameters between propulsion overground on a tile surface and on a dynamometer. Twenty-four experienced manual wheelchair users propelled at a self-selected speed on smooth, level tile and a dynamometer while kinetic data were collected using an instrumented wheel. A Pearson correlation test was used to examine the relationship between propulsion variables obtained on the dynamometer and the overground condition. Ensemble resultant force and moment curves were compared using cross-correlation and qualitative analysis of curve shape. User biomechanics were correlated (R ranging from 0.41 to 0.83) between surfaces. Overall, findings suggest that although the dynamometer does not perfectly emulate overground propulsion, wheelchair users were consistent w...
Proper propulsion
Rehab management, 2003
Boninger ML, Cooper RA, Baldwin MA, Shimada SD, Koontz A. Wheelchair pushrim kinetics: body weigh... more Boninger ML, Cooper RA, Baldwin MA, Shimada SD, Koontz A. Wheelchair pushrim kinetics: body weight and median nerve function. Arch Phys Med Rehabil 1999;80:910-5.
Descriptions of shoulder kinematics during wheelchair propulsion are limited to motions of the up... more Descriptions of shoulder kinematics during wheelchair propulsion are limited to motions of the upper arm due to the difficulty of measuring scapular movement in vivo. Using a digitizing stylus, the three-dimensional positions of three anatomical landmarks on the scapula were recorded for 10 manual wheelchair users in six different statically held hand positions (À30 , À15 , 0 , 15 , 30 , 60 ) on the pushrim. In each hand position, a motion analysis system recorded the coordinates of infrared markers on the arm and torso. Scapular, humeral, and torso angles were computed using an Euler angle decomposition method for each position relative to the torso. At the beginning of the push, the scapula was rotated slightly upward (1.5 ), minimally protracted (15 ), and maximally tipped forward (22 ). In addition, the humerus was maximally extended, abducted and internally rotated. As subjects moved forward along the pushrim, the protraction angle increased while the forward tipping angle decreased. The humerus became increasingly more flexed as the push progressed with small changes observed in humeral abduction and internal rotation. A stepwise multiple regression analysis procedure (po0:01) revealed that the torso, humeral flexion/extension and abduction angles are good predictors for estimating forward tipping and upward/downward rotation of the scapula. The regression equations enable researchers to estimate scapular orientation during propulsion which could provide further insight into specific biomechanical factors that lead to shoulder pathology.
An expert review of the scientific literature on independent wheelchair transfers
Disability and rehabilitation. Assistive technology, 2012
The purpose of this study was to perform a literature review and seek expert opinion on the relev... more The purpose of this study was to perform a literature review and seek expert opinion on the relevance and strength of the evidence concerning setup and transfer performance. Scientific literature databases were searched until June 2009 using 43 keywords resulting in 339 articles. These were internally reviewed and narrowed to 41 articles which were formally assessed by 13 external experts. Articles that 80% or more of the reviewers scored as moderately or highly relevant were included in the final results. Nineteen articles met the relevancy criteria. The aspects of setup that experts felt were addressed to some degree included vertical transfer distance, transferring across a gap and position of the mobility device relative to target destination. None of the 19 articles were scored as having strong to very strong resulting evidence. There is a consensus among studies that transferring to a higher surface implies greater exertion of the upper limb. However, there is no evidence conc...
An autoregressive modeling approach to analyzing wheelchair propulsion forces
Medical Engineering & Physics, 2001
Biomechanical signals collected during wheelchair propulsion are often analyzed by computing aver... more Biomechanical signals collected during wheelchair propulsion are often analyzed by computing averages and/or peak values over several strokes. Due to the complex nature of the signals, this type of analysis may not be specific to identifying factors that may predispose a wheelchair user to joint pain/injury. Hence, a new technique is introduced that uses a system identification approach, autoregressive (AR) modeling, to analyze wheelchair propulsion force waveforms. In this application an AR method was used to create a model force waveform based on current and past values of digital pushrim force data. The feasibility of the AR modeling method over point-wise methods to detect asymmetry among force waveforms was tested with a group of 20 wheelchair users. Subjects propelled at a constant 0.9 m/s on a roller system during which 20 s of force data were collected from the SMART(Wheel)s, force and torque sensing pushrims. Both methods showed that the wheelchair users as a group propelled evenly, however, individual analysis using the AR model error estimates indicated that twenty-five percent demonstrated significant asymmetry in their force waveforms. If only point-wise means and variances of the applied bilateral forces were considered, most subjects would have appeared symmetrical. Thus, the AR modeling approach is more sensitive to detecting anomalies in propulsion technique.
The Journal of Rehabilitation Research and Development, 2009
This study's main objective was to determine if upper-limb (UL) muscular demand was reduced when ... more 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.
The Journal of Rehabilitation Research and Development, 2005
The objective of this study was to conduct a kinetic analysis of manual wheelchair propulsion dur... more The objective of this study was to conduct a kinetic analysis of manual wheelchair propulsion during start-up on select indoor and outdoor surfaces. Eleven manual wheelchairs were fitted with a SMART Wheel and their users were asked to push on a course consisting of high-and low-pile carpet, indoor tile, interlocking concrete pavers, smooth level concrete, grass, hardwood flooring, and a sidewalk with a 5-degree grade. Peak resultant force, wheel torque, mechanical effective force, and maximum resultant force rate of rise were analyzed during startup for each surface and normalized relative to their steady-state values on the smooth level concrete. Additional variables included peak velocity, distance traveled, and number of strokes in the first 5 s of the trial. We compared biomechanical data between surfaces using repeated-measures mixed models and paired comparisons with a Bonferroni adjustment. Applied resultant force (p = 0.0154), wheel torque (p < 0.0001), and mechanical effective force (p = 0.0047) were significantly different between surfaces. The kinetic values for grass, interlocking pavers, and ramp ascent were typically higher compared with tile, wood, smooth level concrete, and high-and low-pile carpet. Users were found to travel shorter distances up the ramp and across grass (p < 0.0025) and had a higher stroke count on the ramp (p = 0.0124). While peak velocity was not statistically different, average velocity was slower for the ramp and grass, which indicates greater wheelchair/user deceleration between strokes. The differences noted between surfaces highlight the importance of evaluating wheelchair propulsion ability over a range of surfaces.
The Journal of Rehabilitation Research and Development, 2007
A multisite collaborative study is being conducted on the association between propulsion biomecha... more A multisite collaborative study is being conducted on the association between propulsion biomechanics and upperlimb 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-brakecoastdown trial on a wheelchair dynamometer while propulsion forces and moment about the hub were measured with a Smart-Wheel. 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. Abbreviations: 3-D = three-dimensional, 3MP = third metacarpalphalangeal joint, ANCOVA = analysis of covariance, ANOVA = analysis of variance, HERL = Human Engineering Research Laboratories, KMRREC = Kessler Medical Rehabilitation Research and Education Corporation, NIDRR = National Institute on Disability and Rehabilitation Research, SCI = spinal cord injury, SD = standard deviation, T = thoracic, UW = University of Washington.
International Journal of Industrial Ergonomics, 2004
Descriptions of shoulder kinematics during wheelchair propulsion are limited to motions of the up... more Descriptions of shoulder kinematics during wheelchair propulsion are limited to motions of the upper arm due to the difficulty of measuring scapular movement in vivo. Using a digitizing stylus, the three-dimensional positions of three anatomical landmarks on the scapula were recorded for 10 manual wheelchair users in six different statically held hand positions (À30 , À15 , 0 , 15 , 30 , 60 ) on the pushrim. In each hand position, a motion analysis system recorded the coordinates of infrared markers on the arm and torso. Scapular, humeral, and torso angles were computed using an Euler angle decomposition method for each position relative to the torso. At the beginning of the push, the scapula was rotated slightly upward (1.5 ), minimally protracted (15 ), and maximally tipped forward (22 ). In addition, the humerus was maximally extended, abducted and internally rotated. As subjects moved forward along the pushrim, the protraction angle increased while the forward tipping angle decreased. The humerus became increasingly more flexed as the push progressed with small changes observed in humeral abduction and internal rotation. A stepwise multiple regression analysis procedure (po0:01) revealed that the torso, humeral flexion/extension and abduction angles are good predictors for estimating forward tipping and upward/downward rotation of the scapula. The regression equations enable researchers to estimate scapular orientation during propulsion which could provide further insight into specific biomechanical factors that lead to shoulder pathology.
Comparison of three different models to represent the wrist during wheelchair propulsion
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2001
Due to the high incidence of secondary wrist injury among manual wheelchair users, recent emphasi... more 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 degrees 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 degrees, 2.2 degrees, and 5.0 degrees for the midstyloid, de Leva, and floating joint center models, respectively. Extension angles were 22.3 degrees, 23.6 degrees, and 23.6 degrees, respectively. Mean maximum right radial deviation angles for the midstyloid, de Leva, and floating joint center models were 26.0 degrees, 26.9 degrees, and 45.1 degrees, respectively, and ulnar deviation angles were found to be 30.5 degrees, 38.8 degrees, and 10.2 degrees, respectively. This information is useful when comparing kinematic studies and further supports the need for consensual methodology.
Engineering Better Wheelchairs to Enhance Community Participation
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2000
With about 2.2 million Americans currently using wheeled mobility devices, wheelchairs are freque... more With about 2.2 million Americans currently using wheeled mobility devices, wheelchairs are frequently provided to people with impaired mobility to provide accessibility to the community. Individuals with spinal cord injuries, arthritis, balance disorders, and other conditions or diseases are typical users of wheelchairs. However, secondary injuries and wheelchair-related accidents are risks introduced by wheelchairs. Research is underway to advance wheelchair design to prevent or accommodate secondary injuries related to propulsion and transfer biomechanics, while improving safe, functional performance and accessibility to the community. This paper summarizes research and development underway aimed at enhancing safety and optimizing wheelchair design.
Clinical Biomechanics, 2006
Background. Trunk instability due to paralysis can have adverse effects on posture and function i... more Background. Trunk instability due to paralysis can have adverse effects on posture and function in a wheelchair. The purpose of this study was to record trunk muscle recruitment patterns using surface electromyography from unimpaired individuals during wheelchair propulsion under various propulsion speed conditions to be able to design trunk muscle stimulation patterns for actual wheelchair users with spinal cord injury.
Clinical Biomechanics, 2006
Background. Manual wheelchair users rely heavily on their upper limbs for independent mobility wh... more Background. Manual wheelchair users rely heavily on their upper limbs for independent mobility which likely leads to a high prevalence of shoulder pain and injury. The goal of this study was to examine the relationship between shoulder forces and moments experienced during wheelchair propulsion and shoulder pathology.
Virtual reality and computer enhanced training applied to wheeled mobility: an overview of work in Pittsburgh
BioMed research international, 2015
Identifying research needs for wheelchair transfers in the built environment
Disability and rehabilitation. Assistive technology, Jan 19, 2015
The purpose of this study is to describe the results of focus groups held during the Independent ... more The purpose of this study is to describe the results of focus groups held during the Independent Wheelchair Transfer (IWT) Workgroup. The aims were to facilitate exchange of ideas on (1) the impact of the built environment on the wheelchair transfer process within the community (i.e. moving from wheelchair to and from other surfaces (e.g. furniture, toilet seat, bath bench, car seat) to participate in daily activities), (2) wheelchair users' needs during transfers in the built environment, and (3) future research directions. Live web-based conferencing using Adobe Connect technology (Clarix Technologies, Inc., Pittsford, NY) was utilized to conduct three focus groups composed of experts in the field of assistive technology. Investigators independently reviewed focus group meeting transcripts and used qualitative methods to identify main themes. Thirty-one experts in assistive technology and related fields participated in focus groups. Nine main themes were found including the ef...
Biomechanics of Sitting Pivot Transfers Among Individuals with a Spinal Cord Injury: A Review of the Current Knowledge
Topics in Spinal Cord Injury Rehabilitation, 2009
... Biomechanics of Sitting Pivot Transfers Among Individuals with a Spinal Cord Injury: A Review... more ... Biomechanics of Sitting Pivot Transfers Among Individuals with a Spinal Cord Injury: A Review of the Current Knowledge Dany Gagnon, Alicia M. Koontz, Sara J. Mulroy, Debbie A. Nawoczenski, Emelie Butler-Forslund, Anna Granstrom, Sylvie Nadeau, and Michael L. Boninger ...
BioMed research international, 2014
This study investigated (1) the effect of repetitive weight-relief raises (WR) and shoulder exter... more This study investigated (1) the effect of repetitive weight-relief raises (WR) and shoulder external rotation (ER) on the acromiohumeral distance (AHD) among manual wheelchair users (MWUs) and (2) the relationship between shoulder pain, subject characteristics, and AHD changes. Twenty-three MWUs underwent ultrasound imaging of the nondominant shoulder in an unloaded baseline position and while holding a WR position before and after the WR/ER tasks. Paired t-tests and Spearman correlational analysis were used to assess differences in the AHD before and after each task and the relationships between pain, subject characteristics, and the AHD measures. A significant reduction in the subacromial space (P<0.01) occurred when subjects performed a WR position compared to baseline. Individuals with increased years of disability had greater AHD percentage narrowing after WR (P=0.008). Increased shoulder pain was associated with AHD percentage narrowing after ER (P≤0.007). The results suppo...
BioMed research international, 2014
Transfers are one of the most physically demanding wheelchair activities. The purpose of this stu... more Transfers are one of the most physically demanding wheelchair activities. The purpose of this study was to determine if using proper transfer skills as measured by the Transfer Assessment Instrument (TAI) is associated with reduced loading on the upper extremities. Twenty-three wheelchair users performed transfers to a level-height bench while a series of forces plates, load cells, and a motion capture system recorded the biomechanics of their natural transferring techniques. Their transfer skills were simultaneously evaluated by two study clinicians using the TAI. Logistic regression and multiple linear regression models were used to determine the relationships between TAI scores and the kinetic variables on both arms across all joints. The results showed that the TAI measured transfer skills were closely associated with the magnitude and timing of joint moments (P < .02, model R(2) values ranged from 0.27 to 0.79). Proper completion of the skills which targeted the trailing arm...
Comparison between overground and dynamometer manual wheelchair propulsion
Journal of applied biomechanics, 2012
Laboratory-based simulators afford many advantages for studying physiology and biomechanics; howe... more Laboratory-based simulators afford many advantages for studying physiology and biomechanics; however, they may not perfectly mimic wheelchair propulsion over natural surfaces. The goal of this study was to compare kinetic and temporal parameters between propulsion overground on a tile surface and on a dynamometer. Twenty-four experienced manual wheelchair users propelled at a self-selected speed on smooth, level tile and a dynamometer while kinetic data were collected using an instrumented wheel. A Pearson correlation test was used to examine the relationship between propulsion variables obtained on the dynamometer and the overground condition. Ensemble resultant force and moment curves were compared using cross-correlation and qualitative analysis of curve shape. User biomechanics were correlated (R ranging from 0.41 to 0.83) between surfaces. Overall, findings suggest that although the dynamometer does not perfectly emulate overground propulsion, wheelchair users were consistent w...
Proper propulsion
Rehab management, 2003
Boninger ML, Cooper RA, Baldwin MA, Shimada SD, Koontz A. Wheelchair pushrim kinetics: body weigh... more Boninger ML, Cooper RA, Baldwin MA, Shimada SD, Koontz A. Wheelchair pushrim kinetics: body weight and median nerve function. Arch Phys Med Rehabil 1999;80:910-5.
Descriptions of shoulder kinematics during wheelchair propulsion are limited to motions of the up... more Descriptions of shoulder kinematics during wheelchair propulsion are limited to motions of the upper arm due to the difficulty of measuring scapular movement in vivo. Using a digitizing stylus, the three-dimensional positions of three anatomical landmarks on the scapula were recorded for 10 manual wheelchair users in six different statically held hand positions (À30 , À15 , 0 , 15 , 30 , 60 ) on the pushrim. In each hand position, a motion analysis system recorded the coordinates of infrared markers on the arm and torso. Scapular, humeral, and torso angles were computed using an Euler angle decomposition method for each position relative to the torso. At the beginning of the push, the scapula was rotated slightly upward (1.5 ), minimally protracted (15 ), and maximally tipped forward (22 ). In addition, the humerus was maximally extended, abducted and internally rotated. As subjects moved forward along the pushrim, the protraction angle increased while the forward tipping angle decreased. The humerus became increasingly more flexed as the push progressed with small changes observed in humeral abduction and internal rotation. A stepwise multiple regression analysis procedure (po0:01) revealed that the torso, humeral flexion/extension and abduction angles are good predictors for estimating forward tipping and upward/downward rotation of the scapula. The regression equations enable researchers to estimate scapular orientation during propulsion which could provide further insight into specific biomechanical factors that lead to shoulder pathology.
An expert review of the scientific literature on independent wheelchair transfers
Disability and rehabilitation. Assistive technology, 2012
The purpose of this study was to perform a literature review and seek expert opinion on the relev... more The purpose of this study was to perform a literature review and seek expert opinion on the relevance and strength of the evidence concerning setup and transfer performance. Scientific literature databases were searched until June 2009 using 43 keywords resulting in 339 articles. These were internally reviewed and narrowed to 41 articles which were formally assessed by 13 external experts. Articles that 80% or more of the reviewers scored as moderately or highly relevant were included in the final results. Nineteen articles met the relevancy criteria. The aspects of setup that experts felt were addressed to some degree included vertical transfer distance, transferring across a gap and position of the mobility device relative to target destination. None of the 19 articles were scored as having strong to very strong resulting evidence. There is a consensus among studies that transferring to a higher surface implies greater exertion of the upper limb. However, there is no evidence conc...
An autoregressive modeling approach to analyzing wheelchair propulsion forces
Medical Engineering & Physics, 2001
Biomechanical signals collected during wheelchair propulsion are often analyzed by computing aver... more Biomechanical signals collected during wheelchair propulsion are often analyzed by computing averages and/or peak values over several strokes. Due to the complex nature of the signals, this type of analysis may not be specific to identifying factors that may predispose a wheelchair user to joint pain/injury. Hence, a new technique is introduced that uses a system identification approach, autoregressive (AR) modeling, to analyze wheelchair propulsion force waveforms. In this application an AR method was used to create a model force waveform based on current and past values of digital pushrim force data. The feasibility of the AR modeling method over point-wise methods to detect asymmetry among force waveforms was tested with a group of 20 wheelchair users. Subjects propelled at a constant 0.9 m/s on a roller system during which 20 s of force data were collected from the SMART(Wheel)s, force and torque sensing pushrims. Both methods showed that the wheelchair users as a group propelled evenly, however, individual analysis using the AR model error estimates indicated that twenty-five percent demonstrated significant asymmetry in their force waveforms. If only point-wise means and variances of the applied bilateral forces were considered, most subjects would have appeared symmetrical. Thus, the AR modeling approach is more sensitive to detecting anomalies in propulsion technique.
The Journal of Rehabilitation Research and Development, 2009
This study's main objective was to determine if upper-limb (UL) muscular demand was reduced when ... more 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.
The Journal of Rehabilitation Research and Development, 2005
The objective of this study was to conduct a kinetic analysis of manual wheelchair propulsion dur... more The objective of this study was to conduct a kinetic analysis of manual wheelchair propulsion during start-up on select indoor and outdoor surfaces. Eleven manual wheelchairs were fitted with a SMART Wheel and their users were asked to push on a course consisting of high-and low-pile carpet, indoor tile, interlocking concrete pavers, smooth level concrete, grass, hardwood flooring, and a sidewalk with a 5-degree grade. Peak resultant force, wheel torque, mechanical effective force, and maximum resultant force rate of rise were analyzed during startup for each surface and normalized relative to their steady-state values on the smooth level concrete. Additional variables included peak velocity, distance traveled, and number of strokes in the first 5 s of the trial. We compared biomechanical data between surfaces using repeated-measures mixed models and paired comparisons with a Bonferroni adjustment. Applied resultant force (p = 0.0154), wheel torque (p < 0.0001), and mechanical effective force (p = 0.0047) were significantly different between surfaces. The kinetic values for grass, interlocking pavers, and ramp ascent were typically higher compared with tile, wood, smooth level concrete, and high-and low-pile carpet. Users were found to travel shorter distances up the ramp and across grass (p < 0.0025) and had a higher stroke count on the ramp (p = 0.0124). While peak velocity was not statistically different, average velocity was slower for the ramp and grass, which indicates greater wheelchair/user deceleration between strokes. The differences noted between surfaces highlight the importance of evaluating wheelchair propulsion ability over a range of surfaces.
The Journal of Rehabilitation Research and Development, 2007
A multisite collaborative study is being conducted on the association between propulsion biomecha... more A multisite collaborative study is being conducted on the association between propulsion biomechanics and upperlimb 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-brakecoastdown trial on a wheelchair dynamometer while propulsion forces and moment about the hub were measured with a Smart-Wheel. 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. Abbreviations: 3-D = three-dimensional, 3MP = third metacarpalphalangeal joint, ANCOVA = analysis of covariance, ANOVA = analysis of variance, HERL = Human Engineering Research Laboratories, KMRREC = Kessler Medical Rehabilitation Research and Education Corporation, NIDRR = National Institute on Disability and Rehabilitation Research, SCI = spinal cord injury, SD = standard deviation, T = thoracic, UW = University of Washington.
International Journal of Industrial Ergonomics, 2004
Descriptions of shoulder kinematics during wheelchair propulsion are limited to motions of the up... more Descriptions of shoulder kinematics during wheelchair propulsion are limited to motions of the upper arm due to the difficulty of measuring scapular movement in vivo. Using a digitizing stylus, the three-dimensional positions of three anatomical landmarks on the scapula were recorded for 10 manual wheelchair users in six different statically held hand positions (À30 , À15 , 0 , 15 , 30 , 60 ) on the pushrim. In each hand position, a motion analysis system recorded the coordinates of infrared markers on the arm and torso. Scapular, humeral, and torso angles were computed using an Euler angle decomposition method for each position relative to the torso. At the beginning of the push, the scapula was rotated slightly upward (1.5 ), minimally protracted (15 ), and maximally tipped forward (22 ). In addition, the humerus was maximally extended, abducted and internally rotated. As subjects moved forward along the pushrim, the protraction angle increased while the forward tipping angle decreased. The humerus became increasingly more flexed as the push progressed with small changes observed in humeral abduction and internal rotation. A stepwise multiple regression analysis procedure (po0:01) revealed that the torso, humeral flexion/extension and abduction angles are good predictors for estimating forward tipping and upward/downward rotation of the scapula. The regression equations enable researchers to estimate scapular orientation during propulsion which could provide further insight into specific biomechanical factors that lead to shoulder pathology.
Comparison of three different models to represent the wrist during wheelchair propulsion
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2001
Due to the high incidence of secondary wrist injury among manual wheelchair users, recent emphasi... more 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 degrees 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 degrees, 2.2 degrees, and 5.0 degrees for the midstyloid, de Leva, and floating joint center models, respectively. Extension angles were 22.3 degrees, 23.6 degrees, and 23.6 degrees, respectively. Mean maximum right radial deviation angles for the midstyloid, de Leva, and floating joint center models were 26.0 degrees, 26.9 degrees, and 45.1 degrees, respectively, and ulnar deviation angles were found to be 30.5 degrees, 38.8 degrees, and 10.2 degrees, respectively. This information is useful when comparing kinematic studies and further supports the need for consensual methodology.
Engineering Better Wheelchairs to Enhance Community Participation
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2000
With about 2.2 million Americans currently using wheeled mobility devices, wheelchairs are freque... more With about 2.2 million Americans currently using wheeled mobility devices, wheelchairs are frequently provided to people with impaired mobility to provide accessibility to the community. Individuals with spinal cord injuries, arthritis, balance disorders, and other conditions or diseases are typical users of wheelchairs. However, secondary injuries and wheelchair-related accidents are risks introduced by wheelchairs. Research is underway to advance wheelchair design to prevent or accommodate secondary injuries related to propulsion and transfer biomechanics, while improving safe, functional performance and accessibility to the community. This paper summarizes research and development underway aimed at enhancing safety and optimizing wheelchair design.
Clinical Biomechanics, 2006
Background. Trunk instability due to paralysis can have adverse effects on posture and function i... more Background. Trunk instability due to paralysis can have adverse effects on posture and function in a wheelchair. The purpose of this study was to record trunk muscle recruitment patterns using surface electromyography from unimpaired individuals during wheelchair propulsion under various propulsion speed conditions to be able to design trunk muscle stimulation patterns for actual wheelchair users with spinal cord injury.
Clinical Biomechanics, 2006
Background. Manual wheelchair users rely heavily on their upper limbs for independent mobility wh... more Background. Manual wheelchair users rely heavily on their upper limbs for independent mobility which likely leads to a high prevalence of shoulder pain and injury. The goal of this study was to examine the relationship between shoulder forces and moments experienced during wheelchair propulsion and shoulder pathology.
Assistive Technology, 2006
Manual wheelchair users commonly experience pain in their hands and wrists associated with the re... more Manual wheelchair users commonly experience pain in their hands and wrists associated with the repetitive stress of propulsion. The objective of this research was to examine the effect of an ergonomic wheelchair handrim as an intervention designed to reduce pain in the hands and wrists and improve functional outcomes for manual wheelchair users. Three studies were conducted to achieve this objective. In the first study, 10 individuals with paraplegia underwent a biomechanical analysis before and after a 2-week practice period with a Natural-Fit (NF) prototype ergonomic handrim. The biomechanical results showed that grip moments were reduced with the NF handrim prototype as compared to the subjects' current handrim (p Ͻ .1). Other biomechanical findings were mixed. In the second study, 46 manual wheelchair users who replaced their standard handrim with the commercially available NF handrim completed a questionnaire of retrospective measures of symptom severity. Average duration of use of the NF was 6 months. When asked to compare propelling with the NF to propelling with their prior handrims, 85% of respondents reported less pain in their hands and 80% reported less pain in their wrists. The third study was a replication and extension of Study 2: 82 manual wheelchair users who replaced their standard handrim with the NF completed retrospective symptom severity and functional status scales after using the NF for an average of 9 months. Results