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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 with the direction and amount of force applied, the time peak force was reached, push angle, and their stroke frequency between conditions. © 2012 Human Kinetics, Inc.

Effect of backrest height on wheelchair propulsion biomechanics for level and uphill conditions. Objective: To evaluate the effect of backrest height on wheelchair propulsion kinematics and kinetics. Design: An intervention study with repeated measures. Setting: University laboratory. Participants: Convenience sample included manual wheelchair users (N=36; 26 men and 10 women) with spinal cord injuries ranging from T8 to L2. Intervention: Participants propelled on a motor-driven treadmill for 2 conditions (level and slope of 3°) at a constant speed of 0.9m/s while using in turn a sling backrest fixed at 40.6cm (16in) high (high backrest) and a lower height set at 50% trunk length (low backrest). Main Outcome Measures: Cadence, stroke angle, peak shoulder extension angle, shoulder flexion/extension range of motion, and mechanical effective force. Results: Pushing with the low backrest height enabled greater range of shoulder motion (P<.01), increased stroke angle (P<.01), push time (P<.01), and reduced cadence (P=.01) regardless of whether the treadmill was level or sloped. Conclusions: A lower cadence can be achieved when pushing with a lower backrest, which decreases the risk of developing upper-limb overuse related injuries. However, postural support, comfort, and other activities of daily living must also be considered when selecting a backrest height for active, long-term wheelchair users. The improvements found when using the low backrest were found regardless of slope type. Pushing uphill demanded significantly higher resultant and tangential force, torque, mechanical effective force, and cadence. © 2012 by the American Congress of Rehabilitation Medicine.

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

Background: The objective of this study was to investigate differences in shoulder, elbow and hand kinetics while performing three different SPTs that varied in terms of hand and trunk positioning. Methods: Fourteen unimpaired individuals (8 male and 6 female) performed three variations of sitting pivot transfers in a random order from a wheelchair to a level tub bench. Two transfers involved a forward flexed trunk (head-hips technique) and the third with the trunk remaining upright. The two transfers involving a head hips technique were performed with two different leading hand initial positions. Motion analysis equipment recorded upper body movements and force sensors recorded hand reaction forces. Shoulder and elbow joint and hand kinetics were computed for the lift phase of the transfer. Findings: Transferring using either of the head hips techniques compared to the trunk upright style of transferring resulted in reduced superior forces at the shoulder (P < 0.002), elbow (P < 0.004) and hand (P < 0.013). There was a significant increase in the medial forces in the leading elbow (P = 0.049) for both head hip transfers and the trailing hand for the head hip technique with the arm further away from the body (P < 0.028). The head hip techniques resulted in higher shoulder external rotation, flexion and extension moments compared to the trunk upright technique (P < 0.021). Interpretation: Varying the hand placement and trunk positioning during transfers changes the load distribution across all upper limb joints. The results of this study may be useful for determining a technique that helps preserve upper limb function overtime. © 2011 Elsevier Ltd.

Medical rehabilitation and assistive technology are immersed in a world transitioning to a basis in evidence-based practice. Fortunately, there is a growing body of knowledge related to manual wheelchair mobility to form a basis for clinical decision making. The results from research studies are useful for designing better wheelchairs, fitting and training people appropriately, contributing to evidence-based-medicine and guiding future research. This review describes some of the work related to manual wheelchairs that has and is being conducted within the University of Pittsburgh and the Human Engineering Research Laboratories of the United States Department of Veterans Affairs, and its application. © 2010 Informa UK, Ltd.

For many wheelchair users, performing transfers is essential for achieving independence with daily activities. However, transfers are particularly straining on the upper limbs and may contribute to the development of pain and overuse injuries at the shoulder. The purpose of this study was to determine the muscular demands of seven bilateral muscles acting at the shoulder and elbow during level and non-level transfers with and without a gap separating the wheelchair and target surface. Fourteen men with spinal cord injury transferred from their own wheelchair to a 1) level bench, 2) level bench with a 10 cm gap, 3) higher bench (+10 cm), 4) higher bench with a 10 cm gap, 5) lower bench (-10 cm), and 6) lower bench with a 10 cm gap in a random order. The maximum surface EMG reached during transfers was normalized to the subject's maximum EMG value reached during maximum static contractions for each muscle. Gaps required greater recruitment of the biceps and anterior deltoid muscles (p < 0.05). The increased muscle activation observed with gaps is likely due in part to increased combined shoulder flexion and abduction and glenohumeral joint strain on the anterior wall. As a result, individuals with SCI should be advised to position their wheelchair as close as possible to the surface they intend to transfer. © 2010 The authors and IOS Press. All rights reserved.

OBJECTIVE: The primary aim of this study is to establish the validity of grayscale-based quantitative ultrasound (QUS) measures of the biceps and supraspinatus tendons. DESIGN: Nine QUS measures of the biceps and supraspinatus tendons were computed from ultrasound images collected from 67 manual wheelchair users. Shoulder pathology was measured using questionnaires, physical examination maneuvers, and a clinical ultrasound grading scale. RESULTS: Increased age, duration of wheelchair use, and body mass correlated with a darker and more homogenous tendon appearance. Subjects with pain during physical examination tests for biceps tenderness and acromioclavicular joint tenderness exhibited significantly different supraspinatus QUS values. Even when controlling for tendon depth, QUS measures of the biceps tendon differed significantly between subjects with healthy tendons, mild tendinosis, and severe tendinosis. Clinical grading of supraspinatus tendon health was correlated with QUS measures of the supraspinatus tendon. CONCLUSIONS: QUS is valid method to quantify tendinopathy and may allow for early detection of tendinosis. Manual wheelchair users are at a high risk for developing shoulder tendon pathology and may benefit from QUS-based research that focuses on identifying interventions designed to reduce this risk. Copyright © 2010 by Lippincott Williams & Wilkins.

Koontz AM, Brindle ED, Kankipati P, Feathers D, Cooper RA. Design features that affect the maneuverability of wheelchairs and scooters. Objective: To determine the minimum space required for wheeled mobility device users to perform 4 maneuverability tasks and to investigate the impact of selected design attributes on space. Design: Case series. Setting: University laboratory, Veterans Affairs research facility, vocational training center, and a national wheelchair sport event. Participants: The sample of convenience included manual wheelchair (MWC; n=109), power wheelchair (PWC; n=100), and scooter users (n=14). Intervention: A mock environment was constructed to create passageways to form an L-turn, 360°-turn in place, and a U-turn with and without a barrier. Passageway openings were increased in 5-cm increments until the user could successfully perform each task without hitting the walls. Structural dimensions of the device and user were collected using an electromechanical probe. Mobility devices were grouped into categories based on design features and compared using 1-way analysis of variance and post hoc pairwise Bonferroni-corrected tests. Main Outcome Measure: Minimum passageway widths for the 4 maneuverability tasks. Results: Ultralight MWCs with rear axles posterior to the shoulder had the shortest lengths and required the least amount of space compared with all other types of MWCs (P<.05). Mid-wheel-drive PWCs required the least space for the 360°-turn in place compared with front-wheel-drive and rear-wheel-drive PWCs (P<.01) but performed equally as well as front-wheel-drive models on all other turning tasks. PWCs with seat functions required more space to perform the tasks. Conclusions: Between 10% and 100% of users would not be able to maneuver in spaces that meet current Accessibility Guidelines for Buildings and Facilities specifications. This study provides data that can be used to support wheelchair prescription and home modifications and to update

Cowan RE, Nash MS, Collinger JL, Koontz AM, Boninger ML. Impact of surface type, wheelchair weight, and axle position on wheelchair propulsion by novice older adults. Objective: To examine the impact of surface type, wheelchair weight, and rear axle position on older adult propulsion biomechanics. Design: Crossover trial. Setting: Biomechanics laboratory. Participants: Convenience sample of 53 ambulatory older adults with minimal wheelchair experience (65-87y); men, n=20; women, n=33. Intervention: Participants propelled 4 different wheelchair configurations over 4 surfaces: tile, low carpet, high carpet, and an 8% grade ramp (surface, chair order randomized). Chair configurations included (1) unweighted chair with an anterior axle position, (2) 9.05kg weighted chair with an anterior axle position, (3) unweighted chair with a posterior axle position (Δ0.08m), and (4) 9.05kg weighted chair with a posterior axle position (Δ0.08m). Weight was added to a titanium folding chair, simulating the weight difference between very light and depot wheelchairs. Instrumented wheels measured propulsion kinetics. Main Outcome Measures: Average self-selected velocity, push frequency, stroke length, peak resultant and tangential force. Results: Velocity decreased as surface rolling resistance or chair weight increased. Peak resultant and tangential forces increased as chair weight increased, as surface resistance increased, and with a posterior axle position. The effect of a posterior axle position was greater on high carpet and the ramp. The effect of weight was constant, but was more easily observed on high carpet and ramp. The effects of axle position and weight were independent of one another. Conclusion: Increased surface resistance decreases self-selected velocity and increases peak forces. Increased weight decreases self-selected velocity and increases forces. Anterior axle positions decrease forces, more so on high carpet. The effects of weight and axle position are independen

Koontz AM, Roche BM, Collinger JL, Cooper RA, Boninger ML. Manual wheelchair propulsion patterns on natural surfaces during start-up propulsion. Objectives: To classify propulsion patterns over surfaces encountered in the natural environment during start-up and compare selected biomechanical variables between pattern types. Design: Case series. Setting: National Veterans Wheelchair Games, Minneapolis, MN, 2005. Participants: Manual wheelchair users (N=29). Intervention: Subjects pushed their wheelchairs from a resting position over high-pile carpet, over linoleum, and up a ramp with a 5° incline while propulsion kinematics and kinetics were recorded with a motion capture system and an instrumented wheel. Main Outcome Measures: Three raters classified the first 3 strokes as 1 of 4 types on each surface: arc, semicircular (SC), single looping over propulsion (SL), and double looping over propulsion (DL). The Fisher exact test was used to assess pattern changes between strokes and surface type. A multiple analysis of variance test was used to compare peak and average resultant force and moment about the hub, average wheel velocity, stroke frequency, contact angle, and distance traveled between stroke patterns. Results: SL was the most common pattern used during start-up propulsion (44.9%), followed by arc (35.9%), DL (14.1%), and SC (5.1%). Subjects who dropped their hands below the rim during recovery achieved faster velocities and covered greater distances (.016≤P≤.075) during start-up on linoleum and carpet and applied more force during start-up on the ramp compared with those who used an arc pattern (P=.066). Conclusions: Classifying propulsion patterns is a difficult task that should use multiple raters. In addition, propulsion patterns change during start-up, with an arc pattern most prevalent initially. The biomechanical findings in this study agree with current clinical guidelines that recommend training users to drop the hand below the pushrim during recovery.

Background. The objective of this study was to examine how surface electrical stimulation of trunk musculature influences the kinematic, kinetic, and metabolic characteristics, as well as shoulder muscle activity, during wheelchair propulsion. Methods. Eleven participants with spinal cord injury propelled their own wheelchairs on a dynamometer at a speed of 1.3 m/s for three 5-minute trials. During a propulsion trial, 1 of 3 stimulation levels (HIGH, LOW, and OFF) was randomly applied to the participantĝ€™s abdominal and back muscle groups with a surface functional electrical stimulation device. Propulsion kinetics, trunk kinematics, metabolic responses, and surface electromyographic (EMG) activity of 6 shoulder muscles were collected synchronously. Kinetic, kinematic, and EMG variables were recorded during 3 time intervals (30 seconds each) within a 5-minute trial. Metabolic variables were recorded through the entire 5-minute trial. Results. Participants with HIGH stimulation increased their gross mechanical efficiency (P =.05) during wheelchair propulsion. No differences were found in shoulder EMG activity, energy expenditure, and trunk motion between stimulation levels. Conclusion. Functional electrical stimulation on the trunk musculature has potential advantages in helping manual wheelchair users with spinal cord injury improve propulsion efficiency without placing additional demands on shoulder musculature.

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 (MUREMG), 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 MUREMG(%MUREMG). The overall peak %MUREMG and the area under the %MUREMG curve were selected as primary outcome measures. Similar peak %MUREMGs 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 %MUREMGs 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 %MUREMG 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 w

Collinger JL, Boninger ML, Koontz AM, Price R, Sisto SA, Tolerico ML, Cooper RA. Shoulder biomechanics during the push phase of wheelchair propulsion: a multisite study of persons with paraplegia. Objectives: To present a descriptive analysis and comparison of shoulder kinetics and kinematics during wheelchair propulsion at multiple speeds (self-selected and steady-state target speeds) for a large group of manual wheelchair users with paraplegia while also investigating the effect of pain and subject demographics on propulsion. Design: Case series. Setting: Three biomechanics laboratories at research institutions. Participants: Volunteer sample of 61 persons with paraplegia who use a manual wheelchair for mobility. Intervention: Subjects propelled their own wheelchairs on a dynamometer at 3 speeds (self-selected, 0.9m/s, 1.8m/s) while kinetic and kinematic data were recorded. Main Outcome Measures: Differences in demographics between sites, correlations between subject characteristics, comparison of demographics and biomechanics between persons with and without pain, linear regression using subject characteristics to predict shoulder biomechanics, comparison of biomechanics between speed conditions. Results: Significant increases in shoulder joint loading with increased propulsion velocity were observed. Resultant force increased from 54.4±13.5N during the 0.9m/s trial to 75.7±20.7N at 1.8m/s (P<.001). Body weight was the primary demographic variable that affected shoulder forces, whereas pain did not affect biomechanics. Peak shoulder joint loading occurs when the arm is extended and internally rotated, which may leave the shoulder at risk for injury. Conclusions: Body-weight maintenance, as well as other interventions designed to reduce the force required to propel a wheelchair, should be implemented to reduce the prevalence of shoulder pain and injury among manual wheelchair users. © 2008 American Congress of Rehabilitation Medicine and the American Academy of Ph

A multisite collaborative study is being conducted on the association between propulsion biomechanics and upper-limb injuries. This substudy compared subject characteristics and pushrim kinetics across three sites and identified early on in the main study any differences that could affect interpretation of the findings or data pooling. A total of 42 manual wheelchair users with paraplegia (14 from each site) performed 0.9 m/s and 1.8 m/s steady state propulsion trials and an acceleration-brake-coastdown trial on a wheelchair dynamometer while propulsion forces and moment about the hub were measured with a 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.

Price R, Ashwell ZR, Chang MW, Boninger ML, Koontz AM, Sisto SA. Upper-limb joint power and its distribution in spinal cord injured wheelchair users: steady-state self-selected speed versus maximal acceleration trials. Objective: To compare upper-limb joint power magnitude and distribution between the shoulder, elbow, and wrist during maximal acceleration (MAC) versus steady-state, self-selected speed (SSS) manual wheelchair propulsion. Design: Cross-sectional biomechanic study. Setting: Research university and teaching hospital. Participants: Volunteer sample of 13 manual wheelchair users with spinal cord injury below T1. Interventions: Not applicable. Main Outcome Measures: Propulsive joint power magnitude and fractional distribution among upper-limb joints. Results: Wilcoxon signed-rank testing revealed shoulder power was larger for MAC versus SSS (median peak, 101.5W; interquartile range [IQR], 74.6; median peak, 37.7W; IQR, 22.9; respectively) (P<.01). Elbow and wrist power were unchanged. Peak shoulder power fraction was larger for MAC versus SSS (median peak, 1.055; IQR, .110 vs peak, .870; IQR, .252) (P<.01). Peak elbow power fraction was smaller for MAC versus SSS (median peak, -.012; IQR, .144 vs peak, .146; IQR, .206) (P<.05). Peak wrist power fraction was smaller for MAC versus SSS (median peak, -.058; IQR, .057 vs peak, -.010; IQR, .150) (P<.05). Conclusions: Power at the shoulder was larger than at other joints. Peak shoulder joint power and power fraction was larger during MAC versus SSS propulsion. Elbow and wrist power fractions were smaller for MAC versus SSS propulsion. Higher joint power, present under MAC, may predispose manual wheelchair users to injury, particularly at the shoulder. © 2007 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.

The manual wheelchair has undergone much advancement over the past two decades. The purpose of this article is to provide an overview of the most significant advances in manual wheelchairs. These technological advances are now available in the clinical setting and should be recognized, discussed, and adopted by doctors, clinicians, engineers, funding sources, and, most important, consumers when the most appropriate manual wheelchair is being selected. © 2006 Thomas Land Publishers, Inc.

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 with the subjects' current handrim (p <.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 again confirmed that using the NF led to a reduction in the severity of symptoms and to improved functional outcomes. © 2006 Taylor & Francis Group, LLC.

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. Methods: Fourteen unimpaired subjects propelled a test wheelchair on a dynamometer system at two steady state speeds of 0.9 m/s and 1.8 m/s and acceleration from rest to their maximum speed. Lower back/abdominal surface electromyography and upper body movements were recorded for each trial. Based on the hand movement during propulsion, the propulsive cycle was further divided into five stages to describe the activation patterns. Findings: Both abdominal and back muscle groups revealed significantly higher activation at early push and pre-push stages when compared to the other three stages of the propulsion phase. With increasing propulsive speed, trunk muscles showed increased activation (P < 0.0001). Back muscle activity was significantly higher than abdominal muscle activity across the three speed conditions (P < 0.0005), with lower back muscles predominating. Interpretation: Abdominal and back muscle groups cocontracted at late recovery phase and early push phase to provide sufficient trunk stability to meet the demands of propulsion. This study provides an indication of the amount and duration of stimulation needed for a future application of electrical stimulation of the trunk musculature for persons with spinal cord injury. © 2006 Elsevier Ltd. All rights reserved.

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. © 2006 IEEE.

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 SMARTWheel 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 start-up 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.

Some aspects of assistive technology can be enhanced by the application of virtual reality. Although virtual simulation offers a range of new possibilities learning to navigate in a virtual environment is not equivalent to learning to navigate in the real world. Therefore, virtual reality simulation is advocated as a useful preparation for assessment and training within the physical environment. We are engaged in several efforts to develop virtual environments and devices for mobility skills assessment and training, exercise training, and environment assessment. Virtual reality offers wheelchair users a training tool in different risk-free environments without any indoor (e.g., walls, furniture, and stairs) and outdoor (e.g., curb cuts, uneven terrain, and street traffic) physical constraints. Virtual reality technology will probably become more common in the field of assistive technology, especially given the rapid expansion of gaming technology and the continued exponential growth of computing power. © 2005 Taylor & Francis Group, LLC.

Background/Objective: Previous investigations have identified muscular imbalance in the shoulder as a source of pain and injury in manual wheelchair users. Our aim was to determine whether a correlation exists between strength and pushrim biomechanical variables including: tangential (motive) force (Ft), radial force (Fr), axial force (Fz), total (resultant) force (FR), fraction of effective force (FEF), and cadence. Methods: Peak isokinetic shoulder strength (flexion [FLX], extension [EXT], abduction [ABD], adduction [ADD], internal rotation [IR], and external rotation [ER]) was tested in 22 manual wheelchair users with a BioDex system for 5 repetitions at 60°/s. Subjects then propelled their own manual wheelchair at 2 speeds, 0.9 m/s (2 mph) and 1.8 m/s (4 mph), for 20 seconds, during which kinematic (OPTOTRAK) and kinetic (SMARTWHEEL) data were collected. Peak isokinetic forces in the cardinal planes were correlated with pushrim biomechanical variables. Results: All peak torque strength variables correlated significantly (P ≤ 0.05) with Ft, Fr, and FR, but were not significantly correlated with Fz, FEF, or cadence. Finally, there were no relationships found between muscle strength ratios (for example, FLX/EXT) and Ft, Fr, FR, Fz, or FEF. Conclusion: There was a correlation between strength and force imparted to the pushrim among wheelchair users; however, there was no correlation found in wheelchair propulsion or muscle imbalance. Clinicians should be aware of this, and approach strength training and training in wheelchair propulsion techniques separately.

Fay BT, Boninger ML, Fitzgerald SG, Souza AL, Cooper RA, Koontz AM. Manual wheelchair pushrim dynamics in people with multiple sclerosis. Arch Phys Med Rehabil 2004;85:935-42. Objectives To define differences in pushrim dynamics during manual wheelchair propulsion by users with multiple sclerosis (MS) relative to 2 control groups of subjects with spinal cord injury (SCI) and no disability (ND) and to investigate changes in propulsion biomechanics at different speeds and with fatigue. Design Case-control. Setting Biomechanics laboratory. Participants A convenience sample of 42 people, 8 women and 6 men per group. Interventions Not applicable. Main outcome measures The propulsion pattern, mean maximum speed, percentage of time in push and recovery phases, push angle, push frequency, mean maximum resultant pushrim force, mean work and push cycle, and hand-to-pushrim coupling and decoupling effects. Results The MS groups tended to use an arcing propulsion pattern more than did the control groups (Pmax=.003). The MS group pushed at a lower mean maximum velocity (v) when allowed to choose the speed of propulsion (vMS, .67±.20m/s; vSCI, 1.10±0.23m/s; P=.001), when asked to push at 1m/s (vMS, .91±.26m/s; vSCI, 1.12±0.11m/s; vND, 1.05±0.13m/s; P=.010), and were unable to maintain a self-selected speed during a 5-minute trial (Δv MS, .15±.02m/s; ΔvND, .03±.06m/s; P<.001). The MS group spent a higher proportion of time in the push phase of propulsion (Pmax=.001). In general, the MS group had smaller push angles, but push frequencies similar to the controls. Statistically adjusted MS group pushrim forces and work per push measures varied depending on context, but in all trials the MS group displayed a braking effect when grasping and releasing the pushrim. The MS group had declines in most measures when pushing at a self-selected speed for 5 minutes. In all trials, the MS group was more likely to display asymmetry between right and left sides in biomechanic parameters. Conclusi

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 (-30°, -15°, 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 (p<0.01) 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.

Boninger ML, Impink BG, Cooper RA, Koontz AM. Relation between median and ulnar nerve function and wrist kinematics during wheelchair propulsion. Arch Phys Med Rehabil 2004;85:1141-5. Objective To investigate the relation between median and ulnar nerve health and wrist kinematics in wheelchair users. Design Case series. Setting Biomechanics laboratory and electrodiagnostic laboratory at a Veterans Health Administration medical center and a university hospital, respectively. Participants Thirty-five people with spinal cord injury who use manual wheelchairs. Intervention Subjects propelled their own wheelchair on a dynamometer at 0.9 and 1.8m/s. Bilateral biomechanic data were obtained by using force and moment sensing pushrims and a kinematic system. Bilateral median and ulnar nerve conduction studies were also completed. Main outcome measures Wrist flexion, extension, radial and ulnar deviation peaks, and ranges of motion (ROMs) as related to median and ulnar motor and sensory amplitudes. A secondary analysis included peak pushrim forces and moments and stroke frequency. Results There was a significant, positive correlation between flexion and extension ROM and both ulnar motor amplitude (r=.383, P<.05) and median motor amplitude (r=.361, P<.05). Conclusions Contrary to our hypothesis, subjects using a greater ROM showed better nerve function than subjects propelling with a smaller ROM. Subjects using a larger ROM used less force and fewer strokes to propel their wheelchairs at a given speed. It is possible that long, smooth strokes may benefit nerve health in manual wheelchair users. © 2004 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.

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.

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

The primary objective of this study was to examine the kinematics and kinetics of the shoulder during wheelchair propulsion at a slow and moderate speed. Twenty-seven individuals with paraplegia propelled their wheelchairs at speeds of 0.9 m/s and 1.8 m/s while a motion analysis system captured movements of their upper limbs and SMARTWheelS simultaneously recorded their pushrim kinetics. Intraclass R correlation and Cronbach's coefficient alpha statistics revealed that all shoulder parameters were stable and consistent between strokes and speeds. The shoulder exhibited a greater range of motion, and forces and moments at the shoulder were 1.2 to 2.0 times greater (p < 0.05) during the 1.8 m/s speed trial. Peak posterior forces occurred near the end of the propulsion phase, and at the same time, the shoulder was maximally flexed and minimally abducted (p > 0.1). Shoulder positioning and the associated peak shoulder loads during propulsion may be important indicators for identifying manual wheelchair users at risk for developing shoulder pain and injury.

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

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

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° 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°, 2.2°, and 5.0° for the midstyloid, de Leva, and floating joint center models, respectively. Extension angles were 22.3°, 23.6°, and 23.6°, respectively. Mean maximum right radial deviation angles for the midstyloid, de Leva, and floating joint center models were 26.0°, 26.9°, and 45.1°, respectively, and ulnar deviation angles were found to be 30.5°, 38.8°, and 10.2°, respectively. This information is useful when comparing kinematic studies and further supports the need for consensual methodology.

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 SMARTWheels, 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.