The Effect of Visual Biofeedback on the Propulsion Effectiveness of Experienced Wheelchair Users

Effect of Haptic Training During Manual Wheelchair Propulsion on Shoulder Joint Reaction Moments

Background

Manual wheelchair propulsion remains a very ineffective means of locomotion in terms of energy cost and mechanical efficiency, as more than half of the forces applied to the pushrim do not contribute to move the wheelchair forward. Manual wheelchair propulsion training using the haptic biofeedback has shown an increase in mechanical efficiency at the handrim level. However, no information is available about the impact of this training on the load at the shoulders. We hypothesized that increasing propulsion mechanical efficiency by 10% during propulsion would not yield clinically significant augmentation of the load sustained at the shoulders.

Methods

Eighteen long-term manual wheelchair users with a spinal cord injury propelled a manual wheelchair over a wheelchair simulator offering the haptic biofeedback. Participants were asked to propel without the Haptic Biofeedback (HB) and, thereafter, they were subjected to five training blocks BL1–BL5 of 3 min in a random order with the haptic biofeedback targeting a 10% increase in force effectiveness. The training blocs such as BL1, BL2 BL3, BL4, and BL5 correspond, respectively, to a resistant moment of 5, 10, 15, 20, and 25%. Pushrim kinetics, shoulder joint moments, and forces during the propulsive cycle of wheelchair propulsion were assessed for each condition.

Results

The tangential force component increases significantly by 74 and 87%, whereas value for the mechanical effective force increases by 9% between the pretraining and training blocks BL3. The haptic biofeedback resulted in a significant increase of the shoulder moments with 1–7 Nm.

Conclusion

Increases in shoulder loads were found for the corresponding training blocks but even though the percentage of the increase seems high, the amplitude of the joint moment remains under the values of wheelchair propulsion found in the literature. The use of the HB simulator is considered here as a safe approach to increase mechanical effectiveness. However, the longitudinal impact of this enhancement remains unknown for the impact on the shoulder joint. Future studies will be focused on this impact in terms of shoulder risk injury during manual wheelchair propulsion.

Augmented feedback for manual wheelchair propulsion technique training in a virtual reality simulator

BACKGROUND

Motor learning of appropriate manual wheelchair propulsion is critical, as incorrect technique elevates risk for upper extremity pain. Virtual reality simulators allow users to practice this complex task in a safe and realistic environment. Additionally, augmented feedback (AF) may be provided in order to optimize learning. The purpose of this study was to investigate the effects of providing AF with various delivery schedules on motor learning and transfer of this skill to over-ground propulsion.

METHODS

Thirty healthy young adults were randomly assigned to three groups. During a virtual reality propulsion training session, the high-frequency AF group received AF in the form of knowledge of performance throughout all propulsion training; the faded AF group received this AF in a faded schedule (high relative frequency of AF early in practice, with relative frequency of AF provision diminishing throughout practice); and the control group underwent training with no AF. Propulsion assessments were performed at baseline and 48 h after practice in both virtual and real environments to measure retention and transfer, respectively.

RESULTS

Compared to the control group, both feedback groups exhibited significant improvements in contact angle and push frequency in both environments after training. Small, non-significant between-group differences were also found between the high-frequency and faded feedback groups.

CONCLUSION

Virtual reality training is an effective learning intervention for acquisition, retention, and transfer of appropriate manual wheelchair propulsion technique when such training includes AF regarding propulsion biomechanics.

Effects of Motor Skill-Based Training on Wheelchair Propulsion Biomechanics in Older Adults: A Randomized Controlled Trial

OBJECTIVE

To identify whether motor skill-based training improves wheeling biomechanics in older adults and whether transfer or retention occurs.

DESIGN

Randomized controlled trial.

SETTING

Human mobility laboratory.

PARTICIPANTS

Able-bodied older adults 50 years and older deemed ready to participate in physical activity (N=34).

INTERVENTION

Participants were randomized to 1 of 3 groups: experimental group with 6 motor skill-based training sessions, active control group with dose-matched uninstructed practice, and the inactive control group (no training or practice). The experimental group's training sessions consisted of two 5-minute blocks of wheelchair propulsion training, separated by a 5-minute break, for a total of 60 minutes of wheeling. Breaks included education and discussion related to wheelchair propulsion. Training focused on increasing push angle, decreasing push frequency, decreasing negative braking forces, and using a circular wheeling pattern with smooth pushes.

MAIN OUTCOME MEASURES

Temporal spatial and kinetic variables (ie, push angle, push frequency, total and tangential forces, negative force) were evaluated during steady-state wheeling and biomechanical variables were assessed with the SmartWheel Clinical Protocol to identify transfer.

RESULTS

The training group significantly increased push angle and decreased push frequency compared with the practice (P<.05) and control groups (P<.05), which were retained over time and transferred to overground wheeling on tile (P≤.05). The dose-matched practice group did not differ from the inactive control group for any variables (P>.05).

CONCLUSIONS

Older adults improve select biomechanical variables following motor skill-based training, which are retained over time and transfer to overground wheeling. Participants in the active control group did not improve with uninstructed practice compared with the inactive control group.

Training Youth With SCI to Improve Efficiency and Biomechanics of Wheelchair Propulsion: A Pilot Study

Background: Long-term manual wheelchair users are at an increased risk of developing upper extremity (UE) joint pain and injuries due to the repetitive nature of wheelchair propulsion. Youth who sustain spinal cord injuries (SCIs) may be at even greater risk due to the many years they may be wheelchair dependent. There has been a decreasing trend in duration of initial rehabilitation, therefore little time is spent on training of proper wheelchair propulsion. An objective evaluation along with proper training may help prevent the risk of UE pain and injuries over time. Objective: To develop a training program to improve the efficiency and biomechanics of wheelchair propulsion in youth with SCI and evaluate changes made following propulsive training. Methods: Manual wheelchair users between 4 and 21 years old with SCI were recruited from one hospital. Demographic and clinical measures were collected and the subjects completed the Wheelchair User's Shoulder Pain Index. SmartWheel metrics were collected at baseline and following propulsive training on a roller system. Analyses assessed differences in SmartWheel metrics pre and post training. Results: The 23 participants were between 7 and 19 years of age; 57% were male and 69% with paraplegia. Significant improvements were found for SmartWheel metrics of peak backwards force that improved from -3.08 Newtons (N) ± 2.1 pre training to -2.37 N ± 1.9 (p = .041) post training and for push mechanical effectiveness that improved from .575 ± .14 at baseline to .631 ± .17 post training (p = .033). Conclusion: Our results suggest that an objective wheelchair assessment and propulsive training may be a valuable tool for youth with SCI.

A motor learning approach to training wheelchair propulsion biomechanics for new manual wheelchair users: A pilot study

CONTEXT/OBJECTIVE

Developing an evidence-based approach to teaching wheelchair skills and proper propulsion for everyday wheelchair users with a spinal cord injury (SCI) is important to their rehabilitation. The purpose of this project was to pilot test manual wheelchair training based on motor learning and repetition-based approaches for new manual wheelchair users with an SCI.

DESIGN

A repeated measures within-subject design was used with participants acting as their own controls.

METHODS

Six persons with an SCI requiring the use of a manual wheelchair participated in wheelchair training. The training included nine 90-minute sessions. The primary focus was on wheelchair propulsion biomechanics with a secondary focus on wheelchair skills.

OUTCOME MEASURES

During Pretest 1, Pretest 2, and Posttest, wheelchair propulsion biomechanics were measured using the Wheelchair Propulsion Test and a Video Motion Capture system. During Pretest 2 and Posttest, propulsion forces using the WheelMill System and wheelchair skills using the Wheelchair Skills Test were measured.

RESULTS

Significant changes in area of the push loop, hand-to-axle relationship, and slope of push forces were found. Changes in propulsion patterns were identified post-training. No significant differences were found in peak and average push forces and wheelchair skills pre- and post-training.

CONCLUSIONS

This project identified trends in change related to a repetition-based motor learning approach for propelling a manual wheelchair. The changes found were related to the propulsion patterns used by participants. Despite some challenges associated with implementing interventions for new manual wheelchair users, such as recruitment, the results of this study show that repetition-based training can improve biomechanics and propulsion patterns for new manual wheelchair users.

A systematic review: the influence of real time feedback on wheelchair propulsion biomechanics

BACKGROUND

Clinical guidelines recommend that, in order to minimize upper limb injury risk, wheelchair users adopt a semi-circular pattern with a slow cadence and a large push arc.

OBJECTIVES

To examine whether real time feedback can be used to influence manual wheelchair propulsion biomechanics.

REVIEW METHODS

Clinical trials and case series comparing the use of real time feedback against no feedback were included. A general review was performed and methodological quality assessed by two independent practitioners using the Downs and Black checklist. The review was completed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines.

RESULTS

Six papers met the inclusion criteria. Selected studies involved 123 participants and analysed the effect of visual and, in one case, haptic feedback. Across the studies it was shown that participants were able to achieve significant changes in propulsion biomechanics, when provided with real time feedback. However, the effect of targeting a single propulsion variable might lead to unwanted alterations in other parameters. Methodological assessment identified weaknesses in external validity.

CONCLUSIONS

Visual feedback could be used to consistently increase push arc and decrease push rate, and may be the best focus for feedback training. Further investigation is required to assess such intervention during outdoor propulsion. Implications for Rehabilitation Upper limb pain and injuries are common secondary disorders that negatively affect wheelchair users' physical activity and quality of life. Clinical guidelines suggest that manual wheelchair users should aim to propel with a semi-circular pattern with low a push rate and large push arc in the range in order to minimise upper limbs' loading. Real time visual and haptic feedback are effective tools for improving propulsion biomechanics in both complete novices and experienced manual wheelchair users.

Sensewheel: an adjunct to wheelchair skills training

The purpose of this Letter was to investigate the influence of real-time verbal feedback to optimise push arc during over ground manual wheelchair propulsion. Ten healthy non-wheelchair users pushed a manual wheelchair for a distance of 25 m on level paving, initially with no feedback and then with real-time verbal feedback aimed at controlling push arc within a range of 85°-100°. The real-time feedback was provided by a physiotherapist walking behind the wheelchair, viewing real-time data on a tablet personal computer received from the Sensewheel, a lightweight instrumented wheelchair wheel. The real-time verbal feedback enabled the participants to significantly increase their push arc. This increase in push arc resulted in a non-significant reduction in push rate and a significant increase in peak force application. The intervention enabled participants to complete the task at a higher mean velocity using significantly fewer pushes. This was achieved via a significant increase in the power generated during the push phase. This Letter identifies that a lightweight instrumented wheelchair wheel such as the Sensewheel is a useful adjunct to wheelchair skills training. Targeting the optimisation of push arc resulted in beneficial changes in propulsion technique.

Identifying key experience-related differences in over-ground manual wheelchair propulsion biomechanics

OBJECTIVES

The purpose of this study was to investigate technique differences between expert and novice manual wheelchair users during over-ground wheelchair propulsion.

METHOD

Seven experts (spinal cord injury level between T5 and L1) and six novices (non-wheelchair users) pushed a manual wheelchair over level ground, a 2.5% cross slope and up a 6.5% incline (7.2 m length) and 12% incline (1.5 m length). Push rim kinetics, trunk and shoulder kinematics and muscle activity level were measured.

RESULTS

During the level and cross slope tasks, the experts completed the tasks with fewer pushes by applying a similar push rim moment over a greater push arc, demonstrating lower muscle activity. During the incline tasks, the experts required fewer pushes and maintained a greater average velocity, generating greater power by applying a similar push rim moment over a greater push arc with greater angular velocity, demonstrating greater trunk flexion and higher shoulder muscle activity.

CONCLUSIONS

This study identifies experience-related differences during over-ground manual wheelchair propulsion. These differences are particularly evident during incline propulsion, with the experts generating significantly greater power to maintain a higher velocity.

Effects of visual feedback-induced variability on motor learning of handrim wheelchair propulsion

BACKGROUND

It has been suggested that a higher intra-individual variability benefits the motor learning of wheelchair propulsion. The present study evaluated whether feedback-induced variability on wheelchair propulsion technique variables would also enhance the motor learning process. Learning was operationalized as an improvement in mechanical efficiency and propulsion technique, which are thought to be closely related during the learning process.

METHODS

17 Participants received visual feedback-based practice (feedback group) and 15 participants received regular practice (natural learning group). Both groups received equal practice dose of 80 min, over 3 weeks, at 0.24 W/kg at a treadmill speed of 1.11 m/s. To compare both groups the pre- and post-test were performed without feedback. The feedback group received real-time visual feedback on seven propulsion variables with instruction to manipulate the presented variable to achieve the highest possible variability (1st 4-min block) and optimize it in the prescribed direction (2nd 4-min block). To increase motor exploration the participants were unaware of the exact variable they received feedback on. Energy consumption and the propulsion technique variables with their respective coefficient of variation were calculated to evaluate the amount of intra-individual variability.

RESULTS

The feedback group, which practiced with higher intra-individual variability, improved the propulsion technique between pre- and post-test to the same extent as the natural learning group. Mechanical efficiency improved between pre- and post-test in the natural learning group but remained unchanged in the feedback group.

CONCLUSION

These results suggest that feedback-induced variability inhibited the improvement in mechanical efficiency. Moreover, since both groups improved propulsion technique but only the natural learning group improved mechanical efficiency, it can be concluded that the improvement in mechanical efficiency and propulsion technique do not always appear simultaneously during the motor learning process. Their relationship is most likely modified by other factors such as the amount of the intra-individual variability.

The development of an instrumented wheelchair propulsion testing and training device

Researchers have used several types of testing devices and training surfaces to examine wheelchair propulsion. Testing and training wheelchair users on the actual surface of interest, such as tile floors or ramps, is ideal but difficult. Devices such as treadmills, dynamometers, and ergometers allow for researchers and clinicians to observe wheelchair users in a controlled space. However, these devices often do not have the ability to realistically simulate the environment. This methodological article describes the instrumentation, development and function of a wheelchair dynamometer system, the WheelMill System (WMS), a uniquely adjustable roller system for wheelchairs. Three participants wheeled on the WMS, over a tile surface and up two different graded slopes with the SmartWheel to compare speed and forces. The WMS reasonably simulated propulsion over a tile floor, though the participants' speed was slightly faster on tile, and the peak forces for each propulsion stroke varied more on tile than on the WMS. For the slopes, the speed oscillated over a greater range and was slower, and the measured peak forces were higher than the values measured on the WMS. The WMS may have several applications, though additional studies on a greater and more diverse population are needed.

Force Application During Handcycling and Handrim Wheelchair Propulsion: An Initial Comparison

The aim of the study was to evaluate the external applied forces, the effectiveness of force application and the net shoulder moments of handcycling in comparison with handrim wheelchair propulsion at different inclines. Ten able-bodied men performed standardized exercises on a treadmill at inclines of 1%, 2.5% and 4% with an instrumented handbike and wheelchair that measured three-dimensional propulsion forces. The results showed that during handcycling significantly lower mean forces were applied at inclines of 2.5% (P< .001) and 4% (P< .001) and significantly lower peak forces were applied at all inclines (1%:P= .014, 2.5% and 4%:P< .001). At the 2.5% incline, where power output was the same for both devices, total forces (mean over trial) of 22.8 N and 27.5 N and peak forces of 40.1 N and 106.9 N were measured for handbike and wheelchair propulsion. The force effectiveness did not differ between the devices (P= .757); however, the effectiveness did increase with higher inclines during handcycling whereas it stayed constant over all inclines for wheelchair propulsion. The resulting peak net shoulder moments were lower for handcycling compared with wheelchair propulsion at all inclines (P< .001). These results confirm the assumption that handcycling is physically less straining.

Reconfiguration of the upper extremity relative to the pushrim affects load distribution during wheelchair propulsion

OBJECTIVE

Repetitive loading during manual wheelchair propulsion (WCP) is associated with overuse injury to the upper extremity (UE). The aim of this study was to determine how RF redirection and load distribution are affected by changes upper extremity kinematic modifications associated with modifications in seat positions during a WCP task. The aim of this study was to determine how RF redirection and load distribution are affected by upper extremity kinematic changes associated with seat position adjustment during a WCP task.

DESIGN

Dynamic simulations using an experiment-based multi-link inverse dynamics model were used to generate solutions for redistributing UE mechanical load in different seating positions without decrements in WCP task performance.

METHODS

Experimental RF and kinematic data were collected for one subject propelling at a self-selected speed and used as input into the model. Shoulder/axle distance, wrist angular position, and RF direction were systematically modified to simulate how the mechanical demand imposed on the upper extremity (elbow and shoulder net joint moments (NJMs) and net joint forces) may vary.

RESULTS

Load distribution depended on UE orientation relative to the wheel. At peak force, lower shoulder/axle distances and more anterior wrist positions on the pushrim allowed for more extended elbow positions and reduced total NJM load.

INTERPRETATION

Simulation results incorporating subject-specific data may provide mechanically based information to guide clinical interventions that aim to maintain WCP performance and redistribute load by modifying RF direction, seat configuration and hand/rim interaction.

Effect of workload setting on propulsion technique in handrim wheelchair propulsion

OBJECTIVE

To investigate the influence of workload setting (speed at constant power, method to impose power) on the propulsion technique (i.e. force and timing characteristics) in handrim wheelchair propulsion.

METHOD

Twelve able-bodied men participated in this study. External forces were measured during handrim wheelchair propulsion on a motor driven treadmill at different velocities and constant power output (to test the forced effect of speed) and at power outputs imposed by incline vs. pulley system (to test the effect of method to impose power). Outcome measures were the force and timing variables of the propulsion technique.

RESULTS

FEF and timing variables showed significant differences between the speed conditions when propelling at the same power output (p < 0.01). Push time was reduced while push angle increased. The method to impose power only showed slight differences in the timing variables, however not in the force variables.

CONCLUSIONS

Researchers and clinicians must be aware of testing and evaluation conditions that may differently affect propulsion technique parameters despite an overall constant power output.

Simulated effect of reaction force redirection on the upper extremity mechanical demand imposed during manual wheelchair propulsion

BACKGROUND

Manual wheelchair propulsion is associated with overuse injuries of the shoulder. Reaction force redirection relative to upper extremity segments was hypothesized as a means to redistribute mechanical load imposed on the upper extremity without decrements in wheelchair propulsion performance.

METHODS

Two individuals performed wheelchair propulsion under simulated inclined (graded) conditions using self-selected control strategies. Upper extremity kinematics and reaction forces applied to the wheel were quantified and used as input into an experiment-based multi-link inverse dynamics model that incorporates participant-specific experimental results. Reaction force direction was systematically modified to determine the mechanical demand imposed on the upper extremity (elbow and shoulder net joint moments and net joint forces) during wheelchair propulsion. Results were presented as solution spaces to examine the upper extremity load distribution characteristics within and between participants across a range of reaction force directions.

FINDINGS

Redirection of the reaction force relative to the upper extremity segments provides multiple solutions for redistributing mechanical demand across the elbow and shoulder without decrements in manual wheelchair propulsion performance. The distribution of load across RF directions was participant specific and was found to vary with time during the push phase.

INTERPRETATION

Solution spaces provide a mechanical basis for individualized interventions that aim to maintain function and redistribute load away from structures at risk for injury (e.g. reduce demand imposed on shoulder flexors (reduce shoulder net joint moment) or reduce potential for impingement (reduce shoulder net joint force).

Wheelchairs propulsion analysis: review

OBJECTIVES: To analyze aspects related with wheelchair propulsion. MATERIALS AND METHODS: In order to delineate this review the search for information was carried out within electronics databases, using the following descriptors: "wheelchair propulsion", "wheelchair biomechanics" e "wheelchair users". Full papers published in English and French were included in the study. RESULTS: The wheelchair propulsion is a complex movement that requires the execution of repeated bi manual forces applications during a short time period. In this movement high levels of force must be produced due to the bad mechanical performance of the wheelchair. Could be characterized that wheelchair users are not satisfied with their wheelchair, the places are not adapted to their presence and lack of specific criteria for the adjustment of this equipment. The main points to look at are the seat height in relation to elbow flexion (100-120 degrees) with his hand in the propulsion rim and tire pressure. The semicircular mode of technique propulsion seems to be more appropriate; in this pattern the wheelchair user returns his hand under the rim after propulsion. Efforts in wheelchairs are high and the incidence of injuries in wheelchair users is high. CONCLUSION: One can conclude that in spite of researchers’ efforts there are still many divergences between topics and methods of evaluation, what makes difficult to apply the experimental results to the wheelchairs users’ daily life.

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 0.9 m/s while using in turn a sling backrest fixed at 40.6 cm (16 in) 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.

BIOMECHANICS OF WHEELCHAIR PROPULSION

With progress of modern technology, manually-propelled wheelchairs are still of importance for individuals with mobility impairments. The repeated wheelchair propulsion and strenuous daily activities cause high loads and thus injuries on the upper extremity joints. Over the past few years, a considerable number of studies have been made on biomechanical analysis of wheelchair propulsion and wheelchair-related activities. Thorough investigation of biomechanics during wheelchair propulsion enhances comprehension of mechanism of injuries and provides information to improve wheelchair design and fitting. Numerous investigations have been made to demonstrate factors which cause low effectiveness of force application and inefficiency of movements. Emphasis was also placed on developing analytical models to simulate wheelchair propulsion.

Comparison between overground and dynamometer manual wheelchair propulsion

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.

Effects of 4-weeks of asynchronous hand-rim wheelchair practice on mechanical efficiency and timing

PURPOSE

To investigate the consequence on gross mechanical efficiency (GE), arm frequency and sub-maximal performance, of paced and unpaced practice during asynchronous hand-rim wheelchair propulsion.

METHODS

Twenty-five able-bodied participants performed five, 4-min exercise bouts at 1.7 m/s, at the freely chosen frequency (FCF) and four paced arm frequencies of 60, 80, 120 and 140% FCF. GE, arm frequency and measures of sub-maximal performance were determined. Participants were assigned to an unpaced (FCF, N = 9), paced (80% FCF, N = 8) or control (CON, N = 8) no practice group. The FCF and 80% FCF groups received 4-weeks (unpaced and paced, respectively) propulsion practice (three sessions·per wk, four 4 min/trials; 33-35 W) at 1.7 m/s on a wheelchair ergometer. Following practice, the pre-testing protocol was repeated.

RESULTS

Mean GE showed a relative increase in both experimental groups (21 and 17%; FCF and 80% FCF respectively; p = 0.001) compared to no change in CON (-1.5%). The FCF arm frequency decreased in both experimental groups (p = 0.001), with larger changes evident following FCF practice.

CONCLUSION

Four weeks of unpaced or paced practice had a beneficial effect on GE. This improvement seems to be associated with a reduction in arm frequency.

The influence of altering push force effectiveness on upper extremity demand during wheelchair propulsion

Manual wheelchair propulsion has been linked to a high incidence of overuse injury and pain in the upper extremity, which may be caused by the high load requirements and low mechanical efficiency of the task. Previous studies have suggested that poor mechanical efficiency may be due to a low effective handrim force (i.e. applied force that is not directed tangential to the handrim). As a result, studies attempting to reduce upper extremity demand have used various measures of force effectiveness (e.g., fraction effective force, FEF) as a guide for modifying propulsion technique, developing rehabilitation programs and configuring wheelchairs. However, the relationship between FEF and upper extremity demand is not well understood. The purpose of this study was to use forward dynamics simulations of wheelchair propulsion to determine the influence of FEF on upper extremity demand by quantifying individual muscle stress, work and handrim force contributions at different values of FEF. Simulations maximizing and minimizing FEF resulted in higher average muscle stresses (23% and 112%) and total muscle work (28% and 71%) compared to a nominal FEF simulation. The maximal FEF simulation also shifted muscle use from muscles crossing the elbow to those at the shoulder (e.g., rotator cuff muscles), placing greater demand on shoulder muscles during propulsion. The optimal FEF value appears to represent a balance between increasing push force effectiveness to increase mechanical efficiency and minimize upper extremity demand. Thus, care should be taken in using force effectiveness as a metric to reduce upper extremity demand.

Hand rim wheelchair propulsion training using biomechanical real-time visual feedback based on motor learning theory principles

BACKGROUND/OBJECTIVE

As considerable progress has been made in laboratory-based assessment of manual wheelchair propulsion biomechanics, the necessity to translate this knowledge into new clinical tools and treatment programs becomes imperative. The objective of this study was to describe the development of a manual wheelchair propulsion training program aimed to promote the development of an efficient propulsion technique among long-term manual wheelchair users.

METHODS

Motor learning theory principles were applied to the design of biomechanical feedback-based learning software, which allows for random discontinuous real-time visual presentation of key spatiotemporal and kinetic parameters. This software was used to train a long-term wheelchair user on a dynamometer during 3 low-intensity wheelchair propulsion training sessions over a 3-week period. Biomechanical measures were recorded with a SmartWheel during over ground propulsion on a 50-m level tile surface at baseline and 3 months after baseline.

RESULTS

Training software was refined and administered to a participant who was able to improve his propulsion technique by increasing contact angle while simultaneously reducing stroke cadence, mean resultant force, peak and mean moment out of plane, and peak rate of rise of force applied to the pushrim after training.

CONCLUSIONS

The proposed propulsion training protocol may lead to favorable changes in manual wheelchair propulsion technique. These changes could limit or prevent upper limb injuries among manual wheelchair users. In addition, many of the motor learning theory-based techniques examined in this study could be applied to training individuals in various stages of rehabilitation to optimize propulsion early on.

The influence of verbal training and visual feedback on manual wheelchair propulsion

PURPOSE

To determine if verbal training with visual feedback improved manual wheelchair propulsion; to examine propulsion differences between an individual with paraplegia and an individual with tetraplegia.

METHOD

Quasi-experimental study: Nine manual wheelchair-using adults participated in propulsion assessments and training. Baseline propulsion performance was measured on several tasks on different surfaces. Participants were trained on a wheelchair treadmill with verbal and visual feedback to increase push length, reduce push frequency and to modify propulsion pattern. Handrim biomechanics were measured with an instrumented wheel. Changes in propulsion were assessed. Differences in propulsion characteristics between a participant with paraplegia and a participant with tetraplegia were examined.

RESULTS

Push length increased (p < 0.05), push frequency decreased (p < 0.01) and peak (p < 0.05) and average (p < 0.01) forces increased immediately after training. These changes were not sustained over time. Graphic representations showed differences in propulsion characteristics between a participant with paraplegia and a participant with tetraplegia.

CONCLUSIONS

Verbal training may produce changes in push biomechanics of manual wheelchair users. Longer training periods may be needed to sustain propulsion changes. Findings from this study support other studies that have shown propulsion differences between people with tetraplegia and paraplegia. Propulsion training for populations with upper-extremity impairments warrants further study.

Is effective force application in handrim wheelchair propulsion also efficient?

BACKGROUND

Efficiency in manual wheelchair propulsion is low, as is the fraction of the propulsion force that is attributed to the moment of propulsion of the wheelchair. In this study we tested the hypothesis that a tangential propulsion force direction leads to an increase in physiological cost, due to (1) the sub-optimal use of elbow flexors and extensors, and/or (2) the necessity of preventing of glenohumeral subluxation.

METHODS

Five able-bodied and 11 individuals with a spinal cord injury propelled a wheelchair while kinematics and kinetics were collected. The results were used to perform inverse dynamical simulations with input of (1) the experimentally obtained propulsion force, and (2) only the tangential component of that force.

FINDINGS

In the tangential force condition the physiological cost was over 30% higher, while the tangential propulsion force was only 75% of the total experimental force. According to model estimations, the tangential force condition led to more co-contraction around the elbow, and a higher power production around the shoulder joint. The tangential propulsion force led to a significant, but small 4% increase in necessity for the model to compensate for glenohumeral subluxation, which indicates that this is not a likely cause of the decrease in efficiency.

INTERPRETATION

The present findings support the hypothesis that the observed force direction in wheelchair propulsion is a compromise between efficiency and the constraints imposed by the wheelchair-user system. This implies that training should not be aimed at optimization of the propulsion force, because this may be less efficient and more straining for the musculoskeletal system.

Biomechanic evaluation of upper-extremity symmetry during manual wheelchair propulsion over varied terrain

OBJECTIVE

To evaluate upper-extremity symmetry during wheelchair propulsion across multiple terrain surfaces.

DESIGN

Case series.

SETTING

A biomechanics laboratory and the general community.

PARTICIPANTS

Manual wheelchair users (N=12).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Symmetry indexes for the propulsion moment, total force, tangential force, fractional effective force, time-to-peak propulsion moment, work, length of push cycle, and power during wheelchair propulsion over outdoor and indoor community conditions, and in laboratory conditions.

RESULTS

Upper-extremity asymmetry was present within each condition. There were no differences in the magnitude of asymmetry when comparing laboratory with indoor community conditions. Outdoor community wheelchair propulsion asymmetry was significantly greater than asymmetry measured during laboratory conditions.

CONCLUSIONS

Investigators should be aware that manual wheelchair propulsion is an asymmetrical act, which may influence interpretation when data is collected from a single limb or averaged for both limbs. The greater asymmetry identified during outdoor versus laboratory conditions emphasizes the need to evaluate wheelchair biomechanics in the user's natural environment.

The effect of resultant force at the pushrim on shoulder kinetics during manual wheelchair propulsion: a simulation study

The aim of this study was to determine, by simulation on real data, the effect of modifying the direction or effectiveness of a given force amplitude on the load sustained by the shoulder estimated by joint forces and moments. Kinematics and kinetics data were recorded on 14 manual wheelchair users 68.2+/-5.2 years for 10 s at sub-maximal speed (0.96-1.01 m/s). The simulation consisted in modifying force effectiveness at the pushrim while maintaining the same initial force amplitude. Shoulder kinetics were computed for simulated resultant forces from radial to tangent directions and also for initial force effectiveness. The results show that as the force was simulated tangent to the wheel, there was a significant increase in the average proximal and anterior shoulder joint forces. Also, significant increases in average internal rotation, flexion in the sagittal and horizontal plane moments were reported. Higher shoulder kinetics could accelerate the onset of fatigue and increase the risk of injury. A single-case analysis revealed an improvement window for force effectiveness ( approximately 10%) in which shoulder kinetics were not substantially increased. Our results provide useful information on what would happen to shoulder kinetics if we were able to teach manual wheelchair users to modify their force pattern at the pushrim. The results suggest that for an elderly population, it is not wise to aim at producing a mechanically optimal resultant force at the pushrim (i.e., tangent). Smaller increases of the initial force effectiveness would be preferable.