Differences in Glenohumeral Joint Contact Forces Between Recovery Hand Patterns During Wheelchair Propulsion With and Without Shoulder Muscle Weakness: A Simulation Study.

The majority of manual wheelchair users (MWCU) develop shoulder pain or injuries, which is often caused by impingement. Because propulsion mechanics are influenced by the recovery hand pattern used, the pattern may affect shoulder loading and susceptibility to injury. Shoulder muscle weakness is also correlated with shoulder pain, but how shoulder loading changes with specific muscle group weakness is unknown. Musculoskeletal modeling and simulation were used to compare glenohumeral joint contact forces (GJCFs) across hand patterns and determine how GJCFs vary when primary shoulder muscle groups are weakened. Experimental data were analyzed to classify individuals into four hand pattern groups. A representative musculoskeletal model was then developed for each group and simulations generated to portray baseline strength and six muscle weakness conditions. Three-dimensional GJCF peaks and impulses were compared across hand patterns and muscle weakness conditions. The semicircular pattern consistently had lower shear (anterior-posterior and superior-inferior) GJCFs compared to other patterns. The double-loop pattern had the highest superior GJCFs, while the single-loop pattern had the highest anterior and posterior GJCFs. These results suggest that using the semicircular pattern may be less susceptible to shoulder injuries such as subacromial impingement. Weakening the internal rotators and external rotators resulted in the greatest increases in shear GJCFs and decreases in compressive GJCF, likely due to decreased force from rotator cuff muscles. These findings suggest that strengthening specific muscle groups, especially the rotator cuff, is critical for decreasing the risk of shoulder overuse injuries.

Objective and Self-Reported Physical Activity Measures and Their Association With Depression and Satisfaction With Life in Persons With Spinal Cord Injury.

OBJECTIVE: To identify associations between objective and self-reported measures of physical activity (PA) and relationships with depression and satisfaction with life (SWL) in persons with spinal cord injury (SCI). DESIGN: Retrospective, cross-sectional study of objectively measured wheelchair propulsion (WCP) from 2 studies in which an odometer was attached to participants' wheelchairs to record daily speed and distance. Self-reported data were collected in a separate study examining dyspnea, PA, mood, and SWL. SETTING: Outpatient clinic in a rehabilitation center. PARTICIPANTS: Individuals (N=86) with traumatic SCI who use a manual wheelchair. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Objective measures of PA included average daily distance and speed of WCP measured by an odometer. Self-report questionnaires included demographics, the 24-hour recall of transfers, Physical Activity Recall Assessment for People with SCI, the Patient Health Questionnaire-2 (PHQ-2) to document depressive symptoms, and the Satisfaction With Life Scale (SWLS). RESULTS: Both objective measures of WCP, average daily distance and speed, were predicted by the combination of self-reported daily time away from home/yard and lower frequency of car transfers ([r=.367, P=.002] and [r=.434, P<.001], respectively). Daily distance of WCP was negatively correlated with depression (PHQ-2) (r=-.309, P=.004). Time in leisure PA was the only significant predictor of SWLS scores (r=.321, P=.003). CONCLUSIONS: Short-term recall of hours away from home/yard not spent driving or riding in a vehicle is suggested as a self-report measure that is moderately related to overall WCP PA in this population. Results of this study suggest that depression is related to decreased PA and WCP activity, while SWL is related to leisure PA.

Multi-Site Identification and Generalization of Clusters of Walking Behaviors in Individuals With Chronic Stroke and Neurotypical Controls.

BACKGROUND: Walking patterns in stroke survivors are highly heterogeneous, which poses a challenge in systematizing treatment prescriptions for walking rehabilitation interventions. OBJECTIVES: We used bilateral spatiotemporal and force data during walking to create a multi-site research sample to: (1) identify clusters of walking behaviors in people post-stroke and neurotypical controls and (2) determine the generalizability of these walking clusters across different research sites. We hypothesized that participants post-stroke will have different walking impairments resulting in different clusters of walking behaviors, which are also different from control participants. METHODS: We gathered data from 81 post-stroke participants across 4 research sites and collected data from 31 control participants. Using sparse K-means clustering, we identified walking clusters based on 17 spatiotemporal and force variables. We analyzed the biomechanical features within each cluster to characterize cluster-specific walking behaviors. We also assessed the generalizability of the clusters using a leave-one-out approach. RESULTS: We identified 4 stroke clusters: a fast and asymmetric cluster, a moderate speed and asymmetric cluster, a slow cluster with frontal plane force asymmetries, and a slow and symmetric cluster. We also identified a moderate speed and symmetric gait cluster composed of controls and participants post-stroke. The moderate speed and asymmetric stroke cluster did not generalize across sites. CONCLUSIONS: Although post-stroke walking patterns are heterogenous, these patterns can be systematically classified into distinct clusters based on spatiotemporal and force data. Future interventions could target the key features that characterize each cluster to increase the efficacy of interventions to improve mobility in people post-stroke.

Multi-site identification and generalization of clusters of walking behaviors in individuals with chronic stroke and neurotypical controls.

Background: Walking patterns in stroke survivors are highly heterogeneous, which poses a challenge in systematizing treatment prescriptions for walking rehabilitation interventions. Objective: We used bilateral spatiotemporal and force data during walking to create a multi-site research sample to: 1) identify clusters of walking behaviors in people post-stroke and neurotypical controls, and 2) determine the generalizability of these walking clusters across different research sites. We hypothesized that participants post-stroke will have different walking impairments resulting in different clusters of walking behaviors, which are also different from control participants. Methods: We gathered data from 81 post-stroke participants across four research sites and collected data from 31 control participants. Using sparse K-means clustering, we identified walking clusters based on 17 spatiotemporal and force variables. We analyzed the biomechanical features within each cluster to characterize cluster-specific walking behaviors. We also assessed the generalizability of the clusters using a leave-one-out approach. Results: We identified four stroke clusters: a fast and asymmetric cluster, a moderate speed and asymmetric cluster, a slow cluster with frontal plane force asymmetries, and a slow and symmetric cluster. We also identified a moderate speed and symmetric gait cluster composed of controls and participants post-stroke. The moderate speed and asymmetric stroke cluster did not generalize across sites. Conclusions: Although post-stroke walking patterns are heterogenous, these patterns can be systematically classified into distinct clusters based on spatiotemporal and force data. Future interventions could target the key features that characterize each cluster to increase the efficacy of interventions to improve mobility in people post-stroke.

Treatments perceived to be helpful for neuropathic pain after traumatic spinal cord injury: A multicenter cross-sectional survey study.

DESIGN: Cross-sectional survey. OBJECTIVE: To evaluate the perceived helpfulness of pharmacological and non-pharmacological interventions and their combinations for neuropathic pain (NeuP) and subcategories of NeuP after spinal cord injury (SCI). SETTING: Six Spinal Cord Injury Model System Centers. METHODS: Three hundred ninety one individuals at least one year post traumatic SCI were enrolled. A telephone survey was conducted to determine the pharmacologic and non-pharmacologic treatments used in the last 12 months for each participant's three worst pains, whether these treatments were "helpful", and if currently used, each treatments' effectiveness. RESULTS: Two hundred twenty participants (56%) reported 354 distinct NeuPs. Pharmacological treatments rated helpful for NeuP were non-tramadol opioids (opioids were helpful for 86% of opioid treated NeuPs), cannabinoids (83%), and anti-epileptics (79%). Non-pharmacological treatments rated helpful for NeuP were massage (76%), body position adjustment (74%), and relaxation therapy (70%). Those who used both opioids and exercise reported greater NeuP treatment helpfulness compared to participants using opioids without exercise (P = 0.03). CONCLUSIONS: Opioids, cannabinoids, and massage were reported more commonly as helpful than treatments recommended as first-line therapies by current clinical practice guidelines (CPGs) for NeuP after SCI (antiepileptics and antidepressants). Individuals with SCI likely value the modulating effects of pharmacological and non-pharmacological treatments on the affective components of pain in addition to the sensory components of pain when appraising treatment helpfulness.

Effects of reduction in shoulder pain on quality of life and community activities among people living long-term with SCI paraplegia: a randomized control trial.

OBJECTIVE/BACKGROUND: People with spinal cord injury (SCI) paraplegia can develop shoulder problems over time, which may also cause pain. Shoulder pain may complicate or interfere with a person's daily activities, social events, and their overall quality of life (QOL). The purpose of this study was to examine changes in social interaction and QOL after an exercise treatment for shoulder pain in people with SCI paraplegia. DESIGN: Fifty-eight participants with SCI paraplegia who were also experiencing shoulder pain were selected and randomized to either an exercise treatment or a control group. Participants in the treatment group participated in a 12-week, at-home, exercise and movement optimization program designed to strengthen shoulder muscles and modify movements related to upper extremity weight bearing. METHODS: Participants filled out self-report measures at baseline, 12 weeks later at the end of treatment, and at a 4-week follow-up. OUTCOME MEASURES: The Wheelchair User's Shoulder Pain Index (WUSPI), the Social Interaction Inventory (SII), and the Subjective Quality of Life Scale. RESULTS: From the baseline to the end of treatment, repeated-measures analysis of variance revealed a significant interaction between WUSPI and SII scores, P < 0.001, and between WUSPI and QOL scores, P < 0.001. CONCLUSION: Reductions in shoulder pain were related to significant increases in social participation and improvements in QOL. However, increases in social participation did not significantly affect improvements in QOL.

The relationship between the hand pattern used during fast wheelchair propulsion and shoulder pain development.

Up to 84% of manual wheelchair users (MWCU) with spinal cord injury experience shoulder pain, which is correlated with shoulder adductor weakness in this population. Modeling studies have shown weak shoulder adductors lead to compensations from the deltoid and rotator cuff muscles during propulsion, which may lead to altered propulsion mechanics. However, the role recovery phase hand pattern has in pain development is unclear, as each hand pattern is associated with unique mechanics and different levels of muscle demand. Previous research found no correlation between hand pattern and shoulder pain at self-selected speeds. However, fast propulsion may exacerbate poor mechanics caused by shoulder muscle weakness, which may reveal those at risk for pain development. The present study evaluated whether the hand pattern used during fast wheelchair propulsion is correlated with shoulder pain. We also assessed whether shoulder adductor strength was correlated with hand pattern. Fast propulsion data from two subsets of MWCU were analyzed at three time points (baseline, 18 months, 36 months). All participants were pain-free at baseline. Subset 1 compared individuals who remained pain-free to those who developed shoulder pain. Subset 2 compared individuals with chronic pain at follow-up to those whose pain resolved over time. The hand pattern used was not different between groups in either subset. However, more over-rim patterns were correlated with lower adductor strength in Subset 1. These results suggest that although the hand pattern used during fast propulsion is not correlated with shoulder pain, more over-rim hand patterns may indicate weaker shoulder adductors.

Using Biofeedback to Reduce Step Length Asymmetry Impairs Dynamic Balance in People Poststroke.

BACKGROUND: People poststroke often walk with a spatiotemporally asymmetric gait, due in part to sensorimotor impairments in the paretic lower extremity. Although reducing asymmetry is a common objective of rehabilitation, the effects of improving symmetry on balance are yet to be determined. OBJECTIVE: We established the concurrent validity of whole-body angular momentum as a measure of balance, and we determined if reducing step length asymmetry would improve balance by decreasing whole-body angular momentum. METHODS: We performed clinical balance assessments and measured whole-body angular momentum during walking using a full-body marker set in a sample of 36 people with chronic stroke. We then used a biofeedback-based approach to modify step length asymmetry in a subset of 15 of these individuals who had marked asymmetry and we measured the resulting changes in whole-body angular momentum. RESULTS: When participants walked without biofeedback, whole-body angular momentum in the sagittal and frontal plane was negatively correlated with scores on the Berg Balance Scale and Functional Gait Assessment supporting the validity of whole-body angular momentum as an objective measure of dynamic balance. We also observed that when participants walked more symmetrically, their whole-body angular momentum in the sagittal plane increased rather than decreased. CONCLUSIONS: Voluntary reductions of step length asymmetry in people poststroke resulted in reduced measures of dynamic balance. This is consistent with the idea that after stroke, individuals might have an implicit preference not to deviate from their natural asymmetry while walking because it could compromise their balance. Clinical Trials Number: NCT03916562.

Shoulder Pain Prevention Program for Manual Wheelchair Users With Paraplegia: A Randomized Clinical Trial.

Objectives: To compare prevalence of shoulder pain (SP) onset over 3 years for individuals with paraplegia from spinal cord injury who participate in one of two shoulder pain prevention program (SPPP) formats with that of a similar population without intervention, and to compare exercise adherence between two SPPP formats. Methods: The randomized clinical trial (compared to historical controls) included a volunteer sample of 100 individuals without SP at study entry. Eighty-seven participants returned for assessments at 18 and 36 months after study entry. Control group included 220 volunteers from a 3-year observational study with identical inclusion criteria. SPPPs included shoulder home exercises and recommendations to improve mobility techniques that are effective in reducing existing SP in this population. Participants were randomly assigned to receive either one instruction session and a refresher session 4 weeks later with a physical therapist or a 4-week series of 2-hour group classes taught by a physical therapist and peer mentor. Prevalence of SP onset at 18 and 36 months and self-reported average weekly exercise frequency were the main outcome measures. Results: SP onset was identical in the two SPPPs but was significantly lower at 18 and 36 months in both groups (11% and 24%) compared to controls (27% and 40%, p < .05). Self-reported average weekly exercise frequency was similar between intervention groups but was significantly lower during the first 4 months in participants who developed SP compared to those without pain (2.12 ± 1.0 vs. 3.01 ± 1.13, p < .05). Conclusion: SPPPs reduced SP onset prevalence regardless of instruction format. Exercise adherence was important to the outcome of shoulder pain.

A Primary Care Provider's Guide to Shoulder Pain After Spinal Cord Injury.

Shoulder pain is a common occurrence after spinal cord injury (SCI) and can have significant negative effects on health and function as many individuals with SCI are reliant on their upper extremities for mobility and self-care activities. Shoulder pain after SCI can be caused by acute injury or chronic pathology, but it is most often related to overuse injuries of the rotator cuff. Both acute strain and chronic overuse shoulder injuries in persons with SCI typically result from increased weight bearing on the upper extremities during transfers, weight-relief raises, and wheelchair propulsion, which are often performed in poor postural alignment owing to strength deficits. This article discusses management of patients with SCI who present with shoulder pain from the perspective of primary care physicians including evaluation and diagnostic procedures, interventions appropriate for both acute and chronic shoulder pain, and strategies for prevention.

Effect of reverse manual wheelchair propulsion on shoulder kinematics, kinetics and muscular activity in persons with paraplegia.

Objective: Shoulder pain after spinal cord injury (SCI) is attributed to increased mobility demands on the arms and negatively impacts independence and quality of life. Repetitive superior and posterior shoulder joint forces produced during traditional wheelchair (WC) locomotion can result in subacromial impingement if unopposed, as with muscular fatigue or weakness. ROWHEELS® (RW), geared rear wheels that produce forward WC movement with backward rim pulling, could alter these forces. Design: Cross sectional. Setting: Research laboratory at a rehabilitation hospital. Participants: Ten manual WC users with paraplegia. Outcome measures: Propulsion characteristics and right upper extremity/trunk kinematics and shoulder muscle activity were collected during ergometer propulsion: (1) self-selected free speed reverse propulsion with RW, (2) matched-speed reverse (rSW), and (3) forward propulsion (fSW) with instrumented Smartwheels (SW). Inverse dynamics using right-side SW rim kinetics and kinematics compared shoulder kinetics during rSW and fSW. Results: Free propulsion velocity, cycle distance and cadence were similar during RW, rSW and fSW. Overall shoulder motion was similar except that peak shoulder extension was significantly reduced in both RW and rSW versus fSW. Anteriorly and inferiorly directed SW rim forces were decreased during rSW versus fSW propulsion, but posteriorly and superiorly directed rim forces were significantly greater. Superior and posterior shoulder joint forces and flexor, adductor, and external rotation moments were significantly less during rSW, without a significant difference in net shoulder forces and moments. Traditional propulsive-phase muscle activity was significantly reduced and recovery-phase muscle activity was increased during reverse propulsion. Conclusion: These results suggest that reverse propulsion may redirect shoulder demands and prevent subacromial impingement, thereby preventing injury and preserving independent mobility for individuals with paraplegia.

Comparison of shoulder muscle electromyographic activity during standard manual wheelchair and push-rim activated power assisted wheelchair propulsion in persons with complete tetraplegia.

OBJECTIVES: To compare spatio-temporal propulsion characteristics and shoulder muscle electromyographic activity in persons with cervical spinal cord injury propelling a standard pushrim wheelchair (WC) and a commercially available pushrim-activated power assisted wheelchair (PAPAW) design on a stationary ergometer. DESIGN: Repeated measures. SETTING: Motion analysis laboratory within a rehabilitation hospital. PARTICIPANTS: Men (N=14) with complete (American Spinal Injury Association grade A or B) tetraplegia (C6=5; C7=9). INTERVENTION: Participants propelled a standard pushrim WC and PAPAW during 3 propulsion conditions: self-selected free and fast and simulated 4% or 8% graded resistance propulsion. MAIN OUTCOME MEASURES: Median speed, cycle length, cadence, median and peak electromyographic activity intensity, and duration of electromyographic activity in pectoralis major, anterior deltoid, supraspinatus, and infraspinatus muscles were compared between standard pushrim WC and PAPAW propulsion. RESULTS: A significant (P<.05) decrease in electromyographic activity intensity and duration of pectoralis major, anterior deltoid, and infraspinatus muscles and significantly reduced intensity and push phase duration of supraspinatus electromyographic activity at faster speeds and with increased resistance were seen during PAPAW propulsion. CONCLUSIONS: For participants with complete tetraplegia, push phase shoulder muscle activity was decreased in the PAPAW compared with standard pushrim WC, indicating a reduction in demands when propelling a PAPAW.

Predictors of shoulder pain in manual wheelchair users.

BACKGROUND: Manual wheelchair users rely on their upper limbs to provide independent mobility, which leads to high muscular demand on their upper extremities and often results in shoulder pain and injury. However, the specific causes of shoulder pain are unknown. Previous work has shown that decreased shoulder muscle strength is predictive of shoulder pain onset, and others have analyzed joint kinematics and kinetics, propulsion technique and intra-individual variability for their relation to shoulder pathology. The purpose of this study was to determine in a longitudinal setting whether there are specific biomechanical measures that predict shoulder pain development in manual wheelchair users. METHODS: All participants were asymptomatic for shoulder pain and categorized into pain and no pain groups based on assessments at 18 and 36 months later. Shoulder strength, handrim and joint kinetics, kinematics, spatiotemporal measures, intra-individual standard deviations and coefficients of variation were evaluated as predictors of shoulder pain. FINDINGS: Individuals who developed shoulder pain had weaker shoulder adductor muscles, higher positive shoulder joint work during recovery, and less trunk flexion than those who did not develop pain. In addition, relative intra-individual variability was a better predictor of shoulder pain than absolute variability, however future work is needed to determine when increased versus decreased variability is more favorable for preventing shoulder pain. INTERPRETATION: These predictors may provide insight into how to improve rehabilitation training and outcomes for manual wheelchair users and ultimately decrease their likelihood of developing shoulder pain and injuries.

Muscle compensatory mechanisms during able-bodied toe walking.

The purpose of this study was to use muscle-actuated forward dynamic simulations to quantify individual muscle contributions to body support (vertical ground reaction force) and propulsion (horizontal ground reaction force) and the mechanical energetics of the body segments during toe and heel-toe walking performed by able-bodied subjects to identify possible compensatory mechanisms necessary to toe walk. The simulations showed that an increased magnitude of plantar flexor power output in early stance, which was necessary to maintain the equinus posture during toe walking, contributed to body support and acted to brake (decelerate) the center-of-mass in the horizontal direction. This in turn required a reduction in the contributions to support from the vastii, gluteus maximus and biarticular hamstring muscles and decreased contributions to braking from the vastii and to a lesser extent the gluteus maximus. In late stance, the soleus contributed less to body support and forward propulsion during toe walking, which when combined with the increased braking by the plantar flexors in early stance, required a prolonged contribution to forward propulsion from the hamstrings from mid- to late stance. The multiple compensatory mechanisms necessary to toe walk have important implications for distinguishing between underlying pathology and necessary compensatory mechanisms, as well as for identifying the most appropriate treatment strategy for equinus gait.

Shoulder muscular demand during lever-activated vs pushrim wheelchair propulsion in persons with spinal cord injury.

BACKGROUND/OBJECTIVE: The high demand on the upper limbs during manual wheelchair (WC) use contributes to a high prevalence of shoulder pathology in people with spinal cord injury (SCI). Lever-activated (LEVER) WCs have been presented as a less demanding alternative mode of manual WC propulsion. The objective of this study was to evaluate the shoulder muscle electromyographic activity and propulsion characteristics in manual WC users with SCI propelling a standard pushrim (ST) and LEVER WC design. METHODS: Twenty men with complete injuries (ASIA A or B) and tetraplegia (C6, n = 5; C7, n = 7) or paraplegia (n = 8) secondary to SCI propelled ST and LEVER WCs at 3 propulsion conditions on a stationary ergometer: self-selected free, self-selected fast, and simulated graded resistance. Average velocity, cycle distance, and cadence; median and peak electromyographic intensity; and duration of electromyography of anterior deltoid, pectoralis major, supraspinatus, and infraspinatus muscles were compared between LEVER and ST WC propulsion. RESULTS: Significant decreases in pectoralis major and supraspinatus activity were recorded during LEVER compared with ST WC propulsion. However, anterior deltoid and infraspinatus intensities tended to increase during LEVER WC propulsion. Participants with tetraplegia had similar or greater anterior deltoid, pectoralis major, and infraspinatus activity for both ST and LEVER WC propulsion compared with the men with paraplegia. CONCLUSIONS: Use of the LEVER WC reduced and shifted the shoulder muscular demands in individuals with paraplegia and tetraplegia. Further studies are needed to determine the impact of LEVER WC propulsion on long-term shoulder function.

The neuromuscular demands of toe walking: a forward dynamics simulation analysis.

Toe walking is a gait deviation with multiple etiologies and often associated with premature and prolonged ankle plantar flexor electromyographic activity. The goal of this study was to use a detailed musculoskeletal model and forward dynamical simulations that emulate able-bodied toe and heel-toe walking to understand why, despite an increase in muscle activity in the ankle plantar flexors during toe walking, the internal ankle joint moment decreases relative to heel-toe walking. The simulations were analyzed to assess the force generating capacity of the plantar flexors by examining each muscle's contractile state (i.e., the muscle fiber length, velocity and activation). Consistent with experimental measurements, the simulation data showed that despite a 122% increase in soleus muscle activity and a 76% increase in gastrocnemius activity, the peak internal ankle moment in late stance decreased. The decrease was attributed to non-optimal contractile conditions for the plantar flexors (primarily the force-length relationship) that reduced their ability to generate force. As a result, greater muscle activity is needed during toe walking to produce a given muscle force level. In addition, toe walking requires greater sustained plantar flexor force and moment generation during stance. Thus, even though toe walking requires lower peak plantar flexor forces that might suggest a compensatory advantage for those with plantar flexor weakness, greater neuromuscular demand is placed on those muscles. Therefore, medical decisions concerning whether to reduce equinus should consider not only the impact on the ankle moment, but also the expected change to the plantar flexor's force generating capacity.

The relationship of shoulder pain intensity to quality of life, physical activity, and community participation in persons with paraplegia.

BACKGROUND/OBJECTIVE: For persons with spinal cord injury (SCI), severe bodily pain is related to a lower quality of life. However, the effect of pain from a specific body region on quality of life has yet to be determined. The shoulder joint is a common site of pain among persons with SCI. Therefore, our purpose was to identify the relationship of self-reported shoulder pain with quality of life, physical activity, and community activities in persons with paraplegia resulting from SCI. METHODS: Eighty participants with shoulder pain who propel a manual wheelchair (mean age: 44.7 years; mean duration of injury: 20 years; injury level T1-L2) completed the following questionnaires: Wheelchair User's Shoulder Pain Index, Subjective Quality of Life Scale, Physical Activity Scale for Individuals with Physical Disabilities, and Community Activities Checklist. Correlations between shoulder pain scores and quality of life, physical activity, and community activities were determined using Spearman's rho test. RESULTS: Shoulder pain intensity was inversely related to subjective quality of life (r(s) =-0.35; P= 0.002) and physical activity (r(s) = -0.42; P < 0.001). Shoulder pain intensity was not related to involvement in community activities (r(s) = -0.07; P = 0.526). CONCLUSIONS: Persons with SCI who reported lower subjective quality of life and physical activity scores experienced significantly higher levels of shoulder pain. However, shoulder pain intensity did not relate to involvement in general community activities. Attention to and interventions for shoulder pain in persons with SCI may improve their overall quality of life and physical activity.

Telehealth monitor to measure physical activity and pressure relief maneuver performance in wheelchair users.

This study demonstrated the feasibility of a device for monitoring pressure relief maneuvers and physical activity for wheelchair users. The device counts the number of wheel pushes based on wheelchair acceleration and measures pressure relief maneuvers using a seat sensor consisting of three force sensing resistors (FSRs). To establish the feasibility of the seat sensor for the detection of pressure relief maneuvers, 10 wheelchair users and 10 non-disabled controls completed a series of wheelchair depression raises, forward trunk leans, and lateral trunk leans. The seat sensor was placed underneath the user's seat cushion. To establish the feasibility of wheel push counting, 10 full-time wheelchair users navigated a flat 50-m outdoor track and a 100-m outdoor obstacle course during self-propulsion (e.g., wheel pushes) and during assisted-propulsion (e.g., no wheel pushes). Of the 240 performed pressure relief, 225 were properly classified by the seat sensor (accuracy: 94%, sensitivity: 96%, specificity: 80%). Sensitivity was highest for depression raises (98%) and lowest for front lean maneuvers (80%). The wheelchair activity monitor measured 2,112 pushes during the self-propulsion trials compared to 2,162 pushes measured with the instrumented push-rim (97.7%). During assisted-propulsion trials, there were 477 incorrectly identified pushes (8.0 per trial).

The influence of wheelchair propulsion hand pattern on upper extremity muscle power and stress.

The hand pattern (i.e., full-cycle hand path) used during manual wheelchair propulsion is frequently classified as one of four distinct hand pattern types: arc, single loop, double loop or semicircular. Current clinical guidelines recommend the use of the semicircular pattern, which is based on advantageous levels of broad biomechanical metrics implicitly related to the demand placed on the upper extremity (e.g., lower cadence). However, an understanding of the influence of hand pattern on specific measures of upper extremity muscle demand (e.g., muscle power and stress) is needed to help make such recommendations, but these quantities are difficult and impractical to measure experimentally. The purpose of this study was to use musculoskeletal modeling and forward dynamics simulations to investigate the influence of the hand pattern used on specific measures of upper extremity muscle demand. The simulation results suggest that the double loop and semicircular patterns produce the most favorable levels of overall muscle stress and total muscle power. The double loop pattern had the lowest full-cycle and recovery-phase upper extremity demand but required high levels of muscle power during the relatively short contact phase. The semicircular pattern had the second-lowest full-cycle levels of overall muscle stress and total muscle power, and demand was more evenly distributed between the contact and recovery phases. These results suggest that in order to decrease upper extremity demand, manual wheelchair users should consider using either the double loop or semicircular pattern when propelling their wheelchairs at a self-selected speed on level ground.