Dany Gagnon

Comparison of peak shoulder and elbow mechanical loads during weight-relief lifts and sitting pivot transfers among manual wheelchair users with spinal cord injury.

This study compared shoulder and elbow joint forces and moments between weight-relief lifts (WRLs) and sitting pivot transfers (SPTs) among manual wheelchair users with spinal cord injury (SCI) (N = 13) during biomechanical laboratory assessment. Minimum and maximum values were reported for each triaxial component of the joint force at the dominant shoulder and elbow during SPTs (leading and trailing roles) and WRLs. Peak shoulder flexor and adductor moments, along with elbow flexor and extensor moments, observed during the same period were also analyzed. The SPTs predominantly exposed (p < 0.001) the shoulder joints to substantial posteriorly directed forces (leading = -2.6 N/kg; trailing = -3.1 N/kg) compared with WRLs (-2.2 N/kg), whereas superiorly directed forces (2.9 N/kg) were principally sustained ( p < 0.001) during WRLs compared with SPTs (leading = 1.5 N/kg; trailing = 1.5 N/kg). High superiorly directed forces (3.6 to 3.9 N/kg) were observed at the elbow, which were comparable (p = 0.33) between the two tasks. The peak shoulder flexor (leading = 1.36 N m/kg; trailing = 1.45 N m/kg) and adductor moments (leading only = -0.46 N m/kg), along with the peak elbow flexor moments (leading = 0.24 N m/kg; trailing = 0.15 N m/kg), were significantly more elevated (p < 0.021) during SPTs than during WRLs. Peak shoulder adductor (-0.46 vs -0.24 N m/kg) and elbow flexor moments were also more elevated ( p = 0.03) at the leading upper limb compared with the trailing one. The peak elbow extensor moments did not differ ( p = 0.167) between the two tasks (-0.17 to -0.25 N m/kg). SPTs exposed the shoulder and elbow joints to greater mechanical loads than WRLs among individuals with SCI.

Quantification of reaction forces during sitting pivot transfers performed by individuals with spinal cord injury.

OBJECTIVES To quantify the reaction forces exerted under the hands, feet and buttocks when individuals with spinal cord injury performed sitting pivot transfers. DESIGN Twelve men with paraplegia completed 3 transfers between seats of the same height (0.5 m high) and 3 transfers to a high target seat (0.6 m high). RESULTS Greater mean and peak vertical reaction forces were always recorded under the hands compared with the feet (p<0.001) during the transfers. Mean vertical reaction forces were similar between the leading and trailing hands (p>0.088) for the 2 transfers studied. However, the mean vertical reaction force underneath the leading hand was greater when transferring between a seat of the same height compared with one of a higher height (p=0.021) and vice-versa for the trailing hand (p=0.0001). The peak vertical reaction force always occurred earlier (p<0.0001) and was greater underneath the trailing hand compared with the leading one (p<0.02), and reached its highest value when transferring to the high target seat (p=0.003). Peak and mean horizontal reaction forces were always higher underneath the trailing hand compared with the leading hand (p<0.001). CONCLUSION These results provide evidence-based data to better understand transfers and strengthen clinical practice guidelines targeting the preservation of upper extremity integrity.

Repeatability of ultrasonographic median nerve measures

In this study we investigated the reliability of ultrasound in measuring median nerve characteristics including cross‐sectional area (CSA), flattening ratio (FR), swelling ratio (SR), and mean grayscale. Generalizability theory was used to assess inter‐ and intrarater reliability using the dependability coefficient (ϕ), normalized standard error of measurement, and normalized minimum detectable change (MDCNORM) for multiple study design protocols. Interrater reliability was generally moderate. Intrarater reliability was mostly good (ϕ > 0.876) when using a single image, captured on one occasion, and being read once. Intrarater MDCNORM ranged from 3.8% to 6.2% for all CSA measures and SR. Using multiple images and/or readings at multiple occasions did not appreciably improve reliability measures. Ultrasound is a reliable tool for measuring median nerve characteristics. We recommend that a single evaluator capture all images for protocols aimed at quantifying median nerve ultrasound measures. We believe an appropriately designed protocol can utilize ultrasound to accurately assess changes in median nerve characteristics after activity. Muscle Nerve, 2010

Biomechanical analysis of a posterior transfer maneuver on a level surface in individuals with high and low-level spinal cord injuries

OBJECTIVE The purpose of this study was to determine the movement patterns and the muscular demand during a posterior transfer maneuver on a level surface in individuals with spinal cord injuries. DESIGN Six participants with high-level spinal cord injury (C7 to T6) were compared to five participants with low-level spinal cord injury (T11 to L2) with partial or complete control of abdominal musculature. BACKGROUND Developing an optimal level of independence for transfer activities figures among the rehabilitation goals of individuals with spinal cord injury. There has been no biomechanical study which specifically describes the posterior transfer maneuver. METHODS Tridimensional kinematics at the elbow, shoulder, head and trunk, as well as surface electromyographic data of the biceps, triceps, anterior deltoid, posterior deltoid, pectoralis major, latissimus dorsi, trapezius and rectus abdominus muscles were recorded during the posterior transfer. To quantify the muscular demand, the electromyographic data were amplitude normalized to the peak value obtained from maximum voluntary contractions. The transfer was divided into pre-lift, lift, and post-lift phases for analysis. RESULTS The duration of the lift phase was significantly shorter (P<0.05) for the high-level spinal cord injury (1.24; SD, 0.37 s) when compared to the low-level spinal cord injury (1.74; SD, 0.39 s). The patterns and magnitudes of the angular displacements were found similar between groups (P values: 0.45-0.98). However, the high-level spinal cord injury initiated the task from a forward flexed posture, whereas the low-level spinal cord injury adopted an almost upright alignment of the trunk. Higher muscular demands were calculated for all muscles among high-level spinal cord injury participants during the transfer when compared to the low-level spinal cord injury. However, only the anterior deltoid (high level=92.4%; low level=34.2%) and the pectoralis major (high level=109.8%; low level=25.6%) reached statistical significance during the lift phase.Conclusions. Participants with high-level spinal cord injury presented different movement characteristics and higher muscular demands during the posterior transfer than low-level spinal cord injury ones. This is probably to compensate for the additional trunk and upper limb musculature impairment. RELEVANCE The findings of this study may help to develop guidelines of specific strengthening programs for the thoracohumeral, scapulothoracic and shoulder muscles designed to restore optimal transfer capacity in individuals with spinal cord injury. Furthermore, innovative rehabilitation programs targeting the ability to control the trunk could be beneficial for these individuals.

Movement patterns and muscular demands during posterior transfers toward an elevated surface in individuals with spinal cord injury

Study design:Three-dimensional kinematic analysis and surface electromyography (EMG) of 10 male adults with complete spinal cord injury (C7 to L2).Objective:To examine movement patterns and muscular demands in individuals with spinal cord injury (SCI) during posterior transfers.Setting:Pathokinesiology Laboratory at a Rehabilitation Centre, Montreal, Canada.Methods:Kinematic variables that described the positions and angular displacements of the head, trunk, shoulder and elbow were obtained by videotaping markers placed on the subject segments. EMG data were recorded for the biceps, triceps, anterior deltoid, pectoralis major, latissimus dorsi and trapezius muscles of the dominant upper extremity during posterior transfers using surface electrodes. To quantify the muscular demand, the EMG data recorded during the transfers were normalized to values obtained during maximal static contractions (EMGmax). The mean muscular demand was calculated for every muscle during the lift phase of the transfers. The lift phase was determined by pressure-sensitive contacts.Results:All subjects were able to execute the posterior transfers on an even surface, whereas nine subjects completed at least one of the transfers to the elevated surface. A forward-flexion pattern at the head and trunk was observed when either one or two hands remained on the lower surface, whereas a lift strategy was seen when both hands were placed on the elevated surface. Transferring to the elevated surface with hands on the lower surface required inferior electromyographic muscular utilization ratio (EMUR) than the transfer on the even surface for all muscles. The lowest EMUR were calculated for the transfer to the elevated surface with hands on the lower surface (triceps (18%), pectoralis major (53.8%), trapezius (66%) and latissimus dorsi (24.5%)) while performing the same transfer with hands on the elevated surface generated the highest EMUR (triceps (40.2%), anterior deltoid (73.2%), trapezius (83.6%) and latissimus dorsi (55.3%)).Conclusions:Subjects presented different movement characteristics and muscular demands during the posterior transfers. It is suggested that the forward-flexion pattern improves the dynamic trunk stability and reduces the muscular demand required to transfer. High muscular demand developed when hands were positioned on the elevated surface might be due to increased postural control demands on the upper limb and reduced angular momentum.

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

Abstract 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.

Biomechanical assessment of sitting pivot transfer tasks using a newly developed instrumented transfer system among long-term wheelchair users

This paper describes the technical characteristics of a transfer assessment system, along with details on three-dimensional (3D) upper extremity (U/E) kinematics required to compute U/E joint forces and moments using inverse dynamics during a displacement of the body in a sitting position from an initial surface to a target one (sitting pivot transfer (SPT)). This system includes five instrumented surfaces designed to measure position (center of pressure (COP)), magnitude and direction of the tri-axial force components underneath the feet, hands (leading and trailing) and buttocks (initial and target seats) during SPTs. Linearity, COP position and natural frequency tests were performed to confirm the accuracy of the transfer assessment system outcomes. Preliminary data of one person with spinal cord injury performing SPTs toward a target seat of same height (50 cm) and additional ones toward a raised target seat (60 cm) are presented. The transfer assessment system was found to be safe, versatile in terms of height- and width-adjustment ranges, portable within a laboratory environment, easy for experienced rehabilitation scientists to use, and allowed for valid quantification of reaction forces during SPTs as confirmed by the overall accuracy test results. Combined with the 3D U/E kinematic and anthropometric parameters, the transfer assessment system outcomes allowed for the quantification of U/E joint forces and moments. Preliminary results highlight the kinematic and kinetic specificities of the leading and trailing shoulders and elbows during SPTs. The impact of modifying target seat heights on the kinematic and kinetic outcomes during SPTs is explored. The transfer assessment framework proposed is useful for research and offers a wide spectrum of possibilities for acquiring new biomechanical knowledge on SPTs that may strengthen clinical practice guidelines, targeting the preservation of U/E integrity following SCI.

Electromyographic patterns of upper extremity muscles during sitting pivot transfers performed by individuals with spinal cord injury

Although substantial upper extremity (U/E) muscular efforts are required when individuals with spinal cord injury (SCI) perform sitting pivot transfers, little is known about the electromyographic (EMG) activation patterns of key shoulder and elbow muscles solicited during the performance of this functional task. The aims of this study were to examine the EMG activation patterns of U/E muscles in 10 males with SCI, and to compare them across sitting pivot transfers performed toward seats of different heights (low, same, high). EMG data from the biceps, triceps, deltoid, pectoralis major and latissimus dorsi were recorded bilaterally. Transfers were divided into pre-lift, lift, and post-lift phases. Each phase was time- and amplitude-normalized using a mean dynamic EMG approach. Similar EMG activation patterns were found across the different transfers for all muscles (r(mean)=0.942-0.991), whereas moderate to high inter-subject variability (CV: 20.9-70.6%) was reported for the different muscles and transfers. Peak EMG occurred earlier at the trailing U/E compared to the leading one, and was observed around seat-off for most of the muscles. When transfer to a high target seat was compared to transfer to one of the same height, significantly higher relative EMG values were observed at the biceps (mean: 1.64 vs. 1.00) of the leading U/E as well as the deltoid (mean: 1.20 vs. 1.00) and pectoralis major (mean: 1.20 vs. 1.00; peak: 2.27 vs. 1.79) of the trailing U/E. Transferring to a low target seat did not lead to lower muscular demand than transferring to one of the same height (P>0.05). These results indicate that coordinated and higher muscular efforts were generated at the trailing deltoid and pectoralis major when transferring to a high target seat compared to one of similar height. Higher muscular efforts were also developed at the leading biceps when transferring to a high target seat compared to a leveled one. Lowering the target seat with respect to the initial seat had no favorable effect on muscular demand.

Dynamic stability requirements during gait and standing exergames on the wii fit® system in the elderly

BackgroundIn rehabilitation, training intensity is usually adapted to optimize the trained system to attain better performance (overload principle). However, in balance rehabilitation, the level of intensity required during training exercises to optimize improvement in balance has rarely been studied, probably due to the difficulty in quantifying the stability level during these exercises. The goal of the present study was to test whether the stabilizing/destabilizing forces model could be used to analyze how stability is challenged during several exergames, that are more and more used in balance rehabilitation, and a dynamic functional task, such as gait.MethodsSeven healthy older adults were evaluated with three-dimensional motion analysis during gait at natural and fast speed, and during three balance exergames (50/50 Challenge, Ski Slalom and Soccer). Mean and extreme values for stabilizing force, destabilizing force and the ratio of the two forces (stability index) were computed from kinematic and kinetic data to determine the mean and least level of dynamic, postural and overall balance stability, respectively.ResultsMean postural stability was lower (lower mean destabilizing force) during the 50/50 Challenge game than during all the other tasks, but peak postural instability moments were less challenging during this game than during any of the other tasks, as shown by the minimum destabilizing force values. Dynamic stability was progressively more challenged (higher mean and maximum stabilizing force) from the 50/50 Challenge to the Soccer and Slalom games, to the natural gait speed task and to the fast gait speed task, increasing the overall stability difficulty (mean and minimum stability index) in the same manner.ConclusionsThe stabilizing/destabilizing forces model can be used to rate the level of balance requirements during different tasks such as gait or exergames. The results of our study showed that postural stability did not differ much between the evaluated tasks (except for the 50/50 Challenge), compared to dynamic stability, which was significantly less challenged during the games than during the functional tasks. Games with greater centre of mass displacements and changes in the base of support are likely to stimulate balance control enough to see improvements in balance during dynamic functional tasks, and could be tested in pathological populations with the approach used here.

Minimizing Errors in Acute Traumatic Spinal Cord Injury Trials by Acknowledging the Heterogeneity of Spinal Cord Anatomy and Injury Severity: An Observational Canadian Cohort Analysis

Clinical trials of therapies for acute traumatic spinal cord injury (tSCI) have failed to convincingly demonstrate efficacy in improving neurologic function. Failing to acknowledge the heterogeneity of these injuries and under-appreciating the impact of the most important baseline prognostic variables likely contributes to this translational failure. Our hypothesis was that neurological level and severity of initial injury (measured by the American Spinal Injury Association Impairment Scale [AIS]) act jointly and are the major determinants of motor recovery. Our objective was to quantify the influence of these variables when considered together on early motor score recovery following acute tSCI. Eight hundred thirty-six participants from the Rick Hansen Spinal Cord Injury Registry were analyzed for motor score improvement from baseline to follow-up. In AIS A, B, and C patients, cervical and thoracic injuries displayed significantly different motor score recovery. AIS A patients with thoracic (T2-T10) and thoracolumbar (T11-L2) injuries had significantly different motor improvement. High (C1-C4) and low (C5-T1) cervical injuries demonstrated differences in upper extremity motor recovery in AIS B, C, and D. A hypothetical clinical trial example demonstrated the benefits of stratifying on neurological level and severity of injury. Clinically meaningful motor score recovery is predictably related to the neurological level of injury and the severity of the baseline neurological impairment. Stratifying clinical trial cohorts using a joint distribution of these two variables will enhance a studys chance of identifying a true treatment effect and minimize the risk of misattributed treatment effects. Clinical studies should stratify participants based on these factors and record the number of participants and their mean baseline motor scores for each category of this joint distribution as part of the reporting of participant characteristics. Improved clinical trial design is a high priority as new therapies and interventions for tSCI emerge.