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Previous findings indicate that co-contractions of plantarflexors and dorsiflexors during quiet standing increase the ankle mechanical joint stiffness, resulting in increased postural sway. Balance impairments in individuals with incomplete spinal cord injury (iSCI) may be due to co-contractions like in other individuals with reduced balance ability. Here we investigated the effect of co-contraction between plantar- and dorsiflexors on postural balance in individuals with iSCI (iSCI-group) and able-bodied individuals (AB-group). Thirteen able-bodied individuals and 13 individuals with iSCI were asked to perform quiet standing with their eyes open (EO) and eyes closed (EC). Kinetics and electromyograms from the tibialis anterior (TA), soleus and medial gastrocnemius were collected bilaterally. The iSCI-group exhibited more co-contractions than the AB-group (EO: 0.208% vs. 75.163%, p = 0.004; EC: 1.767% vs. 92.373%, p = 0.016). Furthermore, postural sway was larger during co-contractions than during no co-contraction in the iSCI-group (EO: 1.405 cm/s2 vs. 0.867 cm/s2, p = 0.023; EC: 1.831 cm/s2 vs. 1.179 cm/s2, p = 0.030), but no differences were found for the AB-group (EO: 0.393 cm/s2 vs. 0.499 cm/s2, p = 1.00; EC: 0.686 cm/s2 vs. 0.654 cm/s2, p = 1.00). To investigate the mechanism, we performed a computational simulation study using an inverted pendulum model and linear controllers. An increase of mechanical stiffness in the simulated iSCI-group resulted in increased postural sway (EO: 2.520 cm/s2 vs. 1.174 cm/s2, p 2 vs. 1.836 cm/s2, p 2 vs. 0.658 cm/s2, p = 1.00; EC: 0.943 cm/s2 vs. 0.926 cm/s2, p = 0.190). Thus, we demonstrated that co-contractions may be a compensatory strategy for individuals with iSCI to accommodate for decreased motor function, but co-contractions may result in increased ankle mechanical joint stiffness and consequently postural sway.

BackgroundClinical applications of conventional functional electrical stimulation (FES) administered via a single electrode is limited by rapid onset neuromuscular fatigue. “Sequential” (SEQ) stimulation, involving rotation of pulses between multiple active electrodes, has been shown to reduce fatigue compared to conventional FES. However, there has been limited adoption of SEQ in research and clinical settings.MethodsThe SEQ adapter is a small, battery-powered device that transforms the output of any commercially available electrical stimulator into SEQ stimulation. We examined the output of the adaptor across a range of clinically relevant stimulation pulse parameters to verify the signal integrity preservation ability of the SEQ adapter. Pulse frequency, amplitude, and duration were varied across discrete states between 4-200 Hz, 10-100 mA, and 50-2000 μs, respectively.ResultsA total of 420 trials were conducted, with 80 stimulation pulses per trial. The SEQ adapter demonstrated excellent preservation of signal integrity, matching the pulse characteristics of the originating stimulator within 1% error. The SEQ adapter operates as expected at pulse frequencies up to 160 Hz, with a noted failure mode at 200 Hz.ConclusionThe SEQ adapter represents an effective and low-cost solution to increase the utilization of SEQ in existing rehabilitation paradigms.

Background Slipping is one of the leading causes of falls among older adults. Older adults are considered to walk with a small anteroposterior (AP) component and a large mediolateral (ML) component of the required coefficient of friction (RCOF) owing to a short step length and a wide step width, respectively. However, limited information is available. Research question What are the effects of aging on the resultant RCOF (RCOFres) and its ML (RCOFML) and AP (RCOFAP) components during straight walking? Methods We used the kinetic and kinematic data of 188 participants aged 20–77 years from a publicly available database (National Institute of Advanced Industrial Science and Technology Gait Database 2015). The participants were divided into the following three groups: young group (n = 56; age range, 20–34 years), middle-aged group (n = 50; age range, 35–64 years), and old group (n = 82; age range, 65–77 years). Results The RCOFres and RCOFAP were lower in the old group than in the other groups, indicating a lower slip risk in this group. However, the RCOFML was higher and the step width was greater in the old group than in the other groups. The higher RCOFML and lower RCOFAP in the old group might be associated with slips in a more lateral direction. Significance Our findings suggest that older adults have a high risk of slipping in a more lateral direction. Shoes with high-slip resistance in the lateral direction are recommended to prevent hazardous lateral slips among older adults.

Background: The purpose of this study was to examine the impact of functional electrical stimulation (FES) induced co-activation of trunk muscles during quiet sitting. We hypothesized that FES applied to the trunk muscles will increase trunk stiffness. The objectives of this study were to: 1) compare the center of pressure (COP) fluctuations during unsupported and FES-assisted quiet sitting - an experimental study and; 2) investigate how FES influences sitting balance - an analytical (simulation) study. Methods The experimental study involved 15 able-bodied individuals who were seated on an instrumented chair. During the experiment, COP of the body projected on the seating surface was calculated to compare sitting stability of participants during unsupported and FES-assisted quiet sitting. The analytical (simulation) study examined dynamics of quiet sitting using an inverted pendulum model, representing the body, and a proportional-derivative (PD) controller, representing the central nervous system control. This model was used to analyze the relationship between increased trunk stiffness and COP fluctuations. Results In the experimental study, the COP fluctuations showed that: i) the mean velocity, mean frequency and the power frequency were higher during FES-assisted sitting; ii) the frequency dispersion for anterior-posterior fluctuations was smaller during FES-assisted sitting; and iii) the mean distance, range and centroidal frequency did not change during FES-assisted sitting. The analytical (simulation) study showed that increased mechanical stiffness of the trunk had the same effect on COP fluctuations as the FES. Conclusions The results of this study suggest that FES applied to the key trunk muscles increases the speed of the COP fluctuations by increasing the trunk stiffness during quiet sitting.

Background Individuals with an incomplete spinal cord injury (iSCI) are highly susceptible to falls during periods of walking or standing. We recently reported the findings of a novel intervention combining functional electrical stimulation with visual feedback balance training (FES + VFBT) on standing balance abilities among five individuals with motor iSCI. However, the previous publication did not report the perceived impact of the intervention on the participants’ lives. In this report, the experiences of these five individuals with incomplete spinal cord injury (iSCI) who had recently completed the four-week balance training program are described. Methods Five individuals with a motor iSCI took part in this study. Each individual was at least 12 months post-injury, capable of unassisted standing for 60 s and had a Berg Balance Scale Score Results Three themes were identified from the collected transcripts: (1) Perceived benefits across International Classification of Functioning, Disability and Health levels; (2) Change in perceived fall risk and confidence; (3) Motivation to keep going. Conclusions Participation in the FES + VFBT program resulted in perceived benefits that led to meaningful improvements in activities of daily living. Following completion of the training, individuals felt they still had the capacity to improve. Individuals felt they had increased their balance confidence, while a few participants also reported a decrease in their risk of falling. The inclusion of qualitative inquiry allows for the evaluation of the meaningfulness of an intervention and its perceived impact on the lives of the participants. Trial registration: NCT04262414 (retrospectively registered February 10, 2020)

The nociceptive flexion reflex (NFR) is used in neurophysiological research as an objective measure of nociception. NFR thresholds are reduced in numerous chronic pain pathologies, which are indicative of common central hyperexcitability within conditions. However, variation exists in both the NFR assessment and determinants of NFR threshold among research groups. Our purpose was to provide a review of the recent literature to (a) confirm the NFR threshold’s efficacy in identifying those with chronic pain compared to controls and (b) provide a narrative synthesis on the current methodology used to assess the NFR in clinical populations. We conducted a review of multiple databases (MEDLINE, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Google Scholar and Cochrane Library), including articles that reported controlled clinical studies of humans, in English, comparing NFR thresholds within chronic pain conditions to matched control subjects, published since the last NFR review in 2010. Our search resulted in nine studies included in our narrative synthesis and eight studies included in a meta-analysis. There was a significant pooled standardized mean difference in NFR threshold between chronic pain conditions and controls (−0.94, 95% confidence interval (CI) −1.33 to −0.55, p 2 = 87%, τ2 = 0.41, Q = 76.13, the degrees of freedom (df) = 11, p

Background The nociceptive flexion reflex is a physiological, polysynaptic reflex and refers to the level that an appropriate withdrawal response activates when a painful stimulus is detected. The nociceptive flexion reflex threshold (NFRthr) is defined as the lowest noxious stimulation intensity required to trigger a reflex motor response. Despite wide utilization and reports of the NFRthr, there has been no consensus on a standard and/or best method in assessment of the NFRthr. Objective To systematically review the literature that compared the NFRthr between individuals with fibromyalgia (FM) and healthy controls; and to identify a source of heterogeneity in these trials. Methods Employing the Cochrane methodology, we systematically searched Ovid MEDLINE, Embase, Cochrane Clinical Answers, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and PsycINFO for clinical case-controlled trials assessing the NFRthr in individuals with and without fibromyalgia from inception to July 2019. Selected articles were passed for data extraction and meta-analyses. We utilized the random-effects model for meta-analysis assuming the true effect size may vary between studies. The sample sizes as a possible source of heterogeneity in multiple meta-regressions were investigated. This systematic review and meta-analysis were registered in PROSPERO before data extraction. Results Nine studies met our criteria and were included in the meta-analysis. Methodologies and settings varied between studies, eg, stimulation intensity, duration, and the current increments. Only two articles comprehensively described and reported details about electromyogram amplification, latency, and sampling rate. Evidence from 423 patients with fibromyalgia and 326 healthy individuals suggested that there may not be a meaningful decreased NFRthr in patients (overall mean difference = -3.16; 95% CI:-6.82 to 0.50; Z = 1.69; P=0.09). Published effect sizes were not homogenous (I2 = 0.91, τ2 = 25.04, χ2 = 91.22, df = 8, P < 0.00001). The multiple meta-regression analyses indicated that total and female sample sizes might be the main sources of heterogeneity for the effect sizes SStotal = -0.0570, P = 0.040; SSfemale = -0.0569; P = 0.047. Conclusion Evidence suggests that the nociceptive flexion reflex threshold may not be different between patients with fibromyalgia and healthy controls. A unified and rigorous methodology and sample size calculation (probably sex specific investigation) is required for the assessment of nociceptive flexion reflex threshold in patients with fibromyalgia.

Objective: To evaluate test-retest reliability, agreement, and convergent validity of the Lean-and-Release test for the assessment of reactive stepping among individuals with incomplete spinal cord injury or disease (iSCI/D). Design: Multi-center cross-sectional multiple test design. Setting: SCI/D rehabilitation hospital and biomechanics laboratory. Participants: Individuals with motor incomplete SCI/D (iSCI/D). Interventions: None. Outcome Measures: Twenty-six participants attended two sessions to complete the Lean-and-Release test and a battery of clinical tests. Behavioral (i.e. one-step, multi-step, loss of balance) and temporal (i.e. timing of foot off, foot contact, swing of reactive step) parameters were measured. Test-retest reliability was determined with intraclass correlation coefficients, and agreement was evaluated with Bland–Altman plots. Convergent validity was assessed through correlations with clinical tests. Results: The behavioral responses were reliable for the Lean-and-Release test (ICC = 0.76), but foot contact was the only reliable temporal parameter using data from a single site (ICC = 0.79). All variables showed agreement according to the Bland–Altman plots. The behavioral responses correlated with scores of lower extremity strength (0.54, P

Background Myofascial pain syndrome (MPS) is a prevalent chronic pain disorder primarily characterized by myofascial trigger points (MTrPs). There is limited knowledge on the pathophysiology and mechanisms underlying MTrP and its development. Research has previously demonstrated the identification of MTrPs using ultrasound and vibration sonoelastography, although there is some contradictory evidence regarding if MTrPs present as hyper or hypoechoic regions. Electromyography (EMG) investigations of MTrP have demonstrated that MTrPs are usually located proximal to innervation zones where the peak surface EMG signals are obtained from. Central sensitization has been proposed as the primary mechanism underlying MTrP development. Central sensitization is associated with hyperexcitability of neuronal responses to normal or noxious stimuli. There is a need for a study that measures ultrasound image textural changes and motor unit activity responses in the muscle following sensitization. The purpose of this study is to determine whether sensitizing healthy muscle using capsaicin induces a regional change in image texture variables within the specific and surrounding muscles, as well as the motor unit frequency and amplitude changes that accompany them. This is an exploratory trial that aims to provide preliminary evidence on whether central sensitization is a direct cause of taut band and MTrP development. Methods Ethical approval was obtained from the University Health Network (UHN) Research Ethics Board. This proposed study is a single centered, factorial, randomized placebo-controlled trial with two independent variables, depth of capsaicin application and dose of capsaicin, for a total of six treatment arms and three control treatment groups. Discussion This will be the first study that assesses the B-mode ultrasound image texture of induced sensitized muscles and will provide more evidence on muscle motor unit activity and regional changes of central sensitization. Findings from this study may support one of few hypotheses proposed delineating the involvement of central sensitization in the development of trigger points. Trial registration National Institutes of Health ClinicalTrials.gov NCT03944889. Registered on May 07, 2019

Delivering short trains of electric pulses to the muscles and nerves can elicit action potentials resulting in muscle contractions. When the stimulations are sequenced to generate functional movements, such as grasping or walking, the application is referred to as functional electrical stimulation (FES). Implications of the motor and sensory recruitment of muscles using FES go beyond simple contraction of muscles. Evidence suggests that FES can induce short- and long-term neurophysiological changes in the central nervous system by varying the stimulation parameters and delivery methods. By taking advantage of this, FES has been used to restore voluntary movement in individuals with neurological injuries with a technique called FES therapy (FEST). However, long-lasting cortical re-organization (neuroplasticity) depends on the ability to synchronize the descending (voluntary) commands and the successful execution of the intended task using a FES. Brain-computer interface (BCI) technologies offer a way to synchronize cortical commands and movements generated by FES, which can be advantageous for inducing neuroplasticity. Therefore, the aim of this review paper is to discuss the neurophysiological mechanisms of electrical stimulation of muscles and nerves and how BCI-controlled FES can be used in rehabilitation to improve motor function.

BACKGROUND The nociceptive flexion reflex is a physiological, polysynaptic reflex triggered by a nociceptive stimulus activating a withdrawal response. In chronic musculoskeletal-related pain conditions, a decreased nociceptive flexion reflex threshold has been suggested as a possible recognition evidence for central sensitization that may cause alteration of central nervous system processing. OBJECTIVE The aim of the study was to systematically review reported comparisons of the nociceptive flexion reflex threshold in chronic pain patients and healthy individuals. METHODS Electronic databases covering studies published between January 1990 and December 2019 were systematically searched. After application of exclusion criteria, 20 studies including 28 trials were included in this review. For meta-analysis, we used a random-effects model and funnel plot for publication bias. This research was registered at PROSPERO (CRD42019140354). RESULTS Compared with healthy controls, standardized mean differences in nociceptive flexion reflex threshold were significantly lower in the total sample of chronic pain patients. Subgroup analysis indicated a homogenous decreased nociceptive flexion reflex threshold in studies reporting fibromyalgia, chronic pain, and joint pain while heterogeneity existed in other included pain conditions. CONCLUSIONS A lower nociceptive flexion reflex threshold in patients experiencing chronic pain conditions may imply hyperexcitability in central nervous system processing. As a preliminary study, the findings would act as a basis for developing a methodology assisting current clinical practices.

Gait disturbances are common in individuals with Parkinson's disease (PD). Although the basic patterns of walking are thought to be controlled by the brainstem and spinal networks, recent studies have found significant corticomuscular coherence in healthy individuals during walking. However, it still remains unknown how PD affects the cortical control of muscles during walking. As PD typically develops in older adults, it is important to investigate the effects of both aging and PD when examining disorders in patients with PD. Here, we assessed the effects of PD and aging on corticomuscular communication during walking by investigating corticomuscular coherence. We recorded electroencephalographic and electromyographic signals in 10 individuals with PD, 9 healthy older individuals, and 15 healthy young individuals. We assessed the corticomuscular coherence between the motor cortex and two lower leg muscles, tibialis anterior (TA) and medial gastrocnemius, during walking. Older and young groups showed sharp peaks in muscle activation patterns at specific gait phases, whereas the PD group showed prolonged patterns. Smaller corticomuscular coherence was found in the PD group compared with the healthy older group in the α band (8-12 Hz) for both muscles, and in the β band (16-32 Hz) for TA. Older and young groups did not differ in the magnitude of corticomuscular coherence. Our results indicated that PD decreased the corticomuscular coherence during walking, whereas it was not affected by aging. This lower corticomuscular coherence in PD may indicate lower-than-normal corticomuscular communication, although direct or indirect communication is unknown, and may cause impaired muscle control during walking.NEW & NOTEWORTHY Mechanisms behind how Parkinson's disease (PD) affects cortical control of muscles during walking remain unclear. As PD typically develops in the elderly, investigation of aging effects is important to examine deficits regarding PD. Here, we demonstrated that PD causes weak corticomuscular synchronization during walking, but aging does not. This lower-than-normal corticomuscular communication may cause impaired muscle control during walking.

Plantarflexors such as the soleus (SOL) and medial gastrocnemius (MG) play key roles in controlling bipedal stance; however, how the central nervous system controls the activation levels of these plantarflexors is not well understood. Here we investigated how the central nervous system controls the plantarflexors’ activation level during quiet standing in a cosine tuning manner where the maximal activation is achieved in a preferred direction (PD). Furthermore, we investigated how spinal cord injury affects these plantarflexors’ activations. Thirteen healthy adults (AB) and thirteen individuals with chronic, incomplete spinal cord injury (iSCI) performed quiet standing trials. Their body kinematics and kinetics as well as electromyography signals from the MG and SOL were recorded. In the AB group, we found that the plantarflexors followed the cosine tuning manner during quiet standing. That is, MG was most active when the ratio of plantarflexion torque to knee extension torque was ~2:-3, whereas SOL was most active when the ratio was ~2:1. This suggests that the SOL muscle, despite being a monoarticular muscle, is sensitive to both ankle plantarflexion and knee extension during quiet standing. The difference in the PDs accounts for the phasic activity of MG and for the tonic activity of SOL. Unlike the AB group, the MG’s activity was similar to the SOL’s activity in the iSCI group, and the SOL PDs were similar to those in the AB group. This result suggests that chronic iSCI affects the control strategy, i.e., cosine tuning, for MG, which may affect standing balance in individuals with iSCI. NEW & NOTEWORTHY Soleus muscle shows a tonic activity whereas medial gastrocnemius muscle shows a phasic activity during quiet standing. Cosine tuning and their preferred direction account for the different muscle activation patterns between these two muscles. In individuals with chronic incomplete spinal cord injury, the preferred direction of gastrocnemius medial head is affected, which may result in their deteriorated standing balance.

Electrical stimulation for inducing muscle contraction can be divided into peripheral nerve stimulation (PNS) and motor point stimulation (MPS). Although the neural pathways activated by PNS have been well studied, those by MPS are still unclear. Here we investigated whether MPS activates Ia-sensory nerves and induces antidromic firing of motor nerves. Ten able-bodied males and females participated in this study. We confirmed that soleus MPS did not induce the H-reflex while soleus PNS did. Furthermore, MPS of the tibialis anterior muscle did not induce the reciprocal inhibition of soleus muscle while PNS did. For testing the effect of MPS on motor neuron excitability, we examined the H-reflex modulation by soleus MPS. When the conditioning and test interval was under 100-ms and the conditioning stimulus intensity was above 30-mA, soleus MPS induced the H-reflex inhibition. This suggests that soleus MPS produces antidromic firing that can induce after-hyperpolarization. These results suggest that MPS predominantly activates the motor nerve without depolarizing the Ia-sensory nerve. Since MPS is applicable to larger number of muscles compared to PNS, utilizing MPS can lead to more versatile neuromodulation of the spinal cord.

Recent work suggests that functional electrical stimulation can be used to enhance dynamic trunk stability following spinal cord injury. In this context, knowledge of the relation between trunk kinematics and muscle activation in non-disabled individuals may assist in developing kinematics-based neuroprostheses. Our objective was therefore to predict the activation profiles of the major trunk muscles from trunk kinematics following multi-directional perturbations during sitting. Trunk motion and electromyograms (EMG) from ten major trunk muscles were acquired in twelve non-disabled, seated individuals who experienced a force of approximately 200 N applied to the trunk in eight horizontal directions. A linear, time-invariant model with feedback gains on angular trunk displacement, velocity, and acceleration was optimized to predict the EMG from trunk kinematics. For each muscle, only the three directions that produced the largest EMG response were considered. Our results indicate that the time course of the processed EMG was similar across muscles and directions and that the model accounted for 68–92% of the EMG variance. A combination of neural and biomechanical mechanisms associated with trunk control can explain the obtained model parameters. Future work will apply the gained insights in the design of movement-controlled neuroprostheses for facilitating trunk stability following spinal cord injury.

STUDY DESIGN Retrospective analysis. OBJECTIVE To describe the dynamic fluctuation of truncal shift parameters during quiet standing in healthy young individuals using biomechanical analyses. SUMMARY OF BACKGROUND DATA Coronal decompensation (CD) and sagittal vertical axis (SVA) are the key radiographic parameters to assess static truncal stability, with the known cut-off value of 4 cm for SVA in determining severity of spinal deformity. These values are obtained at a specific moment during quiet standing, when the posture innately changes. Thus, unassessed truncal sway could potentially compromise the reliability of these measurements. METHODS Previously obtained biomechanical data with 11 male, healthy participants aged 16 to 29 were used to quantify the dynamic sway of standing posture. The participants were instructed to quietly stand with surface reflective markers for 130 seconds. The midpoint of bilateral acromia was used as a surrogate for C7 vertebral body. The time series of coronal and sagittal shifts of C7 to sacrum were measured as quasi-coronal decompensation (CD) and quasi-sagittal vertical axis (SVA) to simulate CD and SVA on radiographs. A force platform was also used to measure the center of pressure (COP) displacement. RESULTS The group averages of the dynamic sway range were 20.2 ± 4.1 mm (range: 15.1-28.6) in the sagittal plane (quasi-SVA) and 9.8 ± 3.2 mm (range: 5.5-15.2) in the coronal plane (quasi-CD). There were significant correlations between quasi-CD sway and medial-lateral COP velocity (Pearson r = 0.65, P = 0.03), as well as between quasi-SVA sway and COP sway area (r = 0.65, P = 0.03). CONCLUSION Given the considerable fluctuation of quasi-SVA and quasi-CD during quiet standing, the reliability of radiographic measurement using CD and SVA at a specific moment can be substantially compromised. The assessment based on the currently proposed cut-off values should be interpreted with caution, and repeat examinations are warranted. LEVEL OF EVIDENCE 4.

First Place Award Submission - CA147Category: Clinical ApplicationManagement of obesity after spinal cord injury: a systematic reviewMir Hatef Shojaei1, Mohammad Alavinia1, B. Catharine Craven1,21N...

Spinal cord injury (SCI) can result in paralysis of trunk muscles, which can affect sitting balance. The objective of this study was to analyze trunk muscle coordination of individuals with thoracic SCI and compare it to able-body individuals. A total of 27 individuals were recruited and subdivided into: (a) high thoracic SCI; (b) low thoracic SCI; and (c) able-body groups. Participants were seated and asked to lean their trunk in eight directions while trunk muscle activity was recorded. Muscle coordination was assessed using the non-negative matrix factorization (NMF) method to extract muscle modules, which are the synergistic trunk muscle activations, and their directional activation patterns. Our results showed that individuals with SCI used less muscle modules, more co-contractions, and less directional tuning, compared to able-bodied people. These results suggest impaired and simplified muscle coordination due to the loss of supraspinal input after SCI. Observed variability in muscle coordination within SCI groups also suggests that other mechanisms such as spasticity and muscle stretch reflexes or individual factors such as experience and training contributed to the postural muscle synergies. Overall, muscle coordination deficits revealed impaired neuromuscular strategies which provide implications for rehabilitation of trunk muscles during sitting balance after SCI.

To determine the efficacy of functional electrical stimulation therapy assisted walking (FES-T) compared to a conventional aerobic and resistance training (CONV) with respect to bone biomarkers and lower extremity bone strength outcomes among adults with chronic motor incomplete spinal cord injury (SCI).Parallel group randomized controlled trial ( www.clinicaltrials.gov - NCT0020196819). Site: Tertiary academic rehabilitation centre in Canada.Adults with chronic (≥18 months) motor incomplete SCI (C2-T12 AIS C-D) were consented and randomized to FES-T or CONV training for 45 minutes thrice-weekly for 4 months. Osteocalcin (OC), β-cross laps (CTX) and sclerostin were assessed at baseline, and 4 months. Similarly, total hip, distal femur and proximal tibia region bone mineral density (BMD) via DXA (4500A, Hologic Inc. Waltham, MA, USA) and tibia bone quality via pQCT (Stratec XCT-2000, Mezintecknik, Pforzheim, Germany) were assessed at baseline, 4, and 12 months. Between group differences were analyzed using repeated measures general linear models.Thirty-four participants (17 FES-T, 17 CONV) consented and were randomized, 27 participants completed the 4-month intervention and 12-month outcome assessments. Participants in the FES-T arm had a decrease in CTX and a significant increase in OC at intervention completion (P0.05). Significant biomarker changes were not observed in the CONV group. No within or between group differences from baseline were observed in sclerostin or bone strength.Four months of FES-T improved bone turnover (increase in OC and decrease in CTX) but not bone strength among individuals with chronic SCI. Future, long term FES-T may augment lower extremity bone strength.

Balance training in the aquatic environment is often used in rehabilitation practice to improve static and dynamic balance. Although aquatic therapy is widely used in clinical practice, we still lack evidence on how immersion in water actually impacts postural control. We examined how postural sway measured using centre of pressure and trunk acceleration parameters are influenced by the aquatic environment along with the effects of visual information. Our results suggest that the aquatic environment increases postural instability, measured by the centre of pressure parameters in the time-domain. The mean velocity and area were more significantly affected when individuals stood with eyes closed in the aquatic environment. In addition, a more forward posture was assumed in water with eyes closed in comparison to standing on land. In water, the low frequencies of sway were more dominant compared to standing on dry land. Trunk acceleration differed in water and dry land only for the larger upper trunk acceleration in mediolateral direction during standing in water. This finding shows that the study participants potentially resorted to using their upper trunk to compensate for postural instability in mediolateral direction. Only the lower trunk seemed to change acceleration pattern in anteroposterior and mediolateral directions when the eyes were closed, and it did so depending on the environment conditions. The increased postural instability and the change in postural control strategies that the aquatic environment offers may be a beneficial stimulus for improving balance control.

Introduction Transcutaneous neuromuscular electrical stimulation (NMES) can generate muscle contractions for rehabilitation and exercise. However, NMES-evoked contractions are limited by fatigue when they are delivered "conventionally" (CONV) using a single active electrode. Researchers have developed "sequential" (SEQ) stimulation, involving rotation of pulses between multiple "aggregated" (AGGR-SEQ) or "distributed" (DISTR-SEQ) active electrodes, to reduce fatigue (torque-decline) by reducing motor unit discharge rates. The primary objective was to compare fatigue-related outcomes, "potentiation," "variability," and "efficiency" between CONV, AGGR-SEQ, and DISTR-SEQ stimulation of knee extensors in healthy participants. Methods Torque and current were recorded during testing with fatiguing trains using each NMES type under isometric and isokinetic (180°/s) conditions. Results Compared with CONV stimulation, SEQ techniques reduced fatigue-related outcomes, increased potentiation, did not affect variability, and reduced efficiency. Conclusions SEQ techniques hold promise for reducing fatigue during NMES-based rehabilitation and exercise; however, optimization is required to improve efficiency. Muscle Nerve 56: 271-281, 2017.

Many individuals with lower limb amputations or neuromuscular impairments face mobility challenges attributable to suboptimal assistive device design. Forward dynamic modeling and simulation of human walking using conventional biomechanical gait models offer an alternative to intuition-based assistive device design, providing insight into the biomechanics underlying pathological gait. Musculoskeletal models enable better understanding of prosthesis and/or exoskeleton contributions to the human musculoskeletal system, and device and user contributions to both body support and propulsion during gait. This paper reviews current literature that have used forward dynamic simulation of clinical population musculoskeletal models to perform assistive device design optimization using optimal control, optimal tracking, computed muscle control (CMC) and reflex-based control. Musculoskeletal model complexity and assumptions inhibit forward dynamic musculoskeletal modeling in its current state, hindering computational assistive device design optimization. Future recommendations include validating musculoskeletal models and resultant assistive device designs, developing less computationally expensive forward dynamic musculoskeletal modeling methods, and developing more efficient patient-specific musculoskeletal model generation methods to enable personalized assistive device optimization.

Context/Objective: Incomplete spinal cord injury (iSCI) causes deficits in balance control. The Mini-Balance Evaluation Systems Test (mini-BESTest) is a comprehensive measure; however, further testing of its psychometric properties among the iSCI population is needed. We evaluated the mini-BESTest’s test-retest reliability, and concurrent and convergent validity among individuals living with iSCI for more than one year. Design: Cross-sectional study. Setting: Rehabilitation hospital. Participants: Twenty-one individuals with chronic motor iSCI (14 females, mean age 56.8 ± 14.0 years). Interventions: None. Outcome Measures: Participants completed the mini-BESTest at two sessions spaced two weeks apart. At the second session, participants performed tests of lower extremity muscle strength and quiet standing on a force platform with eyes opened (EO) and eyes closed (EC). Intraclass correlation coefficients (ICC) evaluated test-retest reliability. To evaluate concurrent and convergent validity, Pearson’s correlation coefficient (r) quantified relationships between mini-BESTest scores and measures of center of pressure (COP) velocity during EO and EC standing, and lower extremity muscle strength, respectively. Results: Test-retest reliability of the mini-BESTest total score and sub-scale scores were high (ICC = 0.94–0.98). Mini-BESTest scores were inversely correlated with COP velocity when standing with EO (r = 0.54–0.71, P

Neuromuscular electrical stimulation is conventionally applied through a single pair of electrodes over the muscle belly, denominated single electrode stimulation (SES). SES is limited by discomfort and incomplete motor-unit recruitment, restricting electrically-evoked torque and promoting premature fatigue-induced torque-decline. Sequential stimulation involving rotation of pulses between multiple pairs of electrodes has been proposed as an alternative, denominated spatially distributed sequential stimulation (SDSS). The present aim was to compare discomfort, maximal-tolerated torque, and fatigue-related outcomes between SES and SDSS of tibialis anterior. Ten healthy participants completed two experimental sessions. The self-reported discomfort at sub-maximal torque, the maximal-tolerated torque, fatigue-induced torque-decline during, and doublet-twitch torque at 10- and 100-Hz before and after, 300 intermittent (0.6-s-ON-0.6-s-OFF) isokinetic contractions were compared between SES and SDSS. SDSS stimulation improved fatigue-related outcomes, whereas increased discomfort and reduced maximal-tolerated torque. SDSS holds promise for reducing fatigue. However, limited torque production and associated discomfort may limit its utility for rehabilitation/training.

STUDY DESIGN: Case series. OBJECTIVES: This case series describes how the aquatic environment influences gait initiation in terms of the center of pressure (COP) excursion, impulses, trunk acceleration, and perceptions of participants with incomplete spinal cord injury (iSCI). SETTING: Tertiary Rehabilitation Hospital, Ontario, Canada. METHODS: Five individuals with iSCI (four cervical injuries/one thoracic injury, AIS D) participated in the study. Baseline clinical balance was evaluated by Berg Balance Scale and Mini-Balance Evaluation System Test. Participants initiated gait on a waterproof force plate and walked ~4 steps, in water and on land. COP trajectories during anticipatory and execution phases, impulses, and trunk acceleration parameters were investigated. Perceptions of walking in both environments were obtained using an interview. RESULTS: COP trajectory was prominently longer when individuals stepped forward. A decrease in velocity of COP was observed predominantly in the AP direction during stepping. Non-normalized vertical impulses decreased as the AP impulses increased, in water compared to land. Upper to lower trunk acceleration ratios showed how water resistance influenced the lower trunk acceleration. Most of participants reported that walking in water was challenging, but safer than on land. CONCLUSIONS: Participants with higher balance function seemed to have more pronounced changes in anticipatory and execution phases’ duration, length and velocity of COP. A faster anticipatory phase and a slower execution phase were observed in water than on land. Participants walked in water using a different trunk control strategy than on land and reported no fear of falling when walking in water versus land.

Cross sectional. To compare the reactive stepping ability of individuals living with incomplete spinal cord injury or disease (SCI/D) to that of sex- and age-matched able-bodied adults. A tertiary SCI/D rehabilitation center in Canada. Thirty-three individuals (20 with incomplete SCI/D) participated. Participants assumed a forward lean position in standing whilst 8–12% of their body weight was supported by a horizontal cable at waist height affixed to a rigid structure. The cable was released unexpectedly, simulating a forward fall and eliciting one or more reactive steps. Behavioral responses (i.e., single step versus non-single step) were compared using a Chi-square test. The following temporal parameters of reactive stepping were compared using t-tests: the onset of muscle activation in 12 lower extremity muscles (six per limb) and step-off, step contact and swing time of the stepping leg. Behavioral responses were significantly different between groups (χ2 = 13.9 and p

Made available in DSpace on 2022-04-30T20:25:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-01 Ontario Neurotrauma Foundation Natural Sciences and Engineering Research Council of Canada Canadian Institutes of Health Research Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung Study design: This work is a case series. Objectives: We assessed the influence of the aquatic environment on quasi-static posture by measuring center of pressure (COP) sway and trunk acceleration parameters after incomplete spinal cord injury (iSCI) in water and on land. Setting: Tertiary Rehabilitation Hospital, Ontario, Canada. Methods: Six adult participants with iSCI (4 cervical/2 thoracic injuries, AIS D) were enrolled. Baseline balance was assessed by the Berg Balance Scale and Mini-Balance Evaluation System Test. Participants stood on a waterproof force plate for one minute per trial on land and in water; participants completed testing with their eyes open or closed in random order over 10 trials. Individuals’ perceptions of their standing balance were obtained. COP and trunk acceleration parameters were analyzed in the time-domain. Results: COP sway and upper to lower trunk acceleration ratios in the AP direction increased in water, which was in contrast to standing on land in both visual conditions for 5/6 participants. Three participants (P1, P3 & P4) with greater sensorimotor deficits had larger COP sway in water with the eyes closed. Two (P1 & P4) of six participants reported more discomfort standing in water than standing on land. Conclusions: Increased COP sway seemed to reflect the balance and sensorimotor impairments of the participants, especially when standing with eyes closed in water. Although most participants (4/6) perceived that they swayed more in water in contrast to on land, 5 out of 6 participants reported that water felt like a safer environment in which to stand. Toronto Rehabilitation Institute – University Health Network Rehabilitation Sciences Institute – University of Toronto Department of Mechanical Engineering University of Alberta Department of Medicine Rehabilitation Sciences Institute – University of Toronto Institute of Biomaterials and Biomedical Engineering University of Toronto Institute of Biosciences – Sao Paulo State University Institute of Biomaterials and Biomedical Engineering Rehabilitation Sciences Institute – University of Toronto Department of Physical Therapy Rehabilitation Sciences Institute Institute of Medical Science University of Toronto Institute of Biosciences – Sao Paulo State University Natural Sciences and Engineering Research Council of Canada: 249669 Canadian Institutes of Health Research: 95662 Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung: P300P2-147865

Objectives: We aimed to investigate the possibility of sample size as a possible source of heterogeneity in trials comparing the nociceptive flexion reflex threshold (NFRthr) in fibromyalgia (FM) patients and healthy controls. Methods: A systematic search strategy was designed and conducted in electronic databases such as Ovid MEDLINE, Cochrane Libraries, Embase, and PsycINFO. In total, nine scholarly records were filtered by the inclusion and exclusion criteria, passed for data extraction (e.g. study designs and settings; methodology; total, male, and female sample sizes in FM and healthy control groups, and effect sizes), and statistical analyses (e.g. metaanalysis and meta-regression). Using random-effects model, the effect size (i.e. mean difference between the NFRthr in FM patients and healthy controls) was meta-analyzed. Investigating the sample size as a possible source of heterogeneity and utilizing a restricted maximum likelihood (REML) technique, the trials’ effect sizes were meta-regressed in multiple meta-regression against the total, male, and female sample sizes. Prior to any investigations, the aims of this research were registered in the International Prospective Register of Systematic Reviews (PROSPERO; registration number: CRD42019140354). Results: Results indicated the deficit in NFRthr (overall mean difference = −3.16; 95% 𝐶𝐼: −6.82 𝑡𝑜 0.50) was heterogenous (𝐼 2 = 0.91, 𝜏 2 = 25.04, 𝜒2= 91.22, df & < 0.00001) and the overall effect was not statistically significant (Z = 1.69; 𝑃 = 0.09). The multiple meta-regression analyses indicated that one of the main sources of bias to the effect size in the trials was found to be the total (𝑆𝑆𝑡𝑜𝑡𝑎𝑙 = −0.0570; 𝑃 = 0.040) and female (𝑆𝑆𝑓𝑒𝑚𝑎𝑙𝑒 = −0.0569; 𝑃 = 0.047) sample sizes that participated in the studies. Conclusion: The findings suggest that the total and female sample sizes might be possible sources of bias to effect sizes determined in NFRthr in FM patient and healthy controls. A possible solution might be to conduct sex-specific trials to determine the NFRthr among FM patients in future research. Funding Statement: Authors received no source of funding for this research. Declaration of Interests: Authors declare no conflict of interest. Ethics Approval Statement: PROSPERO; registration number: CRD42019140354

In human bipedal walking, the peak value of the traction coefficient (i.e., the ratio of the shear force component to the vertical force component exerted on the floor) produced shortly after heel contact is termed as the required coefficient of friction (RCOF). Based on a bipedal inverted pendulum model, with a whole-body center of mass (COM) and reaction forces applied at the center of pressure (COP) of standing feet, RCOF in the sagittal plane (RCOFy) can be expressed as the sum of the tangent of the COM–COP angle and a residual term (RT), mainly comprising the moment around COM. In this study, we investigated the contribution of the tangent of the COM–COP angle to RCOFy during straight walking. The study involved four healthy young adult males. The participants were asked to walk on a 5-m long carpeted walkway. Each participant performed nine trials, i.e., three walking speeds (1, 1.4, and 1.9m/s)×three step lengths (0.55, 0.75, and 0.95m). COM was estimated using motion capture. COPs for the left and right feet were measured using eight force plates embedded in the walkway. RCOFy was calculated from the anterior–posterior and vertical ground reaction force components measured using the force plates. We found that the tangent of the COM–COP angle accounted for 91%–124% of the RCOFy value. This percentage tended to decrease with increasing walking speed (p

Trunk muscles are responsible for maintaining trunk stability during sitting. However, the effects of anticipation of perturbation on trunk muscle responses are not well understood. The objectives of this study were to identify the responses of trunk muscles to sudden support surface translations and quantify the effects of anticipation of direction and time of perturbation on the trunk neuromuscular responses. Twelve able-bodied individuals participated in the study. Participants were seated on a kneeling chair and support surface translations were applied in the forward and backward directions with and without direction and time of perturbation cues. The trunk started moving on average approximately 40ms after the perturbation. During unanticipated perturbations, average latencies of the trunk muscle contractions were in the range between 103.4 and 117.4ms. When participants anticipated the perturbations, trunk muscle latencies were reduced by 16.8±10.0ms and the time it took the trunk to reach maximum velocity was also reduced, suggesting a biomechanical advantage caused by faster muscle responses. These results suggested that trunk muscles have medium latency responses and use reflexive mechanisms. Moreover, anticipation of perturbation decreased trunk muscles latencies, suggesting that the central nervous system modulated readiness of the trunk based on anticipatory information.

We investigated age-related differences in the required coefficient of friction (RCOF) during 90° turning, the difference of RCOF during step and spin turn, and how affects observed differences. Sixteen healthy young and healthy older adults (eight men and eight women in each group) participated. Participants performed 90° step and spin turns to the right at a self-selected normal speed. Older adults turned with lower RCOF than the young adults during both step and spin turns. This was associated with reduced mediolateral (ML) RCOF component (RCOFML) for the older adults. Reduced RCOFML in older adults was associated with reductions in the ML component of the lean angle of the body during turning. This age-related gait changes during turning can be compensatory mechanisms that allowed older adults to turn while reducing the risk of slipping. Spin turns exhibited lower RCOF, resulting from significantly lower RCOFML, than step turns in young and older adults; thus, spin turning is a safer turning strategy for preventing lateral slips. This may suggest that, in older adults, slip prevention may take precedence over balance recovery after slips sustained during turning. These results illustrate a turning gait mechanism that helps prevent slips and falls, and how age affects this mechanism.

Background Individuals with cervical spinal cord injury usually sustain impairments to the trunk and upper and lower limbs, resulting in compromised sitting balance. The objectives of this study were to: 1) compare postural control of individuals with cervical spinal cord injury and able-bodied individuals; and 2) investigate the effects of foot support and trunk fluctuations on postural control during sitting balance. Methods Ten able-bodied individuals and six individuals with cervical spinal cord injury were asked to sit quietly during two 60 s trials. The forces exerted on the seat and the foot support surfaces were measured separately using two force plates. The global centre of pressure sway was obtained from the measurements on the two force plates, and the sway for each force plate was calculated individually. Findings Individuals with spinal cord injury had at least twice as large global and seat sways compared to able-bodied individuals, while foot support sway was not significantly different between the two groups. Comparison between global and seat sways showed that anterior–posterior velocity of global sway was larger compared to the seat sway in both groups. Interpretation Postural control of individuals with cervical spinal cord injury was worse than that of able-bodied individuals. The trunk swayed more in individuals with spinal cord injury, while the stabilization effect of the feet did not differ between the groups. Foot support affected anterior–posterior fluctuations in both groups equally. Thus, trunk control is the dominant mechanism contributing to sitting balance in both able-bodied and spinal cord injury individuals.

A common source of error when detecting heel-strike moments utilizing split force-plate treadmills is unwillingly stepping on contra-lateral force-plate. In this study, we quantified this error when heel-strike was detected based on such erroneous data and compared three methods to investigate how well the heel-strikes and stride-intervals were detected with erroneous data. Eleven subjects walked on a split force-plate treadmill for more than 20min. We used 20N and 50% body-weight thresholds to detect the heel-strike moments (HS20N and HS50%, respectively). Besides, we used linear approximation to estimate the unaffected force profile from affected force-plate data, and subsequently to detect the heel-strike moments (HSest). We used heel-strike moments detected by a foot-switch as a reference to compare accuracy of HS20N, HS50% and HSest. HS20N and HSest detected heel-strike moments accurately for unaffected force-plate data (median(max) errors for all subjects: 9(23) and 9(37) ms) but HS50% showed significantly larger errors (52(74) ms). Unlike HS50% and HSest, HS20N was considerably affected by the affected force-plate data (23(68) ms). The error in stride-interval measurement was relatively small using any methods for unaffected force-plate data (3(7), 6(8), and 6(12) ms), while stride-interval errors were large for some subjects when using HS20N for affected data (6(175) ms). We concluded that unwillingly stepping on contra-lateral force-plate occurred a few percent and up to 37.7% of all strides (median: 12.9%). Our proposed method (HSest) robustly showed small errors for heel-strike detection and stride-interval calculation consistently among subjects, while HS50% and HS20N showed large errors depending on subjects.

Many postural control studies employ a single-mass inverted pendulum model (IPM) to represent the body during standing. However, it is not known to what degree and for what conditions the model's kinematic assumptions are valid.Our first objective was to quantify the IPM error, corresponding to a distance change between the ankle joint and center of mass (COM) during unrestricted, natural, unperturbed standing. A second objective was to quantify the error of having the ankle joint angle represent the COM angle.Eleven young participants completed five standing conditions: quiet standing with eyes open (EO) and closed (EC), voluntarily swaying forward (VSf) and backward (VSb), and freely moving (FR). The modified Helen-Hayes marker model was used to capture the body kinematics.The COM distance changed0.1% during EO and EC,0.25% during VSf and VSb, and1.5% during FR. The ankle angle moderately and positively correlated with the COM angle for EO, EC, and VSf, indicating that temporal features of the ankle angle moderately represent those of the COM angle. However, a considerable offset between the two existed, which needs to be considered when estimating the COM angle using the ankle angle. For VSb and FR, the correlation coefficients were low and/or negative, suggesting that a large error would result from using the ankle angle as an estimate of the COM angle.Insights from this study will be critical for deciding when to use the IPM in postural control research and for interpreting associated results.

Increased variability of spatio-temporal features while walking is related to increased risk of falls. It is thought that variability in foot placement and timing reflects responses to mechanical instability while walking. The purpose of this study was to determine whether ‘extreme’ values of step length, width and time follow transient periods of low mechanical stability during the single support phase of gait in healthy young adults. We conducted secondary analysis of a portion of an existing dataset. Eleven healthy adults walked on an instrumented treadmill. Participants were outfitted with reflective markers and completed two 1-minute periods of walking at each of 3 speeds (0.8 m/s, 1.2 m/s, and 1.6 m/s). Margins of stability were calculated relative to the anterior, posterior, lateral, and medial boundaries of the base of support, and the value at heel strike and the minimum value during the first half of each single-support phase were extracted. Step length, swing time, and step width were calculated from motion capture and ground reaction force data. Extreme values for consecutive steps were identified using Poincaré plots, and margins of stability in each direction were compared between ‘normal’ and ‘extreme’ steps. Margins of stability in both the anterior and medial direction were lower prior to long and wide steps, respectively. Margins of stability in the anterior and medial directions were lower prior to quick steps, and margins of stability in the posterior and lateral directions were lower prior to slow steps. There were either no significant differences in margin of stability between ‘normal’ and ‘extreme’ steps at heel strike, or the direction of the relationship was reversed to that observed during single support. These data suggest that spatio-temporal variability may reflect adjustments in step placement and timing to compensate for transient periods of low mechanical stability when walking.

Closed-loop controlled functional electrical stimulation (FES) applied to the lower limb muscles can be used as a neuroprosthesis for standing balance in neurologically impaired individuals. The objective of this study was to propose a methodology for designing a proportional-integral-derivative (PID) controller for FES applied to the ankle muscles toward maintaining standing balance for several minutes and in the presence of perturbations. First, a model of the physiological control strategy for standing balance was developed. Second, the parameters of a PID controller that mimicked the physiological balance control strategy were determined to stabilize the human body when modeled as an inverted pendulum. Third, this PID controller was implemented using a custom-made Inverted Pendulum Standing Apparatus that eliminated the effect of visual and vestibular sensory information on voluntary balance control. Using this setup, the individual-specific FES controllers were tested in able-bodied individuals and compared with disrupted voluntary control conditions in four experimental paradigms: (i) quiet-standing; (ii) sudden change of targeted pendulum angle (step response); (iii) balance perturbations that simulate arm movements; and (iv) sudden change of targeted angle of a pendulum with individual-specific body-weight (step response). In paradigms (i) to (iii), a standard 39.5-kg pendulum was used and 12 subjects were involved. In paradigm (iv) 9 subjects were involved. Across the different experimental paradigms and subjects, the FES-controlled and disrupted voluntarily-controlled pendulum angle showed root mean square errors of less than 1.2 deg and 2.3 deg, respectively. The root mean square error (all paradigms), rise time, settle time, and overshoot (paradigms (ii) and (iv)) in FES-controlled balance were significantly smaller or tended to be smaller than those observed with voluntarily-controlled balance, implying improved steady-state and transient responses of FES-controlled balance. At the same time, the FES-controlled balance required similar torque levels (no significant difference) as voluntarily-controlled balance. The implemented PID parameters were to some extent consistent among subjects for standard weight conditions and did not require prolonged individual-specific tuning. The proposed methodology can be used to design FES controllers for closed-loop controlled neuroprostheses for standing balance. Further investigation of the clinical implementation of this approach for neurologically impaired individuals is needed.

The precise role of the human primary motor cortex in walking is unknown. Our previous study showed that the primary motor cortex may contribute to specific requirements of walking (i.e., maintaining a constant movement frequency and bilaterally coordinating the feet). Because aging can impair (i) the ability to fulfill the aforementioned requirements and (ii) corticomuscular communication, we hypothesized that aging would impair the motoneuronal recruitment by the primary motor cortex during bilateral cyclical movements. Here, we used corticomuscular coherence (i.e., coherence between the primary motor cortex and the active muscles) to examine whether corticomuscular communication is affected in older individuals during cyclical movements that shared some functional requirements with walking. Fifteen young men and 9 older men performed cyclical, anti-phasic dorsiflexion and plantarflexion of the feet while seated. Coherence between the midline primary motor cortex and contracting leg muscles cyclically increased in both age groups. However, the coherence of older participants was characterized by (i) lower magnitude and (ii) mediolaterally broader and more rostrally centered cortical distributions. These characteristics suggest that aging changes how the primary motor cortex participates in the cyclical movements, and such change may extend to walking.

Multi-channel surface functional electrical stimulation (FES) for walking has been used to improve voluntary walking and balance in individuals with spinal cord injury (SCI).To investigate short- and long-term benefits of 16 weeks of thrice-weekly FES-assisted walking program, while ambulating on a body weight support treadmill and harness system, versus a non-FES exercise program, on improvements in gait and balance in individuals with chronic incomplete traumatic SCI, in a randomized controlled trial design.Individuals with traumatic and chronic (≥18 months) motor incomplete SCI (level C2 to T12, American Spinal Cord Injury Association Impairment Scale C or D) were recruited from an outpatient SCI rehabilitation hospital, and randomized to FES-assisted walking therapy (intervention group) or aerobic and resistance training program (control group). Outcomes were assessed at baseline, and after 4, 6, and 12 months. Gait, balance, spasticity, and functional measures were collected.Spinal cord independence measure (SCIM) mobility sub-score improved over time in the intervention group compared with the control group (baseline/12 months: 17.27/21.33 vs. 19.09/17.36, respectively). On all other outcome measures the intervention and control groups had similar improvements. Irrespective of group allocation walking speed, endurance, and balance during ambulation all improved upon completion of therapy, and majority of participants retained these gains at long-term follow-ups.Task-oriented training improves walking ability in individuals with incomplete SCI, even in the chronic stage. Further randomized controlled trials, involving a large number of participants are needed, to verify if FES-assisted treadmill training is superior to aerobic and strength training.

Traumatic spinal cord injury (SCI) results in substantial reductions in lower extremity muscle mass and bone mineral density below the level of the lesion. Whole-body vibration (WBV) has been proposed as a means of counteracting or treating musculoskeletal degradation after chronic motor complete SCI. To ascertain how WBV might be used to augment muscle and bone mass, we investigated whether WBV could evoke lower extremity electromyography (EMG) activity in able-bodied individuals and individuals with SCI, and which vibration parameters produced the largest magnitude of effect.Ten male subjects participated in the study, six able-bodied and four with chronic SCI. Two different manufacturers' vibration platforms (WAVE(®) and Juvent™) were evaluated. The effects of vibration amplitude (0.2, 0.6 or 1.2 mm), vibration frequency (25, 35, or 45 Hz), and subject posture (knee angle of 140°, 160°, or 180°) on lower extremity EMG activation were determined (not all combinations of parameters were possible on both platforms). A novel signal processing technique was proposed to estimate the power of the EMG waveform while minimizing interference and artifacts from the plate vibration.WBV can elicit EMG activity among subjects with chronic SCI, if appropriate vibration parameters are employed. The amplitude of vibration had the greatest influence on EMG activation, while the frequency of vibration had lesser but statistically significant impact on the measured lower extremity EMG activity.These findings suggest that WBV with appropriate parameters may constitute a promising intervention to treat musculoskeletal degradation after chronic SCI.

Trunk instability during sitting is a major problem following neuromuscular injuries such as stroke and spinal cord injury. In order to develop new strategies for alleviating this problem, a better understanding of the intrinsic contributions of the healthy trunk to sitting control is needed. As such, this study set out to propose and validate a novel methodology for determining multidirectional trunk stiffness during sitting using randomized transient perturbations. Fifteen healthy individuals sitting naturally on a custom-made seat were randomly perturbed in eight horizontal directions. Trunk stiffness and damping were quantified using force and trunk kinematics in combination with translational and torsional models of a mass-spring-damper system. The results indicate that stiffness and damping of the healthy trunk are roughly symmetrical between the two body sides. Moreover, both quantities are smallest in the anterior and largest in the lateral directions. In conclusion, a novel protocol for identifying intrinsic trunk stiffness and damping has been developed, eliminating anticipation effects with respect to perturbation timing and direction. Subsequent studies will use these findings as a reference not only for quantifying trunk stiffness and damping in individuals with various neuromuscular disorders, but also for assessing whether neuroprostheses could increase upper body stiffness and, hence, stability.

Objective: Whole body vibration has been studied in populations experiencing neuromuscular degradation, including the elderly and individuals with neurological disorders, but methodological standardization is required to clarify its therapeutic effects. The characteristics of the vibrations actually delivered by commercial platforms are rarely measured or reported. Our objective was to quantify the vibrations (frequency, amplitude and peak acceleration) produced by several commercial platforms across different settings. Methods: Laser and accelerometer recordings were used to measure the vibrations of 7 vibration platforms. Four loads (0 kg, 45 kg, 68 kg, 91 kg) and 3 vibration frequencies were used (30 Hz, 40 Hz, 50 Hz), totaling 12 combinations. Results: In all platforms, vibration amplitude and peak acceleration varied as a function of the load used (p < 0.001 in all cases). In most platforms, the actual frequency of vibration differed from the intended frequency (actual/intended ratio ranging from 0.83 to 1.19), as a function of load and frequency. These results imply that subjects of different weights could be receiving different vibrations. Conclusion: Investigators should characterize and report the vibrations actually delivered in their studies, in order to increase the quality of evidence in whole body vibration studies.

Considerable demand exists for a device to facilitate hands-free, stable stance in individuals with neurological disorders such as spinal cord injury (SCI) and stroke. In this regard, applying functional electrical stimulation (FES) to muscles of the lower limbs in closed loop has shown promise. In particular, it has been suggested that a PID control strategy could offer functional benefits to stability by mimicking the neurological control strategy employed in able-bodied stance. In this proof of concept study, we tested this assertion by examining the potential of a PID control strategy with gravity compensation to effectively maintain balance during quiet stance by regulating FES-induced contractions of the ankle plantarflexors and dorsiflexors in able-bodied individuals. A novel Inverted Pendulum Standing Apparatus (IPSA) was employed to simulate quiet stance whilst minimizing the voluntary control of able-bodied subjects. Quiet and perturbed standing trials were performed in 3 able-bodied subjects. Performance metrics including those pertaining to stability during quiet stance (root mean square difference), perturbation rejection capabilities (settling time, peak deviation), and ability to transition from an offset initial position (settling time), were examined. For all 3 subjects and for all of the metrics examined, our results showed that the proposed closed-loop controlled FES system improved performance in comparison to voluntary control. These results indicate that the PID plus gravity control strategy used in this study offers meaningful benefits over voluntary control in terms of standing stability. Thus, the controller could potentially be applied to the problem of improving or restoring standing ability in some neurologic patient populations.

In this pilot study, we examined how effectively functional electrical stimulation (FES) and passive stepping mitigated orthostatic hypotension in participants with chronic spinal cord injury (SCI). While being tilted head-up to 70 (°) from the supine position, the participants underwent four 10-min conditions in a random sequence: 1) no intervention, 2) passive stepping, 3) isometric FES of leg muscles, and 4) FES of leg muscles combined with passive stepping. We found that FES and passive stepping independently mitigated a decrease in stroke volume and helped to maintain the mean blood pressure. The effects of FES on stroke volume and mean blood pressure were greater than those of passive stepping. When combined, FES and passive stepping did not interfere with each other, but they also did not synergistically increase stroke volume or mean blood pressure. Thus, the present study suggests that FES delivered to lower limbs can be used in individuals with SCI to help them withstand orthostatic stress. Additional studies are needed to confirm whether this use of FES is applicable to a larger population of individuals with SCI.