Using robot-applied resistance to augment body-weight-supported treadmill training in an individual with incomplete spinal cord injury

The Effectiveness of Overground Robot Exoskeleton Gait Training on Gait Outcomes, Balance, and Motor Function in Patients with Stroke: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

This study aimed to investigate the effects of overground robot exoskeleton gait training on gait outcomes, balance, and motor function in patients with stroke.

METHODS

Following the PRISMA guidelines, literature searches were performed in the PubMed, EMBASE, Cochrane Central Register of Controlled Trials, SCOPUS, Ovid-LWW, and RISS databases. A total of 504 articles were identified, of which 19 were included for analysis after application of the inclusion and exclusion criteria. The included literature was qualitatively evaluated using the PEDro scale, while the Egger's regression, funnel plot, and trim-and-fill methods were applied to assess and adjust for publication bias.

RESULTS

The averaged PEDro score was 6.21 points, indicating a high level of methodological quality. In the analysis based on dependent variables, higher effect sizes were observed in the following ascending order: gait speed (g = 0.26), motor function (g = 0.21), gait ability (g = 0.18), Timed Up and Go Test (g = -0.15), gait endurance (g = 0.11), and Berg Balance Scale (g = 0.05). Subgroup analyses further revealed significant differences in Asian populations (g = 0.26), sessions lasting longer than 30 min (g = 0.37), training frequency of three times per week or less (g = 0.38), and training duration of four weeks or less (g = 0.25). Overall, the results of this study indicate that overground robot exoskeleton gait training is effective at improving gait speed in patients with stroke, particularly when the sessions exceed 30 min, are conducted three times or less per week, and last for four weeks or less.

CONCLUSION

our results suggest that training is an effective intervention for patients with stroke, provided that appropriate goal-setting and intensity and overground robot exoskeleton gait are applied.

Exoskeletal wearable robot on ambulatory function in patients with stroke: a protocol for an international, multicentre, randomised controlled study

INTRODUCTION

The purpose of this study is to determine the effect of overground gait training using an exoskeletal wearable robot (exoskeleton) on the recovery of ambulatory function in patients with subacute stroke. We also investigate the assistive effects of an exoskeleton on ambulatory function in patients with subacute stroke.

METHODS AND ANALYSIS

This study is an international, multicentre, randomised controlled study at five institutions with a total of 150 patients with subacute stroke. Participants will be randomised into two groups (75 patients in the robot-assisted gait training (RAGT) group and 75 patients in the control group). The gait training will be performed with a total of 20 sessions (60 min/session); 5 sessions a week for 4 weeks. The RAGT group will receive 30 min of gait training using an exoskeleton (ANGEL LEGS M20, Angel Robotics) and 30 min of conventional gait training, while the control group will receive 60 min conventional gait training. In all the patients, the functional assessments such as ambulation, motor and balance will be evaluated before and after the intervention. Follow-up monitoring will be performed to verify whether the patient can walk without physical assistance for 3 months. The primary outcome is the improvement of the Functional Ambulatory Category after the gait training. The functional assessments will also be evaluated immediately after the last training session in the RAGT group to assess the assistive effects of an exoskeletal wearable robot. This trial will provide evidence on the effects of an exoskeleton to improve and assist ambulatory function in patients with subacute stroke.

ETHICS AND DISSEMINATION

This protocol has been approved by the Institutional Review Board of each hospital and conforms to the Declaration of Helsinki. The results will be disseminated through publication.

TRIAL REGISTRATION NUMBER

Protocol was registered at ClinicalTrials.gov (NCT05157347) on 15 December 2021 and CRIS (KCT0006815) on 19 November 2021.

Biomechanical differences between able-bodied and spinal cord injured individuals walking in an overground robotic exoskeleton

Background

Robotic assisted gait training (RAGT) uses a powered exoskeleton to support an individual’s body and move their limbs, with the aim of activating latent, pre-existing movement patterns stored in the lower spinal cord called central pattern generators (CPGs) to facilitate stepping. The parameters that directly stimulate the stepping CPGs (hip extension and ipsilateral foot unloading) should be targeted to maximise the rehabilitation benefits of these devices.

Aim

To compare the biomechanical profiles of individuals with a spinal cord injury (SCI) and able-bodied individuals inside the ReWalk^TM powered exoskeleton and to contrast the users’ profiles with the exoskeleton.

Methods

Eight able-bodied and four SCI individuals donned a ReWalk^TM and walked along a 12-meter walkway, using elbow crutches. Whole-body kinematics of the users and the ReWalk^TM were captured, along with GRF and temporal-spatial characteristics. Discreet kinematic values were analysed using a Kruskall-Wallis H and Dunn’s post-hoc analysis. Upper-body differences, GRF and temporal-spatial characteristics were analysed using a Mann-Whitney U test (P<0.05).

Results

Walking speed ranged from 0.32–0.39m/s. Hip abduction, peak knee flexion and ankle dorsiflexion for both the SCI and able-bodied groups presented with significant differences to the ReWalk^TM. The able-bodied group presented significant differences to the ReWalk^TM for all kinematic variables except frontal plane hip ROM (P = 0.093,δ = -0.56). Sagittal plane pelvic and trunk ROM were significantly greater in the SCI vs. able-bodied (P = 0.004,δ = -1; P = 0.008,δ = -0.94, respectively). Posterior braking force was significantly greater in the SCI group (P = 0.004, δ = -1).

Discussion

The different trunk movements used by the SCI group and the capacity for the users’ joint angles to exceed those of the device suggest that biomechanical profiles varied according to the user group. However, upright stepping with the ReWalk^TM device delivered the appropriate afferent stimulus to activate CPGs as there were no differences in key biomechanical parameters between the two user groups.

Viscous field training induces after effects but hinders recovery of overground locomotion following spinal cord injury in rats

Robotic-assisted gait training was able to improve the unassisted overground locomotion of rats following a cervical spinal cord injury. Specifically, four weeks of daily step training in the Robomedica Rodent Robotic Motor Performance System, where the device actively guided the hindlimbs through a pre-injury stepping pattern while the rats walked over a moving treadmill belt in a quadrupedal posture, was able to improve unassisted overground locomotion as measured by the CatWalk gait analysis device. Unfortunately the improvements were minimal. In fact, control animals that received only body weight supported treadmill training and no active robotic forces showed an even greater restoration of unassisted overground locomotion. This led us to further investigate the effects of the specific forces used in rehabilitative training. The robotic training device was modified to apply assistive (negative viscosity) or resistive (viscous) fields in lieu of the standard active guidance. Within the device, daily training with a viscous field resulted in small, constrained steps that were similar to pre-injury steps. However, when the robot was off for weekly assessments, the steps opened up and deviated away from pre-injury levels. Training in a negative viscosity field produced the opposite effect; large open steps that were unlike pre-injury during daily training, and constrained steps that were more like pre-injury during weekly assessment. These training induced after-effects washed out 2 weeks after the cessation of training. Additionally, these distinct after effects seen in the training device did not translate to distinct differences in the recovery of unassisted overground locomotion, with the body weight supported treadmill training controls showing the greatest recovery of overground locomotion. Still, the fact that different applied forces can induce different after effects has interesting implications for rehabilitative training - is it better to have healthy looking steps during training only to induce abnormal after effects, or have abnormal performance during training but with desirable after effects? The data presented here is the first step in addressing this question.

Robotic Rehabilitation in Spinal Cord Injury: A Pilot Study on End-Effectors and Neurophysiological Outcomes

Robot-aided gait training (RAGT) has been implemented to provide patients with spinal cord injury (SCI) with a physiological limb activation during gait, cognitive engagement, and an appropriate stimulation of peripheral receptors, which are essential to entrain neuroplasticity mechanisms supporting functional recovery. We aimed at assessing whether RAGT by means of an end-effector device equipped with body weight support could improve functional ambulation in patients with subacute, motor incomplete SCI. In this pilot study, 15 patients were provided with six RAGT sessions per week for eight consecutive weeks. The outcome measures were muscle strength, ambulation, going upstairs, and disease burden. Furthermore, we estimated the activation patterns of lower limb muscles during RAGT by means of surface electromyography and the resting state networks' functional connectivity (RSN-FC) before and after RAGT. Patients achieved a clinically significant improvement in the clinical outcome measures substantially up to six months post-treatment. These data were paralleled by an improvement in the stair-climbing cycle and a potentiating of frequency-specific and area-specific RSN-FC patterns. Therefore, RAGT, by means of an end-effector device equipped with body weight support, is promising in improving gait in patients with subacute, motor incomplete SCI, and it could produce additive benefit for the neuromuscular reeducation to gait in SCI when combined with conventional physiotherapy.

Acquisition of a precision walking skill and the impact of proprioceptive deficits in people with motor-incomplete spinal cord injury

Many people with motor-incomplete spinal cord injury (m-iSCI) experience difficulty navigating obstacles, such as curbs and stairs. The ability to relearn walking skills may be limited by proprioceptive deficits. The purpose of this study was to determine the capacity of participants to acquire a precision walking skill, and to evaluate the influence of proprioceptive deficits on the skill acquisition in individuals with m-iSCI. Sixteen individuals with m-iSCI and eight controls performed a precision walking task that required matching their foot height to a target during the swing phase. Proprioceptive deficits were quantified at the hip and knee for joint position and movement detection sense. Participants completed 600 steps of training with visual feedback. Pretraining and posttraining tests were conducted without visual feedback, along with a transfer test with an ankle weight. Posttraining and transfer tests were repeated 1 day later. Participants returned to the laboratory 1 wk later to repeat the training. Performance was calculated as the vertical distance between the target and actual foot height for each step. The posttraining and transfer performances were similar between groups. However, participants with m-iSCI had a slower rate of acquisition to achieve a similar performance level compared with controls. Acquisition rate and posttraining performance of the precision walking task were related to lower limb joint position sense among SCI participants. Although they can achieve a similar level of performance in a precision walking task, proprioceptive deficits impair the rate of learning among individuals with m-iSCI compared with able-bodied controls. NEW & NOTEWORTHY People with motor-incomplete spinal cord injuries are able to achieve the same level of performance accuracy on a precision walking task as able-bodied controls; however, the rate of learning is slower, indicating that more practice is required to stabilize performance. Our findings also show a relationship between impaired sensory function and reduced accuracy when performing a precision walking task after spinal cord injury.

A wearable resistive robot facilitates locomotor adaptations during gait

BACKGROUND

Robotic-resisted treadmill walking is a form of task-specific training that has been used to improve gait function in individuals with neurological injury, such as stroke, spinal cord injury, or cerebral palsy. Traditionally, these devices use active elements (e.g., motors or actuators) to provide resistance during walking, making them bulky, expensive, and less suitable for overground or in-home rehabilitation. We recently developed a low-cost, wearable robotic brace that generates resistive torques across the knee joint using a simple magnetic brake. However, the possible effects of training with this device on gait function in a clinical population are currently unknown.

OBJECTIVE

The purpose of this study was to test the acute effects of resisted walking with this device on kinematics, muscle activation patterns, and gait velocity in chronic stroke survivors.

METHODS

Six stroke survivors wore the resistive brace and walked on a treadmill for 20 minutes (4×5 minutes) at their self-selected walking speed while simultaneously performing a foot trajectory-tracking task to minimize stiff-knee gait. Electromyography, sagittal plane gait kinematics, and overground gait velocity were collected to evaluate the acute effects of the device on gait function.

RESULTS

Robotic-resisted treadmill training resulted in a significant increase in quadriceps and hamstring EMG activity during walking. Significant aftereffects (i.e., improved joint excursions) were also observed on the hip and knee kinematics, which persisted for several steps after training. More importantly, training resulted in significant improvements in overground gait velocity. These results were consistent in all the subjects tested.

CONCLUSION

This study provides preliminary evidence indicating that robotic-resisted treadmill walking using our knee brace can result in meaningful biomechanical aftereffects that translate to overground walking.

The effects of robot assisted gait training on temporal-spatial characteristics of people with spinal cord injuries: A systematic review

CONTEXT

Robotic assisted gait training (RAGT) technology can be used as a rehabilitation tool or as an assistive device for spinal cord injured (SCI) individuals. Its impact on upright stepping characteristics of SCI individuals using treadmill or overground robotic exoskeleton systems has yet to be established.

OBJECTIVE

To systematically review the literature and identify if overground or treadmill based RAGT use in SCI individuals elicited differences in temporal-spatial characteristics and functional outcome measures.

METHODS

A systematic search of the literature investigating overground and treadmill RAGT in SCIs was undertaken excluding case-studies and case-series. Studies were included if the primary outcomes were temporal-spatial gait parameters. Study inclusion and methodological quality were assessed and determined independently by two reviewers. Methodological quality was assessed using a validated scoring system for randomized and non-randomized trials.

RESULTS

Twelve studies met all inclusion criteria. Participant numbers ranged from 5-130 with injury levels from C2 to T12, American Spinal Injuries Association A-D. Three studies used overground RAGT systems and the remaining nine focused on treadmill based RAGT systems. Primary outcome measures were walking speed and walking distance. The use of treadmill or overground based RAGT did not result in an increase in walking speed beyond that of conventional gait training and no studies reviewed enabled a large enough improvement to facilitate community ambulation.

CONCLUSION

The use of RAGT in SCI individuals has the potential to benefit upright locomotion of SCI individuals. Its use should not replace other therapies but be incorporated into a multi-modality rehabilitation approach.

Robotic assisted gait as a tool for rehabilitation of individuals with spinal cord injury: a systematic review

BACKGROUND

Spinal cord injury (SCI) is characterized by a total or partial deficit of sensory and motor pathways. Impairments of this injury compromise muscle recruitment and motor planning, thus reducing functional capacity. SCI patients commonly present psychological, intestinal, urinary, osteomioarticular, tegumentary, cardiorespiratory and neural alterations that aggravate in chronic phase. One of the neurorehabilitation goals is the restoration of these abilities by favoring improvement in the quality of life and functional independence. Current literature highlights several benefits of robotic gait therapies in SCI individuals.

OBJECTIVES

The purpose of this study was to compare the robotic gait devices, and systematize the scientific evidences of these devices as a tool for rehabilitation of SCI individuals.

METHODS

A systematic review was carried out in which relevant articles were identified by searching the following databases: Cochrane Library, PubMed, PEDro and Capes Periodic. Two authors selected the articles which used a robotic device for rehabilitation of spinal cord injury.

RESULTS

Databases search found 2941 articles, 39 articles were included due to meet the inclusion criteria. The robotic devices presented distinct features, with increasing application in the last years. Studies have shown promising results regarding the reduction of pain perception and spasticity level; alteration of the proprioceptive capacity, sensitivity to temperature, vibration, pressure, reflex behavior, electrical activity at muscular and cortical level, classification of the injury level; increase in walking speed, step length and distance traveled; improvements in sitting posture, intestinal, cardiorespiratory, metabolic, tegmental and psychological functions.

CONCLUSIONS

This systematic review shows a significant progress encompassing robotic devices as an innovative and effective therapy for the rehabilitation of individuals with SCI.

Efficacy and safety of 9 nonoperative regimens for the treatment of spinal cord injury: A network meta-analysis

OBJECTIVE

This network meta-analysis aims to compare the efficacy and safety of 9 nonoperative regimens (placebo, pregabalin, GM-1 ganglioside, venlafaxine extended-release [venlafaxine XR], fampridine, conventional over-ground training [OT], body-weight-supported treadmill training [BWSTT], robotic-assisted gait training [RAGT] + OT and body-weight-supported over-ground training [BWSOT]) in treating spinal cord injury (SCI).

METHODS

Clinical controlled trials of 9 nonoperative regimens for SCI were retrieved in the electronic database. Traditional pairwise and Bayesian network meta-analyses were performed to compare the efficacy and safety of 9 nonoperative regimens for the treatment of SCI. Weighted mean difference (WMD), odds ratios (OR), and surface under the cumulative ranking curve (SUCRA) were calculated using the Markov Chain Monte Carlo engine Open BUGS (V.3.4.0) and R (V.3.2.1) package gemtc (V.0.6).

RESULTS

A total of 9 clinical controlled trials meeting the inclusion criteria were selected in this meta-analysis. On the aspect of efficacy, the results of pairwise meta-analysis indicated that the RAGT + OT and BWSOT might have the best efficacy in SCI patients in terms of a lower extremity motor score (LEMS) compared with conventional OT; the efficacy of RAGT + OT on SCI patients was relatively better than that of conventional OT in terms of walking index for spinal cord injury (WISCI). With the aspect of safety, the constipation rate of placebo on SCI patients was relatively higher than that of venlafaxine XR; however, with respect to headache and urinary tract infection, there was no significant difference in the safety of placebo, pregabalin, GM-1 ganglioside, venlafaxine XR, and fampridine on SCI patients. The results of SUCRA values suggested that BWSOT had the highest SUCRA value (75.25%) of LEMS; RAGT + OT had the highest SUCRA value (88.50%) of WISCI; venlafaxine XR had the highest SUCRA value (94.00%) of constipation; venlafaxine XR had the highest SUCRA value (80.00%) of headache; GM-1 ganglioside had the highest SUCRA value (87.75%) of urinary tract infection.

CONCLUSION

Our results provide evidence that the RAGT + OT and BWSOT might have the best efficacy in the treatment of SCI, and the venlafaxine XR and GM-1 ganglioside showed adequate safety for SCI.

Measuring balance confidence after spinal cord injury: the reliability and validity of the Activities-specific Balance Confidence Scale

CONTEXT/OBJECTIVE

The study objectives were to evaluate the test-retest reliability, convergent validity, and discriminative validity of the Activities-specific Balance Confidence (ABC) scale in individuals with incomplete spinal cord injury (iSCI).

DESIGN

Prospective, cross-sectional study.

SETTING

Laboratory.

PARTICIPANTS

Twenty-six community-dwelling individuals with chronic iSCI (20 males, 59.7 + 18.9 years old) and 26 age- and sex-matched able-bodied (AB) individuals participated.

INTERVENTIONS

None.

OUTCOME MEASURES

Measures of balance and gait were collected over two days. Clinical measures included the ABC scale, Mini-Balance Evaluation System's Test, 10-meter Walk Test, SCI Functional Ambulation Profile, manual muscle testing of lower extremity muscles, and measures of lower extremity proprioception and cutaneous pressure sensitivity. Biomechanical measures included the velocity and sway area of centre of pressure (COP) movement during quiet standing.

RESULTS

The ABC scale demonstrated high test-retest reliability (intraclass correlation coefficient = 0.93) among participants with iSCI. The minimal detectable change was 14.87%. ABC scale scores correlated with performance on all clinical measures (ρ=0.60-0.80, P<0.01), with the exception of proprioception and cutaneous pressure sensitivity (P=0.20-0.70), demonstrating convergent validity. ABC scale scores also correlated with overall COP velocity (ρ=-0.69, P<0.001) and COP velocity in the anterior-posterior direction (ρ=-0.71, P<0.001). Participants with iSCI scored significantly lower on the ABC scale than the AB participants (P<0.001), and the area under the receiver operating characteristic curve was 0.95, demonstrating discriminative validity.

CONCLUSION

The ABC scale is a reliable and valid measure of balance confidence in community-dwelling, ambulatory individuals with chronic iSCI.

Robot-Applied Resistance Augments the Effects of Body Weight-Supported Treadmill Training on Stepping and Synaptic Plasticity in a Rodent Model of Spinal Cord Injury

BACKGROUND

The application of resistive forces has been used during body weight-supported treadmill training (BWSTT) to improve walking function after spinal cord injury (SCI). Whether this form of training actually augments the effects of BWSTT is not yet known.

OBJECTIVE

To determine if robotic-applied resistance augments the effects of BWSTT using a controlled experimental design in a rodent model of SCI.

METHODS

Spinally contused rats were treadmill trained using robotic resistance against horizontal (n = 9) or vertical (n = 8) hind limb movements. Hind limb stepping was tested before and after 6 weeks of training. Two control groups, one receiving standard training (ie, without resistance; n = 9) and one untrained (n = 8), were also tested. At the terminal experiment, the spinal cords were prepared for immunohistochemical analysis of synaptophysin.

RESULTS

Six weeks of training with horizontal resistance increased step length, whereas training with vertical resistance enhanced step height and movement velocity. None of these changes occurred in the group that received standard (ie, no resistance) training or in the untrained group. Only standard training increased the number of step cycles and shortened cycle period toward normal values. Synaptophysin expression in the ventral horn was highest in rats trained with horizontal resistance and in untrained rats and was positively correlated with step length.

CONCLUSIONS

Adding robotic-applied resistance to BWSTT produced gains in locomotor function over BWSTT alone. The impact of resistive forces on spinal connections may depend on the nature of the resistive forces and the synaptic milieu that is present after SCI.

Variable Damping Force Tunnel for Gait Training Using ALEX III

Haptic feedback affects not only the quality of training but can also influence the physical design of robotic gait trainers by determining how much force needs to be applied to the user and the nature of the force. This paper presents the design of a variable damping force tunnel and explores the effect of the shape and strength of the damping field using ALEX III, a treadmill-based exoskeleton developed at Columbia University. The study consists of 32 healthy subjects who were trained for 40 minutes in the device. The subjects were trained to follow a footpath with a 50% increase in step height, so the foot would have 1.5 times the ground clearance. Subjects were assigned to one of four groups: linear high, linear low, parabolic high, and parabolic low. Linear or parabolic denotes the shape of the damping field, and high or low denotes the rate of change (strength) of the field based on error. It is shown that the new controller is capable of inducing gait adaptations in healthy individuals while walking in the device. All groups showed adaptations in step height, while only the high strength groups showed changes in normalized error area, a measure of how closely the desired path was followed.

Short-term cortical plasticity associated with feedback-error learning after locomotor training in a patient with incomplete spinal cord injury

BACKGROUND AND PURPOSE

For rehabilitation strategies to be effective, training should be based on principles of motor learning, such as feedback-error learning, that facilitate adaptive processes in the nervous system by inducing errors and recalibration of sensory and motor systems. This case report suggests that locomotor resistance training can enhance somatosensory and corticospinal excitability and modulate resting-state brain functional connectivity in a patient with motor-incomplete spinal cord injury (SCI).

CASE DESCRIPTION

The short-term cortical plasticity of a 31-year-old man who had sustained an incomplete SCI 9.5 years previously was explored in response to body-weight-supported treadmill training with velocity-dependent resistance applied with a robotic gait orthosis. The following neurophysiological and neuroimaging measures were recorded before and after training. Sensory evoked potentials were elicited by electrical stimulation of the tibial nerve and recorded from the somatosensory cortex. Motor evoked potentials were generated with transcranial magnetic stimulation applied over the tibialis anterior muscle representation in the primary motor cortex. Resting-state functional magnetic resonance imaging was performed to evaluate short-term changes in patterns of brain activity associated with locomotor training.

OUTCOMES

Somatosensory excitability and corticospinal excitability were observed to increase after locomotor resistance training. Motor evoked potentials increased (particularly at higher stimulation intensities), and seed-based resting-state functional magnetic resonance imaging analyses revealed increased functional connectivity strength in the motor cortex associated with the less affected side after training.

DISCUSSION

The observations suggest evidence of short-term cortical plasticity in 3 complementary neurophysiological measures after one session of locomotor resistance training. Future investigation in a sample of people with incomplete SCI will enhance the understanding of potential neural mechanisms underlying the behavioral response to locomotor resistance training.

Effect of robotic-assisted gait training in patients with incomplete spinal cord injury

Objective

To determine the effect of robotic-assisted gait training (RAGT) compared to conventional overground training.

Methods

Sixty patients with motor incomplete spinal cord injury (SCI) were included in a prospective, randomized clinical trial by comparing RAGT to conventional overground training. The RAGT group received RAGT three sessions per week at duration of 40 minutes with regular physiotherapy in 4 weeks. The conventional group underwent regular physiotherapy twice a day, 5 times a week. Main outcomes were lower extremity motor score of American Spinal Injury Association impairment scale (LEMS), ambulatory motor index (AMI), Spinal Cord Independence Measure III mobility section (SCIM3-M), and walking index for spinal cord injury version II (WISCI-II) scale.

Results

At the end of rehabilitation, both groups showed significant improvement in LEMS, AMI, SCIM3-M, and WISCI-II. Based on WISCI-II, statistically significant improvement was observed in the RAGT group. For the remaining variables, no difference was found.

Conclusion

RAGT combined with conventional physiotherapy could yield more improvement in ambulatory function than conventional therapy alone. RAGT should be considered as one additional tool to provide neuromuscular reeducation in patient with incomplete SCI.

Cardiopulmonary exercise testing early after stroke using feedback-controlled robotics-assisted treadmill exercise: test-retest reliability and repeatability

BACKGROUND

Exercise capacity is seriously reduced after stroke. While cardiopulmonary assessment and intervention strategies have been validated for the mildly and moderately impaired populations post-stroke, there is a lack of effective concepts for stroke survivors suffering from severe motor limitations. This study investigated the test-retest reliability and repeatability of cardiopulmonary exercise testing (CPET) using feedback-controlled robotics-assisted treadmill exercise (FC-RATE) in severely motor impaired individuals early after stroke.

METHODS

20 subjects (age 44-84 years, <6 month post-stroke) with severe motor limitations (Functional Ambulatory Classification 0-2) were selected for consecutive constant load testing (CLT) and incremental exercise testing (IET) within a powered exoskeleton, synchronised with a treadmill and a body weight support system. A manual human-in-the-loop feedback system was used to guide individual work rate levels. Outcome variables focussed on standard cardiopulmonary performance parameters. Relative and absolute test-retest reliability were assessed by intraclass correlation coefficients (ICC), standard error of the measurement (SEM), and minimal detectable change (MDC). Mean difference, limits of agreement, and coefficient of variation (CoV) were estimated to assess repeatability.

RESULTS

Peak performance parameters during IET yielded good to excellent relative reliability: absolute peak oxygen uptake (ICC =0.82), relative peak oxygen uptake (ICC =0.72), peak work rate (ICC =0.91), peak heart rate (ICC =0.80), absolute gas exchange threshold (ICC =0.91), relative gas exchange threshold (ICC =0.88), oxygen cost of work (ICC =0.87), oxygen pulse at peak oxygen uptake (ICC =0.92), ventilation rate versus carbon dioxide output slope (ICC =0.78). For these variables, SEM was 4-13%, MDC 12-36%, and CoV 0.10-0.36. CLT revealed high mean differences and insufficient test-retest reliability for all variables studied.

CONCLUSIONS

This study presents first evidence on reliability and repeatability for CPET in severely motor impaired individuals early after stroke using a feedback-controlled robotics-assisted treadmill. The results demonstrate good to excellent test-retest reliability and appropriate repeatability for the most important peak cardiopulmonary performance parameters. These findings have important implications for the design and implementation of cardiovascular exercise interventions in severely impaired populations. Future research needs to develop advanced control strategies to enable the true limit of functional exercise capacity to be reached and to further assess test-retest reliability and repeatability in larger samples.

Modifications in ankle dorsiflexor activation by applying a torque perturbation during walking in persons post-stroke: a case series

Background

Results obtained in a previous study (Gait Posture 34:358–363, 2011) have shown that, in non-disabled participants, a specific increase in ankle dorsiflexor (Tibialis anterior [TA]) activation can be induced by walking with a torque perturbation that plantarflexes the ankle during the swing phase. After perturbation removal, the increased TA activation persisted temporarily and was associated with a more dorsiflexed ankle during swing. The objective of the present case-series study was to verify if these results can be reproduced in persons post-stroke.

Methods

Six participants who sustained a stroke walked on a treadmill before, during and after exposure to a torque perturbation applied at the ankle by a robotized ankle-foot orthosis. Spatiotemporal gait parameters, ankle and knee kinematics, and the electromyographic activity of TA and Soleus were recorded. Mean amplitude of the TA burst located around toe off and peak ankle dorsiflexion angle during swing were compared across the 3 walking periods for each participant.

Results

At the end of the walking period with the perturbation, TA mean amplitude was significantly increased in 4 of the 6 participants. Among these 4 participants, modifications in TA activation persisted after perturbation removal in 3 of them, and led to a statistically significant increase in peak dorsiflexion during swing.

Clinical implications

This approach may be helpful to evaluate the residual adaptive capacity in the ankle dorsiflexors after a stroke and guide decision-making for the selection of optimal rehabilitation interventions. Future work will investigate the clinical impact of a multiple-session gait training based on this approach in persons presenting a reduced ankle dorsiflexion during the swing phase of walking.

Effect of robotic performance-based error-augmentation versus error-reduction training on the gait of healthy individuals

Effective locomotion training with robotic exoskeletons requires identification of optimal control algorithms to better facilitate motor learning. Two commonly employed training protocols emphasize use of training stimuli that either augment or reduce performance errors. The current study sought to identify which of these training strategies promote better short-term modification of a typical gait pattern in healthy individuals as a framework for future application to neurologically impaired individuals. Ten subjects were assigned to each of a performance-based error-augmentation or error-reduction training group. All subjects completed a 45-min session of treadmill walking at their preferred speed with a robotic exoskeleton. Target templates prescribed an ankle path for training that corresponded to an increased step height. When subjects' instantaneous ankle positions fell below the inferior virtual wall of the target ankle path, robotic forces were applied that either decreased (error-reduction) or increased (error-augmentation) the deviation from the target path. When the force field was turned on, both groups walked with ankle paths better approximating the target template compared to baseline. When the force field was removed unexpectedly during catch and post-training trials, only the error-augmentation group maintained an ankle path close to the target ankle path. Further investigation is required to determine if a similar training advantage is provided for neurologically impaired individuals.

Contributions to enhanced activity in rectus femoris in response to Lokomat-applied resistance

The application of resistance during the swing phase of locomotion is a viable approach to enhance activity in the rectus femoris (RF) in patients with neurological damage. Increased muscle activity is also accompanied by changes in joint angle and stride frequency, consequently influencing joint angular velocity, making it difficult to attribute neuromuscular changes in RF to resistance. Thus, the purpose of this study was to evaluate the effects of resistance on RF activity while constraining joint trajectories. Participants walked in three resistance conditions; 0 % (no resistance), 5 and 10 % of their maximum voluntary contraction (MVC). Visual and auditory biofeedback was provided to help participants maintain the same knee joint angle and stride frequency as during baseline walking. Lower limb joint trajectories and RF activity were recorded. Increasing the resistance, while keeping joint trajectories constant with biofeedback, independently enhanced swing phase RF activity. Therefore, the observed effects in RF are related to resistance, independent of any changes in joint angle. Considering resistance also affects stride frequency, a second experiment was conducted to evaluate the independent effects of resistance and stride frequency on RF activity. Participants walked in four combinations of resistance at 0 and 10 %MVC and natural and slow stride frequency conditions. We observed significant increases in RF activity with increased resistance and decreased stride frequency, confirming the independent contribution of resistance on RF activity as well as the independent effect of stride frequency. Resistance and stride frequency may be key parameters in gait rehabilitation strategies where either of these may be manipulated to enhance swing phase flexor muscle activity in order to maximize rehabilitation outcomes.

Locomotor training: as a treatment of spinal cord injury and in the progression of neurologic rehabilitation

Scientists, clinicians, administrators, individuals with spinal cord injury (SCI), and caregivers seek a common goal: to improve the outlook and general expectations of the adults and children living with neurologic injury. Important strides have already been accomplished; in fact, some have labeled the changes in neurologic rehabilitation a "paradigm shift." Not only do we recognize the potential of the damaged nervous system, but we also see that "recovery" can and should be valued and defined broadly. Quality-of-life measures and the individual's sense of accomplishment and well-being are now considered important factors. The ongoing challenge from research to clinical translation is the fine line between scientific uncertainty (ie, the tenet that nothing is ever proven) and the necessary burden of proof required by the clinical community. We review the current state of a specific SCI rehabilitation intervention (locomotor training), which has been shown to be efficacious although thoroughly debated, and summarize the findings from a multicenter collaboration, the Christopher and Dana Reeve Foundation's NeuroRecovery Network.

Training to achieve over ground walking after spinal cord injury: a review of who, what, when, and how

OBJECTIVES

(1) To provide clinicians with the best evidence for effective retraining of walking after spinal cord injury (SCI) to achieve over ground walking. (2) To identify gaps in our knowledge to guide future research.

METHODS

Articles that addressed the retraining of walking in adults with SCI and reported outcome measures of over ground walking ability were identified through a non-systematic search of the PubMed, Scopus, and CINAHL databases. No restriction was applied to the method of training. Selected articles were appraised using the Physiotherapy Evidence Database scale. Information was synthesized to answer who best responds to what type of treatment, how that treatment should be delivered, and at what stage after injury.

RESULTS

Individuals with motor incomplete SCI (American Spinal Injury Association (ASIA) Impairment scale (AIS) C and D) are most likely to regain walking over ground. The effective methods of training all involved a substantial component of walking in the training, and if assistance was provided, partial assistance was more effective than total assistance. Walking training resulted in a change in over ground walking speed of 0.06-0.77 m/s, and 6 minute walk distance of 24-357 m. The effective training schedules ranged from 10 to 130 sessions, with a density of sessions ranging from 2 per week to 5 per week. Earlier training led to superior results both in the subacute (<6 months) and chronic phases (>6 months) after injury, but even individuals with chronic injuries of long duration can improve.

CONCLUSIONS

Frequent, early treatment for individuals with motor incomplete SCI using walking as the active ingredient whether on the treadmill or over ground, generally leads to improved walking over ground. Much work remains for the future, including better quantification of treatment intensity, better outcome measures to quantify a broader range of walking skills, and better ways to retrain individuals with more severe lesions (AIS A and B).

Effects of repeated walking in a perturbing environment: a 4-day locomotor learning study

Previous studies have shown that when subjects repeatedly walk in a perturbing environment, initial movement error becomes smaller, suggesting that retention of the adapted locomotor program occurred (learning). It has been proposed that the newly learned locomotor program may be stored separately from the baseline program. However, how locomotor performance evolves with repeated sessions of walking with the perturbation is not yet known. To address this question, 10 healthy subjects walked on a treadmill on 4 consecutive days. Each day, locomotor performance was measured using kinematics and surface electromyography (EMGs), before, during, and after exposure to a perturbation, produced by an elastic tubing that pulled the foot forward and up during swing, inducing a foot velocity error in the first strides. Initial movement error decreased significantly between days 1 and 2 and then remained stable. Associated changes in medial hamstring EMG activity stabilized only on day 3, however. Aftereffects were present after perturbation removal, suggesting that daily adaptation involved central command recalibration of the baseline program. Aftereffects gradually decreased across days but were still visible on day 4. Separation between the newly learned and baseline programs may take longer than suggested by the daily improvement in initial performance in the perturbing environment or may never be complete. These results therefore suggest that reaching optimal performance in a perturbing environment should not be used as the main indicator of a completed learning process, as central reorganization of the motor commands continues days after initial performance has stabilized.

Walking while resisting a perturbation: Effects on ankle dorsiflexor activation during swing and potential for rehabilitation

Motor control studies have shown that when walking is performed while resisting a perturbation applied to the lower limb, the muscle activation pattern can be temporarily modified. The objective of the present study is to validate if such an approach, targeting the ankle, could specifically promote an increased activation of the ankle dorsiflexor muscles that are of key importance for the rehabilitation of foot drop.

METHODS

12 adults, with no gait deficit, walked on a treadmill for three periods of 5min: before, during and after exposure to a torque perturbation applied by a robotized ankle-foot orthosis that tended to plantarflex the ankle during the swing phase. Spatiotemporal gait parameters, ankle and knee kinematics, and the electromyographic activity of five lower limb muscle groups were recorded.

RESULTS

The perturbation initially caused a deviation of the ankle towards plantarflexion. This movement error was rapidly reduced and associated with a large increase (78.2%; p<0.001) in tibialis anterior (ankle dorsiflexor; TA) activation, specifically in the stance-to-swing burst. This increase carried over to post-perturbation walking, gradually disappearing over several strides. Interestingly, these aftereffects led to an increase in peak ankle dorsiflexion of approximately 7° during the swing phase.

CONCLUSIONS

Walking while resisting a torque perturbation applied at the ankle during swing promotes an increase in TA muscle activation that carries over after perturbation removal, leading to an increased ankle dorsiflexion. Training based on this approach may have the potential of improving the gait of persons with foot drop.