Locomotor Rehabilitation Research Articles

A new integrative approach to evaluate pathological gait: locomotor rehabilitation index

This article reviews the concept of locomotor rehabilitation index (LRI) from the principle of dynamical similarities and the theory of mechanism minimizing the energy expenditure in pathological walking. This index is defined as the percentage ratio between self-selected speed and optimum speed (algebraically LRI = 100 × self-selected speed/optimum walking speed). First, we analyze the mechanical foundations of human walking especially focusing on general size effects. Then, we discuss the descriptive physiology of pendular mechanism, evidencing the path that leads to the view of reductionist and extremely descriptive view of pathological gait. Integrative models, generated by the first evidence presented in our previous papers around the LRI, represent a crucial change of perspective. This model is discussed in details and criticized concerning the ensuing experimental findings. Finally, we discuss the case of Parkinson's disease using the Nordic walking as a neat example of application of LRI on pathological locomotion. To conclude , the concept of LRI is reinforced by the substantial evidence, showing that this new proposal for assessing the gait functionality is extremely promising and should be stimulated in studies that examine the effects of therapies on gait functionality in degenerative diseases.

Scale-Dependent Signal Identification in Low-Dimensional Subspace: Motor Imagery Task Classification.

Motor imagery electroencephalography (EEG) has been successfully used in locomotor rehabilitation programs. While the noise-assisted multivariate empirical mode decomposition (NA-MEMD) algorithm has been utilized to extract task-specific frequency bands from all channels in the same scale as the intrinsic mode functions (IMFs), identifying and extracting the specific IMFs that contain significant information remain difficult. In this paper, a novel method has been developed to identify the information-bearing components in a low-dimensional subspace without prior knowledge. Our method trains a Gaussian mixture model (GMM) of the composite data, which is comprised of the IMFs from both the original signal and noise, by employing kernel spectral regression to reduce the dimension of the composite data. The informative IMFs are then discriminated using a GMM clustering algorithm, the common spatial pattern (CSP) approach is exploited to extract the task-related features from the reconstructed signals, and a support vector machine (SVM) is applied to the extracted features to recognize the classes of EEG signals during different motor imagery tasks. The effectiveness of the proposed method has been verified by both computer simulations and motor imagery EEG datasets.

Locomotor Adaptability Task Promotes Intense and Task-Appropriate Output From the Paretic Leg During Walking

ObjectiveTo test the hypothesis that participants with stroke will exhibit appropriate increase in muscle activation of the paretic leg when taking a long step with the nonparetic leg compared to during steady-state walking, with a consequent increase in biomechanical output and symmetry during the stance phase of the modified gait cycle. DesignSingle-session observational study. SettingClinical research center in an outpatient hospital setting. ParticipantsAdults with chronic poststroke hemiparesis (N=15). InterventionsParticipants walked on an instrumented treadmill while kinetic, kinematic, and electromyogram data were recorded. Participants performed steady-state walking and a separate trial of the long-step adaptability task in which they were instructed to intermittently take a longer step with the nonparetic leg. Main Outcome MeasuresForward progression, propulsive force, and neuromuscular activation during walking. ResultsParticipants performed the adaptability task successfully and demonstrated greater neuromuscular activation in appropriate paretic leg muscles, particularly increased activity in paretic plantarflexor muscles. Propulsion and forward progression by the paretic leg were also increased. ConclusionsThese findings support the assertion that the nonparetic long-step task may be effective for use in poststroke locomotor rehabilitation to engage the paretic leg and promote recovery of walking.

Identifying stride-to-stride control strategies in human treadmill walking.

Variability is ubiquitous in human movement, arising from internal and external noise, inherent biological redundancy, and from the neurophysiological control actions that help regulate movement fluctuations. Increased walking variability can lead to increased energetic cost and/or increased fall risk. Conversely, biological noise may be beneficial, even necessary, to enhance motor performance. Indeed, encouraging more variability actually facilitates greater improvements in some forms of locomotor rehabilitation. Thus, it is critical to identify the fundamental principles humans use to regulate stride-to-stride fluctuations in walking. This study sought to determine how humans regulate stride-to-stride fluctuations in stepping movements during treadmill walking. We developed computational models based on pre-defined goal functions to compare if subjects, from each stride to the next, tried to maintain the same speed as the treadmill, or instead stay in the same position on the treadmill. Both strategies predicted average behaviors empirically indistinguishable from each other and from that of humans. These strategies, however, predicted very different stride-to-stride fluctuation dynamics. Comparisons to experimental data showed that human stepping movements were generally well-predicted by the speed-control model, but not by the position-control model. Human subjects also exhibited no indications they corrected deviations in absolute position only intermittently: i.e., closer to the boundaries of the treadmill. Thus, humans clearly do not adopt a control strategy whose primary goal is to maintain some constant absolute position on the treadmill. Instead, humans appear to regulate their stepping movements in a way most consistent with a strategy whose primary goal is to try to maintain the same speed as the treadmill at each consecutive stride. These findings have important implications both for understanding how biological systems regulate walking in general and for being able to harness these mechanisms to develop more effective rehabilitation interventions to improve locomotor performance.

Training conditions that best reproduce the joint powers of unsupported walking

ObjectiveTo identify the clinically relevant combinations of body weight support and speed that best reproduce the joint powers of unsupported walking. MethodsTiming and magnitude of lower extremity joint powers were calculated for 8 neurologically intact volunteers (4M/4F) walking with 0%, 30% and 50% body weight support at three speeds (slow, comfortable, and fast). Lower extremity joint power absorption was analyzed during weight acceptance and forward propulsion. In addition, power generation was analyzed during forward propulsion. Timings and magnitudes of joint powers per condition were evaluated to identify the training combinations of body weight support and speed that best preserved the powers of unsupported walking at slow, comfortable and fast speeds. ResultsFor all speeds examined, increasing body weight support to 30% without changing speed provided the best match. In general, changes in speed disrupted the joint power magnitudes and timings more than application of body weight support. Increasing body weight support when faster training speeds were used proved a viable method for reproducing the joint powers of slow, unsupported walking. ConclusionsThese data provide a reference for understanding the effect of potential training conditions on power absorption and generation within the lower extremity joints during walking. It is possible to reproduce the joint powers of unsupported walking with certain combinations of body weight support and speed. We recommend applying adequate levels of BWS when training speeds are faster than the overground speed goal, as occurs during treadmill-based locomotor rehabilitation of individuals with incomplete spinal cord injury.

Effect of Rhythmic Auditory Stimulation on Hemiplegic Gait Patterns.

PurposeThe purpose of our study was to investigate the effect of gait training with rhythmic auditory stimulation (RAS) on both kinematic and temporospatial gait patterns in patients with hemiplegia.Materials and MethodsEighteen hemiplegic patients diagnosed with either cerebral palsy or stroke participated in this study. All participants underwent the 4-week gait training with RAS. The treatment was performed for 30 minutes per each session, three sessions per week. RAS was provided with rhythmic beats using a chord progression on a keyboard. Kinematic and temporospatial data were collected and analyzed using a three-dimensional motion analysis system.ResultsGait training with RAS significantly improved both proximal and distal joint kinematic patterns in hip adduction, knee flexion, and ankle plantar flexion, enhancing the gait deviation index (GDI) as well as ameliorating temporal asymmetry of the stance and swing phases in patients with hemiplegia. Stroke patients with previous walking experience demonstrated significant kinematic improvement in knee flexion in mid-swing and ankle dorsiflexion in terminal stance. Among stroke patients, subacute patients showed a significantly increased GDI score compared with chronic patients. In addition, household ambulators showed a significant effect on reducing anterior tilt of the pelvis with an enhanced GDI score, while community ambulators significantly increased knee flexion in mid-swing phase and ankle dorsiflexion in terminal stance phase.ConclusionGait training with RAS has beneficial effects on both kinematic and temporospatial patterns in patients with hemiplegia, providing not only clinical implications of locomotor rehabilitation with goal-oriented external feedback using RAS but also differential effects according to ambulatory function.

Feasibility of lower-limb muscle power training to enhance locomotor function poststroke.

Poststroke motor control is characterized by greatly reduced muscle power generation. To date, the extent to which muscle power limits walking performance or whether its remediation should be a primary component of locomotor rehabilitation has yet to be established. The purpose of this study was to examine the feasibility and the effects of Poststroke Optimization of Walking using Explosive Resistance training, an intervention aimed at improving poststroke muscular and locomotor function. Twelve subjects (6-60 mo poststroke) participated in 24 training sessions (3 sessions/wk for 8 wk). Exercises included leg press, calf raises, and jump training, all performed at high concentric velocity, as well as trials of fast walking. We measured self-selected and fastest comfortable walking speeds as well as knee extensor and plantar flexor strength and power at pretraining, posttraining, and 8 wk follow-up time points. In addition, we also performed a number of clinical assessments commonly used in poststroke rehabilitation trials. Following training, significant improvements in lower-limb muscle strength and power were realized and accompanied by improvements in self-selected as well as fastest comfortable walking speeds. No changes in clinical assessments resulted from training.

Understanding Spatial and Temporal Gait Asymmetries in Individuals Post Stroke

Gait asymmetry in spatial and temporal parameters and its impacts on functional activities have always raised many interesting questions in research and rehabilitation. The aim of this topical review is threefold: 1) to examine different equations of asymmetry of gait parameters and make recommendations for standardization, 2) to deepen the understanding of the relationships between sensorimotor deficits, spatiotemporal (step length, swing time and double support time) and biomechanical (kinematic, kinetic, muscular activity) parameter asymmetries during gait and, 3) to summarize the impacts of gait asymmetry on walking speed, falls, and energy cost in individuals post stroke. In light of current literature, we recommend quantifying spatiotemporal asymmetries by calculating symmetry ratios. However, for other gait parameters (such as kinetic or kinematic data), the choice will depend on the variability of the data and the objective of the study. Regardless of the selected asymmetry equation, we recommend presenting the asymmetry values in combination with the mean value of each side to facilitate comparisons between studies. This review also revealed that sensorimotor deficits clinically measured are not sufficient to explain the large variability of spatiotemporal asymmetries (particularly for step length and double support time) in individuals post stroke. Biomechanical analysis has been identified as a relevant approach to understanding gait deviations. Studies that linked biomechanical impairments to spatiotemporal asymmetries suggest that a balance issue and an impaired paretic forward propulsion could be among the important factors underlying spatiotemporal asymmetries. In our opinion, this paper provides meaningful information to aid in better understanding gait deviations in persons after stroke and establishes the need for future studies regrouping individuals post stroke according to their spatiotemporal asymmetries. Furthermore, further studies targeting efficacy of locomotor rehabilitation and the impacts of gait asymmetry on risk of falls and energy expenditure are needed.

Hypoxic locomotor rehabilitation for incomplete spinal cord injury

Neurorehabilitation is experiencing a paradigm shift toward treatments that are both effective and efficient, driven by increasing demands upon clinical practice and the staggering burden of health care expenditures. The impetus is toward finding ways to maximize the potential for recovery by targeting networks spared by the lesion. Residual networks can undergo reorganization with recovery, involving plasticity or improved efficiency at the level of preexisting synapses and sprouting from surviving fibers for creation of new circuits.1 Capitalizing on the potential for plasticity and employing methods that can augment this potential are the 2 driving themes in current rehabilitation research. In this issue of Neurology® , Hayes et al.2 present a study that sought to address both.

Navigated transcranial magnetic stimulation as a method of early locomotor rehabilitation after stroke

The objective of the present study was to compare the safety and effectiveness of navigated and non-navigated rhythmic transcranial magnetic stimulation rTMS in the patients presenting with post-stroke hemiparesis. Methods: Group 1 consisted of 31 patients with post-stroke hemiparesis treated by navigated rTMS. Thirty comparable patients treated without navigation were included in Group 2. The patients were examined 3.2±1.1 month after stroke. Their mean age was 42±10.1 years. The average NIHSS score declined from 15.9±3.5 to 10.2±3.9 in Group 1 and from 15.8±3.0 to 13.1±3.4 in Group 2 (p=0.05). The Barthel index characterizing the degree of functional independence increased from 14.5±4.4 to 25.7±6.8 in Group 1 and from 14.3±4.2 to 18.1±5.9 in Group 2 (p=0.07). Navigated rTMS should be preferred as a method for locomotor rehabilitation after stroke.

Gradual training reduces practice difficulty while preserving motor learning of a novel locomotor task

Motor learning strategies that increase practice difficulty and the size of movement errors are thought to facilitate motor learning. In contrast to this, gradual training minimizes movement errors and reduces practice difficulty by incrementally introducing task requirements, yet remains as effective as sudden training and its large movement errors for learning novel reaching tasks. While attractive as a locomotor rehabilitation strategy, it remains unknown whether the efficacy of gradual training extends to learning locomotor tasks and their unique requirements. The influence of gradual vs. sudden training on learning a locomotor task, asymmetric split belt treadmill walking, was examined by assessing whole body sagittal plane kinematics during 24hour retention and transfer performance following either gradual or sudden training. Despite less difficult and less specific practice for the gradual cohort on day 1, gradual training resulted in equivalent motor learning of the novel locomotor task as sudden training when assessed by retention and transfer a day later. This suggests that large movement errors and increased practice difficulty may not be necessary for learning novel locomotor tasks. Further, gradual training may present a viable locomotor rehabilitation strategy avoiding large movement errors that could limit or impair improvements in locomotor performance.

The influence of locomotor rehabilitation on module quality and post-stroke hemiparetic walking performance

Recent studies have suggested the biomechanical subtasks of walking can be produced by a reduced set of co-excited muscles or modules. Individuals post-stroke often exhibit poor inter-muscular coordination characterized by poor timing and merging of modules that are normally independent in healthy individuals. However, whether locomotor therapy can influence module composition and timing and whether these improvements lead to improved walking performance is unclear. The goal of this study was to examine the influence of a locomotor rehabilitation therapy on module composition and timing and post-stroke hemiparetic walking performance.Twenty-seven post-stroke hemiparetic subjects participated in a 12-week locomotor intervention incorporating treadmill training with body weight support and manual trainers accompanied by training overground walking. Electromyography (EMG), kinematic and ground reaction force data were collected from subjects both pre- and post-therapy and from 19 age-matched healthy controls walking on an instrumented treadmill at their self-selected speed. Non-negative matrix factorization was used to identify the module composition and timing from the EMG data. Module timing and composition, and various measures of walking performance were compared pre- and post-therapy.In subjects with four modules pre- and post-therapy, locomotor training resulted in improved timing of the ankle plantarflexor module and a more extended paretic leg angle that allowed the subjects to walk faster and with more symmetrical propulsion. In addition, subjects with three modules pre-therapy increased their number of modules and improved walking performance post-therapy. Thus, locomotor training has the potential to influence module composition and timing, which can lead to improvements walking performance.

Persons with Parkinson’s disease exhibit decreased neuromuscular complexity during gait

ObjectiveIndividual muscle activation patterns may be controlled by motor modules constructed by the central nervous system to simplify motor control. This study compared modular control of gait between persons with Parkinson’s disease (PD) and neurologically-healthy older adults (HOA) and investigated relationships between modular organization and gait parameters in persons with PD. MethodsFifteen persons with idiopathic PD and fourteen HOA participated. Electromyographic recordings were made from eight leg muscles bilaterally while participants walked at their preferred walking speed for 10min on an instrumented treadmill. Non-negative matrix factorization techniques decomposed the electromyographic signals, identifying the number and nature of modules accounting for 95% of variability in muscle activations during treadmill walking. ResultsGenerally, fewer modules were required to reconstruct muscle activation patterns during treadmill walking in PD compared to HOA (p<.05). Control of knee flexor and ankle plantar flexor musculature was simplified in PD. Activation timing was altered in PD while muscle weightings were unaffected. Simplified neuromuscular control was related to decreased walking speed in PD. ConclusionNeuromuscular control of gait is simplified in PD and may contribute to gait deficits in this population. SignificanceFuture studies of locomotor rehabilitation in PD should consider neuromuscular complexity to maximize intervention effectiveness.

Dynamic primitives in the control of locomotion

Humans achieve locomotor dexterity that far exceeds the capability of modern robots, yet this is achieved despite slower actuators, imprecise sensors, and vastly slower communication. We propose that this spectacular performance arises from encoding motor commands in terms of dynamic primitives. We propose three primitives as a foundation for a comprehensive theoretical framework that can embrace a wide range of upper- and lower-limb behaviors. Building on previous work that suggested discrete and rhythmic movements as elementary dynamic behaviors, we define submovements and oscillations: as discrete movements cannot be combined with sufficient flexibility, we argue that suitably-defined submovements are primitives. As the term “rhythmic” may be ambiguous, we define oscillations as the corresponding class of primitives. We further propose mechanical impedances as a third class of dynamic primitives, necessary for interaction with the physical environment. Combination of these three classes of primitive requires care. One approach is through a generalized equivalent network: a virtual trajectory composed of simultaneous and/or sequential submovements and/or oscillations that interacts with mechanical impedances to produce observable forces and motions. Reliable experimental identification of these dynamic primitives presents challenges: identification of mechanical impedances is exquisitely sensitive to assumptions about their dynamic structure; identification of submovements and oscillations is sensitive to their assumed form and to details of the algorithm used to extract them. Some methods to address these challenges are presented. Some implications of this theoretical framework for locomotor rehabilitation are considered.

Locomotor Rehabilitation of Individuals With Chronic Stroke: Difference Between Responders and Nonresponders

ObjectivesTo identify the clinical measures associated with improved walking speed after locomotor rehabilitation in individuals poststroke and how those who respond with clinically meaningful changes in walking speed differ from those with smaller speed increases. DesignA single group pre-post intervention study. Participants were stratified on the basis of a walking speed change of greater than (responders) or less than (nonresponders) .16m/s. Paired sample t tests were run to assess changes in each group, and correlations were run between the change in each variable and change in walking speed. SettingOutpatient interdisciplinary rehabilitation research center. ParticipantsHemiparetic subjects (N=27) (17 left hemiparesis; 19 men; age: 58.74±12.97y; 22.70±16.38mo poststroke). InterventionA 12-week locomotor intervention incorporating training on a treadmill with body weight support and manual trainers accompanied by training overground walking. Main Outcome MeasuresMeasures of motor control, balance, functional walking ability, and endurance were collected at pre- and postintervention assessments. ResultsEighteen responders and 9 nonresponders differed by age (responders=63.6y, nonresponders=49.0y, P=.001) and the lower extremity Fugl-Meyer Assessment score (responders=24.7, nonresponders=19.9, P=.003). Responders demonstrated an average improvement of .27m/s in walking speed as well as significant gains in all variables except daily step activity and paretic step ratio. Conversely, nonresponders demonstrated statistically significant improvements only in walking speed and endurance. However, the walking speed increase of .10m/s was not clinically meaningful. Change in walking speed was negatively correlated with changes in motor control in the nonresponder group, implying that walking speed gains may have been accomplished via compensatory mechanisms. ConclusionsThis study is a step toward discerning the underlying factors contributing to improved walking performance.

Coapplication of noisy patterned electrical stimuli and NMDA plus serotonin facilitates fictive locomotion in the rat spinal cord

A new stimulating protocol [fictive locomotion-induced stimulation (FListim)], consisting of intrinsically variable weak waveforms applied to a single dorsal root is very effective (though not optimal as it eventually wanes away) in activating the locomotor program of the isolated rat spinal cord. The present study explored whether combination of FListim with low doses of pharmacological agents that raise network excitability might further improve the functional outcome, using this in vitro model. FListim was applied together with N-methyl-d-aspartate (NMDA) + serotonin, while fictive locomotion (FL) was electrophysiologically recorded from lumbar ventral roots. Superimposing FListim on FL evoked by these neurochemicals persistently accelerated locomotor-like cycles to a set periodicity and modulated cycle amplitude depending on FListim rate. Trains of stereotyped rectangular pulses failed to replicate this phenomenon. The GABA(B) agonist baclofen dose dependently inhibited, in a reversible fashion, FL evoked by either FListim or square pulses. Sustained episodes of FL emerged when FListim was delivered, at an intensity subthreshold for FL, in conjunction with subthreshold pharmacological stimulation. Such an effect was, however, not found when high potassium solution instead of NMDA + serotonin was used. These results suggest that the combined action of subthreshold FListim (e.g., via epidural stimulation) and neurochemicals should be tested in vivo to improve locomotor rehabilitation after injury. In fact, reactivation of spinal locomotor circuits by conventional electrical stimulation of afferent fibers is difficult, while pharmacological activation of spinal networks is clinically impracticable due to concurrent unwanted effects. We speculate that associating subthreshold chemical and electrical inputs might decrease side effects when attempting to evoke human locomotor patterns.

Spinal and cortical activity-dependent plasticity following learning of complex arm movements in humans

Activity-dependent plasticity is a fundamental requirement for human motor learning, which takes place at several stages of the motor system and involves various mechanisms in neuronal circuitry. Here, we investigate parameters of cortical and spinal excitability before and immediately after a single session of locomotion-like arm training (LMT) or sequential visuo-motor learning (VMT). Both training paradigms focused especially on mainly activating the flexor carpi radialis muscle (FCR). The activity-dependent change in the excitability of FCR-associated neurons was investigated using standard transcranial magnetic stimulation, including analysis of motor-evoked potentials (MEP) amplitude, short-interval intracortical inhibition and intracortical facilitation (ICF). Furthermore, spinal plasticity was also assessed by means of homosynaptic FCR H-reflex depression (HD). LMT decreased HD and ICF. In contrast, VMT had no significant effect on cortical and spinal parameters. There was a nonsignificant tendency of an increase in MEP amplitudes after both interventions. This implies that human locomotor-related learning involves spinal mechanisms. Despite the decreasing importance of quadrupedal coordination in the course of evolution, these changes in transsynaptic plasticity may reflect a persisting locomotor memory-encoding function in the spinal circuitry of the human upper extremities. Evaluating FCR HD might be helpful for the evaluation and development of locomotor rehabilitation strategies.

Advancing Measurement of Locomotor Rehabilitation Outcomes to Optimize Interventions and Differentiate Between Recovery Versus Compensation

Progress in locomotor rehabilitation has created an increasing need to understand the factors that contribute to motor behavior, to determine whether these factors are modifiable, and if so, to determine how best to modify them in a way that promotes improved function. Currently available clinical measures do not have the capacity to distinguish between neuromotor recovery and compensation for impaired underlying body structure/functions. This Special Interest article examines the state of outcomes measurement in physical therapy in regard to locomotor rehabilitation, and suggests approaches that may improve assessment of recovery and clinical decision-making capabilities. We examine historical approaches to measurement of locomotor rehabilitation outcomes, including rating scales, timed movement tasks, and laboratory-based outcome measures, and we discuss the emerging use of portable technology to assess walking in a free-living environment. The ability to accurately measure outcomes of rehabilitation, both in and away from the clinical/laboratory setting, allows assessment of skill acquisition, retention, and long-term carryover in a variety of environments. Accurate measurement allows behavioral changes to be observed, and assessments to be made, regarding an individual's ability to adapt during interventions and to incorporate new skills into real-world behaviors. The result of such an approach to assessment may be that interventions truly translate from clinical/laboratory to real-world environments. Future locomotor measurement tools must be based on a theoretical framework that can guide their use to accurately quantify treatment effects and provide a basis upon which to develop and refine therapeutic interventions.

Beyond componentry: How principles of motor learning can enhance locomotor rehabilitation of individuals with lower limb loss--A review

Relatively little attention has been given to the use of well-established motor learning strategies to enable individuals with lower limb loss to effectively and safely learn to walk with their prostheses in the home and community. Traditionally, such outcomes have been pursued by focusing on the design and function of a patient's prosthesis, rather than on how he or she should learn to use it. The use of motor learning strategies may enhance physical rehabilitation outcomes among individuals with lower limb loss. This review explores these motor learning strategies and ways in which they can be applied to the physical rehabilitation of individuals with lower limb loss and highlights some of the challenges to their implementation, as well as unanswered research questions.

From spinal central pattern generators to cortical network: integrated BCI for walking rehabilitation.

Success in locomotor rehabilitation programs can be improved with the use of brain-computer interfaces (BCIs). Although a wealth of research has demonstrated that locomotion is largely controlled by spinal mechanisms, the brain is of utmost importance in monitoring locomotor patterns and therefore contains information regarding central pattern generation functioning. In addition, there is also a tight coordination between the upper and lower limbs, which can also be useful in controlling locomotion. The current paper critically investigates different approaches that are applicable to this field: the use of electroencephalogram (EEG), upper limb electromyogram (EMG), or a hybrid of the two neurophysiological signals to control assistive exoskeletons used in locomotion based on programmable central pattern generators (PCPGs) or dynamic recurrent neural networks (DRNNs). Plantar surface tactile stimulation devices combined with virtual reality may provide the sensation of walking while in a supine position for use of training brain signals generated during locomotion. These methods may exploit mechanisms of brain plasticity and assist in the neurorehabilitation of gait in a variety of clinical conditions, including stroke, spinal trauma, multiple sclerosis, and cerebral palsy.