Assessment of dynamic balancing responses following perturbations during slow walking in relation to clinical outcome measures for high-functioning post-stroke subjects.

BACKGROUND: Generating appropriate balancing reactions in response to unexpected loss of balance during walking is important to prevent falls. The purpose of this study was to assess dynamic balancing responses following pushes to the pelvis in groups of post-stroke and healthy subjects. METHODS: Forty-one post-stroke subjects and forty-three healthy subjects participated in the study. Dynamic balancing responses to perturbations triggered at heel strike of the left or right leg, directed in the forward, backward, inward and outward directions during slow treadmill walking were assessed. Responses of the healthy group provided reference values used to classify responses of the post-stroke group into two subgroups; one within the reference responses ("inside" subgroup) and the other that falls out ("outside" subgroup). A battery of selected clinical outcome measures (6-Minute Walk Test, 10-Meter Walk Test, Timed-Up-and-Go test, Four Square Step Test, Functional Gait Assessment, Functional Independence Measure and One-legged stance test) was additionally assessed in the post-stroke group. RESULTS: The "inside" subgroup of post-stroke subjects was able to appropriately modulate centre-of-pressure and ground-reaction-force both under the impaired and non-impaired leg in response to perturbations. The "outside" subgroup of post-stroke subjects showed limited modulation of centre-of-pressure and ground-reaction-force under the impaired leg; instead stepping strategy was used in which the non-impaired leg was placed such as to make a longer step (forward perturbation), to make a shorter step (backward perturbation) or to make a cross-step (outward perturbation). Consequently, peak centre-of-mass displacements following perturbations were significantly higher in the "outside" subgroup compared to the "inside" subgroup. Responses in both subgroups following inward perturbations did not differ. Majority of clinical outcome measures moderately correlated with the peak centre-of-mass displacements for forward perturbations and exhibited weak correlations for other perturbation directions. CONCLUSIONS: Substantial number of post-stroke subjects, that were considered to be independent walkers, have reduced capabilities to execute appropriate balancing responses following perturbations commencing on the hemiparetic leg and may thus benefit from perturbation-based training. Timed-Up-and-Go and Functional Independence Measure tests may provide an indication on the abilities of each subject to counteract unexpected loss of balance. However, a reliable assessment should be done through perturbation-based measures.

Using Inertial Measurement Units and Electromyography to Quantify Movement during Action Research Arm Test Execution.

In patients after stroke, ability of the upper limb is commonly assessed with standardised clinical tests that provide a complete upper limb assessment. This paper presents quantification of upper limb movement during the execution of Action research arm test (ARAT) using a wearable system of inertial measurement units (IMU) for kinematic quantification and electromyography (EMG) sensors for muscle activity analysis. The test was executed with each arm by a group of healthy subjects and a group of patients after stroke allocated into subgroups based on their clinical scores. Tasks were segmented into movement and manipulation phases. Each movement phase was quantified with a set of five parameters: movement time, movement smoothness, hand trajectory similarity, trunk stability, and muscle activity for grasping. Parameters vary between subject groups, between tasks, and between task phases. Statistically significant differences were observed between patient groups that obtained different clinical scores, between healthy subjects and patients, and between the unaffected and the affected arm unless the affected arm shows normal performance. Movement quantification enables differentiation between different subject groups within movement phases as well as for the complete task. Spearman's rank correlation coefficient shows strong correlations between patient's ARAT scores and movement time as well as movement smoothness. Weak to moderate correlations were observed for parameters that describe hand trajectory similarity and trunk stability. Muscle activity correlates well with grasping activity and the level of grasping force in all groups.

A multisession evaluation of an adaptive competitive arm rehabilitation game.

BACKGROUND: People with neurological injuries such as stroke should exercise frequently and intensely to regain their motor abilities, but are generally hindered by lack of motivation. One way to increase motivation in rehabilitation is through competitive exercises, but such exercises have only been tested in single brief sessions and usually did not adapt difficulty to the patient's abilities. METHODS: We designed a competitive arm rehabilitation game for two players that dynamically adapts its difficulty to both players' abilities. This game was evaluated by two participant groups: 15 participants with chronic arm impairment who exercised at home with an unimpaired friend or relative, and 20 participants in the acute or subacute phase of stroke who exercised in pairs (10 pairs) at a rehabilitation clinic. All participants first played the game against their human opponent for 3 sessions, then played alone (against a computer opponent) in the final, fourth session. In all sessions, participants' subjective experiences were assessed with the Intrinsic Motivation Inventory questionnaire while exercise intensity was measured using inertial sensors built into the rehabilitation device. After the fourth session, a final brief questionnaire was used to compare competition and exercising alone. RESULTS: Participants who played against an unimpaired friend or relative at home tended to prefer competition (only 1 preferred exercising alone), and exhibited higher enjoyment and exercise intensity when competing (first three sessions) than when exercising alone (last session). Participants who played against each other in the clinic, however, did not exhibit significant differences between competition and exercising alone. For both groups, there was no difference in enjoyment or exercise intensity between the first three sessions, indicating no negative effects of habituation or novelty. CONCLUSIONS: Competitive exercises have high potential for unsupervised home rehabilitation, as they improve enjoyment and exercise intensity compared to exercising alone. Such exercises could thus improve rehabilitation outcome, but this needs to be tested in long-term clinical trials. It is not clear why participants who competed against each other at the clinic did not exhibit any advantages of competition, and further studies are needed to determine how different factors (environment, nature of opponent etc.) influence patients' experiences with competitive exercises. TRIAL REGISTRATION: The study is not a clinical trial. While human subjects are involved, they do not participate in a full rehabilitation intervention, and no health outcomes are examined.

Toward improving the specificity of perturbation-based training through assessment of dynamic balancing responses: a series of N-of-1 studies in subacute stroke.

Perturbation-based balance training (PBT) has been shown to improve reactive balancing abilities in chronic stroke. To inform future investigations in the subacute phase of stroke, the objective of this series of N-of-1 studies was to investigate the range of balancing responses to unexpected mechanical perturbations applied to the pelvis during walking on an instrumented treadmill before and after PBT training. Three subacute stroke subjects were assessed on each occasion with clinical tests and biomechanical measurements following perturbations applied in forward, backward, inward and outward directions. After 15 daily sessions of PBT, most clinical mobility outcomes showed improvements in all three subjects. Assessment of reactive balancing also showed improvements in all subjects when responding to perturbations in backward and inward directions whereas the changes following perturbations in forward and outward directions were subject-specific. The results suggest that PBT should be individually tailored to target balance deficiencies identified through a serial biomechanical assessment.

A comparison of three balance-assessment scales for patients after stroke with various levels of balance disorder.

It is often difficult for the clinician to choose the most appropriate balance-assessment measure. We wanted to facilitate this decision based on the stroke patient's functional abilities. The aim of our study was to compare three established scales [Berg Balance Scale (BBS), mini-BESTest (MBT) and Functional Gait Assessment (FGA)] in terms of responsiveness, floor and ceiling effects at different levels of ambulation as defined by the Functional Ambulation Classification (FAC). The 18-month prospective study included 88 patients after cerebral stroke, who were able to walk independently or with assistance of one person (FAC 2-6). BBS showed the highest relative gain in the FAC 2-3 group (17% of maximum scale score); in the other two groups (FAC 4-5 and FAC 6), MBT showed the highest relative gain (16 and 13%, respectively), followed by FGA (11 and 10%, respectively). Among the patients with initial FAC 2-3, a floor effect occurred with FGA, while a ceiling effect occurred with BBS among patients with initial FAC 6. Gain in FGA correlated slightly more with improvement detected by MBT (r = 0.60) than with BBS (r = 0.50). We can conclude that BBS seems to be suitable for stroke patients with initial FAC 2-5, whereas MBT and FGA for those with FAC 4-6.

Clinical risk factors for post-stroke urinary incontinence during rehabilitation.

Urinary incontinence (UI) is a common problem after stroke. Risk factors for UI seem to be multifactorial. There is still controversy in which risk factors contribute to UI. The aim of this study was to investigate risk factors for UI in stroke patients during rehabilitation. Study investigated 150 participants after the first stroke consecutively admitted to a post-acute inpatient rehabilitation program. They were divided into continence and incontinence group according to continence status on rehabilitation admission. Data about sociodemographic factors, functional status, comorbidities, current medications, type and localisation of stroke were collected. Compared with the continence group, incontinent participants had significantly worse cognitive status and upper limb function (P ≤ 0.005), more common global aphasia, neglect, visual field defect, agitation/confusion and deficits in somatic sensation (P ≤ 0.014). There were no differences between the groups regarding comorbidities, but incontinent participants received a larger number of current medications (P = 0.020). Incontinent participants had stroke located more common in the right hemisphere, corticosubcortical region and in the total anterior circulation region (P ≤ 0.051). In the multivariate analysis, Brunnstrom recovery stages of the affected upper limb [odds ratio (95% confidence interval: 1.61 (1.27-2.03)], agitation/confusion [5.36 (1.74-16.54)], global aphasia [5.06 (1.40-18.26)] and faecal impaction [3.41 (1.15-10.09)] were independent risk factors for UI. Findings suggest that communicative and cognitive problems, affected upper limb function and faecal impaction are the most important clinical risk factors for UI after stroke. Knowledge of these risk factors may help in the management of UI during rehabilitation of stroke patients.

Algorithm for selection of balance assessment tools in post-stroke patients.

The aim of the study was to design an algorithm of selecting the balance assessment tool in patients after stroke, which could be used in a subacute rehabilitation setting. A retrospective study was carried out to analyse results of standardized balance measurements in three groups of stroke patients classified by Functional Ambulation Category (FAC) (FAC 1 or 2, non-functional ambulation; FAC 3 or 4, ambulatory dependent; FAC 5 or 6, ambulatory independent). Balance functions were evaluated in 62 out of 70 patients (88.6%) at admission and discharge with at least with one standardized assessment tool. In 21 patients (30%), two or more assessment tools were used. From admission to discharge significant changes in balance functions in the non-functional ambulatory group were detected by Postural Assessment Scale for Stroke (PASS) (P = 0.003), in the ambulatory dependent group with PASS (P = 0.025) and Berg Balance Scale (BBS) (P = 0.009) and in the ambulatory independent group with the Timed Up and Go Test (P = 0.002) and Functional Gait Assessment (P = 0.029). In a post-stroke rehabilitation most commonly used BBS and PASS are sensitive enough in non-functional ambulatory and ambulatory dependent patients, though they do not reflect the overall balance function. In ambulatory independent patients, significant changes in balance functions can be detected only with the assessment tools that include the measurements of dynamic balance. Based on the findings, the algorithm for the selection of balance assessment tools in post-stroke rehabilitation setting was formulated according to FAC.

Pilot Long-term Evaluation of Competitive and Cooperative Exercise Games in Inpatient Stroke Rehabilitation.

Interpersonal rehabilitation games, which allow patients to compete or cooperate with other patients or unimpaired loved ones, have demonstrated promising short-term results, but have not yet been tested in longer-term studies. This paper thus presents a preliminary 9-session evaluation of interpersonal rehabilitation games for post-stroke arm exercise. Two pairs of stroke survivors were provided with a system that included one competitive and one cooperative rehabilitation game, and exercised with it for 9 sessions in addition to their conventional therapy. They were able to choose the game they wanted to play in each session, and had to exercise for at least 10 minutes per session. Both pairs completed the protocol without any issues, reporting high levels of motivation and consistent levels of exercise intensity (measured using inertial sensors) across the sessions. Furthermore, the maximum difficulty levels reached in the cooperative game increased over time, and improvements of 1-8 points were observed on the Box and Block test. These results indicate that 2 different interpersonal games are sufficient to promote high levels of motivation and exercise intensity for 9 sessions performed over a 3-week period. As the next step, our system will be expanded with additional competitive, cooperative and single-player games, then tested in full clinical trials in both clinical and home environments.

Overground gait training using a motorized assistive device in patients with severe disabilities after stroke.

Regaining of the patient's ability to walk after stroke is an important goal of rehabilitation programmes. The ultimate goal of gait rehabilitation is to empower patients for overground walking. We have previously developed a prototype of a therapist-controlled mobile platform with compliant pelvis support mechanism that enables balance training during overground walking (device E-go). The aim of this pilot randomized controlled study was to explore the usefulness of the E-go in reducing the number of therapists needed during walking training, and to explore the effectiveness of the E-go on walking abilities in severely affected stroke patients. The study included 19 subacute poststroke patients divided into two groups. The experimental group (nine patients) trained to walk with the E-go and the control group trained within conventional physiotherapy programs for 3 weeks. Outcome measures were walking distance and speed, Fugl-Meyer Assessment, Berg Balance Scale, Functional Ambulation Category and the number of therapists needed during training. At the end of the training both groups significantly improved in walking speed, walking distance, Berg Balance Scale and Fugl-Meyer Assessment (P≤0.001), but there were no between-group differences. The experimental group on average needed a lower number of therapists (P=0.040). These findings highlight the potential of the E-go for overground walking training in severely disabled subacute stroke patients.

A novel robot-assisted training approach for improving gait symmetry after stroke.

Gait asymmetry as a consequence of hemiparesis is known as a serious long-term disability, where typical compensatory gait movements are used by stroke subjects in order to cope with their daily activities. This study presents a gait symmetry training approach consisting of the adaptive robot assistance with the combination of the visual feedback integrated in Balance Assessment Robot for treadmill walking (BAR-TM). The support algorithm is based on gait temporal parameters that change the level of assistive support, which was triggered at different gait subphase events. The presented approach was evaluated on a post-stroke subject in a large number of training sessions. The results have shown significant improvement of gait symmetry indicating that the proposed rehabilitation method has significant potential that should be explored in further studies.

Rasch validation and comparison of Slovenian, Croatian, and Italian versions of the Mini-BESTest in patients with subacute stroke.

We aimed to verify by Rasch analysis whether the Mini-BESTest, a balance measure, confirms its main psychometric properties in patients with subacute stroke undergoing rehabilitation in three different countries (Slovenia, Croatia, and Italy), and to examine the stability of item hierarchy and difficulty across the three national versions through a differential item functioning analysis. We investigated 159 patients with subacute stroke consecutively admitted to three rehabilitation facilities after screening for an intensive, tailored rehabilitation program. Balance function was tested within 36 h from admission and after ∼25 days. As no differential item functioning was found between admission and discharge data or among countries, all data were pooled. Rasch criteria for the functioning of rating scale categories were fulfilled. In terms of internal construct validity, all items except item #14 (Cognitive Get Up & Go; infit value=1.42) showed an acceptable fit to the Rasch model. The patient ability-item difficulty matching was very good. Reliability indices were high. The Principal Component Analysis of standardized residuals confirmed the unidimensionality of the test. On the basis of the item calibration, raw scores of the Mini-BESTest were transformed into linear estimates of dynamic balance and six statistically detectable levels of balance ability were defined. Good psychometric features of the Mini-BESTest were confirmed. The three different national versions showed stability in item hierarchy, indicating equivalence of their cross-cultural adaptations. Problems with item #14 in these patients warrant further study.

Application of haptic interface for finger exercise.

A haptic device with two active degrees-of-freedom and a tendon-driven transmission system was designed, later on constructed, and submitted to testing. It was embodied as a lightweight mechanism with a small workspace that wraps the finger workspace and can generate forces up to 10 N suitable for finger exercise. The control loop and the user application were implemented on a personal computer in the Microsoft Windows environment. Along with the device, application covering several different experiment types was developed. The system was evaluated in a group of stroke patients during a one-month period of therapy. Results for two types of experiments are presented. The progress of the patient affected hand side was found to be greater than for the one nonaffected, however, the mean values of the relevant parameters on the nonaffected side of patients are higher than those for the affected side. Results were compared to the motor component of functional independence measure (M-FIM) measured clinical scale.

Effectiveness of a fall-risk reduction programme for inpatient rehabilitation after stroke.

PURPOSE: To evaluate effectiveness of fall-risk-assessment-based fall prevention for stroke rehabilitation inpatients. METHOD: A consecutive series of 232 patients admitted for the first time to a subacute stroke-rehabilitation ward during 2010-2011 was studied in detail. The Assessment Sheet for Fall Prediction in Stroke Inpatients (ASFPSI by Nakagawa et al.) was used to assess fall-risk upon admission. Association of ASFPSI score and patient characteristics with actual falls was statistically tested. Yearly incidence of falls per 1000 hospital days (HD) was retrospectively audited for the 2006-2014 period to evaluate effectiveness of fall-risk reduction measures. RESULTS: The observed incidence of falls over the detailed-study-period was 3.0/1000 HD; 39% of the fallers fell during the first week after admission. ASFPSI score was not significantly associated with falls. Longer hospital stay, left body-side affected and non-extreme FIM score (55-101) were associated with higher odds of fall. Introduction of fall-risk reduction measures followed by compulsory fall-risk assessment lead to incidence of falls dropping from 7.1/1000 HD in 2006 to 2.8/1000 HD in 2011 and remaining at that level until 2014. CONCLUSIONS: The fall-risk-assessment-based measures appear to have led to decreasing falls risk among post-stroke rehabilitation inpatients classified as being at high risk of falls. The fall prevention programme as a whole was successful. Patients with non-extreme level of functional independence should receive enhanced fall prevention. Implications for Rehabilitation Recognising the fall risk upon the patient's admission is essential for preventing falls in rehabilitation wards. Assessing the fall risk is a team tasks and combines information from various sources. Assessing fall risk in stroke patients using the assessment sheet by Nakagawa et al. immediately upon admission systematically draws attention to the risk of falls in each individual patient.

Grip force tracking system for assessment and rehabilitation of hand function.

The aim of the paper is to present a novel tracking system for the assessment and training of grip force control. The system consists of two force measuring units of different shapes, which can be connected to a personal computer for visual feedback and data acquisition. We present the results of the assessment of the grip force control in 32 healthy subjects of different age groups and preliminary results obtained in a patient after head-injury who was treated with Botulinum-Toxin for hand spasticity. The proposed tracking system was also applied as a training tool in 10 post-stroke patients to possibly improve their grip force control. The results in healthy subjects showed significant differences in grip force control among different age groups. In the patient after Botulinum-Toxin treatment the method revealed noticeable effects of the therapy on the patient's tracking performance. Training with the tracking system showed considerable improvements in the grip force control in 8 out of 10 stroke patients. The proposed tracking method is aimed to be used in connection with different rehabilitation therapies (e.g. physiotherapy, functional electrical stimulation, drug treatment) to follow the influence of the therapy on patient's muscular strength and grip force control.

Training of selective attention in work-active stroke patients.

The aim was to examine the effects of computer-based cognitive rehabilitation of attention in work-active patients after stroke. The study included 11 patients treated as inpatients at the University Rehabilitation Institute, Republic of Slovenia, who were included in intensive selective attention training four times a week for 3 months. Each patient was assessed at the initial and the final rehabilitation stage with the TAP system (Test of Attentional Performance), alertness, and divided attention tasks. The results indicate a moderate to strong increase in performance on the divided attention test and a mild effect on the alertness test. Early cognitive rehabilitation of the attentional system can contribute toward recovery of divided attention in work-active patients after stroke.

Telerehabilitation using virtual reality task can improve balance in patients with stroke.

PURPOSE: The objective of the telerehabilitation is a continuation of the rehabilitation process on patients' home. The study also compares the balance training in clinical environment with the telerehabilitation approach when the physiotherapists and physicians can follow the progress remotely. METHOD: In this paper, the preliminary study of the pilot project with virtual reality (VR)-based tasks for dynamic standing frame supported balance training is presented. Six patients with stroke participated in the study. The patients performed the balance training 3 weeks, 2 weeks in the clinical settings and 1 week in the home environment, five times a week, and each time for up to 20 minutes. Objective effectiveness was demonstrated by parameters as track time, number of collisions and the clinical instruments Berg Balance Scale (BBS), Timed Up & Go (TUG), 10-m walk test and standing on the unaffected and affected extremity. The outcomes were compared to the balance training group without VR and telerehabilitation support. A 2-way ANOVA was used to explore the differences between the both stroke groups. RESULTS: In patients who were subject to VR supported balance training, the BBS demonstrated improvement for 15%, the TUG for 29%, the 10-m walk for 26%, stance time on the affected and unaffected extremity for 200 and 67%, respectively. The follow-up demonstrated that the patients preserved the gained functional improvement. The VR task performance time and number of collisions decreased to 45 and 68%, respectively. Besides, no statistical differences were found between the telerehabilitation approach with VR supported balance training and conventional balance training in clinical settings either regarding the overall mean level or regarding the mean improvement. CONCLUSIONS: The telerehabilitation approach in VR supported balance training improved balance in stroke patients and had similar effect on patients' postural functional improvement as conventional balance training in clinical settings. However, when balance training is continued on patient's home instead of the hospital, it would eventually decrease the number of outpatients' visits, reduce related costs and enable treatment of larger number of patients.

Measuring patterns of disability using the International Classification of Functioning, Disability and Health in the post-acute stroke rehabilitation setting.

OBJECTIVE: To determine whether the International Classification of Functioning, Disability and Health (ICF) model is adequate for assessing disability patterns in stroke survivors in the sub-acute rehabilitation setting in terms of potential changes in functional profiles over time. METHODS: Functional profiles of 197 stroke patients were assessed using the ICF Checklist and the Functional Independence Measure (FIMTM) at admission and discharge from rehabilitation hospital. The ICF Checklist was applied based on medical documentation and rehabilitation team meetings. Descriptive analyses were performed to identify changes in ICF categories and qualifiers from admission to discharge, and correlations between different improvement measures were calculated. RESULTS: Mean rehabilitation duration was 60 days; patients' mean age was 60 years, with mean FIM-score 75 at admission. Mean FIM-score improvement at discharge was 12.5. Within Body Functions, changes in at least 10% of patients were found regarding 13 categories; no categories within Body Structures, 24 within Activities and Participation, and 2 within Environmental Factors. Changes were mostly due to improvement in qualifiers, except for within Environmental Factors, where they were due to use of additional categories. Correlations between improvements in Body Functions and Activities and Participation (regarding capacity and performance), as well as between capacity and performance within Activities and Participation, were approximately 0.4. CONCLUSION: Rating ICF categories with qualifiers enables the detection of changes in functional profiles of stroke patients who underwent an inpatient rehabilitation programme. :

Variable structure pantograph mechanism with spring suspension system for comprehensive upper-limb haptic movement training.

Numerous haptic devices have been developed for upper-limb neurorehabilitation, but their widespread use has been largely impeded because of complexity and cost. Here, we describe a variable structure pantograph mechanism combined with a spring suspension system that produces a versatile rehabilitation robot, called Universal Haptic Pantograph, for movement training of the shoulder, elbow, and wrist. The variable structure is a 5-degree-of-freedom (DOF) mechanism composed of 7 joints, 11 joint axes, and 3 configurable joint locks that reduce the number of system DOFs to between 0 and 3. The resulting device has eight operational modes: Arm, Wrist, ISO (isometric) 1, ISO 2, Reach, Lift 1, Lift 2, and Steer. The combination of available work spaces (reachable areas) shows a high suitability for movement training of most upper-limb activities of daily living. The mechanism, driven by series elastic actuators, performs similarly in all operational modes, with a single control scheme and set of gains. Thus, a single device with minimal setup changes can be used to treat a variety of upper-limb impairments that commonly afflict veterans with stroke, traumatic brain injury, or other direct trauma to the arm. With appropriately selected design parameters, the developed multimode haptic device significantly reduces the costs of robotic hardware for full-arm rehabilitation while performing similarly to that of single-mode haptic devices. We conducted case studies with three patients with stroke who underwent clinical training using the developed mechanism in Arm, Wrist, and/or Reach operational modes. We assessed outcomes using Fugl-Meyer Motor Assessment and Wolf Motor Function Test scores showing that upper-limb ability improved significantly following training sessions.

Psychophysiological responses to robot training in different recovery phases after stroke.

Psychophysiological responses have become a valuable tool in human-robot interaction since they provide an objective estimate of the user's psychological state. Unfortunately, their usefulness in rehabilitation robotics is uncertain since they are influenced by both physical activity and pathological conditions such as stroke. We performed psychophysiological measurements in subacute and chronic stroke patients as well as healthy controls during a reaching and grasping exercise task performed in a multimodal virtual environment. Furthermore, we evaluated the differences in kinematic and static parameters between the three groups of subjects. The results of the observed kinematic and static evaluation parameters showed significant differences when different assistive modes enabled the subject to focus on a particular function of the exercise, like reaching or grasping, or coordinated actions that combine reaching and grasping, reflecting the motor abilities of the individual. The analysis of psychophysiological responses suggests that both chronic and subacute stroke subjects have weaker psychophysiological responses than healthy subjects, though the responses of chronic patients have recovered somewhat. This certainly indicates that further studies are needed before psychophysiological responses can be used in clinical practice.

Design and test of a novel closed-loop system that exploits the nociceptive withdrawal reflex for swing-phase support of the hemiparetic gait.

A novel closed-loop system for improving gait in hemiparetic patients by supporting the production of the swing phase using electrical stimulations evoking the nociceptive withdrawal reflex was designed. The system exploits the modular organization of the nociceptive withdrawal reflex and its stimulation site- and gait-phase modulation in order to evoke movements of the hip, knee, and ankle joints during the swing phase. A modified model-reference adaptive controller (MRAC) was designed to select the best stimulation parameters from a set of 12 combinations of four electrode locations on the sole of the foot and three different stimulation onset times between heel-off and toe-off. It was hypothesized that the MRAC system would result in a better walking pattern compared with an open-loop preprogrammed fixed pattern of stimulation (FPS) controller. Thirteen chronic or subacute hemiparetic subjects participated in a study to compare the performance of the two control schemes. Both control schemes resulted in a more functional gait compared to no stimulation (P < 0.05) with a weighted joint angle peak change of 4.0 ± 1.6 (mean ± Standard deviation) degrees and 3.1 ± 1.4 degrees for the MRAC and FPS schemes, respectively. This indicates that the MRAC scheme performed better than the FPS scheme (P < 0.001) in terms of reaching the control target.