Functional Electrical Stimulation Assistance Research Articles

A robot-based hybrid lower limb system for Assist-As-Needed rehabilitation of stroke patients: Technical evaluation and clinical feasibility

Background:Although early rehabilitation is important following a stroke, severely affected patients have limited options for intensive rehabilitation as they are often bedridden. To create a system for early rehabilitation of lower extremities in these patients, we combined the robotic manipulator ROBERT® with electromyography (EMG)-triggered functional electrical stimulation (FES) and developed a novel user-driven Assist-As-Needed (AAN) control. The method is based on a state machine able to detect user movement capability, assessed by the presence of an EMG-trigger and the movement velocity, and provide different levels of assistance as required by the patient (no support, FES only, and simultaneous FES and mechanical assistance). Methods:To technically validate the system, we tested 10 able-bodied participants who were instructed to perform specific behaviors to test the system states while conducting knee extension and ankle dorsal flexion exercises. The system was also tested on two stroke patients to establish its clinical feasibility. Results:The technical validation showed that the state machine correctly detected the participants’ behavior and activated the target AAN state in more than 96% of the exercise repetitions. The clinical feasibility test showed that the system successfully recognized the patients’ movement capacity and activated assistive states according to their needs providing the minimal level of support required to exercise successfully. Conclusions:The system was technically validated and preliminarily proved clinically feasible. The present study shows that the novel system can be used to deliver exercises with a high number of repetitions while engaging the participants’ residual capabilities through the AAN strategy.

The assistive potential of functional electrical stimulation to support object manipulation in functional upper extremity movements after stroke: A randomized cross-over study

The assistive potential of functional electrical stimulation to support object manipulation in functional upper extremity movements after stroke: A randomized cross-over study

Can inertial measurement unit sensors evaluate foot kinematics in drop foot patients using functional electrical stimulation?

The accuracy of inertial measurement units (IMUs) in measuring foot motion in the sagittal plane has been previously compared to motion capture systems for healthy and impaired participants. Studies analyzing the accuracy of IMUs in measuring foot motion in the frontal plane are lacking. Drop foot patients use functional electrical stimulation (FES) to improve walking and reduce the risk of tripping and falling by improving foot dorsiflexion and inversion-eversion. Therefore, this study aims to evaluate if IMUs can estimate foot angles in the frontal and sagittal planes to help understand the effects of FES on drop foot patients in clinical settings. Two Gait Up sensors were used to estimate foot dorsi-plantar flexion and inversion-eversion angles in 13 unimpaired participants and 9 participants affected by drop foot while walking 6 m in a straight line. Unimpaired participants were asked to walk normally at three self-selected speeds and to simulate drop foot. Impaired participants walked with and without FES assistance. Foot angles estimated by the IMUs were compared with those measured from a motion capture system using curve RMSE and Bland Altman limits of agreement. Between participant groups, overall errors of 7.95° ± 3.98°, -1.12° ± 4.20°, and 1.38° ± 5.05° were obtained for the dorsi-plantar flexion range of motion, dorsi-plantar flexion at heel strike, and inversion-eversion at heel strike, respectively. The between-system comparison of their ability to detect dorsi-plantar flexion and inversion-eversion differences associated with FES use on drop foot patients provided limits of agreement too large for IMUs to be able to accurately detect the changes in foot kinematics following FES intervention. To the best of the authors' knowledge, this is the first study to evaluate IMU accuracy in the estimation of foot inversion-eversion and analyze the potential of using IMUs in clinical settings to assess gait for drop foot patients and evaluate the effects of FES. From the results, it can be concluded that IMUs do not currently represent an alternative to motion capture to evaluate foot kinematics in drop foot patients using FES.

Asymmetric cortical activation in healthy and hemiplegic individuals during walking: A functional near-infrared spectroscopy neuroimaging study.

This study investigated the cortical activation mechanism underlying locomotor control during healthy and hemiplegic walking. A total of eight healthy individuals with right leg dominance (male patients, 75%; mean age, 40.06 ± 4.53 years) and six post-stroke patients with right hemiplegia (male patients, 86%; mean age, 44.41 ± 7.23 years; disease course, 5.21 ± 2.63 months) completed a walking task at a treadmill speed of 2 km/h and a functional electrical stimulation (FES)-assisted walking task, respectively. Functional near-infrared spectroscopy (fNIRS) was used to detect hemodynamic changes in neuronal activity in the bilateral sensorimotor cortex (SMC), supplementary motor area (SMA), and premotor cortex (PMC). fNIRS cortical mapping showed more SMC-PMC-SMA locomotor network activation during hemiplegic walking than during healthy gait. Furthermore, more SMA and PMC activation in the affected hemisphere was observed during the FES-assisted hemiplegic walking task than during the non-FES-assisted task. The laterality index indicated asymmetric cortical activation during hemiplegic gait, with relatively greater activation in the unaffected (right) hemisphere during hemiplegic gait than during healthy walking. During hemiplegic walking, the SMC and SMA were predominantly activated in the unaffected hemisphere, whereas the PMC was predominantly activated in the affected hemisphere. No significant differences in the laterality index were noted between the other groups and regions (p > 0.05). An important feature of asymmetric cortical activation was found in patients with post-stroke during the walking process, which was the recruitment of more SMC-SMA-PMC activation than in healthy individuals. Interestingly, there was no significant lateralized activation during hemiplegic walking with FES assistance, which would seem to indicate that FES may help hemiplegic walking recover the balance in cortical activation. These results, which are worth verifying through additional research, suggest that FES used as a potential therapeutic strategy may play an important role in motor recovery after stroke.

Hybrid robotic and electrical stimulation assistance can enhance performance and reduce mental demand.

Combining functional electrical stimulation (FES) and robotics may enhance recovery after stroke, by providing neural feedback with the former while improving quality of motion and minimizing muscular fatigue with the latter. Here, we explored whether and how FES, robot assistance and their combination, affect users' performance, effort, fatigue and user experience. 15 healthy participants performed a wrist flexion/extension tracking task with FES and/or robotic assistance. Tracking performance improved during the hybrid FES-robot and the robot-only assistance conditions in comparison to no assistance, but no improvement is observed when only FES is used. Fatigue, muscular and voluntary effort are estimated from electromyographic recording. Total muscle contraction and volitional activity are lowest with robotic assistance, whereas fatigue level do not change between the conditions. The NASA-Task Load Index answers indicate that participants found the task less mentally demanding during the hybrid and robot conditions than the FES condition. The addition of robotic assistance to FES training might thus facilitate an increased user engagement compared to robot training and allow longer motor training session than with FES assistance.

Quantifying Arms and Legs Contributions during Repetitive Electrically-Assisted Sit-To-Stand Exercise in Paraplegics: A Pilot Study.

Execution of Sit-to-Stand (SitTS) in incomplete spinal cord injury (SCI) patients involves motor function in both upper and lower extremities. The use of arm support, in particular, is a significant assistive factor while executing SitTS movement in SCI population. In addition, the application of functional electrical stimulation (FES) onto quadriceps and gluteus maximus muscles is one of the prescribed management for incomplete SCI to improve muscle action for simple lower limb movements. However, the relative contribution of upper and lower extremities during SitTS has not been thoroughly investigated. Two motor incomplete SCI paraplegics performed repetitive SitTS to fatigue exercise challenge. Their performance was investigated as a mixed-method case-control study comparing SitTS with and without the assistance of FES. Three sets of SitTS tests were completed with 5-min resting period allocated in between sets, with mechanomyography (MMG) sensors attached over the rectus femoris muscles bilaterally. The exercise was separated into 2 sessions; Day 1 for voluntary SitTS and Day 2 for FES-assisted SitTS. Questionnaires were conducted after every session to gather the participants' input about their repetitive SitTS experience. The analysis confirmed that a SitTS cycle could be divided into three phases; Phase 1 (Preparation to stand), Phase 2 (Seat-off), and Phase 3 (Initiation of hip extension), which contributed to 23% ± 7%, 16% ± 4% and 61% ± 6% of the SitTS cycle, respectively. The contribution of arms and legs during SitTS movement varied in different participants based on their legs' Medical Research Council (MRC) muscle grade. In particular, the applied arm forces start to increase clearly when the leg forces start to decline during standing. This finding is supported by the significantly reduced MMG signal indicating leg muscle fatigue and their reported feeling of tiredness.

Postural control during turn on the light task assisted by functional electrical stimulation in post stroke subjects

Postural control mechanisms have a determinant role in reaching tasks and are typically impaired in post-stroke patients. Functional electrical stimulation (FES) has been demonstrated to be a promising therapy for improving upper limb (UL) function. However, according to our knowledge, no study has evaluated FES influence on postural control. This study aims to evaluate the influence of FES UL assistance, during turning on the light task, in the related postural control mechanisms. An observational study involving ten post-stroke subjects with UL dysfunction was performed. Early and anticipatory postural adjustments (EPAs and APAs, respectively), the weight shift, the center of pressure and the center of mass (CoM) displacement were analyzed during the turning on the light task with and without the FES assistance. FES parameters were adjusted to improve UL function according to a consensus between physiotherapists’ and patients’ perspectives. The ANOVA repeated measures, Paired sample t and McNemar tests were used to compare postural control between the assisted and non-assisted conditions. When the task was assisted by FES, the number of participants that presented APAs increased (p = 0.031). UL FES assistance during turning on the light task can improve postural control in neurological patients with UL impairments.

Aerobic Responses to FES-Assisted and Volitional Cycling in Children with Cerebral Palsy.

Recumbent stationary cycling is a potential exercise modality for individuals with cerebral palsy (CP) that lack the postural control needed for upright exercises. Functional electrical stimulation (FES) of lower extremity muscles can help such individuals reach the cycling intensities that are required for aerobic benefits. The aim of this study was to examine the effect of cycling with and without FES assistance to that of a no-intervention control group on the cardiorespiratory fitness of children with CP. Thirty-nine participants were randomized to a FES group that underwent an 8-week FES-assisted cycling program, the volitional group (VOL), who cycled without FES, or a no-intervention control group (CON) (15 FES, 11 VOL, 13 CON). Cadence, peak VO2, and net rise in heart rate were assessed at baseline, end of training, and washout (8-weeks after cessation of training). Latent growth curve modeling was used for analysis. The FES group showed significantly higher cycling cadences than the VOL and CON groups at POST and WO. There were no differences in improvements in the peak VO2 and peak net HR between groups. FES-assisted cycling may help children with CP attain higher cycling cadences and to retain these gains after training cessation. Higher training intensities may be necessary to obtain improvements in peak VO2 and heart rate.

Estimating elbow Torque from electrical Stimulation using a Particle Filter

This study analyses the relationship between functional electrical stimulation (FES) and the induced torque for elbow flexion. The aim is to develop an FES-torque model that is simple to implement and understand, and is easily invertible so that the required FES for a desired assistive torque can be determined to enable control by FES. For accurate control, the FES-torque model must also be adaptable to time-varying behaviour of the muscle such as fatigue. The proposed FES-torque model is a sigmoid function, and a particle filter is implemented to estimate the change in parameters of the sigmoid function over time. The results show that the particle filter is successfully able to adapt to changes in the FES-induced torque and can be used to improve the estimate of FES-induced torque, with an overall average RMS error of 0.24 N.m or 7.85%. The improved FES-torque estimate allows for simple and more effective control of FES assistance and better fatigue management.

Synergy-Based FES for Post-Stroke Rehabilitation of Upper-Limb Motor Functions.

Functional electrical stimulation (FES) is capable of activating muscles that are under-recruited in neurological diseases, such as stroke. Therefore, FES provides a promising technology for assisting upper-limb motor functions in rehabilitation following stroke. However, the full benefits of FES may be limited due to lack of a systematic approach to formulate the pattern of stimulation. Our preliminary work demonstrated that it is feasible to use muscle synergy to guide the generation of FES patterns.In this paper, we present a methodology of formulating FES patterns based on muscle synergies of a normal subject using a programmable multi-channel FES device. The effectiveness of the synergy-based FES was tested in two sets of experiments. In experiment one, the instantaneous effects of FES to improve movement kinematics were tested in three patients post ischemic stroke. Patients performed frontal reaching and lateral reaching tasks, which involved coordinated movements in the elbow and shoulder joints. The FES pattern was adjusted in amplitude and time profile for each subject in each task. In experiment two, a 5-day session of intervention using synergy-based FES was delivered to another three patients, in which patients performed task-oriented training in the same reaching movements in one-hour-per-day dose. The outcome of the short-term intervention was measured by changes in Fugl-Meyer scores and movement kinematics. Results on instantaneous effects showed that FES assistance was effective to increase the peak hand velocity in both or one of the tasks. In short-term intervention, evaluations prior to and post intervention showed improvements in both Fugl-Meyer scores and movement kinematics. The muscle synergy of patients also tended to evolve towards that of the normal subject. These results provide promising evidence of benefits using synergy-based FES for upper-limb rehabilitation following stroke. This is the first step towards a clinical protocol of applying FES as therapeutic intervention in stroke rehabilitation.

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OBJECTIVES/SPECIFIC AIMS: Evaluate the effect of multijoint functional electrical stimulation (FES) on energy consumption during post-stroke walking. METHODS/STUDY POPULATION: A 67-year-old male with chronic stroke was implanted with an 8-channel implanted pulse generator to stimulate flexor and extensor muscles of the hip, knee, and ankle. Oxygen consumption was measured with a k2b4 portable pulmonary gas analyzer during walking with and without FES assistance. Data were analyzed during steady state oxygen consumption within the last 2 minutes of a 5 minute walk. Distance and walking speed were also measured. RESULTS/ANTICIPATED RESULTS: Electrical stimulation increased walking speed from 0.29 to 0.64 minute/second. Faster walking corresponded with increased oxygen consumption from 10.1 to 14.4 mL O2/kg per minute. Energy cost, consumption as a function of distance, decreased from 3.7 to 2.9 mL O2/kg per minute walking with stimulation compared with without. DISCUSSION/SIGNIFICANCE OF IMPACT: These preliminary data suggest improvements in walking speed with FES are accompanied by increased energy consumption and decreased energy cost. Oxygen consumption during FES assisted walking was <50% of the peak for able bodied individuals of similar age; patients may successfully use the system for community ambulation.

Functional Electrical Stimulation to Augment Poststroke Reach and Hand Opening in the Presence of Voluntary Effort

Background. Hemiparesis after stroke can severely limit an individual’s ability to perform activities of daily living. Functional electrical stimulation (FES) has the potential to generate functional arm and hand movements. We have observed that FES can produce functional hand opening when a stroke patient is relaxed, but the FES-produced hand opening is often overpowered by finger flexor coactivation in response to patient attempts to reach and open the hand. Objective. To determine if stimulating both reaching muscles and hand opening muscles makes it possible to achieve useful amounts of simultaneous reach and hand opening even in the presence of submaximal reaching effort. Methods. We measured reach and hand opening during a reach-then-open the hand task under different combinations of voluntary effort and FES for both reach and hand opening. Results. As effort was reduced and stimulation generated more movement, a greater amount of reach and hand opening was achieved. For the first time, this study quantified the effect of voluntary effort for reach and hand opening on stimulated hand opening. It also showed variability in the interaction of voluntary effort and stimulation between participants. Additionally, when participants were instructed to reach with partial effort during simultaneous FES, they achieved greater reach and hand opening. Conclusions. Simultaneous reaching and FES hand opening is improved by including FES for reach and reducing voluntary effort. In the future, an upper extremity neuroprosthesis that uses a combination of voluntary effort and FES assistance may enable users to perform activities of daily living.

Quantification of gait kinematics and walking ability of people with multiple sclerosis who are new users of functional electrical stimulation

To assess whether the application of Functional Electrical Stimulation improves gait kinematics and walking ability in people with multiple sclerosis who experience foot drop. Acute open labelled comparative observation trial. Twelve people (3 females, 9 males, EDSS 2-4) with relapsing remitting multiple sclerosis (47.8 years (standard deviation 6.6)) who were new users of functional electrical stimulation. Gait kinematics were recorded using 3D gait analysis. Walking ability was assessed through the 10-m walk test and the 6-min walk test. All assessments were performed with and without the assistance of functional electrical stimulation. The effect of functional electrical stimulation was analysed using paired t-tests. Ankle dorsiflexion at initial contact (p = 0.026), knee flexion at initial contact (p = 0.044) and peak knee flexion during swing (p = 0.011) were significantly greater whilst walking with Functional Electrical Stimulation. The increased peak dorsiflexion in swing of nearly 4 degrees during functional electrical stimulation assisted walking approached significance (p = 0.069). The 10-m walk time was significantly improved by functional electrical stimulation (p = 0.004) but the 6 min walk test was not. The acute application of functional electrical stimulation resulted in an orthotic effect through a change in ankle and knee kinematics and increased walking speed over a short distance in people with multiple sclerosis who experience foot drop.

Effect of a Bout of Leg Cycling With Electrical Stimulation on Reduction of Hypertonia in Patients With Stroke

Yeh C-Y, Tsai K-H, Su F-C, Lo H-C. Effect of a bout of leg cycling with electrical stimulation on reduction of hypertonia in patients with stroke. Objectives To evaluate whether a bout of leg cycling in patients with stroke reduces muscle tone and to determine whether neuromuscular functional electrical stimulation (FES) to the affected leg during cycling is more effective than cycling without FES. Design Within-subject comparison. Setting University hospital. Participants Patients with stroke (N=16; age range, 42-72y; <8wk poststroke) with hypertonia in the affected leg. Interventions Subjects' affected leg (1) performed cycling exercise with the assistance of FES (assisted-cycling session) and (2) performed cycling exercise without the assistance of FES (nonassisted-cycling session). Subjects sat in a specially designed wheelchair positioned on a resistance-free roller for each 20-minute session. Main Outcome Measures Changes in muscle tone pre- and posttest session were compared by using the Modified Ashworth Scale and the pendulum test (relaxation index and peak velocity). Results Modified Ashworth Scale scores were significantly lower ( P<.05) and relaxation index and peak velocity values were significantly higher ( P<.05) after both sessions. Changes in Modified Ashworth Scale scores, relaxation index, and peak velocity values showed a significant ( P<.05) difference between the 2 sessions, and assisted cycling reduced hypertonia more than nonassisted cycling. Conclusions The hypertonia of patients with stroke showed a significant decrease immediately after a bout of leg-cycling exercise. FES-assisted leg cycling was better than nonassisted cycling for reducing hypertonia.

The Effect of an Auxiliary Stimulation on Motor Function Restoration by FES

Functional Electrical Stimulation (FES) is a technology to generate neural activity in an artificial way to activate muscles. However, as reported by some researchers, the human responses to FES are likely to be affected by several factors, such as spasticity, muscle fatigue, nerve habituation and so forth. Consequently, the function restoration by FES is neither durable, nor stable. In order to realize long-term and stable FES assistance, this study investigated whether and why an Auxiliary Stimulation (AS) to the Gastrocnemius, with current frequency ranged from 2000 to 6000Hz, could alleviate the symptom of spasticity and muscle fatigue caused by the stimulation to the Tibialis Anterior. We have developed a portable auxiliary stimulator, and performed experiments to verify its effectiveness. The results showed that our approach enabled comparatively stable and durable function restoration assistance. Moreover, for understanding underlying neuromuscular processes elicited by the AS and its qualitative nature, this study also measured the Hoffmann-reflex (H-reflex) in soleus muscle before and after the AS, to interpret the effect of the Auxiliary Stimulation.

O044 Changes in upper limb isometric strength and error tracking following training using functional electrical stimulation

CHANGES IN UPPER LIMB ISOMETRIC STRENGTH AND ERROR TRACKING FOLLOWING TRAINING USING ITERATIVE LEARNING CONTROL (ILC) MEDIATED BY FUNCTIONAL ELECTRICAL STIMULATION (FES) Authors: Hughes, A. M. MSc1, Freeman, C. PhD2, Burridge, J. PhD1, Chappell, P. PhD2, Lewin, P. PhD2 and Rogers, E. PhD2 Affiliations: University of Southampton, Southampton, SO17 1BJ, UK 1 School of Health Professions and Rehabilitation Sciences 2 School of Electronics and Computer Science SUMMARY Based on existing motor control theory, an intervention involving a robot, ILC and FES was developed and tested on five chronic stroke patients. Improvements were seen in isometric strength and error tracking. CONCLUSIONS ILC mediated by FES enabled five chronic stroke subjects to accurately track a range of trajectories. Over time this related to an improvement in motor control reflected by increasing accuracy observed in unassisted tracking, and in isometric strength. INTRODUCTION Current opinion in motor learning, reinforced by clinical evidence, supports the use of FES and robot therapy to improve motor control [1-3]. ILC is a technique applicable to processes which repeatedly perform a task with a view to sequentially improving accuracy such as trajectory following in robots. The aim of this study is to test the feasibility of applying ILC to neurological rehabilitation. PATIENTS/MATERIALS and METHODS 5 hemiplegic stroke subjects underwent screening tests, and baseline assessments including isometric strength. Subjects used a robotic workstation to track 2 dimensional trajectories, over 18 intervention sessions within a 3 month period. At the beginning and end of each intervention session the ability of the stroke subject to track four trajectories without any FES or robot assistance was assessed. During the treatment sessions, ILC was used to modulate the FES applied to their triceps muscles in terms of timing and amplitude to improve tracking performance, whilst encouraging a maximal voluntary contribution to the task. Assessments of isometric muscle strength in six directions from a mid position were repeated after the eighteen sessions and for two subjects after an additional seven sessions. RESULTS Improvements in isometric strength were seen for all individual subjects after the intervention, with significant improvements for five out of six directions. Unassisted performance of the tracking tasks improved significantly for 3 out of the 4 tasks across the group. Subjects who performed poorly on the initial visit, showed the biggest improvements in tracking. DISCUSSION Analysis of the variability of the results may assist in the identification of good responders. Future work with the existing system includes assessing the potential for use with other neurological conditions, such as cerebral palsy and incomplete spinal cord injury. A subsequent study will develop a system for reaching in three dimensions and include opening the wrist and hand using ‘Smart glove’ as a position sensor. REFERENCES [1] De Kroon, J. R., van der Lee, J. H., Izerman, M. J., & Lankhorst, G. J. 2002, Clinical Rehabilitation, vol. 16, pp. 350-360. [2] Schmidt, R. A. & Lee, T. D. Motor control and learning a behavioural emphasis. 3rd Edition. 261-285. 1999. Human Kinetics. [3] Kwakkel, G., Kollen, B. J., & Krebs H.I 2008, Neurorehabilitation and Neural Repair, vol. 22, pp. 111-121.

Electromyographic signal-activated functional electrical stimulation of abdominal muscles: the effect on pulmonary function in patients with tetraplegia

Paralysis of abdominal muscles is the main cause of respiratory dysfunctions in patients with lower cervical spinal cord lesion. Activation of the abdominal muscles using functional electrical stimulation (FES) improved respiratory function in these patients. But application of FES frequently requires a caregiver, and it may not be well synchronized with the patient's respiratory activity. To perform preliminary examination of electromyographic (EMG)-activated FES for caregiver-independent and synchronized cough and expiration induction in tetraplegia. Self-controlled study. Loewenstein Rehabilitation Center, Raanana, Israel. A total of 10 male patients with complete or almost complete tetraplegia. Peak expiratory flow (PEF), forced vital capacity (FVC), and maximal voluntary ventilation (MVV). The outcome measures were examined with the abdominal muscles unassisted or assisted by various methods. These included manual assistance or application of FES, activated by a caregiver, by the patient, or by EMG signals elicited from the patient's muscle. Manual assistance improved the mean PEF value by 36.7% (P<0.01) and the mean FVC value by 15.4% (P=0.01). FES did not significantly change most measurements, and patient-activated FES even reduced PEF (P<0.05). But following EMG-activated FES PEF and FVC values were higher than those following patient-activated FES (P<0.05 for PEF; P<0.01 for FVC), and their mean values were higher by 15.8 and 18.9%, respectively. Abdominal FES failed to improve respiratory function in this study, but applying FES to abdominal muscles by EMG from the patient's muscle may promote caregiver-free respiration and coughing in persons with cervical SCL.

FES Gait Re-education: The Swing Phase Estimation

This paper presents the use of multiple sensors for walking assessment and provision of cognitive feedback during early re-education of incomplete spinal cord injured (SCI) humans. The paper is focused on the swing phase estimation as an important part of the Functional Electrical Stimulation (FES) gait re-education system for incomplete spinal cord injured persons. The proposed sensory system comprises four accelerometers, one gyro placed at the shank of the paretic leg, and two goniometers placed at the knee and ankle joints, respectively. The data from the sensors are input in the mathematical algorithm applied for swing quality estimation. The output from the algorithm is a numerical value. The calculated output is divided into three levels, each defining the swing quality in terms of good, sufficient, and poor. This information is provided to the patient as an auditory signal. The patient is taught to maximize his efforts to improve the quality of walking, that is, to move the more affected leg in a way that will generate the auditory output corresponding to the level "good". The preliminary measurements were performed in healthy subjects walking on even terrain and in an incomplete SCI person with C6 lesion during walking on the treadmill. FES in the latter case was triggered manually by a physiotherapist. The results showed that the timing of FES triggering played an important role in sensory-supported FES-assisted walking, that is, the auditory feedback was also a cue to the therapist controlling the FES. The swing quality estimation enabled patients to voluntarily improve their walking, consequently the intensity of FES assistance was decreased. This suggests that the use of an FES multisensor system for cognitive feedback is efficient rehabilitative method in early stage of rehabilitation of walking.

Functional electrical stimulation for grasping and walking: indications and limitations.

This review describes the state of art in the field of Functional Electrical Stimulation (FES) and its impact on improving grasping and walking functions in acute and chronic Spinal Cord Injured (SCI) patients. It is argued that during the early rehabilitation period the FES systems with surface stimulation electrodes should be used to assist training of hand and leg movements in SCI patients. Our clinical trials have shown that a number of acute SCI patients with impaired walking and grasping functions could improve these functions due to training with an adjustable FES system to the point that they finally did not need the FES system to carry out these tasks. Other acute SCI patients, who did not recover the desired function, were enabled to perform either walking or grasping with the FES assistance. We believe that the subjects who can perform grasping or walking with the help of FES, and still use the neuroprosthesis 6 months after being subjected to the FES training, should consider the FES system as a prosthetic device in Activities of Daily Living (ADL). Despite the significant technical progress achieved in the last 10 to 15 years in the FES field, there is a general consensus that these systems are not sufficiently advanced and that they need further development. The limited acceptance of the FES technology can be in part explained by the fact that it is not completely mature and that the patients still require daily assistance to use the FES systems. Nevertheless the present FES treatments combined with conventional occupational and physical therapy still remain the most promising approach in rehabilitating SCI patients. In this review, advantages and limitations of different FES systems that are used to restore grasping and walking functions are discussed.

Lower extremity applications of functional neuromuscular stimulation.

Functional electrical stimulation (FES) applications in the lower extremity are common in research laboratories, but clinical applications are minimal. This review summarizes current knowledge with respect to clinical application. When electrical stimulation is used in clinical applications for functional movement such as standing and walking, it is typically applied in an open-loop manner; a predetermined stimulus pattern is delivered regardless of the consequences of the actual movement. Few clinical applications of FES involve closed-loop control because of the numerous difficulties involved in its application. As with any volitional muscle contraction, electrically stimulated muscle contractions will exhibit fatigue. Although the dynamics of fatigue may differ, electrically stimulated muscle contractions cannot be continuously sustained, and if the duty cycle is too severe, even alternating periods of rest and contraction cannot be sustained at a constant force level. The exact nature of fatigue is highly specific to the past history of the individual muscle and to the individual subject. Despite their intricate detail, quantitative modeling studies have not yet been applied extensively to clinical applications. Present implantable systems are not yet a viable option for clinical application. It is not clear whether more success with surface or percutaneous systems must first be achieved to justify implantation or whether greater improvements in implantable technology and surgical protocols are needed before implantable systems will become practical. It is clear that almost any reasonably designed stimulation protocol will increase muscle bulk. The existence of other therapeutic benefits and their cost/benefit ratios remain to be fully established. It is possible to stand through bilateral stimulation of the quadriceps. Using surface electrodes, this technique is achievable in any physical therapy clinic having minimal expertise in neuromuscular stimulation. FES-aided standing must be conducted as a research project with a protocol approved by the local institutional review board, as there are currently no FDA-approved stimulation devices for standing. Multichannel FES systems are not currently available for clinical application in the United States. This may change if the "Parastep" system receives FDA approval. Percutaneous and implanted systems are years away from commercialization and clinical availability. Hybrid systems, based primarily on the reciprocating gait orthosis (RGO), are presently the only clinically available form of walking that includes some form of FES assistance. The costs and benefits of adding FES to the RGO and the long-term user acceptance rate for these systems remain to be determined.