Application Of Functional Electrical Stimulation Research Articles

Functional electrical stimulation to enhance reactive balance among people with hemiparetic stroke.

Individuals with stroke demonstrate a twofold higher fall incidence compared to healthy counterparts, potentially associated with deficits in reactive balance control, which is crucial for regaining balance from unpredictable perturbations to the body. Moreover, people with higher stroke-related motor impairment exhibit greater falls and cannot recover balance during higher perturbation intensities. Thus, they might need supplemental agents for fall prevention or even to be included in a perturbation-based protocol. Functional electrical stimulation is a widely used clinical modality for improving gait performance;however, it remains unknown whether it can enhance or interfere with reactive balance control. We recruited twelve ambulatory participants with hemiparetic stroke (61.48 ± 6.77years) and moderate-to-high motor impairment (Chedoke-McMaster Stroke Leg Assessment ≤ 4/7). Each participant experienced 4 unpredicted paretic gait-slips, with and without functional electrical stimulation (provided 50-500ms after perturbation) in random order. The paretic quadriceps muscle group was chosen to receive electrical stimulation, considering the role of support limb knee extensors for preventing limb-collapse. Outcomes includingprimary (laboratory falls), secondary (reactive stability, vertical limb support) and tertiary (compensatory step length, step initiation, execution time) measureswere compared between the two conditions. Participants demonstrated fewer falls, higher reactive stability, and higher vertical limb support (p < 0.05) following gait-slips with functional electrical stimulation compared to those without. This was accompanied by reduced step initiation time and a longer compensatory step (p < 0.05). The application of functional electrical stimulation to paretic quadriceps following gait-slips reduced laboratory fall incidence with enhanced reactive balance outcomes among people with higher stroke-related motor impairment. Our results lay the preliminary groundwork for understanding the instantaneous neuromodulatory effect of functional electrical stimulation in preventing gait-slip falls, future studies could test its therapeutic effect on reactive balance. Clinical registry number: NCT04957355.

Peculiarities of distribution of electrical activity of muscles during walking along treadmill

Authors of this article give the comparative estimation of peculiarities of walking along the horizontal surface and treadmill. Authors thoroughly investigated change of the main parameters and EMG-pattern of muscles at different cadences during walking along the horizontal surface and treadmill. Authors established, that during walking along treadmill cadence changes quite insufficiently, while the step length changes to a greater extent. From authors’ point of view, such disproportionate change of cadence and step length leads to the expressed transformation of the resonance properties of the lower extremities, i.e. to discrepancy of frequency of the forced oscillations with the own oscillations of the lower extremities. From the authors’ point of view, change of the resonance phenomena are revealed in inconsiderable increase of the mean electrical activity during the locomotor cycle, in absence of the parabolic dependence in the curve of the summary integral of electrical activity for the locomotor cycle during walking at different cadence, in very limited zone of the optimal walking cadence, in slight growth of muscle capacity with increase of walking velocity. Authors suppose, that training of walking along treadmill and especially training with application of functional electrical stimulation (FES) must be realized with great care, what supposes determination of the optimal walking velocity (i.e. that velocity, which is accompanied by the maximal decrease of the energy expenditures), and also definition of the mean electrical activity (muscle capacity) and the summary integral for the distance of 10 m (work of muscle with an account of both cadence and the step length). Authors consider, that it is possible to apply FES during walking along treadmill only in those patients, who are able to walk with velocity 2.5 km/hour and more.

Study on Effects of Auditory Feedback and Application of Functional Electrical Stimulation During Gait on Balance, Gait and Lower Extremity Function in Patients with Subacute Stroke

Study on Effects of Auditory Feedback and Application of Functional Electrical Stimulation During Gait on Balance, Gait and Lower Extremity Function in Patients with Subacute Stroke

Optimal design of electrodes for functional electrical stimulation applications to single layer isotropic tissues

PurposeThe purpose of this paper is to investigate the design of skin surface electrodes for functional electrical stimulation using an isotropic single layered model of the skin and underlying tissue. A concentric ring electrode geometry was analysed and compared with a conventional configuration, specifically to localise and maximise the activation at depth and minimise the peak current density at the skin surface.Design/methodology/approachThe mathematical formulation determines the spatial electric potential distribution in the tissue, using the solution to the Laplace equation in the lower half space subject to boundary conditions given by the complete electrode model and appropriate asymptotic decay. Hence, it is shown that the electric potential satisfies a weakly singular Fredholm integral equation of the second kind which is then solved numerically in MATLAB for a novel concentric ring electrode configuration and the conventional two disk side-by-side electrode configuration.FindingsIn both models, the electrode geometry can be optimised to obtain a higher activation and lower maximum current density. The concentric ring electrode configuration, however, provides improved performance over the traditional two disk side-by-side electrode configuration.Research limitations/implicationsIn this study, only a single layer of medium was investigated. A comparison with multilayer tissue models and in vivo validation of numerical simulations are required.Originality/valueThe developed mathematical approaches and simulations revealed the parameters that influence nerve activation and facilitated the theoretical comparison of the two electrode configurations. The concentric ring configuration potentially may have significant clinical advantages.

Сlinico-biomechanical foundation of necessity of rehabilitation in adult patients with hereditary limb-girdle muscular dystrophy, type I: clinical case

Modern approach to rehabilitation of patients with limb girdle muscular dystrophy of type I are discussed in this article. Authors thoroughly investigated the clinical picture of limb-girdle muscular dystrophy, pathogenesis of this disease and the main principles of its treatment. On the example of the concrete patient authors considered the clinical picture of the limb-girdle muscle dystrophy and also the biomechanical and energetic parameters of walking. Authors demonstrated, that essential disturbance of the locomotor function is seen in this patient, what is revealed in remarkable diminution of the mean walking velocity, in severe transformation of the temporal structure of walking, in reduction of amplitude of movements at some joints of the lower extremities and increase of amplitude at the other joints, in displacement of all extreme values to the right along the temporal axis, in remarkable weakening of the support and push functions of the lower extremities, in change of the form of the vertical component Rz of ground reaction force from two-peaked to the triangular, in expressed diminution of moments of muscle forces at the joints of the lower extremities. Authors also point out, that it is necessary to carry out regular courses of rehabilitation in such patients with the purpose to improve the locomotor function. Besides, it is very expedient to retrace systematically changes of the biomechanical and innervative structure of walking. On the grounds of investigation of structure of walking of patient with limb girdle muscular dystrophy authors revealed necessity of ortheses and the subsequent application of functional electrical stimulation of muscles during walking. On the basis of realization of the trial sessions authors for the first time determined the main correctional influences, necessary for these patients and also peculiarities of the amplitude and, especially, temporal programs of functional electrical stimulation of muscles in such patients. Patient herself notes greater stability during walking, possibility of walking greater distance without fatigability. The received results give foundation for the further planning of the course of rehabilitation in such patients.

Implementing functional electrical stimulation clinical practice guidelines to support mobility: A stakeholder consultation.

Functional Electrical Stimulation (FES) has been used to support mobility for people with upper motor neuron conditions such as stroke and multiple sclerosis for over 25 years. Recent development and publication of clinical practice guidelines (CPGs) provide evidence to guide clinical decision making for application of FES to improve mobility. Understanding key barriers to the implementation of these CPGs is a critical initial step necessary to create tailored knowledge translation strategies. A public involvement and engagement consultation was conducted with international stakeholders including researchers, clinicians and engineers working with FES to inform implementation strategies for CPG use internationally. Reflexive thematic analysis of the consultation transcripts revealed themes including inconsistent use of CPGs, barriers to implementation such as limited access to FES and low clinician confidence, and the need for a tiered education approach with ongoing support. Insights derived from this consultation will inform the development of knowledge translation strategies to support the next steps to implementing FES use for mobility.

Development of an Aerogel-Based Wet Electrode for Functional Electrical Stimulation.

Functional electrical stimulation (FES) has been a useful therapeutic tool in rehabilitation, particularly for people with paralysis. To deliver stimulation in its most basic setup, a stimulator and at least a pair of electrodes are needed. The electrodes are an essential part of the system since they allow the transduction of the stimulator signals into the body. Their performance can influence the experience of both patient and therapist in terms of movement generation, comfort, and ease of use. For non-invasive surface stimulation, current electrode options have several limitations involving their interfacing with the skin, practical inconveniences, and short-term functionality. Standard hydrogel electrodes tend to lose their adhesion with the skin quickly, while dry or textile electrodes require constant wetting to be comfortable. In this paper, we present the fabrication, characterization, and FES testing of a new aerogel-based wet electrode for surface stimulation applications for long-term and reusable FES applications. We investigated its functionality by stimulating the biceps brachii of twelve healthy individuals and collected elbow joint torque and comfort ratings for three different intensity levels (low, moderate, and high) of FES. Comparing to standard hydrogel electrodes, no statistically significant difference was found for any intensity of stimulation in either torque or comfort. Overall, the new aerogel-based electrode has an appropriate impedance, is flexible and soft, is conformable to the skin, has a high water absorption and retention, and can be used for FES purposes.

Surgical Techniques for Glottal Airway Enlargement -Laterofixation of the Vocal Fold-

Glottal airway enlargement is required to manage dyspnea due to bilateral vocal fold paralysis (BVFP). The method of vocal fold laterofixation reported by Ejnell et al. is relativly non-invasive and has been considered the first choice in cases of BVFP in recent years. We used a video-laryngoscope to obtain a better endolaryngeal view and a GORE-TEX® Soft Tissue Patch as a spacer between the thyroid lamina and the nylon knot to prevent loosening. Laryngeal pacing is a more dynamic and physiologic treatment approach than static airway enlargement procedures, such as laterofixation of the vocal fold. Laryngeal pacing is the application of functional electrical stimulation (FES) of the laryngeal abductor muscles. We evaluated the efficacy of FES in restoring glottal opening, ventilation, and exercise tolerance in a BVFP canine model. An implantable stimulator and deep brain stimulation electrodes were surgically implanted into both posterior cricoarytenoid (PCA) muscles in the animal, and the bilateral recurrent laryngeal nerves were sectioned and repaired. Beyond three months postoperatively, there was passive airway narrowing and further closure of the glottis during hypercapnia. The animal showed severe stridor and could only walk for one to two minutes on a treadmill. With the stimulation-on condition, the glottal area increased considerably, equaling that of a normally innervated animal. Exercise tolerance also returned to normal. Bilateral PCA stimulation offers a physiologic approach to restore ventilation to a normal level in cases of BVFP.

Evaluating the validity of a functional electrical stimulation clinical decision making tool: A qualitative study

Following central nervous system damage, the recovery of motor function is a priority. For some neurological populations, functional electrical stimulation (FES) is recommended in best practice guidelines for neurorehabilitation. However, limited resources exist to guide FES application, despite clinicians reporting that a lack of FES knowledge prevents use in clinical practice. The FES Clinical Decision Making Tool was developed to assist clinicians with FES application and translation into clinical practice. The purpose of this study was to evaluate the content validity of the Tool from the perspectives of Canadian physical and occupational therapists using FES in neurorehabilitation. Thirteen participants (twelve women, one man), aged 40.5 ± 10.3 years, participated in individual semi-structured interviews to explore their clinical decision making experiences when applying FES and to evaluate the content validity (i.e., appropriateness, comprehensibility, and comprehensiveness) of the Tool. Interviews were analyzed using a qualitative conventional content analysis following the DEPICT model. Three themes were identified. 1) Clinician context influences FES usage. Participants' experiences with FES use varied and application was influenced by treatment goals. 2) Parameter selection in clinical practice. Participants identified decision-making strategies and the challenges of parameter selection. 3) With modifications, the Tool is a valid resource to inform FES applications. Participants discussed its strengths, limitations, and suggested changes. While the Tool is useful, a more extensive resource (e.g., appendix) for the Tool is warranted. A revised Tool was created to improve its comprehensiveness and comprehensibility. Thus, the Tool is a valid resource for applying FES in neurorehabilitation.

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.

CONTINUOUS ADAPTIVE CONTROL OF THE KNEE JOINT MOVEMENT

In this paper, we develop a control law for Functional Electrical Stimulation (FES) application fields. This work aims to command the knee joint movement of patients in the seated position suffering from neurological disorders that lead to a partial or total paralysis of the limb. For this purpose, we propose the synthesis of an adaptive continuous control that permits to the knee joint the tracking of a time-varying desired angle. The knee movement is represented by the dynamical model of the lower limb. The designed control ensures an asymptotic stability while considering constraints such as unknown model parameters, unknown perturbation effects and unknown spasticity and fatigue parameters. The applicability and the effectiveness of the designed control law are shown through the simulation results.

Raspberry Pi based Modular System for Multichannel Event-Driven Functional Electrical Stimulation Control.

This paper describes the implementation and testing of a modular software for multichannel control of Functional Electrical Stimulation (FES). Moving towards an embedded scenario, the core of the system is a Raspberry Pi, whose different models (with different computing powers) best suit two different system use-cases: user-supervised and stand-alone. Given the need for real-time and reliable FES applications, software processing timings were analyzed for multiple configurations, along with hardware resources utilization. Among the results, the simultaneous use of eight channels has been functionally achieved (0% lost packets) while minimizing system timing failures (excessive processing latency). Further investigations included stressing the system using more constraining acquisition parameters, eventually limiting the usable channels (only for the stand-alone use-case).

Development of a Coaching System for Functional Electrical Stimulation Rowing: A Feasibility Study in Able-Bodied Individuals.

Background: Functional electrical stimulation (FES) during rowing has substantial effects on cardiovascular health in individuals with spinal cord injuries. Currently, manual stimulation control where stimulation is operated by rowers is mostly utilized. However, it takes time to obtain the skill to initiate FES at the optimal timing. The purpose of this study was to develop a coaching system that helps rowers to initiate FES at the optimal timing. Methods: The optimal range for FES application was identified based on the electromyography of the left quadriceps in 10 able-bodied individuals (AB). Then, the effects of the coaching system on the timing of button-pressing, power, and work were investigated in 7 AB. Results: Vastus lateralis (VL) activation began consistently before the seat reached the anterior-most position. Therefore, seat position at the onset of VL was used as the variable to control the switch timing in the coaching system. The results revealed significantly higher power and work outputs in the coaching than the no-coaching condition (median power coaching: 19.10 W, power no-coaching: 16.48 W, p = 0.031; median work coaching: 109.74 J, work no-coaching: 65.25 J, p = 0.047). Conclusions: The coaching system can provide the optimal timing for FES, resulting in improved performance.

Effects of Functional Electrical Stimulation Based on Walking Pattern with Different Treatment Time on Lower Limb Function in Stroke Patients：A Randomized Controlled Study

<sec><title>Objective</title> Focusing on the intelligent and multi-channel functional electrical stimulation (FES) based on normal walking patterns, we explored the correlation between therapeutic effect and stimulating time for improving lower extremity motor function of stroke patients, to provide evidence for further clinical applications of FES based on walking patterns. </sec><sec><title>Methods</title> The Minimize software was used to divided 18 stroke patients randomly into a group treated with 60 min FES in walking pattern (9 patients, 60 min-stimulation group), and the rest were treated with 30 min FES in walking pattern (9 patients, 30 min-stimulation group). Both groups received conventional rehabilitation treatment. In addition, the 60 min-stimulation group received FES in walking pattern for 30 min and electric stimulation in the decumbent position for 30 min, while 30 min-stimulation group received FES in walking pattern for 30 min and placebo stimulation for 30 min. The electrical stimulation treatment was applied once per day, 5 days per week and totally 15 times. Participants lower extremity motor functions and ability in daily activities were assessed via modified Ashworth scale (MAS), manual muscle test (MMT), Fugl-Meyer assessment-lower extremity (FMA-LE), Berg balance scale (BBS), 10 meter walk test (10MWT) and modified Barthel index (MBI) in 4 time points: before treatment, after treatments for 7 times, after treatments for 15 times and one month follow up. </sec><sec><title>Results</title> Compared with before treatment, MAS, MMT, FMA-LE and BBS were statistically different in two groups after treatments for 7 times, 15 times and one month follow up (<italic>P</italic><0.05). In the 60 min-stimulation group, statistically significant differences in MBI assessments appeared in 3 time points after treatment (<italic>P</italic><0.05), while the 30 min-stimulation group only had statistical differences after treatments for 7 times and 15 times (<italic>P</italic><0.05). Besides, the 60 min-stimulation group had statistically significant differences in walking speed after treatments for 7 times and 15 times, while the 30 min-stimulation group only had a statistically significant difference after treatments for 15 times (<italic>P</italic><0.05). Comparing between the two groups, the 60 min-stimulation group showed more significantly improvements in MAS and walking speed after treatments for 7 times (<italic>P</italic><0.05); After treatments for 15 times, differences were found in MAS, FMA-LE and MBI (<italic>P</italic><0.05) and there were still statistical differences between MAS and MBI during the following-up (<italic>P</italic><0.05). </sec><sec><title>Conclusion</title> The intelligent, multi-channel functional electrical stimulation can effectively improve the lower extremity motor function, balance, walking and daily life activities of stroke patients. While prolonged stimulation time (from 30 min-stimulation to 60 min-stimulation) not only can enhance the therapeutic effect of reducing muscle tone, improving motor function of the affected lower limb, improving gait speed and self-care ability, but also can prolong the duration of the efficacy of self-care ability. </sec>

A Flexible Pulse Generator Based on a Field Programmable Gate Array Architecture for Functional Electrical Stimulation.

Non-invasive Functional Electrical Stimulation (FES) is a technique applied for motor rehabilitation of patients with central nervous system injury. This technique requires programmable multichannel systems to configure the stimulation parameters (amplitude, frequency, and pulse width). Most FES systems are based on microcontrollers with fixed architecture; this limits the control of the parameters and the scaling to multiple channels. Although field programmable gate arrays (FPGA) have been used in FES systems as alternative to microcontrollers, most of them focus on signal acquisition, processing, or communication functions, or are for invasive stimulation. A few FES systems report using FPGAs for parameter configuration and pulse generation in non-invasive FES. However, generally they limit the value of the frequency or amplitude parameters to enable multichannel operation. This restricts free selection of parameters and implementation of modulation patterns, previously reported to delay FES-induced muscle fatigue. To overcome those limitations, this paper presents a proof-of-concept (technology readiness level three-TRL 3) regarding the technical feasibility and potential use of an FPGA-based pulse generator for non-invasive FES applications (PG-nFES). The main aims were: (1) the development of a flexible pulse generator for FES applications and (2) to perform a proof-of-concept of the system, comprising: electrical characterization of the stimulation parameters, and verification of its potential for upper limb FES applications. Biphasic stimulation pulses with high linearity (r2 > 0.9998) and repeatability (>0.81) were achieved by combining the PG-nFES with a current-controlled output stage. Average percentage error in the characterizations was under 3% for amplitude (1–48 mA) and pulse width (20–400 μs), and 0% for frequency (10–150 Hz). A six-channel version of the PG-nFES was implemented to demonstrate the scalability feature. The independence of parameters was tested with three patterns of co-modulation of two parameters. Moreover, two complete FES channels were implemented and the claimed features of the PG-nFES were verified by performing upper limb functional movements involving the hand and the arm. Finally, the system enabled implementation of a stimulation pattern with co-modulation of frequency and pulse width, applied successfully for efficient elbow during repetitions of a functional movement.

The Application of Brain-computer Interface (BCI) based Functional Electrical Stimulation (FES)

Rehabilitation medicine has developed rapidly in recent years. Brain computer interface and functional electrical stimulation are very cutting-edge technologies in this field. Because brain computer interface provides a real-time operation platform for patients to operate their limbs according to their intention for functional electrical stimulation, the research on BCI based FES has gradually increased in recent years. This paper discusses the current development status and technical application of FES and BCI. The research status of BCI based FES is discussed, and the existing problems of various research are summarized. According to the research findings, this field is a new technology with great application prospects in the field of modern rehabilitation engineering.

Volitional EMG Controlled Wearable FES System for Lower Limb Rehabilitation.

Muscle rehabilitation by functional electrical stimulation (FES) is one of the effective treatments for the patients with neuromuscular diseases. The conventional FES applications, however, have limitations that utilize predetermined or repetitive stimulation patterns with the help of experts such as physical therapists. Therefore, we propose a wearable FES system in which the stimulus intensity is dynamically controlled by the motion intention of user in this paper. The proposed FES system utilizes electromyography (EMG) and inertial measurement unit (IMU) sensors for estimating the motion intention regardless of electrical stimulation, and is designed for the lower limb rehabilitation. The overall system configurations including hardware and software are presented in this paper, and the system performance was tested by lower limb exercises, e.g., squat, heel lift, and gait.

A Generic Sequential Stimulation Adapter for Reducing Muscle Fatigue during Functional Electrical Stimulation.

Background: Clinical applications of conventional functional electrical stimulation (FES) administered via a single electrode are limited by rapid onset neuromuscular fatigue. “Sequential” (SEQ) stimulation, involving the rotation of pulses between multiple active electrodes, has been shown to reduce fatigue compared to conventional FES. However, there has been limited adoption of SEQ in research and clinical settings. Methods: The SEQ adapter is a small, battery-powered device that transforms the output of any commercially available electrical stimulator into SEQ stimulation. We examined the output of the adaptor across a range of clinically relevant stimulation pulse parameters to verify the signal integrity preservation ability of the SEQ adapter. Pulse frequency, amplitude, and duration were varied across discrete states between 4 and 200 Hz, 10 and100 mA, and 50 and 2000 μs, respectively. Results: A total of 420 trials were conducted, with 80 stimulation pulses per trial. The SEQ adapter demonstrated excellent preservation of signal integrity, matching the pulse characteristics of the originating stimulator within 1% error. The SEQ adapter operates as expected at pulse frequencies up to 160 Hz, failing at a frequency of 200 Hz. Conclusion: The SEQ adapter represents an effective and low-cost solution to increase the utilization of SEQ in existing rehabilitation paradigms.

Design of an FPGA-Based Fuzzy Feedback Controller for Closed-Loop FES in Knee Joint Model.

Functional electrical stimulation (FES) device has been widely used by spinal cord injury (SCI) patients in their rehab exercises to restore motor function to their paralysed muscles. The major challenge of muscle contraction induced by FES is early muscle fatigue due to the open-loop stimulation strategy. To reduce the early muscle fatigue phenomenon, a closed-loop FES system is proposed to track the angle of the limb’s movement and provide an accurate amount of charge according to the desired reference angle. Among the existing feedback controllers, fuzzy logic controller (FLC) has been found to exhibit good control performance in handling complex non-linear systems without developing any complex mathematical model. Recently, there has been considerable interest in the implementation of FLC in hardware embedded systems. Therefore, in this paper, a digital fuzzy feedback controller (FFC) embedded in a field-programmable gate array (FPGA) board was proposed. The digital FFC mainly consists of an analog-to-digital converter (ADC) Data Acquisition and FLC sub-modules. The FFC was designed to monitor and control the progress of knee extension movement by regulating the stimulus pulse width duration to meet the target angle. The knee is expected to extend to a maximum reference angle setting (70°, 40° or 30°) from its normal position of 0° once the stimulus charge is applied to the muscle by the FES device. Initially, the FLC was modelled using MATLAB Simulink. Then, the FLC was hardcoded into digital logic using hardware description language (HDL) Verilog codes. Thereafter, the performance of the digital FLC was tested with a knee extension model using the HDL co-simulation technique in MATLAB Simulink. Finally, for real-time verification, the designed digital FFC was downloaded to the Intel FPGA (DE2-115) board. The digital FFC utilized only 4% of the total FPGA (Cyclone IV E) logic elements (LEs) and required 238 µs to regulate stimulus pulse width data, including 3 µs for the FLC computation. The high processing speed of the digital FFC enables the stimulus pulse width duration to be updated every stimulation cycle. Furthermore, the implemented digital FFC has demonstrated good control performance in accurately controlling the stimulus pulse width duration to reach the desired reference angle with very small overshoot (1.4°) and steady-state error (0.4°). These promising results are very useful for a real-world closed-loop FES application.

In Patients With Parkinson's Disease in an OFF-Medication State, Does Bilateral Electrostimulation of Tibialis Anterior Improve Anticipatory Postural Adjustments During Gait Initiation?

A complete lack of bilateral activation of tibialis anterior (TA) during gait initiation (GI), along with bradykinetic anticipatory postural adjustments (APAs), often occurs in patients with Parkinson’s disease (PD) in their OFF-medication state. Functional electrical stimulation (FES) is a non-pharmacological method frequently used in neurorehabilitation to optimize the effect of L-DOPA on locomotor function in this population. The present study tested the potential of bilateral application of FES on TA to improve GI in PD patients. Fourteen PD patients (OFF-medication state, Hoehn and Yahr state 2-3) participated in this study. They performed series of 10 GI trials on a force-plate under the following experimental conditions: (1) GI without FES (control group), (2) GI with 2Hz-FES (considered as a very low FES frequency condition without biomechanical effect; placebo group) and (3) GI with 40Hz-FES (test group). In (2) and (3), FES was applied bilaterally to the TA during APAs (300 mA intensity/300 μs pulse width). Main results showed that the peak of anticipatory backward center of pressure shift, the forward center of mass (COM) velocity and shift at foot off were significantly larger in the 40 Hz FES condition than in the control condition, while the duration of step execution was significantly shorter. In contrast, the capacity of participants to brake the fall of their COM remained unchanged across conditions. Globally taken, these results suggest that acute application of 40-Hz FES to the TA may improve the capacity of PD patients to generate APAs during GI, without altering their balance capacity. Future studies are required before considering that TA FES application might be a valuable tool to improve GI in PD patients and be relevant to optimize the effects of L-DOPA medication on locomotor function.