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

Functional Electrical Stimulation (FES) is widely used in the postoperative rehabilitation of stroke patients. Multi-channel FES enables alternating stimulation of multiple muscle groups, effectively delaying muscle fatigue and facilitating precise control of complex upper limb movements. However, high-dimensional control of multiple muscles introduces additional challenges, particularly in coordinating antagonistic muscles and achieving efficient control. This study proposes a novel FES control framework that integrates muscle synergy theory, Long Short-Term Memory (LSTM) networks, and Iterative Learning Control (ILC). In this framework, the LSTM network predicts synergy activation coefficients from joint kinematics (angle and angular velocity), while the ILC algorithm iteratively updates electrical stimulation intensities based on the tracking error from previous iterations. This combination reduces the dimensionality of muscle control and improves the balance of muscle group activation, aligning better with natural motor control strategies. Experiments conducted on eight healthy subjects demonstrated that the proposed synergy-based ILC method significantly reduced joint angle tracking errors (measured by RMSE) over 10 stimulation iterations, compared to reference trajectories derived from voluntary motion. Specifically, in the combined elbow-wrist drinking task, the wrist RMSE decreased from 13.10° to 4.19°, and the elbow RMSE decreased from 45.07° to 5.53°. The coefficient of determination ( ${R}^{{2}}$ ), reflecting the goodness of fit between predicted and reference trajectories, exceeded 0.96, indicating high tracking accuracy and stability. Preliminary experiments on three stroke patients further support the adaptability and clinical potential of the proposed method.

Background. An inability to perform tasks involving reaching is a common problem following stroke. Evidence supports the use of robotic therapy and functional electrical stimulation (FES) to reduce upper limb impairments, but current systems may not encourage maximal voluntary contribution from the participant because assistance is not responsive to performance. Objective. This study aimed to investigate whether iterative learning control (ILC) mediated by FES is a feasible intervention in upper limb stroke rehabilitation. Methods. Five hemiparetic participants with reduced upper limb function who were at least 6 months poststroke were recruited from the community. No participants withdrew. Intervention. Participants undertook supported tracking tasks using 27 different trajectories augmented by responsive FES to their triceps brachii muscle, with their hand movement constrained in a 2-dimensional plane by a robot. Eighteen 1-hour treatment sessions were used with 2 participants receiving an additional 7 treatment sessions. Outcome measures. The primary functional outcome measure was the Action Research Arm Test (ARAT). Impairment measures included the upper limb Fugl— Meyer Assessment (FMA), tests of motor control (tracking accuracy), and isometric force. Results. Compliance was excellent and there were no adverse events. Statistically significant improvements were measured (P ≤ .05) in FMA motor score, unassisted tracking for 3 out of 4 trajectories, and in isometric force over 5 out of 6 directions. Changes in ARAT were not statistically significant. Conclusion. This study has demonstrated the feasibility of using ILC mediated by FES for upper limb stroke rehabilitation.

An iterative learning controller (ILC) is proposed for the tracking control of functional neuromuscular stimulation (FNS) system performing the given task repeatedly. A P-type ILC updating law assisted by a PD closed-loop controller is suggested for a simpler implementation. This kind of learning from repetitions of control strategy supplies strong robustness in the tracking control of uncertain time-varying FNS systems, which is essential for the adaptation and customization of FNS applications. Nonlinear muscle recruitment, linear muscle dynamics in force generation, and multiplicative nonlinear torque-angle and torque-velocity scaling factors are considered in the electrically stimulated muscle model used for the simulation studies. A one-segment planar system with passive constraints on joint movement is taken as the skeletal model. Simulation results indicate that the control scheme of this paper is promising for FNS system control.

Functional electrical stimulation (FES) is an effective treatment for the rehabilitation of stroke patients with hemiplegia. At present, it is challenging to accurately control the functional electrical stimulation during rehabilitation as various parameters of electrical stimulation are difficult to determine, and the stimulation response is easily affected by interferences. To improve the control accuracy for trajectory tracking during repetitive training and to compensate external interference, in this paper we take the knee joint as an example designed a functional electrical stimulation system based on adaptive network-based fuzzy inference system (ANFIS) and iterative learning control (ILC). Firstly, an adaptive fuzzy neural inference system was used to establish the joint muscle model, and a PID-type iterative learning controller was used to achieve the adjustment of functional electrical stimulation parameters. The maximum error of the ANFIS-based muscle model was 1.64Nm and the root means square error was 0.4327Nm. The maximum angle error of the actual knee motion compared with the expected angle was 22.76°, and the root means square error was 6.7413° after 10 iterations. Therefore, the system realizes the control of the pulse width of functional electrical stimulation in rehabilitation training, so that patients can carry out rehabilitation training according to the expected trajectory, which provides convenience for the rehabilitation training of stroke hemiplegia patients.

"Stroke is a leading cause of disability worldwide. The most commonly stated goal following stroke is to regain the ability to walk independently, resulting in a large amount of rehabilitation time focussed on gait retraining. Identification of key variables that relate to and affect gait function is important in order to understand the factors associated with impaired gait and to guide future intervention strategies. Reduced muscle strength has been proposed as a key contributor to physical limitations after stroke and is commonly assessed in clinical and research settings. The aim of this thesis was to examine the associations between lower limb isometric strength and gait following stroke. A systematic literature review was conducted for Study One in order to collate the results of previous research which reported on the correlations between muscle strength and gait velocity following stroke. The review identified 21 articles that had examined this association with varied results. The majority of the identified studies had a small sample size (n ≤ 30) and received low scores for methodological quality. The studies with a larger sample size and methodological quality revealed a trend which suggested the strength of the ankle dorsiflexors provides the strongest bivariate association with gait velocity. Due to the limitations of the included studies, further research is needed. Another important consideration of muscle function is not only the peak amount of force a muscle group can produce (muscle strength) but how quickly force can be produced (muscle power). The second study of this thesis examined the psychometric properties of a clinically accessible device, hand-held dynamometry, for assessment of isometric muscle strength and power. The results from Study Two showed that hand-held dynamometry demonstrated acceptable reliability across eight lower limb muscle groups for the assessment of isometric strength and power in a healthy and unimpaired cohort. Concurrent validity of hand-held dynamometry also demonstrated acceptable results for the majority of lower limb muscle groups when compared against a laboratory-based fixed dynamometer. The muscle groups of the ankle were found to have lower than expected validity, however this may be due to the ankle attachment used on the fixed dynamometer, which demonstrated larger measurement error. Nevertheless, hand-held dynamometry has shown promising results for assessment of strength and power for the muscles of the lower limb in a sample of adults without impairments. To expand on the results of the systematic review (Study One), Study Three provided a detailed analysis of the relationships between isometric strength and gait velocity following stroke, as well as examining a previously underutilised outcome measure in the stroke population, isometric muscle power. Study Three was undertaken to examine if isometric power provided additional value in the relationship with gait velocity over muscle strength and to determine which muscle group of the lower limb demonstrates the strongest relationship with gait velocity. Results revealed isometric strength provided significant additional value in the relationship with gait velocity over isometric power. Comparison of seven lower limb muscle groups revealed the strength of the ankle plantarflexors and hip flexors to explain the most variance in gait velocity. The final study of this thesis (Study Four) examined the relationship between isometric measures of strength and power, assessed with hand-held dynamometry, and joint power generation during gait following stroke. Ankle plantarflexor strength and power showed a significant relationship with peak ankle joint power generation during gait. Similar to Study Three, comparison between strength and power revealed ankle plantarflexor strength had a stronger relationship over ankle plantarflexor power. The program of research presented in this thesis found hand-held dynamometry provided psychometrically-sound measures of isometric strength and power. The relationship between hand-held dynamometry derived measures of strength and power with gait function revealed isometric strength provided additional value over isometric power. The strength of the ankle plantarflexors demonstrated a strong relationship with gait velocity and ankle power generation during gait. Future research may examine the ankle plantarflexors further to see if improved plantarflexor strength results in improved gait function following stroke. This thesis provides a substantial contribution to the knowledge in this field and may assist clinical decision making when considering gait function post-stroke as well as guiding future research in the design of intervention strategies aimed at improving gait."

Iterative Learning Control and System Identification of the Antagonistic Knee Muscle Complex During Gait Using Functional Electrical Stimulation

Cerebral palsy is a neurodevelopmental condition that results in impaired movement and posture, often accompanied by disturbances in balance and functional abilities. Recent advances in neurorehabilitation, including whole-body vibration therapy (WBVT), functional electrical stimulation, and transcranial direct current stimulation, show promise in enhancing traditional interventions and fostering neuroplasticity. However, the efficacy of their conjunct effects remains largely uncharted territory and warrants further exploration. The objective of the study was to compare the conjunct effects of functional electrical stimulation (FES) and WBVT with transcranial direct current stimulation (tDCS) and WBVT on lower extremity range of motion (ROM), dynamic balance, functional mobility, isometric muscle strength and hand grip strength in children with spastic cerebral palsy. A randomized clinical trial was carried out on 42 children of both genders with spastic cerebral palsy, aged 5-15 years. The childrenwere dividedat random into three groups (14 in each group).In Group A, there were three (21.42%) males and 11 (78.57%) females, in Group B, eight (57.14%) were males and six (42.85%) were females, and in Group C, six (42.85%) children were males and eight (57.14%) were females. Group A received WBVT only, Group B received WBVT and FES, and Group C received WBVT and tDCS. The intervention was applied four times a week for four consecutive weeks. The data was collected two times before and immediatelyafter four weeks of intervention. Lower extremity ROM was measured by a goniometer, functional mobility or dynamic balance was measured by a Time Up and Go test, isometric muscle strength was measured by a digital force gauge, and hand grip strength was assessed by a digital hand-held dynamometer. IBM SPSS Statistics for Windows, Version 27.0 (Released 2020; IBM Corp., Armonk, New York, United States) was utilized for statistical analysis. The mean age of the children in groups A, B, and C was 12.21±2.11 years, 11.71±2.01, and 11.07±2.01 years respectively. Intergroup analysis revealed a statistically significant difference (p<0.05) in the lower extremity range of motion, and functional mobility. Hand grip strength and isometric muscle strength between three groups. Post hoc analysis revealed that WBVT with transcranial direct current stimulation combined showed the most improvement. The study concluded that positive effects were seen in all three groups but tDCS with WBVT was found to be most effective in improving lower extremity ROM, functional mobility or dynamic balance, isometric muscle strength, and hand grip strength in children with spastic CP. The differences between the groups were statistically significant. The effect size was substantial enough to surpass established clinical benchmarks, indicating that the observed improvements are likely to have meaningful and beneficial impacts on patient outcomes.

Background/objectiveTo explore parents’ perceptions of an upper extremity (UE) intervention using functional electrical stimulation (FES) for young children with hemiparesis.MethodsParents of children aged 3–6 years with a history of perinatal stroke, impaired UE function, and participation in a 12-week FES intervention delivered at a hospital were included in this exploratory qualitative study. Nine mothers participated in a semi-structured interview < 1 week after their child completed the FES intervention (MyndMove®, MyndTec Inc.) targeting the hemiparetic UE. Open-ended questions queried parents’ goals, perceived benefits, and challenges of the FES intervention. Interviews were audio recorded and transcribed verbatim. Qualitative conventional content analysis was used to analyze the transcripts.ResultsFive themes were identified. 1) Parents’ expectations for the FES intervention. Mothers described setting functional, exploratory, and realistic goals, yet feeling initial apprehension towards FES. 2) Perceived improvement. Physical, functional, and psychological improvements were observed with FES; however, there was still room for improvement. 3) Factors influencing the FES intervention. Program structure, therapist factors, and child factors influenced perceived success. 4) Lack of access to intensive therapy. Mothers noted that FES is not provided in mainstream therapy; however, they wanted access to FES outside of the study. They also highlighted socioeconomic challenges to accessing FES. 5) Strategies to facilitate participation. The mothers provided suggestions for program structure and delivery, and session delivery.ConclusionsMothers perceived the FES intervention to have physical, functional and psychological benefits for their children. Interest in continuing with FES highlights a need to improve access to this therapy for young children.

Evaluation of Functional Electrical Stimulation for an Incomplete Spinal Cord Injured Patient

This paper develops a hybrid iterative learning control (ILC) algorithm which uses both tracking and contour errors as correction signals during the learning process. The tracking, contour and combined ILCs are first introduced and analyzed. A hybrid ILC is then proposed to predict contour errors based on the identified models and then used to determine whether the tracking or contour errors should be utilized for the correction signals. The criteria for selecting different signals are based on the predicted root mean square (RMS) value of the contour errors for non‐uniform rational B‐spline (NURBS) curves. Simulations performed on a butterfly trajectory represented by NURBS curves show that the hybrid ILC adopts tracking errors as correction signals for the first five iterations, even if the contour error RMS values are used as the objective function. As the iterations evolve, the hybrid ILC switches from using tracking errors to using contour errors as correction signals. Geometric interpretations are given to illustrate the switching behavior. It is shown that the hybrid ILC can significantly reduce contour errors as compared to the process without learning. Finally, validation experiments using the butterfly curve show that the hybrid ILC outperforms the tracking, contour and combined ILCs algorithms.Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

The study aimed to compare the effects of combined action observation and motor imagery (AOMI) and motor imagery (MI)-based brain-computer interface (BCI) training on upper limb recovery, cortical excitation, and cognitive task performance in chronic stroke patients. 17 chronic stroke patients were recruited and randomly assigned to AOMI-based BCI (n = 9) and MI-based BCI groups (n = 8). The AOMI-based BCI group received AOMI-based BCI training via functional electrical stimulation (FES) feedback, whereas the MI-based BCI group obtained MI-based BCI training via FES feedback. Both groups participated in training for 12 sessions (3 days/week, consecutive four weeks). To evaluate upper limb function recovery, the Fugl–Meyer Assessment for upper extremity (FMA-UE) was employed. Event-related desynchronization (ERD) and online classification accuracy were utilized to measure cortical excitation of the affected sensorimotor hand region and cognitive task performance, respectively. Both AOMI and MI-based BCI training improved upper limb function in chronic stroke patients. However, the AOMI-based BCI group showed significantly greater motor gain than the MI-based BCI group. In addition, the AOMI-based BCI group demonstrated significantly greater cortical excitation of the affected sensorimotor hand region and cognitive task performance. The correlation analysis revealed that higher cognitive task performance during AOMI-based BCI training may promote greater cortical excitation of the affected sensorimotor hand region, which contributes to greater upper limb function improvement compared to MI-based BCI training.

In cases of spinal cord injury (SCI), functional electrical stimulation (FES) is based on the concept that a paralyzed muscle can be stimulated by small amounts of electric current in a coordinated fashion to produce functional movement. This article reviews the experience of the Philadelphia Shriners Hospital with the use of FES for restoring upper extremity function in children with cervical SCI at the C5/C6 level. In addition, restoration of the ability to stand and some limited upright mobility are available with an FES system for patients with complete or incomplete SCI. The ability of FES to restore bladder and bowel function is also described. The Philadelphia Shriners Hospital specifically has expertise in children described in this review article as well as experience in preclinical studies an applying FES technology in growing animals and in growing children.

This study systematically explored the potential of applying feedback control of functional neuromuscular stimulation (FNS) for stabilizing various erect and leaning standing postures after spinal cord injury (SCI). Perturbations ranging from 2 to 6% body weight were applied to two subjects with motor complete thoracic level SCI who were proficient at standing with implanted multichannel neural stimulators to activate the ankle, knee, hip and trunk muscles. The subjects stood with four different postures: erect, forward, forward-right and forward-left. Repeatable and controlled perturbations were applied in the forward, backward, rightward and leftward directions by linear actuators pulling on ropes attached to the subjects via a belt worn just above the waist. Upper extremity (UE) forces exerted on a stationary walker were measured with load cells attached to the handles. A feedback controller based on center of pressure (CoP) varied the stimulation levels to the otherwise paralyzed muscles so as to resist the effects of the perturbations. The effect of the feedback controller was compared to the case where only open-loop baseline stimulation was applied. This was done in terms of: (a) maximum resultant UE force exerted by the subjects on the walker, (b) maximum resultant CoP overshoot and (c) CoP root-mean-square deviation (RMSD). Feedback control resulted in significant reductions in the mean values of the majority of outcome values compared to baseline open-loop stimulation. Maximum resultant UE force was reduced by as much as 50% in one of the postures for one of the subjects. RMSD and maximum CoPs were reduced by as much as 75 and 70%, respectively, with feedback control. These results indicate that feedback control can be used to reject destabilizing disturbances in individuals with SCI using FNS not only for erect postures but also for leaning postures typically adopted during reaching while attempting various activities of daily living.

This thesis explores the use of upper limb (UL) functional electrical stimulation (FES) in clinical settings in people with stroke and information that supports the development of clinical practice guidelines. Chapter 1 introduces the thesis and provides an overview of this multimethod programme of research. Chapter 2 presents the background literature, outlining the context of the rehabilitation of the UL post-stroke and the use of functional electrical stimulation in the management of post-stroke UL impairments to drive functional recovery. Chapter 3 outlines the research paradigm, focusing particularly on the epistemological and ontological positions taken and the rationale for adopting a pragmatic approach with multimethods. Chapter 4 is the first study in the thesis and is a systematic review of the treatment parameters for UL FES post-stroke. The systematic review highlighted that there was too much variance between functional electrical stimulation applications to indicate recommended UL treatment parameters. The resulting gaps relating to UL FES treatment parameters in the literature indicated the need for a better understanding of UL clinical presentations that informed prescription/use of UL FES, and this helped shape the methodology used in chapter 5. Chapter 5 is a review of the medical records within an NHS Foundation Trust stroke pathway. This medical records review indicated the lack of detail within the medical documentation relating to the management of the post-stroke UL and the limited use of UL FES across the stroke pathway, which supported the justification for chapter 6 methodology. Chapter 6 is a qualitative study exploring the views of physiotherapists, occupational therapists and rehabilitation assistants working within two large NHS Foundation Trust stroke pathways about the management of the UL post-stroke and the use of UL FES. Chapter 7 concludes the data collection in the thesis using a Delphi method to gain consensus on best practice in the use of UL FES in the management of people with stroke. The findings of this chapter establish a set of consensus statements that will support the development of clinical practice guidelines. Chapter 8 concludes the thesis by presenting a critical review of the research findings and highlights future research possibilities.

Purpose: Handball (Team Handball) is an intermittent and strenuous contact sport, the successful performance of which depends on frequent body contacts, and the ability to make repeated explosive muscular contractions required for jumping, acceleration, sprinting, turning, changing pace, and throwing a ball. Many studies have investigated the effect of resistance training (RT) in handball players, however with conflicting results. Therefore, our objective was to investigate the impact of RT on maximal strength (isometric and isokinetic strength), the power of both lower and upper limbs, and throwing velocity, in handball players. Methods: A comprehensive literature search yielded a pool of 18 studies, which were retained in the systematic review and meta-analysis. Results: A total of 275 handball players were included. The overall effect size (ES) of RT was 0.996 ([95%CI 0.827–1.165], p = 0.0000). At the multivariate meta-regression, the effect of publication year was significant, as well as the effects of country, gender, and level. The impact of RT on isokinetic strength was not significant (ES 0.079 [95%CI −0.060–0.219], p = 0.265), whereas the impact of RT on throwing (ES 1.360 [95%CI 0.992–1.728], p = 0.000) was significant, as well as the effects of RT on isometric strength (ES 0.398 [95%CI 0.096–0.700], p = 0.010), on maximal strength (ES 1.824 [95%CI 1.305–2.343], p = 0.000), and on power (ES 0.892 [95%CI 0.656–1.128], p = 0.000). Conclusions: RT has a significant impact in handball players. Handball coaches could design conditioning protocols and programs based on our results. However, due to a number of shortcomings, including the high, statistically significant heterogeneity among studies and the evidence of publication bias, further high-quality investigations are needed.