Neural ODE–driven safe model predictive control for functional electrical stimulation cycling

Rationale and design of a randomized controlled clinical trial of functional electrical stimulation cycling in persons with severe multiple sclerosis.

IntroductionFunctional electrical stimulation cycling has various health benefits, butthe mechanical power output and efficiency are very low compared tovolitional muscle activation. Stimulation with variable frequency showedsignificantly higher power output values in experiments with a kneedynamometer. The aim of the present work was to compare stochasticmodulation of inter-pulse interval to constant inter-pulse intervalstimulation during functional electrical stimulation cycling.MethodsSeventeen able-bodied subjects participated (n = 17).Quadriceps and hamstring muscle groups were stimulated with two activationpatterns: P1-constant frequency, P2-stochastic inter-pulse interval. Poweroutput was measured on functional electrical stimulation ergometer.ResultsOverall, mean power output with the stochastically modulated pattern P2 waslower than with P1 (12.57 ± 3.74 W vs. 11.44 ± 3.81 W, P1 vs. P2,p = 0.022), but no significant differences during thefirst 30 s and the last 30 s were observed.ConclusionsThis study showed that stimulation strategies that use randomized modulationof inter-pulse intervals can negatively affect power output generationduring functional electrical stimulation cycling. To minimise voluntarycontractions, power measurement and assessment should be focused on theperiods where only the quadriceps are stimulated.

Evaluating functional electrical stimulation (FES) cycling on cardiovascular, musculoskeletal and functional outcomes in adults with multiple sclerosis and mobility impairment: A systematic review

Functional electrical stimulation (FES) cycling ergometer has been utilized in recent decades for rehabilitation by sequentially stimulating the large leg-actuating muscles of paralyzed leg muscles to produce cyclical leg motion. A number of studies reported physiological adaptations after regular FES-cycling exercise (FESCE) training in subjects with spinal cord injury, stroke, cerebral palsy and other conditions. This article provides a comprehensive overview of general aspects of FES cycling systems and clinical applications of FESCE. The studies cited in this article provide supportive findings for the potential clinical efficacy of FESCE for reducing the risk of secondary medical complications in subjects with paralysis. The potential therapeutic benefits of FESCE include conditioning the cardiopulmonary, muscular, and skeletal systems, and improving other physiological and psychological performances. Our recent pilot study also indicated that the decrease of leg spasticity in subjects with cerebral palsy is one of the acute effects of FESCE. In conclusion, we recommend that FESCE is of benefit in a variety of aspects to improve the general condition and to prevent deterioration in subjects with central neurological impairments.

Background: People with spinal cord injuries (SCIs) often have trouble remaining active because of paralysis. In the past, exercise recommendations focused on the non-paralyzed muscles in the arms, which provides limited benefits. However, recent studies show that electrical stimulation can help engage the paralyzed extremities, expanding the available muscle mass for exercise. Methods: The authors provide an evidence-based approach using expertise from diverse fields, supplemented by evidence from key studies toward the management of electrical stimulation therapies in individuals with SCIs. Literature searches were performed separately using the PubMed, Medline, and Google Scholar search engines. The keywords used for the searches included functional electrical stimulation cycling, hybrid cycling, neuromuscular electrical stimulation exercise, spinal cord injury, cardiovascular health, metabolic health, muscle strength, muscle mass, bone mass, upper limb treatment, diagnostic and prognostic use of functional electrical stimulation, tetraplegic hands, and hand deformities after SCI. The authors recently presented this information in a workshop at a major rehabilitation conference. Additional information beyond what was presented at the workshop was added for the writing of this paper. Results: Functional electrical stimulation (FES) cycling can improve aerobic fitness and reduce the risk of cardiovascular and metabolic diseases. The evidence indicates that while both FES leg cycling and neuromuscular electrical stimulation (NMES) resistance training can increase muscle strength and mass, NMES resistance training has been shown to be more effective for producing muscle hypertrophy in individual muscle groups. The response to the electrical stimulation of muscles can also help in the diagnosis and prognosis of hand dysfunction after tetraplegia. Conclusions: Electrical stimulation activities are safe and effective methods for exercise and testing for motor neuron lesions in individuals with SCIs and other paralytic or paretic conditions. They should be considered part of a comprehensive rehabilitation program in diagnosing, prognosing, and treating individuals with SCIs to improve function, physical activity, and overall health.

Children who experience spinal cord injuries (SCI) may develop many complications, including loss of bone mass, osteoporosis, and pathological fractures. Additionally, patients with SCI often rate their quality of life as poor compared to non-injured peers. We examined the effect of functional electrical stimulation (FES) cycle exercise on bone mineral density (BMD) and quality of life (QOL) in six patients ranging in age from 9 to 20 years. BMD was determined using Dual X-ray Absorptiometry scans, and QOL was measured using the Pediatric Quality of Life Inventory (PedsQL™ 4.0). While patients experienced difficulty in attending sessions consistently, we found a tendency toward improved BMD and QOL associated with the number of months using the FES cycles. In addition, a positive relation was seen between improved BMD and the total number of cycling sessions, as well as between the final rating of QOL and time from injury. FES cycle exercise has the potential to increase BMD, possibly leading to a decrease in pathologic fractures, as well as to improve QOL, in children and adolescents with SCI. Further investigation is warranted on a larger population of children with SCI in order to establish the full benefits of FES cycle exercise.

Motorized functional electrical stimulation (FES) cycling has been demonstrated to have numerous health benefits for individuals suffering from neurological disorders. FES-cycling is usually designed to track the desired trajectories in real time. However, there are input delays between the exertion of the stimulation and the corresponding muscle contraction that potentially destabilize the system and undermine training efforts. Meanwhile, muscle fatigue gives rise to a time-varying input delay and decreased force. Moreover, switching between FES and motor control can be chattering and destabilizing owing to the high frequency. This article constructs Lyapunov-Krasovskii functionals to analyze the stability and robustness of the nonlinear cycling system with time-varying input delay. A new average dwell time condition is then provided to ensure the input-to-state stability of the considered systems. Finally, numerical simulations are illustrated to verify the effectiveness of the developed controller.

Rehabilitation robotics and functional electrical stimulation (FES) are two promising methods of rehabilitation for people with neurological disorders. In motorized FES cycling, both the rider and the motorized cycle must be controlled for cooperative human-machine interaction. While rehabilitation goals vary widely, FES cycling traditionally rejects rider disturbances to accomplish cadence and power tracking; however, this paper ensures that the cycle accommodates the rider without rejecting rider disturbances as a means to promote function and strength recovery while ensuring rider safety. A cadence and admittance controller are developed to activate the cycle’s electric motor and the rider’s leg muscles through FES when kinematically efficient. Using a single set of combined cycle-rider dynamics, a Lyapunov-like switched systems analysis is conducted to conclude global exponential cadence tracking. A subsequent passivity analysis is conducted to show the admittance controller is passive with respect to the rider. For a desired cadence of 50 RPM, preliminary experiments on one able-bodied participant and one participant with spina bifida demonstrate tracking errors of −0.07±2.59 RPM and −0.20±3.86 RPM, respectively.

Objective To understand the progression in parameters of functional electrical stimulation (FES) cycling dosage (including duration, velocity, stimulation amplitudes, power output), and the resulting changes in muscle mass early after acute spinal cord injury (SCI). Methods Three participants, 24–38 years old, with neurological injury level C4–T4, severity AIS (American Spinal Injury Association Impairment Scale) A–C, started FES cycling 16–20 days post injury while admitted at a level-1 trauma center in Canada, and continued for 8–13 weeks in a rehabilitation hospital. They performed three sessions/week of 15–45 min FES cycling, supine or sitting. FES parameters, cycling performance, and muscle cross-sectional area (CSA) in thighs and calves were measured every 2 weeks. Results Progression in power output, but not in session duration, was limited in two participants who experienced stimulation-associated referred pain or apprehension, requiring limitation of stimulation amplitudes for up to 65 days after the start of FES cycling. Participants started with 15 min cycling at 20 RPM with no resistance (0 W), and progressed to 30–45 min at 30 RPM producing 8.8–19.0 W average power/session after 2–3 months. Initially, muscle CSA decreased in all 3 participants (up to 16% after 6 weeks), and recovered later after a variable period of FES cycling (up to 16% at 13.3 weeks). Conclusion Progression of FES cycling in the first 3 months after injury required a highly individualized approach, guided by participant response, rather than standardized increments in stimulation intensity or duration. Changes in muscle CSA did not always correspond with the dose of FES cycling.

Functional electrical stimulation (FES)-assisted cycling may reduce perceived effort by lowering the required motor command compared to voluntary cycling. While benefits on effort perception have been shown during walking in stroke and multiple sclerosis patients, its effectiveness during cycling in stroke rehabilitation remains unproven. Thus, this work aimed to test the effect of functional electrical stimulation-assisted cycling on stroke patients’ perception of effort (primary aim) in a randomized controlled study design. In an exploratory way, this work also aimed to examine the effect of FES-assisted cycling on cerebral blood flow and cognitive performance (exploratory aims) in a subsample. Fifteen post-stroke patients completed functional electrical stimulation-assisted (Kurage, Lyon, France) and traditional cycling sessions separated by 72 h. Perceived effort, cardio, and cerebrovascular parameters were monitored during exercise. Cognitive performance was assessed before and after each session. Qualitative data were reported after both sessions. Patients reported a lower perceived effort during functional electrical stimulation-assisted cycling than traditional cycling. Both sessions increased heart rate, end-tidal CO2, cardiac output, and cerebral artery blood flow velocity, with higher blood lactate levels after functional electrical stimulation-assisted cycling. Traditional and functional electrical stimulation-assisted cycling positively impacted cognitive performance, with more pronounced improvements observed in the FES condition. Traditional and functional electrical stimulation-assisted cycling induced similar increased cardio and cerebrovascular responses. However, patients perceived functional electrical stimulation-assisted cycling as less effortful than traditional cycling. As effort is a barrier to regular exercise engagement and adherence, these results are promising for implementing functional electrical stimulation-assisted cycling in stroke patients’ rehabilitation.

The Force–Velocity Relationship of Paralyzed Quadriceps Muscles During Functional Electrical Stimulation Cycling

The aim of this study is to investigate the effects of an integrated gait rehabilitation training based on Functional Electrical Stimulation (FES)-cycling and overground robotic exoskeleton in a group of seven complete spinal cord injury patients on spasticity and patient-robot interaction. They underwent a robot-assisted rehabilitation training based on two phases: n=20 sessions of FES-cycling followed by n= 20 sessions of robot-assisted gait training based on an overground robotic exoskeleton. The following clinical outcome measures were used: Modified Ashworth Scale (MAS), Numerical Rating Scale (NRS) on spasticity, Penn Spasm Frequency Scale (PSFS), Spinal Cord Independence Measure Scale (SCIM), NRS on pain and International Spinal Cord Injury Pain Data Set (ISCI). Clinical outcome measures were assessed before (T0) after (T1) the FES-cycling training and after (T2) the powered overground gait training. The ability to walk when using exoskeleton was assessed by means of 10 Meter Walk Test (10MWT), 6 Minute Walk Test (6MWT), Timed Up and Go test (TUG), standing time, walking time and number of steps. Statistically significant changes were found on the MAS score, NRS-spasticity, 6MWT, TUG, standing time and number of steps. The preliminary results of this study show that an integrated gait rehabilitation training based on FES-cycling and overground robotic exoskeleton in complete SCI patients can provide a significant reduction of spasticity and improvements in terms of patient-robot interaction.

Exercise training is one strategy for improving cardiorespiratory fitness (CRF) in multiple sclerosis (MS); however, few modalities are accessible for those with severe mobility impairment. Functional electrical stimulation (FES) cycling is an adapted exercise modality with the potential for improving CRF in people with severe MS. The objective of this study was to characterize the cardiorespiratory response of acute voluntary cycling with FES in people with MS with severe mobility impairment, and to compare this response to passive leg cycling. Eleven participants with MS that required assistance for ambulation completed a single bout of voluntary cycling with FES or passive leg cycling. Oxygen consumption, heart rate (HR), work rate (WR), and ratings of perceived exertion (RPE) were recorded throughout the session. For the FES group, mean exercising oxygen consumption was 8.7 ± 1.8 mL/(kg·min)-1, or 63.5% of peak oxygen consumption. Mean HR was 102 ± 9.7 bpm, approximately 76.4% of peak HR. Mean WR was 27.0 ± 9.2 W, or 57.3% of peak WR, and median RPE was 13.5 (interquartile range = 5.5). Active cycling with FES was significantly (p < 0.05) more intense than passive leg cycling based on oxygen consumption, HR, WR, and RPE during exercise. In conclusion, voluntary cycling with FES elicited an acute response that corresponded with moderate-to vigorous-intensity activity, suggesting that active cycling with FES can elicit a sufficient stimulus for improving CRF.

Objective: To investigate the possible beneficial effects of muscle strength and standing balance in subjects with stroke using the FES-cycling ergometer system. Methods: Sixteen hemiplegic stroke patients were randomly assigned to perform leg cycling exercise (LCE), one with functional electrical stimulation (FES) evoking muscle contractions during a single bout cycling training and a control group received the same study protocol without FES. All subjects, blinded for group assignment, were measured at baseline and at post-test in the laboratory. Muscle strength was quantitatively measured by hand-held dynamometer (HHD), and furthermore the standing balance was evaluated by the limits of stability (LOS). Results: There was no significant change in the muscle strength after cycling in both groups. In addition, significant improvement of the paretic-side stability was detected in endpoint excursion (P= .031), maximum excursion (P= .000), and directional control (P= .013). While training-induced temporal changes of all outcome measures were no significant difference between the two groups. Conclusions: This experiment showed that a short cycling training program is a useful therapeutic intervention to improve the standing balance ability in patients with stroke. But the use of FES had no additional benefit in this experimental study. In the future studies, it will be of interest to use larger groups of subjects to investigate the long-term effects of this intervention on motor recovery and functional walking.

The functional electrical stimulation (FES) bicycle race was an event at the Cybathlon, held in Zurich October 2016. BerkelBike BV (The Netherlands) in collaboration with Imperial College London entered a spinal cord injury pilot who had tetraplegia to compete in this event. The BerkelBike Pro is a commercially available FES capable recumbent which is normally driven by the arm- and leg power. The arm cranking part was disabled. Now the tricycle must be driven using the pilots own lower limb muscles through stimulation in accordance with race rules. The bike used during the race was also adapted with a fixed gear for improved efficiency. The pilot who represented this team come second place overall in the event and attained the fastest race time of all pilots who utilised surface electrode FES. Steps can be taken to increase the race efficiency of the BerkelBikes and its FES capabilities even further.