FES Rehabilitative Systems for Re‐Education of Walking in Incomplete Spinal Cord Injured Persons

Objective. The aim of the paper is to present various relatively simple functional electrical stimulation (FES) systems that affect neural circuits and reflex behavior by providing necessary peripheral input to the lower extremities of incomplete spinal cord injured (SCI) persons. Methods. The proposed FES re‐education walking systems make use of feedback information that is transmitted from the paralyzed limb to the nonparalyzed part of the patient's body. A single gait variable can be analogously transmitted to the walking subject in a form of sensory stimulation. The information about several gait variables can be first integrated and afterwards delivered to the walking subject as a single command. Conclusions. Significant improvements in the duration of the double support phase, metabolic energy expenditure, and physiologic cost index were observed when using FES‐assisted training of walking in incomplete SCI persons.     

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.     

Locomotor training using body weight support on a treadmill improves mobility in persons with multiple sclerosis: a pilot study

RATIONALE: The purpose of this protocol was to investigate the potential benefits and tolerability of locomotor training using body weight support on a treadmill (LTBWST) in persons with multiple sclerosis (MS). METHODS: Four persons with primarily spinal cord MS and severely impaired ambulation (Expanded Disability Status Scale score 7.0-7.5) were enrolled in LTBWST. Subjects completed an average of 40 training sessions over several months. RESULTS: Subjects showed improvement in muscle strength, spasticity, endurance, balance, walking speed, and quality of life at the end of the training sessions, and could tolerate training without fatigue or other adverse effects. CONCLUSIONS: LTBWST is well tolerated by persons with MS and may produce improvements in parameters related to functional mobility.     

Stochastically-modulated stimulation to slow down muscle fatigue at stimulated sites in paraplegics using functional electrical stimulation for leg extension

This short communication is a preliminary report on a study concerning slowing down the rate of muscle fatigue when FES (Functional Electrical Stimulation) is applied for standing and walking by complete (traumatic) thoracic-level paraplegics. It is shown that randomly modulating the inter-pulse interval between FES pulses (which serve to trigger action potentials in the peripheral nerves concerned) results in a significantly lower rate of muscle fatigue, as tested in a series of leg extensions, when FES was applied at the quadriceps. Specifically, we report that the best results (longest durations of leg extension prior to onset of muscle-fatigue) were achieved with a +/- 5 msec uniformly-distributed (pseudo-) white-noise modulation at a 42 msec inter-pulse interval (24 pulses per sec). These resulted in an average increase in duration of leg extension of approximately 37% in this pilot study, as compared with unmodulated (fixed-rate) trains of FES pulses. This significant increase, even in a very preliminary study appears to merit careful further examination, since it may allow a possibly significant increase in standing duration and in walking range of paraplegics using FES for ambulation.     

A pilot study of proximal strength training in Charcot‐Marie‐Tooth disease

Gait analysis of people with Charcot‐Marie‐Tooth (CMT) disease revealed proximal adaptive gait strategies to compensate for foot drop. We previously demonstrated that hip flexor muscle fatigue can limit walking endurance. This pilot study used a single‐blinded cross over design to investigate the effect of a 16‐week home‐based programme of resistance training on hip flexor muscle strength. Measures of walking endurance, gait speed, exertion, fatigue, and general activity were also recorded. The exercise protocol was based on American College of Sports Medicine recommendations. A mixed effects model was used for analysis. Twenty‐six people finished the study, with average reported exercise participation of 93%. No negative effects of exercise were observed. Significant increase in hip flexor muscle strength was observed on the left, but not the right. No changes were observed in walking speed and endurance measures. This pilot study of home‐based resistance training showed a modest improvement in hip strength but only on one side. The lack of a more significant improvement and no improvement in walking measures suggests that this training protocol may not be optimal for people with CMT and that patients may need to stratified differently for training studies in CMT.     

Walking performance, medical outcomes and patient training in FES of innervated muscles for ambulation by thoracic-level complete paraplegics

OBJECTIVE: To discuss functional electric stimulation (FES) gait training of upper motoneuron spinal cord injured complete paraplegics considering ambulation performance, physiologic and metabolic responses as well as psychologic outcome, while providing myologic insight into ambulation via FES when training starts many years post-injury. METHODS: Transcutaneous FES using the Parastep stimulation system, gait training methods with and without major emphasis on muscle reinforcement, cardiovascular and respiratory conditioning. Examination of myofiber tissues and correlation of normal muscles histology versus innervated muscles of upper motor neuron and of denervated muscles of lower motor neuron paraplegics. RESULTS: Published works in literature reviewed in this paper report average walking distance of 440 m/walk when major muscle reinforcement and preconditioning cardiovascular and respiratory systems precedes gait training, versus average 115 m/walk when undergoing direct gait training. Medical, metabolic and psychologic outcomes, as reported in several works, point to benefits of FES walking, including 60% increase in blood flow to lower extremities. Myofiber tissues of patients with upper motor neuron paralysis compare well with those of normal tissue even many years post-injury, while adipose tissue substitute muscle fibers in patients with lower motor neuron lesions. DISCUSSION: Transcutaneous FES allows considerably longer walking distances and speed at the end of training when training involves an extensive pre-conditioning program than with direct gait training. Medical and psychologic benefits are observed, especially concerning blood flow to the lower extremities. Myofiber examinations provide myologic understanding of effectiveness of FES many years post-injury.     

Stochastically-modulated stimulation to slow down muscle fatigue at stimulated sites in paraplegics using functional electrical stimulation for leg extension

Abstract

This short communication is a preliminary report on a study concerning slowing down the rate of muscle fatigue when FES (Functional Electrical Stimulation) is applied for standing and walking by complete (traumatic) thoracic-level paraplegics. It is shown that randomly modulating the inter-pulse interval between FES pulses (which serve to trigger action potentials in the peripheral nerves concerned) re~lJlts in a significantly lower rate ofmuscle fatigue, as tested in a series ofleg extensions, when FES was applied at the quadriceps. Specifically, we report that the best results (longest durations of leg extension prior to onset of muscle-fatigue) were achieved with a ± 5 msec uniformly-distributed (pseudo-) white-noise modulation at a 42 msec inter-pulse interval (24 pulses per sec). These resulted in an average increase in duration of leg extension ofapproximately 37% in this pilot study, as compared with unmodulated (fixed-rate) trains ofFES pulses. This significant increase, even in a very preliminary study appears to merit careful further examination, since it may allow a possibly significant increase in standing duration and in walking range of paraplegics using FES for ambulation. [Neural Res 2000; 22: 703-704]     

Improved gait parameters after robotic‐assisted locomotor treadmill therapy in a 6‐year‐old child with cerebral palsy

Task‐specific body‐weight‐supported treadmill therapy improves walking performance in children with central gait impairment. Modulation of spinal networks and improvement of muscle energy consumption are thought to contribute to this effect. Robotic‐assisted treadmill therapy enabled by a driven gait orthosis (DGO) has been established for adults and shown to provide significant improvements in individuals with spinal cord injury and stroke. Recently a pediatric DGO has been developed. Here, we report the results of a 3‐week trial of robotic‐assisted treadmill therapy of a 6‐year‐old boy with bilateral spastic cerebral palsy. The boy tolerated the trial very well and showed improved function, speed, and endurance of walking. Introducing methods of robotic medicine to pediatrics may help children with central gait impairment to regain motor function. © 2007 Movement Disorder Society     

An overview of the state of the art of noninvasive FES for independent ambulation by thoracic level paraplegics

This paper is an overview of the status of transcutaneous noninvasive (unbraced) functional electrical stimulation (FES) for independent standing and for independent ambulation by traumatic spinal-cord injured (SCI) paraplegics with complete spinal cord lesions at the thoracic level. The paper discusses aspects of patient selection, patient training, system performance, ambulation range, medical benefits and psychological benefits. It also considers problems relating to system adoption and long term system use. Furthermore, the paper discusses the various aspects of transcutaneous noninvasive FES as compared with implanted FES systems for ambulation by thoracic level SCI patients.     

Methods for a randomized trial of weight-supported treadmill training versus conventional training for walking during inpatient rehabilitation after incomplete traumatic spinal cord injury

The authors describe the rationale and methodology for the first prospective, multicenter, randomized clinical trial (RCT) of a task-oriented walking intervention for subjects during early rehabilitation for an acute traumatic spinal cord injury (SCI). The experimental strategy, body weight-supported treadmill training (BWSTT), allows physical therapists to systematically train patients to walk on a treadmill at increasing speeds typical of community ambulation with increasing weight hearing. The therapists provide verbal and tactile cues to facilitate the kinematic, kinetic, and temporal features of walking. Subjects were randomly assigned to a conventional therapy program for mobility versus the same intensity and duration of a combination of BWSTT and over-ground locomotor retraining. Subjects had an incomplete SCI (American Spinal Injury Association grades B, C, and D) from C-4 to T-10 (upper motoneuron group) or from T-11 to L-3 (lower motoneuron group). Within 8 weeks of a SCI, 146 subjects were entered for 12 weeks of intervention. The 2 single-blinded primary outcome measures are the level of independence for ambulation and, for those who are able to walk, the maximal speed for walking 50 feet, tested 6 and 12 months after randomization. The trial's methodology offers a model for the feasibility of translating neuroscientific experiments into a RCT to develop evidence-based rehabilitation practices.     

Treadmill training-induced adaptations in muscle phenotype in persons with incomplete spinal cord injury

Body weight-supported treadmill (BWST) training has been shown to improve ambulatory capacity in persons with a spinal cord injury (SCI); however, the effect that BWST training has on skeletal muscle phenotype is unknown. We aimed to determine whether 6 months (three sessions/week) of BWST training in neurologically stable persons with a traumatic spinal cord injury (ASIA C) alters skeletal muscle phenotype, ambulatory capacity, and blood lipid profile. Externally supported body weight decreased, and walking velocity and duration of the training sessions increased (all P < 0.05) as a result of training. Muscle biopsies revealed increases in the mean muscle-fiber area of type I and IIa fibers. Training induced a reduction in type IIax/IIx fibers, as well as a decrease in IIX myosin heavy chain, and an increase in type IIa fibers. Maximal citrate synthase and 3-hydroxy-acyl-CoA dehydrogenase activity also increased following training. BWST training brought about reductions in plasma total (-11%) and low-density lipoprotein (-13%) cholesterol. We conclude that, in patients with a spinal cord injury, BWST training is able to induce an increase in muscle fiber size and bring about increases in muscle oxidative capacity. In addition, BWST training can bring about improvements in ambulatory capacity and antiatherogenic changes in blood lipid profile.     

Surface‐distributed low‐frequency asynchronous stimulation delays fatigue of stimulated muscles

Introduction: One important reason why functional electrical stimulation (FES) has not gained widespread clinical use is the limitation imposed by rapid muscle fatigue due to non‐physiological activation of the stimulated muscles. We aimed to show that asynchronous low‐pulse‐rate (LPR) electrical stimulation applied by multipad surface electrodes greatly postpones the occurrence of muscle fatigue compared with conventional stimulation (high pulse rate, HPR). Methods: We compared the produced force vs. time of the forearm muscles responsible for finger flexion in 2 stimulation protocols, LPR (f_L = 10 Hz ) and HPR (f_H = 40 Hz ). Results: Surface‐distributed low‐frequency asynchronous stimulation (sDLFAS) doubles the time interval before the onset of fatigue (104 ± 80%) compared with conventional synchronous stimulation. Conclusions: Combining the performance of multipad electrodes (increased selectivity and facilitated positioning) with sDLFAS (decreased fatigue) can improve many FES applications in both the lower and upper extremities. Muscle Nerve 48 : 930–937, 2013     

An overview of the state of the art of noninvasive FES for independent ambulation by thoracic level paraplegics

Abstract

This paper is an overview of the status of transcutaneous noninvasive (unbraced) functional electrical stimulation (FES) for independent standing and for independent ambulation by traumatic spinal-cord injured (SCI) paraplegics with complete spinal cord lesions at the thoracic level. The paper discusses aspects of patient selection, patient training, system performance, ambulation range, medical benefits and psychological benefits. It also considers problems relating to system adoption and long term system use. Furthermore, the paper discusses the various aspects of transcutaneous noninvasive FES as compared with implanted FES systems for ambulation by thoracic level SCI patients. [Neurol Res 2002; 24: 431-442]     

Distributed low‐frequency functional electrical stimulation delays muscle fatigue compared to conventional stimulation

We present a low‐frequency stimulation method via multi‐pad electrodes for delaying muscle fatigue. We compared two protocols for muscle activation of the quadriceps in paraplegics. One protocol involved a large cathode at 30 HZ (HPR, high pulse‐rate), and the other involved four smaller cathodes at 16 HZ (LPR, low pulse‐rate). The treatment included 30‐min daily sessions for 20 days. One leg was treated with the HPR protocol and the other with the LPR protocol. Knee‐joint torque was measured before and after therapy to assess the time interval before the knee‐joint torque decreased to 70% of the initial value. The HPR therapy provided greater increases in muscle endurance and force in prolonged training. Yet the LPR stimulation produced less muscle fatigue compared to the HPR stimulation. The results suggest that HPR is the favored protocol for training, and LPR is better suited for prolonged stimulation. Muscle Nerve, 2010     

Resistance training improves strength and functional capacity in persons with multiple sclerosis

The purpose of this study was to evaluate the effect of an eight-week progressive resistance training programme on lower extremity strength, ambulatory function, fatigue and self-reported disability in multiple sclerosis (MS) patients (mean disability score 3.7 +/- 0.8). Eight MS subjects volunteered for twice weekly training sessions. During the first two weeks, subjects completed one set of 8-10 reps at 50% of maximal voluntary contraction (MVC) of knee flexion, knee extension and plantarflexion exercises. In subsequent sessions, the subjects completed one set of 10-15 repetitions at 70% of MVC. The resistance was increased by 2-5% when subjects completed 15 repetitions in consecutive sessions. Isometric strength of the quadriceps, hamstring, plantarflexor and dorsiflexor muscle groups was assessed before and after the training programme using an isokinetic dynamometer. Magnetic resonance images of the thigh were acquired before and after the exercise programme as were walking speed (25-ft), number of steps in 3 min, and self-reported fatigue and disability. Knee extension (7.4%), plantarflexion (52%) and stepping performance (8.7%) increased significantly (P < 0.05). Self-reported fatigue decreased (P < 0.05) and disability tended to decrease (P = 0.07) following the training programme. MS patients are capable of making positive adaptations to resistance training that are associated with improved ambulation and decreased fatigue.     

New functional electrical stimulation approaches to standing and walking

Spinal cord injury (SCI) is a devastating neurological trauma that is prevalent predominantly in young individuals. Several interventions in the areas of neuroregeneration, pharmacology and rehabilitation engineering/neuroscience are currently under investigation for restoring function after SCI. In this paper, we focus on the use of neuroprosthetic devices for restoring standing and ambulation as well as improving general health and wellness after SCI. Four neuroprosthetic approaches are discussed along with their demonstrated advantages and their future needs for improved clinical applicability. We first introduce surface functional electrical stimulation (FES) devices for restoring ambulation and highlight the importance of these devices for facilitating exercise activities and systemic physiological activation. Implanted muscle-based FES devices for restoring standing and walking that are currently undergoing clinical trials are then presented. The use of implanted peripheral nerve intraneural arrays of multi-site microelectrodes for providing fine and graded control of force during sit-to-stand maneuvers is subsequently demonstrated. Finally, intraspinal microstimulation (ISMS) of the lumbosacral spinal cord for restoring standing and walking is introduced and its results to date are presented. We conclude with a general discussion of the common needs of the neuroprosthetic devices presented in this paper and the improvements that may be incorporated in the future to advance their clinical utility and user satisfaction.     

Gait training strategies utilized in poststroke rehabilitation: are we really making a difference?

Stroke is the leading cause of disability in the United States. Restoration of walking continues to be a major goal of rehabilitation for persons with stroke. The concept of a minimal change in performance to be considered important or significant has recently been addressed in the field of stroke rehabilitation. We examine some of the changes in locomotor function in poststroke individuals. None of the neurofacilitation approaches have shown significant improvement in walking performance after stroke. Functional electrical stimulation (FES) can be performed by stimulating over the muscle, intra-muscularly, or over the peripheral nerve that innervates a muscle providing insufficient force for gait. To date, no form of artificial stimulation can match natural activation for precision or fatigue resistance. Body weight-supported treadmill training (BWSTT) is thought to contribute substantially to the reorganization of neural circuitry and has been shown to restore gait of nonambulatory individuals. Despite the promising recovery suggested by BWSTT, the time and physical demands on therapists have prevented it from wide clinical acceptance. Thus various robotic devices have been developed to provide such "mechanical" stepping assistance. The magnitude of changes induced with robotic devices does not appear to be any greater than that achieved with more traditional approaches or as compared to task-specific BWSTT.     

Endurance neuromuscular electrical stimulation training improves skeletal muscle oxidative capacity in individuals with motor‐complete spinal cord injury

Introduction: Spinal cord injury (SCI) results in skeletal muscle atrophy, increases in intramuscular fat, and reductions in skeletal muscle oxidative capacity. Endurance training elicited with neuromuscular electrical stimulation (NMES) may reverse these changes and lead to improvement in muscle metabolic health. Methods: Fourteen participants with complete SCI performed 16 weeks of home‐based endurance NMES training of knee extensor muscles. Skeletal muscle oxidative capacity, muscle composition, and blood metabolic and lipid profiles were assessed pre‐ and post‐training. Results: There was an increase in number of contractions performed throughout the duration of training. The average improvement in skeletal muscle oxidative capacity was 119%, ranging from –14% to 387% (P = 0.019). There were no changes in muscle composition or blood metabolic and lipid profiles. Conclusion: Endurance training improved skeletal muscle oxidative capacity, but endurance NMES of knee extensor muscles did not change blood metabolic and lipid profiles. Muscle Nerve 55: 669–675, 2017     

Clinical relevance of gait research applied to clinical trials in spinal cord injury

The restoration of walking function following SCI is extremely important to consumers and has stimulated a response of new treatments by scientists, the pharmaceutical industry and clinical entrepreneurs. Several of the proposed interventions: (1) the use of functional electrical stimulation (FES) and (2) locomotor training have been examined in clinical trials and recent reviews of the scientific literature. Each of these interventions is based on research of human locomotion. Therefore, the systematic study of walking function and gait in normal individuals and those with injury to the spinal cord has contributed to the identification of the impairments of walking, the development of new treatments and how they will be measured to determine effectiveness. In this context gait research applied to interventions to improve walking function is of high clinical relevance. This research helps identify walking impairments to be corrected and measures of walking function to be utilized as endpoints for clinical trials. The most common impairments following SCI diagnosed by observational gait analysis include inadequate hip extension during stance, persistent plantar flexion and hip/knee flexion during swing and foot placement at heel strike. FES has been employed as one strategy for correcting these impairments based on analysis that range from simple measures of speed, cadence and stride length to more sophisticated systems of three- dimensional video motion analysis and multichannel EMG tracings of integrated walking. A recent review of the entire FES literature identified 36 studies that merit comment and the full range of outcome measures for walking function were used from simple velocity to the video analysis of motion. In addition to measures of walking function developed for FES interventions, the first randomized multicenter clinical trial on locomotor training in subacute SCI was recently published with an extensive review of these measures. In this study outcome measures of motor strength (impairment), balance, Walking Index for SCI (WISCI), speed, 5min walk (walking capacities) and locomotor functional independence measure (L-FIM), a disability measure all showed improvement in walking function based on the strategy of the response of activity based plasticity to step training. Although the scientific basis for this intervention will be covered in other articles in this series, the evolution of clinical outcome measures of walking function continues to be important for the determination of effectiveness in clinical trials.     

Evoked EMG and Muscle Fatigue During Isokinetic FES-Cycling in Individuals With SCI

Purpose: This study investigated whether muscle fatigue during functional electrical stimulation (FES)‐induced cycling was associated with changes occurring in evoked electromyographic signals (eEMG, M‐waves) in individuals with spinal cord injury. We also explored the effects of recovery intervals between exercise sessions on the relationship between eEMG and muscle torque. Methods: Eight individuals with spinal cord injury performed three FES‐cycling sessions of 15‐min duration, with 5 min of recovery between them. The quadriceps muscles were electrically stimulated as the prime agonist to produce cycling. Pedal torques and surface eEMG signals were synchronously processed and recorded for offline analysis. Results: Large Torque decreases (20–44%) were observed in the first 5 min of cycling during the three exercise bouts, while changes of similar magnitude did not occur on any of the M‐wave time‐series (less than 19%). Between 5 and 15 min of cycling, muscle fatigue lowered the plateau baselines of Torque (ranging from 41% to 62%), M‐wave peak‐to‐peak amplitude (PtpA) and Area (ranging from 60% to 98%) time‐series, yet the magnitudes of these reductions were not consistent between them. Conclusion: We concluded that muscle fatigue during FES‐cycling was not associated with, nor could be predicted by, eEMG signals. Nonetheless, the consistency between M‐waves and Torque time‐curves in their direction of change clearly warrants further investigation.