Hybrid Functional Electrical Stimulation Research Articles

Exercise Responses During Outdoor Versus Virtual Reality Indoor Arm+FES-Leg Cycling in Individuals with Spinal Cord Injury.

Background: Virtual reality (VR)-enhanced indoor hybrid cycling in people with spinal cord injury (SCI) can be comparable to outdoor hybrid cycling. Method: Eight individuals with chronic thoracic-lesion SCI performed voluntary arm and electrically assisted leg cycling on a hybrid recumbent tricycle. Exercises were conducted outdoors and indoors incorporating VR technology in which the outdoor environment was simulated on a large flat screen monitor. Electrical stimulation was applied bilaterally to the leg muscle groups. Oxygen uptake (VO2), heart rate, energy expenditures, and Ratings of Perceived Exertion were measured over a 30-minute outdoor test course that was also VR-simulated indoors. Immediately after each exercise, participants completed questionnaires to document their perceptual-psychological responses. Results: Mean 30-minute VO2 was higher for indoor VR exercise (average VO2-indoor VR-exercise: 1316 ± mL/min vs. outdoor cycling: 1255 ± 53 mL/min; highest VO2-indoor VR-exercise: 1615 ± 67 mL/min vs. outdoor cycling: 1725 ± 67 mL/min). Arm and leg activity counts were significantly higher during indoor VR-assisted hybrid functional electrical stimulation (FES) cycling than outdoors; 42% greater for the arms and 23% higher for the legs (P < 0.05). Similar responses were reported for exercise effort and perceptual-psychological outcomes during both modes. Conclusion: This study proposes that combining FES and VR technology provides new opportunities for physical activity promotion or exercise rehabilitation in the SCI population, since these modes have similar "dose-potency" and self-perceived effort. Human Research Ethics Committee of the University of Sydney Ref. No. 01-2010/12385.

THE EFFECTS OF HYBRID FUNCTIONAL ELECTRICAL STIMULATION INTERVAL TRAINING ON AEROBIC FITNESS AND FATIGUE IN PEOPLE WITH ADVANCED MULTIPLE SCLEROSIS

INTRODUCTION &amp; AIMS Improving aerobic fitness in people with multiple sclerosis (MS) can reduce fatigue, and lower the risk of cardiovascular disease. Aerobic training can be challenging due to paresis, access to suitable equipment and fatigue. The aim was to investigate whether functional electrical stimulation (FES) cycling combined with arm crank interval exercise (hybrid FES interval training) is feasible for people with advanced MS, and its effects on aerobic fitness and fatigue. METHODS Hybrid FES interval training was performed 2 d/wk for 12 weeks. Each session consisted of 40 minutes of continuous FES cycling with arm crank intervals of 30 seconds work/30 seconds rest added concurrently for 20 minutes. The intensity target was a minimum of 60% of arm crank power and ‘hard’ measured by rate of perceived exertion (RPE) on a scale of 6-20. Feasibility was measured by attendance, compliance to intensity and time targets, adverse events, and drop outs. Aerobic fitness was assessed by an arm crank maximal test. Fatigue was measured via the Modified Fatigue Impact Scale (MFIS). RESULTS Seven participants (6 female; age 57.1±7.8y; Expanded Disability Status Scale 7.1±0.8) with advanced MS attended 80±10.4% of the scheduled sessions and there were no adverse events or drop outs. Average RPE at the end of each training session was 15±2, representing vigorous intensity exercise. Aerobic fitness did not change pre- to post-intervention [14.2±5.7 to 14.78±6.0 mL/kg/min (p=0.43)]. There was a trend towards a reduction in the MFIS score pre- to post-intervention [31.0±10.4 to 21.7±11.4 (p=0.10)]. CONCLUSION Hybrid FES interval training is feasible for people with advanced MS who need exercise equipment appropriate for their condition, and can represent vigorous intensity exercise. The positive findings support the need for future randomized control trials that can assess the aerobic fitness changes and associated health benefits of hybrid FES interval training.

Hybrid Functional Electrical Stimulation and Robotic Assistance for Wrist Motion Training After Stroke: Preliminary Results.

This work presents preliminary results of a clinical study with sub-acute stroke patients using a hybrid system for wrist rehabilitation. The patients trained their wrist flexion/extension motion through a target tracking task, where electrical stimulation and robotic torque assisted them proportionally to their tracking error. Five sub-acute stroke patients have completed the training for 3 sessions on separate days. The preliminary results show hybrid assistance improves tracking performance and motion smoothness in most participants. In each session, patients' tracking performances before and after training were evaluated in unassisted tracking trials, without assistance. Their unassisted performance was compared across sessions and the results suggest that moderately to severely impaired patients might benefit more from hybrid training with our system than mildly impaired patients. Subjective assessments from all sessions show that the patients found the use of the device very comfortable and the training enjoyable. More data is being collected and future work will aim at verifying these trends.

Six months of aerobic exercise training does not prevent a worsening of glucose tolerance in individuals with acute spinal cord injury

Individuals with spinal cord injuries (SCI) have a greater incidence of Type 2 Diabetes (T2D) than their non-injured peers. The increased incidence of T2D has been noted in individuals within the first few years after injury, and incidence increases with time since injury. Aerobic exercise training improves long-term glycemic control in non-injured individuals and results in improved glycemic control in individuals with chronic SCI (&gt;10 years). However, it is unknown whether individuals with acute injuries (&lt;3 years) display altered glucose control, and if aerobic training may prevent worsening of glucose control and T2D. Therefore, we assessed blood glucose regulation in individuals &lt;3 years post SCI injury. Glucose regulation was assessed through fasting blood glucose, insulin, hemoglobin A1C (HbA1C), homeostatic model assessment for insulin resistance (HOMA-IR), and an oral glucose tolerance test (OGTT). In addition, body composition was estimated via dual energy x-ray absorptiometry. These assessments were made prior to, and following 3- and 6-months (mo) of aerobic exercise training consisting of hybrid functional electrical stimulation rowing. Data were analyzed with 1-way RMANOVA. Eight individuals (1F, 7M, age 20-45 years) with SCI 9-27 mo post-injury and a neurological level of injury from spinal cord segments C3 to T3 were enrolled. Individuals exercised for 30min per session, at ~60% VO2peak, 2-3 times per week. Fasting glucose (Pre:85±9, 3m:88±8, 6m:86±2 mg/dL, p=0.55), insulin (Pre:6.0±3.8, 3m:5.7±2.5, 6m:3.9±2.5 uIU/mL, p=0.25), HbA1C (Pre:4.9±0.3, 3m:5.0±0.3, 6m:4.8±0.1%, p=0.73) and HOMA-IR (Pre:1.4±1.0, 3m:1.2±0.7, 6m:0.7±0.4, p=0.26) did not change after 6-mo of training. In contrast, the dynamic assessment of glucose tolerance (OGTT) showed dramatic worsening (AUC Pre:15.7±3.8, 3m:17.8±5.9, 6m:17.6±5.8 units, p=0.04) from pre-exercise to 3-mo. Moreover, following 6-mo of exercise training, 1 individual met the diagnostic criteria for impaired glucose tolerance and another 2 for diabetes. Exercise training did not change visceral adipose mass (Pre:1.4±0.9, 3m:1.4±1.2, 6m:1.3±1.2 kg, p=0.96) or total body lean mass (Pre:50.4±9.5, 3m:49.6±9.6, 6m:49.5±9.5kg, p=0.98). These results suggest that fasting measures alone are not sensitive enough in detecting impairments in glucose metabolism in the acute period following a SCI. Interestingly, in people with SCI, whole-body aerobic exercise does not prevent the occurrence of impaired glucose metabolism. The worsening of glucose tolerance occurs despite a conservation of lean mass and no increase in visceral adiposity. It will be of importance to determine the mechanisms underlying the worsening of glycemic control and develop therapies to prevent metabolic disease in SCI. R01 HL117037, F32 HL156675 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Software Interface of a Hybrid FES and Mechatronic Exoskeleton System for Hand Rehabilitation in Stroke People

Abstract This paper introduces novel contributions to the field of hand rehabilitation systems designed for stroke patients. The primary objective is to enhance voluntary movements in the paralyzed upper limbs, with a particular focus on hand functionality. The system, known as MANUTEX, comprises two main components: functional electrical stimulation (FES) implemented through a textile glove with embedded electrodes, connected to a programmable neurostimulator, and a mechatronic exoskeleton resembling a glove, powered by individual linear motors for each finger. These linear motors are controlled by a programmable microcontroller on a central board. MANUTEX delivers mirror therapy, a therapeutic approach requiring a sensory glove attached to the healthy hand. This sensory glove provides reference movements for the hybrid system located on the affected, impaired hand. An application installed on a computer serves as the control interface for the entire system. It reads movement data from the healthy hand and concurrently sends commands to both the FES and mechatronic exoskeleton glove, ensuring a balanced and synchronized therapeutic experience for the patient.

Hybrid Functional Electrical Stimulation Improves Anaerobic Threshold in First Three Years after Spinal Cord Injury.

The purpose of the present investigation was to assess the effects of whole-body exercise on the anaerobic threshold in individuals with spinal cord injury (SCI). Maximal oxygen uptake (VO2max) and oxygen uptake at anaerobic threshold (AT) were measured before and after six months of hybrid functional electrical stimulation row training in 47 participants with SCI aged 19-63, neurological levels of injury C4-L1, American Spinal Injury Association Impairment Scale grades A-D, and time since injury at enrollment from three months to 40 years. Changes in VO2max differed with time since injury, with greater increases earlier post-injury. The early chronic group (<3 years since injury; n = 31) increased VO2max from 1.65 ± 0.54 L/min at baseline to 1.83 ± 0.66 L/min at six months (p < 0.05), while the late chronic group (>3 years since injury; n = 16) did not change (1.42 ± 0.44 at baseline to 1.47 ± 0.41 L/min at six months, p = 0.36). Consistent with VO2max changes, AT increased in the early chronic group (1.03 ± 0.31 to 1.20 ± 0.40 L/min, p < 0.05) and did not change in the late chronic group (0.99 ± 0.31 to 0.99 ± 0.26 L/min, p = 0.92). Cumulative duration of exercise training was positively correlated to change in VO2max (r = 0.475, p < 0.05) but not to change in AT. Hybrid functional electrical stimulation row training is effective for increasing aerobic capacity and anaerobic threshold in individuals with SCI; however, these fitness benefits are only significant in individuals initiating the exercise intervention within three years of injury.

Pilot Study of Enhancing Cardiorespiratory Exercise Response in People With Advanced Multiple Sclerosis With Hybrid Functional Electrical Stimulation

ObjectiveTo investigate through a pilot study the acute cardiorespiratory responses during functional electrical stimulation (FES) cycling, arm crank ergometry (ACE), and a combination of ACE and FES cycling (hybrid FES cycling) in people with advanced multiple sclerosis (MS) to provide preliminary guidance for effective aerobic exercise prescription. DesignAcute repeated measures. SettingLaboratory setting. ParticipantsInclusion criteria was a diagnosis of MS, with Expanded Disability Status Scale (EDSS) 6.0-8.5. Included were 9 participants (N=9; 7 female, age 54.7±8.8y, EDSS 7.2±0.7). InterventionsParticipants were assessed on 3 different exercise modalities (FES cycling, ACE, hybrid FES cycling) at 40%, 60%, 80%, and 100% of mode-specific peak workload. Main Outcome MeasuresOxygen consumption and heart rate were measured at each workload. ResultsHybrid FES cycling evoked a significantly higher oxygen consumption relative to body weight (V̇o2relative) (mL/kg/min) and heart rate (beats per minute [BPM]) at most workloads compared with ACE or FES cycling. At the 100% workload, heart rate for hybrid FES cycling was 125 BPM (range, 113-148 BPM) and was significantly higher than ACE at 99 BPM (range, 95-119 BPM) (P=.008) and FES cycling at 94 BPM (range, 79-100 BPM) (P=.008). Similarly, at the 100% workload, V̇o2relative for hybrid FES cycling was 11.8 mL/kg/min (range, 7.6-17.6 mL/kg/min) and was significantly higher than ACE at 8.9 mL/kg/min (range, 5.3-12.5 mL/kg/min) (P=.012) and FES cycling at 6.8 mL/kg/min (range, 4.1-9.2 mL/kg/min) (P=.012). ConclusionsThis pilot study showed that hybrid FES cycling can elicit a greater cardiorespiratory response than ACE or FES cycling in people with advanced MS. Thus, hybrid FES cycling might provide a potent enough stimulus to induce clinically relevant changes in cardiorespiratory fitness. Training studies are warranted to document the magnitude and sustainability of aerobic capacity adaptations to hybrid FES cycling and associated health outcomes in advanced MS.

High-intensity, whole-body exercise improves blood pressure control in individuals with spinal cord injury: A prospective randomized controlled trial.

Blood pressure regulation following spinal cord injury (SCI) is often compromised due to impaired vascular sympathetic control, leading to increased reliance on cardiovagal baroreflex sensitivity to maintain pressure. Whole-body exercise improves cardiovagal baroreflex sensitivity in uninjured individuals, though has not been explored in those with SCI. Our objective was to determine changes in cardiovagal baroreflex sensitivity following 6 months of high-intensity, whole-body exercise in individuals with SCI compared to lower-intensity, arms only exercise, or waitlist. This randomized controlled trial recruited individuals with SCI aged 18–40 years old. Sixty-one individuals were randomized, with 38 completing at least one cardiovagal baroreflex sensitivity assessment. Whole-body exercise was performed with hybrid functional electrical stimulation rowing prescribed as two to three times per week, for 30–60 minutes with a target heart rate of >75% of maximum. The arms only exercise group performed upper body rowing exercise with the same prescription as whole-body exercise. Waitlist controls were not enrolled in any explicit training regimen. After 6 months, those in arms only exercise or waitlist crossed over to whole-body exercise. Cardiovagal baroreflex sensitivity was assessed via the neck suction technique at baseline and at three-month intervals thereafter. Intention to treat analysis with a structured equation model demonstrated no significant effect of waitlist control or arms only exercise on cardiovagal baroreflex sensitivity. Whole-body exercise significantly improved cardiovagal baroreflex sensitivity at 6 months for those initially randomized (p = 0.03), as well as those who crossed over from arms only exercise or waitlist control (p = 0.03 for each). However, amount of exercise performed and aerobic gains (VO2max) each poorly correlated with increases in cardiovagal baroreflex sensitivity (R2<0.15). In post-hoc analyses, individuals with paraplegia made significantly greater gains in baroreflex sensitivity compared to those with tetraplegia (p = 0.02), though gains within this group were again poorly correlated to gains in aerobic capacity. Clinicaltrials.gov number NCT02139436.

Cardiometabolic Effects of High-Intensity Hybrid Functional Electrical Stimulation Exercise after Spinal Cord Injury.

The prevalence of cardiometabolic disease following spinal cord injury is known to be high. However, it is unknown whether engaging in high-intensity exercise, which is advocated by recent guidelines, is beneficial or feasible for these individuals. To assess the effects of high-intensity, whole-body exercise on the prevalence of cardiometabolic disease in individuals with spinal cord injury. Combination of a randomized controlled trial and an open label intervention study of functional electrical stimulation legs plus arms rowing. Outpatient academic rehabilitation hospital. Forty individuals with spinal cord injury, with American Spinal Injury Association (ASIA) impairments scales A-D and neurological levels of injury C1-T12. Six months of high-intensity, hybrid-functional electrical stimulation rowing. Change in VO2max , serum lipids, and insulin resistance, prevalence of cardiometabolic disease. Individuals averaged 42.1± 22.0minutes of hybrid-functional electrical stimulation rowing a week over an average of 1.69 sessions per week over the 6months of intervention. This amounted to an average of 170.9± 100 km rowed, at a mean heart rate of 82.7% of individualized maximum. Only one of 40 individuals met current exercise guidelines for the full 6months. VO2max increased significantly (P< .001), yet prevalence of cardiometabolic disease did not change significantly (decrease from 22.5% to 20%, P= .70). Hemoglobin A1c did decrease significantly over this time (P= .01), although serum lipids and fasting glucose/insulin levels were unchanged. In exploratory subanalyses assessing individuals injured ≤12 months, those with more chronic injuries decreased their triglyceride-to-high-density lipoprotein (HDL) ratio (P= .04), a marker of cardiac mortality. Stratifying by neurological level of injury, individuals with paraplegia had worsened low-density lipoprotein (LDL) level (P= .02) and total cholesterol-to-HDL ratio (P= .04) over the 6-month intervention. Sustained high-intensity exercise with hybrid functional electrical stimulation rowing does not decrease the prevalence of cardiometabolic disease after spinal cord injury.

Towards real-time muscle fatigue and recovery markers using a wearable continuous wave Doppler ultrasound system

Functional electrical stimulation (FES) is commonly used in physical rehabilitation, bypassing the central nervous system to activate motor neurons directly. However, the unnatural muscle recruitment pattern induced by FES causes rapid muscle fatigue, greatly reducing the muscle's ability to generate force. Currently there exists no reliable, real time indicator for FES-induced muscle fatigue. We believe that signs of muscle fatigue can be inferred from medical ultrasound. Previously we investigated tissue Doppler imaging (TDI) to study muscle physiology associated with muscle potentiation and fatigue. Here, we expand on that research using continuous wave (CW) Doppler ultrasound to create a wearable, low power muscle fatigue monitor. We are investigating this system to work with a hybrid FES exoskeleton designed to use the patient's own muscles with FES with the added stability of an exoskeleton. CW ultrasound indicated that the duration of muscle recruitment decreased from 129.0 ms to 51.7 ms for the same FES as the muscle fatigued. Further, we showed that muscle twitch duration and velocity correlate with twitch force, a marker of fatigue recovery, using TDI and CW. These fatigue and recovery measures can be used to inform the exoskeleton controller to coordinate FES and electric motors for producing gait.

Gains in aerobic capacity with whole-body functional electrical stimulation row training and generalization to arms-only exercise after spinal cord injury.

Study Design:Longitudinal study in adults (n=27; 19–40 years old) with tetraplegic or paraplegic spinal cord injury (SCI).Objectives:Determine physiological adaptations and generalizable fitness effects of six months of whole-body exercise training using volitional arm and functional electrical stimulation (FES) leg rowing.Setting:Outpatient hospital-based exercise facility and laboratoryMethods:Participants enrolled in hybrid FES row training (FESRT) and performed peak exercise tests with arms-only (AO; baseline and 6-Mo) and FES rowing (baseline, 3-Mo, 6-Mo).Results:Participants demonstrated increased aerobic capacity (VO2peak) after FESRT (p<0.001, np2=0.56) that tended to be higher when assessed with FES than AO rowing tests (0.15 ± 0.20 vs. 0.04 ± 0.22 L/min; p=0.10). Changes in FES and AO VO2peak were significantly correlated (r=0.55; p<0.01), and 11 individuals demonstrated improvements (>6%) on both test formats. Younger age was the only difference between those who showed generalization of training effects and those who did not (mean age 26.6 ± 5.6 vs. 32.0 ± 5.7 years; p<0.05) but changes in FES VO2peak correlated to time since injury in individuals <2 years post-SCI (r=−0.51, p<0.01, n=24). Lastly, VO2peak improvements were greater during the first three months vs. months 4–6 (+7.0% vs. +3.9%; p<0.01) which suggests early training adaptations during FESRT.Conclusions:Gains in aerobic capacity after whole-body FESRT are better reflected during FES row testing format. They relate to high-intensity exercise and appear early during training, but they may not generalize to equivalent increases in AO exercise in all individuals with SCI.

Acute Ventilatory Support During Whole-Body Hybrid Rowing in Patients With High-Level Spinal Cord Injury: A Randomized Controlled Crossover Trial

High-level spinal cord injury (SCI) results in profound spinal and supraspinal deficits, leading to substantial ventilatory limitations during whole-body hybrid functional electrical stimulation (FES)-rowing, a form of exercise that markedly increases the active muscle mass via electrically induced leg contractions. This study tested the effect of noninvasive ventilation (NIV) on ventilatory and aerobic capacities in SCI. This blinded, randomized crossover study enrolled 19 patients with SCI (level of injury ranging from C4 to T8). All patients were familiar with FES-rowing and had plateaued in their training-related increases in aerobic capacity. Patients performed two FES-rowing peak exercise tests with NIV or without NIV (sham). NIV increased exercise tidal volume (peak, 1.50 ± 0.31L vs1.36 ± 0.34 L; P< .05) and reduced breathing frequency (peak, 35 ± 7 beats/min vs38 ± 6 beats/min; P< .05) compared with the sham test, leading to no change in alveolar ventilation but a trend toward increased oxygen uptake efficiency (P= .06). In those who reached peak oxygen consumption (Vo2peak) criteria (n= 13), NIV failed to significantly increase Vo2peak (1.73 ± 0.66 L/min vs1.78 ± 0.59 L/min); however, the range of responses revealed a correlation between changes in peak alveolar ventilation and Vo2peak (r= 0.89; P< .05). Furthermore, those with higher level injuries and shorter time since injury exhibited the greatest increases in Vo2peak. Acute NIV can successfully improve ventilatory efficiency during FES exercise in SCI but may not improve Vo2peak in all patients. Those who benefit most seem to be patients with cervical SCI within a shorter time since injury. ClinicalTrials.gov; Nos.: NCT02865343 and NCT03267212; URL:www.clinicaltrials.gov.

Relationship of Spinal Cord Injury Level and Duration to Peak Aerobic Capacity With Arms-Only and Hybrid Functional Electrical Stimulation Rowing.

The aim of the study was to assess the relationship of spinal cord injury level and duration to peak aerobic capacities during arms-only rowing compared with hybrid Functional Electrical Stimulation (FES)-rowing. Comparison of peak aerobic capacity (VO2), peak ventilation, peak respiratory exchange ratio, and peak heart rate were measured during arms-only rowing and FES-rowing obtained from graded exercise tests. Peak aerobic values were strongly related to injury level and injury duration for both arms-only rowing (r = 0.67, P < 0.05) and FES-rowing (r = 0.61, P < 0.05). Peak aerobic capacities were greater across all injury levels and durations with FES-rowing compared with arms-only rowing. Differences in VO2 were inversely related to injury level (r = 0.55, P < 0.05) with greater increases in VO2 in higher level injuries. Injury durations of less than 2 yrs had greater percent increases in VO2 with FES-rowing. FES-rowing acutely post injury may have the greatest effect to maintain function and improve VO2. This impact seems to be greatest in those with higher level injuries.

Hybrid FES–robotic gait rehabilitation technologies: a review on mechanical design, actuation, and control strategies

Gait disorders in neurologically disabled people can be treated by various techniques available today which include passive orthoses, functional electrical stimulation (FES) and robot assisted gait training devices (RAGT). However, each system has its own drawback. For example, gait rehabilitation with orthosis is physically taxing for the patient with no significant functional improvement. FES uses muscle powers as physiological actuators to promote balance and improve gait but leads to fatigue, along with poor control of joint trajectories. RAGT devices including powered exoskeletons, gait rehabilitation systems employing programmable footplates and mobile training platforms, have shown significant advantages but the devices are not yet mature due to numerous drawbacks associated with physical and cognitive interaction, energy-management and portability issues. The combination of FES technology and RAGT devices, often named hybrid FES–robot technologies, has arisen as a promising approach to aid in gait restoration. This work reports a comprehensive review on the hybrid FES–robot technologies over the last decades, focusing on different mechanical structures, actuator designs, sensing technologies, and control approaches. The hybrid robotic structures are classified into two categories: (i) orthotic-based hybrid systems, where (a) FES is used to stimulate the muscles and produce joint torque while the robotic system acts as energy dissipating device, and (b) FES and robotic systems are both torque-generating devices; and (ii) non-orthotic based hybrid systems. The review compiles a variety of sources and illustrates the technology’s most important challenges in the fields of hybrid rehabilitation robotics which may contribute towards further development of hybrid robot systems.

Assessing kinematics and kinetics of functional electrical stimulation rowing

Hybrid functional electrical stimulation (FES) rowing has positive effects on cardiovascular fitness, producing significantly greater aerobic power than either upper body or FES exercise alone. However, there is minimal information on the kinematics, kinetics, and mechanical efficiency of FES-rowing in the spinal cord injured (SCI) population. This study examined the biomechanics of FES-rowing to determine how motions, forces, and aerobic demand change with increasing intensity. Six individuals with SCI and six able-bodied subjects performed a progressive aerobic capacity rowing test. Differences in kinematics (motion profiles), kinetics (forces produced by the feet and arms), external mechanical work, and mechanical efficiency (work produced/volume of oxygen consumed) were compared in able-bodied rowing vs. SCI FES-rowing at three comparable subpeak workloads. With increasing exercise intensity (measured as wattage), able-bodied rowing increased stroke rate by decreasing recovery time, while FES-rowing maintained a constant stroke rate, with no change in drive or recovery times. While able-bodied rowers increased leg and arm forces with increasing intensity, FES-rowers used only their arms to achieve a higher intensity with a constant and relatively low contribution of the legs. Oxygen consumption increased in both groups, but more so in able-bodied rowers, resulting in able-bodied rowers having twice the mechanical efficiency of FES-rowers. Our results suggest that despite its ability to allow for whole body exercise, the total force output achievable with FES-rowing results in only modest loading of the legs that affects overall rowing performance and that may limit forces applied to bone.

A Hybrid Functional Electrical Stimulation for Real-Time Estimation of Joint Torque and Closed-Loop Control of Muscle Activation.

As a neuroprosthetic technique, functional electrical stimulation (FES) can restore lost motor performance of impaired patients. Through delivering electrical pulses to target muscles, the joint movement can be eventually elicited. This work presents a real-time FES system which is able to deal with two neuroprosthetic missions: one is estimating FES-induced joint torque with evoked electromyograph (eEMG), and the other is artificially controlling muscle activation with such eEMG feedback. The clinical experiment results on spinal cord injured (SCI) patients and healthy subjects show promising performance of the proposed FES system.

Ventilation Limits Aerobic Capacity after Functional Electrical Stimulation Row Training in High Spinal Cord Injury.

In the able-bodied, exercise training results in increased ventilatory capacity to meet increased aerobic demands of trained skeletal muscle. However, after spinal cord injury (SCI), peak ventilation can be limited by pulmonary muscle denervation. In fact, peak ventilation may restrict aerobic capacity in direct relation to injury level. Hybrid functional electrical stimulation (FES) exercise training results in increased aerobic capacity and dissociation between aerobic capacity and injury level in those with injuries at T3 and below. However, injuries above T3 have the greatest pulmonary denervation, and ventilatory capacity may restrict the increase in aerobic capacity with hybrid FES training. We assessed relationships among injury level, peak ventilation, and peak aerobic capacity and calculated oxygen uptake efficiency slope during hybrid FES exercise in 12 individuals (1 female) with SCI at level T2 to C4 (injury duration = 0.33-33 yr, age = 20-60 yr), before and after 6 months of FES-row training (FES-RT). Training increased peak aerobic capacity by 12% (P = 0.02) with only a modest increase in peak ventilation (7 of 12 subjects, P = 0.09). Both before and after training, injury level was directly related to peak ventilation (R = 0.48 and 0.43) and peak aerobic capacity (R = 0.70 and 0.55). Before training, the relationship of peak aerobic capacity to peak ventilation was strong (R = 0.62), however, after training, this relationship became almost completely linearized (R = 0.84). In addition, oxygen uptake efficiency slope increased by 11% (P < 0.05) after FES-RT. Despite the ability to increase exercise capacity via hybrid FES exercise, the inability to increase peak ventilation beyond limits set by SCI level in those with high-level injuries (above T3) appears to restrict aerobic capacity.

Exercise Program for Spinal Cord Injury Based on Hybrid Functional Electrical Stimulation Row Training

Exercise Program for Spinal Cord Injury Based on Hybrid Functional Electrical Stimulation Row Training

Hybrid brain-computer interface and functional electrical stimulation for sensorimotor training in participants with tetraplegia: a proof-of-concept study.

Impaired hand function decreases quality of life in persons with tetraplegia. We tested functional electrical stimulation (FES) controlled by a hybrid brain-computer interface (BCI) for improving hand function in participants with tetraplegia. Two participants with subacute tetraplegia (participant 1: C5 Brown-Sequard syndrome, participant 2: complete C5 lesion) took part in this proof-of-concept study. The goal was to determine whether the BCI system could drive the FES device by accurately classifying participants' intent (open or close the hand). Participants 1 and 2 received 10 sessions and 4 sessions of BCI-FES, respectively. A novel time-switch BCI strategy based on motor imagery was used to activate the FES. In one session, we tested a hybrid BCI-FES based on 2 spontaneously generated brain rhythms: a sensory-motor rhythm during motor imagery to activate a stimulator and occipital alpha rhythms to deactivate the stimulator. Participants received BCI-FES therapy 2 to 3 times a week in addition to conventional therapy. Imagery ability and muscle strength were measured before and after treatment. Visual feedback was associated with a 4-fold increase of brain response during motor imagery in both participants. For participant 1, classification accuracy (open/closed) for motor imagery-based BCI was 83.5% (left hand) and 83.8% (right hand); participant 2 had a classification accuracy of 83.8% for the right hand. Participant 1 had moderate improvement in muscle strength, while there was no change for participant 2. We demonstrated feasibility of BCI-FES, using 2 naturally generated brain rhythms. Studies on a larger number of participants are needed to separate the effects of BCI training from effects of conventional therapy.Video Abstract available. (see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A84) for more insights from the authors.

Hybrid Functional Electrical Stimulation Exercise Training Alters the Relationship Between Spinal Cord Injury Level and Aerobic Capacity

To test the hypothesis that hybrid functional electrical stimulation (FES) row training would improve aerobic capacity but that it would remain strongly linked to level of spinal cord lesion because of limited maximal ventilation. Longitudinal before-after trial of 6 months of FES row training. Exercise for persons with disabilities program in a hospitaL. Volunteers (N=14; age range, 21-63y) with complete spinal cord injury (SCI) (T3-11) who are >2 years postinjury. Six months of FES row training preceded by a variable period of FES strength training. Peak aerobic capacity and peak exercise ventilation before and after 6 months of FES row training. FES row training significantly increased peak aerobic capacity and peak minute ventilation (both P<.05). Prior to FES row training, there was a close relation between level of SCI and peak aerobic capacity (adjusted R(2)=.40, P=.009) that was markedly reduced after FES row training (adjusted R(2)=.15, P=.10). In contrast, the relation between level of injury and peak minute ventilation was comparable before and after FES row training (adjusted R(2)=.38 vs .32, both P<.05). The increased aerobic capacity reflects more than increased ventilation; FES row training effectively circumvents the effect of SCI on peak aerobic capacity by engaging more muscle mass for training, independent of the level of injury.