Functional Electrical Stimulation
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Author Year; Country Score Research Design Total Sample Size |
Methods | Outcomes |
FES-assisted cycling | ||
Ralston et al. 2013; Australia |
Population: 14 individuals; average age 25y; motor complete lesions between C4 and T10; AIS A, B; 118 days post injury Treatment: Participants were randomized to an experimental phase followed by a control phase or vice versa, with a 1-week washout period in between. The experimental phase involved FES cycling four times a week for two weeks and the control phase involved standard rehabilitation for two weeks. Outcome Measures: Primary outcome-urine output (mL/hr); Secondary outcomes- lower limb circumference, and spasticity using the Ashworth Scale, and the Patient Reported Impact of Spasticity Measure (PRISM). Participants were also asked open-ended questions to explore their perceptions about treatment effectiveness. |
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Effect Sizes: Forest plot of standardized mean differences (SMD ± 95%C.I.) as calculated from pre- and post-intervention data![]() |
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Kuhn et al. 2014; Germany |
Population: 30 individuals; average age 44 ± 15.5y; motor complete and incomplete spinal cord injuries in the cervical, lumbar, and thoracic regions; AIS A = 10, B = 3, C = 15, D = 2; 0-122 months post injury Treatment: During the 4-week study period, all patients received eight 20min FES interventions at the beginning and end of each week. At every intervention, circumferential measurement and spasticity testing before and after FES cycling (pretest/post-test) were performed. Ultrasound, walking tests, and manual muscle test were only performed at the beginning of week 1 (T1) and at the end of week 4. Outcome Measures: Circumferential measurement, muscular ultrasound measurement, spasticity measured by MAS, Walking (6 Minute Walk, TUG). |
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Duffell et al. 2008; UK |
Population: 11 participants with complete SCI, level of injury T3-T9, mean (SD) 10.7(2.1) YPI; 10 untrained AB controls, mean (SD) age 30.6(3.2) yrs Treatment: FES cycling, up to 1hr/day, 5 days/week for 1 year Outcome Measures: Maximal quadriceps torque; quadriceps fatigue resistance; power output (PO). |
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Baldi et al. 1998; USA PEDro=5 RCTLevel 2 N=26 |
Population: 26 males and females; age 25-28 yrs; traumatic motor complete; cervical or thoracic lesion level; 15 wks post-injury Treatment: Random assignment to 3-6 months of 1) FES-assisted cycle ergometry (n=8), 30 min, 3X/week; 2) PES-assisted isometric exercise group (n=8) (same muscle groups as FES group) for 1 hr, 5X/week or 3) control group (n=9) with no stimulation. Outcome Measures: lower limb lean body mass. |
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Effect Sizes: Forest plot of standardized mean differences (SMD ± 95%C.I.) as calculated from pre- and post-intervention data![]() |
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Deley et al. 2015; USA Pre-Post Level 4 N=10 |
Population: 10 individuals- 8m/2f; average age 34 ± 4.0y; years post injury 9.8 ± 2.7y; level of lesion between C5 and T12; 9 AIS A & 1 AIS B Treatment: Each participant underwent 2 testing sessions separated by at least 24h. During each testing session, isometric muscle torque was measured under 2 sequential electrical stimulation train patterns. Individuals underwent either CFT or VFT patterns until target torque was no longer produced and then switched immediately to the other pattern. Outcome Measures: Isometric muscle torque, CFT (constant frequency train) pattern, VFT (variable frequency train) pattern. |
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Gibbons et al. 2014; United Kingdom |
Population: 8 participants- 4 males and 4 females; chronic complete and incomplete tetraplegia; injuries between C4 and C7, 5 AIS A, 1 AIS B, 2 AIS C; mean age= 30.5 ± 11.4y; years post injury= 8.4 ± 4.2y Treatment: Participants completed a progressive FES-assisted training program building to three continuous 30-min FES-R sessions per week at 60–80% of their predetermined peak power output. Thereafter, rowing performance was monitored for 12 months. Outcome Measures: Number and type of FES-training sessions required before achieving 30-min continuous FES-R, FES-R average power output (POav) pre and post 12 months training, participant feedback of perceived benefits. |
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Gorgey et al. 2015; USA Pre-Post Level 4 N= 7 |
Population: 7 males; motor complete SCI; RT + diet group: average age= 35 ± 10y, years post injury 15 ± 9y, level of lesion between C5 and C7; Diet control group: mean age= 29 ± 4y; years post injury= 4 ± 2y Treatment: Seven men with motor complete SCI were randomly assigned to a resistance training plus diet (RT + diet) group (n = 4) or a diet control group (n = 3). Participants in the RT + diet group were enrolled in a 12-week leg extension weight-lifting program via surface NMES of the knee extensor muscle group. The length of mid-thigh intermuscular fascia and the patellar tendon CSA were measured using MRI. Outcome Measures: Length of mid-thigh intermuscular fascia and the patellar tendon CSA |
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Fornusek et al. 2013; Australia |
Population: 8 participants with chronic SCI; mean (SD) age: 39 (14); C7-T11; 7 AIS A, 1 AIS C. Treatment: 6 weeks (3 days/wk) of training on an isokinetic FES cycle ergometer. For each participant, 1 leg was randomly allocated to cycling at 10 rpm (LOW) for 30 min/day and the other cycling at 50rpm (HIGH) for 30 min/day. Outcome Measures: lower limb circumference (distal and middle position of each thigh); electrically evoked quadriceps muscle torque during isometric contraction |
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Thrasher et al. 2013; USA |
Population: 11 participants with SCI (8M, 3F); 22-57 yrs; 8-95 months post-injury. Treatment: 40 sessions of FES-LCE at a rate of 3 sessions/wk for 13 weeks. Continuous exercise was performed at a pedal cadence of 45RPM against a constant resistance for up to 60 minutes. Outcome Measures: Mean power output; knee extension torque; Fatigue Index. |
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Reichenfelser et al. 2012; Austria |
Population: 23 participants with SCI (20M 3F); mean(SD) age=40(14); mean(SD) DOI: 9(7) months; 7 tetraplegic, 16 paraplegic. Treatment: All participants underwent a mean(SD) of 18(14) training sessions on an instrumented tricycle combined with functional electrical stimulation. Outcome Measures: Power output; Modified Ashworth Test. |
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Haapala et al. 2008; |
Population: 6 SCI participants, between 20-50yrs old, complete and incomplete injury at or below C4, with previous FES cycle ergometry experience. Treatment: FES-LCE, progressive cycling (resistance) protocol with increasing resistance, as well as prolonged, submaximal cycling for 30min. Outcome Measures: Power output for ankle (APO), knee (KPO), and hip (HPO), HR |
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Liu et al. 2007; Taiwan |
Population: 18 males and females; age 26-61 yrs; AIS B-D; C3-L1 lesion level; 1-9 yrs post-injury Treatment: FES cycling exercises three times a week for 8 weeks; 30 minutes/session Outcome Measures: Muscle peak torque of knee flexors and extensors |
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Crameri et al. 2002; Denmark Pre-post Level 4 N=6 |
Population: 5 males, 1 female; age 28-43 yrs; complete; T4-T12 lesion level; >8 yrs post-injury Treatment: FES leg cycle ergometry training, 3 – 30 min/week for 10 weeks. Outcome Measures: Incremental exercise leg test to muscle fatigue (total work output), histological assessment, myosin heavy chain (contractile protein) (MHC), citrate synthase (a mitochondrial enzyme) and hexokinase (enzyme needed to produce muscle glycogen). |
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Gerrits et al. 2000;UK Pre-post Level 4 N=7 |
Population: 7 males; age 28-61 yrs; AIS A and B; C5-T8 lesion level; 1-27 yrs post-injury Treatment: FES leg cycle ergometry training, 3 – 30 minutes sessions/week for 6 weeks. Outcome Measures: Thigh girth, work output, contractile speed and fatigue resistance characteristics, including half relaxation time (½ Rt) and degree of fusion of electrically stimulated isometric contractions. |
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Koskinen et al. 2000; Finland Pre-post Level 4 N=10 |
Population: 10 males and females; age 27-45 yrs; complete; tetraplegic and paraplegic Treatment: 18-month FES-assisted cycling ergometry (First training period: 30 min, 3X/week, 1 year; Second training period: 1X/week, 6 months). Outcome Measures: Muscle morphology and protein measurement (type IV collagen, total collagen, muscle proteins). |
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Scremin et al. 1999; USA Pre-post Level 4 N=13 |
Population: 13 males; age 24-46 yrs; AIS A; C5-L1 lesion level; 2-19 yrs post-injury. Treatment: A 3-phase, FES-assisted cycle ergometry exercise program leading to FES-induced cycling for 30 minutes. Average program was 2.3X/week for 52.8 weeks. Outcome Measures: CT-scan of legs to assess muscle cross-sectional area and proportion of muscle and adipose tissue collected (pre-test, midpoint and post-test). |
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Yasar et al. 2015; Turkey |
Population: 10 males and females with incomplete SCI that can ambulate more than 10m independently or with an assistive device Treatment: The participants underwent 1-h FES cycling sessions three times a week for 16 weeks. Outcome Measures: Total motor score, the Functional Independence Measure (FIM) score, the Modified Ashworth Scale for knee spasticity, temporal spatial gait parameters and oxygen consumption rate during walking. |
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Estigoni et al. 2014; Malaysia |
Population: 8 males; age 45.6 ± 15.7y; complete or incomplete spinal cord lesions between C7 and T11, AIS A to C; 10.5 ± 6 y post injury Treatment: All participants had their quadriceps muscles group stimulated during three sessions of isometric contractions separated by 5 min of recovery. The eEMG signals, as well as the produced torque, were synchronously acquired during the contractions and during short FES bursts applied during the recovery intervals. Outcome Measures: A commercial muscle dynamometer (Biodex Medical Systems) was used to measure isometric torque evoked from the electrically stimulated quadriceps. A custom-made, computerized evoked EMG acquisition system (the UniSyd e2MG) was utilized to control the stimulator and synchronize myoelectric signals with the torque outputs from the muscle dynamometer. |
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FES-assisted Stand or Gait Training | ||
Kapadia et al. 2014; Canada |
Population: 27 individuals; traumatic (>18 months) and incomplete chronic spinal cord lesions between C2 and T12, AIS C and D. Treatment: 45 minutes of therapy per session, 3 days per week, for 16 weeks (48 sessions in total). Outcome measures were assessed at baseline, 4 months, 6 months, and 12 months post baseline. Outcome Measures: Gait Measures- 6 Minute Walk, 10 Meter Walk, Assistive Device Score (ADS), Walking Mobility Scale (WMS); Balance & Mobility Measure- Time Up and Go Test (TUG); Functional Measures- Spinal Cord Independence Measure (SCIM), Functional Independence Measure (FIM); Spasticity Measure- Modified Ashworth Scale (MAS), Pendulum Test |
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Effect Sizes: Forest plot of standardized mean differences (SMD ± 95%C.I.) as calculated from pre- to post-intervention data and pre-intervention to retention/follow-up data![]() |
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Carvalho de Abreu et al. 2008, 2009; Brazil |
Population: 15 complete chronic participants with tetraplegia; injury level C4-C7; mean (SD) age 31.95(8.01) yrs with intact lower motor neurons, divided into gait training (n=8) and control (n=7) groups Treatment: Partial body-weight supported treadmill gait training with NMES, for 2 – 20min session every week for 6 months; control group performed conventional physiotherapy, and gait training without NMES for 6 months Outcome Measures: Cross-sectional area (CSA) of quadriceps, muscle hypertrophy. |
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Kern et al. 2010a; Austria |
Population: 20 males, 5 females; 22 thoracic SCI, 3 lumbar SCI; all with complete conus/cauda equina lesions Treatment: Home-based functional electric stimulation (hb-FES) 30 minutes/muscle group (gluteus, thighs, and lower leg muscles), 5 days/week for two years. Stimulation was composed of long duration biphasic impulses five days a week and was adjusted every 12 weeks following assessment by a physiatrist. Outcome Measures: Muscle cross-sectional area (CSA), knee extension torque, vastus lateralis muscle composition. |
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Kern et al. 2010b; Austria Pre-post Level 4 N=25 |
Population: 20 males, 5 females; 22 thoracic SCI, 3 lumbar SCI; all with complete conus/cauda equina lesions Treatment: Home-based functional electrical stimulation training of the vastus lateralis 5 days/week for 2 years. Long duration, high intensity biphasic simulation impulses adjusted according to excitability produced by daily hb-FES over a period of one year, eventually accompanied by daily standing-up exercises Outcome Measures: Quadriceps muscle mass, force, and structure |
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Possover et al. 2010; Switzerland
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Population: 3 thoracic patients; all presenting with spasms/spasticity of the lower limbs, and bladder spasms Treatment: Stimulation by electrodes to the sciatic and pudendal nerves and one double extradural Brindley-Finetech electrode bilaterally to the sacral nerve roots S3 and S4. Outcome Measures: Spasticity and motion of the legs. |
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Kern et al. 2005; Austria Pre-post Level 4 N=9 |
Population: 1 female, 8 males; age 20-49 yrs; complete traumatic conus cauda equina lesions; > 0.8 yrs post-injury. Treatment: Progressive PES to FES program for quadriceps to FES-assisted standing (n=4 trained ³ 2.4 years); untrained controls (n=5). Outcome Measures: Muscle biopsy of vastus lateralis (mean fiber diameter, % area covered by muscle fibers, adipocytes, connective tissue). |
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Sharif et al. 2014; Canada |
Population: 6 individuals- 3 males and 3 females; Level of injury C5 to L4; All AIS D; mean age= 60.5 ± 13.2y; years post injury= 9.3 ± 12.0y Treatment: The exercise protocol consisted of 12 weeks of FES-ambulation, with the RT600 (Restorative Therapies, Baltimore, MD), at a frequency of 3 times per week. Outcome Measures: Locomotor function was assessed via the Walking Index for Spinal Cord Injury II (WISCI II), the 6-minute walk test (6MWT), the 10-meter walk test (10MWT), and the body-weight support required during training. HRQOL was assessed via the Short Form-36, the Perceived Stress Scale, and the Center of Epidemiological Studies for Depression scale. |
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Functional Electrical Stimulation Wheelchair
Discussion
In general, all studies reviewed involving FES produced beneficial results on muscle functions such as strength and endurance or muscle structure such as increased muscle size (i.e., reduced muscle atrophy). FES may have additional benefits over PES alone. In particular, the study by Baldi et al. (1998) should be highlighted as it was the only randomized controlled trial (n=26) that compared FES (cycle ergometry exercise), PES (isometric exercise), and an untrained control group. These investigators assessed lean body mass in 3 distinct body areas (i.e. total body, lower limb, gluteal) as a marker of muscle atrophy in recently injured (approximately 10 weeks) individuals with motor complete SCI. Their results demonstrate that the FES-assisted cycling program is effective in reducing atrophy and resulted in relative increases in lean body mass in all areas after 3 and 6 months of participation. The PES-assisted isometric exercise group also reduced muscle atrophy but had intermediate results between FES and no treatment (their control group actually lost lean mass).
[su_spoiler title=”Effect Size Forest Plots of RCTs with Available Data” style=”fancy”][su_row]Click on the image to enlarge[/su_row]
[su_lightbox type=”image” src=”/wp-content/uploads/Forest_LLimb_Baldi_1998.gif”][image_with_animation image_url=”/wp-content/uploads/Forest_LLimb_Baldi_1998.gif” alt=”Effect size SMD forest plot for Baldi et al. 1998, functional electrical stimulation (FES) cycle ergometry”][/su_lightbox]
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Reversal of muscle atrophy also appears feasible in more longstanding complete or motor-complete SCI (i.e. > 2 years post-injury) as shown by increases in muscle cross-sectional area and the muscle/adipose tissue ratio using FES-cycling (Crameri et al. 2002; Scremin et al. 1999). In chronic SCI, fatigability is also a key issue due to changes in muscle fiber composition. Fornusek et al. (2013) proposed that lower FES cycling cadences may therefore be more beneficial as slower cycling could mitigate the onset of fatigue and allow greater muscle force production. Indeed, in a recent pilot study using each participant as their control, Fornusek et al. (2013) provided preliminary evidence that a lower FES cycling cadence compared to a higher cadence (10 rpm vs. 50 rpm) could be more effective at improving muscle hypertrophy and isometric strength.
NMES may also be used to strengthen the atrophied muscles to some extent prior to FES (Kern et al. 2005; Kern et al. 2010a; Kern et al. 2010b) and in some cases, FES is not possible unless NMES is first used. Kern et al. (2005) used a progressive NMES – FES program for quadriceps building eventually leading to FES-assisted standing in people with longstanding complete cauda equina injuries (>1.2 years post-injury). These investigators demonstrated increases to the overall mean fiber diameter and the proportion of total cross-sectional area covered by muscle fibers with training as compared to an untrained group. Later studies showed that FES had similar results in a larger group of participants (Kern et al. 2010a, Kern et al. 2010b). However, the feasibility of providing life-long stimulation therapy to participants with denervation injuries is uncertain.
There was one null finding associated with muscle atrophy in that Gerrits et al. (2000) employed a relatively shorter program of 6 weeks of FES-assisted cycling exercise in people with longstanding motor complete SCI (> 1-year post-injury) and found no change in muscle size. These non-significant results might be due to the relative insensitivity of the measure of thigh circumference, especially with the short intervention period and the absence of a control group for comparison purposes.
In addition to improving muscle properties, FES-cycling can improve work output and endurance (Crameri et al. 2002; Gerrits et al. 2000). For example, Gerrits et al. (2000) used a short (6 weeks) pre-post trial of FES-assisted cycling intervention in people with motor complete SCI and found an increased resistance to fatigue in the quadriceps muscle and greater work output.
Some mechanistic investigations have been conducted which help to explain some of these adaptations to muscle morphology and function with ongoing electrical stimulation exercise programs. For example, using FES-assisted cycling, Koskinen et al. (2000) demonstrated an increase in total collagen content as well as up- and down-regulation of proteins consistent with muscle-building activity. Others have noted an adaptive response to FES-assisted cycling exercise that serves to limit or alter the shift in the oxidative properties or fibre type composition of muscles that typically occurs following SCI (Crameri et al. 2002).
Conclusion
There is level 2 evidence (Baldi et al. 1998) that FES-assisted cycling exercise prevents and reverses lower limb muscle atrophy in individuals with recent (~10 weeks post-injury) motor complete SCI and to a greater extent than PES.
There is level 4 evidence (Scremin et al. 1999; Crameri et al. 2002) that FES may partially reverse the lower limb muscle atrophy found in individuals with long-standing (> 1-year post-injury) motor complete SCI.
There is level 4 evidence (Gerrits et al. 2000) that FES-assisted cycle exercise may increase lower limb muscular endurance.