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Evaluating functional electrical stimulation (FES) cycling on cardiovascular, musculoskeletal and functional outcomes in adults with multiple sclerosis and mobility impairment: A systematic review
Corresponding author at: Institute for Clinical Exercise and Health Science, School of Health and Life Sciences, University of the West of Scotland, South Lanarkshire, G72 0LH.
Institute for Clinical Exercise and Health Science, School of Health and Life Sciences, University of the West of Scotland, South Lanarkshire, Scotland
Institute for Clinical Exercise and Health Science, School of Health and Life Sciences, University of the West of Scotland, South Lanarkshire, Scotland
Institute for Clinical Exercise and Health Science, School of Health and Life Sciences, University of the West of Scotland, South Lanarkshire, Scotland
Institute for Clinical Exercise and Health Science, School of Health and Life Sciences, University of the West of Scotland, South Lanarkshire, Scotland
Functional electrical stimulation (FES) cycling is used by people with MS (PwMS).
•
A systematic review evaluated FES cycling in PwMS with a mobility impairment.
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9 studies met the inclusion criteria, with outcome data for n = =76 unique participants.
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Overall study quality was poor, with limitations in study protocols and outcomes.
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There is insufficient evidence to support FES cycling for cardiovascular risk.
Abstract
Background
People with Multiple Sclerosis (PwMS) are at an increased risk of diseases associated with low levels of physical activity (PA). Deconditioning may lead to an acceleration in the development of secondary complications from MS, impairing physical function and exacerbating disease progression. Functional Electrical Stimulation (FES) Cycling may provide a suitable lower limb exercise intervention for PwMS with mobility impairment. The effects of FES cycling on cardiovascular, musculoskeletal and functional outcomes for PwMS with mobility impairment are yet to be investigated to date.
Objective
The objective of this review was to systematically examine the outcomes of PwMS with mobility impairment following FES cycling intervention.
Methods
A systematic search of four electronic databases (MEDLINE, Web of Science, CINAHL and PEDro) from their inception to 8th January 2019 was performed. Inclusion criteria was (1) include human participants with definite diagnosis of MS (2) participants had to be aged 18 years or older (3) include participants with mobility impairment (determined as an average participant EDSS ≥ 6.0) (4) evaluate FES cycling as an intervention study.
Results
Initial searches found 1163 studies. 9 of which met the full inclusion criteria: 5 pre-post studies with no control group, 2 randomised controlled trials (RCTs), 1 retrospective study and 1 case study. Two studies had the same participant group and intervention but reported different outcomes. Outcome data was available for n = =76 unique participants, with n = =82 completing a FES cycling intervention. Of the n = =4 papers with clear dropout rates, pooled dropout rate was 25.81%. Two papers reported non-significant improvements in aerobic capacity following a FES cycling intervention. Four papers reported no change in lower limb strength and two papers reported significant reductions in spasticity post training. Four studies failed to provide information regarding adverse events with the other studies reporting n = =10 adverse events across 36 participants.
Conclusion
Findings suggest FES cycle training may reduce CVD risk alongside trends for a reduction in spasticity post training, however the low quality of the literature precludes any definitive conclusions. FES cycle training appears to be well tolerated in PwMS with mobility impairment, with no serious adverse events.
Multiple Sclerosis (MS) is a chronic autoimmune disease affecting the Central Nervous System (CNS) and is characterised by inflammation and neurodegeneration of the myelin sheath, axons and grey and white matter (
High-intensity resistance training in multiple sclerosis - An exploratory study of effects on immune markers in blood and cerebrospinal fluid, and on mood, fatigue, health-related quality of life, muscle strength, walking and cognition.
Muscular, cardiac, ventilatory and metabolic dysfunction in patients with multiple sclerosis: implications for screening, clinical care and endurance and resistance exercise therapy, a scoping review.
). MS presents as symptoms of fatigue and impairment of both autonomic and somatic systems which have a deleterious impact on walking performance (and other types of physical activity), overall health, quality of life and ability to complete activities of daily living (ADLs) (
In line with these limitations, people with MS (PwMS) frequently fail to engage in the recommended amounts of moderate-to-vigorous physical activity (MVPA) necessary to accrue health benefits (
). Moreover, studies of PwMS also report that they experience both real and perceived barriers to engaging in physical activity (PA), which when combined with reductions in physical function, may promote an inactive lifestyle resulting in physical deconditioning (
Muscular, cardiac, ventilatory and metabolic dysfunction in patients with multiple sclerosis: implications for screening, clinical care and endurance and resistance exercise therapy, a scoping review.
The consequences of insufficient PA and deconditioning may be particularly problematic in this cohort. PwMS are not immune to the increased risk of cardiovascular disease (CVD) occurring as a result of low levels of PA (
). Indeed, deaths from secondary chronic conditions such as hypertension, increased cholesterol and diabetes are common, and the mortality rate in PwMS is estimated as being between 1.7 to 3.5 times greater than that of the general population (
Causes of death in patients with multiple sclerosis and matched referent subjects: a population-based cohort study: causes of death in patients with MS.
). In addition, deconditioning may lead to an acceleration in the development of secondary complications from MS in an interdependent manner. Deconditioning has been suggested to impair physical function and exacerbate disease progression, resulting in further reductions in levels of PA, and an associated cycle of decline in health (
Muscular, cardiac, ventilatory and metabolic dysfunction in patients with multiple sclerosis: implications for screening, clinical care and endurance and resistance exercise therapy, a scoping review.
). An EDSS score of 6.0 is an identifiable milestone on the scale, whereby the individual can walk a maximum of 100 m without stopping, even with the support of a unilateral assistive device (
). As EDSS increases, PwMS are likely to participate in reduced amount of PA in comparison to those with lower EDSS, thus PwMS of disability levels of EDSS ≥ 6.0 are less likely to meet MVPA guidelines and have a greater risk of experiencing CV comorbidities (
). For example, vascular comorbidities have been significantly correlated to an increased risk of mobility impairment and speed of disability progression (
Effects of exercise training on fitness, mobility, fatigue, and health-related quality of life among adults with multiple sclerosis: a systematic review to inform guideline development.
). Whilst both upper body and lower body exercises may have the potential to elicit cardiovascular adaptions in PwMS, it is important to note that the peripheral adaptation and conditioning of the lower limbs remain vital for PwMS's mobility and contribute to their ability to complete personal and instrumental ADLs (
). Lower body function is of particular importance in enabling PwMS to remain independent since it supports the completion of personal ADLs such as self-care, transfer and locomotion (
). The intervention applies electrical stimulation to the lower limb muscles, which is appropriately timed to generate cyclical contractions to propel the cycle ergometer (
). This intervention has reported to benefit other neurological conditions, such as persons with incomplete or complete spinal cord injury (SCI), including increased lower limb skeletal muscle mass, muscular strength, and endurance whilst also improving aerobic capacity, and glucose metabolism (
). In PwMS, FES cycling may support higher exercise intensities, enabling greater engagement with the level of MVPA than would be otherwise possible with passive leg cycling; increasing the potential for cardiovascular conditioning (
Cardiorespiratory demand of acute voluntary cycling with functional electrical stimulation in individuals with multiple sclerosis with severe mobility impairment.
). This methodology therefore, may be a feasible option for reducing comorbid CVD risk.
Over the last decade, FES cycling has attracted an increased number of investigations due to the potential benefit this intervention has for PwMS, both in terms of supporting their physical functioning, and reducing CVD risk. To date, the evidence remains unclear as to the efficacy of FES cycling to support PwMS in maintaining cardiorespiratory and musculoskeletal health, and preventing the development of further comorbidities. No systematic evaluation has been conducted in this group. Given that FES cycling is a more appropriate intervention for those with higher levels of mobility impairment, the aim of this review is to systematically examine cardiovascular, musculoskeletal and functional outcomes in PwMS with mobility impairment following a FES cycling intervention.
2. Methodology
2.1 Search strategy
This systematic review was conducted was in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRIMSA) statement (
). A comprehensive literature search was performed in order to examine the effect of FES cycling on cardiovascular, musculoskeletal and functional outcomes in PwMS. Four electronic databases (MEDLINE, Web of Science, CINAHL and PEDro) were searched from their inception to 8th January 2019. Search terms used were as follows: (“Multiple Sclerosis” OR “Progressive MS” OR “Relapsing Remitting MS”) AND (“NMES” OR “FES” OR “ESAC” OR “neuromuscular stimulation” OR “electrical stimulation” OR “stimulation-assisted cycl*” OR “assisted cycl*”). Table 1 provides an example of the search strategy. Filters were applied so that only research articles and articles that were peer-reviewed would be retrieved.
Table 1Sample search strategy.
#1
“Multiple Sclerosis” OR “Progressive MS” OR “Relapsing Remitting MS” [all fields]
#2
“NMES” OR “FES” OR “ESAC” OR “neuromuscular stimulation” OR “electrical stimulation” OR “stimulation-assisted cycl*” OR “assisted cycl*” [all fields]
FES cycling utilises a commercially available motorised ergometer (e.g. RT300, Restorative Therapies Inc, Baltimore, MD, USA), typically accessed from a seated position (
). Stimulation electrodes are placed on the skin, typically above the quadriceps, hamstrings and glutei and a bilateral current is delivered to the muscles providing timed and cyclical stimulation necessary to produce a cycling motion (
). A target cadence is predetermined on the ergometer with suitable software amending the electrical stimulation and ergometer's resistance based on muscle fibre recruitment and fatigability (
To be included in this review, the study had to (1) include human participants with definite diagnosis of MS (2) participants had to be aged 18 years and over (3) include participants with an average EDSS 6.0 or above, or an equivalent mobility impairment (4) evaluate FES cycling as an intervention study. Since the number of qualifying studies was anticipated to be small, no restrictions were placed on the type of study included in this review, and all qualifying studies were included regardless of study quality.
2.4 Study selection
Following searches of the relevant databases, results were imported into bibliographic software (Zotero: V 5.0.60, Fairfax, VA, USA). Subsequently, articles were screened to remove duplicates. Two authors (JS and NS) independently conducted a literature search and screened the title and abstracts of relevant papers to remove studies which clearly did not meet the inclusion criteria. Where it was not clear in the title or abstract if the study was suitable for inclusion, the full text was read. Using the inclusion criteria, both authors independently generated a list of eligible studies.
2.5 Data extraction
In addition to bibliographic data, the following information was extracted from each article by JS and verified by NS: (i) participant data (Table 2) (ii) intervention protocols (Table 3) (iii) intervention outcomes (Table 4).
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Inclusion criteria of all papers equated to mean EDSS ≥ 6.0. 1, demographic data only given for those that completed the intervention; 2, demographic data not split by control and intervention; 3, demographic data only given for those for those with measurable mVO2; 4, EDSS unknown for n = =1; 5; two papers appear to be same participants and same intervention and have been grouped to prevent double counting; F, female; M, male; PP, Primary Progressive; RR, Relapsing Remitting; SP, Secondary Progressive; P, Progressive; Con, Control Group; FES, FES Cycling Group; NR, Not Reported. Data are mean ± SD unless otherwise stated.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
↑ 0.14 Nm Increments (if 3 sessions for 30 mins continuously)
Clinical
Y
Stimulation gradually increased to cause cycling at 50 rpm. If participant was unable to cycling for 30-mins, the cycle entered a passive mode for remainder of session
Theravital Cycle Ergometer & Constant Current 8-channel Stimulator
Quadriceps & Hamstrings
NR
F = 20 Hz; Max SA = =127 mA, Constant PW = =300 μs
12–18
3 x a week
2
6
72–108
I
NR
Clinical
Y
n = =11 received conventional physiotherapy 5 times a week, and outpatient n = =1 attended conventional physiotherapy sessions twice a week. Highest cycling resistance was selected that would allow the subject to tolerate well 12–18 min of active ergometric pedalling (with and without stimulation), but at the same time not become too exhausted.
1, two papers appear to be same participants and same intervention and have been grouped to prevent double counting; F, frequency; PW, pulse width; PD, phase duration; SA, stimulation amplitude; NR, not reported; ABRT, Activity Based Restorative Therapy; RT300, Restorative Therapies Inc, Baltimore, MD, USA; Motomed Viva 1.5, Reck Medixintechnik GmBH, Betzenweiller, Germany; Motomed FES Ergometer, Reck Medixintechnik GmBH, Betzenweiller, Germany; Portable Neuromuscular Electrical Stimulation Units 300PV, Empi, St Paul, MN, USA; SWISS Stim, Valmed, Sion, Swizerland; Constant Current 8-channel Stimulator, Krauth + Timmermann, Germany; Theravital, Medica-Medizintechnik Ltd, Hochdorf, Germany.
↑ Resistance or Time during FESC ↔ Power during FESC, Lower Limb Strength (Combined MMT of Bilateral HF, KF, KE and AD), Spasticity (MAS), Fatigue (MFIS), Pain (MOS PES), Mental Health (MHI), QOL (MSQLI)
↔ T25FW, MSWS-12, 2MW, TUG, VO2peak, WRpeak, KE Strength, KF Strength, Leg FFM, Leg FM, Leg % Fat, Leg BMD, Cognition (SDMT), Fatigue (FSS, MFIS), Pain (SF-MPQ), QOL (MSIS-29)
7 (6 Min, 1 Mod)
Min (n = =6): Skin Irritation/Redness n = =3, Non-Debilitating Fatigue n = =2, Increased Muscle Spasticity n = =1 Mod (n = =1): Fall Outside of Training
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Study quality was appraised using four different tools based on study type. The majority of studies were evaluated using the tools designed by the National Heart, Lung and Blood Institute (NHLBI), specifically cohort studies (
Fig. 1 denotes the literature search and screening process undertaken. The initial search found 1162 potential articles supplemented with 1 study from an external source; with 9 of these meeting the inclusion criteria. Of these, 5 were pre-post studies with no control group (
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
). As a result, there was a total of 9 papers which underwent quality assessment, however these 9 papers describe 8 different interventions. For clarity, the remainder of this review will refer to papers, not interventions.
Fig. 1PRISMA flow diagram of literature search and review process.
). Two papers did not report participant EDSS however their inclusion criteria approximately equated to that of participants with mobility impairment and EDSS ≥ 6.0 (
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
). One study only provided age range therefore from the other 8 papers with extractable data, the mean participant age was 50.77 ± 10.21 years and disease duration 17.14 ± 8.35 years. Two papers, which reported on the same participants reported body height and mass (
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
). In the four remaining papers a total of 23 out of 31 participants who started the FES cycling protocol completed and 8 dropped out; resulting in a pooled dropout rate of 25.81% (
One paper only provided demographic information for those participants where the main outcome, muscle oxygen consumption (mVO2), was successfully measured (
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
). Resting and Peak Heart Rate (HR) was provided in one paper, however these were from baseline assessments and not measured pre and post intervention (
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
). Of these, the protocol for four papers was to reach a point where a participant could complete 30 min of FES cycling at a target cadence of 35–50 rpm (
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Lower body strength was commonly measured in the Knee Extensors (KE), Knee Flexors (KF), Hip Extensors, Hip Flexors and/or Dorsiflexors or in combined tests (
). One study, that observed a significant increase in thigh volume failed to measure changes in muscle mass or fat free mass in order to ascertain the cause of such increase (
). Three papers reported a reduction in spasticity post FES cycling; two papers described significant improvements in spasticity directly post FES cycling (
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
). Two papers both reported a moderate adverse event which caused a participant to drop out; both of which were falls noted by researchers as unrelated to the intervention (
The study quality assessment tools indicated that papers consistently had unclear or insufficient sample sizes to provide confidence in the findings (Table 5, Table 6, Table 7, Table 8). The largest sample size was that of a retrospective study, which contained 40 participants (
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Table 6Quality assessment of case reports and case series.
Study
Domain
Selection
Ascertainment
Causality
Reporting
Patient represent whole experience of the investigator or is the selection method unclear to the extent that other patients with similar presentation may not have been reported?
Exposure adequately ascertained?
Outcome adequately ascertained?
Other alternative causes that may explain the observation ruled out?
Challenge/rechallenge phenomenon?
Dose–response effect?
Follow-up long enough for outcomes to occur?
Case described with sufficient details to allow other investigators to replicate the research or to allow practitioners make inferences related to their own practice?
The aim of this systematic review was to conduct a comprehensive literature search examining the effect of FES cycle training on cardiovascular, musculoskeletal and functional outcomes in PwMS and EDSS ≥ 6.0. The heterogeneity in outcome measures across the nine papers prevented a meta-analysis. The low quality of the literature base precludes any definitive conclusions regarding the efficacy of FES cycle training in improving cardiovascular health in PwMS and higher EDSS scores. In the present review, one of the main findings is that FES cycle training appears to be well tolerated in PwMS with mobility impairment, with no serious adverse events.
4.1 Cardiorespiratory performance
Aerobic capacity is a strong indicator of cardiovascular fitness and associated CVD risk in PwMS (
Muscular, cardiac, ventilatory and metabolic dysfunction in patients with multiple sclerosis: implications for screening, clinical care and endurance and resistance exercise therapy, a scoping review.
). Although definitive data is lacking, it is plausible that those with the greatest level of mobility impairment are subject to an increased risk of CVD, with a significant correlation between disease progression and aerobic capacity (
); the majority of this work has been in those with EDSS < 6.0, whereas those with higher mobility impairment (e.g. EDSS ≥ 6.0) have been poorly researched in the literature (
). FES cycling has the potential to increase the dose of exercise attainable in PwMS with higher mobility impairment, and could therefore increase aerobic capacity and PA (
Cardiorespiratory demand of acute voluntary cycling with functional electrical stimulation in individuals with multiple sclerosis with severe mobility impairment.
). However, despite this potential, from the evidence of this review, the effectiveness of FES cycling in improving aerobic capacity is equivocal. Only two papers recorded valid objective measures of aerobic capacity (
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
). One paper found a significant increase in peripheral oxygen consumption (mVO2) following 360 min of FES cycle training across 4 weeks while the other study reported trends for improvement in VO2peak that fell short of statistical significance (
) however no papers reported any improvements. This apparent limited effectiveness may be due to the lack of specificity since walking performance is also reliant on balance and lower limb strength asymmetries (
). Moreover, whether different doses of exercises would be more effective (e.g. longer duration or higher intensity) remain to be determined. Indeed, the high level of variability within the FES cycling interventions makes it difficult to attribute any changes to a specific protocol. While four of the nine papers had similar protocols (
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Obesity and cardiovascular disease: pathophysiology, evaluation, and effect of weight loss: an update of the 1997 American heart association scientific statement on obesity and heart disease from the obesity committee of the council on nutrition, physical activity, and metabolism.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
Pilot study: evaluation of the effect of functional electrical stimulation cycling on muscle metabolism in nonambulatory people with multiple sclerosis.
). The other paper provided more nuanced assessment of fat free mass, fat mass and bone density (measured utilising a bone densitometer) and reported no change following FES cycle training (
) makes it difficult to assess the role of FES cycle training in preventing obesity as a CVD risk factor.
However, the accuracy of standard BMI thresholds for persons with lower limb impairment have been questioned since BMI does not distinguish between muscle and fat compartments (
). Consequently, in persons with reduced lower limb muscle tone and bone density, BMI thresholds designed for able bodied persons may underestimate the risk of increased body fat (
). In particular, this is important for PwMS since disease progression and duration are both strongly correlated with spasticity and reductions in mobility (
). FES cycling has been suggested as a possible support mechanism for spasticity since it is associated with a reduction in spastic muscle tone in persons with SCI (
) but the degree to which this is the case with PwMS remains to be determined.
Spasticity was the most commonly recorded measure, and FES cycle training appears to acutely improve symptoms of spasticity but this does not appear to translate into medium term effects (defined as approximately 48 h after training) (
). No papers evaluated longer term effects of FES cycling and thus the effect of FES cycle training in reducing spasticity > 48 h remains unclear. The MAS was the most frequently utilised measurement within this review and is commonly used to measure spasticity in persons with MS (
). That being said, a number of limitations are reported with the MAS related to inter-rater reliability, sensitivity to change and insufficient guidelines regarding its use (
). Future studies should look to use more robust measures of spasticity with less subjectivity.
4.4 Lower limb muscular strength
Lower Limb Muscular Strength is correlated to walking performance in PwMS and is important in enabling PwMS to complete personal and instrumental ADLs (
). Clearly, one aim of FES cycling is to stimulate the musculature of the lower limbs thus aiming to increase strength, reduce the rate of decline and preserve function in the lower body; with the potential to support PwMS's ability to maintain ADLs. Moreover when this lower limb function is lost, this in turn translates into greater loads being placed on the upper body and a higher risk of chronic upper body injury (
). Four papers assessed this outcome, however no improvements in lower body muscular strength following FES cycle training were found within the present review (
Clearly, cycling is generally considered to be aerobic in nature and may be considered to produce modest increases in muscular strength. Indeed, to elicit skeletal muscle hypertrophy in healthy populations using aerobic exercise, the optimum exercise intensity is suggested as a minimum of 70% HR reserve (HRR), 4 times a week for 30 min (
). Given that none of the papers included in this review had sufficient exercise volume to equate to this, nor was %HRR or %VO2peak set as a target within the interventions, it is perhaps not surprising that no changes in strength were noted. Moreover, FES cycling can be considered as a dynamic training modality with moderate speeds of muscle contraction. However, in all cases, strength was assessed isometrically using semi-quantitative (
) methods. It is well established that changes in strength are specific to the speed and type of contraction used in training, and outcome measures should reflect the training mode (
), which was not the case in the interventions used in the papers.
Consequently, the conclusion that FES cycling does not improve strength in PwMS with EDSS ≥ 6.0 should be viewed with caution, and must be re-evaluated with more appropriate protocols, given the mismatch between training stimulus and outcome assessment. Evidence has shown that PwMS and mobility impairment can reach higher %HRpeak during an acute bout of FES cycling in comparison to passive leg cycling (76.4%HRpeak vs 55.5%HRpeak) (
Cardiorespiratory demand of acute voluntary cycling with functional electrical stimulation in individuals with multiple sclerosis with severe mobility impairment.
). This supports the theory that FES cycling protocols have the potential to provide increases in strength. A further limitation is that of the papers in this review, only two interventions were longer than 10 weeks and in both cases, sample sizes were too small to make meaningful interpretations (n = =4 completed in both cases) (
). Another consideration for those papers that measured muscular strength, is that the majority had no control group. As disease progression is correlated to reductions in lower limb muscular strength, future research should look to determine if maintenance of muscular strength is clinically meaningful over time in comparison to controlled counterparts (
Accurate reporting of adverse events is particularly important in this group since there are few intervention papers evaluating the benefits of PA in persons with EDSS ≥ 6.0 (
Effects of exercise training on fitness, mobility, fatigue, and health-related quality of life among adults with multiple sclerosis: a systematic review to inform guideline development.
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