Resistance Training for Muscle Weakness in Multiple Sclerosis: Direct Versus Contralateral Approach in Individuals With Ankle Dorsiflexors' Disparity in Strength

Suspension training improves bilateral isometric strength asymmetry of knee muscles in people with multiple sclerosis

INTRODUCTION

Most people with multiple sclerosis are diagnosed with bilateral strength asymmetry in the lower limbs. Strength asymmetry increases muscle metabolic cost, muscle fatigability, postural instability, gait disturbance, imbalance, and risk of falling, and negatively affects the quality of life in PwMS. So far, the effects of rehabilitation exercises on reducing the asymmetric index in this population has not been studied convincingly. The purpose of this study was to investigate the effect of suspension exercise on bilateral isometric strength asymmetry of knee muscles in patients with multiple sclerosis.

MATERIALS & METHODS

In this randomized controlled trial, twenty-seven female patients were purposively selected as the statistical sample and randomly divided into the control (n = 13, age: 34.72 ± 5.01 years) and exercise (n = 14, age: 37.62 ± 4.58 years) groups. The control group received routine care while the exercise group received the suspension exercise protocol. Isometric muscle strength and bilateral asymmetry were measured at baseline and after 8 weeks. The Biodex isokinetic dynamometer was used to measure the maximal voluntary isometric contraction of the flexor and extensor muscles of the knee. The analysis of covariance was used to analyze the data.

RESULTS

The isometric strength of the knee extensor muscles in the weak leg at the angle of 20° and in both legs at the angle of 70° in the exercise group improved significantly. Furthermore, the strength of the knee flexor muscles in the exercise group was increased. The amount of bilateral strength asymmetry in the knee flexor and extensor muscles at the angle of 70° significantly decreased in the exercise group.

DISCUSSIONS & CONCLUSIONS

These data suggest that suspension training is a practical approach to manage bilateral asymmetry in knee flexor and extensor muscle strength in patients with an EDSS of less than four.

Cross-education of lower limb muscle strength following resistance exercise training in males and females: A systematic review and meta-analysis

Cross-education describes the training of one limb that leads to performance enhancements in the contralateral untrained limb, driven by neural changes rather than muscle adaptation. In this systematic review and meta-analysis, we aimed to evaluate the efficacy of cross-education (vs. a control group) via resistance exercise training (RET) for improving muscle strength in the untrained lower limb of healthy males and females. A literature search from inception to September 2023 was conducted using MEDLINE (via PubMed), the Cochrane Library (CENTRAL), Web of Science (Core Database), Scopus, EBSCO-host, and Ovid-EMBASE. Independent screening, data extraction and quality assessment were conducted. The measured outcomes were change in one-repetition maximum (1-RM) load, maximum voluntary contraction (MVC), and concentric, eccentric and isometric peak torque. Change in muscle structure (pennation angle and muscle thickness) was also analysed. A total of 29 studies were included. The pooled effect size from the random-effects model shows that cross-education significantly increased 1-RM compared to the control group (standardised mean difference (SMD): 0.59, 95% CI: 0.22-0.97; P = 0.002). Cross-education also significantly improved MVC (SMD: 0.55, 95% CI: 0.16-0.94; P = 0.006), concentric (SMD: 0.61, 95% CI: 0.39-0.84; P < 0.00001), eccentric (SMD: 0.39, 95% CI: 0.13-0.64; P = 0.003) and isometric (SMD: 0.45, 95% CI: 0.26-0.64; P < 0.00001) peak torque, each compared to the control group. When RET was categorised as eccentric or concentric, subgroup analysis showed that only eccentric training was associated with significantly increased isometric peak torque via cross-education (SMD: 0.37, 95% CI: 0.13-0.61; P = 0.003) (concentric, SMD: 0.33, 95% CI: -0.09 to 0.74; P = 0.12). This systematic review and meta-analysis emphasise the potency of cross-education for improving lower limb muscle strength. These findings have potential implications for clinical situations of impaired unilateral limb function (e.g., limb-casting or stroke). Future work exploring the mechanisms facilitating these enhancements will help to develop optimised rehabilitation protocols.

Is Resistance Training an Option to Improve Functionality and Muscle Strength in Middle-Aged People with Multiple Sclerosis? A Systematic Review and Meta-Analysis

Background: Currently, it is essential to adopt physical therapy strategies, such as resistance training, to enhance muscle strength and gait in middle-aged individuals (ages 45-65) suffering from Multiple Sclerosis. This is crucial in combating the typical symptoms of neurodegenerative diseases associated with functional loss. The objective of this study is to determine the effects of resistance training interventions on walking and muscle strength in middle-aged people with Multiple Sclerosis. Methods: A systematic review with meta-analysis was conducted by searching specific keywords in the PubMed, Scopus, Cochrane, and Web of Science databases. For inclusion, studies had to incorporate resistance training as a primary or significant component of the overall intervention for middle-aged patients with MS. Out of the 3675 articles identified, 12 randomized clinical trials met the criteria for inclusion in the review, with resistance training being a consistent feature in all of them. Results: Muscle strength and gait were evaluated as the main variables, with fatigue and the quality of life as secondary variables. This review reveals that resistance training significantly improves muscle strength. Resistance training achieves modest and non-significant improvements in gait. Notably, studies combining resistance training with motor control exercises achieve results of greater clinical significance in terms of gait. However, resistance training yields variable positive effects on perceived fatigue and the quality of life. Conclusion: Resistance training is useful for improving muscle strength; however, walking needs to be combined with motor control training.

Ankle dorsiflexion asymmetry and the relationship with walking performance in people with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a neurological disease characterized by demyelination disrupting the central nervous system. Persons with MS may exhibit symptomatic strength asymmetry (SA) that impacts motor gait and ankle mobility. The purpose of the present study was to investigate ankle dorsiflexion SA in people with MS and its relationship to functional performance.

RESEARCH QUESTION

Is their a difference in dorsiflexion SA in MS participants compared to healthy individuals and does it impact functional performance?

METHODS

13 MS participants (EDSS 3.5 + 1.8) and 13 age matched NON-MS participants underwent maximal isometric (MVC) dynamometry testing for ankle dorsiflexion in both limbs to determine SA. Participants performed three functional tasks of walking performance.

RESULTS

There was a significant intra-limb MVC difference in the MS group, and significantly greater isometric SA (p < 0.007) and isokinetic SA (p < 0.04) in the MS group compared to healthy individuals. The MS group exhibited significant correlations between outcomes of functional walking performance with isokinetic but not isometric SA. There was no significant correlation between disability status and functional task performance.

SIGNIFICANCE

Ankle dorsiflexion SA is negatively correlated with functional performance in MS participants. MS disability status was not a predictor of functional task performance, and symptom testing may be appropriate to assess walking ability in persons with MS.

Exercise prescription and strategies to promote the cross-education of strength: a scoping review

The cross-education of strength is moderated by exercise design and prescription in clinical and non-clinical populations. This review synthesizes the available evidence regarding exercise design strategies for unilateral resistance training and provides evidence-based recommendations for the prescription of unilateral training to maximize the cross-education of strength. Greater insights regarding the timing and effectiveness of cross-education interventions in clinical scenarios will strengthen the use of unilateral resistance training for individuals who may benefit from its use.

Physical Activity in Multiple Sclerosis: Meeting the Guidelines at the Time of the COVID-19 Pandemic

BACKGROUND AND PURPOSE

Regular physical activity (PA) helps to reduce the severity of physical and mental symptoms and improves quality of life in people with multiple sclerosis (PwMS). Based on current evidence and expert opinion, the recent multiple sclerosis guidelines recommend at least 150 minutes/week of PA. This study presents the results of a survey analyzing whether and how PwMS met the guidelines before and during the pandemic.

METHODS

We developed and disseminated an international online survey between December 2020 and July 2021, investigating changes in self-reported PA type, duration, frequency, and intensity due to the COVID-19 outbreak in PwMS with differing disability levels.

RESULTS

Among respondents (n = 3810), 3725 were eligible. The proportion of those who conducted at least one activity decreased with increasing disability level at both time points (pre and during). Overall 60% of respondents met the guidelines before the pandemic (mild: 64.43%; moderate: 51.53%; severe: 39.34%; χ 2(2) = 109.13, P < 0.01); a reduction of approximately 10% occurred during the pandemic in all disability groups (mild: 54.76%; moderate: 42.47%; severe: 29.48%; χ 2(2) = 109.67, P < 0.01). Respondents with higher disability participated more in physical therapy and less in walking, cycling, and running at both time points. Most respondents reported practicing PA at a moderate intensity at both time points; frequency and duration of sessions decreased as disability level increased.

DISCUSSION AND CONCLUSIONS

The percentage of those meeting the guidelines reduced with increasing disability level and during the pandemic. PA type and intensity varied widely across the disability categories. Interventions accounting for disability level are required to enable more PwMS to reap the benefits of PA.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A415 ).

Neurorehabilitation in Multiple Sclerosis-A Review of Present Approaches and Future Considerations

Multiple sclerosis is an increasingly prevalent disease, representing the leading cause of non-traumatic neurological disease in Europe and North America. The most common symptoms include gait deficits, balance and coordination impairments, fatigue, spasticity, dysphagia and an overactive bladder. Neurorehabilitation therapeutic approaches aim to alleviate symptoms and improve the quality of life through promoting positive immunological transformations and neuroplasticity. The purpose of this study is to evaluate the current treatments for the most debilitating symptoms in multiple sclerosis, identify areas for future improvement, and provide a reference guide for practitioners in the field. It analyzes the most cited procedures currently in use for the management of a number of symptoms affecting the majority of patients with multiple sclerosis, from different training routines to cognitive rehabilitation and therapies using physical agents, such as electrostimulation, hydrotherapy, cryotherapy and electromagnetic fields. Furthermore, it investigates the quality of evidence for the aforementioned therapies and the different tests applied in practice to assess their utility. Lastly, the study looks at potential future candidates for the treatment and evaluation of patients with multiple sclerosis and the supposed benefits they could bring in clinical settings.

Effects and optimal dosage of resistance training on strength, functional capacity, balance, general health perception, and fatigue in people with multiple sclerosis: a systematic review and meta-analysis

PURPOSE

To analyze the effectiveness of resistance training programs (RTP) on strength, functional capacity, balance, general health perception, and fatigue for people with Multiple Sclerosis (MS) and to determine the most effective dose of RTP in this population.

METHODS

Studies examining the effect of RTP on strength, functional capacity, balance, general health perception, and fatigue in MS patients were included. 44 studies were included. The meta-analysis, subgroup analysis and meta-regression methods were used to calculate the mean difference and standardized mean difference.

RESULTS

Significant group differences were observed in knee extensor (p = 0.01) and flexor (p < 0.001), but not in 1-repetition maximum. Regarding functional capacity and balance, differences between groups, in favour of the RTP group, were found in the Timed Up and Go Test (p = 0.001), walking endurance, (p = 0.02) gait speed (p = 0.02) and balance (p = 0.02). No significant differences between groups were observed in fatigue or general health perception. The results regarding the optimal dose are inconsistent.

CONCLUSIONS

RTP improves strength, functional capacity, balance, and fatigue in people with MS. Registration: (PROSPERO): CRD42020182781Implications for rehabilitationResistance training is a valid strategy to improve isometric strength and functional capacity in MS patients.RTP using long durations (more than 6 weeks), high intensity (more than 80% 1-RM) and two-day weekly training frequency may be a correct stimulus to improve strength, functional capacity, balance, and fatigue in people with MS.Trainers and rehabilitators should consider these indicators in order to maximize muscular and functional adaptations in this population.

Neural mechanisms mediating cross education: With additional considerations for the ageing brain

CALVERT, G.H.M., and CARSON, R.G. Neural mechanisms mediating cross education: With additional considerations for the ageing brain. NEUROSCI BIOBEHAV REV 21(1) XXX-XXX, 2021. - Cross education (CE) is the process whereby a regimen of unilateral limb training engenders bilateral improvements in motor function. The contralateral gains thus derived may impart therapeutic benefits for patients with unilateral deficits arising from orthopaedic injury or stroke. Despite this prospective therapeutic utility, there is little consensus concerning its mechanistic basis. The precise means through which the neuroanatomical structures and cellular processes that mediate CE may be influenced by age-related neurodegeneration are also almost entirely unknown. Notwithstanding the increased incidence of unilateral impairment in later life, age-related variations in the expression of CE have been examined only infrequently. In this narrative review, we consider several mechanisms which may mediate the expression of CE with specific reference to the ageing CNS. We focus on the adaptive potential of cellular processes that are subserved by a specific set of neuroanatomical pathways including: the corticospinal tract, corticoreticulospinal projections, transcallosal fibres, and thalamocortical radiations. This analysis may inform the development of interventions that exploit the therapeutic utility of CE training in older persons.

Outcome measures used in trials on gait rehabilitation in multiple sclerosis: A systematic literature review

Background

Multiple Sclerosis (MS) is associated with impaired gait and a growing number of clinical trials have investigated efficacy of various interventions. Choice of outcome measures is crucial in determining efficiency of interventions. However, it remains unclear whether there is consensus on which outcome measures to use in gait intervention studies in MS.

Objective

We aimed to identify the commonly selected outcome measures in randomized controlled trials (RCTs) on gait rehabilitation interventions in people with MS. Additional aims were to identify which of the domains of the International Classification of Functioning, Disability and Health (ICF) are the most studied and to characterize how outcome measures are combined and adapted to MS severity.

Methods

Pubmed, Cochrane Central, Embase and Scopus databases were searched for RCT studies on gait interventions in people living with MS according to PRISMA guidelines.

Results

In 46 RCTs, we identified 69 different outcome measures. The most used outcome measures were 6-minute walking test and the Timed Up and Go test, used in 37% of the analyzed studies. They were followed by gait spatiotemporal parameters (35%) most often used to inform on gait speed, cadence, and step length. Fatigue was measured in 39% of studies. Participation was assessed in 50% of studies, albeit with a wide variety of scales. Only 39% of studies included measures covering all ICF levels, and Participation measures were rarely combined with gait spatiotemporal parameters (only two studies).

Conclusions

Selection of outcome measures remains heterogenous in RCTs on gait rehabilitation interventions in MS. However, there is a growing consensus on the need for quantitative gait spatiotemporal parameter measures combined with clinical assessments of gait, balance, and mobility in RCTs on gait interventions in MS. Future RCTs should incorporate measures of fatigue and measures from Participation domain of ICF to provide comprehensive evaluation of trial efficacy across all levels of functioning.

Strength training for people with multiple sclerosis and the current recommendations

Recent guidelines recommend strength and conditioning training for patients with multiple sclerosis (MS). This article evaluates and summarises four systematic reviews examining strength training for people with MS and examines if these reviews substantiate these current guidelines.

Age-dependent modulation of motor network connectivity for skill acquisition, consolidation and interlimb transfer after motor practice

OBJECTIVE

Age-related differences in neural strategies for motor learning are not fully understood. We determined the effects of age on the relationship between motor network connectivity and motor skill acquisition, consolidation, and interlimb transfer using dynamic imaging of coherent sources.

METHODS

Healthy younger (n = 24, 18-24 y) and older (n = 24, 65-87 y) adults unilaterally practiced a visuomotor task and resting-state electroencephalographic data was acquired before and after practice as well as at retention.

RESULTS

The results showed that right-hand skill acquisition and consolidation did not differ between age groups. However, age affected the ability to transfer the newly acquired motor skill to the non-practiced limb. Moreover, strengthened left- and right-primary motor cortex-related beta connectivity was negatively and positively associated with right-hand skill acquisition and left-hand skill consolidation in older adults, respectively.

CONCLUSION

Age-dependent modulations of bilateral resting-state motor network connectivity indicate age-specific strategies for the acquisition, consolidation, and interlimb transfer of novel motor tasks.

SIGNIFICANCE

The present results provide insights into the mechanisms underlying motor learning that are important for the development of interventions for patients with unilateral injuries.

Contralateral Strength Training as Preparation for Direct Strength Training in a Patient With Unilateral Foot-Drop Because of Multiple Sclerosis: A Case Report

OBJECTIVE

Direct strength training (DST) is effective in managing unilateral weakness in people with multiple sclerosis (MS). Its feasibility, however, is considerably reduced if one limb is too compromised to train. In this case, contralateral strength training (CST) of the unaffected side to induce a strength transfer to the untrained homologous muscles can help to establish a strength baseline in the weaker limb, eventually allowing direct training. Limited effects for CST, however, have been reported on patient functioning. We tested the effects on dynamometric, electromyographic, and functional outcomes of a sequential combination of CST and DST of the ankle dorsiflexors in a case of MS-related foot-drop.

METHODS

A 56-year-old man diagnosed with relapsing-remitting MS exhibited severe weakness of the right dorsiflexors impairing functional dorsiflexion. The intervention consisted of a 6-week CST of the unaffected dorsiflexors followed by 2 consecutive 6-week DST cycles targeting the weaker dorsiflexors.

RESULTS

At baseline, the participant could not dorsiflex his right ankle but could do so after CST. Maximal strength of the affected dorsiflexors increased by 80% following CST, by 31.1% following DST-1, and by a further 44.6% after DST-2. Neuromuscular recruitment was found progressively increased, with the largest changes occurring after DST-1. Improvements in mobility and walking speed were also detected, although plantar flexors' spasticity on the Modified Ashworth Scale increased from 1+ to 2.

CONCLUSION

In this case, the sequential combination of CST and DST proved a feasible approach to manage severe unilateral weakness in a patient who was not able, at least initially, to dorsiflex his weaker ankle. In this perspective, CST may prime a minimum gain in strength necessary to allow subsequent direct training.

The effect of yoga practice on muscular strength improvement in patients with multiple sclerosis

Background/Aims

Multiple sclerosis is a common condition in the central nervous system where patients experience many issues, including muscle weakness. This study offers an investigation of continuous hatha yoga exercises on patients with multiple sclerosis.

Methods

A total of 22 participants with multiple sclerosis were selected, 11 were allocated to the intervention group, and 11 to the control group. In both groups, surface electromyography and dynamometer were performed at the beginning and the end of the study. The intervention group undertook 90-minute sessions of hatha yoga training three times a week for 6 months and the control group did not do any particular exercise during this period.

Results

Dynamometer results indicated that yoga significantly improved the muscle strength of the participants with multiple sclerosis (before the intervention: 40.00 Nm ± 14.66 Nm vs 56.82 Nm ± 20.28 Nm after the intervention, P=0.037). However, there was no significant difference in muscle strength changes between the intervention and control groups (16.82 Nm ± 23.26 Nm vs -2.86 Nm ± 23.36 Nm, P=0.171). Yoga significantly increased participants muscle strength according to the surface electromyography signals (before the intervention: 39.91 V ± 8.86 V vs 54.09 v ± 8.95 V after the intervention, P=0.007). The muscle strength of the control group participants with multiple sclerosis decreased after 6 months, however it was not statistically significant (41.55 Nm ± 9.3 Nm vs 34.55 Nm ± 8.36 Nm, P=0.073). The comparison of changes showed that the surface electromyography signals in the intervention group were significantly higher than those of the control group (P=0.001).

Conclusions:

Yoga exercises, in addition to common multiple sclerosis treatment methods, can be considered as a complementary therapy to improve the physical aspects of multiple sclerosis symptoms.

How does cross-education affects muscles of paretic upper extremity in subacute stroke survivors?

INTRODUCTION

This study aimed to evaluate the benefits of adding electromuscular stimulation (EMS) to the flexors of wrist muscles on the nonparetic limb in conventional stroke training to strengthen homologous agonist and antagonist muscles on the paretic side in patients with subacute stroke.

METHODS

The EMS group patients (n = 15) received conventional therapy for 30 sessions for 6 weeks (60 min/session) with 30 min of electrical stimulation to their nonparetic forearm using wrist flexors, with 5 min of pre- and post-warm-up. The transcutaneous electrical nerve stimulation (TENS) group patients (n = 15) received the same conventional rehabilitation training with 30 min of conventional antalgic TENS at a barely sensible level to their nonparetic forearm. The Fugl-Meyer motor function assessment for upper extremity (FMA-UE), functional independence measure (FIM), Brunnstrom staging of recovery for hand, maximum and mean wrist flexion force (flexion_max and flexion_mean), and wrist extension force (extension_max and extension_mean) of paretic untrained limb were evaluated before and after the treatment.

RESULTS

EMS and TENS group patients improved similarly in terms of FMA-UE, FIM, and Brunnstrom staging for hand recovery. However, flexion_max and flexion_mean of the paretic limb increased more in the EMS group than in the TENS group. Extension_max and extension_mean on the paretic side increased in the EMS group but did not differ in the TENS group.

CONCLUSION

Cross-education via EMS may have a beneficial effect as an adjunct to conventional treatment methods. This study is retrospectively registered and is available at www.clinicaltrials.gov (ID: NCT04113369).

Adherence and drop-out in randomized controlled trials of exercise interventions in people with multiple sclerosis: A systematic review and meta-analyses

BACKGROUND

The short-term benefits of exercise in people with multiple sclerosis (MS) are well established. To sustain benefits exercise needs to continue long-term. Despite important clinical implications, no systematic reviews have synthesized evidence on adherence and drop-out in MS exercise interventions.

OBJECTIVES

1) To summarize reported adherence and drop-out data from randomized controlled trials (RCTs) of exercise interventions, and 2) identify moderators related to adherence and drop-out.

METHODS

Nine databases were electronically searched in October 2018. Included studies were RCTs of exercise interventions in adults with MS published from January 1993 to October 2018. Abstracts and full texts were independently screened and selected for inclusion by two reviewers. Methodological quality was assessed using the TESTEX rating scale.

RESULTS

Ninety three articles reporting 81 studies were included. Forty one studies (51%) reported both adherence and drop-out data during the intervention period with three (4%) also reporting follow-up data. Of the 41 studies, < 25% pre-defined adherence or described how adherence was measured. Meta-analyses of 59 interventions (41 studies) showed a pooled adherence estimate of 0.87 (95% CI 0.83 to 0.90) and 0.73 (CI 0.68-0.78) when including drop-outs. Mean age, proportion of females and intervention duration were inversely associated with adherence.

CONCLUSION

Little consensus existed on definition of adherence or determination of drop-out in MS exercise studies, with reporting generally of poor quality, if done at all. Hence it is largely unknown what can moderate adherence and whether exercise continued following an exercise intervention. Researchers should ensure clear transparent measurement and reporting of adherence and drop-out data in future trials.

Gait changes following direct versus contralateral strength training: A randomized controlled pilot study in individuals with multiple sclerosis

BACKGROUND

Contralateral strength training (CST) is increasingly investigated and employed as a non-conventional way to induce an indirect gain in strength in the weakened untrained limb. However, its effects on gait performance are more controversial.

RESEARCH QUESTION

To assess and compare the effects of contralateral (CST) and direct (DST) strength training on spatio-temporal parameters, kinematic and kinetic descriptors of gait in persons with relapsing-remitting multiple sclerosis (PwMS).

METHODS

Twenty-eight PwMS (EDSS 2.0-5.5) with inter-side difference in ankle dorsiflexors' strength ≥ 20 % and moderate gait impairment (walking speed 0.70-0.94 m/s), were randomly assigned to a CST (undergoing training of the less-affected dorsiflexors) or DST group (where the most-affected dorsiflexors were trained). Before and after a 6-week high-intensity resistance training (three 25-minute sessions/week), PwMS underwent bilateral measurements of dorsiflexors' maximal strength and assessment of gait spatio-temporal parameters, lower limb joint kinematics and kinetics.

RESULTS AND SIGNIFICANCE

Following the training period, muscle strength increased significantly in both groups (on average, CST + 29.5 %, p < 0.0005; DST + 15.7 %, p = 0.001) with no difference between the two interventions. Significant changes in gait speed (+16.5 %; p < 0.0001) and stride length (+6.0 %; p = 0.04) were detected only after DST, while no difference was detected in the CST group. Ankle moment and ROM were unaffected by the training. In PwMS with mild to moderate disability and lower limb dorsiflexors' strength asymmetry, CST was not inferior to DST in inducing significant strength gains in the untrained most-affected limb. However, only DST significantly improved gait performance and, specifically, walking speed. Even though CST did not worsen asymmetry, data suggest that contralateral approaches should not be recommended straightaway if the training goal is to improve outcomes other than strength and, specifically, walking speed.

Unilateral dorsiflexor strengthening with mirror therapy to improve motor function after stroke: A pilot randomized study

BACKGROUND

Independently, cross-education, the performance improvement of the untrained limb following unilateral training, and mirror therapy have shown to improve lower limb functioning poststroke. Mirror therapy has shown to augment the cross-education effect in healthy populations. However, this concept has not yet been explored in a clinical setting.

OBJECTIVES

This study set out to investigate the feasibility and potential efficacy of applying cross-education combined with mirror therapy compared with cross-education alone for lower limb recovery poststroke.

METHODS

Thirty-one chronic stroke participants (age 61.7 ± 13.3) completed either a unilateral strength training (ST; n = 15) or unilateral strength training with mirror-therapy (MST; n = 16) intervention. Both groups isometrically strength trained the less-affected ankle dorsiflexors three times per week for 4 weeks. Only the MST group observed the mirror reflection of the training limb. Patient eligibility, compliance, treatment reliability, and outcome measures were assessed for feasibility. Maximal voluntary contraction (MVC; peak torque, rate of torque development, and average torque), 10-m walk test, timed up and go (TUG), Modified Ashworth Scale (MAS), and the London Handicap Scale (LHS) were assessed at pretraining and posttraining.

RESULTS

Treatment and assessments were well tolerated without adverse effects. No between group differences were identified for improvement in MVC, MAS, TUG, or LHS. Only the combined treatment was associated with functional improvements with the MST group showing an increase in walking velocity.

CONCLUSION

Cross-education plus mirror therapy may have potential for improving motor function after stroke. This study demonstrates the feasibility of the combination treatment and the need for future studies with larger sample sizes to investigate the effectiveness of the treatment.

Isokinetic predictors of gait speed increase following high-intensity resistance training of the ankle dorsiflexors in people with multiple sclerosis: A pilot study

BACKGROUND

Maximal strength is a predictor of functional capacity for people with multiple sclerosis (PwMS), who frequently exhibit unilateral weakness of the ankle dorsiflexors. Aims of this study were to investigate the relationships between dorsiflexors' weakness and gait speed, the effects of high-intensity training of the affected dorsiflexors on gait performance and to identify isokinetic predictors of changes in gait speed in PwMs.

METHODS

Twenty patients aged 45 (10.3) years, illness duration 14.9 (8.5) years, median EDSS 3, underwent isokinetic dorsiflexors' strength testing at 10°/s and 45°/s angular velocities and gait analysis before and after a 6-week training of dorsiflexors. Pre-to-post differences in strength and gait parameters were analyzed by paired t-test; association between gait speed and isokinetic parameters was tested through correlation and regression analyses.

FINDINGS

Dorsiflexors' strength (peak moment at 10°/s: +14.9%, p = 0.02; at 45°/s: +21.7%, p = 0.03) and gait parameters (speed: +9.6%; p = 0.004; stride time: -5.7%; p = 0.01; cadence: +6.2%; p = 0.001; ankle power: +27.5%, p = 0.003) increased significantly. Of the thirteen isokinetic descriptors of strength, only peak moment, maximal and total work significantly correlated with gait speed increase. Regression analyses revealed high beta coefficients only for maximal work (10°/s: B = -6.528; beta = -1.825; p = 0.008; 45°/s: B = -1.466; beta = -1.364; p = 0.03).

INTERPRETATION

In PwMS, high-intensity training of weakened ankle dorsiflexors induced significant improvements in maximal strength and gait speed. The finding of maximal work as a significant predictor of training-induced changes in gait speed suggests that PwMS with reduced muscle work may benefit from strength training approaches aimed at increasing gait speed. Registration number: ClinicalTrials.gov Identifier: NCT02010398.

Perspectives on neurorehabilitation of unilateral impairments through cross-education

Background: Cross-education is being increasingly investigated as an unconventional, exercise-based intervention to manage severely lateralized weakness. To date, however, cross-education seems more important to research than clinical practice. Aim: To provide foundation and context for an informed employment of cross-education in severely or predominantly unilateral weakness or motor impairment. Method: Qualitative, narrative commentary. Results: Based on the comprehensive overview on contralateral strength training approaches to hemiplegia and unilateral weakness in stroke survivors performed by Russell and colleagues as well as on our experiences in multiple sclerosis, there is a potential for cross-education as a useful training approach to hemiplegia and unilateral weakness in stroke survivors and multiple sclerosis patients and, overall, in neurorehabilitation. However, some limitations of this non-conventional approach have to be pointed out, such as the apparent lack of translation of the performance gains of the weaker untrained side into functional improvement, particularly for the lower limb. Conclusion: Cross-education may serve as a viable option for those patients presenting severe unilateral weakness who are not able to fully exercise their weaker side directly. However, it should not be recommended straightaway if the training goal is to improve outcomes other than strength. As such, contralateral training may prove as a primer to establish a minimum level of strength that may suffice to sustain direct training, which has been proved to prompt more meaningful functional changes. Implications for rehabilitation Cross-education consists of training the stronger limb to increase strength in the untrained weaker homologous muscles. This unconventional strategy is receiving increasing attention for possible applications in neurological populations exhibiting severe unilateral impairment. For those patients who are not able to fully exercise their weaker side it may represent a viable exercise option. However, cross-education should not be recommended straightaway if the training goal is to improve outcomes other than strength.

Strength Training to Improve Gait in People with Multiple Sclerosis: A Critical Review of Exercise Parameters and Intervention Approaches

Background

There are mixed reports on the effectiveness of strength training to improve gait performance in people with multiple sclerosis (MS), yet the reasons for these inconsistent results are not clear. Therefore, a critical review was conducted to explore dosage, frequency, mode, position, and muscle targets of studies that have included strength training in people with MS.

Methods

An electronic search was conducted through July 2017. Randomized controlled trials involving people with MS were included that implemented strength training with or without other interventions and assessed 1) strength in the lower extremities and/or trunk and 2) gait speed and/or endurance. Strength and gait results were extracted, along with exercise frequency, intensity, duration, mode, position, and muscle targets.

Results

Thirteen trials met the inclusion criteria; nine used dosing consistent with recommended guidelines. Overall, six studies reported significant between-group strength improvements, and four reported within-group changes. Four studies reported significant between-group gait improvements for gait speed and/or endurance, and two reported within-group changes. Most exercises were performed on exercise machines while sitting, supine, or prone. The most common intervention target was knee extension.

Conclusions

Studies generally improved strength, yet only two studies reported potentially meaningful between-group changes in gait. Future strength intervention studies designed to improve gait might consider dosing beyond that of the minimum intensity to improve strength and explore muscles targets, positions, and modes that are task-specific to walking.

Determining the potential sites of neural adaptation to cross-education: implications for the cross-education of muscle strength

Cross-education describes the strength gain in the opposite, untrained limb following a unilateral strength training program. Since its discovery in 1894, several studies now confirm the existence of cross-education in contexts that involve voluntary dynamic contractions, eccentric contraction, electrical stimulation, whole-body vibration and, more recently, following mirror feedback training. Although many aspects of cross-education have been established, the mediating neural mechanisms remain unclear. Overall, the findings of this review show that the neural adaptations to cross-education of muscle strength most likely represent a continuum of change within the central nervous system that involves both structural and functional changes within cortical motor and non-motor regions. Such changes are likely to be the result of more subtle changes along the entire neuroaxis which include, increased corticospinal excitability, reduced cortical inhibition, reduced interhemispheric inhibition, changes in voluntary activation and new regions of cortical activation. However, there is a need to widen the breadth of research by employing several neurophysiological techniques (together) to better understand the potential mechanisms mediating cross-education. This fundamental step is required in order to better prescribe targeted and effective guidelines for the clinical practice of cross-education. There is a need to determine whether similar cortical responses also occur in clinical populations where, perhaps, the benefits of cross-education could be best observed.

Is there an overlooked “window of opportunity” in MS exercise therapy? Perspectives for early MS rehabilitation

While early medical treatment has proven effective in MS, early-phase MS rehabilitation has not gained much attention in MS research and clinical practice. Exercise therapy is one of the most promising treatment strategies in MS rehabilitation. Here, we provide a topical review investigating when exercise therapy is initiated in existing MS studies, showing that exercise is initiated at a rather late disease stage, where it predominantly serves as a symptomatic treatment. Recent findings in MS suggest that exercise may have neuroprotective and disease-modifying effects. Such findings along with the findings from medical trials that an early-stage “window of opportunity” exists leads to the proposal that early exercise therapy should be an increased focus in research and clinical practice for persons with MS. A further perspective relates to other rehabilitation interventions that are also initiated at a later disease stage, as these may also take advantage of an early-phase approach.

Pulse Width Does Not Influence the Gains Achieved With Neuromuscular Electrical Stimulation in People With Multiple Sclerosis: Double-Blind, Randomized Trial

BACKGROUND

Multiple sclerosis (MS) eventually compromises the walking ability of most individuals burdened with the disease. Treatment with neuromuscular electrical stimulation (NMES) can restore some functional abilities in persons with MS, but its effectiveness may depend on stimulus-pulse duration.

OBJECTIVE

To compare the effects of a 6-week intervention with narrow- or wide-pulse NMES on walking performance, neuromuscular function, and disability status of persons with relapsing-remitting MS.

METHODS

Individuals with MS (52.6 ± 7.4 years) were randomly assigned to either the narrow-pulse (n = 13) or wide-pulse (n = 14) group. The NMES intervention was performed on the dorsiflexor and plantar flexor muscles of both legs (10 minutes each muscle, 4 s on and 12 s off) at a tolerable level for 18 sessions across 6 weeks. Outcomes were obtained before (week 0) and after (week 7) the intervention and 4 weeks later (week 11).

RESULTS

There was no influence of stimulus-pulse duration on the outcomes ( P > .05); thus, the data were collapsed across groups. The NMES intervention improved ( P < .05) gait speed and walking endurance, dorsiflexor strength in the more-affected leg, plantar flexor strength in the less-affected leg, force control for plantar flexors in the less-affected leg, and self-reported levels of fatigue and walking limitations.

CONCLUSION

There was no influence of stimulus-pulse duration on the primary outcomes (gait speed and walking endurance). The 6-week NMES intervention applied to the lower leg muscles of persons with mild to moderate levels of disability can improve their walking performance and provide some symptom relief.

Motor unit discharge characteristics and walking performance of individuals with multiple sclerosis

Walking performance of persons with multiple sclerosis (MS) is strongly influenced by the activation signals received by lower leg muscles. We examined the associations between force steadiness and motor unit discharge characteristics of lower leg muscles during submaximal isometric contractions with tests of walking performance and disability status in individuals who self-reported walking difficulties due to MS. We expected that worse walking performance would be associated with weaker plantar flexor muscles, worse force steadiness, and slower motor unit discharge times. Twenty-three individuals with relapsing-remitting MS (56 ± 7 yr) participated in the study. Participants completed one to three evaluation sessions that involved two walking tests (25-ft walk and 6-min walk), a manual dexterity test (grooved pegboard), health-related questionnaires, and measurement of strength, force steadiness, and motor unit discharge characteristics of lower leg muscles. Multiple regression analyses were used to construct models to explain the variance in measures of walking performance. There were statistically significant differences (effect sizes: 0.21-0.60) between the three muscles in mean interspike interval (ISI) and ISI distributions during steady submaximal contractions with the plantar flexor and dorsiflexor muscles. The regression models explained 40% of the variance in 6-min walk distance and 47% of the variance in 25-ft walk time with two or three variables that included mean ISI for one of the plantar flexor muscles, dorsiflexor strength, and force steadiness. Walking speed and endurance in persons with relapsing-remitting MS were reduced in individuals with longer ISIs, weaker dorsiflexors, and worse plantar flexor force steadiness. NEW & NOTEWORTHY The walking endurance and gait speed of persons with relapsing-remitting multiple sclerosis (MS) were worse in individuals who had weaker dorsiflexor muscles and greater force fluctuations and longer times between action potentials discharged by motor units in plantar flexor muscles during steady isometric contractions. These findings indicate that the control of motor unit activity in lower leg muscles of individuals with MS is associated with their walking ability.

Cross-education of muscular strength following unilateral resistance training: a meta-analysis

PURPOSE

Cross-education (CE) of strength is a well-known phenomenon whereby exercise of one limb can induce strength gains in the contralateral untrained limb. The only available meta-analyses on CE, which date back to a decade ago, estimated a modest 7.8% increase in contralateral strength following unilateral training. However, in recent years new evidences have outlined larger contralateral gains, which deserve to be systematically evaluated. Therefore, the aim of this meta-analysis was to appraise current data on CE and determine its overall magnitude of effect.

METHODS

Five databases were searched from inception to December 2016. All randomized controlled trials focusing on unilateral resistance training were carefully checked by two reviewers who also assessed the eligibility of the identified trials and extracted data independently. The risk of bias was assessed using the Cochrane Risk-of-Bias tool.

RESULTS

Thirty-one studies entered the meta-analysis. Data from 785 subjects were pooled and subgroup analyses by body region (upper/lower limb) and type of training (isometric/concentric/eccentric/isotonic-dynamic) were performed. The pooled estimate of CE was a significant 11.9% contralateral increase (95% CI 9.1-14.8; p < 0.00001; upper limb: + 9.4%, p < 0.00001; lower limb: + 16.4%, p < 0.00001). Significant CE effects were induced by isometric (8.2%; p = 0.0003), concentric (11.3%; p < 0.00001), eccentric (17.7%; p = 0.003) and isotonic-dynamic training (15.9%; p < 0.00001), although a high risk of bias was detected across the studies.

CONCLUSIONS

Unilateral resistance training induces significant contraction type-dependent gains in the contralateral untrained limb. Methodological issues in the included studies are outlined to provide guidance for a reliable quantification of CE in future studies.