Lower extremity muscle strength across the adult lifespan in multiple sclerosis: Implications for walking and stair climbing capacity

Effects of power training in older patients with multiple sclerosis on neurodegeneration, neuromuscular function, and physical function. A study protocol for the "power training in older multiple sclerosis patients (PoTOMS) randomized control trial

Introduction

Approximately one-third of all persons with multiple sclerosis (pwMS) are older, i.e., having an age ≥60 years. Whilst ageing and MS separately elicit deteriorating effects on brain morphology, neuromuscular function, and physical function, the combination of ageing and MS may pose a particular challenge. To counteract such detrimental changes, power training (i.e., a type of resistance exercise focusing on moderate-to-high loading at maximal intended movement velocity) presents itself as a viable and highly effective solution. Power training is known to positively impact physical function, neuromuscular function, as well as brain morphology. Existing evidence is promising but limited to young and middle-aged pwMS, with the effects of power training remaining to be elucidated in older pwMS.

Methods

The presented 'Power Training in Older MS patients (PoTOMS)' trial is a national, multi-center, parallel-group, randomized controlled trial. The trial compares 24 weeks of usual care(n = 30) to 24 weeks of usual care and power training (n = 30). The primary outcome is whole brain atrophy rate. The secondary outcomes include changes in brain micro and macro structures, neuromuscular function, physical function, cognitive function, bone health, and patient-reported outcomes.

Ethics and dissemination

The presented study is approved by The Regional Ethics Committee (reference number 1-10-72-222-20) and registered at the Danish Data Protection Agency (reference number 2016-051-000001). All study findings will be published in scientific peer-reviewed journals and presented at relevant scientific conferences independent of the results. The www.clinicaltrials.gov identifier is NCT04762342.

Cardiorespiratory fitness (V̇O2peak) across the adult lifespan in persons with multiple sclerosis and matched healthy controls

OBJECTIVES

Cardiorespiratory fitness (measured as peak oxygen uptake; V̇O2peak) is a well-established health predictor in the general population and in persons with multiple sclerosis (pwMS). We aimed to investigate differences in V̇O2peak between age groups and the prevalence of V̇O2peak impairments across the adult lifespan in pwMS compared to age- and sex-matched healthy controls (HC).

DESIGN

Cross-sectional study.

METHODS

Data from 469 pwMS (EDSS range 1.0-7.0), who carried out graded cardiopulmonary exercise testing during their rehabilitation stay at the Valens clinic from 07/2010 to 10/2022, were retrospectively analyzed. Data from 21,063 HC were extracted from previously published studies containing normative reference values.

RESULTS

With advanced age (i.e., across age groups), a continuous deterioration of V̇O2peak was observed in both pwMS and HC. Within all age groups, V̇O2peak was reduced in pwMS compared to HC with deficits ranging from 29 % to 40 % for females (p < .05), and from 30 % to 41 % for males (p < .05). However, no age ∗ group interaction was observed in neither males (p = .626) nor females (p = .557). With V̇O2peak impairments defined as values below the 5th percentile of HC, a high prevalence was observed in pwMS, with values ranging from 48 % to 100 % across age groups.

CONCLUSIONS

The present data provide evidence for a parallel deterioration of V̇O2peak in pwMS and matched controls with advancing age, coinciding with a high prevalence of impairments in V̇O2peak already present in young adulthood in pwMS. Understanding the extent of impairments as well as the age trajectories of cardiorespiratory fitness in pwMS is crucial for designing optimal rehabilitative and preventive interventions.

The combined deleterious effects of multiple sclerosis and ageing on neuromuscular function

BACKGROUND

The prevalence of older (>60 years) people with multiple sclerosis (pwMS) is increasing. This introduces numerous challenges, as both MS and ageing independently contribute to the deterioration of neuromuscular function.

AIM

The aim was to compare the neuromuscular function in pwMS and healthy controls (HC) across three age groups: young, middle-aged, and old.

METHODS

Using a cross-sectional study design, the maximal muscle strength (Fmax) and rate of force development (RFD) of the knee extensors (KE) and plantar flexors (PF) were assessed using an isokinetic dynamometer. In addition, voluntary activation (VA) and resting twitch (RT) were measured using the interpolated twitch technique.

RESULTS

The Fmax, RFD, and VA of the KE were reduced in pwMS compared to HC across age groups. In pwMS, reductions were observed in PF Fmax, RFD, and RT, predominantly in the middle-aged and old age groups. Reductions increased with age in KE for both groups (except for VA) but in PF only for pwMS. The "trajectory" differed between pwMS and HC, as pwMS showed reductions from young to middle age, while HC showed reductions from middle to old age in KE.

CONCLUSION

The combined negative effects of MS and ageing on neuromuscular function were especially present in the PF but also substantial in the KE. RFD showed large deficits for pwMS compared to HC across age groups. The findings can partly be explained by a reduction in VA and RT, but further investigations of neural regulation are needed to explain large RFD deficits.

Smartwatch-derived sleep and heart rate measures complement step counts in explaining established metrics of MS severity

BACKGROUND

Passive remote monitoring of patients with MS (PwMS) with sensor-based wearable technologies promises near-continuous evaluation with high ecological validity. Step counts correlate strongly with traditional measures of MS severity. We hypothesized that remote monitoring of sleep and heart rate will yield complementary information.

METHODS

We recruited 31 PwMS and 31 age- and sex-matched healthy volunteers (HV) as part of the dreaMS feasibility study (NCT04413032). Fitbit Versa 2 smartwatches were worn for 6 weeks and provided a total of 25 features for activity, heart rate, and sleep. Features were selected based on their pairwise intercorrelation (Pearson |r| < 0.6), test-retest reliability (intraclass correlation coefficient ≥ 0.6 or median coefficient of variation < 0.2) and group comparisons between HV and PwMS with moderate disability (expanded disability status scale (EDSS) ≥ 3.5) (rank-biserial |r| ≥ 0.5). These selected features were correlated with clinical reference tests (EDSS, timed 25-foot walk (T25FW), MS-walking scale (MSWS-12)) in PwMS, and multivariate models adjusted for age, sex, and disease duration were compared.

RESULTS

We analyzed 28 PwMS (68% female, mean age 44 years, median EDSS 3.0) and 26 HV in our primary analysis. The objectively selected features discriminated well between HV and PwMS with moderate disability with rank-biserial r = 0.83 for Total number of steps, 0.51 for Deep sleep proportion, -0.51 for Median heart rate, 0.85 for Proportion very active, and 0.65 for Total number of floors. In PwMS they correlated strongly with the three clinical reference tests EDSS (strongest Spearman ρ = -0.75 for Proportion very active), T25FW (-0.75 for Total number of floors), and MSWS-12 (-0.72 for Total number of floors). Deep sleep proportion and Median heart rate complemented Total number of steps in explaining the variance of reference tests.

CONCLUSIONS

Activity, deep sleep and heart rate measures can be derived reliably from smartwatches and contain independent clinically meaningful information about MS severity, highlighting their potential for continuous passive monitoring in both clinical trials and clinical care of PwMS.

Multiple sclerosis is associated with adverse outcomes following hip and knee arthroplasty: A systematic review and meta-analysis of observational studies

BACKGROUND

The association of multiple sclerosis (MS) with joint diseases has been established. However, the impact of MS on postoperative outcomes following total joint arthroplasty (TJA) remains controversial. Therefore, a systematic review of the literature is warranted to ascertain the relationship between MS and adverse outcomes post-TJA.

METHODS

A systematic literature search of PubMed, Embase, Scopus, and the Cochrane Library from inception to 1 March 2023 was conducted to identify observational studies comparing post-TJA outcomes in MS and non-MS patients. Two investigators independently screened titles, abstracts, and full-text articles for eligibility. A random-effects model was used to calculate odds ratios (OR), mean differences (MD), and corresponding 95% confidence intervals (CI).

RESULTS

Seven retrospective cohort studies published between 2018 and 2022 met the inclusion criteria. Patients with MS had a higher risk of medical, surgical, and overall complications than patients without MS. Similarly, the MS group was more likely to experience an extended hospital stay, non-home discharge, and revision surgery compared to the control group. Joint infection and implant instability were also more common in patients with MS.

CONCLUSION

Although TJA may benefit MS patients, current evidence suggests that their postoperative outcomes may be inferior to those of non-MS patients. Thus, orthopaedic surgeons should inform MS patients of potential risks and perform preoperative optimization individually when considering elective arthroplasty.

The six spot step test is superior in detecting walking capacity impairments compared to short- and long-distance walk tests in persons with multiple sclerosis

Background

Walking capacity is important not only to persons with multiple sclerosis but also to clinical practice and research. The present study aims to compare the extent of impairments (relative to healthy controls) across three commonly used walking capacity outcomes in persons with multiple sclerosis.

Methods

In a two-hospital cross-sectional study, walking capacity was assessed using the timed-25-footwalk-test (timed 25-ft walk test; 'walking speed'), the six-minute-walk-test ('walking endurance') and the six-spot-step-test ('walking balance and coordination'). Data were compared to normative reference data in healthy controls.

Results

A total of 228 persons with multiple sclerosis (68% females) were involved in the study: age 53.7 ± 11.6 y (range 26-81 y); patient-determined-disease-steps 3 [IQR; 1; 4] (range 0-7); time since diagnosis 12.6 ± 9.9 y (range 0-49 y); MS-phenotype (relapse remitting MS, secondary progressive MS, primary progressive MS) 146/39/41; and co-morbidity n = 80 (35%). Compared to healthy controls, deficits were observed across all walking capacity outcomes (p < 0.001): timed 25-foot walk test -26 [-30; -23]%, 6 minute-walk-test -36 [-39; -32]% and six-spot-step-test -44 [-47; -40]%. Deficits differed across walking capacity outcomes (p < 0.001).

Conclusion

Altogether, persons with multiple sclerosis performed substantially worse than healthy controls across all three walking capacity outcomes. The results showed that the six-spot-step-test was superior to the timed 25-foot walk test and the 6 minute-walk-test in detecting walking capacity impairments in persons with multiple sclerosis.

Neuromuscular rate of force development discriminates fallers in ambulatory persons with multiple sclerosis - an exploratory study

BACKGROUND

Falls as well as fall-related injuries (e.g., bone fractures) are common in persons with multiple sclerosis (pwMS). Whilst some studies have identified lower extremity maximal muscle strength (Fmax) as one among several risk factors, no previous studies have investigated the association between rate of force development (RFD; ability to generate a rapid rise in muscle force) and falls in pwMS. Not only is RFD substantially compromised (and more so than Fmax) in pwMS, studies involving other neurodegenerative populations have shown that RFD - to a greater extent than Fmax - is crucial for counteracting unexpected perturbations and avoiding falling.

OBJECTIVE

To explore whether knee extensor RFD (and Fmax) can discriminate fallers from non-fallers in pwMS.

METHODS

Knee extensor neuromuscular function (comprising RFD_50ms and RFD_200ms (force developed in the interval 0-50 ms and 0-200 ms, respectively) as well as Fmax) of the weaker leg was assessed by isokinetic dynamometry. Falls were determined by 1-year patient recall, with pwMS subsequently being classified as non-fallers (0 falls), fallers (1-2 falls), or recurrent fallers (≥3 falls).

RESULTS

A total of n=53 pwMS were enrolled in the study, with n=24 classified as non-fallers (63% females, 48 years, EDSS 2.2), n=16 as fallers (88% females, 57 years, EDSS 3.3), and n=13 as recurrent fallers (46% females, 60 years, EDSS 4.2). Compared with non-fallers, neuromuscular function was reduced in both fallers (RFD₅₀ -4.42 [-7.47;-1.37] Nm^.s^-1.kg^-1, -48%; RFD₂₀₀ -1.45 [-2.98;0.07] Nm^.s^-1.kg^-1, -24%; Fmax -0.42 [-0.81;-0.03] Nm^.kg^-1, -21%) and recurrent fallers (RFD₅₀ -5.69 [-8.94;-2.43] Nm^.s^-1.kg^-1, -62%; RFD₂₀₀ -2.26 [-3.89;-0.63] Nm^.s^-1.kg^-1, -38%; Fmax -0.38 [-0.80;0.03] Nm^.kg^-1, -19%). Across all participants, associations were observed between RFD_50ms and falls (r_s = -0.46 [-0.67;-0.24], between RFD_200ms and falls (r_s = -0.34 [-0.59;-0.09]), and between Fmax and falls (r_s = -0.24 [-0.48;0.01]).

CONCLUSION

In this exploratory study, knee extensor neuromuscular function was able to discriminate fallers from non-fallers in pwMS, with RFD being superior to Fmax. Routine assessment of lower extremity neuromuscular function (RFD_50ms in particular) may be a helpful tool in identifying pwMS at future risk of falling.

Reliability of the Five Times Sit to Stand Test performed remotely by multiple sclerosis patients

INTRODUCTION

Multiple Sclerosis, known main cause of non-traumatic neurological disability in adults, leads to changes in muscle strength, especially in the lower limbs. Assessing muscle strength in these patients is thus essential and can be achieved by the Five Times Sit to Stand Test (FTSST), commonly performed in person. Due to the COVID-19 pandemic and social distancing measured adopted, Brazilian physiotherapists turned to remote monitoring and assessment, supported by Resolution n° 516/2020, which required proving the reliability of tests. Given this scenario, this study sought to evaluate the intra- and inter-rater reliability of the Five Times Sit to Stand Test performed remotely and synchronously by multiple sclerosis patients.

METHODS

A sample of 33 individuals with relapsing-remitting Multiple Sclerosis (18 women and 15 men, mean age 43.7 ± 13.4 years) were remotely and synchronously by video call. Inter-rater reliability was evaluated by analyzing FTSST execution time, in seconds, timed by two different raters on the same video call. In turn, intra-rater reliability was assessed by analyzing the execution time recorded in two different video calls made by the same rater, within a 24-28-h interval. Descriptive and inferential data analysis were performed using SPSS 20.0 software. Means and standard deviation were calculated for descriptive statistic. Intraclass correlation coefficient (ICC), with a 0.05 significance level, standard error of measurement (SEM) and minimal detectable change (MDC) were calculated for inferential analysis.

RESULTS

Data analysis showed excellent ICC values and low SEM and MDC values regarding inter-rater reliability (ICC: 0.993 (0.986-0.996); p-value: <0.001; SEM: 0.6 s; MDC: 1.6 s) and intra-rater reliability (ICC: 0.962 (0.925-0.981); p-value: <0.001; SEM: 1.4 s; MDC: 3.8 s).

CONCLUSION

Based on these values, FTSST performed remotely and synchronously by relapsing-remitting Multiple Sclerosis patients is reliable and can be used both by different raters, for assessment, or by the same rater, in pre- and post-test situations.

Physical function across the lifespan in adults with multiple sclerosis: An application of the Short Physical Performance Battery

BACKGROUND

Multiple sclerosis (MS) typically has its onset in early and middle adulthood, but the population is steadily becoming more dominated by older adults. One of the primary consequences of both MS and aging involves declines of lower extremity physical function and mobility. This cross-sectional study compared physical function status based on Short Physical Performance Battery (SPPB) summary and component scores between persons with MS and healthy controls across 6 age groups. We further examined associations between SPPB summary scores and component scores as well as associations between summary scores and measures of physical and cognitive function for identifying the strongest correlates of SPPB summary scores.

METHODS

The study involved secondary analysis of cross-sectional data from multiple studies. Ambulatory adults with MS who were relapse-free for the last 30 days were recruited, and controls were recruited based on similar criteria to adults with MS except without the diagnosis of MS or relapses. The sample of 345 persons with MS and 174 controls completed questionnaires regarding demographic and clinical information and underwent assessments of physical and cognitive function including the SPPB, 6-Minute Walk, Timed 25-Foot Walk, Symbol Digit Modalities Test, California Verbal Learning Test-Second Edition, and Brief Visuospatial Memory Test-Revised.

RESULTS

The two-way ANOVA indicated a main effect of MS status (F(5,500)=34.74, p<.01, η²=0.065), a main effect of age (F(1,500)=3.88, p<.01, η²=0.037), and no MS status by age interaction (F(5,500)=1.20, p=.31, η²=0.012) on SPPB scores. The bivariate correlation analysis indicated that summary SPPB scores were associated with component SPPB scores in the overall samples of persons with MS (r_s=0.71 to 0.83) and controls (r_s=0.42 to 0.91) as well as within most age groups of MS (r_s=0.63 to 0.91) and controls (r_s=0.34 to 1.00). The associations between SPPB scores and physical function outcomes were larger in the sample of persons with MS (r_s=-0.72 to 0.76) than controls (r_s=-0.47 to 0.48). SPPB scores were further significantly associated with scores on cognitive outcomes in persons with MS (r_s=0.31 to 0.43), whereas these associations were weaker in controls (r_s=0.09 to 0.32). Overall, the associations between SPPB scores and physical function outcomes were stronger than the associations between SPPB scores and cognitive function outcomes.

CONCLUSION

Overall, MS status and aging have additive effects on physical function, and the summary SPPB score may be driven by a specific component within each age group. SPPB scores may be driven more by mobility rather than cognition, and are consistent with cognitive-motor coupling in MS. The novelty of this study provides evidence of worsening physical function based on the application of the SPPB and its scores across the lifespan in persons with MS and controls, and this has important implications particularly given the increasing prevalence of older adults with MS.

Validity of the 30-Second Sit-to-Stand test as a measure of lower extremity function in persons with multiple sclerosis: Preliminary evidence

BACKGROUND

The 30-Second Sit-To-Stand (30SSTS) is a quick, inexpensive, safe, and widely used clinical measure of lower extremity function. To date, there is limited evidence regarding the use of 30SSTS in multiple sclerosis (MS). The purpose of this study was to examine the construct validity of the 30SSTS test in persons with MS compared with non-MS healthy controls.

METHODS

Twenty ambulatory persons with MS and twenty age- and sex-matched healthy controls completed the 30SSTS, Timed 25-Foot Walk (T25FW), Timed Up and Go (TUG), Six-Minute Walk (6MW), and Godin Leisure-Time Exercise Questionnaire (GLTEQ). Persons with MS also completed the Patient Determined Disease Steps (PDDS) and 12-item MS Walking Scale (MSWS-12).

RESULTS

Persons with MS had significantly worse performance on the TUG (mean difference [95% confidence interval] = 1.4 [0.5, 2.3] sec) and 6MW (-259.2 [-450.8, -67.6] ft), but not on the 30SSTS (-1.6 [-1.5, 4.6] reps) and T25FW (-0.59 [-0.1, 1.2] ft/sec) compared with controls. There were significant moderate-to-strong correlations between the 30SSTS with T25FW, TUG, and 6MW scores in persons with MS (r = 0.48, -0.65 and 0.61, respectively), whereas the 30SSTS was only significantly associated with 6MW scores (r = 0.43) in controls. The 30SSTS was negatively associated with MS-related walking disability assessed by the PDDS and MSWS-12 (r_s = -0.52 and -0.64, respectively), but was not significantly associated with the GLTEQ in MS and controls (r = 0.30 and 0.17, respectively).

CONCLUSION

This study provides initial support for the construct validity of the 30SSTS as a measure of lower extremity function in persons with MS. Our findings warrant the inclusion of the 30SSTS as a feasible and valid measure of physical function in clinical research and practice involving persons with MS.

Examination of the Impact of Strength and Velocity of the Knee and Ankle on Gait Speed in Community-Dwelling Older Adults

The muscle strength of the knee extension and plantarflexion plays a crucial role in determining gait speed. Recent studies have shown that no-load angular velocity of the lower limb joints is essential for determining gait speed. However, no reports have compared the extent to which lower limb functions, such as knee extension strength, knee extension velocity, plantarflexion strength, and plantarflexion velocity, impact gait speed in a single study. Therefore, this study aimed to examine the relative importance of maximum strength and no-load angular velocity on gait speed. Overall, 164 community-dwelling older adults (72.9 ± 5.0 years) participated in this study. We measured the gait speed and lower limb function (the strength and velocity of knee extension and plantarflexion). Strength was measured with a hand-held dynamometer, and velocity with a gyroscope. A multiple regression analysis was performed with gait speed as the dependent variable and age, sex, and lower-limb function as independent variables. Plantarflexion velocity (β = 0.25) and plantarflexion strength (β = 0.21) were noted to be significant predictors of gait speed. These findings indicate that no-load plantarflexion velocity is more important than the strength of plantarflexion and knee extensions as a determinant of gait speed, suggesting that improvement in plantarflexion velocity may increase gait speed.

Objectively assessed physiological, physical, and cognitive function along with patient-reported outcomes during the first 2 years of Alemtuzumab treatment in multiple sclerosis: a prospective observational study

INTRODUCTION

In persons with multiple sclerosis (pwMS), little evidence exist on the effects of Alemtuzumab on physiological, physical, and cognitive function along with patient-reported outcomes, despite these domains are being rated as highly important. Therefore, our purpose was to perform a prospective observational study to examine these outlined outcomes during the first two years of Alemtuzumab treatment in pwMS.

METHODS

In n = 17 relapsing-remitting pwMS, physiological function [body composition; bone mineral content; muscle strength; aerobic capacity], physical function [6-min walk test (6MWT, primary outcome); timed 25 ft walk test (T25FWT); six spot step test (SSST); 9-step stair ascend (9SSA); timed up and go test (TUG); 5 × sit to stand test (5STS)], cognitive function [selective reminding test (SRT); symbol digit modalities test (SDMT)], and patient-reported outcomes [multiple sclerosis impact scale-29 (MSIS29); 12-item multiple sclerosis walking scale (MSWS12); modified fatigue impact scale (MFIS); hospital anxiety and depression scale (HADS)] were assessed prior to Alemtuzumab treatment initiation as well as 3, 6, 12, and 24 months into the treatment.

RESULTS

Improvements were observed at 24-month follow-up in T25FWT (+ 8%), SSST (+ 10%), SDMT (+ 5.2 points, 53% improved more than the clinical cut-off score) and SRT, whereas the primary outcome 6MWT, and all other remaining outcomes, remained stable throughout the Alemtuzumab treatment period.

CONCLUSION

The present findings suggest that Alemtuzumab treatment in relapsing-remitting pwMS can improve certain domains of physical function (short distance walking) and cognitive function (processing speed, memory), and furthermore stabilize physiological and physical function along with patient-reported outcomes.

TRIAL REGISTRATION

Registered at clinicaltrials.gov: NCT03806387.

Is Aerobic or Resistance Training the Most Effective Exercise Modality for Improving Lower Extremity Physical Function and Perceived Fatigue in People With Multiple Sclerosis? A Systematic Review and Meta-analysis

OBJECTIVE

The purpose of this systematic review was to investigate whether aerobic training (AT) or resistance training (RT) is most effective in terms of improving lower limb physical function and perceived fatigue in persons with multiple sclerosis (PwMS).

DATA SOURCES

Nine databases (MEDLINE, EMBASE, Cumulative Index to Nursing and Allied Health, Allied and Complementary Medicine Database, Physiotherapy Evidence Database, SPORTDiscus, PsycINFO, Web of Science, and Scopus) were electronically searched in April 2020.

STUDY SELECTION

Included studies were randomized controlled trials (RCTs) involving PwMS attending 1 of 2 exercise interventions: AT or RT. Studies had to include at least 1 objective or self-reported outcome of lower extremity physical function and/or perceived fatigue.

DATA EXTRACTION

Data were extracted using a customized spreadsheet, which included detailed information on patient characteristics, interventions, and outcomes. The methodological quality of the included studies was independently assessed by 2 reviewers using the Tool for Assessment of Study Quality for Reporting on Exercise rating scale.

DATA SYNTHESIS

Twenty-seven articles reporting data from 22 RCTS (AT=14, RT=8) including 966 PwMS. The 2 modalities were found to be equally effective in terms of improving short walk test (AT: effect size [ES]=0.33 [95% confidence interval (CI), -1.49 to 2.06]; RT: ES=0.27 [95% CI, 0.07-0.47]) and long walk test performance (AT: ES=0.37 [95% CI, -0.04 to 0.78]; RT: ES=0.36 [95% CI, -0.35 to 1.08]), as well as in reducing perceived fatigue (AT: ES=-0.61 [95% CI, -1.10 to -0.11]; RT: ES=-0.41 [95% CI, -0.80 to -0.02]). Findings on other functional mobility tests along with self-reported walking performance were sparse and inconclusive.

CONCLUSIONS

AT and RT appear equally highly effective in terms of improving lower extremity physical function and perceived fatigue in PwMS. Clinicians can thus use either modality to target impairments in these outcomes. In a future perspective, head-to-head exercise modality studies are warranted. Future MS exercise studies are further encouraged to adapt a consensus "core battery" of physical function tests to facilitate a detailed comparison of results across modalities.

Impaired central drive to plantarflexors and minimal ankle proprioceptive deficit in people with multiple sclerosis

BACKGROUND

A common and disruptive symptom of multiple sclerosis is difficulty in walking. Deficits in ankle proprioception and in plantarflexor muscle function may contribute to these mobility issues. In this study, ankle proprioceptive ability and plantarflexor performance of people with multiple sclerosis (PwMS) were compared to healthy controls to determine whether multiple sclerosis causes impairments in these systems.

METHODS

PwMS (n = 30, median EDSS 4.0, IQR 2) were compared to age- and sex-matched healthy controls (n = 30) across tests of ankle proprioception and plantarflexor muscle performance. Proprioceptive tests: detection of passive movement, reaction time and ankle joint position sense. Plantarflexor performance: strength, fatigue, recovery and voluntary activation (level of neural drive) of the plantarflexor muscles, assessed through brief and sustained fatiguing (2 min) isometric maximal voluntary contractions with nerve stimulation to evoke superimposed and resting muscle twitches.

RESULTS

PwMS had unimpaired movement detection and joint position sense but had a slower reaction time to respond with plantarflexion to an imposed ankle movement (between group difference = 0.11 [95% CI; 0.05 to 0.17] s). During brief, maximal contractions PwMS produced lower torque (difference = -25.1 [-42.0 to -8.2] Nm) with reduced voluntary activation (difference = -14.6 [-25.1 to -4.1]%) but no impairment of the muscle itself (resting twitch torque difference = 0.3 [-2.8 to 2.2] Nm). At the end of the fatiguing contraction, neural drive decreased for PwMS (-19.5 [-27.1 to -11.9]%, p <0.0001) but not for controls (-2.5 [-6.9 to 1.8]%, p = 0.242). Fatigue did not affect the resting twitch size for controls (-1.3 [-2.7 to -0.03] Nm, p = 0.134) or PwMS (-0.1 [-1.1 to 1.0] Nm, p = 0.90).

CONCLUSIONS

PwMS showed no deficit in their ability to sense ankle position or imposed movements but were slow when a motor response was required. Their plantarflexor muscles produced similar torque with electrical stimulation but voluntary strength was impaired.  Both groups experienced overall fatigue following the 2-minute maximal voluntary contraction but PwMS also had significantly reduced neural drive indicating central fatigue. PwMS showed mainly central deficits in motor output at the ankle with little impairment of proprioceptive acuity.