Quantitative assessment of motor fatigue and strength in MS

The measurement of fatigability severity in individuals with multiple sclerosis and healthy controls

BACKGROUND

Multiple Sclerosis (MS) is a chronic disease that substantially diminishes one's ability to undertake daily living activities. Fatigue has been reported by at least 80 % of persons with MS (PwMS). Yet, little is known concerning the quantification of fatigability using prolonged walking tests.

OBJECTIVES

To compare fatigability severity measures using the 10-minute walk test for PwMS against age- and gender-matched healthy controls (HCs).

METHODS

Participants included 53 ambulatory PwMS and 49 HCs. Perceived fatigability was measured by dividing a participant's change in self-reported tiredness by the number of meters walked. Performance fatigability was calculated by dividing the change in walking speed (at 2.5 and 10 min) by the total distance walked in meters.

RESULTS

There was a significant difference in perceived fatigability between PwMS and HCs (mean difference: 2.73 ± 0.83; p = 0.001) and in performance fatigability (mean difference: 0.24 ± 0.11; p = 0.01). Moreover, there were significant differences in speed and distance at all time points (p ≤ 0.05) between PwMS and HCs.

CONCLUSIONS

PwMS have significant walking deficits as reflected by greater fatigability in both perceived and performance measures. These methods can enhance therapeutic strategies that improve the walking performances of PwMS.

Management of multiple sclerosis fatigue in the digital age: from assessment to treatment

Fatigue is one of the most disabling symptoms of Multiple Sclerosis (MS), affecting more than 80% of patients over the disease course. Nevertheless, it has a multi-faceted and complex nature, making its diagnosis, evaluation, and treatment extremely challenging in clinical practice. In the last years, digital supporting tools have emerged to support the care of people with MS. These include not only smartphone or table-based apps, but also wearable devices or novel techniques such as virtual reality. Furthermore, an additional effective and cost-efficient tool for the therapeutic management of people with fatigue is becoming increasingly available. Virtual reality and e-Health are viable and modern tools to both assess and treat fatigue, with a variety of applications and adaptability to patient needs and disability levels. Most importantly, they can be employed in the patient's home setting and can not only bridge clinic visits but also be complementary to the monitoring and treatment means for those MS patients who live far away from healthcare structures. In this narrative review, we discuss the current knowledge and future perspectives in the digital management of fatigue in MS. These may also serve as sources for research of novel digital biomarkers in the identification of disease activity and progression.

The rate of force relaxation scaling factor is highly sensitive to detect upper and lower extremity motor deficiencies in mildly affected people with multiple sclerosis

BACKGROUND

The motor symptoms affecting upper and lower extremity functioning in people with multiple sclerosis (PwMS) are considered the cardinal symptoms of multiple sclerosis. There is still a need for outcome measures that can sensitively evaluate these symptoms. We aimed to investigate the sensitivity of the isometric outcomes (maximum force; Fmax, maximum rate of force development; RFDmax, rate of force development scaling factor; RFD-SF, and rate of force relaxation scaling factor; RFR-SF) and standard clinical tests (9-hole peg test; 9HPT and timed 25-feet walk test; T25FW) in detecting the upper and lower extremity motor deficiencies in PwMS and also in a subgroup of mildly affected PwMS whose performance in standard clinical tests were similar to controls.

METHODS

Twenty-nine PwMS (age: 47.9 (8.6) years, relapsing-remitting type, expanded disability status scale: 2.5 (1.5)) and their age- and gender-matched controls completed an identical testing protocol in the upper (grip force muscles) and lower (knee extensors) extremities. For each extremity, we assessed Fmax, RFDmax, RFD-SF, and RFR-SF. Additionally, participants completed standard clinical tests for the evaluation of upper- (9HPT) and lower-extremity (T25FW) function. Comparisons were made between controls and PwMS 1) using all study participants and 2) including only mildly affected PwMS whose performance in standard functional tests was comparable to controls. Independent sample t-tests were utilized to compare groups, with a p-value set at 0.01 to correct for multiple comparisons. P-values and effect sizes were used to evaluate the sensitivity of the outcome measures in detecting group differences.

RESULTS

Our results indicate that most isometric outcomes and standard functional tests were sensitive in detecting motor deficiencies in both upper and lower extremities between groups (p<0.001). Among participants, 16 PwMS in 9HPT and 11 PwMS in T25FW demonstrated performance similar to that of the control group (9HPT: 18.85 (2.20) s vs 17.81 (2.19) s; p=0.19) and (T25FW: 3.60 (0.42) s vs 3.58 (0.29) s; p=0.92). The results of the comparisons between mildly affected PwMS and their controls indicate that RFR-SF is the only sensitive isometric outcome to detect differences between groups in the upper (-8.24 (0.76) 1/s vs -8.93 (0.6) 1/s; p=0.008) and lower extremity (-5.86 (1.13) 1/s vs -7.71 (1.11) 1/s; p<0.001).

CONCLUSION

The rate of force relaxation scaling factor, which assesses the ability to rapidly relax muscle forces after quick contractions, demonstrates high sensitivity in detecting motor deficiencies in PwMS, even when the current standard clinical outcomes fail to detect these differences. Our findings emphasize the importance of future randomized controlled trials focusing on rehabilitative and therapeutic interventions that specifically target muscle force relaxation to enhance motor functioning in PwMS.

Neuromuscular fatigue in autoimmune myasthenia gravis: A cross-sectional study

OBJECTIVES

To investigate the presence of increased neuromuscular fatigue (NMF) in individuals with myasthenia gravis (IwMG), compared to healthy controls. A secondary aim was to assess associations between NMF, strength and perceived health-related quality of life (HRQoL) and symptom severity in IwMG.

METHODS

In this cross-sectional study, we assessed NMF using classical myoelectrical indicators (root mean square: RMS, mean power frequency: MPF) obtained from surface electromyography (sEMG) during a sustained submaximal isometric contraction of the right Biceps Brachii and the right Vastus Lateralis and by evaluating the post-effort decline in peak torque following a fatiguing task consisting of a 40-second sustained isometric contraction. Relationships with MG-specific clinical scores (Myasthenia Muscle Score for symptom severity, MGQOL-15-F for HRQoL) were investigated.

RESULTS

Forty-one females with MG were compared to 18 control females of similar age. IwMG demonstrated reduced strength in both muscle groups, compared to control subjects. In both populations and both limbs, NMF was demonstrated by an increase in RMS and a decrease in MPF. However, IwMG did not demonstrate greater NMF based on these myoelectrical indicators nor based on post-effort peak torque decline.

DISCUSSION

Despite a decrease in baseline strength, IwMG did not display greater NMF in this specific experimental paradigm. This cohort consisted of individuals with mild-to-moderately severe MG which was well-controlled and stable. Further studies are warranted to identify simple and reliable methods to measure NMF in MG and to understand the relationship between NMF and perceived fatigue in activities of daily living for IwMG.

Factors contributing to falls in people with multiple sclerosis: The exploration of the moderation and mediation effects

BACKGROUND

The prevalence of multiple sclerosis (MS) has significantly increased in recent decades. People with MS have a high risk of falling; these falls may lead to serious injuries, affecting their quality of life PURPOSE: The aim of this study is to assess the factors affecting falls in people with MS and map out the most significant ones. This study also aims to determine whether fatigue has a moderation effect and balance has a mediation effect on falls in people with MS METHODS: In total, 103 people with MS with a mean age of 32.09 ± 7.17 were enrolled. All subjects were assessed for multiple variables including balance using the Berg Balance Scale (BBS), speed of gait using the Timed Up and Go (TUG) test, fear of falling using the Falls Efficacy Scale-International (FES-I), level of fatigue using the Modified Fatigue Impact Scale (MFIS), and lower limb muscle strength using a handheld digital dynamometer RESULTS: Simple binary logistic regression analysis showed significant results for BBS (OR: 10.88; 95% CI: 4.24-27.96; p < 0.0001), TUG (OR: 1.18; 95% CI: 1.09-1.28; p < 0.0001), FES-I (OR: 1.06; 95% CI: 1.02-1.10; p = 0.001), and MFIS (OR: 1.04; 95% CI: 1.02-1.07; p < 0.0001) as factors affecting falls. According to multivariate analysis, balance (OR: 3.924; 95% CI: 1.307-11.780, p = 0.015), speed of gait (OR: 1.122; 95% CI: 1.023-1.231; p = 0.015), and fatigue (OR: 1.029; 95% CI: 1.002-1.058; p = 0.038) were the strongest predicting factors of falls. Hayes's PROCESS analysis showed that fatigue had a significant moderation effect on the relationship between gait speed and falls (MFIS; β; 0.10; p < 0.0001; 95% CI: 0.07-0.14) and balance had a mediation effect on the relationship between gait speed and falls (BBS; indirect effect; 0.08; 95% CI: 0.02-0.13) CONCLUSIONS: People with MS with impaired balance, slower gait speeds, higher levels of fatigue, and a fear of falling were at a high risk of falling. The relationship between gait speed and falls can be mediated by impaired balance and moderated by the level of fatigue. Our data suggest that targeting balance and fatigue while developing rehabilitation interventions could decrease the incidence of falls among people with MS.

Exploring the impact of exercise and essential amino acid plus cholecalciferol supplementation on physical fitness and body composition in multiple sclerosis: A case study

Key Clinical Message

In MS patients, especially those frail or malnourished, combining home-based exercise twice weekly with essential amino acids and vitamin D may improve body composition, strength, and physical performance, enabling long-term functional improvements.

Abstract

Multiple sclerosis (MS) is associated with reduced bone and muscle strength and function. We aimed to investigate the effectiveness of a 24-week intervention in a 57-year-old frail female with MS. The participant completed a 2×/week exercise intervention and ingested 2×/day a supplement containing 7.5 g essential amino acids and 500 IU cholecalciferol. Body composition, 6-m gait speed (GS), handgrip strength (HGS), 30-sec arm-curl test (30ACT), 6-min walking test (6MWT), 30-sec chair-stand test (30CST), and plasma concentrations of 25-hydroxyvitamin D₃ [25(OH)D₃], insulin-like growth factor 1 (IGF-1), and amino acids were assessed at baseline, and at Weeks 12 and 24. Plasma 25(OH)D₃ increased from 23.2 to 41.3 ng/mL and IGF-1 from 131.6 to 140.7 ng/mL from baseline to post-intervention. BMI, total lean tissue mass (LTM), fat mass, bone mineral content, and the sum of 17 amino acids increased by 3.8, 1.0, 3.5, 0.2, and 19%, respectively, at Week 24. There were clinically significant increases in regional LTM (6.9% arms and 6.3% legs) and large increases in GS (67.3%), dominant HGS (31.5%), non-dominant HGS (11.8%), dominant 30ACT (100%), non-dominant 30ACT (116.7%), 6MWT (125.6%), and 30CST (44.4%). The current intervention was effective in improving components of physical fitness and body composition in a female with MS.

Use of a physiological profile to document upper limb motor impairment in ageing and in neurological conditions

Profiling performance in the physiological domains underpinning upper limb function (such as strength, sensation, coordination) provides insight into an individual's specific impairments. This compliments the traditional medical 'diagnosis' model that is currently used in contemporary medicine. From an initial battery of 13 tests in which data were collected across the adult lifespan (n = 367, 20-95 years) and in those with neurological conditions (specifically, multiple sclerosis (n = 40), Parkinson's disease (n = 34), and stroke (n = 50)), six tests were selected to comprise a core upper limb physiological profile assessment (PPA). This comprised measures of handgrip strength, simple reaction time, finger dexterity, tactile sensation, bimanual coordination, and a functional task. Individual performance in each of these tests can be compared to a reference population score (devised from our database of healthy individuals aged under 60 years), informing the researcher or clinician how to best direct an intervention or treatment for the individual based on their specific impairment(s). Lastly, a composite score calculated from the average performance across the six tests provides a broad overview of an individual's overall upper limb function. Collectively, the upper limb PPA highlights specific impairments that are prevalent within distinct pathologies and reveals the magnitude of upper limb motor impairment specific to each condition.

Objective measurement of oral function in adults with spinal muscular atrophy

BACKGROUND

Impairment of bulbar function in adult individuals with spinal muscular atrophy (SMA) usually is not assessed by established motor scores. Measurements of oral function including quantitative muscle and endurance tests are able to detect subtle changes. The aim of this study was to systematically evaluate the measurement of maximum bite force and endurance, maximum tongue pressure and endurance, as well as maximum mouth opening in adult individuals with SMA types 2 and 3.

METHODS

Data from oral function tests in 43 individuals were analyzed. Differences in oral function between individuals with different SMA types and numbers of SMN2 copies were tested. Spearman´s rho correlations among oral function measures themselves as well as with established clinical outcome scales were analyzed.

RESULTS

The absolute maximum measures of oral function (maximum bite force, maximum tongue pressure, maximum mouth opening) were able to discriminate between individuals with different SMA types, individuals with a different number of SMN2 copies and with different walking abilities. The pairwise correlations of the absolute maximum measures of oral function were fair to moderate in size; the same was true for their correlations with the established motor scores. All correlations assessing endurance measures of oral function were weaker and statistically insignificant.

CONCLUSIONS

Among the oral function tests maximum tongue pressure and maximum mouth opening are particulary promising as clinical and sensitive outcome measures for clinical trials. Oral function tests may supplement existing motor scores, in particular concerning specific questions about bulbar function or in severely affected non-ambulatory individuals where mild (treatment-related) changes would otherwise remain undetected. Trial registration DRKS, DRKS00015842. Registered 30 July 2019, https://drks.de/search/de/trial/DRKS00015842.

Children With Cerebral Palsy Show Higher Static-But Not Higher Dynamic-Motor Fatigability in Grip and Pinch Tasks Than Children With Typical Development Do

OBJECTIVE

The purpose of this study was to investigate differences in static and dynamic motor fatigability during grip and pinch tasks between children with unilateral spastic cerebral palsy (USCP) and children with typical development (TD) and between preferred and nonpreferred hands.

METHODS

Fifty-three children with USCP and 53 age-matched children with TD (mean = 11 years 1 month; SD = 3 years 8 months) participated in 30-second maximum exertion sustained and repeated grip and pinch tasks. For sustained tasks, the Static Fatigue Index and the ratio of mean force between the first and last thirds of the curve were calculated. For repeated tasks, the ratio of mean force and the ratio of numbers of peaks between the first and last thirds of the curve were calculated.

RESULTS

Higher Static Fatigue Index scores for grip and pinch were found with USCP in both hands and between hands in both groups. Dynamic motor fatigability showed inconsistent results, with higher levels of fatigability in children with TD than in children with USCP for grip in the ratio of mean force between the first and last thirds of the curve in nonpreferred hands and in the ratio of number of peaks between the first and last thirds of the curve in preferred hands.

CONCLUSION

Higher motor fatigability in children with USCP than in children with TD was found for static but not dynamic grip and pinch. Underlying mechanisms may play different roles in static and dynamic motor fatigability.

IMPACT

These results highlight that static motor fatigability in grip and pinch tasks should be part of a comprehensive upper limb assessment and that this could be the target of individualized interventions.

How is neuromuscular fatigability affected by perceived fatigue and disability in people with multiple sclerosis?

Whereas fatigue is recognized to be the main complaint of patients with multiple sclerosis (PwMS), its etiology, and particularly the role of resistance to fatigability and its interplay with disability level, remains unclear. The purposes of this review were to (i) clarify the relationship between fatigue/disability and neuromuscular performance in PwMS and (ii) review the corticospinal and muscular mechanisms of voluntary muscle contraction that are altered by multiple sclerosis, and how they may be influenced by disability level or fatigue. Neuromuscular function at rest and during exercise are more susceptible to impairement, due to deficits in voluntary activation, when the disability is greater. Fatigue level is related to resistance to fatigability but not to neuromuscular function at rest. Neurophysiological parameters related to signal transmission such as central motor conduction time, motor evoked potentials amplitude and latency are affected by disability and fatigue levels but their relative role in the impaired production of torque remain unclear. Nonetheless, cortical reorganization represents the most likely explanation for the heightened fatigability during exercise for highly fatigued and/or disabled PwMS. Further research is needed to decipher how the fatigue and disability could influence fatigability for an ecological task, especially at the corticospinal level.

Test-Retest Reliability of a Static and Dynamic Motor Fatigability Protocol Using Grip and Pinch Strength in Children With Cerebral Palsy

OBJECTIVE

The purpose of this study was to investigate the test-retest reliability, measurement error, and interpretability of new motor fatigability outcomes of grip and pinch strength for children with unilateral cerebral palsy (UCP).

METHODS

Motor fatigability during grip and pinch strength was measured twice (within 48 hours) in both hands of 50 children (mean age = 11 years 2 months; 14, 31, and 5 children with Manual Ability Classification System levels I, II, and III, respectively) using a 30-second static and dynamic maximum exertion protocol. For static motor fatigability, the Static Fatigue Index (SFI) and mean force (Fmean) in the first (Fmean1) and last (Fmean3) 10 seconds were calculated. For dynamic motor fatigability, Fmean1, Fmean3, and the number of peaks in the first and last 10 seconds were calculated.

RESULTS

For static motor fatigability, the intraclass correlation coefficients (ICCs) were moderate to high for Fmean1 and Fmean3 (0.56-0.88), and the SFI showed low to moderate reliability (ICC = 0.32-0.72). For dynamic motor fatigability, the ICCs were moderate to high for all outcomes (0.54-0.91). The standard error of measurement agreement and the smallest detectable difference agreement were large in all outcomes, except for the SFI in static motor fatigability. Details per age group are provided. In general, younger children (6-11 years old) showed lower reliability than older children (12-18 years old).

CONCLUSION

Most outcome measures for static and dynamic motor fatigability of grip and pinch strength show moderate to high reliability in children with UCP, indicating that these tests can be used reliably to investigate the presence of motor fatigability in UCP, especially in older children. Standard error of measurement agreement and smallest detectable difference agreement indicated that these outcome measures should be interpreted with caution when evaluating change.

IMPACT

Most of the proposed outcome measures for static and dynamic motor fatigability of grip and pinch are reliable in children with UCP and can be used for discriminative purposes.

Development of a Novel Accelerometry-Based Performance Fatigability Measure for Older Adults

INTRODUCTION

Efforts to study performance fatigability have been limited because of measurement constrains. Accelerometry and advanced statistical methods may enable us to quantify performance fatigability more granularly via objective detection of performance decline. Thus, we developed the Pittsburgh Performance Fatigability Index (PPFI) using triaxial raw accelerations from wrist-worn accelerometer from two in-laboratory 400-m walks.

METHODS

Sixty-three older adults from our cross-sectional study (mean age, 78 yr; 56% women; 88% White) completed fast-paced ( n = 59) and/or usual-paced 400-m walks ( n = 56) with valid accelerometer data. Participants wore ActiGraph GT3X+ accelerometers (The ActiGraph LLC, Pensacola, FL) on nondominant wrist during the walking task. Triaxial raw accelerations from accelerometers were used to compute PPFI, which quantifies percentage of area under the observed gait cadence-versus-time trajectory during a 400-m walk to a hypothetical area that would be produced if the participant sustained maximal cadence throughout the entire walk.

RESULTS

Higher PPFI scores (higher score = greater fatigability) correlated with worse physical function, slower chair stands speed and gait speed, worse cardiorespiratory fitness and mobility, and lower leg peak power (| ρ | = 0.36-0.61 from fast-paced and | ρ | = 0.28-0.67 from usual-paced walks, all P < 0.05). PPFI scores from both walks remained associated with chair stands speed, gait speed, fitness, and mobility, after adjustment for sex, age, race, weight, height, and smoking status; PPFI scores from the fast-paced walk were associated with leg peak power.

CONCLUSIONS

Our findings revealed that the objective PPFI is a sensitive measure of performance fatigability for older adults and can serve as a risk assessment tool or outcome measure in future studies and clinical practice.

Instrumented Assessment of Motor Performance Fatigability During the 6-Min Walk Test in Mildly Affected People With Multiple Sclerosis

There are conflicting results regarding the changes in spatio-temporal gait parameters during the 6-min walk test (6MWT) as indicators of gait-related motor performance fatigability (PF) in people with Multiple Sclerosis (pwMS). To further analyze if gait-related motor PF can be quantified using instrumented gait analysis during the 6MWT, we investigated: (i) whether gait parameters recorded during the first or second minute were more stable and thus the better baseline to assess motor PF and (ii) if the minimum toe clearance (MTC) together with “classical” spatio-temporal gait parameters can be used to quantify motor PF in pwMS. Nineteen mildly affected pwMS [12 women/7 men; 47.8 ± 9.0 years; the Expanded Disability Status Scale (EDSS): 2.7 ± 1.0] and 24 healthy controls (HC; 15 women/9 men; 48.8 ± 7.6 years) completed the 6MWT equipped with inertial measurement units. Data were analyzed using the attractor method to compare the stability of gait parameters and, besides “classical” spatio-temporal gait parameters, the MTC was calculated as a potential new marker for motor PF in pwMS as this was shown in healthy older adults. It was found that (i) gait parameters were more stable in the second than in the first minute and (ii) gait-related motor PF could not be detected based on spatio-temporal gait parameters, including the MTC. Descriptive analysis indicated a decrease in MTC variability, which is assumed to be indicative for motor PF, toward the end of the 6MWT in some pwMS. Future studies should investigate gait parameters for the assessment of motor PF in pwMS recorded during more intense and/or longer walking protocols, taking the level of disability into account. Furthermore, using gait parameters recorded in the first minute of the 6MWT as a baseline for the assessment of motor PF should be avoided.

Cognitive fatigability assessment test (cFAST): Development of a new instrument to assess cognitive fatigability and pilot study on its association to perceived fatigue in multiple sclerosis

Background

Fatigue is a common symptom of many diseases, including multiple sclerosis. It manifests as a cognitive or physical condition. Fatigue is poorly understood, and effective therapies are missing. Furthermore, there is a lack of methods to measure fatigue objectively. Fatigability, the measurable decline in performance during a task, has been suggested as a complementary method to quantify fatigue.

Objective

To develop a new and objective measurement of cognitive fatigability and investigate its association with perceived fatigue.

Methods

We introduced the cognitive fatigability assessment test (cFAST), a novel smartphone-based test to quantify cognitive fatigability. Forty-two people with multiple sclerosis (23 fatigued and 19 non-fatigued, defined by the Fatigue Scale for Motor and Cognitive Functions) took part in our validation study. Patients completed cFAST twice. We used t-tests, Monte Carlo sampling, and area under the receiver operating characteristic curves to evaluate our approach using two sets of proposed metrics.

Results

When classifying fatigue, our fatigability metric Δresponse time has a mean area under the receiver operating characteristic curve of 0.74 (95% CI 0.64–0.84), making it the best performing metric for this task. Furthermore, Δresponse time shows a statistically significant difference between the fatigued and non-fatigued groups (t = 2.27, P = .03). Particularly, cognitively-fatigued patients decline in performance, while non-fatigued patients do not.

Conclusions

We introduce cFAST, a new instrument to quantify cognitive fatigability. Our pilot study provides evidence that cognitive fatigability assessment test produces a quantifiable drop in cognitive performance in a short period. Furthermore, our results indicate that cFAST may have the potential to serve as a surrogate for subjective cognitive fatigue. cFAST is significantly shorter than the existing fatigability assessments and does not require specialized equipment. Thus, it could enable frequent and remote monitoring, which could substantially aid clinicians in better understanding and treating fatigue.

Original articleQuantifying upper-limb motor impairment in people with multiple sclerosis: a physiological profiling approach

BACKGROUND

. Upper-limb sensory and motor impairments are common in people with multiple sclerosis (MS), yet the current gold standard criteria for documenting functional impairment largely focuses on mobility, balance and postural stability.

OBJECTIVE

. We aimed to determine the validity of the upper-limb Physiological Profile Assessment (PPA) in people with MS by investigating whether the included domains of muscle strength, dexterity, arm stability, position sense, skin sensation and bimanual coordination 1) are sensitive in differentiating people with MS from healthy controls and 2) correlate with a validated measure of upper-limb function and a scale for quantifying disability in MS.

METHODS

. In a cross-sectional study, 40 participants with MS and 80 healthy controls completed all 13 of the upper-limb PPA tests within a single session.

RESULTS

. People with MS were impaired across all physiological domains tested. Performance in 4 of the 13 tests was correlated with a validated measure of self-reported upper-limb function (Pearson's r or Spearman's rho -0.333-0.441), whereas 3 tests were associated with the degree of MS-specific disability (Spearman's rho -0.318; 0.456).

CONCLUSIONS

. The upper-limb PPA offers a valid and clinically suitable assessment of upper-limb function in people with MS. Clinicians should prioritise assessments of motor speed, fine motor control and functional tasks in their assessment of upper-limb function in people with MS because these domains are the most commonly and significantly impaired.

Exercise and Sports Science Australia (ESSA) position statement on exercise for people with mild to moderate multiple sclerosis

OBJECTIVES

Multiple sclerosis (MS), the most common chronic and progressive neurological condition of the central nervous system, affects 26,000 Australian adults. Exercise training has beneficial effects on MS-related impairments including reduced muscular strength, poor aerobic capacity and impaired mobility, and in consequence can improve quality of life. This Position Statement provides evidence-based recommendations for exercise prescription and delivery of exercise training for people with MS with mild to moderate disability.

DESIGN AND METHODS

Synthesis of published works within the field of exercise training in MS.

RESULTS

Exercise provides many benefits to people with MS. There is strong evidence that resistance and aerobic training, performed 2 to 3 times per week at a moderate intensity, are safe and can improve muscle strength, cardiorespiratory fitness, balance, fatigue, functional capacity, mobility and quality of life in people with MS with mild to moderate disability (Expanded Disease Severity Scale (EDSS) ≤ 6.5). However, the evidence for those with severe disability (EDSS >6.5) is less clear. The effects of exercise on MS pathogenesis, central nervous structures and other outcomes such as depression and cognitive impairment, have not been adequately investigated. Effective exercise interventions to improve balance, joint contractures and reduce falls in people with MS are also urgently needed as well as investigations of long-term (≥1 year) effects of exercise training.

CONCLUSIONS

Resistance and aerobic training exercises are effective to alleviate some characteristic signs and symptoms in MS and should be supplemented by balance exercise to prevent falls. Exercise training programs should be prescribed and delivered by qualified exercise professionals. It is important to recognise and accommodate exercise-associated complications such as fatigue and heat sensitivity.

Muscle architecture and its relationship with lower extremity muscle strength in multiple sclerosis

This study was planned to determine the muscle architecture (pennation angle, muscle fiber length, and muscle thickness) and its relationship to lower extremity muscle strength in patients with Multiple Sclerosis (pwMS). The muscle architecture (pennation angle, muscle fiber length, and muscle thickness) and lower extremity muscle strength were assessed in 33 pwMS [13 Relapsing-Remitting MS (RRMS), 5 Primary Progressive MS (PPMS), 5 Secondary Progressive MS (SPMS), and 11 matched healthy controls (HC)]. Muscle architecture features were assessed with ultrasonography and muscle strength were assessed with a digital hand-held dynamometer. The rectus femoris muscle thickness and pennation angle, gastrocnemius muscle thickness, and the tibialis anterior pennation angle were significantly lower in pwMS compared to HC (p < 0.05). The strength of hip flexors, hip extensors, knee extensors, foot plantar, and foot dorsi flexors were lower in pwMS. In PPMS group, muscle strength of hip flexors was lower than RRMS and SPMS groups, and muscle strength of foot dorsi flexors was lower than RRMS (p < 0.05). In pwMS, positive correlations were found, between knee flexor strength and biceps femoris pennation angle. Also knee extensor strength and rectus femoris fiber length and muscle thickness were correlated positively (p < 0.05). According to our results the muscle architecture is affected in MS. The determination of architectural changes of lower extremity muscles may guide the arrangement of optimal strength exercises in functional rehabilitation programs.ClinicalTrials: NCT03766698.

Upper Extremity Motor Fatigability as an Early Indicator in Pediatric Onset Multiple Sclerosis

AIM

To adopt a computer-based protocol to assess grip fatigability in patients with pediatric-onset multiple sclerosis to provide detection of subtle motor involvement identifying those patients most at risk for future decline.

METHOD

Pediatric-onset multiple sclerosis patients were recruited during routine outpatient visits to complete a grip assessment and compared to a group of healthy age- and sex-matched controls. All participants completed a computer-based measurement of standard maximal grip strength and repetitive and sustained grip performance measured by dynamic and static fatigue indices.

RESULTS

A total of 38 patients with pediatric-onset multiple sclerosis and 24 healthy controls completed the grip protocol (right-hand dominant). There were no significant group differences in maximal grip strength bilaterally (right: 21.8 vs 19.9 kg, P = .25; left: 20.4 vs 18.7 kg, P = .33), although males with pediatric-onset multiple sclerosis were significantly less strong than healthy controls (right: 26.53 vs 21.23 kg, P = .009; left; 25.13 vs 19.63 kg, P = .003). Both dynamic and static fatigue indices were significantly higher bilaterally in pediatric-onset multiple sclerosis compared with healthy control participants (left-hand dynamic fatigue index: 18.6% vs 26.7%, P = .003; right-hand static fatigue index: 28.3% vs 41.3%, P < .001; left-hand static fatigue index: 31.9% vs 42.6%, P < .001).

CONCLUSION

Brief repeatable grip assessment including measures of dynamic and sustained static output can be a sensitive indicator of upper extremity motor involvement in pediatric-onset multiple sclerosis, potentially identifying those in need of intervention to prevent future disability.

Test-retest reliability of static and dynamic motor fatigability protocols using grip and pinch strength in typically developing children

Upper limb motor fatigability is an important debilitating factor for activities of daily living in clinical pediatric populations. However, the reliability of fatigability protocols in these populations is currently unknown. Therefore, the current study investigates test-retest reliability of a static and dynamic motor fatigability protocol for grip and pinch strength in typically developing children (TDC). Eighty-nine TDC (35 boys, 54 girls; mean age 10 years 11 months) used a grip and pinch dynamometer for static (sustained) and dynamic (repeated) contractions during 30s. For static motor fatigability (SFI), mean (Fmean) and SD (Fvar) of force were calculated, and for dynamic motor fatigability, F mean and number of peaks (Npeaks) were calculated. Intraclass correlation coefficients (ICC) were calculated. ICCs of F mean in static and dynamic motor fatigability were high (ICC: 0.94-0.96 and 0.91-0.98). ICCs were moderate to high for F var (ICC: 0.67-0.85). The SFI showed moderate ICCs (ICC: 0.69-0.77). ICCs were moderate to high for N peaks (ICC: 0.78-0.91).Conclusion: The results suggest that static and dynamic motor fatigability in for grip and pinch can be used reliably in TD children aged 6-18 years. What is Known: •Psychometric properties of motor fatigability protocols using grip and pinch in children are lacking. •Motor fatigability in grip and pinch is an important debilitating symptom in multiple neurologic populations. What is New: •Static fatigability can be investigated using a 30-s maximum sustained grip strength protocol in children. •Dynamic fatigability can be investigated using a 30-s maximum repeated grip strength protocol in children.

Lower extremity muscle power - A critical determinant of physical function in aging and multiple sclerosis

BACKGROUND AND PURPOSE

In aging, lower extremity muscle power is undoubtedly one of the most important parameters of neuromuscular function implicating lower extremity physical function (e.g. walking capacity). However, no previous studies have examined the combined effects of aging and multiple sclerosis (MS) on lower extremity muscle power concomitant with lower extremity physical function. The aim of this cross-sectional study was to examine potential decrements in pwMS vs. healthy controls (HC) across the adult lifespan in these outcomes.

METHODS

In the present explorative cross-sectional study, n = 42 pwMS (females n = 29 (69%); age = 53 ± 12 years (mean ± SD), range 31-78; patient determined disease steps score = 3.7 ± 1.7, range 0-7) and n = 49 age-matched HC (females n = 34 (69%); age = 56 ± 16 years, range 24-78) were enrolled, and divided into groups of young (≤ 44 years), middle-aged (45-59 years), and old (≥ 60 years). Muscle power was obtained from bilateral leg press (Power_LegPressPeak) and maximal chair rise (Power_ChairRise) using a linear encoder. Associations were assessed between muscle power and measurements of lower extremity physical function (5 x sit-to-stand (5STS); timed 25-foot-walk-test (T25FWT)).

RESULTS

Muscle power was reduced in pwMS vs. HC (Power_LegPressPeak -23[-34:-12]% (mean[95%CI]); Power_ChairRise -26[-35:-17]%) and was negatively associated with advanced age in both pwMS (decline per decade -0.40 W.kg^-1 and -2.53 W.kg^-1, respectively) and HC (decline per decade -0.42 W.kg^-1 and -2.03 W.kg^-1, respectively). Muscle power was strongly associated with physical function in pwMS (r²_range = 0.45-0.61, p < 0.01) yet only moderately associated in HC (r²_range = 0.18-0.39, p < 0.01).

CONCLUSION

The combined effects of MS and aging reveal substantial decrements in lower extremity muscle power that is accompanied by (and strongly associated with) decrements in lower extremity physical function. Consequently, lower extremity muscle power should be viewed as a clinically important factor (i.e. a critical determinant of lower extremity physical function) in pwMS. We propose that lower extremity muscle power should be specifically targeted by preventive and rehabilitative exercise strategies, especially in older pwMS.

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.

Timed Up and Go in men and women with Multiple Sclerosis: Effect of muscular strength

OBJECTIVE

People with Multiple Sclerosis (pwMS) often exhibit generalized weakness that affects several activities of daily life, particularly those relying on balance and gait. While it is known that such a symptom has a strong impact on mobility, to what extent muscular strength is linked with functional mobility in men and women with MS remains mostly unexplored. The aim of this study is to assess the existence of possible sex-related differences in functional mobility in pwMS, also considering the muscular strength capacity.

METHODS

Functional mobility and hand-grip strength (HGS) were assessed in 49 pwMS with mild-moderate disability using instrumental Timed-up-and-go (TUG) test carried out using an inertial sensor and digital dynamometry. We investigated the existence of sex-related differences in the duration of each TUG sub-phase and their correlation with the HGS.

RESULTS

No sex-related differences in TUG performance (either in terms of overall or sub-phase time) were found. Similar large negative correlations were found in men and women with MS between HGS and overall TUG and walking phase duration. However, changes in strength have a more marked impact in women as indicated by the different slope of the HGS-TUG time relationship., In women, HGS also appears significantly correlated with all TUG sub-phases, while in men this occurs only for overall TUG and walking time.

CONCLUSIONS

Rehabilitation and training programs for pwMS should take into account the peculiar features associated with the interaction between strength and mobility specific for each individual's sex to optimize their effectiveness.

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.

Multiple sclerosis-related fatigue: the role of impaired corticospinal responses and heightened exercise fatigability

It is unclear whether motor fatigability and perceived fatigue share a common pathophysiology in people with multiple sclerosis (PwMS). This cross-sectional investigation explored the relationship between the mechanisms of motor fatigability from cycling and fatigue severity in PwMS. Thirteen highly fatigued (HF) and thirteen nonfatigued (LF) PwMS and thirteen healthy controls (CON) completed a step test until volitional exhaustion on an innovative cycle ergometer. Neuromuscular evaluations involving femoral nerve electrical stimulation and transcranial magnetic stimulation were performed every 3 min throughout cycling. One-way ANOVA at baseline and exhaustion uncovered evidence of consistently smaller motor evoked potential (MEP) amplitudes (P = 0.011) and prolonged MEP latencies (P = 0.041) in HF as well as a greater decline in maximal voluntary contraction force (HF: 63 ± 13%; LF: 75 ± 13%; CON: 73 ± 11% of pre; P = 0.037) and potentiated twitch force (HF: 35 ± 13%; LF: 50 ± 16%; CON: 47 ± 17% of pre; P = 0.049) in HF at volitional exhaustion. Hierarchical regression determined that fatigue severity on the Fatigue Severity Scale was predicted by prolonged MEP latencies (change in r² = 0.389), elevated peripheral muscle fatigability (change in r² = 0.183), and depressive symptoms (change in r² = 0.213). These findings indicate that MS-related fatigue is distinguished by disrupted corticospinal responsiveness, which could suggest progressive pathology, but fatigability from whole body exercise and depressive symptoms also influence perceptions of fatigue in PwMS.NEW & NOTEWORTHY The etiology of fatigability from whole body exercise was examined for the first time to accurately elucidate the relationship between fatigue and fatigability in multiple sclerosis (MS). Compromised corticospinal responsiveness predicted fatigue severity, providing a novel, objective indicator of fatigue in MS. Although the impaired corticomotor transmission did not aggravate muscle activation in this group of people with multiple sclerosis (PwMS) of lower disability, heightened muscle fatigability was seen to contribute to perceptions of fatigue in PwMS.

Movement Velocity as A Measure of Exercise Intensity in Persons with Multiple Sclerosis: A Validity Study

Objectives: This study aims to analyse the validity (agreement between two methods) of the movement propulsive velocity (MPV) as an indicator of relative load in leg press (LP) and bench press (BP) exercises in persons with multiple sclerosis (MS). Methods: 18 persons with MS (sex = 55% male; age (mean ± SD) = 44.88 ± 10.62 years; body mass = 67.19 ± 10.63 kg; height = 1.66 ± 0.07 m; Expanded Disability Status Scale (EDSS) = 3.12 ± 1.73) performed an incremental loading test in BP and LP exercises in two separate sessions. Individual determination of the one-repetition maximum (1RM) and full load-velocity profile were obtained for each participant. Results: a significant linear relationship was observed between the %1RM load and the MPV in LP (%1RM = −133.58 × MPV + 117.44; r² = 0.84; standard error of the estimate (SEE) = 9.38%1RM) and BP (%1RM = −95.66 × MPV + 115.26; r² = 0.86; SEE = 9.82%1RM). In addition, no significant differences were found between the %1RM achieved directly and the %1RM obtained by the equation calculated from the linear regression (LP, p = 0.996; BP, p = 0.749). Conclusions: these results indicate that movement velocity can estimate the relative load in bench press and leg press exercises in persons MS.

Lack of effect on ambulation of dalfampridine-ER (4-AP) treatment in adult SMA patients

SMA is a genetically determined motor system disorder that results in muscle weakness, selective motor neuron death, muscle atrophy, and impaired functional mobility. In SMA model systems, long-term treatment with 4-aminopyridine (4-AP) has been shown to improve motor function. To assess tolerability and preliminary efficacy of 4-AP on walking ability, endurance and EMG in adult ambulatory SMA patients, we conducted a double blind, placebo control, crossover pilot study with dalfampridine (4-AP, 10 mg BID). The study is comprised of a short-term (2 weeks) treatment arm with 1-week washout and a long-term (6 weeks) treatment arm with a 2-week washout. The primary outcome measure, for which the study was powered, was the 6 min walk test (6MWT, distance and percent fatigue); secondary outcome measures were the Hammersmith Functional Motor Scale Expanded (HFMSE), Manual Muscle Testing (MMT), Myometry with Hand held Dynamometry, HHD) and Quantitative Gait Analyses. We performed electrophysiology, including CMAP and H-reflex, during the short-term treatment trial. The mean age of the 11 participants enrolled was 37.7 ± 11.9 years; 54.5% were male. Dalfampridine was safe and well tolerated and no patient suffered a serious adverse event related to treatment. We observed no statistically significant positive effects of dalfampridine treatment on our primary functional motor outcome (6MWT distance, fatigue). Dalfampridine had a positive effects on H-reflex and H/M ratio but not on CMAP amplitude. The effect on the H-reflex is of interest, as it suggests dalfampridine may enhance neuronal activity, an effect observed in SMA Drosophila and mouse models at doses (mg/kg) not recommended for clinical use. Larger studies with dalfampridine in SMA patients are needed to confirm our findings, especially in light of studies in other populations showing drug effects in only a subset of patients.

Peripheral Electrical Stimulation Paired With Movement-Related Cortical Potentials Improves Isometric Muscle Strength and Voluntary Activation Following Stroke

Background

Endogenous paired associative stimulation (ePAS) is a neuromodulatory intervention that has potential to aid stroke recovery. ePAS involves pairing endogenous electroencephalography (EEG) signals known as movement-related cortical potentials (MRCPs), with peripheral electrical stimulation. Previous studies have used transcranial magnetic stimulation (TMS) to demonstrate changes in corticomotor excitability following ePAS. However, the use of TMS as a measure in stroke research is limited by safety precautions, intolerance, and difficulty generating a measurable response in more severely affected individuals. We were interested in evaluating the effect of ePAS using more feasible measures in people with stroke. This study asks whether ePAS produces immediate improvements in the primary outcomes of maximal voluntary isometric contraction (MVIC) and total neuromuscular fatigue of the dorsiflexor muscles, and in the secondary outcomes of muscle power, voluntary activation (VA), central fatigue, peripheral fatigue, and electromyography activity.

Method

In this repeated-measures cross-over study, 15 participants with chronic stroke completed two interventions, ePAS and sham, in a randomized order. During ePAS, 50 repetitions of visually cued dorsiflexion were completed, while single pulses of electrical stimulation were delivered to the deep branch of the common peroneal nerve. Each somatosensory volley was timed to arrive in the primary motor cortex at the peak negativity of the MRCP. Univariate and multivariate linear mixed models were used to analyze the primary and secondary data, respectively.

Results

There was a statistically significant increase in dorsiflexor MVIC immediately following the ePAS intervention (mean increase 7 N), compared to the sham intervention (mean change 0 N) (univariate between-condition analysis p = 0.047). The multivariate analysis revealed a statistically significant effect of ePAS on VA of the tibialis anterior muscle, such that ePAS increased VA by 7 percentage units (95% confidence interval 1.3–12.7%). There was no statistically significant effect on total neuromuscular fatigue, muscle power, or other secondary measures.

Conclusion

A single session of ePAS can significantly increase isometric muscle strength and VA in people with chronic stroke. The findings confirm that ePAS has a central neuromodulatory mechanism and support further exploration of its potential as an adjunct to stroke rehabilitation. In addition, the findings offer alternative, feasible outcome measures for future research.

Clinical trial registration

Australia New Zealand Clinical Trials Registry ACTRN12617000838314 (www.anzctr.org.au), Universal Trial Number U111111953714.

Upper and lower limb performance fatigability in people with multiple sclerosis investigated through surface electromyography: a pilot study

OBJECTIVE

Fatigue experienced by people with multiple sclerosis (pwMS) is multidimensional, consisting of different components, such as perceived, physical and cognitive fatigue and performance fatigability. At present, there is no gold standard to assess performance fatigability in pwMS; therefore, we aimed to determine whether, during a fatiguing task, average rectified value (ARV), mean frequency of the power spectrum (MNF), muscle fiber conduction velocity (CV) and fractal dimension (FD) of surface electromyography (sEMG) may be used as indirect indices of performance fatigability. Moreover, we analyzed whether a three-week rehabilitation program impacts on performance fatigability in pwMS, and whether a relationship between sEMG parameters and trait levels of perceived fatigability, before and after rehabilitation, does exist.

APPROACH

Twenty-one pwMS performed a 20% maximal voluntary contraction (MVC) of 1 min, and afterwards a 60% MVC held until exhaustion. sEMG signals were detected from the biceps brachii, vastus medialis and vastus lateralis. Performance fatigability was determined at entry to (t ₀) and discharge from (t ₁) rehabilitation. Perceived fatigability was measured at t ₀ and t ₂, one month after rehabilitation.

MAIN RESULTS

ARV, MNF, CV and FD rates of change showed significant changes at t ₀ and t ₁ (p  <  0.05) during the high-level contraction in the BB, but rather limited in the vastii muscles. Moreover, rehabilitation did not induce any reductions in either perceived or performance fatigability. No significant correlations between ARV, MNF, CV and FD rates of change during the 60% MVC and perceived fatigability, at t ₀ and t ₂, were found.

SIGNIFICANCE

Our findings suggest that the sEMG parameters are useful for indirectly assessing performance fatigability in pwMS during sub-maximal fatiguing contractions, particularly in the biceps brachii.

Quantifying muscle fatigue during walking in people with multiple sclerosis

BACKGROUND

This study aimed to examine muscle fatigue in lower leg muscles in of people with multiple sclerosis and healthy controls, and whether muscle fatigue coincided with potential changes in gait.

METHODS

In this case-control study, people with multiple sclerosis (n = 8; 3male; mean age (SD) = 49.7 (9.6) yr) and age-matched healthy controls (n = 10; 4male; mean age (SD) = 47.4 (8.7) yr) walked on a treadmill for 12-min at self-paced speed. Muscle fatigue was indirectly quantified by a decrease in median frequency and increase in root mean square of surface electromyographic recordings of lower leg muscles. Walking speed, ankle push-off power and net ankle work were calculated from marker positions and force plate data using inverse dynamic calculations.

RESULTS

People with multiple sclerosis showed larger decreases in median frequency of soleus (most affected leg: p = 0.003; least affected leg: p = 0.009) and larger increases in root mean square of soleus (most and least affected leg: p = 0.037), gastrocnemius medialis (most affected leg: p = 0.003; least affected leg: p = 0.005) and lateralis (most and least affected leg: p < 0.001) compared to controls. Walking speed (p = 0.001), ankle push-off power (most affected leg: p = 0.018; least affected leg: p = 0.001) and net work around the ankle (most affected leg: p = 0.046; least affected leg: p = 0.001) were lower in people with multiple sclerosis compared to controls, but increased in both groups.

INTERPRETATION

The results yield preliminary evidence that soleus muscles of people with multiple sclerosis fatigue during prolonged walking. Changes in electromyography of gastrocnemius muscles could however be related to muscle fatigue, changes in gait or a combination.

Local dynamic stability during long-fatiguing walks in people with multiple sclerosis

BACKGROUND

Altered balance/stability during walking is common in people with multiple sclerosis (PwMS). While dynamic gait stability has been related to falling and localized muscle fatigue, it has rarely been studied in MS. Specifically, the effects of walking-related fatigue on dynamic stability are unclear in PwMS.

RESEARCH QUESTIONS

1) Are temporal changes in dynamic stability during long-walks different among PwMS and healthy controls (HC)? 2) Is there a relationship between stability and walking performance changes in PwMS?

METHODS

Twenty-five PwMS and ten HC participated in the six-minute walk test (6MWT) wearing six-wireless inertial sensors. Local dynamic stability (LDS) during gait was quantified by maximum-finite-time Lyapunov exponents (λS), where larger λS indicates less stable dynamics. Linear mixed models were fit to compare changes in LDS and walking performance over time among two groups. Additionally, the percent changes in λS and distance from minute 1 to 6 were recorded as Dynamic Stability Index (DSI6-1) and Distance-Walked Index (DWI6-1) respectively. Finally, Pearson correlation compared the association between DSI6-1 and DWI6-1.

RESULTS

A significant group*time interaction was found for LDS. PwMS did not have different LDS than HC until minute-4 of walking, and differences persisted at minute-6. Further, PwMS walked significantly shorter distances and demonstrated a greater decline in walking performance (DWI6-1) during the 6MWT. Finally, DSI6-1 and DWI6-1 were significantly correlated in PwMS. Significance The dynamic stability differences among PwMS and HC were only apparent after 3-minutes of walking and ∼60% of PwMS became less stable over time, supporting the use of long walks in MS to capture stability changes during the motor task performance. A significant relationship between the decline in stability and poor walking performance over time during the 6MWT suggested a possible role of walking-related fatigue in the worsening of balance during long walks in PwMS.

The importance of lower-extremity muscle strength for lower-limb functional capacity in multiple sclerosis: Systematic review

BACKGROUND

Lower-limb functional capacity is impaired in most people with multiple sclerosis (PwMS). Reductions in lower-extremity muscle mechanical function (e.g., muscle strength) appear to have critical implications for lower-limb functional capacity. However, no review has summarized the current knowledge about the importance of muscle strength for functional tasks in PwMS. Expanding the current knowledge would advance the design of both clinical and research interventions aiming to improve functional capacity in PwMS.

OBJECTIVES

(1) To identify studies that measured lower-extremity muscle mechanical function and lower-limb functional capacity outcomes in PwMS, and (2) to map associations between muscle strength and functional capacity.

METHODS

This review was based on a literature search (databases: PubMed, Embase). Included studies had to report data on lower-extremity muscle mechanical function and lower-limb functional capacity outcomes in PwMS. The associations between muscle strength and functional capacity were analyzed by using the reported correlation coefficients (R) recalculated to the determination coefficient R². Randomized trials and observational studies were included.

RESULTS

A total of 59 articles were reviewed; 17 (773 participants) reported associations between muscle strength and functional capacity. Lower-extremity muscle mechanical function explained a significant part of the variance in most lower-limb functional capacity tests (approximately 20-30%). This was particularly evident in muscle strength from the weakest leg. Muscle strength was predominantly tested on knee extensors and knee flexors by using isokinetic dynamometry during maximal isometric (0°/s) and dynamic (30-60°/s) contractions. Walking tests such as the timed 25-Foot Walk Test and 10-Min, 2-Min and 6-Min Walk Test were the most frequently performed functional capacity tests.

CONCLUSIONS

In PwMS, muscle strength of particularly the weakest limb explains 20% to 30% of the variance across a number of lower-limb functional capacity tests. Thus, exercise programs should focus on increasing lower-extremity muscle mechanical function in PwMS and minimizing strength asymmetry between limbs.

A framework for closing the loop between human experts and computational algorithms for the assessment of movement disorders

Clinical assessment of abnormal neuromechanics is typically performed by manipulation of the affected limbs; a process with low inter- and intra-rater reliability. This paper aims at formalizing a framework that closes the loop between a clinician's expertise and computational algorithms, to enhance the clinician's diagnostic capabilities during physical manipulation. The framework's premise is that the dynamics that can be measured by manipulation of a limb are distinct between movement disorders. An a priori database contains measurements encoded in a space called the information map. Based on this map, a computational algorithm identifies which probing motions are more likely to yield distinguishing information about a patient's movement disorder. The clinician executes this movement and the resulting dynamics, combined with clinician input, is used by the algorithm to estimate which of the movement disorders in the database are most probable. This is recursively repeated until a diagnosis can be confidently made. The main contributions of this paper are the formalization of the framework and the addition of the information map to select informative movements. The establishment of the framework provides a foundation for a standardized assessment of movement disorders and future work will aim at testing the framework's efficacy.

Portable fixed dynamometry to quantify ankle dorsiflexion force

INTRODUCTION

Quantifying muscle strength is critical in clinical and research settings. A rapid and objective method is ideal. The primary objective of this study was to examine the reliability of a novel device, the rapid objective quantification- tibialis anterior (ROQ-TA), which quantifies the dorsiflexion force of the tibialis anterior, and to assess its validity against isokinetic dynamometry (IKD).

METHODS

Ankle dorsiflexion of 20 healthy subjects was assessed by 3 modalities, ROQ-TA, manual muscle testing, and isokinetic dynamometry, over 2 testing sessions.

RESULTS

The intraclass correlation coefficient [ICC_(2,1) ] for reliability was 0.872 (0.677-0.949) for the ROQ-TA and 0.892 (0.728-0.957) for IKD. For validity, the ICC_(2,1) values for the ROQ-TA and IKD were in good agreement, with 0.672 (0.17-0.87) in the first testing session and 0.769 (0.42-0.91) in the second session.

DISCUSSION

The ROQ-TA is a valid and reliable device to test ankle dorsiflexion force in a healthy population. Muscle Nerve, 2018.

Force decline after low and high intensity contractions in persons with multiple sclerosis

OBJECTIVE

Force decline during strong contractions is dominated by changes in the periphery whereas during weaker contraction changes in voluntary activation become more important. We compared force decline and contributing factors in persons with multiple sclerosis (PwMS) during low and high intensity contractions.

METHODS

Index finger abduction force, force evoked by electrical stimulation of the ulnar nerve at rest (RTw), and during MVCs were investigated in 19 PwMS and 19 controls. Participants performed contractions in sets of six contractions (7 s-on, 3 s-off) at 25% or 80% MVC. After each set, a 5 s-MVC was performed with superimposed nerve stimulation followed by RTw. Contractions were repeated until MVC dropped below 80% of initial MVC.

RESULTS

Low compared to high intensity contractions caused a greater decline in voluntary activation and a smaller decline in RTw. Compared to controls, PwMS accomplished equal sets of contractions but showed a smaller decline in RTw. Female PwMS showed poorer voluntary activation. The number of low intensity contractions was associated with sense of fatigue in PwMS.

CONCLUSION

Although, no difference in fatigability was observed, the mechanism contributing to force decline differed between PwMS and controls during submaximal contractions.

SIGNIFICANCE

During weak contractions, fatigue and fatigability are associated in PwMS.

The relationship between corticospinal tract integrity and lower-extremity strength is attenuated when controlling for age and sex in multiple sclerosis

Muscle weakness, particularly in the lower-extremities, is common in multiple sclerosis (MS) and seemingly results from damage along white matter pathways in the central nervous system including the corticospinal tract (CST). This study examined CST structural integrity indicated by diffusion tensor imaging (DTI) related metrics (fractional anisotropy [FA], mean diffusivity [MD], radial diffusivity [RD], and axial diffusivity [AD]) as correlates of knee flexor (KF) and knee extensor (KE) muscle strength in MS. We included 36 persons with MS who underwent MRI and measurements of peak KE and KF strength using an isokinetic dynamometer. We examined associations using bivariate Spearman (rs) and partial Spearman correlation (prs) analyses controlling for age and sex. Peak KF strength was significantly associated with FA (rs = 0.42) and RD (rs = -0.36) and peak KE strength was significantly associated with MD (rs = -0.47) and RD (rs = -0.36). The correlations were attenuated after controlling for age and sex, but the relationship between KF strength and FA demonstrated a trend towards significance (prs = 0.33, p = 0.056). We provide evidence that the anatomical integrity of the CST may be associated with lower-extremity strength in MS. The attenuated correlations when controlling for age and sex suggest these factors, rather than MS per se, may be important contributors toward an association between CST DTI-metrics and KF and KE strength. Future rehabilitation trials of resistance training should consider including CST integrity as an outcome and/or predictor of strength adaptations.

How does strength training and balance training affect gait and fatigue in patients with Multiple Sclerosis? A study protocol of a randomized controlled trial

INTRODUCTION

Multiple sclerosis (MS) is characterized by a demyelination that results in reduced conductivity in the somatosensory nervous system, decreased muscle strength, vestibular alteration, and severe fatigue. Progressive resistance training (PRT) has proven to be a promising intervention showing a positive effect on muscle strength. Another promising intervention frequently used in neuro-rehabilitation is task specific training where also Balance and Motor Control Training (BMCT) are incorporated. Interestingly, the principles of BMCT do fundamentally contrast the principles of PRT in terms of variation in movement pattern, loading and repetitions. Consequently, knowledge of any diverse effect would be of clinical relevance.

AIM

To evaluate the effects of PRT and BMCT on gait, balance and fatigue in persons with MS.

METHOD

A three-armed multi-center, single-blinded cluster randomized controlled trial with two intervention groups (1. PRT of the lower extremities. 2. BMCT that challenges gait function) and a control group that receives usual care while on a waitlist for a combined PRT + BMCT intervention performed after the two interventions groups have completed their interventions. The interventions last ten weeks with two sessions per week, in groups of 3-6 participants. Number of participants is 30 per intervention - 90 in total. Primary outcome measures for gait function are the Timed 25 Foot Walk (T25FW) and the Six Spot Step Test (SSST). Secondary outcomes are fatigue, perceived gait function, temporo-spatial gait characteristics, balance and strength.Inclusion criteria are: EDSS 2-6, SSST >8 sec and T25FW >5 sec. Exclusion: Recent attacks and ongoing intensive rehabilitation.

ANALYSIS

The effects in the three groups are examined in a mixed effects regression analysis with group and time as fixed effects and center and patient within center as random effects. Spearman or Pearson correlation analysis will be conducted on baseline data to determine associations between the primary outcomes on gait function and the secondary outcomes on fatigue, spatial gait parameters, balance and patient reported measures.

TRIAL REGISTRATION

The study is approved by the Regional ethical committee and registered at clinicaltrials.gov, NCT02870023.

Motor fatigability in persons with multiple sclerosis: Relation between different upper limb muscles, and with fatigue and the perceived use of the arm in daily life

BACKGROUND

Motor fatigability is increasingly acknowledged in persons with MS (pwMS). It is unknown whether fatigability is generalized across upper limb muscles and relates to fatigue and perceived difficulties in upper limb use.

METHODS

This observational case-controlled study included twenty PwMS (median EDSS = 3, range 1.5-6.5) and twenty healthy controls who performed 30″ sustained maximal muscle contractions for index finger abduction, hand grip, elbow flexion and shoulder abduction. A static fatigue index (SFI) was calculated to assess motor fatigability for each muscle group. PwMS completed the Fatigue Severity Scale (FSS) and Modified Fatigue Index Scale (MFIS), to quantify severity and perceived impact of fatigue and the Manual Ability Measure (MAM-36) reflecting perceived difficulty in using the upper limbs. Comparisons between groups and muscles was made by t-tests. Associations between outcomes were calculated with correlation coefficients.

RESULTS

Fatigue was highest in pwMS. PwMS showed preserved muscle strength and a greater motor fatigability in elbow flexors compared to healthy controls. SFI of elbow flexors and shoulder abductors were associated, and contributed to FSS and MFIS. SFI of elbow flexors and finger abductors predicted half of the variation in MAM-36.

CONCLUSION

Increased motor fatigability was only present in elbow flexors of PwMS, indicating that expression of motor fatigability is not generalized. Fatigability was associated with perceived fatigue (impact) and daily life upper limb use. Results are preliminary given the small sample size with predominantly persons with mild MS.

Exercise prescription for patients with multiple sclerosis; potential benefits and practical recommendations

BACKGROUND

Multiple sclerosis (MS) can result in significant mental and physical symptoms, specially muscle weakness, abnormal walking mechanics, balance problems, spasticity, fatigue, cognitive impairment and depression. Patients with MS frequently decrease physical activity due to the fear from worsening the symptoms and this can result in reconditioning. Physicians now believe that regular exercise training is a potential solution for limiting the reconditioning process and achieving an optimal level of patient activities, functions and many physical and mental symptoms without any concern about triggering the onset or exacerbation of disease symptoms or relapse.

MAIN BODY

Appropriate exercise can cause noteworthy and important improvements in different areas of cardio respiratory fitness (Aerobic fitness), muscle strength, flexibility, balance, fatigue, cognition, quality of life and respiratory function in MS patients. Aerobic exercise training with low to moderate intensity can result in the improvement of aerobic fitness and reduction of fatigue in MS patients affected by mild or moderate disability. MS patients can positively adapt to resistance training which may result in improved fatigue and ambulation. Flexibility exercises such as stretching the muscles may diminish spasticity and prevent future painful contractions. Balance exercises have beneficial effects on fall rates and better balance. Some general guidelines exist for exercise recommendation in the MS population. The individualized exercise program should be designed to address a patient's chief complaint, improve strength, endurance, balance, coordination, fatigue and so on. An exercise staircase model has been proposed for exercise prescription and progression for a broad spectrum of MS patients.

CONCLUSION

Exercise should be considered as a safe and effective means of rehabilitation in MS patients. Existing evidence shows that a supervised and individualized exercise program may improve fitness, functional capacity and quality of life as well as modifiable impairments in MS patients.

Relationship between perceived fatigue and performance fatigability in people with multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Perceived fatigue (i.e., subjective perception of reduced capacity) is one of the most common and disabling symptoms for people with multiple sclerosis (MS). Perceived fatigue may also be related to performance fatigability (i.e., decline in physical performance over time), although study findings have been inconsistent.

OBJECTIVE

To locate all studies reporting the relationship between perceived fatigue and fatigability in people with MS, determine the population correlation, and examine moderating variables of the correlation size.

METHODS

In accordance with PRISMA guidelines, systematic searches were completed in Medline, PsychInfo, Google Scholar, and the Cochrane Library for peer-reviewed articles published between March 1983 and August 2016. Included articles measured perceived fatigue and performance fatigability in people with MS and provided a correlation between measures. Moderator variables expected to influence the relationship were also coded. Searches located 19 studies of 848 people with MS and a random-effects model was used to pool correlations.

RESULTS

The mean correlation between fatigue and fatigability was positive, "medium" in magnitude, and statistically significant, r=0.31 (95% CI=0.21, 0.42), p<0.001. Despite moderate between-study heterogeneity (I²=46%) no statistically significant moderators were found, perhaps due to the small number of studies per moderator category.

CONCLUSION

There is a significant relationship between perceived fatigue and fatigability in MS, such that people reporting elevated fatigue also are highly fatigable. The size of the relationship is not large enough to suggest fatigue and fatigability are the same construct, and both should continue to be assessed independently.

The Assessment of Motor Fatigability in Persons With Multiple Sclerosis: A Systematic Review

Background. Persons with multiple sclerosis (PwMS) are often characterized by increased motor fatigability, which is a performance change on an objectively measured criterion after any type of voluntary muscle contractions. This review summarizes the existing literature to determine which protocols and outcome measures are best to detect or study motor fatigability and the underlying mechanisms in MS. Methods. Two electronic databases, PubMed and Web of Science, were searched for relevant articles published until August 2016 with a combination of multiple sclerosis, fatigability, muscle fatigue, and motor fatigue. Results. A total of 48 articles were retained for data extraction. A variety of fatigability protocols were reported; protocols showed differences in type (isometric vs concentric), duration (15 to 180 s), and number of contractions (fixed or until exhaustion). Also, 12 articles reported motor fatigability during functional movements, predominantly assessed by changes in walking speed; 11 studies evaluated the mechanisms underlying motor fatigability, using additional electrical nerve or transcranial magnetic stimulation. Three articles reported psychometrics of the outcomes. Conclusions. The disparity of protocols and outcome measures to study different aspects of motor fatigability in PwMS impedes direct comparison between data. Most protocols use maximal single-joint isometric contractions, with the advantage of high standardization. Because there is no head-to-head comparison of the different protocols and only limited information on psychometric properties of outcomes, there is currently no gold standard to assess motor fatigability. The disability level, disease phenotype, and studied limb may influence the assessment of motor fatigability in PwMS.