Postural control in women with multiple sclerosis: effects of task, vision and symptomatic fatigue

Postural behaviour in people with multiple sclerosis: A complexity paradox

BACKGROUND

Balance deficits are a major concern for people with multiple sclerosis (pwMS). Measuring complexity of motor behaviour can offer an insight into MS-related changes in adaptability of the balance control system when dealing with increasingly complex tasks.

QUESTION

Does postural behaviour complexity differ between pwMS at early stages of the disease and healthy controls (HC)? Does postural behaviour complexity change across increasingly complex tasks?

METHODS

Forty-eight pwMS and 24 HC performed four increasingly complex postural tasks with eyes open (EO), eyes closed (EC), on firm (FS) and compliant surface (CS). Lumbar and sternum sensors recorded 3D acceleration, from which complexity index (CI) was calculated using multiscale sample entropy (MSE) in the frontal and sagittal planes.

RESULTS

We found that only the complexity index in both planes during the eyes closed on compliant surface (EC-CS) task was significantly lower in pwMS compared to HC. We also found that complexity in pwMS was significantly lower during EC-CS compared to the other three tasks when using both lumbar and sternum sensors.

SIGNIFICANCE

Increasing the complexity of postural tasks reduces the complexity of postural behaviour in pwMS. This paradox may reflect reduced adaptability of the sensorimotor integration processes at early stages of MS. CI can provide a different perspective on balance deficits and could potentially be a more sensitive biomarker of MS progression and an early indicator of balance deficit.

The influence of cognitive load and vision variability on postural balance in adolescents with intellectual disabilities

Introduction

This study aimed to investigate the impact of cognitive load, particularly its escalation during the execution of the same test, under varying vision conditions, on postural balance among adolescents with intellectual disability (ID).

Methods

Twenty adolescents underwent balance assessments under different visual conditions (Open Eyes (OE), Closed Eyes (CE), Flash, Goggles, Visual Stimulation (VS)) and task settings (Single Task (ST), Dual Task (DT) without challenges, and DT with challenges). The cognitive test was assessed using Verbal Fluency (VF).

Results and discussion

Significant effects were found for Task (p < 0.001, ηp2 = 0.85), indicating that CoP values significantly increased (p < 0.05) with the introduction of the DT. Dual Task Cost (DTC) demonstrated significant effects for Vision (p = 0.008, ηp2 = 0.62), with values varying significantly (p < 0.05) among different vision conditions, especially in CE and Flash conditions. Visual Dependency Quotient (VDQ) analyses revealed significant effects of condition (p < 0.001, ηp2 = 0.84), with significant changes observed in CE/OE and Flash/OE conditions (p < 0.05). Significant effects were observed for Cognitive performance in the Challenge condition (p < 0.001, ηp2 = 0.86), with decreased performance with cognitive task challenges, particularly in Flash and Goggles conditions (p < 0.05). In conclusion, cognitive tasks, especially challenging ones, and visual variations significantly impact postural balance in adolescents with ID.

Exploring Factors Associated with Falls in Multiple Sclerosis: Insights from a Scoping Review

Multiple sclerosis (MS) is a chronic inflammatory condition that causes demyelination of the central nervous system accompanied by a wide range of symptoms. The high prevalence of falls among patients diagnosed with MS within the initial six months highlights the importance of this issue. The objective of this study is to identify factors associated with falls in MS patients in order to increase awareness and reduce the risk of falls. This scoping review used specific Mesh terms to formulate the literature search around falls and MS using Medline, Google Scholar, Scopus, and Embase search engines. English papers published between 2012 and 2022, studies with a clear definition of falls, McDonald's diagnostic criteria for MS, and those with Expanded Disability Status Scale (EDSS) or Patient Determined Disease Steps (PDDS) scores were included. Critical data from the selected articles were extracted and classified according to the different factors associated with falls in MS patients. Eighteen articles were included in this review. The most important factors associated with falls in MS patients identified were the severity and progression of the disease, mobility and balance problems, bladder dysfunction, fear of falling, fatigue, and cognitive dysfunction. In conclusion, this scoping review yielded the most common factors associated with falls in patients with MS. Study findings can be used to develop future interventions focusing on improving mobility, proprioception, and balance to decrease fall risk and injury amongst MS patients.

The Effects of Optical Flow Perturbations on Standing Balance in People With Multiple Sclerosis

Multiple sclerosis is a neurodegenerative disease that causes balance deficits, even in early stages. Evidence suggests that people with multiple sclerosis (PwMS) rely more on vision to maintain balance, and challenging balance with optical flow perturbations may be a practical screening for balance deficits. Whether these perturbations affect standing balance in PwMS is unknown. Therefore, the purpose of this study was to examine how optical flow perturbations affect standing balance in PwMS. We hypothesized that perturbations would cause higher variability in PwMS compared with matched controls during standing and that standing balance would be more susceptible to anterior-posterior (A-P) perturbations than medial-lateral (M-L) perturbations. Thirteen PwMS and 13 controls stood under 3 conditions: unperturbed, M-L perturbation, and A-P perturbations. A-P perturbations caused significantly higher A-P trunk sway variability in PwMS than controls, although both groups had similar center-of-pressure variability. Both perturbations increased variability in A-P trunk sway and center of pressure. Trunk variability data supported the hypothesis that PwMS were more susceptible to optical flow perturbations than controls. However, the hypothesis that A-P perturbations would affect balance more than M-L perturbations was partially supported. These results suggest potential for optical flow perturbations to identify balance deficits in PwMS.

Associations between respiratory function, balance, postural control, and fatigue in persons with multiple sclerosis: an observational study

Introduction

Fatigue, postural control impairments, and reduced respiratory capacities are common symptoms in persons diagnosed with Multiple Sclerosis (MS). However, there is a paucity of evidence establishing correlations among these factors. The aim of this study is to analyze respiratory function in persons with MS compared to the control group as well as to analyze the relationship between fatigue, respiratory function and postural control in persons with MS.

Materials and methods

A total of 17 persons with MS and 17 healthy individuals were enrolled for this cross-sectional study. The evaluated parameters included fatigue assessed using the Visual Analog Scale-fatigue (VAS-F) and the Borg Dyspnea Scale, postural control assessed through the Mini Balance Evaluation System Test (Mini-BESTest), Berg Balance Scale (BBS), Timed Up and Go (TUG) test, and Trunk Impairment Scale (TIS); and respiratory capacities measured by Maximum Inspiratory Pressure (MIP), Maximum Expiratory Pressure (MEP), Forced Vital Capacity (FVC), Forced Expiratory Volume in the first second (FEV1), FEV1/FVC ratio, Diaphragmatic excursion and diaphragmatic thickness.

Results

A very high correlation was observed between the Borg Dyspnoea Scale and the BBS (r = -0.768), TUG (0.867), and Mini-BESTest (r = -0.775). The VAS-F exhibited an almost perfect correlation solely with the TUG (0.927). However, none of the variables related to fatigue exhibited any correlation with the respiratory variables under study. Balance-related variables such as BBS and Mini-BESTest demonstrated a very high and high correlation. Respectively, with respiratory function variables MEP (r = 0.783; r = 0.686), FVC (r = 0.709; r = 0.596), FEV1 (r = 0.615; r = 0.518). BBS exhibited a high correlation with diaphragmatic excursion (r = 0.591). Statistically significant differences were noted between the persons with MS group and the control group in all respiratory and ultrasound parameters except for diaphragmatic thickness.

Conclusion

The findings suggest that decreased postural control and balance are associated with both respiratory capacity impairments and the presence of fatigue in persons with MS. However, it is important to note that the alterations in respiratory capacities and fatigue are not mutually related, as indicated by the data obtained in this study. Discrepancies were identified in abdominal wall thickness, diaphragmatic excursion, and respiratory capacities between persons with MS and their healthy counterparts.

People With Low Back Pain Exhibit Higher Trunk Muscle Activity and Impaired Postural Control During Static and Dynamic Functional Tasks: A Cross-Sectional Study

The study compared superficial trunk muscle activity and postural control among an active extension subgroup of people with nonspecific chronic low back pain (AE-NSCLBP) with painfree controls during functional tasks. Thirty-two people (17 people with low back pain [LBP] and 15 painfree controls) participated in this study. Muscle activity of 5 trunk muscles and postural control were investigated during both standing tasks (eyes open/closed; single/double-leg balance) and dynamic functional tasks (spinal forward flexion and return, and a sit to stand transfer). Results showed that during single-leg standing, people with AE-NSCLBP exhibit higher muscle activity than painfree controls for 3 trunk muscles, especially with their eyes closed. There were no significant differences in muscle activity between eye conditions during double-leg standing and sit to stand transfer, forward flexion, and return from flexion. The AE-NSCLBP subgroup also demonstrated significantly impaired postural control (lower time to boundary) in 4 of 8 conditions, especially during single-leg standing and with their eyes closed. These findings show people with LBP typically demonstrated greater trunk muscle activity and poorer postural control while maintaining standing posture. This pattern was most evident when the postural challenge was higher, such as single-leg standing or with eyes closed. While this study design cannot infer causality, these findings have implications for LBP rehabilitation, particularly regarding approaches which seek to alter muscle activation among people with LBP.

The effect of fatigue on postural control in individuals with multiple sclerosis: a systematic review

BACKGROUND

Fatigue is the most disabling symptom for individuals with multiple sclerosis (MS), which can significantly affect postural control (PC) by impairing the ability of the central nervous system to modulate sensory inputs and coordinate motor responses. This systematic review aimed to investigate the effect of fatigue on PC in individuals with MS..

METHODS

This systematic review is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline and registered in PROSPERO with ID CRD42022376262. A systematic search was performed in the Web of Science, PubMed, Scopus, and Google Scholar until January 2023, and a manual search was performed using the reference lists of included studies. Two authors independently selected the studies, extracted data, and evaluated their methodological quality using the Downs and Black checklist. The process was later discussed with a third author..

RESULTS

Five studies were included in this review, of which consistent evidence investigating a direct relationship between fatigue and PC in individuals with MS. All the studies reported negative effects on PC. Four studies employed walking tests as their primary protocol for inducing fatigue, while one study implemented a strength testing protocol for both legs, serving as a fatigue-inducing activity.

CONCLUSIONS

The evidence suggests that individuals with MS may experience PC deficits due to fatigue. However, the present body of literature exhibits limitations regarding its quality and methodology. Gender differences, balance, fatigue task, and muscle function are essential factors that need to be considered when investigating the relationship between fatigue and PC deficits in MS. Further high-quality research is necessary to comprehend the complex interplay between MS-related fatigue and PC deficits after physical activity.

Impaired foot vibration sensitivity is related to altered plantar pressures during walking in people with multiple sclerosis

BACKGROUND

Balance and mobility impairment are two of the most common and debilitating symptoms among people with multiple sclerosis (MS). Somatosensory symptoms, including reduced plantar cutaneous sensation, have been identified in this cohort. Given the importance of the somatosensory system in gait, it is likely that impaired plantar sensation may play a role in the walking adaptations commonly observed in people with MS, including decreased stride length and increased stride width and dual support time, often described as a cautious gait strategy. Understanding the contributions of plantar sensation to these alterations may provide targets for interventions that seek to improve sensory feedback and normalize gait patterns. This cross-sectional study determined whether individuals with MS who demonstrate reduced sensitivity of the plantar surfaces also demonstrate altered plantar pressure distributions during walking compared to a control cohort.

METHODS

Twenty individuals with MS and twenty age- and sex-matched control participants walked barefoot at preferred and three matched speeds. Participants walked across a walkway with an embedded pressure plate used to quantify pressures within ten plantar zones. In addition, vibration perception thresholds were assessed at four sites on the plantar surface.

RESULTS

Individuals with MS demonstrated increased peak total plantar pressures compared to control participants, that increased with walking speed. For the MS group, plantar pressures were higher on the less sensitive foot, although pressures on both feet exceeded those of the control cohort. Positive correlations between vibration perception threshold and peak total pressure were evident, although generally stronger in the MS cohort.

CONCLUSION

A relationship between plantar vibration sensitivity and pressure could indicate that individuals with MS seek to increase plantar sensory feedback during walking. However, because proprioception may also be impaired, increased plantar pressure could result from inaccurate foot placement. Interventions targeting improved somatosensation may have the potential to normalize gait patterns and should be investigated.

Combined effect of gender differences and fatiguing task on postural balance, functional mobility and fall risk in adults with multiple sclerosis: A preliminary study

AIM

To investigate the gender difference effect on postural balance, functional mobility, and fall risk after performing a fatiguing task in adults with multiple sclerosis (MS).

METHODS

Eleven women (30.91 ± 8.19 years) and seven men (30.29 ± 7.99 years) with relapsing-remitting MS performed a fatiguing task: three sets of the Five-repetition Sit-To-Stand Test (5-STST) were performed before and after the six-minute WalkTest (6MWT). Bipedal postural balance in eyes open and eyes closed conditions were assessed prefatigue (T0) and postfatigue (T3) using a force platform. Unipedal balance, functional mobility (Timed Up and Go Test), fall risk (Four Square Step Test) and fatigue [Visual Analogue Scale of Fatigue (VASF)] were assessed at T0 and T3. Heart rate (HR) and Rating of Perceived Exertion (RPE) were recorded before (only for HR), during and after the fatiguing task.

RESULTS

Compared to women, men showed an impairment of posturographic parameters [mean center of pressure (CoP) velocity (CoPVm) in both conditions (p < 0.05); CoP sway area (CoPAr) in both conditions (p < 0.01)], unipedal balance on the dominant leg (p <0.001), mobility (p<0.001) and an increased fall risk (p < 0.05). No gender differences were observed in 6MWT, 5-STST, HR, RPE, and VASF.

CONCLUSION

This preliminary study showed that fatiguing task negatively affected postural control, mobility and fall risk only in men. These gender differences were inconclusive but could be taken into account in postural balance rehabilitation programs for MS persons.

Examining the Relationship Between Reactive Stepping Outcomes and Falls in People With Multiple Sclerosis

OBJECTIVE

Reactive stepping is critical for preventing falls and is impaired in people with multiple sclerosis (PwMS); however, which aspects of stepping relate to falls remains poorly understood. Identifying outcomes most related to falls is a first step toward improving rehabilitation for fall prevention. The purpose of this study was to assess whether reactive step latency or length during forward and backward losses of balance were related to a history of falls in PwMS.

METHODS

Of the 111 PwMS who participated in this study, 76 reported no falls in the previous 6 months, whereas 36 reported 1 or more falls. Participants completed 3 forward and 3 backward treadmill-induced reactive steps from stance. Step length (centimeters) and step latency (milliseconds) were measured using motion capture and analyzed via MATLAB.

RESULTS

Participants with a history of falls had significantly slower step latencies during backward stepping, but not forward stepping, than those without a history of falls. Step length did not differ between groups. Slower step latencies during backward stepping significantly increased the odds of having experienced a fall (β = .908, SE = 0.403, odds ratio = 2.479, 95% CI = 1.125 to 5.464).

CONCLUSION

PwMS and a history of falling show delayed step onsets during backward reactive stepping. Specifically, for every 10-millisecond increase in step latency, PwMS were 2.5 times more likely to have a fall history. Although clinical trials are necessary to determine whether interventions targeting reactive stepping reduce falls in PwMS, the current work indicates that the latency of steps may be a relevant target for this work.

IMPACT

Subsequent fall prevention clinical trials should consider targeting backward reactive step latency to further assess its relevance for rehabilitation in PwMS.

LAY SUMMARY

If you have MS and a history of falls, you may be more likely to have delayed reactive step latencies.

Feasibility and safety of an immersive virtual reality-based vestibular rehabilitation programme in people with multiple sclerosis experiencing vestibular impairment: a protocol for a pilot randomised controlled trial

INTRODUCTION

Vestibular system damage in patients with multiple sclerosis (MS) may have a central and/or peripheral origin. Subsequent vestibular impairments may contribute to dizziness, balance disorders and fatigue in this population. Vestibular rehabilitation targeting vestibular impairments may improve these symptoms. Furthermore, as a successful tool in neurological rehabilitation, immersive virtual reality (VRi) could also be implemented within a vestibular rehabilitation intervention.

METHODS AND ANALYSIS

This protocol describes a parallel-arm, pilot randomised controlled trial, with blinded assessments, in 30 patients with MS with vestibular impairment (Dizziness Handicap Inventory ≥16). The experimental group will receive a VRi vestibular rehabilitation intervention based on the conventional Cawthorne-Cooksey protocol; the control group will perform the conventional protocol. The duration of the intervention in both groups will be 7 weeks (20 sessions, 3 sessions/week). The primary outcomes are the feasibility and safety of the vestibular VRi intervention in patients with MS. Secondary outcome measures are dizziness symptoms, balance performance, fatigue and quality of life. Quantitative assessment will be carried out at baseline (T0), immediately after intervention (T1), and after a follow-up period of 3 and 6 months (T2 and T3). Additionally, in order to further examine the feasibility of the intervention, a qualitative assessment will be performed at T1.

ETHICS AND DISSEMINATION

The study was approved by the Andalusian Review Board and Ethics Committee, Virgen Macarena-Virgen del Rocio Hospitals (ID 2148-N-19, 25 March 2020). Informed consent will be collected from participants who wish to participate in the research. The results of this research will be disseminated by publication in peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

NCT04497025.

Immersive Virtual Reality and Vestibular Rehabilitation in Multiple Sclerosis: Case Report

Background

Dizziness and imbalance are common and disabling symptoms in patients with multiple sclerosis (MS) and are caused by a central, peripheral, or mixed vestibulopathy. Central vestibular disorder is the most frequently reported vestibular problem in the MS population due to demyelination. Vestibular rehabilitation ameliorates these symptoms and their repercussions and improves quality of life. Immersive virtual reality (VRi) is an emerging tool in this field; however, no previous research has been performed studying its effects in MS.

Objective

The aim of this study was to apply a VRi vestibular training protocol to a patient with MS and assess the effects induced by the experimental intervention.

Methods

This case study included a 54-year-old woman with relapsing-remitting MS. We developed a standardized VRi exercise protocol for vestibular rehabilitation based on the gold-standard Cawthorne-Cooksey vestibular training protocol. The 20-session intervention was made up of 10 initial sessions and 10 advanced sessions. Each 50-minute session was performed two to three times per week for 7 weeks. Four evaluations were carried out over the study period: at baseline (T0), between initial and advances phases (T1), postintervention (T2), and 1 month after the experimental procedure (T3). The research outcomes were dizziness, balance, gait, impact of fatigue, quality of life, repercussions in muscular tone, and usability of the head-mounted display device.

Results

After implementing the VRi vestibular protocol, improvements were seen in the following patient parameters: Dizziness Handicap Inventory score (62 points at T0; 4 points at T2); Berg Balance Scale score (47 points at T0; 54 points at T2); instrumented Timed Up and Go time (8.35 seconds at T0; 5.57 seconds at T2); muscular tone of the erector spinae, rectus femoris, and soleus; Modified Fatigue Impact Scale score (61 points at T0; 37 points at T2); and Multiple Sclerosis Quality of Life-54 values (67.16% in the physical health area at T2; 33.56% in the mental health area at T2). The patient rated the usability of the system as 90%, based on the System Usability Scale, and gave the system a grade of A.

Conclusions

Although further research is needed, this study provided initial evidence that the first VRi vestibular protocol for the MS population can improve dizziness, balance, gait, impact of fatigue, quality of life, and muscular tone through an exergame intervention. This study may help establish a standardized VRi protocol for vestibular rehabilitation.

The effect of visual field manipulations on standing balance control in people with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is associated with an increased risk of falls, degeneration of sensory organization, and possible increased reliance on vision for balance control.

RESEARCH QUESTION

The aim of this study was to assess differences in standing postural control between people with MS and age and sex matched controls during medial-lateral (ML) oscillations of the visual field, with and without blinders to the lower periphery.

METHODS

Ten persons with MS (mean age 54.0 ± 5.3 years) and ten age and sex matched controls (mean age: 56.3 ± 6.0 years) participated in this study. Balance control was assessed while participants stood in a Christie Cave system while wearing stereoscopic glasses that projected an immersive forest scene. Visual conditions consisted of 2 m ML visual oscillations of the scene at five frequencies (0.0, 0.3, 0.6, 0.7 and 0.8 Hz) with and without blinders to block the lower periphery.

RESULTS AND SIGNIFICANCE

The results demonstrated that, in comparison to controls, participants with MS had a significantly larger center of pressure sway in both the ML and AP direction to ML visual oscillations. Additionally, participants with MS and controls both increased center of pressure frequency content to the visual oscillation frequency, while participants with MS also increased relative power at the visual oscillation frequency in the AP direction. Blinders of lower periphery reduced the percent power at the visual oscillation frequency in both groups and reduced overall sway in participants with MS during visual oscillations. Overall, results indicate that postural balance is sensitive to visual feedback in people with MS. The elicited AP sway to ML visual oscillation could reflect errors in visual processing for the control of balance, and decreased sway in response to blocking vision of the lower peripheral field could indicate an increased reliance on visual cues to maintain balance.

Central Vestibular Functions Correlate With Fatigue and Walking Capacity in People With Multiple Sclerosis

OBJECTIVE

Imbalance and fatigue are among the most common and disabling symptoms of multiple sclerosis (MS). Vestibular rehabilitation studies demonstrate not only improvements in balance but fatigue also, suggesting a relationship between central vestibular integration and fatigue. The objective of this study was to determine whether the relationship between balance and fatigue in people with MS is seen between other measures of central vestibular integration and fatigue and to understand how central vestibular integration measures interrelate.

METHODS

This cross-sectional study consisted of 40 people with MS (age = 27-55 years, Expanded Disability Severity Scale score = 1.0-6.5) who completed vestibular ocular reflex testing, subjective visual vertical testing, static posturography, dynamic gait, 2 self-report fatigue surveys, and a 6-Minute Walk Test to assess walking capacity/physical fatigue was completed. Spearman correlations were calculated between variables.

RESULTS

Measures of central vestibular integration were significantly correlated with measures of fatigue and walking capacity and with each other. The correlations between physical fatigue and central vestibular functions were larger than self-reported fatigue correlations with central vestibular functions.

CONCLUSION

The relationship between balance and fatigue extends to other measures requiring central vestibular integration, suggesting a deficit in central vestibular processing in people with MS. These measures may compliment balance assessment as outcome measures for vestibular rehabilitation in people with MS. Fatigue measures should be included in vestibular rehabilitation as secondary outcomes.

IMPACT

Correlations between central vestibular integration and fatigue in people with MS suggest that future studies of vestibular rehabilitation should include fatigue, as a secondary outcome measure as vestibular function and fatigue may share similar a similar etiology in people with MS.

The effects of visual feedback disruption on postural control with chronic ankle instability

OBJECTIVES

The purpose of this study was to identify the effects of reduced visual feedback via stroboscopic glasses on dynamic postural control among chronic ankle instability (CAI), lateral ankle sprain (LAS) coper and uninjured control participants.

DESIGN

Controlled trial in a laboratory setting.

METHODS

Twenty CAI patients, 20 copers, and 20 controls participated in this study. Each participant performed a single-leg hop stabilization test with eyes open (EO) and stroboscopic vision (SV). Two-way ANOVAs (group × condition) were used to examine the differences between group (CAI, coper, and control) and condition (EO and SV).

RESULTS

There was a significant group by condition interaction for DPSI scores. CAI patients displayed increased DPSI scores with SV compared to EO (p < 0.01), and CAI patients had increased DPSI scores only with SV when compared with controls. All participants displayed decreased dynamic postural control under the SV condition compared to the EO condition (p < 0.01) regardless of ankle group.

CONCLUSIONS

CAI patients rely more on visual feedback during dynamic postural control than copers and controls. However, they may not be as able to compensate for the disrupted visual feedback during a dynamic task. Regardless of ankle injury history, stroboscopic glasses could be cost-effective visual disruption devices during a dynamic balance task.

Effects of dual-tasking on time-to-boundary during stance in people with PD: A preliminary study

BACKGROUND

Quiet stance is impacted by Parkinson's disease and dual-tasking. Recently developed outcomes such as the time-to-boundary provide unique insight into balance by integrating center of pressure position with base of support. However, little is known about the effects of Parkinson's disease on time-to-boundary. In particular, the effects of distracting cognitive tasks, and how people with Parkinson's disease prioritize balance and cognitive tasks are poorly understood.

METHODS

14 people with Parkinson's disease and 13 controls completed quiet standing and cognitive Stroop tasks separately (single-task) and together (dual-task). 2-dimentional, medio-lateral, and anterior-posterior time-to-boundary were calculated via force-plate data. Traditional sway outcomes, including sway area and path length, were also calculated. Cognitive performance was measured as the verbal reaction time after auditory stimulus delivery. Prioritization was assessed by taking the difference between cognitive and postural dual-task interference.

FINDINGS

Time-to-boundary was worse in Parkinson's disease compared to controls (2-dimentional: p = .019; anterior-posterior: p = .062; medio-lateral: p = .012). Medio-lateral time-to-boundary, but not anterior-posterior, was significantly worse during dual-tasking than single-tasking (p = .024). Neurotypical adults tended to prioritize cognition over medio-lateral postural outcomes.

INTERPRETATION

People with Parkinson's disease exhibit worse time-to-boundary than their neurotypical peers, and medio-lateral outcomes were sensitive to single to dual-task performance changes. Further, participants generally showed cognitive prioritization, such that cognitive performance was less impacted than medio-lateral postural outcomes by dual-tasking.

The functional reach test in people with multiple sclerosis: a reliability and validity study

Background: Limits of stability (LOS) is a major component of balance dysfunction in people with multiple sclerosis (MS). The functional reach test (FRT) is a clinical LOS assessment; however, its psychometric properties have not been investigated in people with MS yet. Objectives: To investigate: (1) the intrarater, interrater, and test-retest reliability of the FRT in people with MS; (2) the minimum detectable change (MDC) in the FRT distances; (3) the concurrent and discriminant validity of the FRT; and (4) the cutoff distance that best discriminates people with MS from healthy people and fallers from non-fallers with MS.Methods: Forty-three people with MS and 36 healthy people participated in this study. The FRT was administered along with the instrumented LOS test, Berg Balance Scale, Four Square Step Test, Timed Up and Go Test, and Expanded Disability Status Scale. The FRT was repeated by the same rater after 2 min from the first test session to determine the intrarater reliability and was simultaneously conducted by two independent raters to determine the interrater reliability. The FRT was also repeated after 7-10 days to determine the test-retest reliability. The reliability was quantified using intraclass correlation coefficients (ICC), Bland-Altman plots, and the MDC. The validity was assessed by correlating the FRT distances with the scores of other measures and by comparing the FRT distances between the MS group and healthy people, and between the fallers and non-fallers in the MS group.Results: The FRT demonstrated good to excellent intrarater, interrater, and test-retest reliability with an ICC (3,1) of 0.80-0.88 (p < .001), an ICC (3,2) of 0.94-0.97 (p < .001), an ICC (2,3) of 0.84-0.86 (p < .001), respectively. Bland-Altman analyses showed no systematic bias between the assessments. The MDC was 8.28 centimeters. The FRT was correlated with the other outcome measures (correlation coefficients ranged from 0.31 to 0.79, p < .05 for all). Significant differences in the FRT distances were found between people with MS and healthy people; however, no significant difference was found between the fallers and non-fallers with MS (p < .001 and p = .09, respectively). The cutoff distance of 35.5 centimeters best discriminates healthy people from people with MS while of 28.5 centimeters did not discriminate between the fallers and non-fallers with MS.Conclusions: The FRT is a reliable, valid, and easy-to-administer tool for assessing LOS in people with MS.

Gait Pattern in People with Multiple Sclerosis: A Systematic Review

The aim of the present systematic review was to describe the gait pattern in people with multiple sclerosis (MS) by compiling the main findings obtained from studies using three-dimensional capture systems of human movement. The search was carried out in PubMed, Web of Science, Physiotherapy Evidence Database (PEDro), and the Cumulative Index to Nursing and Allied Health (CINAHL) databases. Studies that used three-dimensional gait analysis systems and that analyzed spatiotemporal, kinematic, kinetic, or electromyographic parameters, were included. The quality of the studies was assessed using the Critical Review Form-Quantitative Studies scale. 12 articles were included with 523 (342 women and 181 men) people with a diagnosis of MS. The present work suggests that people with MS have a decrease in speed and stride length, as well as an increase in double-stance intervals during gait. Likewise, it is common to observe a decrease in hip extension during the stance period, a decrease in knee flexion in the swing period, a decrease in ankle dorsiflexion in the initial contact and a decrease in ankle plantar flexion during the pre-swing phase. The subjects with MS decrease the hip extensor moment and the ankle power during the stance period of walking.

Non-invasive brain stimulation to assess neurophysiologic underpinnings of lower limb motor impairment in multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a neuroinflammatory disease resulting in axonal demyelination and an amalgamation of symptoms which commonly result in decreased quality of life due to mobility dysfunction and limited participation in meaningful activities.

NEW METHOD

The use of non-invasive brain stimulation (NIBS) techniques, specifically transcranial magnetic and transcranial direct current stimulation, have been essential in understanding the pathophysiological decrements related to disease progression, particularly with regard to motor impairments. Although the research in this area has primarily focused on the upper extremities, new interest has arisen in understanding the neurophysiological underpinnings of lower limb impairment. Therefore, the purpose of this review is to: first, provide an overview of common NIBS techniques used to explore sensorimotor neurophysiology; second, summarize lower limb neuromuscular and mobility impairments typically observed in PwMS; third, review the current knowledge regarding interactions between TMS-assessed neurophysiology and lower limb impairments in PwMS; and fourth, provide recommendations for future NIBS studies based on current gaps in the literature.

RESULTS

PwMS exhibit reduced excitability and increased inhibitory neurophysiologic function which has been related to disease severity and lower limb motor impairments. Comparison with existing methods: Moreover, promising results indicate that the use of repetitive stimulation and transcranial direct current stimulation may prime neural adaptability and prove useful as a therapeutic tool in ameliorating lower limb impairments.

CONCLUSIONS

While these studies are both informative and promising, additional studies are necessary to be conclusive. As such, studies assessing objective measures of lower limb impairments associated with neurophysiological adaptations need further evaluation.

Are fatigue scales the same? A content comparison using the International Classification of Functioning, Disability and Health

BACKGROUND

Fatigue is a common impairment in a wide range of disorders. Numerous fatigue scales have been designed in an attempt to quantify this impairment without any clear distinction between them. The International Classification of Functioning, Disability and Health (ICF) is a useful tool for content comparison of measurement scales.

OBJECTIVE

To explore the content of generic fatigue scales using the ICF.

METHODS

Twenty generic fatigue scales were identified and linked to the ICF by two health care professionals according to the established linking rules. The contents of the 20 scales were compared and the inter-rater agreement was estimated using kappa coefficients.

RESULTS

The content of generic fatigue scales varies and was found to focus mostly on body functions, activities and participation components of the ICF with a moderate to high degree of inter-observer agreement.

CONCLUSIONS

The content comparison of fatigue questionnaires would assist clinicians and researchers in selecting the most appropriate measurement for use and precisely analyze the results of these measurements.

Postural control quantification in minimally and moderately impaired persons with multiple sclerosis: The reliability of a posturographic test and its relationships with functional ability

BACKGROUND

Postural control has been associated with the functional impairment in persons with multiple sclerosis (pwMS). However, there is a need for reliable methods to assess postural control in early stages of the disease, when subtle changes can be difficult to detect. The aims of this study were to assess the absolute and relative reliability of a standing and a sitting posturographic protocol in minimally (Expanded Disability Status Scale ≤ 2) and moderately (2.5 ≤ Expanded Disability Status Scale ≤ 4) impaired pwMS, and to analyze relationships among postural control and functional mobility and gait performance.

METHODS

To assess postural control in an upright stance, 14 minimally and 16 moderately impaired pwMS performed six 70 s trials in tandem stance, 3 with their weaker leg behind (TS_WL) and 3 with their stronger leg behind (TS_SL). Additionally, participants completed five 70 s trials using an unstable sitting protocol (US) to assess trunk stability. The mean radial errors of TS_WL, TS_SL, and US trials were calculated as postural control indexes. Furthermore, participants performed the Timed Up and Go test (TUG) and the Timed 25-foot Walk test (T25FW) to measure their functional mobility and gait speed, respectively. Reliability was evaluated using the intraclass correlation coefficient (ICC_3,1) and the standard error of measurement (SEM). Analyses of variances were carried out to assess between-group differences. Hedges' g index (d_g) was used to estimate the effect size of differences. Pearson correlation analyses (r) were performed to examine the relationships among the postural control and the functional tests.

RESULTS

Posturographic tests showed a high reliability in both minimally (0.87 ≤ ICC ≤ 0.92; 9.32% ≤ SEM ≤ 11.76%) and moderately (0.80 ≤ ICC ≤ 0.92; 10.33% ≤ SEM ≤ 15.33%) impaired pwMS. Similarly, T25FW and TUG displayed a high consistency in minimally (0.89 ≤ ICC ≤ 0.94; 3.43% ≤ SEM ≤ 5.17%) and moderately (0.85 ≤ ICC ≤ 0.93; 5.57% ≤ SEM ≤ 6.56%) impaired individuals. Minimally impaired pwMS showed a better performance on the TUG, T25FW, and TS_WL than moderately impaired individuals (p < 0.05; d_g ≥ 0.8). The TS_WL, TS_SL, and US variables correlated with TUG scores (0.419 ≤ r ≤ 0.604; p < 0.05), but TS_WL also correlated with T25FW scores (r = 0.53; p < 0.01). Furthermore, US scores correlated with both tandem stance parameters (TS_WL: r = 0.54, p < 0.01; TS_SL: r = 0.43, p < 0.05).

CONCLUSION

Tandem and sitting posturographic tests provide reliable measures of postural control in pwMS, even in individuals with a homogeneous disease profile. Gait speed, functional mobility, and weaker leg status seem decisive in assessing the degree of physical activity limitation in pwMS. Finally, although trunk stability does not seem to be so affected by the course of the disease, it remains relevant for postural control and functional capacity.

Reference Values for Isometric, Dynamic, and Asymmetry Leg Extension Strength in Patients with Multiple Sclerosis

Having recognized the value of resistance training in patients with multiple sclerosis (PwMS), there are a lack of lower limb normative reference values for one repetition maximum (1RM) and maximal voluntary isometric contraction (MVIC) in this population. Hence, the purposes of this study were to provide reference values for 1RM and MVIC of knee extensors in PwMS across the disability spectrum and to examine knee extension strength asymmetry. Three hundred and ninety PwMS participated in the study, performing MVIC and 1RM tests of bilateral (both legs together at once) and unilateral (each leg singly) knee extensors. There was no difference in 1RM according to the disease course of MS, but there was according to the degree of neurological disability, being more preserved in those with a lower degree of disability. MVIC tends to be higher in patients with relapsing-remitting MS respect those with progressive MS, and in patients with lower levels of neurological disability. Asymmetry above the values considered normal in 1RM was present in 20-60% of patients and 56-79% in the MVIC test, depending on the type of MS and tended to be lower in those with less disability. Reference values are given by quartiles for 1RM, MVIC, and asymmetry.

Neuromuscular and Mobility Responses to a Vibration Session in Hypoxia in Multiple Sclerosis

The aim of this study was to investigate the acute effects of vibration training (WBVT) under hypoxic and normoxic conditions on the voluntary rate of force development (RFD), balance and muscle oxygen saturation (SMO₂) in persons with Multiple Sclerosis (MS). 10 participants completed the study (30% males, 44.4±7.7 years, 164.3±8.9 cm, 65.2±11.1 kg, 2.5±1.3 Expanded Disability Status Scale, 24.1±4.0 kg.m^-2 BMI). Maximal force, RFD during isometric knee extension, static balance with eyes open and closed and sit-to-stand test were evaluated before and immediately after one session of WBVT (12 60-s bout of vibration; frequency 35 Hz; amplitude 4 mm; 1-min rest intervals) under both normoxic and hypoxic conditions. In addition, SMO₂ of the gastrocnemius lateralis was assessed during each condition. No changes were found in force, static balance and sit-to-stand test. Time-to-peak RFD increased in the left leg (p=0.02) and tended to increase in the right leg (p=0.06) after the hypoxic session. SMO₂ resulted in significant increases from the initial to final intervals of the WBVT under both hypoxic and normoxic conditions (p<0.05). Increases in SMO₂ during WBVT demonstrates muscle work that may contribute to the observed muscle adaptations in long-term WBVT programs without inducing decreases in neuromuscular activation, physical function and balance within a session.

Sensorimotor function in progressive multiple sclerosis

BACKGROUND

A sensitive test reflecting subtle sensorimotor changes throughout disease progression independent of mobility impairment is currently lacking in progressive multiple sclerosis.

OBJECTIVES

We examined non-ambulatory measures of upper and lower extremity sensorimotor function that may reveal differences between relapsing-remitting and progressive forms of multiple sclerosis.

METHODS

Cutaneous sensitivity, proprioception, central motor function and mobility were assessed in 32 relapsing-remitting and 31 progressive multiple sclerosis patients and 30 non-multiple sclerosis controls.

RESULTS

Cutaneous sensation differed between relapsing-remitting and progressive multiple sclerosis at the foot and to a lesser extent the hand. Proprioception function in the upper but not the lower extremity differed between relapsing-remitting and progressive multiple sclerosis, but was different for both upper and lower extremities between multiple sclerosis patients and non-multiple sclerosis controls. Foot-tap but not hand-tap speed was slower in progressive compared to relapsing-remitting multiple sclerosis, suggestive of greater central motor function impairment in the lower extremity in progressive multiple sclerosis. In addition, the non-ambulatory sensorimotor measures were more sensitive in detecting differences between relapsing-remitting and progressive multiple sclerosis than mobility assessed with the 25-foot walk test.

CONCLUSION

This study provides novel information about changes in sensorimotor function in progressive compared with relapsing-remitting forms of multiple sclerosis, and in particular the importance of assessing both upper and lower extremity function. Importantly, our findings showed loss of proprioceptive function in multiple sclerosis but also in progressive compared to relapsing-remitting multiple sclerosis.

Can optical flow perturbations detect walking balance impairment in people with multiple sclerosis?

People with multiple sclerosis (PwMS) who exhibit minimal to no disability are still over twice as likely to fall as the general population and many of these falls occur during walking. There is a need for more effective ways to detect preclinical walking balance deficits in PwMS. Therefore, the purpose of this study was to investigate the effects of optical flow perturbations applied using virtual reality on walking balance in PwMS compared to age-matched controls. We hypothesized that susceptibility to perturbations–especially those in the mediolateral direction–would be larger in PwMS compared to controls. Fourteen PwMS and fourteen age-matched controls walked on a treadmill while viewing a virtual hallway with and without optical flow perturbations in the mediolateral or anterior-posterior directions. We quantified foot placement kinematics, gait variability, lateral margin of stability and, in a separate session, performance on the standing sensory organization test (SOT). We found only modest differences between groups during normal, unperturbed walking. These differences were larger and more pervasive in the presence of mediolateral perturbations, evidenced by higher variability in step width, sacrum position, and margin of stability at heel-strike in PwMS than controls. PwMS also performed worse than controls on the SOT, and there was a modest correlation between step width variability during perturbed gait and SOT visual score. In conclusion, mediolateral optical flow perturbations revealed differences in walking balance in PwMS that went undetected during normal, unperturbed walking. Targeting this difference may be a promising approach to more effectively detect preclinical walking balance deficits in PwMS.

Effectiveness of Vestibular Training for Balance and Dizziness Rehabilitation in People with Multiple Sclerosis: A Systematic Review and Meta-Analysis

Postural instability and dizziness are commonly observed in people with multiple sclerosis (PwMS). The aim of this systematic review was to evaluate the evidence for the use of vestibular rehabilitation, in comparison with other exercise interventions or no intervention, to treat balance impairments and dizziness in PwMS. An electronic search was conducted by two independent reviewers in the following databases: MEDLINE (Pubmed), Scopus, the Physiotherapy Evidence Database (PEDro), Web of Science (WOS), Lilacs, CINHAL and the Cochrane Database of Systematic Reviews (CDSR). A quality assessment was performed using the PEDro scale and the Cochrane Risk of Bias Tool. When possible, the data were pooled in a meta-analysis (95%CI). This systematic review followed the PRISMA guideline statement and was registered in the PROSPERO database (CRD42019134230). Seven studies were included, with a total of 321 participants analysed. Compared with no intervention, vestibular rehabilitation was more effective for balance development (SMD = 2.12; 95% CI = 0.49, 3.75; p = 0.01; I² = 89%) and dizziness symptoms improvement (SMD = −17.43; 95% CI = −29.99, −4.87; p= 0.007; I²= 66%). Compared with other exercise interventions, improvements in favour of the experimental group were observed, but statistical significance for the differences between groups was not reached.

Relative importance of vision and proprioception in maintaining standing balance in people with multiple sclerosis

BACKGROUND

Balance impairment is common and a risk factor of falls in people with multiple sclerosis (MS). The purpose of this study was to evaluate the relative importance between vision and proprioception in maintaining standing body balance among individuals with MS compared with healthy individuals.

METHODS

Thirty people with MS (the mean ± standard deviation of the Patient Determined Disability Steps: 3.62 ± 1.67 out of 8) and 25 healthy adults participated in this cross-sectional study. They underwent a static posturography test, consisting of three sensory feedback conditions: eyes open on a firm surface, eyes closed on a firm surface, and eyes open on a compliant surface. Their standing balance performance, quantified by the 95% confidence ellipse area and the total length of the center of pressure trajectory during each sensory condition, was calculated based on the ground reaction force data. The Romberg's quotient (the ratio of the center of pressure measurements on the firm surface between eyes open and eyes closed conditions) and proprioception quotient (the ratio of the center of pressure measurements with eyes open between firm and compliant standing surfaces) were calculated and compared between groups.

RESULTS

Persons with MS demonstrated significantly larger postural sway under all three sensory conditions than their healthy counterparts. The reliance on the vision and proprioception systems in maintaining body balance was greater among people with MS compared to healthy adults. Both groups similarly relied more on the proprioceptive input to keep body balance than on the vision.

CONCLUSIONS

Like healthy individuals, persons with MS rely more on proprioception to maintain body balance than vision. Our findings could provide preliminary reference for optimizing balance improving programs aimed at person with MS.

The Effect of Holding an Object on Postural Stability and Suprapostural Task Performance

Holding an object has been found to reduce postural sway during quiet standing. However, people normally stand to accomplish suprapostural goals, such as fitting a key into a lock. Postural control should therefore be assessed by examining postural outcomes in the context of suprapostural task performance. This study assessed whether holding an object increased standing postural stability and improved the performance of a concurrent precision manual task. A total of 15 young adults performed a precision manual task with their dominant hand while holding or not holding an object in their nondominant hand. Postural stability was assessed using measures of postural sway and time to boundary. Suprapostural task performance was assessed as an error count. Holding did not influence postural sway or suprapostural task performance. Discrepancies among previous studies coupled with the present findings suggest that the effects of holding an object on standing posture are highly sensitive to the experimental context. The authors provide several explanations for their findings and discuss the limitations of previous suggestions that holding an object may have clinical relevance for balance-compromised populations.

Postural Control Underlying Head Movements While Tracking Visual Targets

The aim of this study was to investigate the relationship between postural regulation and tracking accuracy under static and moving visual target conditions in unipedal and bipedal standing postures. Postural time-to-contact stability boundaries decreased under more challenging visual target conditions for the unipedal posture, but this decrease was associated with lower visual tracking error. During bipedal support, there was independent control of the head and foot center of pressure, as higher frequencies at the head during the static visual task were associated with longer time-to-contact. These results demonstrate that decreased time-to-contact stability boundaries is a functional adaptation in postural tasks requiring visual control and provide evidence of the dependency of postural control on the nature of the suprapostural task.

Altered visual and somatosensory feedback affects gait stability in persons with multiple sclerosis

Persons with multiple sclerosis (PwMS) often report problems due to sensory loss and have an inability to appropriately reweight sensory information. Both of these issues can affect individual's ability to maintain stability when walking under challenging conditions. The purpose of the current study was to determine how gait stability is adapted when walking under challenging sensory conditions where vision and somatosensation at the feet is manipulated. 25 healthy adults and 40 PwMS (15 fallers, 25 non-fallers) walked on a treadmill at their preferred normal walking speed under 3 conditions: normal walking, altered vision using goggles that shifted visual field laterally, and altered somatosensation using shoes with compliant foam soles. Inertial measurement united recorded acceleration at the lumbar and right ankle, and acceleration variability measures were calculated including root mean square (RMS), range, sample entropy (SaEn), and Lyapunov exponents (LyE). A gait stability index (GSI) was calculated using each of the four variability measures as the ratio of lumbar acceleration variability divided by foot acceleration variability in the frontal and sagittal planes. The sagittal and frontal GSI_RMS were larger in the somatosensory condition compared to the normal and visual conditions (p < 0.001). The frontal GSI_SaEn was greater in the visual condition compared to the somatosensory condition (p = 0.021). The frontal and sagittal GSI_LyE was greater in the somatosensory condition compared to the normal and visual conditions (p < 0.002). The current study showed that HC, MS non-fallers and MS fallers largely adapted to altered sensory feedback during walking in a similar manner. However, MS faller subjects may be more reliant on visual feedback compared to MS non-fallers and HC subjects.

Validating Virtual Time to Contact With Home Based Technology in Young and Older Adults

Virtual time to contact (VTC) is a measure of postural stability that estimates the virtual time it would take to reach an individual's stability boundary. This study aimed to validate VTC as measured by a depth sensor, and to determine if VTC from the depth sensor distinguishes between older adult fallers and non-fallers compared to a force platform. VTC was assessed in 10 young and 20 older adults by having participants lean in a circular direction followed by five balance tests: eyes open, dual task, eyes open foam, eyes closed, and eyes closed foam. Spearman's correlations and Bland-Altman plots were conducted to determine validity, and Receiver Operating Curves were constructed to discriminate between fallers and non-fallers. Significant correlations were found in the dual task (p = 0.03), eyes open foam (p < 0.01), and eyes closed foam conditions (p = 0.05). The depth sensor discriminated between fallers and non-fallers in the eyes open (p = 0.02), dual task (p = 0.03), and eyes open foam conditions (p = 0.04). VTC was in agreement between the two devices, and VTC derived from a depth sensor and may be used to discriminate between older adult fallers and non-fallers during challenging balance conditions.

Effects of External Perturbations on Anticipatory and Compensatory Postural Adjustments in Patients with Multiple Sclerosis and a Fall History

Background

Although previous studies have investigated postural adjustment mechanisms in patients with multiple sclerosis (MS), it seems that no study has yet investigated the relationship between anticipatory and compensatory postural adjustments (APAs and CPAs, respectively) and falls.

Methods

Seventeen MS fallers, 17 MS nonfallers, and 15 controls were exposed to a series of expected and unexpected backward pull perturbations applied at the trunk level. The electrical activity of 12 leg and trunk muscles as well as center of pressure displacement were recorded.

Results

The MS fallers had delayed muscle activity onsets compared with MS nonfallers and controls. In addition, a significantly lower level of muscle activity during APAs was detected in MS fallers compared with controls. Moreover, in the unexpected condition of perturbation, significantly smaller CPA was observed in MS fallers compared with controls. Both groups of patients with MS required more time to stabilize their center of pressure after both types of perturbations compared with controls.

Conclusions

The inability to produce efficient APAs and CPAs during perturbations may explain the high rates of postural instability and falls in patients with MS. Findings from this study provide a background for the development of perturbation-based training programs aimed at balance improvement and fall prevention by restoring mechanisms underlying balance impairments.

Effects of Muscle Function and Limb Loading Asymmetries on Gait and Balance in People With Multiple Sclerosis

People with MS (PwMS) often have a more- and less-affected side of the body which results in a variety of asymmetries, including measures of power, strength, muscle activity, and limb loading. Though many studies have identified asymmetries, their impact on gait and balance in PwMS is currently unclear. In this mini-review we first summarize previous findings of asymmetries in muscle function and limb loading and their impact on gait and balance in PwMS. We then provide potential explanations for this lack of consistency in the current literature, and propose study guidelines to improve future lower limb asymmetry studies. Making use of a unified approach to study lower limb asymmetry may then provide more clarity regarding their impact on mobility, specifically gait and balance, in PwMS.

Postural control deficits in people with Multiple Sclerosis: A systematic review and meta-analysis

BACKGROUND

Multiple sclerosis (MS) is a neurological condition that can affect the postural stability of the individual and predispose falls in this population.

METHODS

A systematic literature search identified case-control studies investigating differences in postural control across a diversity of task conditions, with the exception of gait, between people with MS and healthy controls. Meta-analysis was conducted where a variable was presented by four or more studies.

RESULTS

Forty-three studies of people with a mean Expanded Disability Status Scale (EDSS) of 1.0 to 6.0 were included. Seven conditions of assessment and 105 individual measurement variables relating to postural control were included. Quiet stance was the only condition (11 studies) possessing sufficient data to contribute to meta-analysis in terms of centre of pressure path length (SMD = 1.04, 95% CI {0.86-1.22}, p < 0.001), medio-lateral velocity (SMD = 1.35, 95% CI {0.77-1.92}, p < 0.001) and 95% confidence ellipse (SMD = 0.83 95% CI {0.59-1.08}, p < 0.001).

RESULTS

indicate that regardless of task complexity or sensory condition, people with MS display considerable deficits in postural control in comparison to healthy controls.

CONCLUSIONS

The large number of variables and lack of standardisation of reporting makes data synthesis challenging, however, people with MS display considerable deficits in postural control compared to healthy controls regardless of task condition or complexity.

Coherence analysis of trunk and leg acceleration reveals altered postural sway strategy during standing in persons with multiple sclerosis

Balance task performance is affected in persons with multiple sclerosis (PwMS), but the control strategies used to perform specific tasks are not well understood. The purpose of this study was to evaluate segmental control during quiet standing in PwMS and controls to understand whether MS alters use of the ankle and hip strategies to manage postural sway. Coherence of acceleration between the trunk and legs was evaluated with accelerometers placed on the sacrum and lower leg. Thirty-six PwMS and 20 healthy control subjects performed quiet standing with eyes open and closed while center of pressure (CoP) and acceleration of postural sway was measured. Acceleration frequencies were divided into lower frequencies (≤1.0 Hz) and higher frequencies (>1.0 Hz) to categorize sway characteristics. With eyes open, coherence was significantly lower in PwMS compared to controls at lower frequencies only. With eyes closed, coherence was significantly lower in PwMS compared to controls, who use an ankle strategy at lower frequencies only, at both lower and higher frequencies. Both groups showed decreased coherence with increasing frequency when eyes were open and closed. Coherence was significantly correlated with CoP sway area in PwMS during the eyes closed condition only. The reduced coherence in PwMS during both lower and higher frequency sway indicates PwMS utilize a mixed ankle-hip sway strategy regardless of sway frequency. This is in contrast to sway in healthy subjects which utilizes an ankle strategy at lower frequencies and a mixed strategy at higher frequencies. Lack of adaptability in segmental control strategy likely contributes to abnormal postural control, as reflected by CoP sway patterns, in PwMS.

Post-fatigue recovery of power, postural control and physical function in older women

Low muscle power, particularly at high velocities, has been linked to poor physical function in older adults. Any loss in muscle power following fatiguing exercise or daily activities could impact physical function and postural control until power has fully recovered. To test the overall hypothesis that a common task such as walking can result in prolonged power loss and decreased physical function and balance, 17 healthy older (66–81 years) women completed a 32-min walking test (32MWT) designed to induce neuromuscular fatigue, followed by 60min of recovery (60R). Fatigue and recovery of knee extensor muscle power (3 velocities) were quantified by dynamometry. Function was quantified by chair rise time and postural control by measures of center of pressure (COP) range (mm) and velocity (mm·s^-1) during quiet stance. Power declined at all velocities by 8–13% 2min following the 32MWT (p≤0.02) and remained depressed by 8–26% at 60R (p≤0.04). Postural control decreased following the 32MWT, indicated by increased COP range in the anterior-posterior (AP, p<0.01) direction and a trend in the medial-lateral (ML) direction (p = 0.09), and returned to baseline by 60R (p≥0.10). COP velocity was unchanged immediately following the 32MWT, but at 60R was lower in ML (p = 0.03) and tended to be reduced in AP (p = 0.07). Changes in high-velocity power (270°·s^-1) were associated with altered postural control (p = 0.02) and chair rise performance (p≤0.03). These results provide evidence of long-duration neuromuscular changes following fatigue in healthy older women that may place them at increased risk for functional deficits during everyday mobility tasks.

DNA damage and postural balance in multiple sclerosis patients

Abstract Introduction: Multiple Sclerosis (MS) is a chronic inflammatory disease characterized by infiltration of inflammatory cells on the Central Nervous System (CNS). There is evidence that cumulative DNA damage can contribute to various mechanisms underlying MS lesions. Changes in postural balance are frequent observations in subjects with MS. Objective: Evaluated the DNA damage index (DDI)) and postural balance in patients with MS. Methods: A case-control study was conducted with 28 subjects matched for sex, age, and body mass index, divided into MS group and control. The DDI was assessed by comet assay and postural balance through recording the body oscillations of the center of pressure (COP), in the anterior-posterior and lateral middle directions. Results: Showed higher DDI in MS patients (21.3 ± 4.8) than controls (7.9 ± 6.1). Significant differences between groups were also noted in postural control parameters. The wider ranges of postural sway were observed in the MS group. The associations between DDI and postural control parameters showed weak, but significant correlations. No associations were found between DDI and time of diagnosis of MS. Conclusion: People with MS had higher DDI and larger body oscillations than healthy individuals.

Multiscale entropy: A tool for understanding the complexity of postural control

Clinical disorders often are characterized by a breakdown in dynamical processes that contribute to the control of upright standing. Disruption to a large number of physiological processes operating at different time scales can lead to alterations in postural center of pressure (CoP) fluctuations. Multiscale entropy (MSE) has been used to identify differences in fluctuations of postural CoP time series between groups with and without known physiological impairments at multiple time scales. The purpose of this paper is to: 1) review basic elements and current developments in entropy techniques used to assess physiological complexity; and 2) identify how MSE can provide insights into the complexity of physiological systems operating at multiple time scales that underlie the control of posture. We review and synthesize evidence from the literature providing support for MSE as a valuable tool to evaluate the breakdown in the physiological processes that accompany changes due to aging and disease in postural control. This evidence emerges from observed lower MSE values in individuals with multiple sclerosis, idiopathic scoliosis, and in older individuals with sensory impairments. Finally, we suggest some future applications of MSE that will allow for further insight into how physiological deficits impact the complexity of postural fluctuations; this information may improve the development and evaluation of new therapeutic interventions.

Multiscale entropy identifies differences in complexity in postural control in women with multiple sclerosis

Loss of postural center-of-pressure complexity (COP complexity) has been associated with reduced adaptability that accompanies disease and aging. The aim of this study was to identify if COP complexity is reduced: (1) in those with Multiple Sclerosis (MS) compared to controls; (2) when vision is limited compared to remaining intact; and (3) during more demanding postural conditions compared to quiet standing. Additionally, we explored the relationship between the COP complexity and disease severity, fatigue, cutaneous sensation and central motor drive. Twelve women with MS and 12 age-matched controls were tested under quiet standing and postural maximal lean conditions with normal and limited vision. The key dependent variable was the complexity index (CI) of the center of pressure. We observed a lower CI in the MS group compared to controls in both anterior-posterior (AP) and medio-lateral (ML) directions (p's<0.002), during the performance of maximal self-regulated leans (AP: p<0.001; ML: p=0.018), and under limited vision (AP: p=0.001; ML: p=0.006). No group-by-vision interaction (p>0.05) was observed, indicating that limiting vision did not impact COP complexity differently in the two groups. Decreased cutaneous sensitivity was associated with lower CI values in the AP direction among those with MS (r(2)=0.57); all other measures did not exhibit significant relationships. The findings reported here suggest that (1) MS is associated with diminished COP complexity under both normal and challenging postures, and (2) complexity is strongly correlated with cutaneous sensitivity, suggesting the unique contribution of impaired somatosensation on postural control deficits in persons with MS.