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

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.

Are trunk stability and endurance determinant factors for whole-body dynamic balance in physically active young males? A multidimensional analysis

OBJECTIVES

Determine if (a) a better trunk stability and endurance are associated with an improved whole-body dynamic balance, and if (b) the assessment tests can be interchanged within each capability.

METHODS

Sixty-three physically active young males performed three trunk stability (i.e., the lumbopelvic stability, the unstable sitting and the sudden loading sitting tests), three trunk muscle endurance (i.e., the Biering-Sørensen, the side bridge and the front bridge tests) and four whole-body dynamic balance (i.e., the tandem and the single-leg stance, the Y-Balance, and the single-leg triple hop tests) tests two times. After assessing the reliability of the variables, a Pearson correlation analysis was performed.

RESULTS

The correlations between trunk stability and endurance tests with dynamic balance tests were non-significant except for the unstable sitting test with both the tandem (r = 0.502) and the single-leg stance (r = 0.522) tests. Moreover, no relationships were observed between the trunk stability and the trunk muscle endurance tests. Interestingly, no relationships were found between most tests within each capability (i.e., trunk stability, trunk endurance, and dynamic balance) except: (i) the front bridge stability test and the back (r = 0.461) and the side (r = 0.499) bridge stability tests; (ii) the two side bridge endurance tests (r = 0.786); (iii) the tandem and the single-leg stance tests (0.439 ≤ r ≤ 0.463); (iv) the Y-Balance and the single-leg triple hop tests (0.446 ≤ r ≤ 0.477).

CONCLUSION

Better trunk function does not seem to be a relevant factor for dynamic balance in young active males. In this population, specific measures are needed as the test interchangeability is questioned.

Impact of textured surfaces on the orthostatic balance of patients with multiple sclerosis

OBJECTIVE

To perform posturographic measurements with eyes open or closed using floor coverings with different textured surfaces to study postural control in patients with multiple sclerosis (MS).

METHODS

Static posturographic recordings were performed with eyes open and eyes closed on a forceplate with no covering (control condition) or covered by a textured mat with small pimples (height 2 mm) or large pimples (height 7 mm). Several posturographic variables were measured, focusing on displacements of the center of pressure (CoP) including the average velocity (Vav), the total length (L) of all displacements, and the surface (S) of the confidence ellipse. The recordings made with the textured mats were compared to the control condition with eyes open or closed. Then, the differences between the recordings made with large vs. small pimples on the one hand, and with eyes closed vs. open were calculated to assess the impact of pimple height or eye closure on posturographic measurements. Clinical assessment was based on the Expanded Disability Status Scale (EDSS) and its functional system (FS) subscores, the Modified Fatigue Impact Scale (MFIS), the Unipodal Stance test (UST), and the Timed Up-and-Go test (TUG).

RESULTS

Forty-six MS patients (mean EDSS score: 3.6) completed the study. Several posturographic variables, including Vav and L, deteriorated when measured on a textured mat, especially with large pimples and in eyes open condition. In contrast, no difference was found with small pimples and eyes closed, as compared to the control condition (no covering). The deleterious impact of pimple height on posturography correlated positively with the alteration of balance and gait clinically assessed by the UST and the TUG, and also with the MFIS physical and cerebral EDSS-FS subscores, and negatively with the cerebellar and brainstem subscores. On the other hand, the impact of eye closure on posturography was negatively correlated with the visual EDSS-FS subscore.

DISCUSSION

Static posturographic measurements made with different textured surfaces and visual conditions can be considered as a sensitive tool to measure "proprioceptive reserves". Actually, when cerebellar, brainstem, or visual functions are impaired, the resources of the sensory (proprioceptive) system, if preserved, can be recruited at a higher level and compensate for dysfunctions of other postural controls to maintain a satisfactory balance. In addition, this procedure of static posturographic examination can provide objective measurements correlated with clinical testing of balance and gait and could usefully complement EDSS scoring to assess disability affecting postural control and the risk of falling in MS patients.

Protocol for Forearm Pronosupination Strength Measuring in Different Postures: Reliability and Influence of Relevant Factors

IMPORTANCE

Despite the importance of pronosupination strength, which is key in daily activities, current evaluation protocols are disparate, and results differ regarding the influence of factors such as gender, age, limb dominance, or posture.

OBJECTIVE

To design a reliable device to measure pronation and supination torques in different forearm positions, considering the influence of gender, age, and limb dominance.

DESIGN

Reliability study with analysis of intrarater and interrater repeatability and examination of the influence of different factors on the strength of pronation and supination.

SETTING

Biomechanical analysis laboratory of the Instituto de Biomecánica de Valencia.

PARTICIPANTS

Convenience sample of 39 healthy male and female participants, ages 18 to 65 yr.

OUTCOMES AND MEASURES

Pronation strength and supination strength were studied in five forearm positions: 30° and 60° of supination, neutral rotation, and 30° and 60° of pronation. The influence of gender, age, and limb dominance was studied using repeated-measures analysis of variance. Intrarater and interrater reliabilities were studied in 17 participants, and the intraclass correlation coefficients (ICCs) were calculated from three measurement sessions.

RESULTS

Except for 60° of pronation, all ICCs ranged from .72 to .97. Gender, limb dominance, and posture significantly affected pronosupination strength (p < .05), with the highest supination strength at 60° of pronation and the highest pronation strength at 60° of supination.

CONCLUSIONS AND RELEVANCE

In using this reliable pronosupination torque assessment device and standardized protocol in the clinical setting, clinicians must consider the influence of gender, limb dominance, and forearm posture. What This Article Adds: The results of this study will allow occupational therapists to establish differences between patients' functionality in comparison with healthy individuals and to design recovery treatments and facilitate performance of manual tasks, considering which are the most advantageous positions to exert force. Furthermore, the developed device can be used to monitor the evolution of these torques in an objective and reliable manner.

George L, Nankervis K, Sinclair J, Penhorwood G, Williams J, Clayton HM. Towards an Evidence-Based Classification System for Para Dressage: Associations between Impairment and Performance Measures

This study follows a previously defined framework to investigate the impact of impairment on performance in Para dressage athletes. Twenty-one elite Para dressage athletes (grades I to V) and eleven non-disabled dressage athletes (competing at Prix St. Georges or Grand Prix) participated. Data were collected in two phases: performing a two minute custom dressage test on a riding simulator while kinematic data were synchronously collected using inertial measurement units (2000 Hz) and optical motion capture (100 Hz), and clinically assessed using a battery of impairment assessment tools administered by qualified therapists. Impairment and performance measures were compared between Para and non-disabled athletes. Significant differences between athlete groups were found for all impairment measures and two performance measures: simulator trunk harmonics (p = 0.027) and athlete trunk dynamic symmetry (p < 0.001). Impairment assessments of sitting function and muscle tone could predict 19 to 35% of the impact of impairment on performance in Para athletes but not in non-disabled athletes. These findings provide the basis for a robust, scientific evidence base, which can be used to aid in the refinement of the current classification system for Para dressage, to ensure that it is in line with the International Paralympic Committee's mandate for evidence-based systems of classification.

The Relationship Between Imbalance Symptom and Cardiac Pulsation Induced Mechanical Strain in the Brainstem and Cerebellum for Chiari Malformation Type I

Chiari malformation Type I (CMI) is known to have an altered biomechanical environment for the brainstem and cerebellum; however, it is unclear whether these altered biomechanics play a role in the development of CMI symptoms. We hypothesized that CMI subjects have a higher cardiac-induced strain in specific neurological tracts pertaining to balance, and postural control. We measured displacement over the cardiac cycle using displacement encoding with stimulated echoes magnetic resonance imaging in the cerebellum, brainstem, and spinal cord in 37 CMI subjects and 25 controls. Based on these measurements, we computed strain, translation, and rotation in tracts related to balance. The global strain on all tracts was small (<1%) for CMI subject and controls. Strain was found to be nearly doubled in three tracts for CMI subjects compared to controls (p < 0.03). The maximum translation and rotation were ∼150 μm and ∼1 deg, respectively and 1.5-2 times greater in CMI compared to controls in four tracts (p < 0.005). There was no significant difference between strain, translation, and rotation on the analyzed tracts in CMI subjects with imbalance compared to those without imbalance. A moderate correlation was found between cerebellar tonsillar position and strain on three tracts. The lack of statistically significant difference between strain in CMI subjects with and without imbalance could imply that the magnitude of the observed cardiac-induced strain was too small to cause substantial damage to the tissue (<1%). Activities such as coughing, or Valsalva may produce a greater strain.

Smartphone accelerometry for quantifying core stability and developing exercise training progressions in people with multiple sclerosis

BACKGROUND

Core stability exercise programs have become popular in recent years for preserving balance and functional independence in people with multiple sclerosis (PwMS); however, their real impact is not well-known as the main intervention target (i.e., core stability) theoretically responsible for balance or functional improvements is not measured. The objective of this study was to test the reliability of accelerometers integrated into smartphones for quantifying core stability and developing exercise progressions in PwMS.

METHODS

Twenty participants with MS [age: 47.5±8.0 years; height: 1.62±0.07 m; mass: 63.4±10.9 kg; EDSS: 3.0 (1.5-6)] participated voluntarily in this study. CS was assessed in different variations of the front, side, and back bridges and bird-dog exercises by measuring the mean lumbopelvic acceleration in two testing sessions, separated by one week. Relative and absolute reliability of lumbopelvic acceleration of those exercise variations performed by more than 60% of the participants was analyzed by the intraclass correlation coefficient (ICC_3,1), and the standard error of measurement (SEM) and the minimal detectable change (MDC), respectively. Repeated measures ANOVAs were performed to detect a potential learning effect between test-retest assessments. Statistical significance was set at p < 0.05.

RESULTS

Reliability analyses revealed that good to excellent relative and absolute scores (0.85<ICC<0.96; 7.8%≤SEM≤19.2%; 21.6%≤MDC≤53.2%) for the mean lumbopelvic acceleration obtained during 10 of the 12 CS exercise variations performed by more than 60% of the participants. A non-significant between-session learning effect was detected in all the variables considered (all p values >0.05).

CONCLUSION

Smartphone accelerometry seems a low cost, portable and easy-to-use tool to objectively and reliably track core stability changes in PwMS through. However, in spite of the popularity of bridging and bird-dog exercises, only the short and long bridges and the three-point bird-dog positions proved feasible for most participants. Overall, this study provides useful information to evaluate and guide the prescription of core stability exercise programs in PwMS with mild-to-moderate impairment.

Test-retest reliability of the single leg stance on a Lafayette stability platform

The validity and reliability of the Lafayette stability platform are well-established for double leg testing. However, no evaluation of single leg (SL) stance on the platform was discovered yet. Therefore, this study aimed to investigate the reliability of conducting the SL stance on the Lafayette platform. Thirty-six healthy and active university students (age 23.2 ± 3.2 years; BMI 21.1 ± 3.1 kg/m2) were tested twice, one week apart (week 1; W1, week 2; W2). They stood on their dominant leg with eyes-open (EO) and eyes-closed (EC) in random order. Three successful trials of 20 seconds each were recorded. The duration during which the platform was maintained within 0° of tilt was referred to as time in balance (TIB). At all-time points, TIB was consistently longer in EO (EOW1: 17.02 ± 1.04s; EOW2: 17.32 ± 1.03s) compared to EC (ECW1: 11.55 ± 1.73s; ECW2: 13.08 ± 1.82s). A ±10 seconds difference was demonstrated in the Bland-Altman analysis in both EO and EC. Lower standard error of measurement (SEM) and coefficient of variation (CV) indicated consistent output. High intraclass correlation coefficient (ICC) values were seen between weeks (EO = 0.74; EC = 0.76) and within weeks (EOW1 = 0.79; EOW2 = 0.86; ECW1 = 0.71; ECW2 = 0.71). Although statistical measures (i.e., SEM, CV, and ICC) indicated good reliability of Lafayette for SL tasks, the wide agreement interval is yet to be clinically meaningful. Factors underlying the wide variation need to be identified before Lafayette is used for TIB assessment.

Validation of the patients-specific functional scale in patients with haemophilia

INTRODUCTION

A complete functional assessment is essential to measure health status and treatment effects in patients with haemophilia. The Patient-Specific Functional Scale (PSFS) is a reliable, valid, simple and quick scale that measures physical function in patients with musculoskeletal disorders. However, the reliability and validity of the PSFS have not been evaluated in patients with haemophilia.

AIM

The aim of this study was to validate the Patient-Specific Functional Scale in patients with haemophilia.

METHODS

Twenty-eight patients with haemophilia participated in the study. They completed the PSFS and the Haemophilia Activity List (HAL) scales by telephone during an initial session, and then repeated the assessment in a follow-up session 1 week apart. Reliability was analysed by the internal correlation coefficient (ICC), the standard error of measurement (SEM) and the smallest detectable change (SDC). The concurrent validity of the PSFS was determined by correlating the initial score of the PSFS scale to the initial score of the HAL scale. Correlations were calculated by means of scatter plots and Pearson product-moment r correlation coefficient.

RESULTS

ICC and SEM values showed excellent reliability for the PSFS scale, with a SDC of 1. A significant moderate correlation was found between the results of the PSFS and the HAL (r = .57, P < .001).

CONCLUSION

The PSFS is a reliable and valid scale to measure the functionality of people with haemophilia.

Test-Retest Reliability and Known-Groups Validity of Trunk Muscle Tests in People With Multiple Sclerosis: A Cross-Sectional, Case-Control Study

OBJECTIVE

Research on muscle performance testing reliability in people with multiple sclerosis (MS) has focused on limb performance while less is known about trunk strength and endurance. This work aims to 1) establish test-retest reliability of trunk flexion, lateral flexion, and extension strength tests, and plank, side bridge, and Biering-Sørensen endurance tests in people with MS and matched healthy controls (HCs); 2) analyze known-groups validity of these tests in people with MS and HCs; 3) to compare groups for side-to-side differences; and 4) to describe the relationships between trunk performance and functional mobility tests.

METHODS

Fifteen people with MS (median Expanded Disability Status Scale = 3) and 15 HCs underwent 2 trunk isometric strength and endurance testing sessions. Mobility was evaluated by Timed Up-and-Go test. Intraclass correlation coefficient, SEM, and minimal detectable change (MDC) were calculated. Between-group differences in trunk performance were tested using the t test for independent measures. Between-group differences in an asymmetry index were analyzed by independent t test. Bivariate correlations between trunk tests and mobility were also examined.

RESULTS

All trunk tests showed good-to-excellent relative reliability in both groups (intraclass correlation coefficient > 0.71). Regarding absolute reliability, strength tests were associated with low intersession variability in both groups (MDC: MS, 11.23%-36.45%; HCs, 26.60%-31.98%). Conversely, endurance tests showed higher variability scores in people with MS (MDC: MS, 69.55%-116.50%; HCs, 29.57%-54.40%). People with MS displayed significantly lower trunk performance. Likewise, the asymmetry index showed significantly higher scores in people with MS for endurance assessment but not in strength tests. Significant correlations were detected in people with MS between Timed Up-and-Go and several trunk tests (r = 0.63-0.70).

CONCLUSIONS

SEM and MDC scores revealed similar consistency and variability between groups for strength tests, whereas higher variability was observed for endurance tests in people with MS. Trunk strength tests are reliable and present discriminant validity to distinguish mildly disabled people with MS from HCs. Conversely, the high measurement error and variability of the endurance tests may hinder their application in intervention programs.

IMPACT

Determining the reliability and validity of the tests currently used to assess trunk function is of the greatest importance for people with MS (who show not only impaired trunk function but also wide fluctuations in performance), as it requires consistent and accurate measurements that are sensitive enough to detect minimal changes induced by rehabilitation.

Do Initial Trunk Impairment, Age, Intervention Onset, and Training Volume Modulate the Effectiveness of Additional Trunk Exercise Programs after Stroke? A Systematic Review with Meta-Analyses

The aim of this systematic review is to analyze how, after additional trunk-focused training programs (ATEP), motor recovery after a stroke is modulated by potential effect modifiers. Twenty randomized controlled studies that carried out ATEP were included. Results showed moderate-to-high effects in favor of ATEP for trunk function, balance ability, gait performance, and functional mobility. Studies with a higher initial trunk impairment obtained a higher effect on trunk function and balance; studies with older participants had a higher effect on trunk function, limit of stability, and functional mobility, but not on balance ability. Older and more affected patients were, as well, those who started the intervention earlier, which was also linked with higher effects on trunk function, balance, and gait performance. Longer ATEP found a high effect on trunk function and balance ability. The potential effect modifiers seem to be important in the modulation of the effectiveness of ATEP and should be considered in the design of rehabilitation programs. Thus, since potential effect modifiers seem to modulate ATEP effectiveness, future studies should consider them in their experimental designs to better understand their impact on stroke rehabilitation.

Sempere Á, Vera-Garcia FJ, Barbado D. Understanding the Deterioration of Gait, Postural Control, Lower Limb Strength and Perceived Fatigue Across the Disability Spectrum of People with Multiple Sclerosis

Disability progression is a prominent feature of multiple sclerosis (MS). However, little is known about the extent to which physical condition parameters and perceived fatigue evolve during the disease. We analyzed how strength, balance, core stability and perceived fatigue differ among different cohorts of people with MS (PwMS) with different disability degrees and how these contribute to patients' gait speed and functional mobility. Sixty-three PwMS divided into three groups according to the "Expanded Disability Status Scale" (MS1: EDSS ≤ 1.5; MS2: 2 ≤ EDSS ≤ 3.5; MS3: 4 ≤ EDSS ≤ 6) and 22 healthy controls (HC) participated in this study. MS1 showed lower balance and hip strength compared to HC. MS2 showed lower balance, core stability, gait speed, and functional mobility than MS1. MS3 showed lower gait speed, functional mobility, balance, and knee flexion strength than MS2. No between-group differences were observed in perceived fatigue. Relative weight analysis showed that strength, balance and core stability explained 60%-70% of the variance in gait speed and functional mobility. The decline of each parameter did not evolve at the same rate across the different stages of the disease, being knee flexion strength and balance the most influential factors in the disability progression. Overall, these results provide useful information to guide exercise prescription at different stages of MS.