Preprocessing the Nintendo Wii Board Signal to Derive More Accurate Descriptors of Statokinesigrams

Postural performance assessment in aging people with diabetes and diabetic peripheral neuropathy using a Wii balance board

PURPOSE

To determine the effect of sensory perturbations on static postural control in older people with type 2 diabetes mellitus by comparing postural outcomes of people with and without diabetic neuropathy using a Wii Balance Board (WBB).

MATERIALS AND METHODS

Static postural balance assessments were performed in 31 participants: nine with type 2 diabetes mellitus; 12 with diabetic neuropathy; and 10 non-diabetic controls. Participants stood on the WBB under sensory perturbations (visual and proprioceptive). Body balance was analysed using centre of pressure ellipse area, mean velocity, and sample entropy. The effects of within-participant factors, sensory perturbations and the between-participants factor 'group' on outcomes were analysed using a multivariate analysis of variance model.

RESULTS

Type 2 diabetes mellitus participants with and without neuropathy showed altered postural performance under sensory perturbations compared to non-diabetic participants. Moreover, participants with diabetic neuropathy showed impaired postural performance when one perceptual system was disturbed. Finally, participants with type 2 diabetes mellitus without neuropathy decreased their postural performance when both sensory disturbances were present.

CONCLUSIONS

The Wii Balance Board can be a useful alternative for balance impairment screening related to diabetic neuropathy and contribute as an affordable source of insight in early interventions in integral diabetes care.Implications to rehabilitationOlder people with diabetic peripheral neuropathy depend on visual and somatosensory cues to keep their static postural balance.Static balance assessment using the Wii Balance Board allows the identification of alterations in postural performance in participants with diabetes.This low-cost method used can be considered as a complement to integral diabetes care.

Identifying neuropathies through time series analysis of postural tests

BACKGROUND

In physical therapy, postural tests are frequently used to diagnose neuropathies, particularly in diabetic individuals. This study aims to develop a method based on the analysis of time series that allows discriminating between healthy and diabetic subjects with or without a neuropathic condition.

RESEARCH QUESTION

Do features obtained from time series corresponding to postural tests allow us to reliably discriminate between healthy, diabetic and neuropathic patients?

METHODS

In this study, 32 people participated in the healthy, diabetic, and neuropathic categories (11, 9, and 12, respectively). The data was collected by positioning each participant on a Wii Balanced Board platform, under 8 different conditions. The analyzed time series are sensed by devices that capture variations in the subject's center of pressure when subjected to a test on different conditions over a short period of time. The method proposed considers statistical techniques used for characterizing the time series combined with machine learning techniques to classify the individual's profile into one of the three categories mentioned. The classification is supported by an underlying probabilistic model, based on the characteristics of the time series, generating average curves for each class, which are then used by the classification methods.

RESULTS

The empirical results include classification models for each class, obtaining a performance (F-score) over 98%. In addition, other models considering the particular conditions to which the subject is exposed during the test are developed, revealing that the conditions of eyes open and eyes closed show the highest levels of discrimination to classify participants into one of the three class categories.

SIGNIFICANCE

These results suggest a test protocol simplification and, at the same time, that the proposed method based on the analysis of the time series associated with the test used is highly predictive and may reliably complement or substitute a questionnaire-based diagnosis.

Concurrent validity of the inertial sensors for assessment of balance control during quiet standing in patients with chronic low back pain and asymptomatic individuals

The objective was to investigate the concurrent validity of inertial sensors for measuring balance control in patients with chronic low back pain and asymptomatic individuals. Thirty-nine patients with chronic low back and 39 age- and sex-matched asymptomatic individuals were included. Balance control analysis was performed in quiet standing with two inertial sensors positioned at the lumbar region and the sternum and compared to the results of a force plate. The variables analysed with either device were Root Mean Square (RMS), index of smoothness (JERK), trajectory length (PATH) and area (AREA). Spearman's correlation coefficient investigated the correlation. Patients with chronic low back pain showed moderate correlation with the inertial sensor positioned on the lumbar for RMS (r_s = 0.59; p < 0.01), PATH (r_s = 0.42, p = 0.01) and AREA (r_s = 0.59; p < 0.01) and weak correlation with the inertial sensor positioned on the sternum for PATH (r_s = 0.36, p = 0.04). The asymptomatic group showed statistically significant correlations for RMS for the lumbar (r_s = 0.38; p = 0.03) and sternum inertial sensor (r_s = 0.42; p = 0.02). Inertial sensors showed weak to moderate correlations compared to data obtained from a force plate.

A review of center of pressure (COP) variables to quantify standing balance in elderly people: Algorithms and open-access code

Postural control is often quantified by recording the trajectory of the center of pressure (COP)-also called stabilogram-during human quiet standing. This quantification has many important applications, such as the early detection of balance degradation to prevent falls, a crucial task whose relevance increases with the aging of the population. Due to the complexity of the quantification process, the analyses of sway patterns have been performed empirically using a number of variables, such as ellipse confidence area or mean velocity. This study reviews and compares a wide range of state-of-the-art variables that are used to assess the risk of fall in elderly from a stabilogram. When appropriate, we discuss the hypothesis and mathematical assumptions that underlie these variables, and we propose a reproducible method to compute each of them. Additionally, we provide a statistical description of their behavior on two datasets recorded in two elderly populations and with different protocols, to hint at typical values of these variables. First, the balance of 133 elderly individuals, including 32 fallers, was measured on a relatively inexpensive, portable force platform (Wii Balance Board, Nintendo) with a 25-s open-eyes protocol. Second, the recordings of 76 elderly individuals, from an open access database commonly used to test static balance analyses, were used to compute the values of the variables on 60-s eyes-open recordings with a research laboratory standard force platform.

Postural sway in the moving room scenario: New evidence for functional dissociation between self-motion perception and postural control

Postural control in quiet standing is often explained by a reflexive response to optical flow, the apparent motion of environmental objects in a visual scene. However, moving room experiments show that even small-amplitude body sway can evoke odd sensations or motion sickness, indicating that a consciousness factor may also be involved. Studies targeting perception of self-motion, vection, typically use rapid visual stimuli moving in a single direction to maintain a constant feeling of vection, and there are few studies of vection using low-speed sinusoidal visual stimuli similar to human pendular movement. In the present study we searched for changes in postural control during periods of vection during quiet standing. Participants (N = 19, age = 20.4 ±1.1 years) were shown dynamic visual stimuli in the form of sinusoidally expanding and contracting random dots, and the stimuli speed and visual field were manipulated. Posture was continually evaluated using Center of Pressure (CoP) measurements. Participants were also asked to report feelings of vection, both by pressing a button during the trial and through an overall rating at the end of each trial. Using repeated-measures ANOVA, we assessed changes in the CoP and vection variables between experimental conditions, as well as possible interactions between the variables. The results show that postural reaction and vection were both affected by the visual stimuli and varied with speed. The peripheral visual field was found to couple to stronger feeling of vection and better quality of postural control. However, no significant relationship between postural control and vection, nor evidence of vection interaction to the relationship between optical flow and postural control, was found. Based on our results we conclude that for postural stability during quiet standing, visual cues dominate over any potential consciousness factor arising due to vection.

Revealing posturographic profile of patients with Parkinsonian syndromes through a novel hypothesis testing framework based on machine learning

Falling in Parkinsonian syndromes (PS) is associated with postural instability and consists a common cause of disability among PS patients. Current posturographic practices record the body's center-of-pressure displacement (statokinesigram) while the patient stands on a force platform. Statokinesigrams, after appropriate processing, can offer numerous posturographic features. This fact, although beneficial, challenges the efforts for valid statistics via standard univariate approaches. In this work, 123 PS patients were classified into fallers (PSF) or non-faller (PSNF) based on the clinical assessment, and underwent simple Romberg Test (eyes open/eyes closed). We developed a non-parametric multivariate two-sample test (ts-AUC) based on machine learning, in order to examine statokinesigrams' differences between PSF and PSNF. We analyzed posturographic features using both multiple testing with p-value adjustment and ts-AUC. While ts-AUC showed significant difference between groups (p-value = 0.01), multiple testing did not agree with this result (eyes open). PSF showed significantly increased antero-posterior movements as well as increased posturographic area compared to PSNF. Our study highlights the superiority of ts-AUC compared to standard statistical tools in distinguishing PSF and PSNF in multidimensional space. Machine learning-based statistical tests can be seen as a natural extension of classical statistics and should be considered, especially when dealing with multifactorial assessments.

Postadychute-AG, Detection, and Prevention of the Risk of Falling Among Elderly People in Nursing Homes: Protocol of a Multicentre and Prospective Intervention Study

Introduction: While falls among the elderly is a public health issue, because of the social, medical, and economic burden they represent, the tools to predict falls are limited. Posturography has been developed to distinguish fallers from non-fallers, however, there is too little data to show how predictions change as older adults' physical abilities improve. The Postadychute-AG clinical trial aims to evaluate the evolution of posturographic parameters in relation to the improvement of balance through adapted physical activity (APA) programs. Methods: In this prospective, multicentre clinical trial, institutionalized seniors over 65 years of age will be followed for a period of 6 months through computer-assisted posturography and automatic gait analysis. During the entire duration of the follow-up, they will benefit from a monthly measurement of their postural and locomotion capacities through a recording of their static balance and gait thanks to a software developed for this purpose. The data gathered will be correlated with the daily record of falls in the institution. Static and dynamic balance measurements aim to extract biomechanical markers and compare them with functional assessments of motor skills (Berg Balance Scale and Mini Motor Test), expecting their superiority in predicting the number of falls. Participants will be followed for 3 months without APA and 3 months with APA in homogeneous group exercises. An analysis of variance will evaluate the variability of monthly measures of balance in order to record the minimum clinically detectable change (MDC) as participants improve their physical condition through APA. Discussion: Previous studies have stated the MDC through repeated measurements of balance but, to our knowledge, none appear to have implemented monthly measurements of balance and gait. Combined with a reliable measure of the number of falls per person, motor capacities and other precipitating factors, this study aims to provide biomechanical markers predictive of fall risk with their sensitivity to improvement in clinical status over the medium term. This trial could provide the basis for posturographic and gait variable values for these elderly people and provide a solution to distinguish those most at risk to be implemented in current practice in nursing homes. Trial Registration: ID-RCB 2017-A02545-48. Protocol Version: Version 4.2 dated January 8, 2020.

Equimetrix Device: Criteria Based Validation and Reliability Analysis of the Center of Mass and Base of Support of a Human Postural Assessment System

Human postural control is a fundamental ability for static and dynamic tasks, especially in hiper- and hipo-functional populations, such as the elderly. The Equimetrix is a clinical device developed to assess both the base of support (BoS) and the center of mass (CoM) dynamics, thus allowing their use as new evaluation and training tools. This study aims to perform a criteria based validation of Equimetrix by comparing the BoS and CoM data with gold-standard equipment. A motion capture system, force platform, and pressure mat were used to calculate the CoM, center of pressure (CoP) and BoS during bipedal, unipedal, feet together and full tandem stances. Results demonstrate an excellent reliability of Equimetrix in terms of spatial accuracy of the CoM, although over-estimating the CoM height. Differences were found when comparing Mean velocity Path with the CoM, but not with the CoP, indicating a lower reliability in time-based parameters. The Equimetrix presents a tendency to overestimate the BoS, with mixed reliability values, which may be related to the different size of sensing elements between the Equimetrix and the pressure sensing mat. These are encouraging results that should be further explored during dynamic tasks.

Description of Participants in the "Atout Age Mobility" Prevention Workshops at the University Hospital Center of La Réunion: A Prospective Study

INTRODUCTION

As the population ages, loss of autonomy is becoming a priority public health issue. "Atout Age Mobility" prevention interventions for seniors aim to limit frailty, which is a predictive and reversible factor in the loss of autonomy and disability.

OBJECTIVES

The objective of this study is to describe the impact of these interventions on the physical performance and quality of life of a pilot sample of participants.

DESIGN

We conducted a prospective study named 5P PILOT with 3 months of follow up.

SETTINGS

Subjects were recruited by convenience sampling from participants in the "Atout Age Mobility" workshops at Saint Joseph from 04/09/2017 to 29/01/2019.

PARTICIPANTS

Retired people over 55 years old with no contraindications to physical activity recruited from participants in the "Atout Age Mobility" workshops in Saint Joseph. Intervention(s) (for clinical trials) or Exposure(s) (for observational studies): All participants completed 12 weeks of physical exercise called the "Atout Age Mobility" workshop, which lasted 60 minutes each week and was supervised by physical activity coaches. Main Outcome(s) and Measure(s): Physical performance was assessed by Short physical performance battery (SPPB), 10-m gait speed and grip strength measurement. Quality of life through the SF-36 test.

RESULTS

Ninety-six patients were included and 55 (57.3%) completed the study. There was a significant improvement in gait speed (1.35±0.26m/s vs. 1.27±0.24m/s; p=0.008). There was no significant change in SF-36, grip strength dominant arm and SPPB at the 0.01 significance level.

CONCLUSION

The "Atout Ages Mobility" workshops seem to significantly improve gait speed but not other aspects of physical performance or quality of life.

Portable Device for the Measurement and Assessment of the Human Equilibrium

This work presents the design and development of a new alternative tool to measure the Center of Pressure (CoP) displacements, intended to evaluate the human balance. The device is based on a modified commercial balance board used for video games, resulting in a low-cost, portable device capable of computing the CoP, providing 24 of the most used indexes to test the human balance. The proposed standalone device runs on rechargeable batteries, weighs only 3.5 kg, and has a data storage capacity for over 1000 tests. Visual and auditory instructions assist its user interface. Thus, contrary to the commercial systems designed for laboratory use, this device enables the measurement of quantitative balance parameters in non-laboratory places, allowing the study of the balance of vulnerable populations directly on their typical environments. To evaluate the device, 20 older adults (68.60 ± 1.23 years) were tested, and the resulting values were compared with a similar study using a force platform; 19 indexes showed a similarity with those reported using force platform and 12 of these were statistically equivalent. The proposed device represents an open-source alternative tool for researchers and healthcare personnel to acquire reliable data to evaluate human balance.

Reliability and robustness of optimization properties for stabilization of the upright stance as determined using posturography

Diagnostic value of static posturography depends on its methodological features, measurement properties, and on computational methods that extract meaningful information from the postural sway i.e. the center-of-pressure (CoP) displacements. In this study, we assessed the reliability and robustness of the postural system based on the optimization properties of the CoP signal: descending, local and global stability, and convergence. For the analysis, we used CoP data from 146 participants (104 [71%] female, age 46 ± 23 years, body mass index 23.6 ± 3.4 kg/m²) recorded while standing quietly on a foam surface without visual input. Reliability was estimated using the intraclass correlation coefficient from a single (ICC_2,1) and averaged (ICC_2,3) measurements. Robustness was assessed through main and interaction effects for the signal duration (60, 30 s), sampling frequency (100, 50 Hz), and lowpass filtering cutoff frequency (10, 5 Hz). The observed reliability depended on the use of average or single measurements as it was excellent for the stability property (ICC_2,k ≥ 0.772); excellent-to-acceptable (ICC_2,3 ≥ 0.540) or excellent-to-unacceptable (ICC_2,1 ≥ 0.281) for the descending property; and excellent-to-unacceptable (ICC_2,3 > 0.295; ICC_2,1 > 0.122) for the convergence property. Robustness analysis showed large main effects of signal duration (ω² ≤ 0.834, p < 0.001), sampling frequency (ω² ≤ 0.526, p < 0.001), and the lowpass filter cutoff frequency (ω² ≤ 0.523, p < 0.001) on the optimization properties; but all two-way and three-way effects varied from medium to trivial. Reliability is thus excellent to acceptable for deriving the descending, stability, and convergence properties from the average of three measurements. Those optimization properties are robust to the interaction but not the main effects of methodological sources of variation of posturography.

Balance Markers and Saccadic Eye-Movement Measures in Adolescents With Postconcussion Syndrome

CONTEXT

Deficits in both balance and oculomotor function, including impairments in saccadic eye movements, are observed in approximately 30% of patients postconcussion. Whereas balance and saccadic eye movements are routinely assessed separately, growing evidence suggests that they should be assessed concurrently.

OBJECTIVE

To compare balance measures and saccades between adolescents 1 to 3 months postconcussion and healthy uninjured adolescents.

DESIGN

Case-control study.

SETTING

Concussion clinic and 2 private schools.

PATIENTS OR OTHER PARTICIPANTS

Twenty-five adolescents (10 boys, 15 girls; median [interquartile range (IQR)] age = 14 years [11.5-16 years]) between 1 and 3 months postconcussion (median [IQR] time since injury = 39.5 days [30-56.75 days]) and 33 uninjured adolescents (18 boys, 15 girls; median [IQR] age = 13 years [11.5-14 years]).

MAIN OUTCOME MEASURE(S)

The center-of-pressure 95% ellipse area and medial-lateral and anterior-posterior velocity and the number of saccades in the dual-task balance conditions including a high cognitive load (cognitive condition), a low cognitive load and a gaze-shifting component (visual condition) or both a high cognitive load and a gaze-shifting component (combined condition).

RESULTS

Concussion-group participants swayed over larger center-of-pressure ellipse areas in the visual (P = .02; effect size = 0.73) and combined (P = .005; effect size = 0.86) conditions but not in the cognitive condition (P = .07; effect size = 0.50). No group differences were identified for anterior-posterior (F_1,56 = 2.57, P = .12) or medial-lateral (F_1,56 = 0.157, P = .69) velocity. Concussion-group participants also did not perform more saccades than the control-group participants (F_1,56 = 2.04, P = .16).

CONCLUSIONS

Performing dual-task balance conditions for which the secondary task involved a gaze-shifting component or both a gaze-shifting component and a high cognitive load resulted in greater sway amplitude in adolescents with concussion. However, these larger amounts of postural sway were not associated with increased saccadic eye movements.

Portable electronic device to assess the human balance using a minimum number of sensors

OBJECTIVE

This paper presents the design and development of a new electronic portable device to assess the human balance of the human body during standing, using a minimal number of sensors and peripheral components. This device is aimed to evaluate human balance in environments outside of specialized laboratories, such as small clinics and therapy offices.

APPROACH

The design is based on previous designs using three or more resistive force sensors attached to the feet, however in the present work, the sensors were attached on an adjustable platform, to fit several sizes of feet. Furthermore, all the signal acquisition, process, storage and display are executed by an embedded electronic system, thus avoiding the use of computers and external peripherals. A new method to compute the CoP using only two sensors per foot was developed and tested in a group of 50 university students, (17 women and 33 men), 26.04 ± 4.94 years.

MAIN RESULTS

It was developed a portable electronic system to measure the trajectory of the CoP and to calculate the indexes values derived from it. The system is capable to discriminate between measuring situations (open and closed eyes), using only two sensors per foot (p < 0.0001). A comparison between the values obtained for young subjects using the proposed device, and the values reported in the literature showed a similar tendency.

SIGNIFICANCE

The results indicate that the proposed system is a good, low-cost, and easy-to-use alternative tool for researchers and clinicians interested in the evaluation of human balance, especially if the measurements must be done outside laboratories.

Agreement and predictive power of six fall risk assessment methods in community-dwelling older adults

A large number of fall risk assessment methods are available with a variety of performances for screening the risk of falling in older adults, but their agreement for assessing the risk of falling remains unknown. This observational prospective cohort study describes the agreement and predictive power of methods to classify the risk of falling in older adults using prospective data and published cut-off values. Fifty-two participants aged 74 years (interquartile range 69-80) were assessed using the Berg Balance Scale, polypharmacy, Falls Risk Assessment Score, Fall Risk Assessment Tool, Fall Efficiency Scale, and Posturography. Nine participants (17 %) reported at least one fall after six months. Cochran's test showed different proportions of participants classified as at high risk of falling among all methods (Q = 69.560, p < 0.001). A slightly better-then-chance agreement was estimated between all FRA methods (Light's κ = 0.074, 95%CI [0.021; 0.142]). We found both global and pairwise agreement levels that question the agreement among fall risk assessment methods for screening community-dwelling older adults.

Balance Impairment in Radiation Induced Leukoencephalopathy Patients Is Coupled With Altered Visual Attention in Natural Tasks

Background: Recent studies have shown that alterations in executive function and attention lead to balance control disturbances. One way of exploring the allocation of attention is to record eye movements. Most experimental data come from a free viewing of static scenes but additional information can be leveraged by recording eye movements during natural tasks. Here, we aimed to provide evidence of a correlation between impaired visual alteration in natural tasks and postural control in patients suffering from Radiation-Induced Leukoencephalopathy (RIL).

Methods: The study subjects were nine healthy controls and 10 patients who were diagnosed with RIL at an early stage, with isolated dysexecutive syndrome without clinically detectable gait or posture impairment. We performed a balance evaluation and eye movement recording during an ecological task (reading a recipe while cooking). We calculated a postural score and oculomotor parameters already proposed in the literature. We performed a variable selection using an out-of-bag random permutation and a random forest regression algorithm to find: (i) if visual parameters can predict postural deficit and, (ii) which are the most important of them in this prediction. Results were validated using the leave-one-out cross-validation procedure.

Results: Postural scores indeed were found significantly lower in patients with RIL than in healthy controls. Visual parameters were found able to predict the postural score of RIL patients with normalized root mean square error (RMSE) of 0.16. The present analysis showed that horizontal and vertical eye movements, as well as the average duration of the saccades and fixations influenced significantly the prediction of the postural score in RIL patients. While two patients with very low MATTIS-Attention sub score showed the lowest postural scores, no statistically significant relationship was found between the two outcomes.

Conclusion: These results highlight the significant relationship between the severity of balance deficits and the visual characteristics in RIL patients. It seems that increased balance impairment is coupled with a reduced focusing capacity in ecological tasks. Balance and eye movement recordings during a natural task could be a useful aspect of multidimensional scoring of the dysexecutive syndrome.

On the importance of local dynamics in statokinesigram: A multivariate approach for postural control evaluation in elderly

The fact that almost one third of population >65 years-old has at least one fall per year, makes the risk-of-fall assessment through easy-to-use measurements an important issue in current clinical practice. A common way to evaluate posture is through the recording of the center-of-pressure (CoP) displacement (statokinesigram) with force platforms. Most of the previous studies, assuming homogeneous statokinesigrams in quiet standing, used global parameters in order to characterize the statokinesigrams. However the latter analysis provides little information about local characteristics of statokinesigrams. In this study, we propose a multidimensional scoring approach which locally characterizes statokinesigrams on small time-periods, or blocks, while highlighting those which are more indicative to the general individual’s class (faller/non-faller). Moreover, this information can be used to provide a global score in order to evaluate the postural control and classify fallers/non-fallers. We evaluate our approach using the statokinesigram of 126 community-dwelling elderly (78.5 ± 7.7 years). Participants were recorded with eyes open and eyes closed (25 seconds each acquisition) and information about previous falls was collected. The performance of our findings are assessed using the receiver operating characteristics (ROC) analysis and the area under the curve (AUC). The results show that global scores provided by splitting statokinesigrams in smaller blocks and analyzing them locally, classify fallers/non-fallers more effectively (AUC = 0.77 ± 0.09 instead of AUC = 0.63 ± 0.12 for global analysis when splitting is not used). These promising results indicate that such methodology might provide supplementary information about the risk of fall of an individual and be of major usefulness in assessment of balance-related diseases such as Parkinson’s disease.

A Non Linear Scoring Approach for Evaluating Balance: Classification of Elderly as Fallers and Non-Fallers

Almost one third of population 65 years-old and older faces at least one fall per year. An accurate evaluation of the risk of fall through simple and easy-to-use measurements is an important issue in current clinic. A common way to evaluate balance in posturography is through the recording of the centre-of-pressure (CoP) displacement (statokinesigram) with force platforms. A variety of indices have been proposed to differentiate fallers from non fallers. However, no agreement has been reached whether these analyses alone can explain sufficiently the complex synergies of postural control. In this work, we study the statokinesigrams of 84 elderly subjects (80.3+− 6.4 years old), which had no impairment related to balance control. Each subject was recorded 25 seconds with eyes open and 25 seconds with eyes closed and information pertaining to the presence of problems of balance, such as fall, in the last six months, was collected. Five descriptors of the statokinesigrams were computed for each record, and a Ranking Forest algorithm was used to combine those features in order to evaluate each subject’s balance with a score. A classical train-test split approach was used to evaluate the performance of the method through ROC analysis. ROC analysis showed that the performance of each descriptor separately was close to a random classifier (AUC between 0.49 and 0.54). On the other hand, the score obtained by our method reached an AUC of 0.75 on the test set, consistent over multiple train-test split. This non linear multi-dimensional approach seems appropriate in evaluating complex postural control.