Analysis Of Sway Research Articles

Effect of fatigue on postural sway in sport-specific positions of young rhythmic gymnasts

In rhythmic gymnastics, balance represents a key element in achieving optimal performance. However, there is a lack of data on the modalities with which postural control is impaired by fatigue originated by actual competitive performance. This study aims to analyze the effect of fatigue consequent to a competitive performance on static balance of rhythmic gymnasts (quantitatively assessed by means of postural sway analysis) for several sport-specific positions. Fifteen rhythmic gymnasts (mean age 12.7 years) who compete at national and regional levels participated in the study. Their balance was assessed before and after a 90 s performance for 4 unipedal positions (i.e., “ring with hand support”, “back split without hand support”, “arabesque”, and “split with hand support”) using a pressure platform. Center-of-pressure (COP) time series acquired for 10 s was processed to calculate sway area, COP path length, and COP displacements in the antero-posterior and medio-lateral directions. After the performance, a generalized increase in postural sway was detected for all the positions tested, with the exception of “arabesque”. Sway area doubled for most positions after the performance, while fatigue appears to have a reduced effect on COP displacements in the ML direction, which were found significantly increased only for the “split with hand support” position. The physical effort associated with the performance influences the effectiveness of the postural control system. Coaches could include specific balance exercises even when gymnasts are fatigued to improve their adaptations to competitive conditions and reduce the risk of injuries.

Development and Validation of Wearable Inertial Sensor System for Postural Sway Analysis

Postural sway is a fall risk assessment tool traditionally measured using forceplates. However, it is expensive and lack portability to usage in clinical environments. In this study, a wearable low-cost MEMS inertial sensor was developed and validated for sway assessment. This study had two principal objectives (1) To develop and validate an Inertial Measurement Unit (IMU) for sway analysis (2) To assess the feasibility of IMU in detecting slight balance impairments due to reduced proprioception or induced subthreshold vibrations on the feet. A total of 10 healthy young adults (five males and five females) participated in this study. We found that sway velocity, Root Mean Square (RMS), and sway path length could successfully differentiate postural changes due to varying proprioceptive and sub-threshold vibration conditions. We conclude that new cheap wearable sensors can be designed for accurate clinical postural sway assessments and have potential to diagnose postural impairments.

Demonstration of the Effect of Centre of Mass Height on Postural Sway Using Accelerometry for Balance Analysis

The effect of center of mass (COM) height on stand-still postural sway analysis was studied. For this purpose, a measurement apparatus was set up that included an accelerometry device attached to a rod: three plumb lines, positioned at 50, 75 and 100 cm to an end of the rod, each supported a plumb bob. Using a vice mechanism, the rod was inclined from vertical (0 degree inclination) in steps of 5 degrees to 90 degrees. For each inclination, the corresponding inclination angle was manually measured by a protractor and the positions of the three plumb bobs on the ground surface were also manually measured using a tape measure. Algebraic operations were used to calculate the inclination angle and the associated displacements of the plumb bobs on the ground surface from the accelerometry data. For each inclination angle, the manual and accelerometry calculated ground displacement were close. The height of COM, where the measurement was taken, affected the projected displacement on the ground surface. The COM height had a nonlinear double-effect relationship with sway as it can affect both the angle and projected sway. Normalization of the COM height was used to reduce this effect for comparison purposes.

Inter-trial phase coherence of visually evoked postural responses in virtual reality

Vision plays a central role in maintaining balance. When humans perceive their body as moving, they trigger counter movements. This results in body sway, which has typically been investigated by measuring the body’s center of pressure (COP). Here, we aimed to induce visually evoked postural responses (VEPR) by simulating self-motion in virtual reality (VR) using a sinusoidally oscillating “moving room” paradigm. Ten healthy subjects participated in the experiment. Stimulation consisted of a 3D-cloud of random dots, presented through a VR headset, which oscillated sinusoidally in the anterior–posterior direction at different frequencies. We used a force platform to measure subjects’ COP over time and quantified the resulting trajectory by wavelet analyses including inter-trial phase coherence (ITPC). Subjects exhibited significant coupling of their COP to the respective stimulus. Even when spectral analysis of postural sway showed only small responses in the expected frequency bands (power), ITPC revealed an almost constant strength of coupling to the stimulus within but also across subjects and presented frequencies. Remarkably, ITPC even revealed a strong phase coupling to stimulation at 1.5 Hz, which exceeds the frequency range that has generally been attributed to the coupling of human postural sway to an oscillatory visual scenery. These findings suggest phase-locking to be an essential feature of visuomotor control.

Biomechanics of Vertical Posture and Control with Referent Joint Configurations

Our study compared the results of two methods of analysis of postural sway during human quiet standing, the rambling-trembling (Rm-Tr) decomposition and the analysis of the point of intersection of the ground reaction forces (zIP analysis). Young, healthy subjects were required to stand naturally and with an increased level of leg/trunk muscle co-activation under visual feedback on the magnitude of a combined index of muscle activation (muscle mode). The main findings included the shift of zIP toward higher frequencies and strong correlations between Tr and zIP when the subjects stood with increased muscle co-activation. We interpret the results within the idea of whole-body control with a set of primitives associated with referent coordinates in the joint configuration space.

094 Towards objective testing in parkinson’s disease: a systematic review of the literature looking at assessment of postural sway

IntroductionParkinson’s Disease (PD) is associated with increased mortality and reduced quality of life. There is currently no accurate objective measure for use in diagnosis or assessment of severity. Analysis of postural sway may help in this regard. This systematic review aimed to assess the effectiveness of the various features currently used to analyse postural sway.MethodsFive databases were searched for articles that examined postural sway in both PD patients and controls. An effect size (ES) was derived for every feature reported in each article. The most effective features and feature-families were determined, along with the influence on these measures of data sampling rate and experimental condition.Results441 papers were initially retrieved, of which 31 met the requirements for analysis. The most commonly-used features were not the most effective (e.g. PathLength had an ES of 0.47 while TotalEnergy had an ES of 1.78). Decreased sampling rate was associated with decreased ES (e.g. ES of PathLength lowered from 1.12 at 100 Hz to 0.40 at 10 Hz). Being off medication was associated with a larger ES (e.g. ES of PathLength was 0.21 on medication and 0.83 off medication).ConclusionsSome measures of postural sway are better able to distinguish PD patients from controls than others. ES is enhanced by using a higher sampling rate and studying patients off medication. These results will inform future studies looking at postural sway in PD and contribute to the aim of finding an objective marker of the disease.

Transfemoral amputee’s limit of stability and sway analysis during weight shifting exercise with a vibrotactile feedback system

Amputation in the transfemoral amputee (TFA) results in loss of sensory feedback of the amputated limb and therefore results in the poor postural stability. To assess the postural stability, the limit of stability (LOS) is a reliable parameter. In this study, we have investigated the effect of vibrotactile feedback (VF) on the LOS during the weight shifting exercise (WSE) for a TFA. The data of centre of pressure (COP) during WSE was collected from five TFA and five healthy individuals using a zebris force plate. The VF was provided on the amputated/healthy limb’s anterior and posterior part of the stump/thigh during forward and backward WSE, respectively. A customized foot insole with 24 embedded dielectric sensors was used to drive the vibratory motor. The effect of VF was analyzed by pre and post-test. Results show that with the use of VF, TFA significantly improved (t-test, p < .05) the sound limb’s LOS during forward WSE. Also, ANOVA analysis between WSE divisions shows that the prosthetic limb does not follow the path of WSE. We further examine the spectral power using the Welch method to determine the dominant sway frequency of COP. It shows a decreased frequency between 0.5–2 Hz in the healthy and decreased frequency between 0–0.5 Hz and >2 Hz in the amputee with VF. It concluded that VF could improve the LOS of TFA during WSE which ultimately leads to postural stability enhancement.

Nonlinear Dynamics Analysis of the Body Sway of Car-trailer Combinations

Nonlinear Dynamics Analysis of the Body Sway of Car-trailer Combinations

Analysis of Rope Sway during Travel of Elevator

An elevator for a high-rise building ought to perform emergency operation when the elevator rope is oscillated by the sway of the building caused by wind force or long – period ground motion. In recent years, techniques for directly measuring rope amplitude in real time have been utilized. Thereby, it has become possible to perform apposite emergency operation based on the rope sway condition. On the other hand, the rope sway changes continuously every moment during the travel of elevator. Therefore, it is very important to grasp the changing tendency of rope sway for the efficient judgment of emergency operation. In this research, we constructed a simulation model which quantitatively simulates the rope sway motion during a travel of an elevator.

Standing balance in preschoolers using nonlinear dynamics and sway density curve analysis

The aim of the present study was to investigate how age and sensory deprivation affect the temporal organization of CoP sway variability and the postural corrective commands during standing balance in typically developing preschoolers. A sample of 57 children aged 3–5 years participated in the study. Structural stabilometric descriptors of sample entropy (SEn), detrended fluctuation analysis (DFA), and sway density curve (SDC) analysis were employed to assess features of center of pressure sway. A force platform was used to collect center of pressure data during standing balance over 40 s in four conditions: standing on rigid and foam surfaces with eyes open and closed. The main results are as follows: (1) sample entropy decreased and DFA_coefficient increased with age, while the SDC variables remained unaltered among the 3-, 4-, and 5-year-old children; (2) as sensory conditions became more challenging, sample entropy decreased and DFA_coefficient increased, while MT and MD decreased and MD increased; age did not influence the responses to sensorial deprivation. In conclusion, 5-year-old children showed decreased variability of CoP sway during standing balance compared with the younger children, but all children used the same corrective torques to control for perturbations. More challenging sensory deprivation conditions resulted in decreased variability of postural sway, higher amplitudes and more frequent correcting torques for stabilization, but age did not influence these behaviors.

Body postural sway analysis in older people with different fall histories.

A cross-sectional study of postural sway analysis in older non-fallers, once-fallers and multiple-fallers using five common standing tests was conducted. Eighty-six older subjects with an average age of 80.4years (SD ± 7.9) participated in the study. The angular rotation and velocity of the trunk of the participants in the roll (lateral) and pitch (sagittal) planes were recorded using an inertial sensor mounted on their lower backs. The Gaussian Mixture Models (GMM), Expectation-Maximisation (EM) and the Minimum Message Length (MML) algorithms were applied to the acquired data to obtain an index indicative of the body sway. The standing with feet together and standing with one foot in front, sway index distinguished older fallers from non-fallers with specificity of 75.7% and 77.7%, respectively, and sensitivity of 78.6% and 82.1%, respectively. This compares favourably with the Berg Balance Scales (BBS) with specificity of 70.5% and sensitivity of 75.3%. The results suggest that the proposed method has potential as a protocol to diagnose balance disorder in older people. Graphical abstract.

Time series analysis of body sway caused by several matrix-shaped tactile stimuli on body trunk

Postural control is an essential function of the human body that uses several senses and information from the body as input, processes the input and then provides output to the muscles for control. In this study, we examine a method wherein several matrix-shaped tactile stimuli (MSTS) located on the skin of the trunk are used to away subjects’ bodies. To clarify the relationship between body sway and the MSTS, the subjects were tracked using a high-speed camera, a foot pressure distribution measuring instrument, and two acceleration sensors. Owing to the nature of using human subjects, the resulting data had high variance; therefore, each trial data set exhibits different features. The effects of each MSTS on body sway and the dynamics of body sway are discussed and evaluated here. Additionally, we propose a single trial analysis method based on the clustering based Gaussian mixture model and smoothing filtering.

立体映像視聴時における視覚誘導自己運動感に起因する重心動揺の特徴解析(視聴覚の基礎と応用,マルチモーダル,感性情報処理,一般)

立体映像視聴時における視覚誘導自己運動感に起因する重心動揺の特徴解析(視聴覚の基礎と応用,マルチモーダル,感性情報処理,一般)

Back off! The effect of emotion on backward step initiation

The distance regulation (DR) hypothesis states that actors are inclined to increase their distance from an unpleasant stimulus. The current study investigated the relation between emotion and its effect on the control of backward step initiation, which constitutes an avoidance-like behavior. Participants stepped backward on a force plate in response to neutral, high-arousing pleasant and high-arousing unpleasant visual emotional stimuli. Gait initiation parameters and the results of an exploratory analysis of postural sway were compared across the emotion categories using significance testing and Bayesian statistics. Evidence was found that gait initiation parameters were largely unaffected by emotional conditions. In contrast, the exploratory analysis of postural immobility showed a significant effect: highly arousing stimuli (pleasant and unpleasant) resulted in more postural sway immediately preceding gait initiation compared to neutral stimuli. This suggests that arousal, rather than valence, affects pre-step sway. These results contradict the DR hypothesis, since avoidance gait-initiation in response to unpleasant stimuli was no different compared to pleasant stimuli.

Body-worn triaxial accelerometer coherence and reliability related to static posturography in unilateral vestibular failure.

SUMMARYSince changes in vestibular function may be one cause of disequilibrium, major advances in measuring postural control and sensory integration in vestibular impairments have been achieved by using posturography. However, in order to overcome problems related to this type of technology, body-worn accelerometers (ACC) have been proposed as a portable, low-cost alternative to posturography for measurements of postural sway in a friendly and ecologic environment. Due to the fact that no study to date has shown the experimental validity of ACC-based measures of body sway with respect to posturography for subjects with vestibular deficits, the aim of the present study was: i) to develop and validate a practical tool that can allow clinicians to measure postural sway derangements in an otoneurological setting by ACC, and ii) to provide reliable, sensitive and accurate automatic analysis of sway that could help in discriminating unilateral vestibular failure (UVF) patients. Thus, a group of 13 patients (seven females, 6 males; mean age 48.6 ± 6.4 years) affected for at least 6 months by UVF and 13 matched healthy subjects were instructed to maintain an upright position during a static forceplate-based posturography (FBP) acquisition while wearing a Movit® sensor (by Captiks) with 3-D accelerometers mounted on the posterior trunk near the body centre of mass. Pearson product moment correlation demonstrated a high level of correspondence of four time-domain and three frequency-domain measures extracted by ACC and FBP testing; in addition, t-test demonstrated that two ACC-based time- and frequency-domain parameters were reliable measures in discriminating UVF subjects. These aspects, overall, should further highlight the attention of clinicians and researchers to this kind of sway recording technique in the field of otoneurological disorders by considering the possibility to enrich the amount of quantitative and qualitative information useful for discrimination, diagnosis and treatment of UVF. In conclusion, we believe the present ACC-based measurement of sway offers a patient-friendly, reliable, inexpensive and efficient alternative recording technique that is useful – together with clinical balance and mobility tests – in various circumstances, as well as in outcome studies involving diagnosis, follow-up and rehabilitation of UVF patients.

Analysis of Sway in Ballroom Dancing and Other Sports

Analysis of Sway in Ballroom Dancing and Other Sports

The Frequency Analysis of Body Sway Affected by Visual Information:A Study of the Postural Control Ability Among Toddlers

The Frequency Analysis of Body Sway Affected by Visual Information:A Study of the Postural Control Ability Among Toddlers

Postural Sway, Balance Confidence, and Fear of Falling in Women With Knee Osteoarthritis in Comparison to Matched Controls

BackgroundOsteoarthritis (OA) is a chronic degenerative disease that commonly affects the knee joints. Individuals older than 65 years of age with knee OA have a greater risk of falls. However, there has been limited examination of the parameters of postural sway (increased time, speed, and postural sway area [center of pressure{CoP}]), and OA of the knee. ObjectivesThe primary objective of this study was to determine whether the CoP variables discriminate between patients with knee OA and matched healthy volunteers, and to correlate the CoP variables with the Activities-Specific Balance Confidence Scale (ABC) and Falls Self-Efficacy Scale (FES). The secondary objective was to compare the CoP of older women with OA with a control group in bipedal support condition with eyes opened and closed. DesignCross-sectional study. SettingUniversity Biomechanics Laboratory. ParticipantsA total of 22 participants were divided into the following 2 groups of 11 participants each: an OA group (mean = 68 years, standard deviation = 7.4 years) and a control group (mean = 66 years, standard deviation = 4.4 years). MethodsStatic postural balance was measured by a portable force platform. Data were collected in both visual conditions (eyes open and closed), in random order. Three attempts of 30 seconds were allowed for each participant on the force platform, with a 1-minute interval between attempts. Main Outcome MeasureVariables were the CoP total displacement of sway (TDS, in centimeters), anteroposterior amplitude displacement (APAD, in centimeters), medial-lateral amplitude displacement (MLAD, in centimeters), total mean velocity (TMV, in centimeters per second), and dispersion of the center of pressure (AREA, in centimeters squared). ResultsThe postural sway analysis found statistically significant differences in the eyes open condition for the TDS (P = .020), APAD (P = .042), TMV (P = .010), and AREA (P = .045). In the discriminant analysis, none of the CoP variables were able to classify the groups (P = .15). The correlation analysis showed that only the AREA with eyes closed was associated with the ABC Scale (rho = −0.42). ConclusionsWomen with knee OA had greater postural sway when compared with a control group for the eyes open condition. CoP variables could not discriminate between the groups. The AREA was negatively correlated with the ABC Scale, when the eyes were closed. Level of EvidenceIII

Spectral analysis of the human body sway during standing on firm and compliant surfaces under different visual conditions

Effects of different visual conditions on the vertical posture maintenance were compared in subjects standing on a firm or compliant surface. These visual conditions included a motionless visual environment (MVE), eyes-closed condition (EC), and a virtual visual environment (VVE). The VVE consisted of two planes: the foreground and background. The foreground displayed a room window with adjacent walls, and the background was represented by an aqueduct with the adjacent landscape. The VVE was destabilized by inducing either the cophased or the antiphased relation between the foreground of the visual scene and the body sway. We evaluated changes in the amplitude spectra of two elementary variables calculated from the trajectories of the plantar center of pressure (CoP) displacements in the anteroposterior and lateral directions, namely, the trajectories for the center of gravity projections on the support (the CG variable) and the differences between the CoP and CG trajectories (the CoP–CG variable).The CG trajectory was considered as a controlled variable, and the difference between the CoP and CG trajectories were considered as a variable related to the body acceleration and reflecting changes in the resultant stiffness in ankle joints. The rootmean-square (RMS) values for the spectra of both variables calculated from the body sway in the anteroposterior direction in standing on a firm support decreased proportionately with antiphased relation between the foreground and the body sway and increased with the cophased relation, compared with the RMS calculated for the MVE conditions. RMS for the spectra of the CG variable in the cophased relation were nearly the same, as in standing with eyes closed (EC), while the RMS for the spectra of the CoP–CG variable were significantly less than with EC. The body sway during standing on a compliant support significantly increased in both the anteroposterior and the lateral directions under all visual conditions. RMS for the spectra of both variables with EC increased considerably higher than in the cophased relation. Furthermore, the RMS for the spectra of the CG variable calculated from the body sway in the lateral direction on a compliant support was substantially higher in the antiphased relation than in the cophased relation, whereas the RMS for the spectra of the CoP–CG variable under both conditions had similar values. The analysis of body sway and the results under some visual conditions have shown that the amplitude characteristics of the CG and CoP–CG variables changed not always proportionately with the passage from standing on a firm support to a compliant support. It is suggested that the found disproportion of changes in these two variables is probably associated with the contribution of another additional factor to the process of postural control, the passive elastic component of musculo-articular stiffness generated by fascial-tendon tissues.

What Could Posturography Tell Us About Balance Problems in Parkinson's Disease?

Impaired balance in patients with Parkinson's disease (PD) leads to loss of balance and frequent falls. Computerized dynamic posturography allows the assessment of stance tasks whereas mobile posturography analyzes the balance in free-field conditions, where falls among PD patients commonly occur (e.g. sitting down or standing up). The aim of the present study is to assess postural stability in PD patients with both techniques. Prospective study. University Hospitals, ambulatory care (outpatient clinic). Thirty-three patients diagnosed with idiopathic PD. Balance assessment. Dizziness handicap inventory (DHI), activities-specific balance confidence scale (ABC), composite score of sensory organization test (SOT), results of free-field body sway analysis (standard balance deficit test (SBDT)), or geriatric SBDT. PD patients showed a significantly higher sway in the roll direction in almost all of the SBDT conditions. Also, pathological sway compared with normative values was more prominent in complex tasks. There is a significant correlation between the different objective variables of the postural study (SOT and SBDT) and the ABC, but not with the DHI. Finally, the percentage of PD patients with a pathological score in SOT-composite score was 54.5% whereas in SBDT-composite score it was significantly higher (93.9%). Mobile posturography is more accurate in depicting the reality of balance impairment in PD patients than platform posturography. Also, ABC relates better than DHI to the significant psychological consequences of balance impairments. An increased lateral trunk sway seems to be a key factor of postural instability in PD patients.