Sway Speed Research Articles

Postural motion perception during vestibular stimulation depends on the motion perception threshold in persistent postural-perceptual dizziness

Patients with persistent postural-perceptual dizziness (PPPD) perceive postural instability larger than the observed sway. It is unknown whether the concept of postural misperception prevails during vestibular stimulation and whether it may account for the unsteadiness patients complain during body movements. We tested the hypothesis of an abnormal sensory-perceptual scaling mechanism in PPPD by recording objective, perceived, and the reproduced postural sway under various standing conditions, modulating visual and proprioceptive input, by binaural galvanic vestibular stimulation (GVS). We related postural sway speed to individual vestibular motion perceptional thresholds and disease-related PPPD questionnaires in 32 patients and 28 age-matched healthy control subjects (HC). All participants showed normal vestibular function tests on quantitative testing at the time of enrollment. The perception threshold of GVS was lower in patients. Compared to HC, patients showed and perceived larger sway on the firm platform. With GVS, posturo-perceptual ratios did not show group differences. The ratio of reproduced to real postural sway showed no group differences indicating normal postural sway perception during vestibular stimulation. Noticeably, only in patients, reproduced postural instability became larger with lower individual thresholds of vestibular motion detection. We conclude that posturo-perceptual (metacognitive) scaling of postural control seems to be largely preserved in PPPD during GVS. Vestibular stimulation does not destabilize patients more than HC, even in challenging postural conditions. Low individual thresholds of vestibular motion perception seem to facilitate instability and postural misperception on solid grounds. This conclusion is important for an effective physical therapy with vestibular exercises in PPPD.

Influence of oral motor tasks on postural muscle activity during dynamic reactive balance.

Jaw clenching improves dynamic reactive balance on an oscillating platform during forward acceleration and is associated with decreased mean sway speed of different body regions. It is suggested that jaw clenching as a concurrent muscle activity facilitates human motor excitability, increasing the neural drive to distal muscles. The underlying mechanism behind this phenomenon was studied based on leg and trunk muscle activity (iEMG) and co-contraction ratio (CCR). Forty-eight physically active and healthy adults were assigned to three groups, performing three oral motor tasks (jaw clenching, tongue pressing against the palate or habitual lower jaw position) during a dynamic one-legged stance reactive balance task on an oscillating platform. The iEMG and CCR of posture-relevant muscles and muscle pairs were analysed during platform forward acceleration. Tongue pressing caused an adjustment of co-contraction patterns of distal muscle groups based on changes in biomechanical coupling between the head and trunk during static balancing at the beginning of the experiment. Neither iEMG nor CCR measurement helped detect a general neuromuscular effect of jaw clenching on the dynamic reactive balance. The findings might indicate the existence of robust fixed patterns of rapid postural responses during the important initial phases of balance recovery.

Application of modified Model Reference Adaptive Controller and Observer (MRACO) for speed control of an unmanned underwater vehicle

In this paper, a modified Model Reference Adaptive Controller and Observer (MRACO), including an integral term to handle external disturbances, is applied to control, independently, the surge and sway speeds of an unmanned underwater vehicle (UUV). The suitability of the method is shown in simulation and in an experiment on a real system where a use-case from aquaculture robotics is demonstrated. The results show that the modified MRACO method is capable of controlling the surge and sway speeds accurately despite being derived on a simplified model of the UUV system used.

The Performance of Discriminative Tracking Algorithms for the Sway Frequency Measurement of Betula platyphylla Sukaczev (Individual Branch and Tree) under Artificial and Natural Excitation

The sway frequency is an important component of the dynamic characteristics of trees. Video-based methods can be used to measure the sway frequencies of trees. The key to successfully measuring tree sway frequency using video methods lies in whether the tracking method employed is appropriate. Based on six algorithms, i.e., Boosting, TLD, MIL, KCF, MOSSE and CSR-DCF, the tracking performance and accuracy of tree sway frequency measurements were investigated under two conditions: artificial excitation and environmental excitation. The results show that the following: (1) In terms of the tracking speed of tree sway, MOSSE > KCF > CSR-DCF > Boosting > MIL > TLD. (2) The TLD algorithm is not suitable for tree sway tracking. Boosting, MIL, MOSSE, KCF and CSR-DCF can be used for tree sway tracking. (3) Boosting, MIL and MOSSE are suitable for measuring the sway frequency of artificially excited branches and environmentally excited trees. (4) KCF and CSR-DCF algorithms are not suitable for the measurement of branch sway frequency under artificial excitation conditions but can be used for the measurement of tree sway frequency under environmental excitation conditions. However, it should be noted that this experiment only takes a Betula platyphylla Sukaczev tree and a Betula platyphylla Sukaczev branch as the research object to verify the effectiveness and feasibility of each tracking method, and does not verify the generalization ability of the above methods (on multiple tree species and multiple trees).

Ship dynamics model identification based on Semblance least square support vector machine

In recent years, with the rapid development of Maritime Autonomous Surface Ships (MASS) in the industry and academia, using system identification method to build the accurate ship dynamics model has become a hotspot in this area, which is critical to achieve precise and robust ship motion control for safety and adaptive navigation of MASS. Therefore, a non-parametric and robust two-phase system identification method is proposed. Firstly, the improved complete ensemble empirical mode decomposition is introduced to filter datasets collected from model-scale free-running model tests. Secondly, Semblance least square support vector machine (S-LS-SVM) is proposed for the ship dynamics modeling based on the LS-SVM with the state-of-the-art Semblance kernel function. Compared with the traditional method, the Root Mean Square Error (RMSE) of overall prediction on the test dataset improves by 20.82%, 7.68%, and 58.19% for surge, sway, and yaw speed of target ship model. According to maneuverability simulation, it is verified that this method has better generalization performance and higher accuracy for the prediction of the ship’s heading angle and trajectory.

Quantitative Romberg on a Force Plate: Objective Assessment Before and After Surgery for Cervical Spondylotic Myelopathy.

Longitudinal observational cohort. The purpose of this study was to evaluate the utility of Quantitative Romberg measurements as pre-op and post-op balance outcome measures. Cervical spondylotic myelopathy (CSM) is characterized by balance deficiencies produced by impaired proprioception. Evaluation is subjective, and binary physical exam findings lack the precision to assess postoperative outcome improvement. CSM patients were prospectively enrolled to undergo preoperative and postoperative Quantitative Romberg tests on a force plate to record center of pressure (COP) motion for 30 seconds with eyes open followed by eyes closed. Revision cases were excluded. Kinematics of COP movement parameters were compared between preoperative and postoperative state for each patient. Twenty-seven CSM patients were enrolled and completed both pre/post-testing. The mean age was 60.0 years, with 13 (48%) males and 9 (33%) smokers. Mean number of surgical levels was 2.48. The minimum mean follow-up was six months. There was a statistically significant improvement in eyes closed after surgery compared with preoperative for total COP motion (523.44 vs. 387.00cm, P <0.001), average sway speed (17.41 vs. 13.00cm/s, P <0.001), and total lateral COP motion (253.44 vs. 186.70cm, P <0.001). There was no statistically significant improvement in the modified Japanese Orthopaedic Association (13.29 vs. 14.29, P =0.28). CSM balance findings on Quantitative Romberg testing significantly improve postoperatively in patients with CSM. These findings support this testing as representative of proprioceptive balance deficiencies seen in CSM. Quantitative Romberg may be used as an objective measure of clinical outcome and assist in stratification of surgical interventions, surgery timing, and technique.

Effects of noninvasive brain stimulation on dual-task performance in different populations: A systematic review.

Increasing research has investigated the use of noninvasive brain stimulation (NIBS) on augmenting dual-task (DT) performance. To investigate the effects of NIBS on DT performance in different populations. Extensive electronic database search (from inception to November 20, 2022) was conducted in PubMed, Medline, Cochrane Library, Web of Science and CINAHL to identify randomized controlled trials (RCTs) that investigated the effects of NIBS on DT performance. Main outcomes were balance/mobility and cognitive function under both single-task (ST) and DT conditions. Fifteen RCTs were included, involving two types of intervention techniques: transcranial direct current stimulation (tDCS) (twelve RCTs) and repetitive transcranial magnetic stimulation (rTMS) (three RCTs); and four different population groups: healthy young adults, older adults, Parkinson's disease (PD), and stroke. For tDCS, under DT condition, significant improvement in speed was only observed in one PD and one stroke RCT, and stride time variability in one older adults RCT. Reduction in DTC in some gait parameters was demonstrated in one RCT. Only one RCT showed significant reduction in postural sway speed and area during standing under DT condition in young adults. For rTMS, significant improvements in fastest walking speed and time taken to Timed-up-and-go test under both ST and DT conditions were observed at follow-up in one PD RCT only. No significant effect on cognitive function in any RCT was observed. Both tDCS and rTMS showed promising effects in improving DT walking and balance performance in different populations, however, due to the large heterogeneity of included studies and insufficient data, any firm conclusion cannot be drawn at present.

Receiver Operating Characteristic Analysis of Posture and Gait Parameters to Prevent Frailty Condition and Fall Risk in the Elderly

Prevention strategies should be constantly improved to manage falls and frailty in the elderly. Therefore, we aimed at creating a screening and predictive protocol as a replicable model in clinical settings. Bioimpedance analysis was conducted on fifty subjects (mean age 76.9 ± 3.69 years) to obtain body composition; then, posture was analysed with a stabilometric platform. Gait performance was recorded by a 10 m walking test, six-minute walking test, and timed up and go test. After 12 months, subjects were interviewed to check for fall events. Non-parametric analysis was used for comparisons between fallers and non-fallers and between able and frail subjects. ROC curves were obtained to identify the predictive value of falling risk and frailty. Path length (area under the curve, AUC = 0.678), sway area (AUC = 0.727), and sway speed (AUC = 0.778) resulted predictive factors of fall events (p &lt; 0.05). The six-minute walking test predicted frailty condition (AUC = 0.840). Timed up and go test was predictive of both frailty (AUC = 0.702) and fall events (AUC = 0.681). Stabilometry and gait tests should be, therefore, included in a screening protocol for the elderly to prevent fall events and recognize the condition of frailty at an early stage.

Improving the method of linear-quadratic control over a physical model of vessel with azimuthal thrusters

The object of this research is the algorithms for controlling large-scale models of sea-based vehicles (SBVs). The subject of the research is a linear-quadratic method for controlling a model of the propulsion complex with azimuthal thrusters (ATs) in the aft part. The problem is the solution between the interdependent throws of surge, sway, and yaw speeds predicted by the linear controller. Input signals are the rotational speeds and the angles of ATs propeller thrusts with respect to the diametrical plane of SBVs. During the simulation, step responses of a closed system for overload and rotation speed are compared. Simulation of speed jumps showed an adequate response, in contrast to the speed of rotation of ATs, which showed a greater impact on the system than the orientation of ATs. When modeling the rate of yaw, the behavior of the ATs angle did not correspond to its limitations inherent in the device rotating at the appropriate speed. It is concluded that this is the result of linearization of the actuators, and the proposed solution is to implement the strengthening of the task to better adapt to the rotating behavior of ATs. Despite these problems, the simulation showed the potential of the model and controller for use in similar situations. Several modifications are also offered to significantly improve the model and simulations. One of the main changes that could be made is the implementation of a predictive gain during the linearization of the ATs control system. The practical significance of the results obtained is the fact that the quadratic optimization model is an effective and reliable technique in the process of designing SBVs of various configurations of steering devices for optimal control

Characterization of Postural Control in Post-Stroke Patients by Musculoskeletal Simulation

An association is observed between the standing sway posture and falls in patients with stroke; hence, it is important to study their standing balance. Although there are studies on the standing balance in stroke patients, differences in control have not been adequately investigated. This study aims to propose a method to characterize the postural sway in standing stroke patients using a mathematical model. A musculoskeletal model and neural controller model were used to simulate ten stroke patients (five patients with cerebral hemorrhages and five patients with cerebral infarctions) and eight young healthy participants, and their data were monitored during quiet standing. The model parameters were adjusted by focusing on the maximum-minimum difference in sway, which was considered important in a previous study, and sway speed, which is frequently used in the analysis. The adjusted model parameters were subjected to dimension reduction using non-negative matrix factorization. Consequently, the sway characteristics of stroke patients were expressed as the magnitude of gain parameters related to the extension of the entire body. The results of this study demonstrated the possibility of representing the characteristics of postural sway as model parameters in stroke patients using a mathematical model. This characterization could lead to the design of individualized rehabilitation systems in the future.

Impaired postural control in diabetes-a predictor of falls?

People with type 1 diabetes (T1D) and type 2 diabetes (T2D) are at risk of falling, but the association with impaired postural control is unclear. Therefore,the aim was to investigate postural control by measuring the center of pressure (CoP) during quiet standing and to estimate the prevalence ratio (PR) of falls and the fear of falling among people with diabetes compared to controls. In a cross-sectional study, participants with T1D (n = 111) and T2D (n = 106) and controls without diabetes (n = 328) were included. Study procedures consisted of handgrip strength (HGS), vibration perception threshold (VPT), orthostatism, visual acuity, and postural control during quiet stance measured by CoPArea (degree of body sway) and CoPVelocity (speed of the body sway) with "eyes open," "eyes closed" in combination with executive function tasks. A history of previous falls and fear of falling was collected by a questionnaire. CoPArea and CoPVelocity measurements were analyzed by using a multiple linear regression model. The PR of falls and the fear of falling were estimated by a Poisson regression model. Age, sex, BMI, previous falls, alcohol use, drug, HGS, VPT, orthostatism, episodes of hypoglycemia, and visual acuity were covariatesin multiple adjusted analyses. Significantly larger mean CoPArea measures were observed for participants with T1D (p = 0.022) and T2D (0.002), whereas mean CoPVelocity measures were only increased in participants with T2D (p = 0.027) vs. controls. Additionally, T1D and T2D participants had higher PRs for falls (p = 0.044, p = 0.014) and fear of falling (p = 0.006, p < 0.001) in the crude analyses, but the PRs reducedsignificantly when adjusted for mean CoPArea and mean CoPVelocity, respectively.Furthermore,multiple adjustedPRsweresignificantly higher than crude the analyses. CONCLUSION: Impaired postural control during quiet stance was seen in T1D and T2D compared with controlseven in the occurrence of well-known risk factors.and correlated well with a higher prevalence of falls.

Effect of cooling on static postural balance while wearing firefighter’s protective clothing in a hot environment

Objectives. Postural imbalance can result from hyperthermia-mediated muscular fatigue and is a major factor contributing to injuries from falling. The objective of this study was to investigate the effect of exercise-induced hyperthermia and the impact of cooling on postural balance while wearing firefighters’ protective clothing (FPC) in a hot environment. Methods. A portable force platform measured postural balance characterized by postural sway patterns using center of pressure metrics. Twelve healthy, physically fit males were recruited to stand on the force platform once with eyes open and once with eyes closed before and after treadmill exercise (40% V ˙ O 2 max ) inside an environmental chamber under hot and humid conditions (30 °C and 70% relative humidity) while wearing FPC. Subjects participated in two randomly assigned experimental phases: control and cooling intervention. Results. A significant increase in physiological responses and postural balance metrics was observed after exercising in the heat chamber while wearing FPC. Cooling resulted in a significant effect only on postural sway speed after exercise-induced hyperthermia. Conclusions. Hyperthermia can negatively alter postural balance metrics, which may lead to an increased likelihood of falling. The utilization of body cooling reduced the thermal strain but had limited impact on postural balance stability.

PREFACE

PREFACE

Postural control through force plate measurements in female AIS patients compared to their able-bodied peers

The present understanding of the mechanisms responsible for postural deficit in adolescent idiopathic scoliosis (AIS) is still insufficient. This is important because some authors see one of the causes of this disease in the impaired postural control. Moreover, there is a reciprocal link between the level of postural imbalance and the clinical picture of these people. Therefore, we compared the center-of-pressure (COP) indices of 24 patients with AIS to 48 controls (CON) during four 20-s quiet stance trials with eyes open (EO) or closed (EC) and on firm or foam surface. This included sway amplitude, speed, sample entropy and fractal dimension. AIS had poorer postural steadiness only in the most difficult trial. In the remaining trials, AIS did as well as CON, while presenting a greater COP entropy than CON. Thus, the factor that made both groups perform equally could be the increased sway irregularity in AIS, which is often linked to higher automaticity and lower attention involvement in balance control. After changing the surface from hard to foam, puzzling changes in sway fractality were revealed. The patients decreased the fractal dimension in the sagittal plane identically to the CON in the frontal plane. This may suggest some problems with the perception of body axes in patients and reveals a hitherto unknown cause of their balance deficit.

Proprioceptive manipulations in orthograde posture modulate postural control in low back pain patients: a pilot study

As we stand upright, perceptual afferences are crucial to successfully help generating postural motor commands. Non-Specific Low Back Pain patients frequently demonstrate a lack of proprioceptive acuity, often translating into postural control deficiencies. For the first time, to our knowledge, we studied the postural effects of proprioceptive manipulations in orthograde posture on Non-Specific Low Back Pain patients. Using static posturography recordings, we computed sway speed, speed variance, and the main direction of sway. We also addressed the patient’s subjective feedbacks after being manipulated. Five minutes after the proprioceptive manipulations, our results revealed decreased speed and speed variance outcomes, but the main direction of sway was not modulated. Furthermore, after the proprioceptive manipulations, the patients also self-reported improved clinical outcomes. These findings provide new knowledge opening new fields of research as well as potential treatment strategies in Low Back Pain patients.

Change in Turning Ability According to the Side Fin Angle of a Ship Based on a Mathematical Model

In general, the effect of roll motion is not considered in the study on maneuverability in calm water. However, for high-speed twin-screw ships such as the DTMB 5415, the coupling effects of roll and other motions should be considered. Therefore, in this study, the estimation of maneuverability using a 4-degree-of-freedom (DOF; surge, sway, roll, yaw) maneuvering mathematical group (MMG) model was conducted for the DTMB 5415, to improve the estimation accuracy of its maneuverability. Furthermore, a study on the change in turning performance according to the fin angle was conducted. To accurately calculate the lift and drag forces generated by the fins, it is necessary to consider the three-dimensional shape of the wing, submerged depth, and effect of interference with the hull. First, a maneuvering simulation model was developed based on the 4-DOF MMG mathematical model, and the lift force and moment generated by the side fins were considered as external force terms. By employing the CFD model, the lift and drag forces generated from the side fins during ship operation were calculated, and the results were adopted as the external force terms of the 4-DOF MMG mathematical model. A 35° turning simulation was conducted by altering the ship’s speed and the angle of the side fins. Accordingly, it was confirmed that the MMG simulation model constructed with the lift force of the fins calculated through CFD can sufficiently estimate maneuverability. It was confirmed that the heel angle changes according to the fin angle during steady turning, and the turning performance changes accordingly. In addition, it was verified that the turning performance could be improved by increasing the heel angle in the outward turning direction using the side fin, and that the sway speed of the ship during turning can affect the turning performance. Hence, it is considered necessary to study the effect of the sway speed on the turning performance of a ship during turning.

AGE-RELATED DIFFERENCES IN STATIC POSTURAL BALANCE IN KOREAN ELDERLY ADULTS

Poor postural balance has been related to falls in older people. Although fall rates increase with age, age-related declines in postural balance of older people are still unclear. The goal of this study was to investigate age-related changes in the static postural balance ability of Korean elderly adults. Three hundred and eighty-nine normal elderly adults with ages ranging from 57 years to 87 years participated in this study. All elderly adults were instructed to stand in their preferred natural stance on a self-developed force platform. As postural sway variables, peak frequency, mean frequency, mean velocity, and mean distance were calculated from the center of pressure (COP) trajectories in both the medio-lateral (ML) and antero-posterior (AP) directions. The mean velocity in the older-elderly was significantly faster compared to those of the other age groups particularly in the AP direction ([Formula: see text]). In both the ML and AP directions, the older-elderly group showed a greater mean distance compared to the other age groups ([Formula: see text]). Conversely, no significant age group differences were found in mean frequency and peak frequency ([Formula: see text]). Our results mean that the older-elderly group showed postural balance with faster AP sway speed and overall sway size. The results of our study help in the understanding of age-related declines in postural balance for the prevention of falls and the development of a regression model for normative postural balance ability in Korean elderly adults.

Iteratively weighted dynamic modeling of four degrees of freedom motion for marine surface vehicles for k-step ahead prediction

Estimating surge, sway, roll, and yaw motions in marine vehicles are essential for many different reasons, such as maneuvering, dynamic positioning, control, and safety. In this article, an iterative-weighted model is presented for predicting marine vehicle's motions. Surge, sway, roll, and yaw speeds are used as input/output pairs, rudder and throttle references are also used as inputs. By using these input-output relations as training data, an iteratively weighted modeling algorithm is developed. The iteratively weighted model is then used for k-step ahead prediction for different maneuvering scenarios in calm waters. Estimation results are validated with varying scenarios of maneuvering to show the generalization of iteratively progressed model results. The presented work aims to bring a different perspective from a practical use viewpoint of a dynamic model of the platform without knowing the structure of the model, where only needed information are the excitation inputs and required outputs. Therefore, the presented approach has the flexibility to define input and output variables so that it can be configured for the desired application and has the potential to be extended on purpose, increasing the precision and reliability of surface/underwater vehicle's control as well as unmanned vehicles.

Objective assessment of the functional status of stroke patients: Can comprehensive rehabilitation treatment improve their functional efficiency?

Abstract Study aim: To check if the short rehabilitation treatment (3 weeks) complemented by complex rehabilitation on advanced equipment improves the functional status of chronic stroke patients; and which clinical and objective parameters can be used to assess the efficacy of such treatment. Material and methods: 28 patients 3 to 6 months after the stroke. They participated in 3 weeks rehabilitation program in Rehabilitation Hospital. This program was supplemented by rehabilitation on: Zebris treadmill, ALFA and GAMMA platform, Biodex Balance System SD, the Balance Tutor treadmill. Their functional status was assessed by: Scandinavian Stroke Scale (SSS), Timed-Up-And-Go test (TUG), balance tests on Zebris, instrumented gait analysis on BTS system. Results: The positive changes of the patients’ functional status were found in time of TUG test, in case of balance test for 95% of the ellipsoid area, lengths of major and minor axes of the ellipsoid, average sway speed, sway path length, total ground reaction force for left and right leg, and Gillette Gait Index in case of the gait analysis. Conclusions: The improvement of the functional status of chronic stroke patients after relatively short rehabilitation treatment was achieved, due to the addition to the standard rehabilitation treatment the program on the advanced technologically equipment.

The Cortical Dynamics of Dual-Task Standing in Older Adults

In older adults, the extent to which performing a cognitive task when standing diminishes postural control is predictive of future falls and cognitive decline. The cortical control of such “dual-tasking,” however, remains poorly understood. Electroencephalogram (EEG) studies have demonstrated that the level of attention and cognitive inhibitory activity during cognitive task performance can be quantified by changes in brain activity in specific frequency bands; namely, an increase in theta/beta ratio and a decrease in alpha-band power, respectively. We hypothesized that in older adults, dual-tasking would increase theta/beta ratio and decrease alpha-band power, and, that greater alpha-band power during quiet standing would predict worse dual-task performance. To test this hypothesis, we recorded postural sway and EEG (32-channels) in 30 older adults without overt disease as they completed trials of standing, with and without verbalized serial subtractions, on four separate visits. Postural sway speed, as well as absolute theta/beta power ratio and alpha-band power, were calculated. The theta/beta power ratio and alpha-band power demonstrated high test-retest reliability during quiet and dual-task standing across visits (intra-class correlation coefficients >0.70). Compared with quiet standing, dual-tasking increased theta/beta power ratio (p<0.0001) and decreased alpha-band power (p=0.002). Participants who exhibited greater alpha-band power during quiet standing demonstrated a greater dual-task cost (i.e., percent increase, indicative of worse performance) to postural sway speed (r=0.3, p=0.01). These results suggest that in older adults, dual-tasking while standing increases EEG-derived metrics related to attention, and, that greater cognitive inhibitory activity during quiet standing is associated with worse dual-task standing performance.