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Background Diabetic retinopathy is a principal cause of visual damage and blindness, in which laser treatment offers proven therapy. The progressive degeneration of the retina, secondary to diabetes, is believed to cause postural instability although this is not well documented. The aim of this research was to assess how optic flow stimuli contribute to the control of stance in people with impaired retinal functions. Research question Does the different retinal functionality correspond to different specific patterns of movements and muscles recruitment? Methods Postural mechanisms and motor strategies were measured by testing subjects in quiet stance on a force platform with surface electromyography under different optic flow stimulations. Root mean square values of the center of pressure time-varying signals and normalized EMG values were used to evaluate the postural sway. Results People with diabetic retinopathy, and to a greater extent laser group, were more unstable than healthy subjects. The greater amplitude of the body sway observed in the retinopathy group, and especially in the laser group, could be an expression of the difficulty for this population in processing this kind of visual information. Significance The increase in muscle activity indicates that there are musculoskeletal and postural changes in the lower limb musculature with increasing severity of diabetic retinopathy. An impaired retinal function might negatively affect postural control in a way that is dependent on the severity of retinal damage.

Objective: In this study, a novel hybrid predictive musculoskeletal model is proposed which has both motion prediction and muscular dynamics assessment capabilities. Methods: First, a two-dimensional (2D) skeletal model with 10 degrees of freedom is used to predict a symmetric lifting motion, outputting joint angle profiles, ground reaction forces (GRFs), and center of pressure (COP). These intermediate outputs are input to the scaled musculoskeletal model in OpenSim for muscle activation and joint reaction load analysis. Finally, the experimental validation is carried out. Results: Static Optimization tool is used to estimate the muscle activation data in OpenSim for the predicted lifting motion. Joint reaction forces of the lumbosacral joint (L5-S1) are generated using the OpenSim Joint Reaction analysis tool. The predicted joint angles, muscle activations, and peak joint reaction forces are compared with experimental data and data from literature to validate the hybrid model. Conclusion: The proposed hybrid model combines the skeletal models rapid motion prediction with OpenSims complex muscular dynamics assessment, and it can serve as a new generic tool for motion prediction and injury analysis in ergonomics and biomechanics.

Estimation of center of mass (CoM) and center of pressure (CoP) is critical for lower limb exoskeletons, prostheses, and legged robots. To meet the demand in these fields, this study presents a novel CoM and CoP estimation method for human walking through a wearable visual odometry (VO) device. This method is named VO-based estimation of CoM and CoP (VOECC). The methodology of VOECC is that the VO provides CoM trajectory estimation and the inherent walking dynamics model is exploited as prior knowledge for CoP trajectory estimation during human walking. Gait cycle is estimated based on the frequency analysis of the CoM trajectory, which is cropped into segments. Each segment mainly includes a half gait cycle. The segments are designed to be sliding to mitigate the disturbance of double-stance phase. For each segment, a quadratic programming (QP) problem is formulated to fit the CoM measurement with the theoretical walking dynamics model. The solution to this QP problem is an optimal gait parameters estimation, including CoP. Based on this solution, the human walking model with the CoM trajectory and CoP excursion is reconstructed. VOECC is evaluated experimentally where human walks on level ground and upstairs with VO device attached in front of the chest. The ground truth of CoM and CoP position is directly measured by the motion capture system and fully instrumented treadmill, respectively, and compared with the VOECC results. The proposed method is demonstrated to be effective in terms of wearable and extensible functionalities compared with the existing methods. Root-mean-squared errors between the CoP measured by fully instrumented treadmill and the CoP estimated by VOECC are evaluated and compared. This method has the potential to be extensible in lower limb rehabilitation, prosthetic, and legged locomotion fields.

Gait analysis is important in the field of healthcare, due to its close relationship to chronic diseases. With the development of the Internet of Health Things (IoHT), long-term gait monitoring and corresponding analysis can be performed remotely, reducing a patient’s time and traffic cost, while providing doctors more valuable gait information. In this paper, we present a piezoelectric insole gait monitoring system and its use in an IoHT architecture. Through the experimental results, the high detection sensitivity of 3.56 kPa and responsivity of 2.35 mV/kPa are achieved. Besides, computer software is developed with Qt platform, and the cloud database is also established. The plantar pressure distribution and center of pressure (CoP) trajectory are provided for further analysis, thereby satisfying the need for analyzing various diseases. Furthermore, the assembled system can continuously work for 16 hours, indicating its successful utilization when long-term gait monitoring is required. The presented work provides a feasible means for real-time, long-term, and accurate gait monitoring, prompting the development of gait analysis in the IoHT.

In the human hand, high-density contact information provided by afferent neurons is essential for many human grasping and manipulation capabilities. In contrast, robotic tactile sensors, including the state-of-the-art SynTouch BioTac, are typically used to provide low-density contact information, such as contact location, center of pressure, and net force. Although useful, these data do not convey or leverage the rich information content that some tactile sensors naturally measure. This research extends robotic tactile sensing beyond reduced-order models through (1) the automated creation of a precise experimental tactile dataset for the BioTac over a diverse range of physical interactions, (2) a 3D finite-element (FE) model of the BioTac, which complements the experimental dataset with high-density, distributed contact data, (3) neural-network-based mappings from raw BioTac signals to not only low-dimensional experimental data, but also high-density FE deformation fields, and (4) mappings from the FE deformation fields to the raw signals themselves. The high-density data streams can provide a far greater quantity of interpretable information for grasping and manipulation algorithms than previously accessible. Datasets, CAD files for the experimental testbed, FE model files, and videos are available at https://sites.google.com/nvidia.com/tactiledata .

Objectives Aim was to study the effect of monoski foot adjustment on kinematic and kinetic skiing parameters expressing sit skier’s technique. Design Independent variable was skier position with respect to bindings, acting on position of monoski foot sole clamp. Front (F), Mid (M) and Rear (R) settings changed with intervals of 20 mm. Course time, skiing speed, Ground Reaction Forces (GRFs) magnitude and point of application and damper stroke were dependent variables. Method A Paralympic monoski was equipped with a dynamometric binding plate measuring GRFs, roll and pitch moments. A Paralympic gold medalist (LW10-1) was involved. Skier trajectory and gates location were measured by a differential global navigation satellite system (GNSS) in steep and medium steep slope portions. The athlete performed two giant slalom runs for each foot setting the same day. Results GRFs, center of pressure (COP) and variations with foot settings were measured. Peaks values up to 3.36 times the total weight and damper speed of 675 mm/s in compression were found. Fastest runs, highest peak loads and best subjective ratings were recorded with F setting. COP mean values were influenced by foot adjustments. GRFs in left turns were 54% larger than in the right turns with F setting on steep slope. Conclusions The monoski foot adjustment influenced kinematic and kinetic skiing, with F setting showing best results. A skier asymmetric behavior between right and left turning was discovered. Findings can support the design of monoskis for a wider dissemination of Paralympic alpine sit skiing.

Computer interfaces with visual biofeedback (BF) capabilities in robot-assisted gait training applications can help design subject-specific therapies, define tasks based on the patient's condition, and increase the training outcomes. This study presents the use of an open-source real-time computer interface as a subject-specific visual BF and monitoring tool during gait. The interface is used in combination with a low-cost Wearable integrated Sensor System for Data Acquisition (WiSSDA), which consists of a 3-D printed lower extremity exoskeleton equipped with rotary encoders and pressure-sensitive insoles that measure biometric data during the gait cycle. The system obtains the lower extremities’ joint kinematics in the sagittal plane and estimates the vertical component of the foot contact forces and the foot center of pressure. Experimental tests were performed to evaluate different gait parameters using the computer interface as visual BF to guide the subject with reference boundaries of kinematic and kinetic parameters as target trajectories. The results were used to evaluate the interface's performance for specific gait tasks. The results demonstrated the capabilities of the computer interface combined with WiSSDA for robot-assisted gait training applications using BF; providing an open-source, portable, and ambulatory device that can be used in outdoor environments. The proposed system can help bring gait rehabilitation outside the laboratory environment, eliminating the need for stationary equipment.

The effect of propellant sloshing upon the stability of a liquid-propelled space vehicle in a high-g environment has been studied extensively. For a typical space vehicle with thrust vector control...

Traumatic brain injury (TBI) often results in balance impairment, increasing the risk of falls, and the chances of further injuries. However, the underlying neural mechanisms of postural control after TBI are not well understood. To this end, we conducted a pilot study to explore the neural mechanisms of unpredictable balance perturbations in 17 chronic TBI participants and 15 matched healthy controls (HC) using the EEG, MRI, and diffusion tensor imaging (DTI) data. As quantitative measures of the functional integration and segregation of the brain networks during the postural task, we computed the global graph‐theoretic network measures (global efficiency and modularity) of brain functional connectivity derived from source‐space EEG in different frequency bands. We observed that the TBI group showed a lower balance performance as measured by the center of pressure displacement during the task, and the Berg Balance Scale (BBS). They also showed reduced brain activation and connectivity during the balance task. Furthermore, the decrease in brain network segregation in alpha‐band from baseline to task was smaller in TBI than HC. The DTI findings revealed widespread structural damage. In terms of the neural correlates, we observed a distinct role played by different frequency bands: theta‐band modularity during the task was negatively correlated with the BBS in the TBI group; lower beta‐band network connectivity was associated with the reduction in white matter structural integrity. Our future studies will focus on how postural training will modulate the functional brain networks in TBI., EEG connectivity graph measures were studied in traumatic brain injury (TBI) during the balance perturbation task. TBI group showed altered brain activation and connectivity during the balance task. Graph‐theoretic measures showed that the task modulation of brain network segregation in alpha‐band was reduced in TBI and the network segregation in theta‐band was associated with postural instability in TBI.

Accelerations, ground reaction force data, and other quantitative data obtained from kinematic analyses of gait initiation serve as measures of dyskinesia in patients with Parkinson's disease. The objective of this study was to determine whether a separate center of pressure information could reveal new characteristics of reduced anticipatory postural adjustments in patients with Parkinson's disease.Ten healthy elderly subjects and 10 patients with Parkinson's disease participated in this study. Motions at gait initiation in response to a light signal to begin the task were analyzed. Anticipatory postural adjustments were characterized using trunk acceleration data and center of pressure displacement data.The separated center of pressure in patients with Parkinson's disease showed longer peak latency (Patients with Parkinson's disease experience asymmetry between the stance leg and stepping leg at gait initiation. These findings may help clinicians understand the changes to motor function in patients with Parkinson's disease and suggest strategies for improved rehabilitation training.

Background Early detection of delay or impairment in motor function is important to guide clinical management and inform prognosis during a critical window for the development of motor control in children. The purpose of this study was to investigate the ability of biomechanical measures of early postural control to distinguish infants with future impairment in motor control from their typically developing peers. Methods We recorded postural control from infants lying in supine in several conditions. We compared various center of pressure metrics between infants grouped by birth status (preterm and full term) and by future motor outcome (impaired motor control and typical motor control). Results One of the seven postural control metrics—path length—was consistently different between groups for both group classifications and for the majority of conditions. Conclusions Quantitative measures of early spontaneous infant movement may have promise to distinguish early in life between infants who are at risk for motor impairment or physical disability and those who will demonstrate typical motor control. Our observation that center of pressure path length may be a potential early marker of postural instability and motor control impairment needs further confirmation and further investigation to elucidate the responsible neuromotor mechanisms. Impact The key message of this article is that quantitative measures of infant postural control in supine may have promise to distinguish between infants who will demonstrate future motor impairment and those who will demonstrate typical motor control. One of seven postural control metrics—path length—was consistently different between groups. This metric may be an early marker of postural instability in infants at risk for physical disability.

Context: Chronic low-back pain (CLBP) may be associated with changes in postural balance in athletes as poor postural control during sports practice. Objective: To compare the postural control of athletes with and without CLBP during 2 one-legged stance tasks and identify the center of pressure (COP) cutoff values to determine the main differences. Designed: A cross-sectional study. Setting: Laboratory of functional evaluation and human motor performance. Participants: A total of 56 male athletes, 28 with and 28 without CLBP (mean age = 26 y). Intervention: The one-legged stance with knee extension and with the knee at 30° flexion tasks were measured and analyzed on a force platform. The participants completed three 30-second trials (30 s of rest between each trial). Main Outcome Measures: The COP parameters: the area of COP, mean COP sway velocity in both the anteroposterior and mediolateral directions, and total COP displacement were computed, and a receiver operating characteristics curve analysis was applied to determine the group differences. Results: Athletes with CLBP had poorer postural control (P d = 0.80).The knee extension cutoffs identified were >7.1 cm2 for the COP area, >2.6 cm/s for the COP sway velocity in the anterior-posterior direction, and >3.2 cm/s for the mediolateral direction. Whereas, the 30° knee flexion cutoffs were >10.9 cm2 for the COP area, >2.9 cm/s for the COP sway velocity in the anterior-posterior direction, and >4.1 cm/s for the mediolateral direction. Both measures showed enough sensitivity and specificity (ie, area under the curve = 0.88 in and 0.80, respectively) to discriminate both groups. Conclusions: The athletes with CLBP had poorer postural control than the healthy athletes and obtained specific cutoff scores from the COP values.

Background Previous research showed that standing on textured surfaces can improve postural control by adapting somatosensory inputs from the plantar foot. The additional stimulation of plantar cutaneous mechanoreceptors by a textured surface during single-leg stance on a balance board may increase afferent information to the central nervous system to accelerate muscular responses and to enhance their accuracy. The additional impact of textured surface during single-leg stance on a balance board on postural control and muscle activity is unknown. Research question To investigate the differences of a) postural control during single-leg stance on a textured balance board compared to a smooth balance board and b) activity of lower extremity muscles during single-leg stance on a textured balance board compared to a smooth balance board and the floor. Methods Twenty-six healthy adults (12 females, 14 males; mean age = 25.4 years) were asked to balance on their randomly assigned left or right leg on a force plate (floor; stable condition), a textured balance board and a smooth balance board (unstable conditions). Center of pressure (CoP) displacements (force plate, Bertec, 1000 Hz) and electromyographic activity (EMG) of eight leg muscles were measured and compared between conditions, respectively. Results Neither CoP-displacements, nor EMG activities differed significantly between the textured and the smooth balance board (p > 0.05). Significantly higher muscle activities (p Significance Single-leg stance using a textured balance board seems not to lead to reduced CoP-displacements compared to a smooth balance board. Muscle activation is significantly increased in both balance board conditions compared to the floor, however, it is not different when both balance board surfaces are compared. It could not be recommended to use a textured balance board for altering muscle activity and improving postural control during single-leg stance in favor of a smooth textured balance board.

Auditory feedback is a simple, low-cost training solution that can be used in rehabilitation, motor learning, and performance development. The use has been limited to the instruction of a single kinematic or kinetic target. The goal of this study was to determine if auditory feedback could be used to simultaneously train 2 lower-extremity parameters to perform a bodyweight back squat. A total of 42 healthy, young, recreationally active males participated in a 4-week training program to improve squat biomechanics. The Trained group (n = 22) received 4 weeks of auditory feedback. Feedback focused on knee flexion angle and center of pressure under the foot at maximum squat depth. The Control group (n = 20) performed squats without feedback. Subjects were tested pre, post, and 1 week after training. The Trained group achieved average target knee flexion angle within 1.73 (1.31) deg (P P P P

Objective To assess effects of 15 exoskeleton-assisted gait training sessions, reflected by the muscle strength of the lower limbs and by walking speed immediately after the training sessions and at the 6-week follow-up. Design Single-group longitudinal preliminary study. Setting Individuals with multiple sclerosis (MS) at a hospital neurology ward. Participants Participants (N=14) included women and men aged from 36-61 years, with Expanded Disability Status Scale scores from 5.0-6.5. Interventions Exoskeleton-assisted walk training. Main Outcome Measures Primary outcomes included dynamometric knee extensor and flexor strength (Biodex Pro4), postural balance, and center of pressure displacements (Zebris FMD-S). Secondary outcomes included walking speed measured with the timed 25-foot walk test and fatigue (Fatigue Severity Scale). Assessments were performed 4 times, that is, prior to the start of the program (T0), at the end of the physiotherapy without an exoskeleton (T1), at the end of the exoskeleton-assisted training (T2), and at 6-week follow-up (T3). Results At the end of exoskeleton-assisted gait training there was a statistically significant improvement in peak torque of knee extensor muscles compared with the period of exercise without an exoskeleton. No statistically significant change was identified in the value of peak torque of knee flexors at T1. Likewise, the assessment at T2 showed the change in peak torque of knee flexors was not significant. The participants presented significantly faster walking speed after exoskeleton-assisted gait training compared with T0 and T1. No improvement was found in body balance. The subjects reported lower fatigue after exoskeleton-assisted gait training; however, the differences between the assessments at T1 and T0 as well as at T2 and T1 were statistically insignificant. Conclusions Individuals with MS and severe gait impairment participating in exoskeleton-assisted gait training achieved significant improvement in lower-limb muscle strength and increase in walking speed, yet the effect was not long-lasting.

Background Assessing postural stability in Parkinson’s disease (PD) often relies on measuring the stepping response to an imposed postural perturbation. The standard clinical technique relies on a brisk backwards pull at the shoulders by the examiner and judgement by a trained rater. In research settings, various quantitative measures and perturbation directions have been tested, but it is unclear which metrics and perturbation direction differ most between people with PD and controls. Objectives (1) Use standardized forward vs. backward perturbations of a support surface to evaluate reactive stepping performance between PD and control participants. (2) Evaluate the utility of using principal components analysis to capture the dynamics of the reactive response and differences between groups. Methods Sixty-two individuals participated (40 mild-to-moderate PD, off medication). Standardized rapid translations of the support surface were applied, requiring at least one step, backward or forward, to restore balance. The number of steps taken and the projection of the first principal component (PC1) of the center of pressure (COP) time series were entered in linear repeated-measures mixed effect models. Results Forward falls required significantly fewer steps to recover than backward falls. PC1 captured more than half of the variance in the COP trajectory. Analysis of the PC1 projection revealed a significant interaction effect of group (PD vs. controls) by direction, such that there was a group difference in forward stepping, but not backward. Significance Forward reactive stepping in PD differed from controls more than backward-stepping. PC1 projections of the COP trajectory capture the dynamics of the postural response and differ between PD and controls.

Virtual reality environments can be manipulated allowing controlled visual disturbances. These environmental manipulations (textures, objects, and movements) can affect postural control by creating...

This study proposes a real-time sequential sensor fusion based gait pattern controller. During the walking cycle, the sensor data is analyzed and obtained by several inertial measurement units (IMUs) and pressure sensors on the robot. Besides, in order to model the correction values of the walking parameters, this approach applies long short-term memory (LSTM) to build a feedback system for a bipedal humanoid robot. For training the network, four sequential features including two-direction Center of Pressure (CoP) and two-direction acceleration are acquired by using pressure sensors and IMUs on the robot. While these features are mapped to the network inputs, the network output is mapped by the optimal solutions generated using particle swarm optimization (PSO). The proposed LSTM feedback network comprises four layers. The effect of the proposed methodology is first tested in a robot simulation environment and then tested on a real bipedal humanoid robot. The experimental results demonstrate that this methodology can make the humanoid robot perform better than when using a fixed gait. It also provides self-adjustment capability to the robot to enable it to avoid situations like falling.

In people with severe neuromotor deficits of trunk and lower extremities, regaining balance in standing is often performed in rehabilitation with manual assistance, rigid body supports or by the use of handrails. To investigate and further expand postural control training in standing, we developed a Robotic Upright Stand Trainer (RobUST). In this study, we used RobUST to deliver trunk perturbations while simultaneously providing postural assistive forces on the pelvis in 10 able-bodied adults. Posture control responses with 'pelvic support' was then compared to 'no support' and 'hand supported' standing, with and without assistance from RobUST. We characterize postural imbalance with kinematic displacements and center of pressure (COP) outcomes, such as amplitude and root mean square of the excursions of COP. Surface electromyography (sEMG) was also applied to investigate muscle control. We additionally investigated ground reaction and handrail forces during standing to analyze how postural strategies and muscle mechanisms with 'pelvic support' via RobUST would differ from standing with 'no support' and with the 'handrail support'. Our results show that during perturbations, pelvic assistive support decreased kinematic and COP excursions compared to standing with no support. The pelvic assistance from RobUST showed similar level of COP changes as the use of handrail support but without reducing muscle activity or ground reaction forces. As expected, the maximum level of postural stability was observed when participants used the handrail and received pelvic assistive forces. In conclusion, RobUST demonstrates potential as a training device since it enhances postural balance without significantly removing muscular control mechanisms that are of interest in re-training postural control strategies in standing.

Background Up to one-third of individuals with a recent spinal cord injury (SCI) and most of the individuals with an incomplete lesion are able to regain partial balance and walking ability after the first-year post-injury. However, most individuals experience injurious falls while standing and frequent losses of balance post-rehabilitation, which can result in physical injuries and a fear of falling. Research question Control of balance during quiet standing depends on the integration of sensory information. Since SCI causes sensory and motor impairments, understanding the underlying mechanisms of how postural control is regulated is of significant importance for targeted and guided rehabilitation post-SCI. Methods We characterized the impact of a variety of challenging conditions on the standing balance for eight participants with incomplete SCI with walking ability compared to twelve age-matched able-bodied individuals using a waist-mounted inertial measurement unit (IMU). We compared balance biomarkers derived from IMUs’ readouts under conditions that challenged balance by affecting somatosensory (i.e., standing on hard vs. foam surfaces) and visual (i.e., eyes open vs. closed) inputs. We performed a three-way ANOVA or a Kruskal-Wallis test to characterize changes in postural control post-SCI based on reliance on somatosensory and visual information using balance biomarkers. Results We observed a reduced stability performance, an increased control demand, and a less effective active correction post-SCI in all standing conditions. Due to impaired somatosensory feedback, individuals with incomplete SCI showed a higher and lower reliance on visual and somatosensory information, respectively, for maintaining balance (p Significance Using a single waist-mounted IMU, the proposed method could characterize standing balance in individuals with incomplete SCI compared to able-bodied participants. Having high clinical utility and sufficient resolution with discriminatory ability, our method could be used in the future to objectively evaluate the effectiveness of rehabilitative interventions on the balance performance of individuals with SCI.

INTRODUCTION: Atypical rearfoot eversion is an important kinematic risk factor in running-related injuries. Prominent interventions for atypical rearfoot eversion include foot orthoses, footwear, and taping, yet a running gait retraining is lacking. Therefore, the aim was to investigate the effects of changing mediolateral center of pressure (COP) on rearfoot eversion, subtalar pronation, medial longitudinal arch angle (MLAA), hip kinematics and vertical ground reaction force (vGRF).METHODS: Fifteen healthy female runners underwent gait retraining under three conditions. Participants were instructed to run normally, on the lateral (COP lateral) and medial (COP medial) side of the foot. Foot progression angle (FPA) was controlled using real-time visual feedback. 3D measurements of rearfoot eversion, subtalar pronation, MLAA, FPA, hip kinematics, vGRF and COP were analyzed. A repeated-measures ANOVA followed by pairwise comparisons was used to analyze changes in outcome between three conditions. Data were also analyzed using statistic parameter mapping.RESULTS: Running on the lateral side of the foot compared to normal running and running on the medial side of the foot reduced peak rearfoot eversion (mean difference (MD) with normal 3.3°, p SIGNIFICANCE: This study demonstrated that COP translation along the mediolateral foot axis significantly influences rearfoot eversion, MLAA, and subtalar pronation during running. Running with either more lateral or medial COP reduced or increased peak rearfoot eversion, peak subtalar pronation, and peak MLAA, respectively, compared to normal running. These results might use as a basis to help clinicians and researchers prescribe running gait retraining by changing mediolateral COP for runners with atypical rearfoot eversion or MLAA.

Postural stability is an important indicator of balance and is commonly evaluated in neurorehabilitation. We proposed a system based on a virtual reality (HTC Vive) system with a tracker at the lumbar area. The position data of the tracker were obtained through detection of the sensors on the tracker by the VR system. The reliability and validity of these sway parameters to measure postural stability were evaluated. Twenty healthy adults had their postural sway measured with this system and a force platform system under four stance conditions, with wide- or narrow-stance and eyes open or closed. The path data from both systems were computed to obtain the following parameters: the mean distance and the mean velocity in the medial-lateral and anterior-posterior directions and the 95% confidence ellipse area. The reliability of the Vive-based sway measures was tested with intraclass correlation coefficients (ICCs). The convergent validity was tested against the center of pressure (COP) parameters from the force platform system. Finally, the discriminative validity was tested for the above four conditions. The results indicated that the Vive-based sway parameters had moderate to high reliability (ICCs: 0.56 ~ 0.90) across four conditions and correlated moderately to very highly with the COP parameters ( ${r} = 0.420\,\,\sim \,\,0.959$ ). Bland-Altman plotting showed generally good agreement, with negative offset for the Vive-based sway parameters. The sway parameters obtained by the Vive-based system also discriminated well among the tasks. In conclusion, the results support this system as a simple and easy-to-use tool to evaluate postural stability with acceptable reliability and validity.

A force plate is one of the most popular tools for postural stability assessment. It decomposes the ground reaction force (GRF) applied to the human body into multiple force components to determine the center of pressure (COP), which is the point at which the GRF is applied. Many COP measures have been proposed to characterize postural stability. Despite postural stability being closely related to GRF components, the interactions between them have rarely been studied. By studying the correlation structure of these GRF components, we developed a set of features to assess postural stability. We determined the correlation matrix of these GRF components and subsequently solved the corresponding eigenvalue problem; we used the resulting eigenvalues to characterize postural stability. The effectiveness of the proposed features was demonstrated by using them to differentiate between individuals in two age groups: 18–24 and 65–73 years. Statistical test results showed that the correlation matrix eigenvalues of the two age groups differed significantly. The classification results demonstrated that most of the correlation matrix eigenvalues were more sensitive to age variations than one of the most reliable and accurate conventional COP features. Furthermore, by reducing the force sensing requirement from three-dimensional to one-dimensional by considering only the vertical GRF components, a simplified version of the proposed approach can be obtained, which could reduce the cost of the force plate system substantially.

Noisy galvanic vestibular stimulation (nGVS) involves the application of a weak, noisy, electrical current to the vestibular end organs and their afferent nerves, through electrodes placed bilaterally over the mastoid process. Center of pressure (COP) sway was shown to decrease during nGVS under conditions of static standing posture. However, whether nGVS can improve balance functions other than the static standing posture remains unclear. This study aimed to elucidate the effects of nGVS on COP sway during one-legged standing. We randomly assigned 36 participants to either a control group (sham stimulation), a 0.2 mA group (nGVS at 0.2 mA), or a 0.4 mA group (nGVS at 0.4 mA). All participants were measured for COP sway standing on one leg, with open eyes, both before and during stimulation. In the 0.2 mA group, the sway path length, mediolateral mean velocity, and anteroposterior mean velocity decreased during stimulation compared with before stimulation. Conversely, no significant differences in COP sway were detected for either the control group or the 0.4 mA group. The stimulation effects for all COP sway parameters were significantly higher in the 0.2 mA group than in either the control group or the 0.4 mA group. The results of this study suggested that nGVS not only decreases COP sway during static standing postures but can also reduce COP sway during one-legged standing.

The loss of somatosensory feedback after transfemoral amputation imposes a serious challenge in achieving postural stability. In the recent past, weight shifting exercises with fixed ankle joint have been reported useful in boosting the limit of stability (LOS) only in the sound limb; the LOS on the prosthetic limb did not improve. A fixed ankle joint restricts movement in the anterior-posterior direction at the ankle level. Thus, it may suppress the ability to move forward LOS despite awareness of center of pressure (COP) due to vibrotactile feedback. Therefore, it could have limited the improvement in the LOS of a prosthetic limb in previous studies. This article investigates this hypothesis by evaluating the effect of vibrotactile feedback in the LOS of transfemoral amputees with fixed as well as movable ankle joints. This evaluation is done during weight shifting exercises. Firstly, we developed an in-house COP guided vibrotactile sensory feedback system. Next, we recruited five transfemoral amputees to perform a weight-shifting exercise with a) fixed ankle joint (single-axis cushion heel (SACH) foot) and b) movable ankle joint (single-axis foot). Finally, we analyzed the recorded center of pressure trajectory signals for the limit of stability. The findings of repeated measures ANOVA showed a marginally significant interaction ( $\text{F}_{{(\text {1, 4})}}= {5.7}$ , $\text {p}={0.07}$ , $\eta \text {p}^{{2}}= {0.591}$ ) between ankle joint and feedback conditions during backward shifting in weight shifting exercise. Further analysis showed that during the backward shifting fixed ankle joint did not improve in the presence of vibrotactile feedback, while a marginally significant ( $\text {p}={0.14}$ ) improved LOS was observed in the movable ankle joint with feedback. The findings conclude that the vibrotactile feedback is more effective in transfemoral amputees with movable ankle joint compared with fixed ankle joint.

This research is dedicated to introducing a novel structure for small-sized solar sail by using rotatable vanes and reflectivity control devices. The overactuated design that is proposed for the so...

Sit-to-Walk (STW) is a critical task for daily independence, yet its two inherent destabilizing events (seat-off, walking initiation) may diminish postural stability under fast motion speed (FS). This study aimed at the FS effect on the STW spatial and temporal patterns, with a specific interest in the relative STW temporal pattern. The STW kinetics and kinematics were recorded (n=18 men, 20.7±2.0 years) at preferred and FS. Statistics included One-Way repeated measures ANOVA (SPSS 25.0, p≤0.05). The FS spatial pattern reveals a discontinuous mode of the forward ground reaction force, indicating a balance rather than a propulsive strategy during the Rising phase. The FS relative temporal pattern reveals the prolongation of the Leaning phase (most possibly due to the feet repositioning), the shortening of the Rising and the Walking phases, and a relative delay in the spatial variables (p≤0.05). Overall, the results do not allow the STW consideration at FS as a “magnified” with respect to force, or a “shrinked-in” with respect to time, copy of the preferred motion speed. As more generic and versatile than the absolute one, the relative temporal pattern may be used as a reference for a variety of populations.

Trim-tab is a device for controlling and stabilizing planing boats in different sea conditions. This paper presents to find dimensions of the trim-tab at various speeds of the boat to reach the minimum drag. The speed of the boat is from15 m/s to 30m/s. Drag of the boat is calculated by Stavisky’s method. The minimum drag is found based on the optimum the trim angle. A Matlab program code is prepared for these calculations and all the all results such as drag, dimensions of the trim-tab, longitudinal center of pressure and time angle at different speeds of the boat are presented and discussed.

Maintaining an optimal rolling of the foot over the ground is thought to increase the stability and efficiency of pathologic gait. Ankle-foot orthoses are often prescribed to improve gait mechanics in individuals with lower extremity injuries; however, their design may compromise how the foot rolls over the ground.The aim of this study was to investigate the effects of the sagittal plane ankle-foot orthosis alignment on roll-over shape and center of pressure velocity in individuals with lower limb reconstructions.Randomized cross-over study with a control group comparison.In total, 12 individuals with lower limb reconstruction who used a custom carbon ankle-foot orthosis and 12 uninjured controls underwent gait analysis. Ankle-foot orthosis users were tested in their clinically-provided ankle-foot orthosis alignment, with an alignment that was 3° more plantarflexed, and with an alignment that was 3° more dorsiflexed. Components of roll-over shape and center of pressure velocity were calculated from heel strike on the ankle-foot orthosis limb to contralateral heel strike.Roll-over shape radius was not affected by 3° changes to alignment and was not significantly different from controls. Aligning the ankle-foot orthosis in more dorsiflexion than clinically provided resulted in a smaller peak center of pressure velocity that occurred later in stance.Individuals using custom carbon ankle-foot orthoses can accommodate 3° alterations in the dorsiflexion or plantarflexion alignment.

Aim. The paper aims to study the dynamics of balance and coordination development through training with biofeedback. Material and methods. The Voronezh state institute students involved in shooting (n = 6) and swimming (n = 6) took part in the experiment. The mean age of participants was 19.5 ± 1.5 years. A one-month training was conducted with the use of 2 stabilographic simulators, namely Hunting and Stand shooting. Results. The results obtained in Stand shooting and Hunting simulators demonstrated an increase in points in both groups. However, in the group of shooters, the increase was statistically significant. An intergroup comparison at the end of the experiment was also statistically significant, which indicates a significantly greater improvement in the effectiveness of shooters. When assessing spectral indicators, a statistically significant improvement in the performance of shooters was revealed, which confirmed an increase in unconscious oscillations by 33.7 % along the frontal plane; as well as a decrease in oscillations associated with human physiology (heartbeat, respiration) by 75.4 % in the frontal plane and by 89 % in the sagittal plane. The intergroup comparison of data has statistically significant differences, which indicates the best effect of BFB training on the ability of shooters to control conscious and unconscious movements for maintaining frontal balance and sagittal oscillations associated with human physiology. Conclusion. As a result of the experiment, a positive effect of stabilometric simulators with biofeedback was revealed in terms of improving stability, coordination and the ability to control the center of pressure through the control of physiological processes that affect the shooting stance. Performance in the group of shooters was higher than in the group of swimmers

Spontaneous postural sway during quiet standing has been considered a simple output error of postural control. However, as postural sway and inherent body orientation evoke compensatory activity of the plantar flexors, they might contribute to blood circulation under gravitational stress via the muscle pump. Hence, the present study employed an external support device to attenuate the plantar flexor activity in supported standing (SS), to experimentally identify its physiological impact on blood circulation. Eight healthy young subjects performed two 5-min quiet standing trials (i.e., normal standing (NS) and SS), and the beat-to-beat interval (RRI) and blood pressure (BP) were compared between trials. We confirmed that postural sway and corresponding plantar flexor activity, quantified by the anteroposterior displacement of the foot center of pressure and lower back position with respect to the wall, and by the amplitude of electromyography and mechanomyography, respectively, were attenuated in SS, while mean body orientation angle and relative position of the BP sensor were comparable to NS. The 5-min averages of diastolic BP and mean arterial pressure during SS were significantly higher than during NS, while RRI and systolic BP did not change. These could be interpreted as an increase in peripheral vascular resistance; meanwhile, in NS, this effect was replaced by the muscle pump of the plantar flexors. The muscle contractions related to spontaneous postural sway and body orientation produce substantial physiological impact on blood circulation during quiet standing.

The purposes of the study were (1) to compare postural sway between participants with Parkinson’s disease (PD) and healthy controls and (2) to develop and validate an automated classification of PD postural control patterns using a machine learning approach. A total of 9 participants in the early stage of PD and 12 healthy controls were recruited. Participants were instructed to stand on a force plate and maintain stillness for 2 minutes with eyes open and eyes closed. The center of pressure data were collected at 50 Hz. Linear displacements, standard deviations, total distances, sway areas, and multiscale entropy of center of pressure were calculated and compared using mixed-model analysis of variance. Five supervised machine learning algorithms (ie, logistic regression, K-nearest neighbors, Naïve Bayes, decision trees, and random forest) were used to classify PD postural control patterns. Participants with PD exhibited greater center of pressure sway and variability compared with controls. The K-nearest neighbor method exhibited the best prediction performance with an accuracy rate of up to 0.86. In conclusion, participants with PD exhibited impaired postural stability and their postural sway features could be identified by machine learning algorithms.

The primary purpose of this study was to examine lateral deviations in center of pressure as a result of an extreme-duration load carriage task, with particular focus on heel contact. A total of 20 (n = 17 males and n = 3 females) soldiers from a special operation forces unit (body mass 80.72 [21.49] kg, stature 178.25 [8.75] cm, age 26 [9] y) underwent gait plantar pressure assessment and vertical jump testing before and after a 43-km load carriage event (duration 817.02 [32.66] min) carrying a total external load of 29.80 (1.05) kg. Vertical jump height decreased by 18.62% (16.85%) from 0.30 (0.08) to 0.24 (0.07) m, P P = .035, Glass delta = 0.44 and 1.28 [0.40] vs 1.46 [0.41] body weight, P = .015, Glass delta = 0.45, respectively) and increases in lateral center of pressure displacement were observed as a result of the load carriage task 14.64 (3.62) to 16.97 (3.94) mm, P

Postural stability deficits are commonly observed in cases of concussion. However, the objective duration in which impairments of standing postural stability remain following a concussion is often inconclusive. The present study was conducted to determine if prior history of concussion is associated with deficits in postural stability beyond the clinical determination of recovery. It was hypothesized that concussion history would be associated with decreases in static stability compared to individuals that have never sustained a concussion. Fifty-four healthy adults were recruited based on whether they reported sustaining one or more prior concussions (n = 27) or no history of concussion (n = 27). Participants were instructed to stand on a force platform to track center-of-pressure (CoP) during standing for thirty seconds under four conditions based on stance and number of tasks: (1) bipedal, single-task, (2) bipedal, dual-task, (3) unipedal, single-task, and (4) unipedal, dual-task. Results revealed that individuals with a history of concussion demonstrate significantly reduced postural stability under dual-task conditions as evidenced by increases in average displacements and elliptical area of postural sway as well as reductions in CoP sample entropy. However, there were no significant differences in CoP displacement or elliptical area between groups under single task conditions. Overall, these findings indicate that concussion is associated with impairments of maintaining standing postural stability that remain evident approximately 7 years following clinical resolution of the initial injury. The exacerbation of these impairments under dual-task conditions indicate that concussion can result in a reduced capacity to allocate proper attention resources to multiple concurrent objectives.

Objective To investigate postural control related to a lower limb exoskeleton (Chairless Chair) when (a) reaching for a working tool, and (b) an external perturbation occurs. Background Lower limb exoskeletons aiming to reduce physical load associated with prolonged standing may impair workers’ postural control and increase the risk of falling. Method Forty-five males were reaching for an object (3-kg dumbbell) at the lateral end of their reaching area without the exoskeleton in upright standing (STAND) and with the exoskeleton at a high (EXOHIGH.SEAT) and low sitting position (EXOLOW.SEAT). The task was performed with the object placed in three different angles (120°, 150°, and 180°) in the transversal plane. The minimum absolute static postural stability (SSABS.MIN) as the shortest distance (mm) of the center of pressure to the base of support border was measured (zero indicates risk of falling). Additionally, eight subjects were standing without the exoskeleton or sitting on it (EXOHIGH.SEAT and EXOLOW.SEAT) while being pulled backward. The tilting moment when subjects lost their balance was assessed. Results SSABS.MIN was lower when using the exoskeleton ( p < .05) but still about 17 mm. The location of the object to be reached had no influence. Tilting moments of less than 30 nm were sufficient to let people fall backward when sitting on the exoskeleton (50 nm for STAND). Conclusion Impairments in postural control by the exoskeleton may not be relevant when reaching laterally for objects up to 3 kg. When an external perturbation occurs, the risk of falling may be much higher; irrespective of factors like uneven or slippery flooring. Application The risk of falling using the exoskeleton seems to be low when reaching laterally for an object of up to 3 kg. In situations where, for example, a collision with coworkers is likely, this exoskeleton is not recommended.

Total ankle arthroplasty (TAA) is a common surgical approach for patients with end-stage ankle osteoarthritis (OA). However, very little is known about the path of the center of pressure (COP) of the foot, and thus important aspects of load transfer, muscle mechanical advantage, and balance, in patients before or after surgery. The objective of this study was to trace the pathway of the COP under the foot in patients with symptomatic ankle OA, comparing asymmetry between affected and unaffected limbs. From force plate data, proximo-distal and medio-lateral position of the COP beneath the foot were calculated and compared for the affected and unaffected foot in patients with unilateral ankle OA (N=93) before and after TAA. Gender and age at surgery had little or no effect in this study. Patients with ankle OA had minimal COP position asymmetry before surgery, and this asymmetry was reduced following surgery. Prior to surgery, patients had a slower walking speed and a shorter path of the COP which began relatively distal to the heel and ended relatively proximal to the hallux. TAA increased the proximo-distal distance the COP traveled under both the unaffected and affected foot, a pattern that was maintained for over two years post-surgery. TAA allows patients with ankle OA to maintain a longer COP path than they had before surgery on both sides that is closer to that reported for unaffected individuals, extending effectively from the heel to the hallux, potentially improving pedal mechanics. This article is protected by copyright. All rights reserved.

The purpose of this study was to determine what differences exist when performing grand plié with and without the barre. Differences in center of pressure (COP) sway, trunk kinematics, and lower extremity kinematics were used in this analysis for both first (P1) and fifth positions (P5). It was hypothesized that use of the barre would result in decreased COP sway, but increased asymmetries in trunk and lower extremity kinematics would be seen compared with the same movements performed without the barre in both positions. Sixteen collegiate dancers (1 male, 15 female) performed three trials of grand plié in P1 and P5 (right leg crossed in front) with or without the barre, for a total of 12 trials. For the barre condition (BC), participants demonstrated less time to complete grand plié, slightly less depth in grand plié, and decreased anterior-posterior (AP) sway compared to the without barre condition (WBC). The BC condition showed increased peak left trunk rotation, right knee flexion, decreased right and left peak hip flexion, and increased right hip abduction in both P1 and P5. Comparing P1 to P5, there was decreased AP sway, decreased peak left trunk rotation, decreased peak right and left hip flexion, increased left hip abduction, and decreased right knee flexion in both BC and WBC conditions. For the BC, there was increased right hip abduction in P1 compared to P5. Our results indicate that while use of the barre provides proprioceptive information, which helps dancers to control balance and learn a motor control strategy, grand plié should also be taught without the barre to challenge the dancer's balance control with different movement patterns in space.

Introduction: Postural control has two behavioral goals: postural balance and orientation, which are achieved through a dynamic relationship between sensory information and muscle activity. To maintain body balance, the vestibular, optical and proprioceptive systems must be fully functioning. Neuromuscular balance (NB), developed by François Soulier, is a non-manipulative method that involves applying a soft vibration or a micro-thrust with a small mechanical device to a joint or vertebra in order to induce realignment and readjustment. Objective: To identify the biomechanical effect of NB upon static balance and body oscillations of adults and the elderly through stabilometry. Methodology: In this interventional study, 20 healthy volunteers - 10 young adults (aged between 18 and 30 years old) and 10 elderly (aged between 60 and 80 years old) - were subjected to 10 consecutive weekly NB sessions. Stabilometry was assessed at baseline and after the 10th intervention (center of pressure (COP) behavior parameters: total area in mm2, laterolateral and anteroposterior width in mm). Results: Anteroposterior as well as total area oscillations significantly decreased in the adult population (p

A motor-assisted elliptical trainer is being used clinically to help individuals with physical disabilities regain and/or retain walking ability and cardiorespiratory fitness. Unknown is how the device's training parameters can be used to optimize movement variability and regularity. This study examined the effect of motor-assisted elliptical training speed as well as body weight support (BWS) on center of pressure (CoP) movement variability and regularity during training.CoP was recorded using in-shoe pressure insoles as participants motor-assisted elliptical trained at three speeds (20, 40 and 60 cycles per minute) each performed at four BWS levels (0 %, 20 %, 40 %, and 60 %). Separate two-way repeated measures ANOVAs (3 × 4) evaluated impact of training speed and BWS on linear variability (standard deviation) and non-linear regularity (sample entropy) of CoP excursion (anterior-posterior, medial-lateral) for 10 dominant limb strides.Training speed and BWS did not significantly affect the linear variability of CoP in the anterior-posterior or medial-lateral directions. However, sample entropy in both directions revealed the main effect of training speed (p 0.0001), and a main effect of BWS was observed in the medial-lateral direction (p = 0.004). Faster training speeds and greater levels of BWS resulted in more irregular CoP patterns.The finding that speed and BWS can be used to manipulate CoP movement variability when using a motor-assisted elliptical has significant clinical implications for promoting/restoring walking capacity. Further research is required to determine the impact of motor-assisted elliptical speed and BWS manipulations on functional recovery of walking in individuals who have experienced a neurologic injury or illness.

Introduction: Postural instability is one the most common disabling features in vestibular disorders. Objective: This study aimed to analyze the limit of stability and the influence of manipulation of visual, somatosensorial and visual–vestibular information on postural control in older adults with vestibular disorder, with and without a history of falls. Methods: Cross-sectional study. Participants – 76 elderly patients with vestibular disorder (G1, without falls; G2, with falls) and 41 healthy elderly subjects (control group; CG). Using posturography, analyzed were limit of stability area, body center of pressure, and velocity of oscillation in the standing position in 10 conditions, including open/closed eyes, unstable surface with eyes closed, saccadic and optokinetic stimuli, and visual–vestibular interaction. Results: Limit of stability area in CG was better compared with G1-2, and center of pressure values were worse in G1 than in CG. Center of pressure area in all conditions and velocity of oscillation in the following conditions: open/closed eyes, optokinetic stimulation, and visual–vestibular interaction showed worse values in G2 than in CG. Center of pressure area in the following conditions: open/closed eyes, saccadic and optokinetic stimuli, visual–vestibular interaction, and unstable surface with eyes closed showed worse values in G2 than in G1. Conclusion: Older adults with vestibular disorder presented reduced limit of stability and increased postural sway in the following conditions: conflict between visual and somatosensory information and visual–vestibular interaction. Deterioration in postural control was significantly associated with history of falls. Resumo: Introdução: Instabilidade postural é uma das características incapacitantes mais comuns nos distúrbios vestibulares. Objetivo: Analisar o limite de estabilidade e a influência da manipulação de informações visuais, somatossensoriais e visuais-vestibulares no controle postural em idosos com disfunção vestibular, com e sem histórico de quedas. Método: Estudo transversal. Participantes: 76 idosos com distúrbios vestibulares (G1, sem quedas; G2, com quedas) e 41 idosos saudáveis (grupo controle; GC). Com o uso da posturografia, foram analisadas a área do limite de estabilidade, centro de pressão e velocidade de oscilação na posição ereta em 10 condições, incluindo olhos abertos/fechados, superfície instável com olhos fechados, estímulos sacádicos e optocinéticos e interação visual-vestibular. Resultados: A área de limite de estabilidade no GC foi melhor comparada com o G1-2 e os valores do centro de pressão foram piores no G1 do que no GC. A área do centro de pressão em todas as condições e a velocidade de oscilação nas seguintes condições: olhos abertos/fechados, estímulo optocinético e interação visual-vestibular mostraram valores piores no G2 do que no GC. A área do centro de pressão nas seguintes condições: olhos abertos/fechados, estímulos sacádicos e optocinéticos, interação visual-vestibular e superfície instável com olhos fechados apresentou valores piores no G2 do que no G1. Conclusão: Idosos com disfunção vestibular apresentaram redução de limite de estabilidade e aumento da oscilação postural nas seguintes condições: conflito entre informação visual e somatossensorial e interação visual-vestibular. A deterioração no controle postural foi significantemente associada ao histórico de quedas.

Vertical posture of a standing subject with different orientations of one or both feet was studied. Symmetrical turn of both feet in a standing person led to an increase in the movement of the common center of pressure (CCP) and center of pressure (CP) of each foot. It is likely that, for the vertical position maintenance with symmetrical feet turn, the movement of the CPs of both feet was controlled simultaneously. During standing with the turn of one foot, the CP movement increased for the foot that retained orientation in the sagittal direction. For the turned foot the CP movement did not change. Thus, the turn of the foot of one leg changed the involvement of this leg in the upright position maintenance. The vertical posture was maintained mainly due to the position control of CP of the foot oriented in the sagittal direction. In addition, there was a change in the predominant direction of the CP movement relative to the foot orientation. When the foot was oriented in the sagittal direction, the predominant movement direction of the CP was turned outward. With the foot rotated outward, the predominant movement direction of the CP was turned inward. This change in the CP movement direction was observed in the cases of simultaneous turn of both feet as well as the turn of one foot. It can be assumed that, in standing, the balance-maintaining system controls the CP position of each leg and takes into account the torsional torque in the leg that occurs when the foot is rotated.

Background The variability of center of pressure (COP) is a measure of stability commonly examined during quiet standing. While more recent research has examined the variability of COP during walking, an adequate comparison between shod and unshod walking conditions has yet to be made. Research question What is the influence of athletic footwear on the variability of COP displacement during walking? Methods In this intervention study, twenty healthy women (age 18–30 years) completed 2, 10-min walking trials, 1 shod and 1 unshod, during which ground reaction forces (GRF) and COP movement were collected by an instrumental treadmill. COP displacement was examined in the medial-lateral (ML) and anterior-posterior (AP) directions after being divided into quadrants based on the peaks and trough of each steps associated vertical GRF. A single MANOVA was used to determine effects of footwear and limb for each quadrant with the probability of a Type I error set at 0.05. Results Significant differences in variability were seen between footwear conditions in all quadrants in the AP direction and quadrants one and four in the ML direction. These results may be due to the structure of footwear, including midsole cushioning, altering the dynamics of the foot during walking. Significance The results of this study suggest that on average, athletic footwear reduces the variability of COP displacement in ML and AP directions. This may have implications for populations for whom variability of COP is determined to be undesirable.

Virtual reality (VR) paradigms have proved to be a valid method to challenge and perturb balance. There is little consensus in the literature on the best protocol design to perturb balance and induce postural sway. Current VR interventions still lack a well-defined standardized metric to generate a virtual environment that can perturb balance in an efficacious, lifelike, and repeatable manner. The objective of this study was to investigate different configurations of amplitude and frequency in an anterior–posterior translation VR environment, that is, lifelike and scaled. Thirteen young adults with no conditions affecting balance were recruited. Balance was challenged by anterior–posterior sinusoidal movement of the lab image within the VR headset. Four different amplitudes of the sinusoidal movement were tested: 1, 5, 10, and 20 cm, with each amplitude being presented at 2 test frequencies : 0.5 and 0.25 Hz. Mean center of pressure velocity was significantly greater than baseline at 0.5 Hz and amplitudes of 10 and 20 cm. Mean center of pressure at approximate entropy was greater than baseline at 0.5 Hz and amplitude of 20 cm. The results suggest that sinusoidal movement of a realistic VR environment produces altered balance compared with baseline quiet standing, but only under specific movement parameters.

In this letter, we present a novel simplified approach for the center of pressure (CoP) estimation across different foot sizes using insole-based systems. A concept of insole templates is introduced to realize the adaptability of a single bunch of sensors across different template sizes. The proposed insole system is validated against the force platform during walking and weight shifting tasks. The experimental results show estimation accuracy with root mean square error of 1.98 ± 0.57 cm during walking and 1.28 ± 0.60 cm during weight shifting using UK7 insole size. The pearson correlation coefficient of 0.97 ± .03 during walking and 0.97 ± 0.05 during weight shifting was observed. The nonsignificant difference ( p >0.05) in root mean square error and Pearson's correlation coefficient between two significantly varying foot sizes (UK7 and UK10; p

Many people with stroke (PwS) demonstrate reduced balance and increased postural sway afterwards, which may ultimately lead to falls and injury. In this study, we aimed to better understand postural sway behavior and the mechanisms of balance control by examining balance in upright standing among PwS using methods from statistical mechanics i.e., the Stabilogram diffusion analysis (SDA). Center-of-pressure displacements while standing still were measured in 25 PwS and 11 healthy subjects. The traditional postural sway parameters were measured, and the SDA was used to characterize balance control in eyes-open and eyes-closed conditions. We found that PwS demonstrated significantly greater postural sway in the mediolateral and anterior–posterior directions and significantly higher SDA short-term diffusion coefficients and critical displacement in both eyes-open and eyes-closed conditions. There was also a significant group-by-condition interaction, whereas PwS demonstrated more sway in the eyes-closed condition. The SDA analysis revealed unstable behavior during short-term intervals, interpreted as larger distance of sway until closed-loop control took place. This significant group-by-condition interaction suggests that PwS have a significantly greater reliance on visual input compared with healthy subjects.