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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.

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.

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

Parkinson&rsquo, s disease (PD) is a neurodegenerative disorder that affects postural and cardiac autonomic control. However, since it is unknown whether these changes are associated, the objective of this study was to determine whether such a relationship exists. Twenty-three patients with PD participated. The RR intervals were recorded in different positions and heart rate variability (HRV) was analyzed. Postural sway was analyzed based on the center of pressure. No significant differences on HRV indices were induced by postural change. A correlation was found between these indices and postural control, high frequency (HF), and anterior-posterior (AP) root mean square (RMS-AP) (r = 0.422, p = 0.045), low frequency (LF)/HF, and AP mean velocity (r = 0.478, p = 0.021). A correlation was found between HRV induced by postural change and postural control, &Delta, LF/HF and RMS-AP (r = 0.448, p = 0.032), &Delta, LF/HF and ellipse area (r = 0.505, p = 0.014), &Delta, LF/HF and AP mean velocity (r = &minus, 0.531, p = 0.009), and &Delta, LF and AP mean velocity (r = &minus, 0.424, p = 0.044). There is an association between the autonomic and postural systems, such that PD patients with blunted cardiac autonomic function in both the supine and orthostatic positions have worse postural control.

Introduction Sensorineural hearing loss (SNHL) is a serious public health problem. Some evidence suggests a significant relationship between SNHL and balance disorders. The inability to maintain balance associated with SNHL while standing further increases the risk of falls among older people. Objective To investigate the association between SNHL on the postural balance in elderly individuals of both genders. Methods The sample consisted of 247 (166 women) physically independent elderly individuals, (mean age = 68.4 ± 6.0). The instruments used were the anamnesis and the pure tone audiometry for hearing loss, and for balance a force platform based in measures of center of pressure area and of sway velocity in the anteroposterior and mediolateral directions. Results Presence of hearing loss (HL) was observed in 68% of the participants. We observed a significant association between SNHL and characteristics of balance between the groups with and without HL for center of pressure (COP) area (p = 0.010), anteroposterior velocity (p = 0.001) and mediolateral velocity (p = 0.020). There was a significant difference between the gender groups for center of pressure area (p = 0.004), anteroposterior velocity (p = 0.001) and mediolateral velocity (p = 0.001) with better performance in the female group. Amongst men, there was a difference between the ones with HL and those without it, for COP area (p = 0.049). Conclusion In the present study, elderly individuals with SNHL exhibited more instability on the postural balance, and elderly men presented worse results in the test.

Background Individuals with autism spectrum disorder (ASD) show a reduced ability to maintain postural stability, though motor control mechanisms contributing to these issues and the extent to which they are associated with other gross motor activities (e.g., stepping) are not yet known. Methods Seventeen individuals with ASD and 20 typically developing (TD) controls (ages 6–19 years) completed three tests of postural control during standing. During the neutral stance, individuals stood with their feet shoulder width apart. During the Romberg one stance, they stood with feet close together. During the circular sway, participants stood with feet shoulder width apart and swayed in a circular motion. The standard deviation (SD) of their center of pressure (COP) in the mediolateral (ML) and anteroposterior (AP) directions and the COP trajectory length were examined for each stance. We also assessed mutual information (MI), or the shared dependencies between COP in the ML and AP directions. Participants also completed a stepping task in which they stepped forward from one force platform to an adjacent platform. The amplitude and duration of anticipatory postural adjustments (APAs) were examined, as were the maximum lateral sway, duration, and velocity of COP adjustments following the initial step. We examined stepping variables using separate one-way ANCOVAs with height as a covariate. The relationships between postural control and stepping measures and ASD symptom severity were assessed using Spearman correlations with scores on the Autism Diagnostic Observation Schedule–Second Edition (ADOS-2) and the Autism Diagnostic Interview-Revised (ADI-R). Results Individuals with ASD showed increased COP trajectory length across stance conditions (p = 0.05) and reduced MI during circular sway relative to TD controls (p = 0.02). During stepping, groups did not differ on APA amplitude (p = 0.97) or duration (p = 0.41), but during their initial step, individuals with ASD showed reduced ML sway (p = 0.06), reduced body transfer duration (p p = 0.02) compared to controls. Greater neutral stance COPML variability (r = 0.55, p = 0.02) and decreased lateral sway (r = − 0.55, p = 0.02) when stepping were associated with more severe restricted and repetitive behaviors in participants with ASD. Conclusions We found that individuals with ASD showed reduced MI during circular sway suggesting a reduced ability to effectively coordinate joint movements during dynamic postural adjustments. Additionally, individuals with ASD showed reduced lateral sway when stepping indicating that motor rigidity may interfere with balance and gait. Postural control and stepping deficits were related to repetitive behaviors in individuals with ASD indicating that motor rigidity and key clinical issues in ASD may represent overlapping pathological processes.

When people walk on a treadmill, significant differences exist in postural control if compared to walking on the ground. In this paper, a method combining linear and nonlinear analysis is proposed to evaluate the walking postural control ability. In this method, the movements of the upper body and the feet are analyzed separately, because these parts have more capacity to reflect the characteristics of people’s gait. On this basis, the linear and nonlinear indicators of each part are analyzed, and the postural control ability is evaluated. The method is validated by three healthy subjects walking on both the treadmill and the ground. In treadmill walking case, the results show a smaller upper trunk acceleration (UTa) in the anterior-posterior (AP) direction. In the foot movement analysis, there are significant differences in the performance indexes related to the center of pressure (CoP) when people are walking on the treadmill and the ground. When walking on the treadmill, the velocity, acceleration, and jerk of the CoP in the AP direction are smaller than those in the ground walking case. Besides, when people walk on treadmills at uniform speeds, their feet accelerate is less in the vertical direction, and they have shorter stride length (SL) and longer stride time (ST). These results suggest that people have better postural control when walking on a treadmill. This method can be used as a means of assessing people’s behavior when walking on various situations by evaluating their control posture ability.

This paper reports the kinematic, kinetic and electromyographic (EMG) dataset of human locomotion during level walking at different velocities, toe- and heel-walking, stairs ascending and descending. A sample of 50 healthy subjects, with an age between 6 and 72 years, is included. For each task, both raw data and computed variables are reported including: the 3D coordinates of external markers, the joint angles of lower limb in the sagittal, transversal and horizontal anatomical planes, the ground reaction forces and torques, the center of pressure, the lower limb joint mechanical moments and power, the displacement of the whole body center of mass, and the surface EMG signals of the main lower limb muscles. The data reported in the present study, acquired from subjects with different ages, represents a valuable dataset useful for future studies on locomotor function in humans, particularly as normative reference to analyze pathological gait, to test the performance of simulation models of bipedal locomotion, and to develop control algorithms for bipedal robots or active lower limb exoskeletons for rehabilitation., Measurement(s)kinematic data • kinetic data • electromyography • locomotor behavior trait • motion analysis dataTechnology Type(s)stereophotogrammetry • dynamometric force platform • electromyography device • multifactorial motion analysisFactor Type(s)type of locomotor task • age • sex • gait speed • body height • body weightSample Characteristic - OrganismHomo sapiens Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.11112980

[Purpose] This pilot study aims to determine whether improvements in postural sway, particularly among older adults, can be augmented immediately after training participants to activate and isolate the transverse abdominis (TrA) muscle. [Participants and Methods] Fifty six participants (in three age groups) took part in a single session TrA training intervention. Aspects of postural sway, balance and muscle activation patterns were measured before and after training and compared. [Results] There was significant improvement across four of six postural sway variables for the combined sample of all age groups. Older adults improved more than younger and middle-age participants in two important postural sway variables. No marked differences were evident in static reach distance across all age groups. There were no differences between groups with regard to surface electromyography (sEMG) amplitudes despite the emergence of different activation patterns among age groups. [Conclusion] Immediate effects were induced in postural sway measures after the single session training intervention. By improving neuromuscular control of the TrA and maximizing the efficiency of related proximal core muscles center of pressure (COP) sway velocities decreased during single limb standing (SLS).

Background: In the military, insufficient postural stability is a risk factor for developing lower extremity injuries. Postural stability training programs are effective in preventing these injuries. However, an objective method for the measurement of postural stability in servicemen is lacking. The primary objective of this study was to assess the influence of the number of repetitions, different foot positions and real-time visual feedback on postural stability, as well as their effects on the intrasession reliability of postural stability measurements in servicemen. The secondary objective was to assess the concurrent validity of the measurements. Methods: Twenty healthy servicemen between 20 and 50 years of age and in active duty were eligible for this quantitative, cross-sectional study. The measurements took place on a force plate, measuring the mean velocity of the center of pressure. The participants were asked to stand as still as possible in three different foot positions (wide stance, small stance, and on one leg), five times each for 45 s each time, and the measurements were performed with and without real-time visual feedback. Results: We observed a significant main effect of foot position (P < 0.001), but not of visual feedback (P = 0.119) or repetition number (P = 0.915). Postural stability decreased in the more challenging foot positions. The ICC estimates varied from 0.809 (one repetition in wide stance) to 0.985 (five repetitions on one leg). The common variance (R 2) between different foot positions without feedback varied between 0.008 (wide stance) and 0.412. Conclusions: To yield reliable data, wide-stance measurements should be conducted three times, and small-stance measurements and measurements on one leg should be conducted two times. The scores of a measurement in a particular foot position cannot predict the scores of measurements in other foot positions.

The goal of this study was to assess the effects of a supervised slackline training program in a group of soccer players. Thirty-four male division I under-19 players (16.64 ± 0.81 years) agreed to participate in the study. They were randomly divided into an experimental group (EG) and a control group (CG). The first group (EG) followed a 6-week supervised slackline training program (3 sessions/week; 5-9 min/session), while the CG performed only regular soccer training. Several variables were assessed in all participants: acceleration (20-m sprint test), agility (90º turns test), jump performance (squat jump, countermovement jump), and postural control (Center of Pressure ( CoP) testing: length, area, speed, Xmean, Ymean, Xspeed, Yspeed, Xdeviation, Ydeviation). Ratings of perceived exertion and local muscle ratings of perceived exertions were also recorded after each slackline training session. At post-tests, there was a significant increase only in the EG in acceleration, agility, squat jump and countermovement jump performance, as well as several CoP variables: area in the bipedal support on a firm surface, and length, area and speed in the left leg on a firm surface. The program was rated as “somewhat hard” by the players, while quadriceps, gastrocnemius and tibialis anterior were the most exerted muscles while slacklining. In conclusion, slackline training can be an effective training tool for young, high-level soccer players.

Balance confidence may reflect and affect balance performance, and this effect may be mediated by neural inputs to muscles. Available balance confidence scales are designed for older adults and individuals with pathological conditions. To eliminate ceiling effects for young adults and to enable the study of neural excitability in relation to confidence relevant to balance, we developed a Balance Confidence Scale (BCS), comprised of items depicting single limb stance conditions of varying difficulty. Motor cortical excitability was measured using transcranial magnetic stimulation (TMS). Preliminary construct validity was examined relative to balance performance, perceived steadiness, and previous physical activity in 20 young adults (25.7 ± 4.2 years; 11 females). The scale showed good internal consistency (Cronbach’s α = 0.81) and good test-retest reliability (ICC2,1 = 0.84) in a separate sample of 21 young adults (23.8 ± 4.6 years; 11 females). Balance confidence ranged from 34 to 79.6% in the validity sample. Confidence was correlated with performance indexed using center of pressure velocity (r = −0.62, p = 0.01) and area (r = −0.49, p = 0.04), in a relatively difficult standing condition with one leg positioned on an unstable spring. Perceived steadiness and overall physical activity were not correlated with confidence; however, participants with higher confidence scores reported greater experience with balance-related activities. Finally, confidence was related to indices of motor cortical excitability. The Balance Confidence Scale has sound preliminary validity and reliability and holds promise for the study of neural processes mediating social-cognitive influences on balance performance.

[Purpose] The aim of this study was to determine whether there are differences in postural stability control while leaning forward and backward between healthy elderly participants and elderly participants with cognitive impairment. [Participants and Methods] Postural stability was analyzed in 36 participants. According to the Mini-Mental State Examination results, participants were divided into the cognitive impairment group and the control group. A force plate was used to register the center of pressure in the sagittal and frontal plane, during two trials of maximum forward and backward body leaning. [Results] Significant differences were shown in both forward and backward leaning between the control and cognitive impairment groups. [Conclusion] The control of stability in the sagittal plane during maximum forward and backward lean of the body in cognitively impaired patients is similar to the results obtained by their healthy peers. However, individuals with cognitive impairment demonstrated larger lateral oscillations, which may be the reason for postural instability in this group, leading to an increased occurrence of falls.

Movement related beta band cortical oscillations, including beta rebound after execution and/or suppression of movement, have drawn attention in upper extremity motor control literature. However, fewer studies focused on beta band oscillations during postural control in upright stance. In this preliminary study, we examined beta rebound and other components of electroencephalogram (EEG) activity during perturbed upright stance to investigate supraspinal contributions to postural stabilization. Particularly, we aimed to clarify the timing and duration of beta rebound within a non-sustained, but long-lasting postural recovery process that occurs more slowly compared to upper extremities. To this end, EEG signals were acquired from nine healthy young adults in response to a brief support-surface perturbation, together with the center of pressure, the center of mass and electromyogram (EMG) activities of ankle muscles. Event-related potentials (ERPs) and event-related spectral perturbations were computed from EEG data using the perturbation-onset as a triggering event. After short-latency (

This study aimed at investigating the human ability to shift weight and maintain balance when driving a self-balancing personal mobility device (SPMD). In the experiment, participants performed a weight-shifting task, which is moving the center of pressure (COP) toward 15 targets comprising three distances and five directions. They were also given a maintaining balance task, which is holding the COP as close as possible to the same targets. The results showed that during the weight-shifting task, the target distance significantly increased the movement time and decreased the movement fluency and accuracy. In the balance control task, while the target distance significantly affected the postural stability, the target direction had no major effect, although there were interaction effects with the direction on the postural sway along the medial–lateral direction. It is expected that this study can help in understanding the balance control of humans and design safer SPMDs.

Finite element analysis (FEA) has been widely used to study foot biomechanics and pathological functions or effects of therapeutic solutions. However, development and analysis of such foot modeling is complex and time-consuming. The purpose of this study was therefore to propose a method coupling a FE foot model with a model order reduction (MOR) technique to provide real-time analysis of the dynamic foot function. A generic and parametric FE foot model was developed and dynamically validated during stance phase of gait. Based on a design of experiment of 30 FE simulations including four parameters related to foot function, the MOR method was employed to create a prediction model of the center of pressure (COP) path that was validated with four more random simulations. The four predicted COP paths were obtained with a 3% root-mean-square-error (RMSE) in less than 1 s. The time-dependent analysis demonstrated that the subtalar joint position and the midtarsal joint laxity are the most influential factors on the foot functions. These results provide additionally insight into the use of MOR technique to significantly improve speed and power of the FE analysis of the foot function and may support the development of real-time decision support tools based on this method.

The operation of wearable robots, such as gait rehabilitation robots, requires real-time classification of the standing or walking state of the wearer. This report explains a technique that measures the ground reaction force (GRF) using an insole device equipped with force sensing resistors, and detects whether the insole wearer is standing or walking based on the measured results. The technique developed in the present study uses the waveform length that represents the sum of the changes in the center of pressure within an arbitrary time window as the determining factor, and applies this factor to a conventional threshold method and an artificial neural network (ANN) model for classification of the standing and walking states. The results showed that applying the newly developed technique could significantly reduce classification errors due to shuffling movements of the patient, typically noticed in the conventional threshold method using GRF, i.e., real-time classification of the standing and walking states is possible in the ANN model. The insole device used in the present study can be applied not only to gait analysis systems used in wearable robot operations, but also as a device for remotely monitoring the activities of daily living of the wearer.

Background: Tracking the whole body center of mass (CoM) trajectory of balance-impaired individuals with a personalized model is useful in the development of customized fall prevention strategies. A personalized CoM estimate can be obtained using the statically equivalent serial chain (SESC) method, but the subject has to perform an identification procedure to determine the set of subject-specific SESC parameters. During this identification, the subject must hold a series of static poses, some of which are unsuitable for balanced-impaired individuals. Research question: Can non-static poses be used to replace the static poses during SESC parameter identification? Methods: A new method that extends the range of postures used to determine SESC parameters is presented. It takes advantage of CoM dynamics and can be executed by predominantly using dynamic motions with a few static frames. Furthermore, it is implemented using a Kalman filter to allow automatic switching between the dynamic and static models. The proposed method was tested with motion data obtained from seven healthy adults using a Vicon motion capture system and an AMTI force platform. Results: We found that dynamic motions could be used to estimate the SESC parameter and even reproduce ground reaction forces; however a small number of static poses are still required to determine the subject’s CoM position. The SESC-based CoM estimate obtained with this new approach was similar to that obtained using conventional full-static identification, except that the subject did not have to assume and maintain static poses. Significance: Our proposed extension of the conventional SESC method would facilitate its application in the field of neuro-rehabilitation, especially in patients who need balance training. This personalized CoM method could be applicable for patients who are not able to maintain a static posture. In addition, this method helps minimize the total identification time by increasing the number of usable recorded frames.

This paper presents a Control Allocation formulation aimed at altering the dynamic transient response of an aircraft by exclusive means of the aerodynamic effectiveness of its control effectors. This is done, for a given Flight Control System architecture and, optionally, closed-loop performance, by exploiting the concept of Control Center of Pressure, i.e. the center of pressure due to only aerodynamic control forces. Two formulations are proposed, and their advantages and disadvantages presented. The first is based on the straightforward augmentation of the control effectiveness matrix, the second on a weighting matrix to prioritize control effectors. The latter is implemented in three application studies on a box-wing aircraft configuration with redundant control surfaces: a simple pull-up maneuver, a trajectory tracking task, and an altitude holding task in turbulent atmosphere. Results show that the proposed formulation can significantly impact performance metrics that are closely related to the aircraft transient response. In the best case scenario, the aircraft is able to completely cancel the non-minimum phase behavior typical of pitch dynamics, hence achieving a sharp initial response to longitudinal commands. If compared to a standard Control Allocation algorithm, the proposed formulation results in improved tracking precision, better disturbance rejection, and a measurably improved feeling of comfort on board.

The present contribution aims to determine the dependence of the location of the non-dimensional center of pressure ( λ ) with orientation ( β ) for non-spherical particles of regular shape. Prolate and oblate ellipsoids as well as cylinders of various aspect ratios ( A R ) at several Reynolds numbers ( R e p ) have been considered. The required flow coefficients (drag, lift and pitching torque) were determined through DNS and validated with recently published results. The strategy for determining the center of pressure consisted in the evaluation of the pitching torque acting on the non-spherical particles resulting from the fluid-dynamic forces (i.e. drag and lift) and its comparison with the torque directly determined from DNS. The performed analysis did not only allow determining the shape of the curve λ ( β ) , but also revealed that the location of the center of pressure depends additionally on particle aspect ratio and Reynolds number. It is found that for all the particles considered, the position of the center of pressure at a fixed incidence angle displaces upstream of the geometrical center with increasing Reynolds number; additionally, it exhibits a non-monotonic behavior in dependence of the aspect ratio.

The purpose of this study is to investigate whether regional modulation of the ankle plantarflexors during standing was related to the recruitment of motor units associated with force direction. Fourteen participants performed a multi-directional leaning task in standing. Participants stood on a force platform and maintained their center of pressure in five different target directions. Motor unit firings were extracted by decomposition of high-density surface electromyograms recorded from the ankle plantarflexor muscles. The motor unit barycentre, defined as the weighted mean of the maximal average rectified values across columns and rows, was used to evaluate the medio-lateral and proximo-distal changes in the surface representation of single motor units across different leaning target directions. Using a motor unit tracking analysis, groups of motor units were identified as being common or unique across the target directions. The leaning directions had an effect on the spatial representations of motor units in the medial gastrocnemius and soleus (p 0.05). Motor unit action potentials were represented in the medial and proximal aspects of the muscles during forward vs. lateral leans. Further analysis determined that the common motor units were found in similar spatial locations across the target directions, whereas newly recruited unique motor units were found in different spatial locations according to target direction (p

The human ability of keeping balance during various locomotion tasks is attributed to our capability of withstanding complex interactions with the environment and coordinating whole-body movements. Despite this, several stability analysis methods are limited by the use of overly simplified biped and foot structures and corresponding contact models. As a result, existing stability criteria tend to be overly restrictive and do not represent the full balance capabilities of complex biped systems. The proposed methodology allows for the characterization of the balance capabilities of general biped models (ranging from reduced-order to whole-body) with segmented feet. Limits of dynamic balance are evaluated by the Boundary of Balance (BoB) and the associated novel balance indicators, both formulated in the Center of Mass (COM) state space. Intermittent heel, flat, and toe contacts are enabled by a contact model that maps discrete contact modes into corresponding center of pressure constraints. For demonstration purposes, the BoB and balance indicators are evaluated for a whole-body biped model with segmented feet representative of the human-like standing posture in the sagittal plane. The BoB is numerically constructed as the set of maximum allowable COM perturbations that the biped can sustain along a prescribed direction. For each point of the BoB, a constrained trajectory optimization algorithm generates the biped’s whole-body trajectory as it recovers from extreme COM velocity perturbations in the anterior–posterior direction. Balance capabilities for the cases of flat and segmented feet are compared, demonstrating the functional role the foot model plays in the limits of postural balance. The state-space evaluation of the BoB and balance indicators allows for a direct comparison between the proposed balance benchmark and existing stability criteria based on reduced-order models [e.g., Linear Inverted Pendulum (LIP)] and their associated stability metrics [e.g., Margin of Stability (MOS)]. The proposed characterization of balance capabilities provides an important benchmarking framework for the stability of general biped/foot systems.

Postural and walking instabilities contribute to falls in older adults. Given that shoes affect human locomotor stability and that visual, cognitive and somatosensory systems deteriorate during aging, we aimed to: (1) compare the effects of footwear type on stability and mobility in persons with a history of falls, and (2) determine whether the effect of footwear type on stability is altered by the absence of visual input or by an additional cognitive load. Thirty participants performed standing and walking trials in three footwear conditions, i.e. conventional shoes, minimal shoes, and barefoot. The outcomes were: (1) postural stability (movement of the center of pressure during eyes open/closed), (2) walking stability (Margin of Stability during normal/dual-task walking), (3) mobility (the Timed Up and Go test and the Star Excursion Balance test), and (4) perceptions of the shoes (Monitor Orthopaedic Shoes questionnaire). Participants were more stable during standing and walking in minimal shoes than in conventional shoes, independent of visual or walking condition. Minimal shoes were more beneficial for mobility than conventional shoes and barefoot. This study supports the need for longitudinal studies investigating whether minimal footwear is more beneficial for fall prevention in older people than conventional footwear.

Step-by-step foot placement control, relative to the center of mass (CoM) kinematic state, is generally considered a dominant mechanism for maintenance of gait stability. By adequate (mediolateral) positioning of the center of pressure with respect to the CoM, the ground reaction force generates a moment that prevents falling. In healthy individuals, foot placement is complemented mainly by ankle moment control ensuring stability. To evaluate possible compensatory relationships between step-by-step foot placement and complementary ankle moments, we investigated the degree of (active) foot placement control during steady-state walking, and under either foot placement-, or ankle moment constraints. Thirty healthy participants walked on a treadmill, while full-body kinematics, ground reaction forces and EMG activities were recorded. As a replication of earlier findings, we first showed step-by-step foot placement is associated with preceding CoM state and hip ab-/adductor activity during steady-state walking. Tight control of foot placement appears to be important at normal walking speed because there was a limited change in the degree of foot placement control despite the presence of a foot placement constraint. At slow speed, the degree of foot placement control decreased substantially, suggesting that tight control of foot placement is less essential when walking slowly. Step-by-step foot placement control was not tightened to compensate for constrained ankle moments. Instead compensation was achieved through increases in step width and stride frequency.

The purpose of this study was to analyze the body balance control of people walking and hurdling with or without a specific dominant leg in a monopodal position. This study involved 28 physical education students. The center of pressure (COP) was measured with a force plate under four conditions: single-leg standing (right and left) with eyes open and two upper limb positions (the arms were positioned in either a specific hurdle technique manner or alongside the body). A repeated measures analysis of variance (ANOVA) was conducted separately for five parameters of the COP in the medial-lateral (ML) and anterior-posterior (AP) directions under the four conditions. In the single-leg position, athletes without a dominant lower leg had better body balance than those with a dominant lower leg. The position of the upper limbs influenced the body position when hurdling. Accepting the correct position of the upper limbs helped to maintain balance (when overcoming hurdles). In hurdles, the position of the upper limbs should be improved to maintain postural stability and save this function for more demanding postural tasks.

The center of pressure (COP), which is defined as the point at which the resultant ground reaction force (GRF) is applied on a body, provides valuable information for postural stability assessment. This is because the fundamental goal of balance control is to regulate the center of mass (COM) of the human body by adaptively changing the position of the COP. By using Newtonian mechanics to develop two equations that relate the two-dimensional COP coordinates to the GRF components, one can easily determine the location of the COP using a force plate. An important property of these two equations is that for a given COP position, there exists an infinite number of GRF component combinations that can satisfy these two equations. However, the manner in which a postural control system deals with such redundancy is still unclear. To address this redundancy problem, we introduce four postural stability features by quantifying the coupling strengths between the COP coordinates and their GRF components. Experiments involving younger (18&ndash, 24 years old) and older (65&ndash, 73 years) participants were conducted. The efficacy of the proposed features was demonstrated by comparing the differences between variants of each feature for each age group (18&ndash, 24 and 65&ndash, 73 years). The results demonstrated that the coupling strengths between the anterior&ndash, posterior (AP) direction coordinate of the COP and its GRF components for the older group were significantly higher than those of the younger group. These experimental results suggest that (1) the balance control system of the older group is more constrained than that of the younger group in coordinating the GRF components and (2) the proposed features are more sensitive to age variations than one of the most reliable and accurate conventional COP features. The best testing classification accuracy achieved by the proposed features was 0.883, whereas the testing classification accuracy achieved by the most accurate conventional COP feature was 0.777. Finally, by investigating the interactions between the COP and its GRF components using the proposed features, we found that that the AP component of the GRF of younger people plays a more active role in balance control than that of the GRF of older people. Based on these findings, it is believed that the proposed features can be used as a set of stability measures to assess the effects on posture stability from various health-related conditions such as aging and fall risk.

Kinetics data such as ground reaction forces (GRFs) are commonly used as indicators for rehabilitation and sports performance, however, they are difficult to measure with convenient wearable devices. Therefore, researchers have attempted to estimate accurately unmeasured kinetics data with artificial neural networks (ANNs). Because the inputs to an ANN affect its performance, they must be carefully selected. The GRF and center of pressure (CoP) have a mechanical relationship with the center of mass (CoM) in the three dimensions (3D). This biomechanical characteristic can be used to establish an appropriate input and structure of an ANN. In this study, an ANN for estimating gait kinetics with a single inertial measurement unit (IMU) was designed, the kinematics of the IMU placed on the sacrum as a proxy for the CoM kinematics were applied based on the 3D spring mechanics. The walking data from 17 participants walking at various speeds were used to train and validate the ANN. The estimated 3D GRF, CoP trajectory, and joint torques of the lower limbs were reasonably accurate, with normalized root-mean-square errors (NRMSEs) of 6.7% to 15.6%, 8.2% to 20.0%, and 11.4% to 24.1%, respectively. This result implies that the biomechanical characteristics can be used to estimate the complete three-dimensional gait data with an ANN model and a single IMU.

Conventional biomechanical analyses of human movement have been generally derived from linear mathematics. While these methods can be useful in many situations, they fail to describe the behavior of the human body systems that are predominately nonlinear. For this reason, nonlinear analyses have become more prevalent in recent literature. These analytical techniques are typically investigated using concepts related to variability, stability, complexity, and adaptability. This review aims to investigate the application of nonlinear metrics to assess postural stability. A systematic review was conducted of papers published from 2009 to 2019. Databases searched were PubMed, Google Scholar, Science-Direct and EBSCO. The main inclusion consisted of: Sample entropy, fractal dimension, Lyapunov exponent used as nonlinear measures, and assessment of the variability of the center of pressure during standing using force plate. Following screening, 43 articles out of the initial 1100 were reviewed including 33 articles on sample entropy, 10 articles on fractal dimension, and 4 papers on the Lyapunov exponent. This systematic study shows the reductions in postural regularity related to aging and the disease or injures in the adaptive capabilities of the movement system and how the predictability changes with different task constraints.

Sub-threshold (imperceptible) vibration, applied to parts of the body, impacts how people move and perceive our world. Could this idea help someone who has lost part of their limb? Sub-threshold vibration was applied to the thigh of the affected limb of 20 people with unilateral transtibial amputation. Vibration conditions tested included two noise structures: pink and white. Center of pressure (COP) excursion (range and root-mean-square displacements) during quiet standing, and speed and spatial stride measures (mean and standard deviations of step length and width) during walking were assessed. Pink noise vibration decreased COP displacements in standing, and white noise vibration decreased sound limb step length standard deviation in walking. Sub-threshold vibration positively impacted aspects of both posture and gait; however, different noise structures had different effects. The current study represents foundational work in understanding the potential benefits of incorporating stochastic resonance as an intervention for individuals with amputation.

Postural instability is a major disabling feature in Parkinson’s disease (PD). We quantified the organization of leg and trunk muscles into synergies stabilizing the center of pressure (COP) coordinate within the uncontrolled manifold hypothesis in levodopa-naive patients with PD and age-matched control subjects. The main hypothesis was that changes in the synergic control of posture are present early in the PD process even before levodopa exposure. Eleven levodopa-naive patients with PD and 11 healthy controls performed whole-body cyclical voluntary sway tasks and a self-initiated load-release task during standing on a force plate. Surface electromyographic activity in 13 muscles on the right side of the body was analyzed to identify muscle groups with parallel scaling of activation levels (M-modes). Data were collected both before (“off-drug”) and approximately 60 min after the first dose of 25/100 carbidopa/levodopa (“on-drug”). COP-stabilizing synergies were quantified for the load-release task. Levodopa-naive patients with PD showed no COP-stabilizing synergy “off-drug”, whereas controls showed posture-stabilizing multi-M-mode synergy. “On-drug”, patients with PD demonstrated a significant increase in the synergy index. There were no significant drug effects on the M-mode composition, anticipatory postural adjustments, indices of motor equivalence, or indices of COP variability. The results suggest that levodopa-naive patients with PD already show impaired posture-stabilizing multi-muscle synergies that may be used as promising behavioral biomarkers for emerging postural disorders in PD. Moreover, levodopa modified synergy metrics differently in these levodopa-naive patients compared to a previous study of patients on chronic antiparkinsonian medications (Falaki et al. in J Electromyogr Kinesiol 33:20–26, 2017a), suggesting different neurocircuitry involvement.

The purposes of this study were to investigate the combined effects of age and obesity on gait and to analyze the relationship between age and obesity on ankle muscle activities during walking.4 groups; the young non-obese control group (CG, n = 50, age = 31.8 ± 4.5 years; BMI = 21.4 ± 2.2 kg/mCompared to OB, OBOA walked with higher CoP velocity, shorter stride, spending more time in support phase (p .05). These manifestations were associated with higher TA and SOL activities during the 1st double support (1st DS) and higher TA activity during the single support (SS) (p .05). Compared to OA, OBOA walked with lower GRFv, shorter and wider stride and spend more time in SU (p .05). Moreover, SOL, TA and GM activities of OBOA were higher compared to OAG during 1st DS, SS and 2nd Double support (2nd DS), respectively (p .05). During the 1ST DS, the stepwise multiple regression revealed that age accounted for 87% of the variance of TA activity. The addition of age contributed a further 16% to explain the variance TA activity. During the SS, age accounted for 64% and 46% of the variance of SOL and TA activity respectively. The addition of the body weight added further 15% and 66% of the variation of SOL and TA activity respectively. During the 2nd DS, body weight accounted for 86% of the variance and the addition of the body weight added a further 17% to explain the high level of GM.Age in obese adults and obesity in older adults should be considered separately to evaluate neuromuscular responses during walking and, subsequently, optimize the modality of treatment and rehabilitation processes in obese individuals in order to reduce and/or prevent the risk of falls.

Patients with bilateral vestibular hypofunction (BVH) often suffer from imbalance, gait problems, and oscillopsia. Noisy galvanic vestibular stimulation (GVS), a technique that non-invasively stimulates the vestibular afferents, has been shown to enhance postural and walking stability. However, no study has investigated how it affects stability and neural activities while standing and walking with a 2 Hz head yaw turning. Herein, we investigated this issue by comparing differences in neural activities during standing and walking with a 2 Hz head turning, before and after noisy GVS. We applied zero-mean gaussian white noise signal stimulations in the mastoid processes of 10 healthy individuals and seven patients with BVH, and simultaneously recorded electroencephalography (EEG) signals with 32 channels. We analyzed the root mean square (RMS) of the center of pressure (COP) sway during 30 s of standing, utilizing AMTI force plates (Advanced Mechanical Technology Inc., Watertown, MA, USA). Head rotation quality when walking with a 2 Hz head yaw, with and without GVS, was analyzed using a VICON system (Vicon Motion Systems Ltd., Oxford, UK) to evaluate GVS effects on static and dynamic postural control. The RMS of COP sway was significantly reduced during GVS while standing, for both patients and healthy subjects. During walking, 2 Hz head yaw movements was significantly improved by noisy GVS in both groups. Accordingly, the EEG power of theta, alpha, beta, and gamma bands significantly increased in the left parietal lobe after noisy GVS during walking and standing in both groups. GVS post-stimulation effect changed EEG activities in the left and right precentral gyrus, and the right parietal lobe. After stimulation, EEG activity changes were greater in healthy subjects than in patients. Our findings reveal noisy GVS as a non-invasive therapeutic alternative to improve postural stability in patients with BVH. This novel approach provides insight to clinicians and researchers on brain activities during noisy GVS in standing and walking conditions in both healthy and BVH patients.

This study aims to explore the effect of real-time visual feedback (VF) information of the pres-sure of center (COP) provided by intelligent insoles on balance training in a one leg stance (OLS) and tandem stance (TS) posture. Thirty healthy female college students were randomly assigned to the visual feedback balance training group (VFT), non-visual feedback balance training group (NVFT), and control group (CG). The balance training includes: OLS, tandem Stance (dominant leg behind, TSDL), tandem stance (non-dominant leg behind, TSNDL). The training lasted 4 weeks, the training lasts 30 minutes at an interval of 1 days. There was a sig-nificant difference in the interaction effect between Groups*Times of the COP parameters (p0.05) for TS. The main effect of the COP parameters was a significant difference in Times (p

Balance disorders are a risk factor for falls in the elderly population. Balance control involving the complex interaction among nervous, muscular, and sensory systems should be maintained to keep an upright posture and prevent falls. Vestibular sensation is one of the main senses essential for postural control. Noisy galvanic vestibular stimulation (nGVS) is a noninvasive stimulation method for vestibular organs. Recently, it has received increasing attention for the treatment of balance disorders. However, the effect of balance disorders on stimulus effect during the implementation of nGVS remains unknown. Therefore, this study aimed to determine the effects of different floor surface and visual conditions on the stimulus effects of the nGVS intervention. In this study, two experiments were conducted with 24 participants (12 each for Experiments 1 and 2). In Experiment 1, nGVS (0.4 mA; 0.1-640 Hz) was performed in the open-eyes standing position on a solid surface (nGVS condition) and in the closed-eye standing position on a foam rubber (nGVS + foam rubber condition). In Experiment 2, sham stimulation was performed under the same conditions as in Experiment 1, except for nGVS. Center of pressure (COP) sway was measured in all participants with them standing with open eyes at Pre and Post-1 (immediately after the intervention) and Post-2 (10 min after the measurement of post-1). In Experiment 1, under the nGVS condition, COP sway was significantly reduced in Post-1 and Post-2 compared with Pre. However, no significant difference was observed among Pre, Post-1, and Post-2 under the nGVS + foam rubber condition. Furthermore, the intervention effect was significantly greater in the nGVS condition than in the nGVS + foam rubber condition. In contrast, in Experiment 2, the COP sway did not significantly differ among Pre, Post-1, and Post-2 under either condition. Based on the results of this study, nGVS was found to be effective with open-eyes standing on a solid surface.

Background: Poor postural stability is associated with chronic ankle instability. Previous research showed an effect of foot type on postural stability. However, the specific effect of supinated feet remains unclear. Research question: Our study aimed to assess the effect of foot type on postural stability, while taking potential confounding effects of body mass and body height into account. Methods: Forty-three healthy participants between 18 and 40 years old performed barefooted single leg stance tests with eyes open (EO) and closed (EC) on solid ground, and on a balance board (BB). Foot type was determined from pressure recordings during gait, using the arch index. Ground reaction forces were measured using a force plate. Outcome measures were Center of Pressure Velocity (COPV) divided by body height, and the Horizontal Ground Reaction Force (HGRF) divided by body mass. Generalized Estimating Equations models assessed the differences between supinated, normal and pronated feet during EO, EC and on a BB. Results: During EO an interaction between supinated feet and body mass showed an increase of COPV with 0.03 × 10-2 1/s per kilogram of mass relative to normal feet (p = .03). During EC this interaction was more pronounced with 0.22 × 10-2 1/s increase per kilogram mass (p < .01). The HGRF did not differ between foot types in any of the conditions. Significance: Supinated feet have a larger increase in COPV compared to normal feet with increasing mass when standing on solid ground during EO and EC. This indicates that people with supinated feet and a higher mass are less stable during single leg stance. Level of evidence: Level 3, associative study.

It is well established that obesity is associated with deterioration in postural control that may reduce obese adults' autonomy and increase risks of falls. However, neuromuscular mechanisms through which postural control alterations occur in obese adults remain unclear.To investigate the effects of obesity on muscle coactivation at the ankle joint during static and dynamic postural control.A control group (CG; n = 20; age = 32.5 ± 7.6 years; BMI = 22.4 ± 2.2 Kg/m²) and an obese group (OG; n = 20; age = 34.2 ± 5.6 years; BMI = 38.6 ± 4.1 Kg/m²) participated in this study. Static postural control was evaluated by center of pressure (CoP) displacements during quiet standing. Dynamic postural control was assessed by the maximal distance traveled by the CoP during a forward lean test. Electromyography activity data for the gastrocnemius medialis (GM), soleus (SOL) and tibialis anterior (TA) were collected during both quiet standing and forward lean tests. Muscle activities were used to calculate two separate coactivation indexes (CI) between ankle plantar and dorsal flexors (GM/TA and SOL/TA, respectively).CoP displacements were higher in the OG than in the CG for quiet standing (p0.05). When leaning forward, the maximal distance of the CoP was higher in the CG than in the OG (p0.05). Only the CI value calculated for SOL/TA was higher in the OG than in the CG for both static and dynamic tasks (p0.05). The SOL/TA CI value in the OG was positively correlated with CoP displacements during quiet standing (r = 0.79; p0.05).Obesity increases muscle coactivation of the soleus and tibialis anterior muscles at the ankle joint during both static and dynamic postural control. This adaptive neuromuscular response may represent a joint stiffening strategy for enhancing stability. Consequently, increased ankle muscle coactivation could not be considered as a good adaptation in obese adults.

We study the foot plantar sensor placement by a deep reinforcement learning algorithm without using any prior knowledge of the foot anatomical area. To apply a reinforcement learning algorithm, we propose a sensor placement environment and reward system that aims to optimize fitting the center of pressure (COP) trajectory during the self-selected speed running task. In this environment, the agent considers placing eight sensors within a 7 × 20 grid coordinate system, and then the final pattern becomes the result of sensor placement. Our results show that this method (1) can generate a sensor placement, which has a low mean square error in fitting ground truth COP trajectory, and (2) robustly discovers the optimal sensor placement in a large number of combinations, which is more than 116 quadrillion. This method is also feasible for solving different tasks, regardless of the self-selected speed running task.

Stroke survivors adopt cautious or compensatory strategies for safe and successful obstacle crossing. Although knee extensor spasticity is a common independent secondary sensorimotor disorder post-stroke, few studies have examined the step adjustment and compensatory strategies used by stroke survivors with knee extensor spasticity during obstacle crossing. This study aimed to compare the differences in the kinematics and kinetics during obstacle crossing between stroke survivors with and without knee extensor spasticity, and to identify knee extensor spasticity-related differences in step adjustment and compensatory strategies. Twenty stroke subjects were divided into a spasticity group [n = 11, modified Ashworth scale (MAS) ≥ 1] and a non-spasticity group (n = 9, MAS = 0), based on the MAS score of the knee extensor. Subjects were instructed to walk at a self-selected speed on a 10-m walkway and step over a 15 cm obstacle. A ten-camera 3D motion analysis system and two force plates were used to collect the kinematic and kinetic data. During the pre-obstacle phase, stroke survivors with knee extensor spasticity adopted a short-step strategy to approach the obstacle, while the subjects without spasticity used long-step strategy. During the affected limb swing phase, the spasticity group exhibited increased values that were significantly higher than those seen in the non-spasticity group for the following measurements: pelvic lateral tilt angle, trunk lateral tilt angle, medio-lateral distance between the ankle and ipsilateral hip joint, hip work contributions, the inclination angles between center of mass and center of pressure in anterior-posterior and medio-lateral directions. These results indicate that the combined movement of the pelvic, trunk lateral tilt, and hip abduction is an important compensatory strategy for successful obstacle crossing, but it sacrifices some balance in the sideways direction. During the post-obstacle phase, short-step and increase step width strategy were adopted to reestablish the walking pattern and balance control. These results reveal the step adjustment and compensatory strategies for obstacle crossing and also provide insight into the design of rehabilitation interventions for fall prevention in stroke survivors with knee extensor spasticity.

Postural control provides insight into health concerns such as fall risk but remains relatively untapped as a vital sign of health. One understudied aspect of postural control involves transient responses within center of pressure (CoP) data to events such as vision occlusion. Such responses are masked by common whole-trial analyses. We hypothesized that the transient behavior of postural control would yield unique and clinically-relevant information for quiet stance compared to traditionally calculated whole-trial CoP estimates. Three experiments were conducted to test different aspects of this central hypothesis. To test whether transient, epoch-based characteristics of CoP estimates provide different information than traditional whole-trial estimates, we investigated correlations between these estimates for a population of young adults performing three 60-second trials of quiet stance with eyes closed. Next, to test if transient behavior is a result of sensory reweighting after eye closure, we compared transient characteristics between eyes closed and eyes open conditions. Finally, to test if there was an effect of age on transient behavior, we compared transient characteristics during eyes closed stance between populations of young and older adults. Negligible correlations were found between transient characteristics and whole-trial estimates (p>0.08), demonstrating limited overlap in information between them. Additionally, transient behavior was exaggerated during eyes closed stance relative to eyes open (p

In this work, we introduced a novel hybrid reinforcement learning scheme to balance a biped robot (NAO) on an oscillating platform, where the rotation of the platform is considered as the external disturbance to the robot. The platform had two degrees of freedom in rotation, pitch and roll. The state space comprised the position of center of pressure, and joint angles and joint velocities of two legs. The action space consisted of the joint angles of ankles, knees, and hips. By adding the inverse kinematics techniques, the dimension of action space was significantly reduced. Then, a model-based system estimator was employed during the offline training procedure to estimate the dynamics model of the system by using novel hierarchical Gaussian processes, and to provide initial control inputs, after which the reduced action space of each joint was obtained by minimizing the cost of reaching the desired stable state. Finally, a model-free optimizer based on DQN (λ) was introduced to fine tune the initial control inputs, where the optimal control inputs were obtained for each joint at any state. The proposed reinforcement learning not only successfully avoided the distribution mismatch problem, but also improved the sample efficiency. Simulation results showed that the proposed hybrid reinforcement learning mechanism enabled the NAO robot to balance on an oscillating platform with different frequencies and magnitudes. Both control performance and robustness were guaranteed during the experiments.

This article presents data from a research paper entitled “Postural balance, muscle strength, and history of falls in end-stage renal disease patients living with a kidney transplant: a cross-sectional study” available in Journal Gait and Posture [1] . In this article, we reported the minimal detectable changes at the 95% level of confidence (MDC95) of postural balance variables measured in eyes open (EO) and eyes closed (EC) conditions, with a stabilometric platform, in 59 kidney transplant (KT) recipients (mean age= 53.2 ± 11 years). In addition, we also performed receiver operating characteristics (ROC) curve analysis to explore the ability of postural balance measures to discriminate fallers and non-fallers (history of falls: yes or no). Sensitivity, specificity and area under the curve (AUC) of mean center of pressure velocity (CoPv), sway area (SA), center of pressure range of displacement in the anterior-posterior (AP) and medio-lateral (ML) directions were calculated. These data can be used by researchers aiming to design psychometric studies of postural balance in KT patients and they also provide clinicians with information on possible prioritization of outcome assessment for future fall-risk research in this clinical population.

Background People use various strategies to maintain balance, such as taking a reactive step or rotating the upper body. To gain insight in human balance control, it is useful to know what makes people switch from one strategy to another. In previous studies the transition from a non-stepping balance response to reactive stepping was often described by an (extended) inverted pendulum model using a limited number of features. The goal of this study is to predict whether people will take a reactive step to recover from a push and to investigate what features are most relevant for that prediction by using a data-driven approach. Methods Ten subjects participated in an experiment in which they received forward pushes to which they had to respond naturally with or without stepping. The collected kinematic and center of pressure data were used to train several classification algorithms to predict reactive stepping. The classification algorithms that performed best were used to determine the most important features through recursive feature elimination. Results The neural networks performed better than the other classification algorithms. The prediction accuracy depended on the length of the observation time window: the longer the allowed time between the push and the prediction, the higher the accuracy. Using a neural network with one hidden layer and eight neurons, and a feature set consisting of various kinematic and center of pressure related features, an accuracy of 0.91 was obtained for predictions made up until the moment of step leg unloading, in combination with a sensitivity of 0.79 and a specificity 0.97. The most important features were the acceleration and velocity of the center of mass, and the position of the cervical joint center. Conclusion Using our classification-based method the occurrence of reactive stepping could be predicted with a high accuracy, higher than previous methods for predicting natural reactive stepping. The feature set used for that prediction was different from the ones reported in other step prediction studies. Given the high step prediction performance, our method has the potential to be used for triggering reactive stepping in balance controllers of bipedal robots (e.g. exoskeletons).

A cross-sectional, prospective, between-subjects design was used in this study to establish the differences in sensory reweighting of postural control among different ages during adolescence. A total of 153 adolescents (five age groups; 13–17 years old) performed bipedal standing in three sensory conditions (i.e., with visual restriction, vestibular disturbance, and proprioceptive disturbance). Center of pressure displacement signals were measured in mediolateral and anteroposterior directions to characterize reweighting in the sensory system in static postural control when sensory information is disturbed or restricted during adolescent growth. The results indicate a development of postural control, showing large differences between subjects of 13–14 years old and older adolescents. A critical change was found in sensory reweighting during bipedal stance with disturbance of proprioceptive information at 15 years old. Adolescents of 13–14 years old showed less postural control and performance than older adolescents during the disturbance of proprioceptive information. Moreover, the results demonstrated that the visual system achieves its development around 15–16 years old. In conclusion, this research suggests that a difference of sensory reweighting under this type of sensorial condition and sensory reweight systems would seem to achieve stabilization at the age of 15.

The aim of the study was to assess the impact of proprioceptive training with the use of virtual reality (VR) on the level of postural stability of high&ndash, altitude workers. Twenty-one men working at height were randomly assigned to the experimental group (EG) with training (n = 10) and control group (CG) without training (n = 11). Path length of the displacement of the center of pressure (COP) signal and its components in the anteroposterior and medial&ndash, lateral directions were measured with use of an AccuGaitTM force plate before and after intervention (6 weeks, 2 sessions &times, 30 min a week). Tests were performed at two different platform heights, with or without eyes open and with or without a dual task. Two&ndash, way ANOVA revealed statistically significant interaction effects for low&ndash, high threat, eyes open-eyes closed, and single task-dual task. Post-training values of average COP length were significantly lower in the EG than before training for all analyzed parameters. Based on these results, it can be concluded that the use of proprioceptive training with use of VR can support, or even replace, traditional methods of balance training.

The effects of different factors&mdash, such as age, sex, performance level, and athletic shoe features&mdash, on postural balance in athletes remain unclear. The main objective of our study is to identify the features of postural stability in athletes of different age, sex, performance level, and using different types of athletic shoes. This study assessed postural stability in athletes (n = 936, 6&ndash, 47 years) in a normal bipedal stance with eyes open (EO) and eyes closed (EC). Postural stability was evaluated based on the center of pressure (COP), sway area (AS), and velocity (VCP) while standing on a stabiloplatform. Children (6&ndash, 12 years) and teen athletes (13&ndash, 17 years) showed reduced AS-EO (p &lt, 0.01) and VCP-EO (p &lt, 0.01) compared to control (n = 225, 7&ndash, 30 years). In male and female athletes aged 18+, only VCP-EC was lower versus control. In females (13&ndash, 17 and 18+), VCP-EO and EC were lower than in males (p &lt, 0.05). Only in the Shooting group, the athletes&rsquo, performance levels had an effect on VCP-EO (p = 0.020). Long use of rigid athletic shoes with stiff ankle support was associated with reduced posture stability. Postural stability in athletes was mostly influenced by the athlete&lsquo, s age, and, to a lesser extent, by their sex, performance level, and athlete shoe features.

Background According to the American Physical Therapy Association, there is strong evidence to show that vertebral mobilization and manipulation procedures can be used to improve spinal and hip mobility and reduce pain and incapacity in low back pain patients that fit the clinical prediction rule. Objectives: To evaluate the immediate effects of high-velocity low-amplitude (HVLA) manipulation on pain and postural control parameters in individuals with nonspecific low back pain. Methods This study used a participant-blinded and assessor-blinded randomized controlled clinical trial involving a single session, in which 24 participants were randomly distributed into control (simulated manipulation) and intervention (HVLA lumbar manipulation) groups. The primary (pain: subjective pain intensity and pressure pain threshold) and secondary outcomes (postural control: ellipse area, center of pressure [COP] excursion, COP RMS velocity, and differences between the COP and center of projected gravity) were evaluated before and after the session using a numerical pain scale, algometer, and a force platform. For all outcomes, multiple mixed 2 (group) × 2 (time) ANOVAs were performed. Results For the subjective pain intensity, only time was significant as a main effect, where pre-intervention presented a greater value then post-intervention (F [1.44] = 4.377; p = 0.042; r = 0.30). For the pressure pain threshold no significant effect was found. For the postural control parameters, as a main effect, only the ellipse area was significantly greater in the control group (F [1.44] = 6.760; p = 0.013; effect size = 0.36). Conclusions There was a reduction in subjective pain intensity, evaluated using a numerical scale, in both the intervention and control groups immediately after the intervention, suggesting that the spinal manipulation had a similar effect to the placebo procedure. No effect of HVLA lumbar manipulation was identified for postural control variables in either the intervention or control groups. Trial registration The study was registered at ClinicalTrials.gov under the number NCT02312778, registered at 14 September 2014.

The database is a collection of postural data acquired from 10 patients affected by the rare Stargardt's syndrome, all having the ABCA4 gene mutation, and from 10 control healthy subjects. Specifically, the database includes a file (.xlxs) called SubjectsData and 20 datasets (MATLAB structures) containing postural signals. Each subject performed a total of 15 postural tests, 5 postural tests for 3 different conditions (‘C’: eyes-closed; ‘O’: eyes-open, still target fixation; ‘M’: eyes-open, moving target tracking). For each postural test, 11 postural derived signals (the anterior-posterior force, the medio-lateral force, the vertical force, the plate moment about x axis, the plate moment about y axis, the plate moment about z axis, the plate moment about top plate surface about x axis, the plate moment about top plat surface about y axis, the x-coordinate of the center of pressure, the y-coordinate of the center of pressure, and the free moment about z axis) were computed from 8 raw signals, acquired at the Ophthalmic Hospital of Turin, Italy, through an 8-channel Kistler 9286A force platform connected to a Step32 system. Thus, a total of 285 postural signals (120 raw and 165 derived) are available for each subject. The database may be useful to: (1) investigate postural adaptations of patients affected by Stargardt's syndrome; (2) support definition of rehabilitative procedures to reduce postural instability of patients affected by Stargardt's syndrome; and (3) support investigation on visual control of balance in the general population.

Maintaining an upright posture while talking or texting on the phone is a frequent dual-task demand. Using a within-subjects design, the aim of the present study was to assess the impact of a smartphone conversation or message texting on standing plantar pressure and postural balance performance in healthy young adults. Thirty-five subjects (mean age 21.37 &plusmn, 1.11 years) were included in this study. Simultaneous foot plantar pressure and stabilometric analysis were performed using the PoData system, under three conditions: no phone (control), talking on a smartphone (talk) and texting and sending a text message via a smartphone (text). Stabilometric parameters (center of pressure (CoP) path length, 90% confidence area and maximum CoP speed) were significantly affected by the use of different smartphone functions (p &lt, 0.0001). The CoP path length and maximum CoP speed were significantly higher under the talk and text conditions when compared to the control. CoP path length, 90% confidence area and maximum CoP speed were significantly increased in talk compared to text and control. Talking on the phone also influenced the weight distribution on the left foot first metatarsal head and heel as compared with message texting. Postural stability in healthy young adults was significantly affected by talking and texting on a smartphone. Talking on the phone proved to be more challenging.

Purpose: The establishment of early diagnostic methods for Parkinson disease (PD) is one of the key features to clinically control the rate of PD progression. This study aimed to give a first step toward recognizing the efficacy of multiple postural indices of balance control in differentiating medicated PD patients from health participants. Methods: Nine individuals with PD (Hoehn and Yahr Stage up to 2), 9 staged 2.5 and up, and 9 healthy age-matched Controls performed bipedal stances for 120 seconds with eyes either open or closed on a stable force platform. All participants with PD were under anti-Parkinsonian medication. Non-parametric tests investigated the effects of PD and visual input on postural indices extracted from the center of pressure coordinates. Results: Independent of the stage of the disease, individuals with PD presented faster and shakier body sway compared with Controls. Advanced stages of PD also revealed increased body sway length and variability. In addition, medio-lateral postural instability was more pronounced in all stages of PD when visual inputs were not allowed. Conclusion and Significance: Body sway velocity, jerkiness, length, and its variability revealed to be potential markers for subclinical signs of adjustments in the neuromechanisms of balance control and postural instability even at early stages of disease and under anti-Parkinsonian medication. Results produced here will direct future studies aiming to investigate the efficacy of these same indices on recognizing subclinical development of PD as well as those individuals susceptible to faster rates of progression.

This study was designed to assess how the results obtained for three different posturographic platforms agreed with each other in an assessment of static postural stability. The study included 111 young healthy participants. A measurement of postural stability was made for each participant, with their eyes open and then closed, on each platform in a random order. The Romberg ratio, path length, and center of pressure (COP) area were analyzed. For all measures, significant differences (p &lt, 0.05) were observed among the three force plates. The highest Spearman's rank correlation was observed between Alfa vs. CQStab2P (0.20 to 0.38), and the lowest between Alfa vs. AccuGait (&minus, 0.19 to 0.09). Similar results were obtained for the concordance correlation coefficient (0.10 to 0.22 for Alfa vs. CQStab2P and &minus, 0.6 to 0.02 for Alfa vs. AccuGait). Bland&ndash, Altman analysis for values standardized (z-scores) against AccuGait indicated a low level of agreement between compared platforms, with the largest error between AccuGait vs. Alfa, and a slightly lower error between AccuGait vs. CQStab2P or Alfa vs. CQStab2P. The 95% limits of agreement ranged from 2.38 to 7.16 (Alfa vs. AccuGait), 2.09 to 5.69 (CQStab2P vs. AccuGait), and 1.39 to 7.44 (AccuGait vs. Alfa) in COP length with eyes open and COP length Romberg ratio, respectively. Special care is recommended when comparing values relating to COPs from different devices that are analyzed by different software. Moreover, unperturbed stance tests among young healthy adults can be questioned as a valid postural control parameter.