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BACKGROUND: Knee osteoarthritis (OA) impairs postural control and may affect how the lower limb joints are used for postural control. OBJECTIVE: To investigate how individuals with knee OA use lower limb joints for static postural control. METHODS: Ten patients with knee OA and thirteen healthy controls performed quiet standing for 30 s. The standard deviation of the center of mass (COM) and lower limb joint motions in the anterior-posterior (AP) and medial-lateral (ML) planes were calculated from three-dimensional marker trajectories. Pearson’s correlation analysis and independent t-tests were conducted to investigate the relationship between COM and lower limb joint motion and to compare group difference, respectively. RESULTS: The AP hip angular velocity alone in the knee OA group and the AP hip and knee angular velocity in the control group were significantly correlated with the AP COM velocity. The ML hip angular velocity was significantly correlated with the ML COM velocity in both groups. The knee OA group exhibited a significantly larger standard deviation of AP COM velocity than the control group. CONCLUSIONS: Individuals with knee OA depended solely on the contribution of the hip to the AP COM velocity, which could not be successfully controlled by the knee.

Patients with hallux rigidus (HR) tend to develop a characteristic alteration in walking to lessening pain and compensate for the limited range of motion at the first metatarsophalangeal (MTP1) joint that might be affected balance and gait. The goal of this study was to perform an integrated biomechanical description of gait and balance of symptomatic patients with either grade as III or IV HR in comparison with healthy subjects. Eleven patients (7 men) with HR (60 ± 7 years, 1.60 ± 0.07 m, and 70 ± 13 kg) and 16 (7 men) healthy subjects (70 ± 8 years, 1.66 ± 0.10 m, and 74 ± 14 kg) were included. Subjects performed 2 tasks: walking (5 trials of straight walking for at least 6 meters) and bipedal quiet standing for 30 seconds. For these 2 tasks the following variables were measured: range of motion of the MTP1 joint, plantar pressure distribution during the stance phase of walking, and the postural sway during quiet standing. Plantar pressure was measured in up 15 walking trials with a mat pressure sensor. The MTP1 joint range of motion for flexion/extension during walking was significantly smaller for the patients with HR than for the control group (HR: 14 ± 8°, control: 44 ± 5°; t(17) = -9.7, p.001). The forefoot plantar pressure distribution among different regions of the foot in patients with HR was not statistically different than the control group, but there was a tendency of higher pressures in the lateral metatarsal heads (p = .06). As description of the postural sway during quiet standing, the center of pressure area was not different between HR and the control group (p.05). Decreased MTP1 joint range of motion for flexion/extension during walking in symptomatic high-grade HR patients can be associated with higher pressure in the lateral metatarsal heads while the impact on postural sway is not affected.

Background Postural sway during quiet standing has been shown as a useful task to assess risk of falling in older adults. While the risk of falling is consistently reported to be higher in older females than males, the sex-related differences in postural sway are not consistent across the studies. Research question What are the effects of age and sex on postural sway during quiet standing during different stance conditions? Methods We examined the effects of age (40 young and 34 older adults), sex (37 males and 37 females), and their interaction on the postural sway during different stance conditions. We compared the center of pressure (CoP) velocity, amplitude and frequency during parallel (eyes open and eyes closed) and semi-tandem (eyes open) stances. Results Our results suggest that postural sway is similar between sexes in young participants, while older males exhibit larger postural sway than older female participants (10/21 outcomes). Older female participants exhibited lower CoP amplitude (but larger total and anterior-posterior CoP velocity) compared to young female participants. We also found that the increase in the postural sway with increasing task difficulty is more pronounced in older vs. young adults. Significance This study shows that ageing-related changes in postural sway are sex- and task-specific. Researchers and clinicians need to be aware of these effects when comparing groups or monitoring changes in time.

The loaded walking ability of people can be enhanced by lower limb exoskeleton. How to avoid lower limb joint injuries while improving walking efficiency is a major challenge for loaded walking assistance. Inspired by the muscle-skeleton working mechanism of human, we proposed a lower limb exoskeleton with rigid and soft structure for active hip extension assistance and passive load transfer assistance. Its motion flexibility, load transfer ability and metabolic cost were investigated. Five motions including jumping jack, sit down, crouch, across obstacle, and forward lunge were realized by the wearer. Under the conditions of quiet standing and dynamic walking, the percentages indicating the degree of load transfer to the ground reached up to 88% and 67%, respectively. Compared to the condition of no exoskeleton, the net metabolic reductions of 20kg-loaded walking in three experimental setups, namely, active-passive assistance on, active exosuit assistance only, and active assistance off-passive assistance on, achieved 12.8%, 8.5% and 3.7%, individually. The results demonstrate that our rigid-soft lower limb exoskeleton presents outperformance in loaded walking assistance.

The purpose of the present study was to determine whether there are sex differences in fatigue-induced changes in quiet standing and dynamic balance and establish whether changes in muscle torque and resting stiffness may explain the potential sex differences in balance responses. Sixteen recreationally active men (age; 24.8 ± 5.0 years, height; 178.2 ± 5.6 cm, mass; 77.8 ± 13.2 kg) and 10 women (age; 21.0 ± 1.6 years, height; 167 ± 5.3 cm, mass; 61.3 ± 8.9 kg) were assessed for postural sway, Y balance test performance, isokinetic and isometric knee extensor torque and resting stiffness of the vastus lateralis (VL), gastrocnemius lateralis (GL) and Achilles tendon (AT) before and immediately after fatiguing exercise. The fatigue protocol consisted of five sets of 20-drop jumps. The fatiguing exercise elicited similar magnitude (effects size; ES) reductions in muscle torque (men; ES = 0.45–0.80, women; ES = 0.46–0.52), dynamic balance (men; ES = 0.45–0.74, women; ES = 0.47–0.79) and resting VL stiffness (men; ES = 0.46, women; ES = 0.36) in men and women (all p 0.05). Fatiguing exercise, when producing a similar level of force reduction, induces similar magnitude reductions in dynamic postural control and resting VL stiffness in men and women. Distinct deteriorations in quiet standing balance in men but not women were accompanied by modifications in calf muscle stiffness following exercise-induced muscle fatigue.

Accurate estimation of the center of mass is necessary for evaluating balance control during quiet standing. However, no practical center of mass estimation method exists because of problems with estimation accuracy and theoretical validity in previous studies that used force platforms or inertial sensors. This study aimed to develop a method for estimating the center of mass displacement and velocity based on equations of motion describing the standing human body. This method uses a force platform under the feet and an inertial sensor on the head and is applicable when the support surface moves horizontally. We compared the center of mass estimation accuracy of the proposed method with those of other methods in previous studies using estimates from the optical motion capture system as the true value. The results indicate that the present method has high accuracy in quiet standing, ankle motion, hip motion, and support surface swaying in anteroposterior and mediolateral directions. The present method could help researchers and clinicians to develop more accurate and effective balance evaluation methods.

Background: Theoretically, balance is affected by the height of center of mass (COM) during quiet standing. However, no one examined this in humans with variables derived from the center of pressure (COP). Objects: We have conducted balance experiment to measure COP data during quiet standing, in order to examine how the COP measures were affected by the height of COM, vision, floor conditions, and gender. Methods: Twenty individuals stood still with feet together and arms at sides for 30 seconds on a force plate. Trials were acquired with three COM heights: 1% increased or decreased, and not changed, with two vision conditions: eyes closed (EC) and eyes open (EO), and with two floor conditions: unstable (foam pad) and stable (force plate) floor. Outcome variables included the mean distance, root mean square distance, total excursion, mean velocity, and 95% confidence circle area. Results: All outcome variables were associated with the COM height (p 0.096), and between the COM height and floor condition (p > 0.183) for all outcome variables. Furthermore, there was no gender difference in all outcome variables (p > 0.186). Conclusion: Balance was affected by the change of COM height induced by a weight belt in human. However, the effect was not affected by vision or floor condition. Our results should inform the design of balance exercise program to improve the outcome of the balance training.

In previous studies, the influence of plantar sensation has been examined using various textured surfaces with different stiffness materials to assess static balance. This study investigated the effects of a Firm Textured Surface (FTS) along with age and sex-related influences on postural control under different visual conditions. Forty subjects (20 elderly, 10 males, mean age 68.30, 10 females, mean age 68.00, and 20 young people, 10 males, mean age 25.45, 10 females, mean age 27.30) participated in this study maintained a quiet standing on FTS, foam and firm surfaces with eyes open and closed. The center of pressure displacement (CoPDISP), CoP velocity (CoPVEL), and sway velocity of the CoP in anteroposterior (AP) and mediolateral (ML) direction (VA/P and VM/L) were measured. FTS was associated with lower postural sway measures in both the groups with eyes open and closed. However, the foam surface showed the worst results in all postural parameters under all experimental conditions. Separate four-way ANOVAs were applied to each dependent variable. The main effects of surface (p p p DISP, CoPVEL and VA/P; p = 0.0003 for VM/L) were significant in each of the four fitted models. Sex was never significant, either as a main effect or an interaction with other experimental factors. Eyes open were able to reduce the negative effects of the foam surfaces but without vision the proprioceptive sensory system cues of the body state become more important for maintaining balance. A good stimulation with rigid texture should be considered as relief to reduce the physiological-related decline of afferent information with age.

Individuals with motor incomplete spinal cord injuries (iSCI) often have impaired abilities to maintain upright balance. For able-bodied (AB) individuals, the ankle and hip joint accelerations are in antiphase to minimize the postural sway during quiet standing. Here we investigated how interjoint coordination between the ankle and hip joints was affected in individuals with iSCI, leading to their larger postural sway during quiet standing. Data from 16 individuals with iSCI, 14 age- and sex-matched AB individuals, and 13 young AB individuals were analyzed. The participants performed quiet standing during which kinematic and kinetic data were recorded. Postural sway was quantified using center-of-pressure velocity and center-of-mass acceleration. Individual ankle and hip joint kinematics were quantified, and the interjoint coordination was assessed using the cancellation index (CI), goal-equivalent variance (GEV), nongoal-equivalent variance (NGEV), and uncontrolled manifold (UCM) ratio. Individuals with iSCI displayed greater postural sway compared with AB individuals. The contribution of ankle angular acceleration toward one's sway was significantly greater for those with iSCI compared with AB groups. CI and the UCM ratios were not statistically different between the groups, while GEV and NGEV were significantly greater for the iSCI group compared with the AB groups. We demonstrated that individuals with iSCI show larger postural sway compared with the AB individuals during quiet standing, primarily due to larger ankle joint acceleration. We also demonstrated that the interjoint coordination between ankle and hip joint is not affected in individuals with iSCI, which is not successfully able to reduce the large COM acceleration.

Impairments in postural stability are present in children with autism spectrum disorder (ASD), but documentation of impairments as individuals age into adulthood are sparse and have yielded inconsistent results. Therefore, the purpose of this study was to assess postural control of college students with and without ASD during four conditions: eyes open and eyes closed, for both single- and double-leg stances. Twenty participants (10 with ASD and 10 without ASD) between the ages of 18 and 30 performed three quiet standing trials in each of the four conditions. Antero-posterior (A-P) and medio-lateral (M-L) sway and sway velocity, as well as sway area and stance time, were calculated for each condition and compared between groups. In the double-leg eyes open and eyes closed conditions, A-P displacement and sway area were greater in individuals with ASD. There were no differences in sway between groups in the single-leg eyes open condition. Individuals with ASD demonstrated much shorter stance times than individuals without ASD in the single-leg eyes closed condition. Young adults with ASD display less postural stability in both simple and complex balance tasks than young adults without ASD. It appears that the balance abnormalities reported in children with ASD persist into adulthood.

Strokes are the third leading cause of disability worldwide. Currently, several types of performance assessment, such as the Fugl–Meyer index, are used to explore the overall difference between cer...

Elderly and disabled people frequently experience falls that may require early assessment and training. The quiet standing test provides descriptive statistics such as the center of pressure (COP) sway data, which can be used to analyze the decline in balance ability. Generally, higher descriptive statistics indicate lower balance ability. Stochastic models can model COP trajectories, and such equation parameters were previously used to assess the balance of patients. However, the model equation is a hypothesis and should be verified. In this study, we evaluated whether stochastic models can predict the descriptive statistics of observed COP trajectories. We estimated the model parameters by fitting postural sway data from 49 individuals in four linear stochastic models, and the prediction accuracy was verified by comparing the observed descriptive statistics with the predicted COP trajectories. We observed that the prediction accuracy of the models with stiffness was much higher than those with viscosity only, and the models with the center of mass (COM) had higher prediction accuracy than COP-only models. Therefore, we identified that coefficients from Langevin-based models contained descriptive statistics about a subject’s COP trajectory, which suggested that these coefficients can be used to effectively assess balance issues.

Freezing of gait (FoG) is one of the main reasons for movement initiation disorders and abnormal coupling of posture and gait in Parkinson's disease (PD). Patients with FoG have poor postural control when compared to patients without FoG. However, the nature of the interrelationship between FoG and domains of postural control remains unknown. The aim of this study was to estimate the association between different domains of postural control and severity of FoG in patients with moderate-to-severe PD. Thirty patients with idiopathic PD with FoG (age range 45-80 years, Hoehn & Yahr stages 3 and 4) participated in the study. We evaluated objective (FoG-ratio during turning task) and subjective (New Freezing of Gait Questionnaire, NFoG-Q) measures of FoG severity, reactive postural adjustments in response to an external perturbation, first step anticipatory adjustment for step initiation and quiet standing stability. In the multiple regression analysis, step initiation was the strongest significant correlation of the NFoG-Q score explaining 23% of the variance of the assessment. For the objective FoG measure, mediolateral CoP amplitude in quiet standing and mediolateral CoP amplitude in step initiation explained 39% of the variance of the FoG-ratio. As main conclusions, this study identified the association between objective and subjective measure for FoG severity and postural control domains. The results support conducting step initiation training during rehabilitation of individuals with FoG.

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.

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.

BACKGROUND People with migraine exhibit postural control impairments. These patients also have an increased light sensitivity due to the disease, and it remains during the headache-free period. It is currently unknown if increased lighting levels can alter the balance control, especially in individuals with visual hypersensitivity, such as migraineurs. This study aimed to assess the balance and photophobia of women with migraine and non-headache controls under different light conditions. METHODS This cross-sectional study consisted of 14 women with migraine (mean ± SD 30.6 ± 8.1 years old) and 14 women without any kind of headache (mean ± SD 27.2 ± 2.8 years old) screened from a tertiary headache clinical hospital and the local community. Quiet standing balance was evaluated during bipodal and unipodal support, under 3 light conditions: ambient (AMB) - 270 lx, visual discomfort threshold (VDT) - 400 lx, and intense visual discomfort (IVD) - 2000 lx. Sway area of the center of pressure was processed and compared between groups. The association of migraine with the risk of presenting a greater imbalance in the discomfort lighting conditions was verified. RESULTS Compared to the non-headache controls, the migraine group presented greater sway area in bipodal stance under the 3 light conditions (mean difference (95% CI)): AMB 0.81 cm2 (0.19 to 1.43), P = .011; VDT 3.17 cm2 (0.74 to 5.60), P = .001; IVD 5.56 cm2 (2.75 to 8.37), P

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.

CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Background: Older adults require special attention during cognitive-motor tasks since automatic postural control is reduced. AIM: To analyze the effect of physical exercise on dual-task processing of healthy older women performing standing balance. Method: Sixteen healthy older women were assessed in a quiet standing position with eyes open/closed (single-task, EO, and EC) and with a cognitive task (dual-task, DT) using a Wii Balance Board. All individuals performed training (aerobic, strength, and virtual reality exercises) at moderate effort. Center of pressure (CoP) anteroposterior and mediolateral displacement were analyzed over time pre- and post-training. The Wilcoxon test was used to compare pre- and post-training. Results: Greater variability in CoP was observed pre- compared to post-training. In the DT, there was a significance decrease in post-training variability compared to pre-training (p

Summary Background. Depending on the level of lesion, spinal cord injury (SCI) individuals have limited ability to stand and walk. They have to use various assistive devices to restore their abilities. The aim of this study was to evaluate the stability of SCI individuals during walking and quiet standing. Material and methods. Three groups: normal subjects and SCI individuals with complete and incomplete lesions, were enrolled. Stability of the subjects was evaluated based on center of pressure (COP) sways in quiet standing and spatiotemporal gait parameters in walking. The difference between the stability of normal and SCI subjects was determined by use of the two-sample t test. The correlation between the mean values of stability parameters in standing and walking and lesion level was determined by use of Pearson’s correlation. Results. The stability of SCI subjects during quiet standing was better than that of normal subjects. How­ever, their dynamic stability was significantly less than normal subjects. The dynamic stability of complete and incomplete SCI subjects did not differ significantly (P-value

Holding an object has been found to reduce postural sway during quiet standing. However, people normally stand to accomplish suprapostural goals, such as fitting a key into a lock. Postural control should therefore be assessed by examining postural outcomes in the context of suprapostural task performance. This study assessed whether holding an object increased standing postural stability and improved the performance of a concurrent precision manual task. A total of 15 young adults performed a precision manual task with their dominant hand while holding or not holding an object in their nondominant hand. Postural stability was assessed using measures of postural sway and time to boundary. Suprapostural task performance was assessed as an error count. Holding did not influence postural sway or suprapostural task performance. Discrepancies among previous studies coupled with the present findings suggest that the effects of holding an object on standing posture are highly sensitive to the experimental context. The authors provide several explanations for their findings and discuss the limitations of previous suggestions that holding an object may have clinical relevance for balance-compromised populations.

To date, the human balance assessment is mainly achieved by measuring the center of pressure (COP) trajectory of upright posture. However, COP-based metrics provide inconclusive results under certain circumstances, due to the lack of relevance with the body balance mechanism. This paper developed a novel framework to measure the variability in body sway based on the Poincare analysis to enhance the balance assessment. It provided nonlinear parameters SD1, SD2, and their ratio SD1/SD2 as quantitative indicators of the local and global balance regulation capacities. 136 healthy adults were categorized into young and elderly groups and received test on a force platform. COP signals were recorded for 30 s under eyes-opened and eyes-closed vision conditions. The results were analyzed using the two-way mixed-design analysis of variance and show that the technology is able to reveal the effect of age and vision on the balance control by SD1, SD2, and SD1/SD2. SD1 mainly responded to vision, and SD2 was more influenced by age. Due to the information about the subtle adjustment during quiet standing, these Poincare indexes surpassed the conventional COP measurements in demonstrating the balance control behavior. It can be concluded that the supposed method of estimating the local and global variabilities is a valuable approach for the balance assessment.

Background: People with Parkinson's disease (PD) often have backward displacement of their center of pressure (COP) during quiet standing and reduced stability limits, as compared to healthy controls. These kinetic characteristics may induce postural instability in people with PD.Objective: To investigate the short-term effects on COP displacements during quiet standing and forward leaning brought about by the post-incline leaning after-effects in people with PD.Methods: Twenty participants with PD were randomly divided into two groups (tilting and control groups). The tilting group was required to stand upright quietly on a tilting board angled to raise the front part of the feet. The control group was asked to voluntarily lean their bodies forward as far as possible. The total time of the intervention was 60 seconds for each group. The COP displacements during quiet standing and forward leaning were recorded before and after the intervention.Results: In the tilting group, the COP significantly shifted forward after the intervention compared to that before the intervention during quiet standing as well as forward stability limits; this did not happen in the control group.Conclusions: The post-incline leaning after-effects may induce the short-term effects of forward shifting of COP during quiet standing and expand the forward stability limits in people with PD.

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

Previous findings indicate that co-contractions of plantarflexors and dorsiflexors during quiet standing increase the ankle mechanical joint stiffness, resulting in increased postural sway. Balance impairments in individuals with incomplete spinal cord injury (iSCI) may be due to co-contractions like in other individuals with reduced balance ability. Here we investigated the effect of co-contraction between plantar- and dorsiflexors on postural balance in individuals with iSCI (iSCI-group) and able-bodied individuals (AB-group). Thirteen able-bodied individuals and 13 individuals with iSCI were asked to perform quiet standing with their eyes open (EO) and eyes closed (EC). Kinetics and electromyograms from the tibialis anterior (TA), soleus and medial gastrocnemius were collected bilaterally. The iSCI-group exhibited more co-contractions than the AB-group (EO: 0.208% vs. 75.163%, p = 0.004; EC: 1.767% vs. 92.373%, p = 0.016). Furthermore, postural sway was larger during co-contractions than during no co-contraction in the iSCI-group (EO: 1.405 cm/s2 vs. 0.867 cm/s2, p = 0.023; EC: 1.831 cm/s2 vs. 1.179 cm/s2, p = 0.030), but no differences were found for the AB-group (EO: 0.393 cm/s2 vs. 0.499 cm/s2, p = 1.00; EC: 0.686 cm/s2 vs. 0.654 cm/s2, p = 1.00). To investigate the mechanism, we performed a computational simulation study using an inverted pendulum model and linear controllers. An increase of mechanical stiffness in the simulated iSCI-group resulted in increased postural sway (EO: 2.520 cm/s2 vs. 1.174 cm/s2, p 2 vs. 1.836 cm/s2, p 2 vs. 0.658 cm/s2, p = 1.00; EC: 0.943 cm/s2 vs. 0.926 cm/s2, p = 0.190). Thus, we demonstrated that co-contractions may be a compensatory strategy for individuals with iSCI to accommodate for decreased motor function, but co-contractions may result in increased ankle mechanical joint stiffness and consequently postural sway.

Coordinated movements of both lower limbs may be a clinically important indicator of motor control during quiet standing. From a neurological point of view, it is known that extensive coupling of muscles must be coordinated an upright posture. However, movement coordination between the lower limbs is the final motor output, is unknown. In this study, we focussed on the ground reaction force (GRF) vector and clarified the time and frequency characteristics of the force vectors of both lower limbs.A total of 16 healthy young adults and 18 healthy older adults participated and placed each bare foot on one of two force plates to measure the GRF vectors (i.e., anteroposterior, mediolateral, and vertical) of each lower limb and determine the centre of mass (COM) acceleration in the anteroposterior direction (COMacc). Characteristics of the coordination of both lower limbs during movements were analysed using coherence analysis and cross-correlation function analysis (CCF).The coherence levels of the force vectors of both lower limbs were higher in all three directions and significantly increased in the older adults. CCF analysis showed that the force vectors of both lower limbs were negatively correlated at the zero-time lag. Moreover, a weak correlation was observed between COMacc and coherence values.The assessment of bilateral lower limb connectivity using force vectors can be used as an evaluation method to reflect changes in the ability to control bipedal standing during ageing.

The existence of a learning effect by which subjects progressively reduce body sway over the course of repetitive stabilometric measurements is currently debated. Also, the position and orientation of the feet on the platform can have a substantial influence on the outcome measurements. The aim of the present work was to assess the effect of feet positions on mean total velocity (V) of the center of pressure and the area (AR) covered by its displacements during quiet standing. A group of 35 healthy young subjects was examined during two successive sessions consisting of five recordings with their feet placed either in the recommended (standard, SP) or their usual most comfortable (UP) position. Results show a slight decreasing trend that failed to be statistically significant checked with Friedman's ANOVA (SP AR, χ2(4)=6.10, p=0.19 and V, χ2(4)=8.66, p=0.07 and UP AR, χ2(4)=2.32, p=0.68 and V, χ2(4)=1.19, p=0.88). Nonetheless, values of AR and V showed a notable decrement especially evident in the SP exam reaching, respectively, 24% and 11% from baseline, whereas variability measured by the coefficient of variation was the same in the two exams. Given the results, a learning effect should not be ruled out with confidence. Also, usual foot placement would be preferable to avoid this effect. Further research is needed to take into consideration the great variability of stabilometric measurements and the fact that different subjects could adapt more readily to the test conditions than others.

Background: Postural control impairments following a stroke have impact on mobility, reduce independence and increase the risk of falls. Assessing these impairments during tasks representative of real-life situations, such as quiet standing (QS) and voluntary stepping response (VSR) will enhance our understanding of how the postural control system is impaired in individuals post-stroke (IPS). It will also inform the development of a more targeted and effective rehabilitation to prevent falls in IPS.\ud Objectives: Identify the postural control impairments encountered by IPS during QS and VSR. \ud Methods: Twenty IPS and sixteen healthy controls were recruited to perform QS and VSR tasks while ground reaction forces and whole-body motion were measured. Displacement and speed variation of the COM, centre of pressure (COP) displacement and spatiotemporal data were calculated and compared between groups. \ud Results: During QS, IPS exhibited greater maximal COP displacement in mediolateral direction, COM displacement in vertical direction and COM speed excursions compared to controls. During VSR, IPS exhibited smaller step length, braking force, posterior foot placement in relation to the pelvis and COM anteroposterior excursion compared to controls. IPS presented less static and dynamic postural stability compared to controls. \ud Conclusions: Greater postural sway during QS, smaller anteroposterior COM displacement before losing balance and altered voluntary recovering steps during VSR could place IPS at more risk of falling when they face a postural challenge in the community. These novel results will improve the current knowledge base and should be considered in IPS rehabilitation.

International audience; The study of human balance recovery strategies is important for human balance rehabilitation and humanoid robot balance control. To date, many efforts have been made to improve balance during quiet standing and walking motions. Arm usage (arm strategy) has been proposed to control the balance during walking motion in the literature. However, limited research exists on the contributions of the arm strategy for balance recovery during quiet standing along with ankle and hip strategy. Therefore, in this study, we built a simplified model with arms and proposed a controller based on nonlinear model predictive control to achieve human-like balance control. Three arm states of the model, namely, active arms, passive arms, and fixed arms, were considered to discuss the contributions of arm usage to human balance recovery during quiet standing. Furthermore, various indexes such as root mean square deviation of joint angles and recovery energy consumption were verified to reveal the mechanism behind arm strategy employment. In this study, we demonstrate to computationally reproduce human-like balance recovery with and without arm rotation during quiet standing while applying different magnitudes of perturbing forces on the upper body. In addition, the conducted human balance experiments are presented as supplementary information in this paper to demonstrate the concept on a typical example of arm strategy.

Background: Astronauts returning to earth usually demonstrate reduced orthostatic tolerance when assessed on a tilt table or quiet standing, but no studies have evaluated postflight orthostatic tolerance during activities of daily living, when it is most clinically relevant. Ambulatory blood pressure (BP) variability also is associated with orthostatic intolerance in certain patient populations and can capture clinically significant orthostatic hypotension during activities of daily living, especially when measured on a beat-to-beat basis. We evaluated the impact of prolonged spaceflight on orthostatic tolerance and BP profiles in astronauts. Methods: Ambulatory beat-to-beat BP was recorded using a portable device for multiple 24-hour time periods before, during, and after 6 months of spaceflight in 12 astronauts (4 women; age 48±5 [mean±SD] years). BP variability in the time domain was calculated as the SD. Systolic BP distribution during activities of daily living was characterized by skewness and kurtosis. Results: In contrast with results from previous studies that used tilt tables or stand tests, no astronaut experienced orthostatic intolerance/hypotension during activities of daily living before or after spaceflight. Also, 24-hour systolic BP decreased in space (120±10 mm Hg before spaceflight versus 106±9 mm Hg during spaceflight; P P >0.05). The skewness of systolic BP increased in space (0.74±0.51 versus 1.43±1.00; P =0.001), indicating that signal fluctuations became asymmetrical; however, it returned to preflight levels after landing (0.51±0.42). The kurtosis increased in space (5.01±7.67 versus 11.10±11.79; P =0.010), suggesting that fluctuations concentrated around the mean with a narrow distribution; however, it also returned to preflight levels (2.21±2.56) after return to earth. Conclusions: Given current countermeasures including in-flight exercise training and volume resuscitation on return, no astronauts experienced orthostatic hypotension or intolerance during routine (for landing day) activities in the initial 24 hours after landing following 6 months in space. Prolonged exposure to spaceflight had little impact on systolic BP variability and its distribution, although the latter showed a transient change in space (accompanied by mild relative hypotension), all of which returned to preflight values after return to earth.

PURPOSE To evaluate postural symmetry in sitting and standing for children with hemiplegic cerebral palsy (hCP) following the Combined Approach to Treatment for Children with Hemiplegia (CATCH) protocol, an intervention combining Constraint Induced Movement Therapy, Bimanual Intensive Therapy and Neuro-Developmental Treatment. METHODS The study included 10 children with a diagnosis of hCP and 10 typically developing age-matched peers. Subjects participated in a CATCH camp for six hours daily for eight consecutive days. Postural symmetry measurements in quiet sitting and standing were obtained using a Boditrak pressure-mapping system at four time points: prior to start of camp (T1), first day of camp (T2), last day of camp (T3), and one month post-camp (T4). RESULTS Significant differences (p< 0.05) were found in quiet sitting when comparing postural symmetry pre-intervention and one-month post camp. In quiet standing, significant differences (p< 0.05) were found when pre-intervention was compared to one-month post-intervention. One month post-intervention, the intervention group showed no significant difference from the comparison group. CONCLUSIONS Children with hCP demonstrate improvement in postural symmetry in sitting and standing following participation in a CATCH camp. Following the intervention, children with hCP continued to improve postural symmetry and approach age-matched peers.

Body sway has usually been studied during symmetrical standing while lower limbs equally contributed in upright posture. The present study aimed to examine the dynamics of body sway while turning during standing with symmetrical and asymmetrical weight distribution between the legs. Subjects performed a body turn of 30° to the right and left during quiet standing and standing with the right or left foot loaded with 70% of body weight. We found that body turn in the symmetrical posture induced weight increase on the foot contralateral to the turning direction and the common center of pressure (COP) velocity increase. Body turn in the asymmetrical posture induced further loading of the foot that was initially overloaded; also turning in the direction of the unloaded foot affects weight distribution more than turning in the direction of the overloaded foot. The posture transition from symmetrical to asymmetrical induced the common COP velocity increase and forward protraction of the unloaded foot COP. Turning in the asymmetrical posture produced further increase of the common COP velocity and further forward protraction of the unloaded foot COP. Moreover, when the left leg was unloaded this resulted not only in left leg's COP forward, but also in left leg's COP lateral protraction, and left leg's COP frontal velocity increase. These findings reveal that body position and weight distribution between the feet interact to stabilize upright posture and show the effect of footedness during turning in asymmetrical standing.

The details on how the position of balance examination is achieved (preceding movement) and what is happening after (subsequent movement) is scarce. We hypothesised that the postural sway in quiet standing can differ due to demanded stability or mobility associated with the preceding and subsequent action. The body sway will be lower with high stability demand task than a condition with high mobility task. Thirteen female ballet students were examined (aged 15.1 ± 0.95 years). Participants were examined in the single-legged standing position as a part of gait initiation (G-I, high mobility) and termination (G-T, high stability) task with the use of force plate. The following Centre of Pressure (COP) variables were analysed: range and standard deviation of COP position, mean COP velocity for AP (anterio-posterior) and ML (medio-lateral) planes. The results showed that for ML plane, body sway was larger for G-I than G-T task. The lowest values of all variables in AP plane (except the COP range) were for G-T task. This difference, confirm our hypothesis, where this difference is not caused by the skills of the participants, but due to the measuring procedure and motor behaviour before and after achieving the measurement position. Our conclusion is limited to the specific posture and homogenous participants.

Background:Balance skills are challenged at the roofing worksite by dynamic visual cues in the form of clouds and trees that move with the wind; any instability may result in a fall from height.Aim:To determine if roofers are less susceptible to a dynamic visual surround (moving room) when stationary cues were available, relative to people who do not work in a similar environment.Methods:Forty male adults participated, including young roofers (N=10,26.3 years), middle-aged roofers (N=10,50.6 years), young controls (N=10,26.2 years) and middle-aged controls (N=10,55.1 years). Center of pressure root mean square (APRMS) was assessed during quiet standing and four moving room conditions when stationary cues were:(1)not in place,(2)in the foreground (inside the moving room),(3)in the background (outside the moving room, but still visible) and (4)in the foreground and background. Results:A workgroup by visual cue interaction was observed (p=0.032), where roofers had up to 18% lower APRMS relative to controls when the background references were in place. The interaction effect was independent of age. Interpretation:The roofers were able to suppress visually-induced postural sway when stationary visual cues were present in the background, likely due to the severe consequences for loss of balance when working at height. The suppression was maintained in aging workers.

Made available in DSpace on 2019-10-06T16:08:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-02-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação para o Desenvolvimento da UNESP (FUNDUNESP) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Postural control asymmetry is an important aspect of Parkinson's disease (PD) that may be associated with falls. The aim of this study was to compare the postural control asymmetry during postural tasks between fallers and non-fallers in people with PD and neurological healthy age-matched controls (CG). Individuals with idiopathic PD (n = 24) and CG (n = 24) were sub-divided into groups of fallers and non-fallers based on their fall history over the past year. Participants performed blocks of three 30-s trials of quiet standing with feet in a side-by-side and semi-tandem stance position. The center of pressure parameters for each limb were measured and used to calculate the symmetry index. Fallers compared to non-fallers had decreased asymmetry of vertical force in the side-by-side condition. During the tandem-front leg condition, PD non-fallers increased asymmetry of the medial-lateral velocity of sway compared to CG non-fallers. In addition, for the tandem–back leg condition, PD non-fallers increased asymmetry of total displacement and medial-lateral root mean square and mean velocity of sway compared to PD fallers. The results of the study did not support the hypothesis that PD fallers are more asymmetric than PD non-fallers. On the contrary, our results indicated that PD non-fallers had higher postural control asymmetry, especially during the more challenging (semi-tandem standing) postural task. São Paulo State University (UNESP) – Campus Bauru Graduate Program in Movement Science Human Movement Research Laboratory (MOVI-LAB) Department of Physical Education University of British Columbia School of Kinesiology São Paulo State University (UNESP) – Campus Rio Claro Graduate Program in Movement Science Posture and Gait Studies Laboratory (LEPLO) Department of Physical Education São Paulo State University (UNESP) – Campus Bauru Graduate Program in Movement Science Human Movement Research Laboratory (MOVI-LAB) Department of Physical Education São Paulo State University (UNESP) – Campus Rio Claro Graduate Program in Movement Science Posture and Gait Studies Laboratory (LEPLO) Department of Physical Education FUNDUNESP: 0716/011 FAPESP: 2012/24040-9 FAPESP: 2013/00925-4

Background The use of high-heeled shoes (HHS) introduces instability into the wearer’s balance system but how high-heel experience might influence standing balance is less examined in literature. Research question (1) Does foot stability decrease in both the antero-posterior (AP) and medial-lateral (ML) directions with increasing heel height during quiet standing? (2) Does high-heel experience improve the wearer’s foot stability during quiet standing in high-heeled conditions? Methods Twenty-four young females (12 regular and 12 non-regular HHS wearers) were recruited to perform quiet standing while wearing shoes with heel heights of 1 cm, 5 cm, 8 cm and 10 cm. The effects of heel height on the mean center of pressure (COP), their variability (standard deviations) and mean COP velocities in both the AP and ML directions were analysed by one-way repeated measures ANOVA and Bonferroni post-hoc test. The effects of high-heel experience were analysed through independent samples t-tests. Results The variability of the COP in both directions increased with heel height, although significance was found only in the ML direction. The COP velocities in both directions were highest for the 1 cm heel, decreased as the heel increased to 8 cm and increased again for the 10 cm heel. Experienced HHS wearers exhibited significantly smaller COP variances (AP) for the 8 cm and 10 cm heels, smaller COP velocities (AP) for all heels, and smaller COP variances (ML) and COP velocities (ML) for the 10 cm heel. Significance The use of HHS results in greater stability distortions in both AP and ML directions but high-heel experience improves balance control under high-heeled conditions. Our findings enhance the understanding of how high-heel experience might influence standing balance in different heel height, and highlights the importance of the ML components of the in-foot COP measures in the examination of standing balance in HHS.

This interview discusses the infinity of stories as an endless reservoir of imagining new forms of meaning, feeling and embodiment of fieldwork data. Thinking of ethnographic analysis and experience as a collaborative process of performance and creative expression is an alternative to the prevailing textocentric documentation that demands both a political economy of contexts and an ethics of loving attention.

Quiet standing exhibits strongly intermittent variability that has inspired at least two interpretations. First, variability can be intermittent through the alternating engagement and disengagement of complementary control processes at distinct scales. A second and perhaps deeper way to interpret this intermittency is through the possibility that postural control depends on cascade-like interactions across many timescales at once, suggesting specific non-Gaussian distributional properties at different timescales. Multiscale probability density function (PDF) analysis shows that quiet standing on a stable surface exhibits a crossover from low, increasing non-Gaussianity (consistent with exponential distributions) at shorter timescales, reflecting inertial control, towards higher non-Gaussianity. Feedback-based control at medium to longer timescales yields a linear decrease characteristic of cascade dynamics. Destabilizing quiet standing with unstable surface or closed eyes serves to attenuate inertial control and to elicit more of the feedback-based control over progressively shorter timescales. The result was to strengthen the appearance of the linear decay indicating cascade dynamics. Finally, both linear and nonlinear indices of postural sway also govern the relative strength of crossover or of linear decay, suggesting that tempering of non-Gaussianity across log-timescale is a function of both extrinsic constraints and endogenous postural control. These results provide new evidence that cascading interactions across longer-timescales supporting postural corrections can even recruit shorter-timescale processes with novel task constraints that can destabilize posture.

Postural sway is a result of a complex action-reaction feedback mechanism generated by the interplay between the environment, the sensory perception, the neural system and the musculation. Postural oscillations are complex, possibly even chaotic. Therefore fitting deterministic models on measured time signals is ambiguous. Here we analyse the response to large enough perturbations during quiet standing such that the resulting responses can clearly be distinguished from the local postural sway. Measurements show that typical responses very closely resemble those of a critically damped oscillator. The recovery dynamics is modelled by an inverted pendulum subject to delayed state feedback and is described in the space of the control parameters. We hypothesize that the control gains are tuned such that (H1) the response is at the border of oscillatory and nonoscillatory motion; (H2) the response is the fastest possible; (H3) the response is a result of a combined optimization of fast response and robustness to sensory perturbations. Parameter fitting shows that H1 and H3 are accepted while H2 is rejected. Thus, the responses of human postural balance to “large” perturbations matches a delayed feedback mechanism that is optimized for a combination of performance and robustness.

Background Studies on short-term upright quiet standing tasks have presented contradictory findings about postural control in people with Parkinson’s disease (pwPD). Prolonged trial durations might better depict body sway and discriminate pwPD and controls. Objective The aim of this study was to investigate postural control in pwPD during a prolonged standing task. Methods A total of 26 pwPD and 25 neurologically healthy individuals performed 3 quiet standing trials (60 s) before completing a constrained prolonged standing task for 15 minutes. Motion capture was used to record body sway (Vicon, 100 Hz). To investigate the body sway behavior during the 15 minutes of standing, the analysis was divided into three 5-minute-long phases: early, middle, and late. The following body sway parameters were calculated for the anterior-posterior (AP) and medial-lateral (ML) directions: velocity, root-mean-square, and detrended fluctuations analysis (DFA). The body sway area was also calculated. Two-way ANOVAs (group and phases) and 1-way ANOVA (group) were used to compare these parameters for the prolonged standing and quiet standing, respectively. Results pwPD presented smaller sway area ( P < .001), less complexity (DFA; AP: P < .009; ML: P < .01), and faster velocity (AP: P < .002; ML: P < .001) of body sway compared with the control group during the prolonged standing task. Although the groups swayed similarly (no difference for sway area) during quiet standing, they presented differences in sway area during the prolonged standing task ( P < .001). Conclusions Prolonged standing task reduced adaptability of the postural control system in pwPD. In addition, the prolonged standing task may better analyze the adaptability of the postural control system in pwPD.

Postural sway refers to the fluctuations in the horizontal movements of the center of mass (COM) while a human stands quietly. The fluctuations in the center of pressure (COP) measured with a force platform provide a measure of the neuromuscular response to the motions of the COM.

We assessed 168 patients with multiple sclerosis (MS) by force platform to obtain the dual-task cost (DTC) of balance, that is, the change in postural sway from quiet standing to dual-task condition (Stroop test). After a median follow-up time of 3.5 years from this assessment, disability progression occurred in 45 (27%) patients. Disability progression was predicted by the adoption of a ‘posture second’ strategy, that is, values of DTC of balance exceeding those obtained from 62 healthy controls, even after controlling by demographic and clinical characteristics. The DTC of balance may potentially represent a novel and easy tool to predict MS progression.

Methods used to assess quiet standing in unilateral prosthesis users often assume validity of an inverted pendulum model despite this being shown as invalid in some instances. The aim of the current study was to evaluate the validity of a proposed unilaterally-constrained pin-controller model in explaining postural control in unilateral prosthesis users. Prosthesis users were contrasted against the theoretical model as were able-bodied controls that stood on a platform which unilaterally constrained movement of the CoP. All participants completed bouts of quiet standing with eyes open, eyes closed and with feedback on inter-limb weight bearing asymmetry. Correlation coefficients were used to infer inverted pendulum behavior in both the anteroposterior and mediolateral directions and were derived from both kinematic (body attached markers) and kinetic (centre of pressure) experimental data. Larger, negative correlation coefficients reflected better model adherence, whilst low or no correlation reflected poorer model adherence. Inverted pendulum behavior derived from kinematic data, indicated coefficients of high magnitude in both mediolateral (all cases range 0.71–0.78) and anteroposterior (0.88–0.91) directions, irrespective of groups. Inverted pendulum behavior derived from kinetic data in the anteroposterior direction indicated validity of the model with large negative coefficients associated with the unconstrained/intact limbs (prosthesis users: − 0.45 to − 0.65, control group: − 0.43 to − 0.72), small coefficients in constrained/prosthetic limbs (prosthesis users: − 0.02 to 0.07, control group: 0.13–0.26) and large negative coefficients in combined conditions (prosthesis users: − 0.36 to − 0.56, control group: − 0.71 to − 0.82). For the mediolateral direction, coefficients were negligible for individual limbs (0.03–0.17) and moderate to large negative correlations, irrespective of group (− 0.31 to − 0.73). Data suggested both prosthesis users’ and able-bodied individuals’ postural control conforms well to that predicted by a unilaterally-constrained pin-controller model, which has implications for the fundamental control of posture in transtibial prosthesis users.

[Purpose] To examine the influence of dorsolateral prefrontal cortex (DLPFC) activation, ankle muscle activities, and coactivation on postural steadiness during dual-tasks. [Participants and Methods] A total of 14 participants (8 males, 6 females) were included. The participants stood straight on the force plate, and performed 3 different tasks: 1) a quiet standing (single-task), 2) a repetition of a number (dual-task 1: DT1), and 3) a serial subtraction (dual-task 2: DT2). We divided the participants into 2 groups (S and L group) according to whether their center of pressure paths in the dual-tasks were shorter or longer than those in the single-task. The EMG activity of the gastrocnemius lateralis and tibialis anterior were measured; the oxygenated hemoglobin (oxy-Hb) level in the DLPFC were measured using fNIRS. [Results] The results revealed that oxy-Hb in the left DLPFC increased significantly in all participants during DT2 compared to a single-task. Further, we found that the S group exhibited a higher rate of tibialis anterior activity and ankle muscle coactivation than the L group during DT2. [Conclusion] We concluded that the increase of the DLPFC activation varied with the dual-tasks; moreover, younger individuals modulate their standing posture using different strategies for posture steadiness during posture-calculating task.

Fall risk is a serious problem especially for the elderly. Fall accident causes fracture, and it leads to bedridden. Early detection of balance inability and rehabilitation training is important to decrease the risk. Quiet standing test is one of the physical tests to assess the balance inability of human. When the human is standing, he/she controls the plantar force to keep the balance. Center of pressure (COP) is the representative parameter to explain the plantar force movement. During the quiet standing test, COP fluctuates unconsciously. There are many researches that analyze the relationship between the COP fluctuation and balance inability. Many statistical indicators have been developed to assess the fluctuation specification.In contrast, several researchers have been tried to reveal the COP fluctuation mechanism by introducing stochastic mathematical model. Ornstein-Uhlenbeck process and diffusion equation are often introduced to the model. The mathematical models have been developed, and analyzed how visual input is related to the model parameters. If the mathematical model can explain the COP fluctuation completely, it becomes easier to assess the balance ability by comparing the model parameters.However, statistical indicators are still used in the clinical cases, thus there is room to discuss which statistical indicators to be used for assessment. The purpose of this research is to explore the relationship between statistical indicators and numerical model by evaluating whether the numerical model reproduces the same values with real data. The reproduced indicators and original indicators are compared, and the magnitude of the errors are evaluated.

Purpose: The aim of the study was to compare the results of six balance tests collected on AMTI AccuSway Plus ACS force platform between healthy female and male children and adolescents. We also searched for possible correlation of the balance measures with subjects’ age. Methods: 228 healthy 6- to 18-year-old subjects (111 boys and 117 girls) participated in the study. Six balance tests were performed with the use of AMTI AccuSway Plus ACS platform: quiet standing for 30s, maximal voluntary sways of the body in the sagittal plane (anterior-posterior – AP test) for 30 s, and in the frontal plane (left-right – ML test) for 30s. All tests were performed in two conditions: eyes open and eyes closed. Results: During quiet standing with eyes open, most balance measures were lower in girls (p < 0.05). In AP and ML tests with eyes open, a few balance parameters were different between boys and girls (p < 0.05). In quiet standing, AP and ML tests with eyes closed, there were no between-gender differences (p > 0.05). In quiet standing with eyes open and closed most balance parameters were negatively correlated with age (p < 0.05). Conclusions: Quiet standing postural sway characteristics depended on gender under normal visual conditions and it was similar in boys and girls under visual deprivation conditions. The vision was differently used by females and males in balance tasks. Static postural stability improved with age regardless of visual conditions.

Made available in DSpace on 2020-12-12T02:20:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-15 The aim of this study was to investigate the effects of wearing virtual reality head-mounted goggles (VR) on body sway in young adults. We run two experiments, in which we compared the body sway while standing during the conditions of 1) wearing and non-wearing VR with eyes-opened (experiment #1), 2) wearing and no-wearing VR with eyes-closed (experiment #2), and 3) wearing VR with eyes-opened when the scene was turned on and off (experiment #2). Forty-four (experiment #1) and fifteen (experiment #2) young adults were instructed to remain as still as possible on a force plate for 60-s and performed three trials in each quiet standing condition. The center of pressure (CoP) displacement, mean velocity, root mean square (RMS), area and median frequency of sway were calculated in both experiments. In the experiment #1, wearing VR condition with eyes-opened largely increased the AP and ML CoP displacement, AP mean velocity, AP and ML RMS, and area (p < 0.05) compared to non-wearing VR with eyes-opened. In the experiment #2, no differences were found for any conditions (eyes-closed and eyes-opened with turned on and off VR scene). In conclusion, wearing VR head-mounted goggles increased body sway of young adults during standing postural task, when the individuals were with eyes-opened. However, the effects of wearing VR head-mounted goggles on body sway disappeared when the individuals were with eyes-closed or the google scene was turned off the scene compared to not wearing VR head-mounted goggles with eyes-closed or turned on scene, respectively. São Paulo State University (UNESP) Human Movement Research Laboratory (MOVI-LAB) Graduate Program in Movement Science Department of Physical Education, Campus Bauru São Paulo State University (UNESP) Laboratory of Information Vision and Action (LIVIA) Graduate Program in Movement Science Department of Physical Education, Campus Bauru São Paulo State University (UNESP) Department of Physical Therapy and Occupational Therapy University of São Paulo (USP) School of Arts Sciences and Humanities (EACH), Campus São Paulo São Paulo State University (UNESP) Human Movement Research Laboratory (MOVI-LAB) Graduate Program in Movement Science Department of Physical Education, Campus Bauru São Paulo State University (UNESP) Laboratory of Information Vision and Action (LIVIA) Graduate Program in Movement Science Department of Physical Education, Campus Bauru São Paulo State University (UNESP) Department of Physical Therapy and Occupational Therapy