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Renee Beach Sample, Kurt Jackson, Allison L. Kinney, Wiebke S. Diestelkamp, Senia Smoot Reinert and Kimberly Edginton Bigelow

Falls occur in 33% of older adults each year, some leading to moderate to severe injuries. To reduce falls and fall-related injuries, it is important to identify individuals with subtle risk factors elevating their likelihood of falling. The objective of this study was to determine how postural sway measures differed between fallers and nonfallers under standard and dual-task conditions. Quietstanding posturography measures were collected from 150 older adults during standard, cognitive, manual, and cognitive+manual tasks, and analyzed through traditional and nonlinear analyses. Of the traditional measures, M/L sway range and 95% confidence ellipse sway area showed statistically significant differences in all 4 test conditions between fallers and nonfallers. Although the manual dual task showed the most stable balance, effect sizes demonstrated larger differences between fallers and nonfallers. Nonlinear analysis revealed M/L sample entropy and M/L α-scaling exponent differentiating between fallers and nonfallers, with the cognitive task demonstrating larger differences. Based on the results, it is recommended to: (1) apply M/L sway range and 95% confidence ellipse area, (2) use the manual task to differentiate between fallers and nonfallers when using traditional analyses, and (3) use the cognitive task and M/L alpha and M/L sample entropy when using nonlinear analyses.

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Saud F. Alsubaie, Susan L. Whitney, Joseph M. Furman, Gregory F. Marchetti, Kathleen H. Sienko and Patrick J. Sparto

, et al . A comparison of accelerometry and center of pressure measures during computerized dynamic posturography: a measure of balance . Gait Posture . 2011 ; 33 ( 4 ): 594 – 599 . PubMed ID: 21333541 doi:10.1016/j.gaitpost.2011.01.015 21333541 10.1016/j.gaitpost.2011.01.015 9. Marchetti GF

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Melissa R. Taylor, Erin E. Sutton, Wiebke S. Diestelkamp and Kimberly Edginton Bigelow

The goal of this study was to examine the effects of 3 factors and their interactions on posturography: a period of time to become accustomed to the force platform before the initiation of data collection, presence of a visual fixation point, and participant talking during testing. The postural stability of 30 young adults and 30 older adults was evaluated to determine whether any observed effects were confounded with age. Analysis of variance techniques were used to test all possible combinations of the 3 factors. We hypothesized that all 3 factors would significantly affect postural stability. For both participant groups, the results suggest that a period of time to become accustomed to the force platform before the initiation of data collection and a visual fixation point significantly affect postural control measures, while brief participant talking does not. Despite this, no significant interactions existed suggesting that the effects of these factors, which may occur in clinical testing, do not depend on each other. Our results suggest that inconsistencies in posturography testing methods have the potential to significantly affect the results of posturography, underscoring the importance of developing a standardized testing methodology.

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Senia Smoot Reinert, Allison L. Kinney, Kurt Jackson, Wiebke Diestelkamp and Kimberly Bigelow

results of all older adults has the potential to conceal meaningful differences caused by aging or various pathologies. One potential modification of the Limits of Stability test would be to incorporate a foam surface condition. Currently, quiet-standing posturography utilizes both a firm and a foam

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John R. Biggan, Forest Melton, Michael A. Horvat, Mark Ricard, David Keller and Christopher T. Ray

The understanding of prefrail and nonfrail older adults’ postural control with and without increased environmental and cognitive stress is imperative to the development of targeted interventions to decrease fall risk within these populations. Thirty-eight individuals participated in this study. Postural control testing included the Sensory Organization Test (SOT) on a NeuroCom EquiTest. Cognitive and environmental load testing was performed during Condition 6 of the SOT. Though there were no group differences on composite equilibrium score (p = .06), the cognitive task (Stroop task) impaired equilibrium scores more than the auditory or visual distracter tasks (p < .05 and p < .01) for both groups. These results suggest that both prefrail and nonfrail older adults’ postural control is reduced in demanding environments. Given these findings, the need for multimodal exercise interventions to target both physical and cognitive factors is apparent.

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Joshua Haworth, Anastasia Kyvelidou, Wayne Fisher and Nicholas Stergiou

Children with autism spectrum disorder tend to have little interest in the presence, actions, and motives of other persons. In addition, these children tend to present with a limited and overly redundant movement repertoire, often expressing hyperfixation and aversion to novelty. We explore whether this is related to a more fundamental lack of appreciation for various temporal dynamics, including periodic, chaotic, and aperiodic motion structures. Seven children with ASD (age, gender, and height matched with children without ASD) were asked to stand and watch the motion of a visual stimulus displayed on a large (55") video monitor. Gaze and posture movements were recorded and assessed using cross recurrence quantification analysis for qualities of coordination, including rate and duration of bouts of coordination. Results showed that children with ASD do not express an affinity to chaotic motion of the stimulus in the same way as children without ASD. We contend that this indifference to chaotic motion is foundational to their general disinterest in biological motion.

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Luigi Baratto, Pietro G. Morasso, Cristina Re and Gino Spada

In order to identify useful guidelines for the clinical practitioner as regards the use of static posturographic analysis, we collected a set of posrurograms from 3 groups of participants (normal participants. Parkinsonian patients, and osteoporotic patients), according to the Romberg test. From each posturogram, we extracted global parameters (in the time domain and frequency domain) and structural parameters (based on diffusion plots and sway-density plots), with a total of 38 parameters. The discriminative power of each parameter was evaluated by means of statistical analysis in relation to the condition effect (open vs. closed eyes) and the pathology effect (normal participants vs. patients). The initial set of 38 parameters was reduced to 24 by identifying clear redundancies, and then to 18 by eliminating the parameters that did not pass the condition effect with normal participants. These parameters were analyzed for reliability and discriminative power in the general framework of a biomechanic model of postural stabilization. At the end of this analysis, we suggested that a set of 4 parameters is particularly valuable in the clinical practice: 2 global parameters (sway-path and frequency band of the posturogram) and 2 structural parameters (mean value of peaks and mean inter-peak distance in the sway-density plots).

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Christopher McCrum, Katrin Eysel-Gosepath, Gaspar Epro, Kenneth Meijer, Hans H.C.M. Savelberg, Gert-Peter Brüggemann and Kiros Karamanidis

Posturography is used to assess balance in clinical settings, but its relationship to gait stability is unclear. We assessed if dynamic gait stability is associated with standing balance in 12 patients with unilateral vestibulopathy. Participants were unexpectedly tripped during treadmill walking and the change in the margin of stability (MoSchange) and base of support (BoSchange) relative to nonperturbed walking was calculated for the perturbed and first recovery steps. The center of pressure (COP) path during 30-s stance with eyes open and closed, and the distance between the most anterior point of the COP and the anterior BoS boundary during forward leaning (ADist), were assessed using a force plate. Pearson correlations were conducted between the static and dynamic variables. The perturbation caused a large decrease in the BoS, leading to a decrease in MoS. One of 12 correlations was significant (MoSchange at the perturbed step and ADist; r = −.595, P = .041; nonsignificant correlations: .068 ≤ P ≤ .995). The results suggest that different control mechanisms may be involved in stance and gait stability, as a consistent relationship was not found. Therefore, posturography may be of limited use in predicting stability in dynamic situations.

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Valentina Agostini, Emma Chiaramello and Marco Knaflitz

Static posturography provides an objective assessment of postural control by characterizing the body sway during upright standing. The center of pressure (COP) signal is recorded by a force platform, and it is analyzed by means of many different models and techniques. Most of the parameters calculated according to these different approaches are affected by relevant intra- and intersubject variability or do not have a clear physiological interpretation. Traditional approaches decompose the COP signal into anteroposterior and mediolateral time series, corresponding to ankle plantar/dorsiflexion and hip adduction/abduction, respectively. In this study we hypothesized that COP signals show inherent rotational characteristics. To verify our hypothesis we applied the rotary spectra analysis to the two-dimensional COP signal to decompose it into clockwise and counterclockwise rotational components. We demonstrated the presence of rotational components in the COP signal of healthy subjects, providing a reference data set of the spectral characteristics of these components.

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Hans-Georg Palm, Oliver Waitz, Johannes Strobel, Jens Metrikat, Birgit Hay and Benedikt Friemert

There is clear evidence that vision contributes to stabilizing posture and that large quantities of alcohol affect balance. It has, however, not yet been investigated whether and how the consumption of low doses of ethanol affects postural control and the visual system. The purpose of this study was therefore to assess the influence of low-dose alcohol intake on balance. After having performed stability tests in a sober condition, 26 healthy males were instructed to consume 0.32 g of ethanol/kg body weight. At predefined time points, blood samples were collected and stability index scores were calculated using computerized dynamic posturography. Thirty minutes after ethanol intake, blood alcohol levels reached a mean peak of 0.037%. Whereas the ability to maintain balance significantly deteriorated during eyes-open testing, it surprisingly did not decrease during eyes-closed testing. Apparently, the visual system is particularly affected by ethanol and plays a major role in maintaining postural stability.