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A Critical Review of Position- and Velocity-Based Concepts of Postural Control During Upright Stance

100%
Portela F. M., Rodrigues E. C., Sá Ferreira A. d.
Human Movement
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2014
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vol. 15
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issue 4
227-233
EN
Purpose. Postural control during quiet standing has been modeled by concepts using kinematic variables estimated from center of pressure (COP) signals. The concept of position-based postural control has had particular ramifications in the literature, although a more recent concept of velocity-based control has been proposed as being more relevant. Methods. This study reviews the literature investigating these concepts and their respective quantitative methods alongside current supporting evidence and criticisms. Results. The position-based control concept suggests the existence of two control loops that alternate whenever certain thresholds are exceeded. Such a theory is supported by studies describing the time delay between the skeletal muscle activation and CoP displacement. However, this concept has been criticized to be the result of statistical artifacts due to it not being adapted to the analysis of bounded time series. Conversely, the velocity-based control concept claims that velocity is the most relevant kinematic variable for postural control. Such a theory suggests that postural adjustments are executed to change the trajectory of the CoP whenever the velocity crosses a threshold. Both theories have their major methodological limitations, while interpretation of data from the position-based concept is difficult, velocity-based thresholds are empirical and still need verification in different motor tasks and populations. Conclusions. Given the observed similarities and mutual exclusivity of both concepts, there is a need for the development of methods that can quantitatively analyze stabilometric signals while simultaneously considering both kinematic variables.
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The Effects of a Perturbation-Based Balance Training on the Reactive Neuromuscular Control in Community- -Dwelling Older Women: A Randomized Controlled Trial

88%
Rossi L. P., Pereira R., Brandalize M., Gomes A. R. S.
Human Movement
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2013
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vol. 14
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issue 3
238-246
EN
Purpose. The purpose of this study was to evaluate the effects of short-term perturbation-based balance training and a detraining period on postural control in older adults. Methods. A group of healthy older women were recruited and divided into two groups: an exercise group (EG, n = 21, age = 67.0 ± 2.0 y) that performed balance-based exercises three times a week over a sixweek period and a control group (CG, n = 20, age = 67.9 ± 3.1 y). Center-of-pressure displacement (CoP) and electromyographic data (EMG onset, time-to-peak and amplitude) were assessed during forward and backward perturbations for six leg muscles. All variables were analyzed before the training program began, at its end, and after a six-week period of detraining. A mixed ANOVA model was used to analyze the within- and between-subject results. Results. A decrease in backward CoP displacement, EMG onset and time-to-peak of the ankle muscles, especially the tibialis anterior (TA) and gastrocnemius (MG), was observed. Improvement in muscle EMG amplitude for the ankle muscles (TA, MG and Soleus - SO) at the early phase (0-200 ms) of the perturbation test, with the SO also showing an increase in amplitude at the intermediate phase (201-400 ms). After the detraining period, only the TA muscle maintained an improvement in reaction time. Conclusions. Perturbation-based balance training improved neuromuscular responses such as muscle reaction time and ankle muscle activation and consequently aided the body’s ability to maintain correct center of pressure, although after a period of detraining this gain was not maintained for most of the assessed variables.
3
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Control of static balance among women after mastectomy. Vision impact on the quality of the equilibrium response

63%
Rachwał M., Drzał-Grabiec J., Walicka-Cupryś K., Truszczyńska A.
Advances in Rehabilitation
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2013
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vol. 27
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issue 3
9-16
EN
Introduction: Structural stability assess of the impact of the sense of the reactions equivalent. The aim of this study was to determine the importance of maintaining control patterns in static equilibrium of women after mastectomy. Materials and methods: The study included 150 women. In the first group there were 75 women after mastectomy, mean age 60 (±7,6), mean BMI 26 (±3,6). In the control group there were 75 age matched women (59 (±6,5), BMI 26 (±7,9) without a history of cancer diseases. The study was conducted using a tensometric platform. Quantification was composed of two 30-second test, the first test with eyes open and a second after 5-10 second pause with eyes closed. Results: It was found that there were significant statistical differences within a significant part of the measured parameters with eyes closed, and for all the Romberg parameters. There were: COP (centre of pressure) path length (p = 0.0411), the COP path length measured in the anterior-posterior direction (p = 0.0251), the average tilt COP (p = 0.0025), the maximum swing in the x-axis (relating to the range lateral stability) (p = 0.0447). In addition, there were statistically significant differences between the parameters: the average speed of a moving 2D COP (p = 0.0432) and the y-axis (p = 0.0240). Conclusion: Balance after mastectomy was less dependent on the vision than in the control group. Physiotherapy program after mastectomy should include proprioceptive training, with closed eyes to improve the equilibrium reaction quality and increase the postural stability.
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