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Riann M. Palmieri, Christopher D. Ingersoll, Marcus B. Stone and B. Andrew Krause

Objective:

To define the numerous center-of-pressure derivatives used in the assessment of postural control and discuss what value each might provide in the assessment of balance.

Data Sources:

MEDLINE and SPORTDiscus were searched with the terms balance, postural control, postural sway, and center of pressure. The remaining citations were collected from references of similar papers. A total of 67 references were studied.

Conclusions:

Understanding what is represented by each parameter used to assess postural control is crucial. At the present time the literature has failed to demonstrate how the variables reflect changes made by the postural-control system. Until it can be shown that the center of pressure and its derivatives actually reveal changes in the postural-control system, the value of using these measures to assess deficits in postural control is minimized.

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Cyril Burdet and Patrice Rougier

To question the relation between uni- and bipedal postural skills, 21 subjects were required to stand on a force platform through uni- and bipedal conditions. These two protocols are commonly used paradigms to assess the balance capacities of healthy and disabled patients. The recorded displacements of the center of pressure (CP) were decomposed along mediolateral and anteroposterior axes and assessed through variance positions and parameters obtained from fractional Brownian motion (fBm) modeling to determine the nature and the spatiotemporal organization of the successive controlling mechanisms. The variances underline the relative independence of the two tasks. Nevertheless, as highlighted by the fBm framework, postural correction is initiated for the unipedal stance after shorter time delays and longer covered distances. When compared to bipedal standing, one of the main characteristics of unipedal standing is to induce better-controlled CP trajectories, as deduced from the scaling regimes computed from the fBm modeling. Lastly, the control of the CP trajectories during the shortest time intervals along the anteroposterior axis appears identical for both uni- and bipedal conditions. Unipedal and bipedal standing controls should thus be viewed as two complementary tasks, each providing specific and complementary insights into the postural control organization.

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Ksenia I. Ustinova, Valery M. Goussev, Ramesh Balasubramaniam and Mindy F. Levin

To determine how arm movements influence postural sway in the upright position after stroke, interactions between arm, trunk, and center of pressure (CoP) displacements in the sagittal direction were investigated in participants with hemiparesis and healthy subjects. Participants swung both arms sagittally in either of 2 directions (in-phase, anti-phase) and at 2 speeds (preferred, fast) while standing on separate force plates. Variables measured included amplitude and frequency of arm swinging, shoulder and trunk range of motion, CoP displacements under each foot and of the whole body, and the relationships between the arm, trunk, and CoP displacements. CoP displacements under the non-paretic leg were greater than those under the paretic leg, which may in part be related to the larger amplitude of swinging of the non-paretic arm. CoP displacements under each foot were not related to arm swinging during in-phase swinging at the preferred speed in healthy subjects. When speed of arm swinging was increased, however, the CoP moved in a direction opposite to the arm movement. In contrast, in individuals with hemiparesis, CoPs and arms moved in the same direction for both speeds. During anti-phase swinging in healthy subjects, the trunk counterbalanced the arm movements, while in participants with hemiparesis, the trunk moved with the affected arm. Results show that stroke resulted in abnormal patterns of arm-trunk-CoP interactions that may be related to a greater involvement of the trunk in arm transport, an altered pattern of coordination between arm and CoP displacements, and an impaired ability of the damaged nervous system to adapt postural synergies to changes in movement velocity.

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James L. Croft, Vinzenz von Tscharner and Ronald F. Zernicke

Compliant surfaces are used to challenge postural stability, but assessments are frequently limited to summary measures of center of pressure that do not provide insights into the temporal dynamics of motor coordination. Here, we measured center-of-pressure changes on three surfaces (solid, foam, and air-filled disc) and quantified the relative timing of changes in joint angles and muscle activity with respect to center-of-pressure changes. Nine active male subjects (20–30 years old) performed ten 30-s trials of unipedal stance on each of the three surfaces. Sway range, mean sway, mean sway velocity, path length, and fitted ellipse area increased, monotonically, from solid surface to foam to air-filled disc. The number of significant cross-correlations was greater for the compliant surfaces compared with the solid surface. Muscle activity preceded changes in center-of-pressure displacement, with the type of surface affecting the magnitude of the lead in the mediolateral direction. Center of pressure was more constrained on less stable surfaces and in the mediolateral direction.

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Carolyn A. Duncan, Scott N. MacKinnon and Wayne J. Albert

The purpose of this study was to examine how wave-induced platform motion effects postural stability when handling loads. Twelve participants (9 male, 3 female) performed a sagittal lifting/lowering task with a 10 kg load in different sea conditions off the coast of Halifax, Nova Scotia, Canada. Trunk kinematics and foot center of force were measured using the Lumbar Motion Monitor and F-Scan foot pressure system respectively. During motion conditions, significant decreases in trunk velocities were accompanied by significant increases in individual foot center of pressure velocities. These results suggest that during lifting and lowering loads in moving environments, the reaction to the wave-induced postural disturbance is accompanied by a decrease in performance speed so that the task can be performed more cautiously to optimize stability.

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Hin Fong Leong, Wing-Kai Lam, Wei Xuan Ng and Pui Wah Kong

the development of stability-optimized basketball shoes. Biomechanically, stability can be measured objectively with center of pressure (COP) changes during locomotion. The COP, quantified using a force/pressure plate system or plantar pressure insole system, is the point where resultant plantar

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John Goetschius, Mark A. Feger, Jay Hertel and Joseph M. Hart

Balance and postural control relies on the integration of sensory input from visual, vestibular, and somatosensory components. Instrumented balance platforms that measure center of pressure (COP) excursions during static stance are commonly utilized to identify adaptations in balance and postural

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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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Fatemeh Azadinia, Ismail Ebrahimi-Takamjani, Mojtaba Kamyab, Morteza Asgari and Mohamad Parnianpour

, 2007 ; Reeves, Everding, Cholewicki, & Morrisette, 2006 ). One of the most common methods for assessing postural stability is to record center of pressure (CoP) excursions during quiet standing in response to balance perturbation caused by support surface manipulation (e.g., standing on a hard surface

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Yumeng Li, Melissa A. Mache and Teri A. Todd

common feature of ASD, 12 could result in activity avoidance. Most of the studies surrounding the postural stability have utilized traditional linear analyses of center of pressure (COP) and found that children with ASD demonstrated greater sway displacements, 13 , 14 sway areas, 8 , 9 SDs of sway