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Weight Lifting and Training
Published in Christopher L. Vaughan, Biomechanics of Sport, 2020
Garhammer133 utilized force-plate measurements to study the movement of the center of pressure (CP) on one foot during snatch lifts. For most subjects CP was found to move rapidly from the ball-of-foot/mid-foot area to the heel and back toward the toes during the transition from the first to the second pull. This CP movement was related to use of the DKB pulling method and seemed to be quantitatively related to the extent of horizontal bar movement during the pull. One subject who had difficulty in completing his lifts had a straighter bar trajectory and little movement of the CP from the ball of his foot. Data presented in other studies using a force plate show that extensive anterior-posterior CP shifts take place during snatch and clean pulls,76,134 but the authors do not discuss this parameter.
Biomechanical Aspects of the Development of Postural Control
Published in Mark De Ste Croix, Thomas Korff, Paediatric Biomechanics and Motor Control, 2013
Jody Jensen, Renate van Zandwijk
Beyond these broad categories of dependent measures, there are some measures that are historically associated with assessments of postural control. The centre of pressure (COP) is one of these measures. COP refers to a location – the location at the interface between the body and the support surface at which the resultant ground reaction force is applied. This resultant ground reaction force is the equal and opposite force of a weighted average of all applied forces at the contact surface (Prieto et al. 1996; Winter 1990). It is a summary variable that reveals the stability/variability of a quiescent system (e.g. during quiet sitting or quiet stance (Cignetti et al. 2011; Deffeyes et al. 2009b; Kirshenbaum et al. 2001)) or information about the dynamic control of posture or gait (Winter and Eng 1995).
Biomechanical studies for understanding falls in older adults
Published in Youlian Hong, Roger Bartlett, Routledge Handbook of Biomechanics and Human Movement Science, 2008
Daina L. Sturnieks, R. Stephen
Standing balance, or postural control, has been widely studied in relation to falls. Although quiet standing appears to be simple and somewhat static, it is in fact a mechanically challenging task, involving the constant monitoring and adjustment of body motion. Standing balance motion is often likened to an inverted pendulum, the body COM moving about a pivot point at the ankles. As an inverted pendulum is unstable, relatively minor perturbations (such as breathing) cause the swaying motion. In order to maintain the body COM within the BOS, an individual produces forces on the support surface/s (predominantly under the feet while standing), to control the COM position. The point at which the sum of these forces acts on the support surface is the centre of pressure (COP). Much like a constant process of catching and throwing, forces at the support surface act to accelerate the COM in a given direction and when this motion is detected as being adverse to stability, opposing forces act to catch the falling COM and throw it in another direction. Consequently, the displacement of the COP oscillates around that of the COM (Figure 35.2) and the COP can be considered a controlling variable for balance, as it governs the horizontal acceleration of the COM (Winter et al., 1991).
Effect of Sway Frequency on the Joint Angle and Center of Pressure in Voluntary Sway
Published in Journal of Motor Behavior, 2023
Tetsuya Hasegawa, Tomoki Mori, Kohei Kaminishi, Ryosuke Chiba, Jun Ota, Arito Yozu
The center of pressure (COP) was measured using a pressure distribution measuring plates (56 × 203 cm; FDM, Zebris Medical GmbH, Germany). The sampling rate was 100 Hz. Posture was measured using an optical three-dimensional motion analysis system using 10 cameras (Kestrel, Motion Analysis, Santa Rosa, California, USA) placed around the experimental environment (Figure 1). 52 infrared reflective markers were placed with reference to CGM 2.4 marker set (Leboeuf et al., 2019). Based on the location of the markers, the trunk, pelvis, thigh, shank, and foot segments were defined. The joint angles were calculated based on the segments. The joint angles were calculated using Visual 3D Professional software (C-motion, Germantown, Maryland, USA). The calculated joint angles were for the ankle, knee, hip, and trunk. The angle of the trunk was defined as the angle between the pelvis segment and the trunk segment. The knee and ankle joints were calculated from the relative angles of adjacent segments. The sign conventions for describing the joint angles are as follows: trunk extension, positive; hip flexion, positive; knee flexion, positive; foot dorsiflexion, positive.
Anticipatory and Compensatory Postural Adjustments in Response to Dynamic Platform Perturbation during a Forward Step
Published in Journal of Motor Behavior, 2023
Yun Wang, Kazuhiko Watanabe, Tadayoshi Asaka
During standing balance control, the ability to take a step following a perturbation requires anticipatory postural adjustments (APAs) and compensatory postural adjustments (CPAs) in the activation patterns of postural muscles for body orientation and balance stabilization. APAs control the body center of mass (COM) motion to stabilize the posture associated with stepping (Horak, 2006). It is mechanically necessary to unload the stepping leg and create a moment of the vertical reaction force (McIlroy & Maki, 1993). The purpose of these adjustments is to propel the body COM forward and laterally for foot landing orientation. Correspondingly, the center of pressure (COP) shifts toward the supporting foot and in the anterior-posterior (AP) direction backward and forward for weight transfer. In contrast, CPAs serve to restore the body COM motion after the liftoff of the stepping leg. CPAs are triggered by sensory feedback information and help to safeguard stability through muscle activation after a perturbation has already occurred (Aruin et al., 2015). Therefore, CPAs deal with the actual effects of a perturbation and represent protective adjustments for preserving balance by controlling the stepping leg to match the ongoing motion of the body COM.
Diagnostic route of cervicogenic dizziness: usefulness of posturography, objective and subjective testing implementation and their correlation
Published in Disability and Rehabilitation, 2021
Alessandro Micarelli, Andrea Viziano, Ivan Augimeri, Beatrice Micarelli, Donatella Capoccia, Marco Alessandrini
Each patient was instructed to keep an upright position on a standardized platform for static posturography (ED800 Medi-Care Solutions S.R.L. Euroclinic). The recording period was 60 s for each test (eyes closed or open while standing on the stiff platform) and the sampling frequency in the time domain was 25 Hz [18,31]. The center of pressure was monitored, while performing the test. The posturographic parameters considered in our study were the trace length (length), the surface of the ellipse of confidence (surface), and the fast Fourier transform elaboration of oscillations on both the X (right-left) and Y (forward-backwards) planes [18,31]. Time-domain oscillation signals (X and Y) were extracted from the original manufacturer’s software into .txt format and the fast Fourier transform elaborations were gained through a core function implemented on Matlab space [17,31]. Spectral values (power spectra) of body oscillations were quantified on a .xls file, for every frequency from 0.0122 to 4.9927 Hz [31]. As in previous experiences [31], we subdivided the frequency spectrum into three groups: 0.0122 to 0.6958 Hz (low-frequency interval); 0.708 to 0.9888 Hz (middle-frequency interval); 1.001 to 4.9927 Hz (high-frequency interval). Within each group, the spectral intensity was determined by adding the relative power spectra and the group mean power spectra (± standard deviations) [17,18,31].