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Hatice Mujde Ayık and Michael J. Griffin

oscillation of a platform in the mediolateral axis of walking subjects, their postural stability was similar when motions had the same velocity, irrespective of the frequency of oscillation in the range 0.5 to 2 Hz. 15 Apart from quantifying motions to predict walking instability, discomfort, or difficulty

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Cameron T. Gibbons, Polemnia G. Amazeen and Aaron D. Likens

purpose of this study is to compare controlled and self-selected foot placement procedures and to understand the role that natural foot positioning plays in the control of posture during anteroposterior (AP; front-back) and mediolateral (ML; side-to-side) stances (see Figure  1 ). Figure 1 —Foot placement

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Joanna B. Morley, Leslie M. Decker, Tracy Dierks, Daniel Blanke, Jeffrey A. French and Nicholas Stergiou

Despite extensive research on running mechanics, there is still a knowledge gap with respect to the degree of relationship between mediolateral ground reaction forces (ML-GRF) and foot pronation. Our goal was to investigate whether differences exist in ML-GRF among runners that exhibit different degrees of pronation. Seventeen male and 13 female recreational runners ran with and without shoes while ML-GRF and frontal kinematics were collected simultaneously. Subjects were divided into groups based upon their peak eversion (low pronation, middle pronation, high pronation). Discrete parameters from the ML-GRF were peak forces, respective times of occurrence, and impulses. No significant differences were found between groups regarding the magnitude of ML-GRF. Based upon the relative times of occurrence, the peak medial GRF occurred closer to the peak eversion than the peak lateral GRF. Findings support the idea that the ML-GRF have less to do with pronation than previous research suggested.

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Eric Yiou and Manh-Cuong Do

This study examined how the central nervous system organizes mediolateral (ML) “anticipatory postural adjustments” (APAs) for stepping initiation (SI) to take into account the postural perturbation induced by voluntary lateral arm raising. Subjects purposely stepped in isolation (“isolated stepping”) or in combination with lateral raising of dominant arm (“motor sequence”). SI was carried out with the leg ipsilateral or controlateral to raising arm. Results showed that APA amplitude increased from “ipsilateral isolated stepping” to “ipsilateral sequence”, but did not change in conditions involving controlateral leg; ML instability increased from “ipsilateral isolated stepping” to “ipsilateral sequence”, but decreased from “controlateral isolated stepping” to “controlateral sequence”. These changes were exacerbated when inertia was added at the hand during raising. These results suggest that APAs for SI are globally scaled as a function of the biomechanical consequences of forthcoming arm movement on ML postural stability.

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Noah J. Rosenblatt, Christopher P. Hurt and Mark D. Grabiner

Recent experimental findings support theoretical predictions that across walking conditions the motor system chooses foot placement to achieve a constant minimum “margin of stability” (MOSmin)—distance between the extrapolated center of mass and base of support. For example, while step width varies, similar average MOSmin exists between overground and treadmill walking and between overground and compliant/irregular surface walking. However, predictions regarding the invariance of MOSmin to step-by-step changes in foot placement cannot be verified by average values. The purpose of this study was to determine average changes in, and the sensitivity of MOSmin to varying step widths during two walking tasks. Eight young subjects walked on a dual-belt treadmill before and after receiving information that stepping on the physical gap between the belts causes no adverse effects. Information decreased step width by 17% (p = .01), whereas MOSmin was unaffected (p = .12). Regardless of information, subject-specific regressions between step-by-step values of step width and MOSmin explained, on average, only 5% of the shared variance (β = 0.11 ± 0.05). Thus, MOSmin appears to be insensitive to changing step width. Accordingly, during treadmill walking, step width is chosen to maintain MOSmin. If MOSmin remains insensitive to step width across other dynamic tasks, then assessing an individual’s stability while performing theses tasks could help describe the health of the motor system.

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Yuko Kuramatsu, Yuji Yamamoto and Shin-Ichi Izumi

were free from control. Therefore, the anteroposterior direction (i.e., the advancing direction of whole-body movements that include walking and standing up) should be more strongly controlled than the mediolateral direction. However, individuals with hemiparesis have impairments that affect one side

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

pressure acts on the foot. 14 During the stance phase of the gait, the COP shifts primarily in the posterior-to-anterior direction. Displacements of the COP in the mediolateral direction when walking are indicative of perturbations of foot stability. 15 During running, COP deviations have been associated

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Kai Yan Lui, Patricia Hewston and Nandini Deshpande

mass; AP = anteroposterior. Mediolateral control Peak-to-peak trunk roll angle (in degrees), peak-to-peak mediolateral (ML) COM displacement (in centimeters), and peak-to-peak ML COP (center of pressure) displacement (in centimeters) were computed. Peak-to-peak trunk roll angle allowed for the direct

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Matt Greig, Hannah Emmerson and John McCreadie

Global Positioning System (GPS) technology offer potential to quantify mechanical loading during functional rehabilitative tasks. Recently, mediolateral loading imbalances were highlighted in a case study of ankle sprain injury in elite male soccer. 11 However, to enhance the clinical application of GPS

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

entropy. We hypothesized that children with ASD would demonstrate lower complexity of COP during quiet standing with lower values of entropy in both the anteroposterior and mediolateral directions. We further expected that perturbations in visual and somatosensory information could reduce the complexity