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Neuromechanical interference of posture on movement: evidence from Alexander technique teachers rising from a chair.

Cacciatore, TW; Mian, OS; Peters, A; Day, BL; (2014) Neuromechanical interference of posture on movement: evidence from Alexander technique teachers rising from a chair. J Neurophysiol , 112 (3) 719 - 729. 10.1152/jn.00617.2013. Green open access

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Abstract

While Alexander technique (AT) teachers have been reported to stand up by shifting weight gradually as they incline the trunk forward, healthy untrained (HU) adults appear unable to rise in this way. This study examines the hypothesis that HU have difficulty rising smoothly, and that this difficulty relates to reported differences in postural stiffness between groups. A wide range of movement durations (1-8 s) and anteroposterior foot placements were studied under the instruction to rise at a uniform rate. Before seat-off (SO) there were clear and profound performance differences between groups, particularly for slower movements, that could not be explained by strength differences. For each movement duration, HU used approximately twice the forward center-of-mass (CoM) velocity and vertical feet-loading rate as AT. For slow movements, HU violated task instruction by abruptly speeding up and rapidly shifting weight just before SO. In contrast, AT shifted weight gradually while smoothly advancing the CoM, achieving a more anterior CoM at SO. A neuromechanical model revealed a mechanism whereby stiffness affects standing up by exacerbating a conflict between postural and balance constraints. Thus activating leg extensors to take body weight hinders forward CoM progression toward the feet. HU's abrupt weight shift can be explained by reliance on momentum to stretch stiff leg extensors. AT's smooth rises can be explained by heightened dynamic tone control that reduces leg extensor resistance and improves force transmission across the trunk. Our results suggest postural control shapes movement coordination through a dynamic "postural frame" that affects the resistive behavior of the body.

Type: Article
Title: Neuromechanical interference of posture on movement: evidence from Alexander technique teachers rising from a chair.
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1152/jn.00617.2013
Publisher version: http://dx.doi.org/10.1152/jn.00617.2013
Language: English
Additional information: © 2014 the American Physiological Society Licensed under Creative Commons Attribution CC-BY 3.0: the American Physiological Society.
Keywords: Alexander technique, balance, movement, muscle tone, posture, sit-to-stand
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
URI: https://discovery.ucl.ac.uk/id/eprint/1437138
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