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https://hdl.handle.net/2142/21447
Description
Title
Dynamic strategies of human postural control
Author(s)
Slobounov, Semyon M.
Issue Date
1994
Doctoral Committee Chair(s)
Newell, Karl M.
Department of Study
Kinesiology and Community Health
Discipline
Kinesiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Education, Educational Psychology
Psychology, General
Psychology, Experimental
Language
eng
Abstract
The two goals pursued in this study were to identify controllable dynamic characteristics of human posture and to approach the description of these characteristics by means of computer graphics. The notion that virtual time-to-contact, which specifies the spatio-temporal proximity of the pressure center to the stability boundary is one of the controllable parameters for postural dynamics, was examined while subjects performed a variety of upright postural movements where the speed, instructions and the base of support dimensions were experimentally manipulated. The rational for the new concept of virtual time-to-contact as well as a method for its computation and visualization with respect to two-dimensional stability boundary were elaborated.
It was shown that the dynamic strategy of postural control defined by the interactive effects of environmental and task constraints channels a search for controllable parameters in relation to the organism-environment interaction. It appeared that range of postural movements, in terms of both whole body linear and angular kinematics and the center of pressure motion, is varied as a function of speed, physical dimension of the base of support and instruction, specifying additional constraints on postural dynamics. It was suggested that changes in task, experimental instruction and physical dimension of the base of support force the subjects to search for appropriate dynamic strategies in order to accommodate these task demands.
Virtual time-to-contact values and associated variables were obtained and discussed in this study in terms of the mechanism of postural control including the processes by which performers explore their operational workspace. It was shown that virtual time-to-contact appeared to be specifically sensitive to changes in task, instructional constraints, physical dimension of the base of support, movement type and change in movement direction. Therefore, virtual time-to-contact can be considered as a unique perception-action mechanism which serves as an organizing principle for postural dynamics. It seems reasonable to suggest that additional sources of informational constraints such as vision availability, manipulations of physical base of support and so forth would be the appropriate experimental designs to further explore the dynamical properties of virtual time-to-contact.
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