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Updated: May 14, 2026
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Experimental Methods to Study Human Postural Control
Published on: September 11, 2019
Correlation dimension estimates of human postural sway.
1Department of Engineering Sciences, Middle East Technical University, 06800 Ankara, Turkey. senih@metu.edu.tr
Human Movement Science
|January 30, 2013
Summary
Human postural sway dynamics are complex, with ergodic theory revealing age-related changes. Nonlinear metrics show aging affects control of multiple degrees of freedom in quiet standing.
Area of Science:
- Biomechanics
- Dynamical Systems Theory
- Human Physiology
Background:
- Human postural sway during quiet standing is complex, exhibiting both stochastic and deterministic properties.
- Previous methods like linear system identification and stochastic analysis have not fully captured the global dynamics of quiet stance.
- Ergodic theory offers a novel approach to analyze the statistical characteristics of postural sway.
Purpose of the Study:
- To apply ergodic theory to explore the statistical characteristics of human postural sway dynamics across different age groups (children, adults, elderly).
- To investigate age-related differences in the complexity and control of postural sway using nonlinear metrics.
- To determine if aging affects the ability to independently control multiple degrees of freedom during quiet standing.
Main Methods:
- Collected center of pressure (CoPx) time series data from 28 subjects across four age groups during quiet standing.
- Applied Run Test to assess signal stationarity and ergodic properties.
- Computed nonlinear metrics, including correlation dimension (Dk), to quantify postural sway complexity.
- Analyzed differences in these metrics across age groups.
Main Results:
- 97% of trials were stationary, but children and elderly groups showed significant nonstationary behavior.
- Linear metrics did not reveal age-related differences in CoPx dynamics.
- Nonlinear metrics (τcritical, msaturated, Dk estimates) showed significant age-related differences.
- Elderly subjects exhibited higher Dk estimates (4.12±0.59) compared to children and adults (3.67±0.28).
Conclusions:
- Human quiet standing exhibits multi-degree-of-freedom dynamics with a fractal structure and embedded noise, individually characterized.
- Ergodic theory and nonlinear metrics effectively reveal age-related changes in postural control.
- Aging significantly impacts the ability to independently control multiple degrees of freedom during quiet standing.
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