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Stochastic processes in postural center-of-pressure profiles
K M Newell1, S M Slobounov, E S Slobounova
1Pennsylvania State University, University Park 16802, USA. kmnl@psu.edu
Experimental Brain Research
|January 1, 1997
Summary
Postural sway, measured by center-of-pressure motion, changes with age, decreasing from childhood to adulthood and increasing in the elderly. Vision impacts sway, but a simple linear model explains the data well.
Area of Science:
- Biomechanics
- Human Movement Science
- Stochastic Processes
Background:
- Postural control is crucial for maintaining balance.
- Center-of-pressure (COP) dynamics reflect postural sway.
- Age-related changes in postural control are well-documented.
Purpose of the Study:
- To analyze the stochastic processes of COP profiles across different age groups.
- To compare the efficacy of different stochastic models in explaining COP dynamics.
- To investigate the influence of visual input on COP motion across the lifespan.
Main Methods:
- Examined COP time-evolutionary properties in 3- and 5-year-olds, young adults (20 yrs), and elderly (67 yrs).
- Subjects performed quiet upright bipedal stance with and without vision on a force platform.
- Applied stochastic process models, including a two-process random-walk and an Ornstein-Uhlenbeck model.
Main Results:
- COP motion decreased from 3-5 years to young adulthood, then increased in the elderly.
- Vision reduced COP motion in all groups except 3-year-olds.
- Both models explained significant variance, but the Ornstein-Uhlenbeck model offered a simpler explanation.
Conclusions:
- The trajectory of COP is not definitively a two-process, open- and closed-loop random-walk model.
- A linear Ornstein-Uhlenbeck dynamic equation adequately explains COP variance.
- Further research is needed to fully elucidate the stochastic properties of COP in quiet standing.