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Surface height effects on postural control: a hypothesis for a stiffness strategy for stance.
M G Carpenter1, J S Frank, C P Silcher
1University of Waterloo, Ontario, Canada.
Journal of Vestibular Research : Equilibrium & Orientation
|September 3, 1999
Summary
Balance confidence affects upright stance control. Reduced vision and vestibular input on elevated surfaces altered postural sway, suggesting vision enhances ankle stiffness to maintain stability when balance confidence is low.
Area of Science:
- Biomechanics
- Human Motor Control
- Sensory Integration
Background:
- Upright stance control is crucial for safety and mobility.
- Balance confidence, or perceived safety, may influence postural control strategies.
- Sensory inputs (visual, vestibular, somatosensory) are vital for maintaining balance.
Purpose of the Study:
- To investigate the role of balance confidence in upright stance control.
- To examine how reduced visual and vestibular inputs affect postural control on elevated surfaces.
- To determine gender-specific differences in postural responses.
Main Methods:
- Twenty-eight adults stood on low and high platforms with varying visual and vestibular conditions.
- Postural control was assessed using center of pressure (COP) measures: amplitude variability (RMS) and mean power frequency (MPF).
- Visual input was manipulated (eyes open/closed), and vestibular input reduced via head extension.
Main Results:
- Surface height and vision interacted to influence COP RMS and MPF.
- Higher surfaces with vision decreased RMS and increased MPF, indicating greater stability.
- Reduced vestibular input increased RMS, suggesting reliance on other sensory systems and potential ankle stiffness adjustments.
Conclusions:
- Postural control is modulated by sensory input availability and surface height.
- Vision plays a key role in enhancing ankle stiffness, particularly when balance confidence is challenged.
- Gender differences in postural responses were observed under specific sensory conditions.