Phase plane analysis of stability in quiet standing

Area of Science:

• Biomechanics
• Neuroscience
• Human Motor Control

Background:

• Standing balance relies on complex postural control mechanisms.
• Evaluating balance typically involves analyzing center of gravity (CG) and center of pressure (CoP) displacement.
• The dynamic interplay between position and momentum in balance control remains an area for detailed investigation.

Purpose of the Study:

• To investigate standing balance control in healthy subjects and individuals with bilateral vestibular hypofunction (BVH).
• To determine the efficacy of phase plane plots in characterizing dynamic balance control.
• To explore how base of support and visual information influence postural stability.

Main Methods:

• Analyzed standing balance using phase plane plots (velocity vs. displacement) of the whole body center of gravity (CG) and center of pressure (CoP).
• Included 11 healthy subjects and 15 subjects with BVH.
• Manipulated postural stability by altering base of support (feet wide apart, feet together, semitandem stance) and visual input (eyes open/closed).

Main Results:

• Phase plane plots demonstrated changes in stability with altered base of support and visual input.
• Significant differences in stability measures were observed between healthy controls and the BVH group.
• Root mean square variance of velocity and displacement, quantified from phase plane plots, showed significant differences between conditions and groups.

Conclusions:

• Phase plane plots integrating displacement and velocity provide a more comprehensive characterization of balance control than either measure alone.
• This dynamic analysis method is sensitive to changes in postural stability induced by altered sensory input and base of support.
• Phase plane analysis effectively differentiates balance control strategies between healthy individuals and those with BVH.