The effect of foam surface properties on postural stability assessment while standing.

Area of Science:

• Biomechanics
• Human Motor Control
• Sensory Integration

Background:

• Postural control assessment commonly uses compliant foam surfaces to challenge balance.
• Variability in foam physical properties (density, elastic modulus) across studies complicates result interpretation.
• Understanding foam properties' influence is crucial for standardizing balance testing.

Purpose of the Study:

• To investigate the effect of foam density and elastic modulus on anteroposterior (AP) and lateral torque variance.
• To determine if these effects differ with eyes open versus eyes closed conditions.
• To explore the interaction between visual input and foam properties in postural control.

Main Methods:

• Thirty healthy adults performed posturography on three foam blocks (firm, medium, soft) varying in elastic modulus.
• Torque variance was calculated for total body movements and specific frequency bands (<0.1Hz, >0.1Hz).
• Generalized Linear Models (GLM) and correlation analyses were used to assess relationships between foam properties and movement variance.

Main Results:

• Higher frequency torque variances (>0.1Hz) increased with foam firmness (firm > medium > soft), particularly with eyes closed.
• Foam properties significantly affected AP torque variance (>0.1Hz) and lateral torque variance across all frequencies.
• The stabilizing effect of vision was more pronounced as postural challenge increased with firmer foams.

Conclusions:

• Foam properties demonstrably influence measured body movements during balance tasks.
• Caution is advised when interpreting balance deficits from foam-based tests due to variability in foam characteristics.
• Standardization of foam properties is recommended for reliable and comparable postural control research.