Postural Responses to Achilles Tendon Vibration Depend on Feet Positioning

Area of Science:

• Biomechanics
• Neuroscience
• Human Motor Control

Background:

• Mechanical vibration of the Achilles tendon (TV) is a common method for investigating proprioception's role in postural control.
• Previous studies on TV's effects on postural control have primarily focused on temporal parameters of center of pressure (CoP) and used varied foot positions.

Purpose of the Study:

• To investigate the effects of Achilles TV on both temporal and spectral characteristics of CoP motion.
• To examine how different foot positions influence the body's postural response to TV.

Main Methods:

• Eighteen healthy adults stood barefoot on a dual platform with eyes occluded.
• Achilles TV (80 Hz, 0.2-0.5 mm amplitude) was applied bilaterally for 20 seconds.
• CoP signals were analyzed in natural and standardized (15° feet angular opening) positions, during vibration (VIB), and during a recovery period (REC), examining both temporal and spectral parameters.

Main Results:

• TV significantly increased CoP velocity (mediolateral and anteroposterior) and anteroposterior displacement during the VIB phase, with progressive decreases during REC.
• Median and peak CoP frequencies increased in the mediolateral direction during VIB compared to REC.
• A standardized foot position increased CoP velocity and mediolateral displacement but did not alter spectral characteristics.

Conclusions:

• Postural control, reflected in CoP motion, demonstrates adaptation during and after Achilles TV, observable in both temporal and spectral domains.
• Foot positioning influences the temporal dynamics of CoP motion during and after TV but does not affect its spectral properties.