Difference between voluntary control and conscious balance processing during quiet standing

Area of Science:

• Biomechanics
• Human Motor Control
• Neuroscience

Background:

• Postural threat, such as standing at height, alters postural sway.
• The underlying mechanisms, voluntary control (VC) versus conscious balance processing, remain unclear.
• Understanding these mechanisms is crucial for explaining balance adjustments under stress.

Purpose of the Study:

• To differentiate the effects of voluntary control (VC) and high-conscious movement processing (high-CMP) on postural control during quiet standing.
• To investigate whether VC or conscious balance processing better explains postural sway changes under threat.

Main Methods:

• Twenty-seven healthy adults performed quiet standing tasks under three conditions: relaxed, VC, and high-CMP.
• Postural sway was assessed using center of pressure (COP) measurements (anteroposterior and mediolateral directions) via a stabilometer.
• Analysis included mean power frequency (MPF), high frequency (HF), and root mean square (RMS) of COP data.

Main Results:

• Both VC and high-CMP conditions exhibited lower sway amplitude and higher sway frequency compared to the relaxed condition.
• The VC condition showed significantly higher mediolateral MPF and HF than the high-CMP condition.
• Anteroposterior MPF was higher, while RMS and low frequency were lower in both VC and high-CMP conditions versus relaxed.

Conclusions:

• Voluntary control strategies, characterized by higher sway frequency, appear to be a key mechanism underlying postural adjustments under threat.
• The findings suggest that voluntary control may be more akin to postural control under threat than conscious balance processing alone.
• These results contribute to understanding the neural and motor strategies employed for maintaining balance in challenging situations.