Postural threat increases sample entropy of postural control.

Area of Science:

• Human movement science
• Neuroscience
• Psychophysiology

Background:

• Postural threat alters standing balance, but the neural mechanisms are not fully understood.
• Attention shifts towards balance control may explain these threat-induced changes.
• Sample entropy, a measure of sway regularity, may indicate conscious versus automatic control.

Purpose of the Study:

• To investigate the effects of postural threat on sample entropy.
• To examine relationships between arousal, anxiety, attention, sample entropy, and balance.
• To explore the influence of biological sex on these threat-related responses.

Main Methods:

• Healthy adults stood on a force plate under threat and no-threat conditions.
• Measured electrodermal activity, center of pressure (COP) sample entropy, and sway characteristics.
• Assessed perceived anxiety and attention focus post-trial.

Main Results:

• Threat increased physiological arousal, anxiety, and attention to balance-related information.
• Participants exhibited increased sample entropy, forward lean, and COP displacement amplitude/frequency.
• Sex differences emerged in attention to balance and high-frequency sway, but overall responses were similar.

Conclusions:

• Increased sample entropy under threat may indicate a shift towards more automatic balance control.
• Conscious attention to balance may serve to regulate these automatic adjustments.
• Threat-induced balance changes are influenced by arousal, anxiety, and attention, with some sex-specific modulation.