The difficulty of the postural control task affects multi-muscle control during quiet standing.

Area of Science:

• Neuroscience
• Biomechanics
• Human Movement Science

Background:

• Understanding muscle coordination is crucial for postural control.
• Electromyographic (EMG) coherence analysis reveals neural coupling between muscles.

Purpose of the Study:

• To compare electromyographic (EMG) coherence between lower limb and core muscles during postural tasks of varying difficulty.
• To investigate neural input sharing in muscle synergies during bipedal and unipedal standing.

Main Methods:

• Recorded EMG signals from 20 healthy males during bipedal and unipedal quiet standing.
• Analyzed EMG-EMG coherence (single-pair and pooled estimations) in the 0-5 Hz frequency band.

Main Results:

• Significant EMG-EMG coherence was found in the 0-5 Hz band for core, anterior, posterior, and antagonist muscle pairs.
• Low-frequency neural inputs (0-5 Hz) are shared between core and antagonist muscles, potentially aiding M-mode assembly.
• Muscle synergies differed between bipedal and unipedal stance tasks.

Conclusions:

• Core muscles provide essential synergy for spine stability during balancing.
• Shared low-frequency neural inputs suggest a coordinated control strategy for postural tasks.
• Task difficulty and stance type (bipedal vs. unipedal) modulate muscle synergy formation and neural coupling.