Muscle synergy stability and human balance maintenance

Area of Science:

• Neuroscience
• Biomechanics
• Motor Control

Background:

• The precise neural control mechanisms for human movement remain incompletely understood.
• Muscle synergy theory posits that the central nervous system (CNS) utilizes a limited set of motor commands to generate diverse movements.
• While muscle synergies exhibit temporal stability, inherent variability exists, influencing motor performance.

Purpose of the Study:

• To investigate the variability of muscle synergies during postural control.
• To introduce and validate a Synergy Stability Index (SSI) for quantifying muscle synergy variability.
• To establish the relationship between muscle synergy stability and an individual's ability to maintain balance.

Main Methods:

• Electromyography (EMG) was used to record muscle activity during lateral balance tasks with induced platform disturbances.
• Non-negative Matrix Factorization (NMF) was employed to decompose EMG data and identify muscle synergies related to postural reflexes and automatic responses.
• A Synergy Stability Index (SSI) was calculated based on the identified muscle synergies.

Main Results:

• A significant positive correlation was observed between balance performance and the Synergy Stability Index (SSI).
• Individuals demonstrating superior balance control exhibited more invariant (stable) muscle synergies.
• Conversely, participants with less adept balance control displayed more variable muscle synergies.

Conclusions:

• The Synergy Stability Index (SSI) provides a quantitative measure for assessing balance maintenance capabilities.
• Muscle synergy stability is a key factor underlying effective postural control and balance.
• This research offers insights into the neural strategies employed for maintaining upright stability.