Learning effects on muscle modes and multi-mode postural synergies

Area of Science:

• * Neuroscience
• * Motor Control
• * Biomechanics

Background:

• * The uncontrolled manifold hypothesis provides a framework for understanding how the central nervous system controls redundant motor systems.
• * Muscle synergies, groups of muscles acting together, are crucial for stabilizing key performance variables like the center of pressure (COP).
• * The transition from co-contraction to reciprocal muscle activation patterns during practice is hypothesized to improve motor control.

Purpose of the Study:

• * To investigate the effects of practice on muscle group (M-mode) composition and multi-M-mode synergies for COP stabilization.
• * To test if practice promotes a shift from co-contraction to reciprocal muscle activation patterns.
• * To determine if new M-mode sets enhance synergies for COP stabilization.

Main Methods:

• * Subjects practiced load release tasks on an unstable surface for five days.
• * Muscle modes (M-modes) and multi-M-mode synergies were assessed during stable and unstable standing conditions before, during, and after practice.
• * Analysis focused on changes in M-mode composition and synergy strength for COP stabilization.

Main Results:

• * Practice improved task performance, indicated by fewer balance losses.
• * Co-contraction M-modes decreased, while multi-M-mode synergies stabilizing COP location emerged with practice.
• * Reciprocal M-modes were observed during stable standing, while co-contraction M-modes were prevalent on unstable surfaces pre-practice.

Conclusions:

• * The central nervous system flexibly adjusts elemental variables (modes) to ensure stable performance trajectories.
• * Practice leads to modifications in M-mode composition and co-variation, strengthening synergies for COP stabilization.
• * Motor learning involves optimizing muscle activation strategies for enhanced stability and control.