Models of Postural Control: Shared Variance in Joint and COM Motions

Area of Science:

• Biomechanics
• Human Physiology
• Motor Control

Background:

• Postural control is crucial for maintaining upright stance.
• Understanding the coordination of multiple joints in balance is essential.
• Previous models simplified the degrees of freedom (DOF) in postural control.

Purpose of the Study:

• To investigate the organization of the human postural control system during upright stance.
• To analyze the shared variance between joint and center of mass (COM) motions using canonical correlation analysis (CCA).
• To evaluate how different degrees of freedom (DOF) in postural control models influence balance.

Main Methods:

• Multivariate canonical correlation analysis (CCA) was used to analyze joint and COM motions.
• CCA was applied to models with varying degrees of freedom (DOF): 2DOF (ankle), 4DOF (ankle-hip), 5DOF (ankle-knee-hip), and 7DOF (ankle-knee-hip-neck).
• Healthy adults performed quiet stance and voluntary sway tasks on rigid and foam surfaces.

Main Results:

• Increased DOF in postural control models progressively enhanced shared variance with COM motion.
• The 7DOF model demonstrated greater involvement of all joints during challenging one-leg stances and dynamic tasks.
• Shared variance increased during dynamic conditions, indicating reduced dimensionality in postural control.

Conclusions:

• Multi-DOF postural control mechanisms significantly contribute to human balance.
• The study provides direct evidence for the degeneracy of multivariate joint regulation in postural control.
• Stance and surface conditions influence the complex interplay of joint regulation for maintaining balance.