Postural strategy to keep balance on the seesaw

Area of Science:

• Biomechanics
• Neuroscience
• Human Motor Control

Background:

• Maintaining upright balance is crucial for daily activities.
• Seesaws present a dynamic challenge to postural stability.
• Understanding the neural control of balance is key to rehabilitation.

Purpose of the Study:

• To investigate the kinematic and electromyography (EMG) strategies used by the central nervous system (CNS) for anterior-posterior balance on seesaws.
• To determine how varying degrees of seesaw instability affect balance control mechanisms.
• To identify the primary joints and muscles involved in maintaining equilibrium.

Main Methods:

• Utilized a 3D motion-analysis system to reconstruct joint kinematics (hip, knee, ankle).
• Recorded electromyography (EMG) activity from key ankle, knee, and hip muscles.
• Assessed balance control strategies across seesaws with different instability levels.

Main Results:

• Balance was predominantly maintained through ankle joint adjustments.
• Alternating agonist and antagonist bursts were observed in gastrocnemius and anterior tibialis muscles.
• Muscles around the knee and hip exhibited generalized co-activation with minimal movement, suggesting neural or biomechanical constraints.
• The balance strategy was qualitatively similar across different instability conditions.

Conclusions:

• The ankle joint plays a primary role in maintaining anterior-posterior balance on seesaws.
• Specific muscle activation patterns (agonist/antagonist bursts, co-activation) are employed by the CNS for equilibrium control.
• The CNS utilizes a consistent balance strategy regardless of the seesaw's instability level, indicating robust control mechanisms.