Human standing posture: multi-joint movement strategies based on biomechanical constraints

Area of Science:

• Biomechanics
• Human Motor Control
• Robotics

Background:

• Maintaining upright standing posture requires complex coordination of the human musculoskeletal system.
• Previous models often simplify joint dynamics, limiting insights into natural movement strategies.

Purpose of the Study:

• To develop a theoretical framework and computational model for analyzing coordination strategies in human standing posture.
• To investigate how musculoskeletal mechanics and constraints influence joint control and balance maintenance.

Main Methods:

• Developed a sagittal plane musculoskeletal model of the human lower extremity.
• Calculated the feasible acceleration set (FAS) representing muscle-induced accelerations.
• Analyzed subsets of FAS under specific joint constraints (e.g., straight knees) to identify movement strategies.

Main Results:

• Musculoskeletal mechanics make independent joint control difficult.
• A 'hip strategy' (1:3 hip to ankle movement ratio) is favored for stability with straight knees.
• The 'hip strategy' requires less muscle activation ('neural effort') than the 'ankle strategy' for horizontal center-of-mass control.

Conclusions:

• The human body's mechanics inherently favor specific coordination patterns for balance.
• The 'hip strategy' appears to be a more energy-efficient method for maintaining upright stance and balance.
• This framework provides insights into the neural control of posture and potential applications in robotics.