The formation of trajectories during goal-oriented locomotion in humans. I. A stereotyped behaviour

Area of Science:

• Biomechanics
• Human Movement Science
• Robotics

Background:

• Human locomotion involves complex coordination of multiple body segments.
• Previous research on arm reaching movements has revealed stereotyped trajectory properties.
• Understanding the control mechanisms of human locomotion is crucial for various applications, including robotics and rehabilitation.

Purpose of the Study:

• To investigate the planning and control strategies underlying goal-oriented human locomotion.
• To compare the kinematic properties of human locomotion with those of arm reaching movements.
• To test the hypothesis that locomotion is planned as a sequence of steps versus a whole-body trajectory.

Main Methods:

• Subjects performed a goal-oriented locomotion task, walking to and through doorways at various locations and orientations.
• Kinematic data of whole-body trajectories, including path geometry and velocity profiles, were recorded.
• Analysis focused on comparing the consistency of whole-body trajectories versus individual foot placements across multiple trials.

Main Results:

• Despite variations in foot placement, subjects exhibited highly consistent whole-body trajectories (path geometry and velocity profiles) when walking to a target.
• The stereotyped nature of locomotion trajectories mirrors findings from arm reaching movement studies.
• Inconsistent foot placement across repetitions suggests that locomotion is not planned as a simple sequence of steps.

Conclusions:

• Common underlying control mechanisms may govern both whole-body locomotion and arm reaching movements.
• Goal-oriented locomotion appears to be planned and controlled as a unified whole-body trajectory rather than a series of discrete steps.
• These findings have implications for understanding motor control and developing more naturalistic robotic movement systems.