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Predictive control of body mass trajectory in a two-step sequence.
1MRC Human Movement Group, Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London, WC1 N 3BG, UK.
Experimental Brain Research
|October 14, 2004
Summary
Human body trajectory control during stepping relies on a predictive, ballistic "throw." This strategy primarily focuses on leading foot placement, not final body position, enabling a safe one-step-at-a-time approach.
Area of Science:
- Biomechanics
- Motor Control
- Human Movement Science
Background:
- Stepping involves a brief period of falling when a foot is lifted.
- The central nervous system may control body trajectory via a predictive, ballistic movement before the step.
- Understanding the predictive capacity of this 'body throw' is crucial for analyzing stepping dynamics.
Purpose of the Study:
- To investigate the proposed ballistic 'body throw' model of stepping.
- To determine how far into the future body trajectory is predetermined by this initial throw.
- To examine the relationship between the body throw, leading foot placement, and final center-of-mass (CoM) position.
Main Methods:
- Measured body center-of-mass (CoM) and foot trajectories during two-step sequences.
- Utilized illuminated targets to guide leading foot placement.
- Spatially varied targets to dissociate leading foot placement from final CoM position.
Main Results:
- The 'body throw' was adjusted for steps in different directions.
- The 'body throw' correlated with leading foot placement, independent of final CoM position.
- Body trajectories diverged only after the stepping foot made contact with the ground, not while airborne.
Conclusions:
- Results support the ballistic stepping model but indicate a limited predictive scope.
- The 'body throw' appears primarily concerned with leading foot placement, not final CoM.
- This suggests a one-step-at-a-time control strategy for safe locomotion.