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Adaptation of postural orientation to changes in surface inclination.
Joann Kluzik1, Robert J Peterka, Fay B Horak
1Neurological Sciences Institute, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006-3499, USA.
Experimental Brain Research
|October 14, 2006
Summary
The central nervous system adapts whole-body posture to maintain alignment with surfaces. This study shows that the lean after-effect, influenced by surface inclination, relies on global postural adjustments, not local muscle or joint control.
Area of Science:
- Human motor control
- Neuroscience
- Biomechanics
Background:
- Previous research demonstrated a postural lean after-effect following standing on inclined surfaces.
- This effect preserves body alignment relative to the support surface.
Purpose of the Study:
- Investigate how surface inclination amplitude impacts postural control variables.
- Determine if the lean after-effect mechanism regulates local (muscle, joint) or global (whole-body) postural variables.
Main Methods:
- Subjects stood on inclined surfaces with varying amplitudes (2.5-10 degrees).
- Measurements included muscle activity (EMG), joint positions, body segment orientation, center of mass (CoM), and center of pressure (CoP).
- A second experiment manipulated leg movement during the post-incline period.
Main Results:
- Increasing surface inclination linearly affected trunk and head orientation post-incline.
- Leg orientation, ankle position, EMG activity, and CoP location were not systematically affected by inclination amplitude.
- Restricting leg movement did not eliminate upper body leaning in the post-incline period.
Conclusions:
- The body-support surface relationship is a key reference for the central nervous system's (CNS) internal representation of posture.
- The CNS adaptively modifies this representation.
- The post-incline lean after-effect mechanism operates at the level of global, whole-body postural variables.
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