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Stance dependence of automatic postural adjustments in humans
J M Macpherson1, F B Horak, D C Dunbar
1Neurological Sciences Institute, Good Samaritan Hospital, Portland, OR 97209.
Experimental Brain Research
|January 1, 1989
Summary
Human postural responses differ significantly between bipedal and quadrupedal stances. Quadrupedal stance reveals distinct lower limb muscle activation patterns and resembles feline postural control, suggesting cats as a model for human studies.
Area of Science:
- Biomechanics
- Neuroscience
- Human Movement Science
Background:
- Automatic postural responses are crucial for maintaining stability.
- The influence of stance configuration on these responses is not fully understood.
Purpose of the Study:
- To investigate how initial stance (bipedal vs. quadrupedal) affects automatic postural responses to support surface translations.
- To compare human quadrupedal postural control with that of cats.
Main Methods:
- Subjects adopted bipedal and quadrupedal stances on a translating platform.
- Measurements included ground forces, body segment kinematics, and electromyographic (EMG) activity.
- Analysis focused on spatial and temporal muscle activation patterns.
Main Results:
- Postural responses were biomechanically adapted to the initial stance.
- Muscle activation sequences differed significantly between bipedal (distal-to-proximal) and quadrupedal (proximal-to-distal) stances.
- Quadrupedal stance showed asymmetric limb use, with lower limbs acting as levers and exhibiting reciprocal antagonist activation, unlike upper limbs.
Conclusions:
- Stance configuration critically alters automatic postural control strategies.
- Human quadrupedal postural responses share similarities with cats, particularly in lower limb dominance.
- The standing cat serves as a relevant model for studying human postural control mechanisms.