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Human standing posture control system depending on adopted strategies.
N Fujisawa1, T Masuda, Y Inaoka
1Graduate School of Science & Technology, Keio University, Yokohama, Japan.
Medical & Biological Engineering & Computing
|March 4, 2005
Summary
Human balance control uses ankle and hip strategies. This study found that when the hip strategy is dominant, the central nervous system may selectively enhance somatosensory feedback for better posture control.
Area of Science:
- Biomechanics
- Neuroscience
- Human Motor Control
Background:
- Human standing posture relies on distinct ankle and hip strategies to maintain balance in the sagittal plane.
- Understanding the sensory feedback contributions (vestibular, visual, somatosensory) to these strategies is crucial for elucidating postural control mechanisms.
Purpose of the Study:
- To quantify the influence of vestibular, visual, and somatosensory feedback on the ankle and hip strategies during human posture control.
- To investigate how the central nervous system modulates sensory feedback pathways under varying postural demands.
Main Methods:
- A two-linked rigid segment model represented human body dynamics, with a controller regulating ankle and hip joint moments.
- System identification techniques, specifically maximum-likelihood estimation, were used to determine controller transfer functions.
- Experiments involved healthy adults performing balance tasks on surfaces of varying width while subjected to external disturbances.
Main Results:
- Under narrow support conditions, favoring the hip strategy, the feedback pathway from leg inclination to ankle moment gain decreased by 16%.
- Conversely, other feedback pathways showed significant gain increases (20-140%), indicating selective neural modulation (ANOVA, p < 0.05).
Conclusions:
- The observed changes in feedback gains suggest a shift in sensory reliance during challenging postural tasks.
- A novel hypothesis proposes that the central nervous system prioritizes specific somatosensory feedback from the hip joint to ankle and hip moments when posture control becomes difficult.