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Postural fluctuations during pointing from a unilateral or bilateral stance
Ing-Shiou Hwang1, Chien-Ting Huang, Rong-Ju Cherng
1Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan. ishwang@mail.ncku.edu.tw
Human Movement Science
|February 7, 2006
Summary
Unilateral stance increases postural sway and alters limb coordination compared to bilateral stance. This suggests the body adjusts joint stiffness and attention to maintain balance during single-leg standing.
Area of Science:
- Biomechanics
- Human motor control
- Neuroscience
Background:
- Postural control is crucial for maintaining stability during upright stance.
- Active balance control involves continuous adjustments to prevent falls.
- The effects of different stances on coordination and fluctuations are not fully understood.
Purpose of the Study:
- To compare postural fluctuations and intralimb coordination between bilateral and unilateral stances during an active balance task.
- To investigate how the postural control system adapts to different stance conditions.
Main Methods:
- Fifteen participants performed a pointing task in bilateral and unilateral stances.
- Center of foot pressure (CoP) excursion was measured using a force plate.
- Limb movements were recorded using accelerometers.
Main Results:
- Unilateral stance led to wider CoP trajectories and increased postural fluctuations, particularly in the lower limbs.
- Limb-dependent fluctuations in unilateral stance showed increased upper limb coupling and decreased stance leg coupling.
- Unilateral stance resulted in greater regularity and spectral changes in trunk and lower limb fluctuations, indicating increased central oscillations (8-15 Hz).
Conclusions:
- Postural control system modulates joint stiffness in a stance-dependent manner.
- Unilateral stance likely shifts attentive control to the stance leg, increasing arm stiffness to reduce movement redundancy.