| Project/Area Number |
18500394
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Rehabilitation science/Welfare engineering
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| Research Institution | Hokkaido University |
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Principal Investigator |
FUKUSHIMA Junko Hokkaido University, School of Medicine., Professor (40208939)
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| Co-Investigator(Kenkyū-buntansha) |
ASAKA Tadayoshi Hokkaido University, Hokkaido University School of Medicine, Associate Professor (60241387)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,720,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥120,000)
Fiscal Year 2007: ¥520,000 (Direct Cost: ¥400,000、Indirect Cost: ¥120,000)
Fiscal Year 2006: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Keywords | Anticipatory Postural Adjustment (APA) / Eye-head movements / Muscle synergy / Center of Pressure (COP) / EMG / Muscle mode / Jacobian Matrix / UCM analysis / 足圧中心(COP) / 拮抗筋 |
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| Research Abstract |
#1. Postural control during eye-head movements.
We investigated postural sway in young subjects during eye-head movements. Subjects stood on the force plate wearing a helmet on which a laser spot was attached. Visual targets were presented stepwise at 60 deg. To right and left or 50 deg. To upward and downward of the straight-ahead position. Subjects were asked to look at the targets quickly by directing the laser spot to the target. The anterior-posterior component of centre of pressures (COPs) exhibited the largest changes and shortest latencies during downward movements.
Most of the subjects showed COP changes preceding the onset of downward head movements, and these changes were associated with EMG activity of biceps femoris and gastrocnemius. When subjects were asked to look at the target only by eyes, no consistent change was detected in ground reaction forces. These results indicate that the eye-head movements elicited the COP changes that preceded the onset of head movements. We
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assigned the same tasks to elderly subjects and compared the results. Even elderly subjects showed APAs preceding downward eye-head movements.
#2. Muscle Synergy
We used the framework of the uncontrolled manifold hypothesis to explore the effects of practice on the composition of muscle groups (M-modes) and multi-M mode synergies stabilizing the location of the center of pressure (COP). In particular, we tested a hypothesis that new sets of M-modes would form stronger synergies stabilizing COP location. Subjects practiced load release tasks for five days while standing on a board with a narrow support surface (unstable board). Their M-modes and indices of multi-M-mode synergies were computed during standing without instability and during standing on an unstable board before practice, in the middle-of practice, and at the end of practice. During standing without instability, subjects showed two consistent M-modes uniting dorsal and ventral muscles of the body respectively (reciprocal modes). While standing on an unstable board, prior to practice, subjects commonly showed M-modes uniting muscle pairs with opposing actions at major leg joints-co-contraction modes. Such sets of M-modes failed to stabilize the COP location in the anterior-posterior direction. Practice led to better task performance reflected in fewer incidences of lost balance. This was accompanied by a drop in the occurrence of co-contraction M-modes and the emergence of multi-mode synergies stabilizing the COP location. We conclude that the central nervous system uses flexible sets of elemental variables (modes) to ensure stable trajectories of important performance variables (such as COP location). Elderly subjects also showed both co-contraction and reciprocal patterns However, they showed more inter-subject variability than young adults. Less
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