2004 Fiscal Year Final Research Report Summary
Functional reorganizations and motor strategies for postural control during standing.
| Project/Area Number |
15500386
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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 | Keio University |
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Principal Investigator |
HASE Kimitaka Keio University, Department of Medicine, Assistant Professor, 医学部, 専任講師 (80198704)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAHASHI Nobushige Keio University, Department of Medicine, Instructor, 医学部, 助手 (60306818)
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| Project Period (FY) |
2003 – 2004
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| Keywords | postural control / voluntary movement / motion analysis / deafferentation / motor learning |
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| Research Abstract |
Sitting down and squatting are routine activities in daily living that lower the body mass by flexing the trunk and legs, but they obviously require different motor strategies for each goal posture. The former must transfer the supporting surface onto a seat, whereas the latter must maintain the center of mass within the same base of both feet. By comparing the performance of both maneuvers, the mechanisms involved in initiating the downward-oriented movements and the process of optimizing the performance during their repetitions were studied. The sitting-down movement was achieved by a stereotyped motor strategy characterized by a gastrocnemius muscle burst coupled with deactivation of the erector spinae muscle. The former produced a transient center of pressure(COP) displacement in the forward direction, and simultaneous unlocking of the trunk prevented falling backward. By contrast, because of the absence of any need to produce momentum in a given direction, a variety of motor strat
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egies were available to initiate squatting. During repetition of sitting down, the average COP position of the initial standing posture in the preparatory period was immediately shifted forward after the second trials, resulted in a decreased momentum in the backward direction while the subjects were transferring themselves onto the seat. In the squatting task, however, these changes could not be identified. These findings suggest that in the case of transferring the body-mass to another supporting base the central nervous system immediately adjusts the size of the initial throw to optimize the performance.
Then the motor strategies responsible for maintaining standing posture after deafferentation of the unilateral leg were studied. Specifically, we addressed the temporal changes in standing steadiness and reference position during prolonged standing until deafferentation would come on normal adult human subjects.
Ninn healthy subjects were asked to stand quietly on adjoining two force platforms with their knees extended. Two separate sessions consisted of prolonged standing over 20 min(control task) and until the H-reflex would be disappeared by the inflated pneumatic cuff above the right knee (experimental task). Bilateral hip and ankle joint positions and EMGs of bilateral gluteus maximus(GM), vastus mediali (VM), tibialis anterior(TA), and soleus (Sol) were recorded in the first period for 60 s and the following periods for the same duration every 3 min0. Body sway during quiet standing in each period was estimated on the basis of the COP measures derived from force plate data, i.e. mean velocity(MV) and root mean square distance (RMSD). Simultaneously, the average COP positions(center of body sway ; CBS) in each legs were calculated for determining the change of reference position.
In the control task, any time-related change during prolonged standing was not found in all of measured parameters. In the experimental task, although the MV in the anterior-posterior(A-P) and medial-lateral(M-L) directions were greater after deafferentation than in the previous periods, a significant difference in the RMSD was found only between the initial and final periods in the A-P direction(p<0.01). The results indicated that the unilateral loss of leg and foot sensory information necessitated additional regulatory activities to stabilize standing posture in the A-P and M-L direction, but the postural stability in the A-P direction could not be developed to the level in the initial period. After deafferentation, the right soleus activity was significantly decreased(P<0.01), so the mean velocities of COP in the anterior-posterior and medial-lateral directions were greater and the average COP position under the right foot shifted backwards compared to the ones in the previous periods(P<0.01). Also, the left tibialis anterior and soleus were activated as well as the bilateral gluteus medius.
The unilateral loss of leg and foot sensory information necessitated additional regulatory activities to stabilize the standing posture. The newly organized posture appeared to partly simulate the standing posture in the patients with sensory disturbance of a unilateral leg, such as amputees or hemiparetic patients. Less
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Research Products
(4 results)
