2005 Fiscal Year Final Research Report Summary
Exploring functional significance of phase synchronization between cardiac and locomotor rhythms
| Project/Area Number |
16500390
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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 |
Sports science
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| Research Institution | Yamagata University |
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Principal Investigator |
NIIZEKI Kyuichi Yamagata University, Faculty of Engineering, Professor, 工学部, 教授 (00228123)
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| Project Period (FY) |
2004 – 2005
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| Keywords | phase synchronization / cardiac rhythm / locomotor rhythm / functional significance / nonlinear oscillator |
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| Research Abstract |
It has been demonstrated that cardiac rhythm and locomotor rhythm are often led to oscillate in coincidence, thereby giving rise to synchronization. The synchronization of cardiac and locomotor rhythms has been suggested to enhance the efficiency of arterial delivery to active muscles during rhythmic exercise, but direct evidence showing such a functional role has not been provided. The present study was conducted to test this hypothesis. Rhythmic intramuscular pressure changes during locomotion were simulated using a computer-controlled, dynamic, thigh-cuff occlusion device. Alternating occlusions of bilateral thigh cuffs, administered at the frequency of the mean heart rate, produced significant phase synchronization between the cardiac and occlusion rhythms, provided that the occlusion pressure is comparable to the systolic pressure. During synchronization, heartbeats were most likely to occur in phases that did not include overlap between peak arterial flow velocity in the thigh and elevated cuff pressure.
Next, we compared the coupling phases that occurred during the simulation of intramuscular pressure changes and during walking on a treadmill. During walking experiment, subjects were required to walk while synchronizing their locomotion pace with their mean heart rate. The timing of the intramuscular pressure change was evaluated using the cuff wrapped around right thigh. Almost identical distributions of the phase histogram were found between walking and simulation experiments. The synchronized phases observed in both experiments are approximately consistent. These results suggest that cardiac-locomotor synchronization occurs so that the cardiac cycle is timed to deliver blood through the lower legs when the intramuscular pressure is not maximal.
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